Calcined Clays for Sustainable Concrete

Kaolinitic clays are among the most abundant source of highly reactive pozzolans and constitute a strategic mineral resource for the development of cements with high clinker replacement and reduced environmental impact. However, despite its abundance, suitable kaolinitic clay deposits are frequently uncharted or not properly identified, due partially to the absence of selection criteria and to the relatively high mineralogical complexity of kaolinitic clays. In this paper, the main findings in the accumulated experience of Cuba Technical Regional Center in the search and assessment of kaolinitic clay deposits are summarized. Through the study of selected samples from several kaolinitic clay deposits of different geologic origins, the relationship between chemical and mineralogical composition, and potentialities as a source of highly reactive SCMs are established, and experience-based guidelines for the preliminary assessment of kaolinitic clay deposits as a source of SCMs are proposed.

Growth of the world’s population is projected to add 2.5 billion people to the urban population by 2050, with nearly 90% of the increase concentrating in Asia and Africa. This will result in an immense demand for urban concrete infrastructure, leading to more global anthropogenic carbon-dioxide emissions. The most promising strategy for Africa entails the partial substitution of Portland cement clinker with additions of kaolinite clay and limestone to make cement and concrete. Kaolinite content is an important indicator of clay suitability. Results obtained by X-ray fluorescence, X-ray diffraction and thermogravimetric analysis indicate the potential of clay from two South African sources for clinker replacement in cement and concrete, showing that one source is very suitable, while the other is not.

The potential for calcined clay, and in particular Limestone Calcined Clay Cement (LC3), to be used in concrete in Kenya was examined in this study. Locations of clay sources and existing mining infrastructure were examined for potential development. Potential sources of clay were obtained and characterized for kaolinite content and reactivity. Results showed that there is significant potential for development and use of calcined clays in Kenya. Product development issues going forward in Kenya is also discussed.

The Southeast USA contains very large reserves of clay that could be used for supplementary cementitious material (SCM) production. A feasibility study has been performed recently to determine the viability of this clay for use as an SCM. Samples were taken from currently operating mines in Florida and analyzed for clay content, particle size, reactivity, and strength development potential. This paper discusses results with a focus on clay quality, material processing needs for use, and availability.

This study gives an overview over the geological and spatial distribution of German clay deposits visualized in a GIS map, which is based on the map of mineral resources and the geological map of Germany, and supplemented by active clay pits. The clays are classified regarding their geological context. Representative clays for a certain geological formation are examined closely. Detailed clay mineralogy is determined using XRD. Optimal calcination temperature is defined using TG/DTG. The calcined clays are characterized by XRD and BET. Pozzolanic reactivity is assessed by R3 calorimetry test and solubility of Al and Si ions in alkaline solution. A correlation between geological origin, chemical–mineralogical composition and pozzolanic reactivity is discussed. The study shows that a rough estimation of pozzolanic reactivity based on geological data or chemical composition is possible. For a detailed assessment, an elaborate determination of mineralogical phase content or a direct determination of reactivity is necessary.

Three clay deposits from northeastern Cuba were characterized by X-ray fluorescence, X-ray diffraction, and thermogravimetric analysis. The clay deposits present high content of aluminum oxide and loss on ignition. Kaolinite was identified as a main clay mineral, and iron and aluminum phases as impurities. The clays were preliminarily selected by chemical and mineralogical criteria and then activated by stationary calcination at 750 °C. The pozzolanic reactivity was determined by strength activity index in standardized mortars. Three blended cements containing calcined clay, limestone, clinker, and gypsum were formulated and assessed. Formulated cements were used to produce hollow blocks of concrete and hydraulic tiles. Finally, it is concluded that the three clayey deposits are presented with high potential for use as source of supplementary cementitious materials. Chemical criteria and kaolinite content are a useful tool to predict the potential of clay deposits to be used as source of supplementary cementitious materials. Samples with higher kaolinite content present the best pozzolanic activity. Ternary cements assessed can replace Portland cement in the manufacture of hollow concrete blocks and hydraulic tiles.

Marine clay is a low-grade kaolinsite clay commonly occurring in the coastal areas globally. Produced during excavation works, they are characterized by high silt and low kaolinite content, and hence, have little value for industrial applications. Since, the legislation in Singapore does not allow for disposal of these waste clays in the landfill, coupled with the acute shortage of space, marine clay poses a nuisance for handling and environmental issues. This project investigates the valorization of marine clay as a cement replacing agent and studies its pozzolanic potential. The clay after calcination at 600, 700 and 800 ℃ was used to replace ordinary Portland cement. Thermo-gravimetric analyses and isothermal calorimetry results indicate the potential of pozzolanic reactions with the consumption of calcium hydroxide and release of additional heat, respectively. Comparable strength was obtained at 28 days even at 30% by wt cement replacement. Furthermore, the 28-days compressive strength was not substantially affected with the calcination temperatures.

Tourism is a very important contributor to Goa’s GDP. In 2017, 6.9 million domestic tourists and 0.89 million foreign tourists visited Goa. This leads to a need for refurbishment of hotel rooms which is a significant contributor to the C&D waste generation in Goa. Around one ton of waste is on average generated per rehabilitated hotel room. The contents of tiles and bathroom fittings are around 20–25%. In this study, two different ceramic samples (wall tiles and sanitary ware) have been collected from C&D waste dumping sites in Goa. In addition, broken Mangalore roof tiles have been collected as a third ceramic waste. These three ceramics are made from clayey raw materials, most likely kaolin. The samples were split, size reduced and pulverized for the different analyses. In the preliminary study, all samples were analysed for the composition by XRF/XRD, characterized in terms of particle size distribution and tested for pozzolanic reactivity using the R3 test. The reaction products from the R3 test were investigated by XRD and DTA/TG.

Suitability of calcined kaolinitic filter cake arising from the production of high-quality silica sand as SCM was tested. The investigation comprises two different grades of materials. The first one represents a cross section from one week of sand production. The other sample has been subsequently prepared by sedimentation on a laboratory scale in order to investigate the impact of lower sand content. Chemical and mineralogical compositions of both samples were determined by means of ICP-OES, XRD and FTIR. The laboratory sample yielded higher kaolinite and a lower quartz content in comparison with the industrial product. The dehydroxylation behavior was determined using TG/DTG. After thermal activation, the reactivity was investigated by measuring the solubility of Al- and Si-ions in alkaline solution. It turned out that a calcination temperature of at least 650 °C is required for a complete dehydroxylation. Heat of hydration was studied by isothermal calorimetry using a substitution of 20 wt% of cement by the calcined product. The same substitution was chosen for the determination of strength activity index on mortar bars. Both materials provided a significant acceleration of the early hydration by promoting the aluminate reaction. After 28 days, the higher kaolinite content of the laboratory sample leads to a higher activity index of 121% in comparison with 102% of the industrial product.

Two brick clays (rich in 2:1 clay minerals) and a low-grade kaolinitic clay were studied regarding their transformations during calcination and their performance in blended cement mortars. The mortars with calcined clays exhibited decreased workability (slump flow), but this effect could be mitigated by employment of a conventional superplasticizer; however, compressive strength of the hardened mortar was lowered in some cases. While the kaolinitic clay generally yielded the highest strength, the performance of a brick clay could be increased by grinding to higher fineness and by mixing it with the kaolinitic clay.

Partial replacement of cement with crushed burnt clay brick waste powder (CBP) could reduce CO2 emission, enhance the conservation of natural resources, and decrease the cost of waste disposal sites. The aim of this study is to investigate the use of CBP as a partial replacement for cement in the production of cement mortar. Clinker was replaced by CBP in different proportions (0, 5, 10, 15, and 20%) by weight for cement. The physicochemical properties of cement at the anhydrous state and the hydrated state thus compressive strengths after 7, 28, and 90 days for the mortar were studied. Thermogravimetry analysis (TGA), Differential thermal analysis (DTA) and Thermogravimetry (TG) tests were conducted to investigate the development of cement hydration reactions in the presence of these wastes. Particle size distributions were obtained from laser granulometry (LG) of CBP and cement used in this study. Considering the proportions levels studied, the results indicated that the use of CBP in mixture accelerated the hydration reactions, and there was an indication of pozzolanic activity, particles packing density and compressive strength were maintained. Compressive strength decreased as the replacement level and average particle size increased. The CBP mixture at 20% level had similar or even higher mechanical properties than controlled mortar.

This paper reviews the feasibility of using low grade clay for developing geopolymer mortar by partially replacing conventional source material. The study intends to develop a framework for identification, classification and utilization of various clays and suggest suitable processing techniques to qualify for geopolymerization. The influence of source clay based on the reactivity of silica, physical, chemical and mineralogical characteristics on the properties of geopolymer mortar is extensively studied based on existing literature. Characteristics of clay after various treatment methods (calcining and lime treatment) are also reviewed so as to identify the extent of its effectiveness on geopolymers. Characteristics based on micro-structural studies such as energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) along with geotechnical characterization are reviewed. The paper highlights the significant characteristics of clay that is significant for geopolymerization and its implication on the properties of geopolymer mortar. The manifestation of geopolymer characteristics and its relation to crystallography and microstructure is explored to develop strategies for the qualification of clays. The influence of parameters such as alkali concentration and sodium silicate to sodium hydroxide ratio on compressive strength is presented. Based on the review, an attempt has been made to characterize different types of clay obtained from few sources in India, and a study has been conducted to assess the qualification technique proposed.

Previous studies revel that calcined illitic clay acts as potentially supplementary cementitious materials in Portland cement. Packing and workability are improved; the hydration products are like that corresponding to Portland cement and it also produces a pore size refinement improving the mechanical performance at later ages. The illitic clays have a high activation temperature and its pozzolanic activity is slow; however, it is the most abundant type of clay in several regions of the world, and therefore, their used as supplementary cementitious materials must be improved. Therefore, compression resistance values denote the effect of dilution at early ages. On the other hand, materials containing silica and alumina can be activated in an alkaline form, which would help to compensate the dilution generated by the addition. In this work, the alkaline activation of cement mixtures with calcined illitic clays is presented. As an alkaline activator, finely ground discarded glass is used. The finely ground glass, due to its amorphous nature, reacts quickly contributing to early hydration, while providing the alkalis necessary for an alkaline activation. In this paper, the blended cements with 30% of calcined illitic clays were analyzed and the effect of different percentages of replace by glass powder wastes was studied.

Clinker substitution by a combining multiple supplementary cementitious materials has been established as the most promising solution for combating the greenhouse gas emissions from the cement industry. Limestone calcined clay cement is a ternary cement in which clinker is partially replaced using calcined clay and limestone. This paper discusses the importance of using low-grade kaolinite clay for producing limestone calcined clay cements. While it appears that higher grade clay would be more beneficial at higher substitution levels, it is seen that the availability of portlandite becomes the limiting factor in LC3 cements having low clinker factors. Additionally, the reduction in the long-term clinker hydration, which has been reported in LC3 systems, is not observed in the presence of low-grade kaolinite clay.

The pozzolanic reactivity of four calcined natural clays (two being rich in illite and two being rich in smectite) was investigated by means of 28 days compressive strength of mortars and calcium hydroxide (CH) consumption in pastes of calcined clay and CH. The materials were characterized by XRD, XRF, BET, SEM and TG/DTG. Hydrated pastes of clay and CH were investigated by means of XRD, DTG and SEM. Besides clay minerals, two of the investigated raw clays contained 15 and 25% calcite, respectively. At optimum calcination temperature, calcined clays containing smectite and calcite, and illite and calcite in the raw clay had higher pozzolanic reactivity than clays containing smectite and illite alone. Results indicate that in clays containing high amounts of calcite, the formation of a glass phase upon calcination contributes to the pozzolanic reactivity.

Within three research projects, VDZ was able to show the performance of several calcined impure clays as supplementary cementitious materials (SCM). The used kaolinitic, illitic, and chloritic clays indicated low ceramic qualities and represented typical clays of cement plant quarries. Even suitable calcination conditions led to acceptable pozzolanic reactivity of the calcined clays. Illitic clay of low quality was mixed with few amounts of CaO added as limestone and calcined at different temperatures to investigate the influences of CaO addition on pozzolanic activation of the clay. The obtained samples were analyzed concerning their mineralogical composition and their amounts of reactive components. These activated calcined clays were used as SCM to mix laboratory cements with 20 and 40 mass % of calcined clay and were subjected to cement performance tests. The procedure may offer an opportunity to improve the quality of calcined clays for use as SCM produced with clays of lower quality. Currently, research is done to use, e.g., bypass dusts as clay activating calcium source to find another suitable valorization of by-products from the clinker production.

This study investigates the feasibility of using an oven and a balance to determine the kaolinite content in clay. The mass of 14 clays was recorded after three heating steps at 200 ℃, 400 ℃, and 600 ℃. The two upper temperatures permit to accurately consider the kaolinite dehydroxylation, whereas the step at 200 ℃ considers the moisture state of the clay. The protocol of the test was optimized with an adequate sample mass of 10 g and finer than 4 mm. The correlation with thermogravimetric analyses (TGA) results shows a very high correlation coefficient (R2 = 0.99). Since TGA is not available in all laboratories, this alternative method permits to characterize the clay without any expensive equipment.

This project explores the use of grinding aids to control the resulting particle-size distribution of calcined clay and limestone. It was observed that after grinding, calcined clays exhibit a strongly bimodal particle-size distribution, where the clay minerals concentrate mainly in the finer particle population. A significant increase in compressive strength at early age was observed in systems incorporating alkanolamines. The effect appears to be restricted to the aluminate reaction, as the silicate peak remains virtually unmodified. Particle classification (air separation) techniques were applied to remove the impurities (mainly quartz and iron oxides) and, therefore, increase the amount of kaolinite in the resulting material. An increase in the kaolinite content from 29 to 45% by mass was achieved in one step and without pre-dispersion of the particles.

The use of calcined clay fits well with the cement industry scenario where the goal is to produce sustainable and low CO2products. In addition, calcined clay draws special attention due to the high availability and improvement of mechanical strength of cement with addition of calcined clay. The trend toward clay calcination stresses the importance to find alternative processes that focus on efficiency and quality of the final product. Temperature, retention time and atmospheric conditions are process parameters which must be under control during the clay calcination, and those will be responsible for the quality and color of the final materials. FLSmidth investigations using two different processes—(1) soak calcination by rotary kiln and (2) flash calcination by gas suspension calciner—show that the flash calcination process gives a uniform heating with a better control of temperature and residence time of clay, which has an impact on the final quality of the clay product. FLSmidth has developed and patented a process which enables to obtain grayish color clays and to recover heat from the finished product more efficiently than traditional kiln process design.

The use of calcined clays as a substitute for clinker in the cement manufacturing is of great interest among the industries of cement and concrete due to many reasons, such as lower cost of production, lower CO2 emission rate and great availability of clay material. However, there are different kinds of clays available, regarding chemical and mineralogical composition. Processing clays with high iron content results in reddish or pinkish pozzolan, and cements with reddish and pinkish hues are misjudged as low-quality material. A color change technology to produce gray pozzolan from high iron content clays has been developed by Dynamis and proved in both laboratorial and industrial scales. This work presents the advance of this technology, proving that it can be applied to different kinds of clays and also that it can be implemented with the use of a flash dryer and a rotary kiln or considering only the kiln that can be a refurbished equipment. The technology also enables the production of pozzolan without the color change issue but also in an efficient and economically viable way. Using a combustion technology developed for clay activation, it is possible to control the calcination temperature and to obtain a controlled atmosphere, which is the key to the color change process. Industrial-scale tests proved that the technology is viable and versatile, regarding the types of processed clays.

A new large-scale suspension calcination process and key equipment suitable for dehydration and calcination of kaolin clay are introduced. The pretreatment process can be designed to meet various raw materials with different moisture contents, and the burning system has high heat transfer efficiency with a five-stage cyclone preheater, a suspension calciner and a fluidization cooling system. Moreover, the thermal process of materials in the production line can be accurately controlled as required necessarily; especially, the temperature of calciner can be controlled at a fluctuation of less than ±10 °C. Pilot production results show that suspension calcined clay has good activity and workability as a kind of supplementary cementing materials, indicating that suspension calcination technology has a good application prospect in the field of producing calcined clay for cement.

Associated with cement manufacturing processes, large amounts of carbon dioxide (CO2) are released into the atmosphere, and it is estimated that between 0.65 and 0.90 tons of CO2 are emitted per ton of cement manufactured. By 2050, the demand for this binder is expected to exceed 5000 million tons, which would contribute to an increase of more than 3% of emissions. However, the emissions can be reduced by using supplementary cementitious materials (SCMs); in this sense, calcined clays have a great potential for the reduction of emissions in the manufacture of cement. This has been studied in recent years with low carbon cement or LC3, developed by a joint team of the University of Lausanne and the Central University of Las Villas. The main results are the expansion of production by achieving clinker substitutions of up to 50%. In this sense, the Center for Research and Development of Technologies and Materials (CIDEM) in conjunction with the company IPIAC NERY has committed to the development of a small pilot plant that makes the manufacture of limited quantities of LC3, which allows the study of the process by interacting different sources of raw materials. In this paper, some calculations were for designing a pilot plant, taking into account the balance of mass and energy necessary for its proper functioning, which in turn allows to specify the technology for the scaling of the production in any new industrial plant or adaptation of capacities installed.

This study highlights the suitability of amphoteric (zwitterionic) polycarboxylate-based superplasticizers for a naturally occurring mixed-layer clay used as pozzolanic cement substitute after calcination. After a successful synthesis, dispersing performance tests reveal that amphoteric superplasticizers are a promising type of superplasticizer to address both calcined clays and cement. Tailor-made terpolymers can be applied to vary the initial slump by integration of different ratios of cationic monomer. Furthermore, heat flow calorimetry tests with amphoteric superplasticizers point out a less pronounced retardation in cement hydration compared to a standard anionic polymer. Zwitterionic superplasticizers are seen as potential alternatives for common anionic superplasticizers, especially for the advancing replacement of cement clinker with calcined clays of various mineralogical composition. Calcined mixed-layer clays are particularly promising as supplementary cementitious materials (SCMs) as they can be fluidized at low dosages of superplasticizers comparable to cement.

A major challenge of calcined clay cements is the flow properties. This research addresses binary and ternary CCIL (calcined clay blended with an ASTM C595 Type IL cement at the ready-mixed plant) and CCI/II systems and the effect of particle size and chemical admixtures on rheological characteristics. The effects of six different calcined clays and a superplasticizer and viscosity reducing admixture on the static and dynamic yield stress and viscosity of the blended paste were measured. While calcined clay systems alter the cementitious system flowability, modern chemical admixtures can custom-tailor the concrete rheological properties for robust placement and consolidation.

Calcined clays can be used in mortar and concrete as a part of a binder (LC3) or as a supplementary cementing material (SCM). The aim here is to substitute fly ash as an additive in concrete recipes. A stable mixture between two regionally available clays, burnt together with a certain ratio of 60:40 wt% at 650–680 °C, could be produced. Such metaclays produced in larger amounts were investigated in different mortar and concrete mixtures. The production indicates an important problem with the workability of the fresh concrete mixtures. That is why different superplasticizers were tested. It could be found that especially a mixture between a PCE-based material and a special additive developed for loam sands provides very good results. The workability increases from less than 200 mm slump on a value of about 300 mm. The combination of calcined clay materials and specially developed superplasticizer mixtures allows producing concrete with very different properties. It can be a closed system for the production of durable concrete structures.

Ensuring sustainability of printable concretes while complying with the complex requirements to their rheological properties in the fresh state is challenging yet absolutely essential. In this context, the limestone calcined clay cement (LC3) is of high relevance. In the study at hand, the structural build-up of LC3 paste was investigated by using the single batch testing approach. Two different calcined clays (CC), one from India and one from Germany, were studied, which were characterized by 58 and 66% amorphous phase, respectively. Both CCs enhanced the static yield stress of the cementitious materials, showing benefits of their use for digital concrete construction. However, the structural build-up of LC3 made with Indian CC was significantly more pronounced in comparison with that made of the German CC. Most likely, such quick and intense structural build-up can be attributed to the presence of kaolinite in the Indian CC which interacts with the high-range water-reducing admixture used in a particular way.

To escalate the structural efficiency of concrete is one of the best practices to achieve sustainability of concrete. Development of high strength lightweight aggregate self-compacting concrete has significant importance in this circumstance. Due to lower strength of the porous lightweight aggregate, it is very much necessary to improve the strength of the binder that is used in the concrete. Incorporation of metakaolin in the binder is one such practice to improve the strength of the binding material and to achieve these rheological properties of the concrete is very important. The present study evaluates the rheological and mechanical properties of high strength self-compacting lightweight aggregate concrete developed using metakaolin. SCCs were developed with binder content of 550 kg/m3 and water-binder ratio of 0.28, having metakaolin replacement percentages of 7.5, 10, 12.5 and 15%. Fresh properties of all the developed concretes using metakaolin were satisfying the SCC criteria. The compressive strength of the concretes increased due to the addition of metakaolin. At higher replacement level of metakaolin, it was also observed that the yield stress and plastic viscosity of the concrete increased. All these evidences justify that metakaolin is a potential material for the development of high strength lightweight self-compacting concrete which not only improves the rheological properties but also the mechanical properties of SCCs.

Calcined clay and fillers are materials with the best chance of scalability in cement industry. However, the addition of substantial amounts of SCMs affects the reactivity and water demand of blended cements, influencing their environmental impact in use as well as their performance. So, the aim of this work is to compare the influence of substituting clinker by calcined clay and limestone filler in the ecoefficiency of blended cements. For that, an ordinary Portland cement was replaced by calcined clay and limestone filler to produce two blended cements: LC3 and LFC. Regarding reactivity, LFC and LC3 presented higher relative combined water at 91 days compared to OPC. Water demand for constant workability was higher for LC3 compared to OPC and similar to LFC, but when superplasticizer was used, both cements demanded less water than OPC. Both parameters (reactivity and water demand) affected the binder’s efficiency measured as cwf index which had a linear correlation with mechanical performance. In concern of environmental indicators, binder and carbon intensity, LFC presented the lowest indicators results for concretes with 20 and 30 MPa, LC3 for concrete with 50 MPa and OPC for concrete with 60 MPa.

This study investigates the feasibility of using LC3 concrete, in comparison with more conventional cements. LC3 provides better performance than slag concrete. Similar properties to plain cement concrete are obtained. LC3 even permits to catch silica fume concrete in terms of durability properties.

The main goal of the paper is to compare the economic and environmental impacts of local production of low carbon cement based on a new mineral addition of calcined clay and limestone (LC2) versus industrial production of low carbon cement (LC3), considering particularities of Cuban context. First, a technical comparison is carried out comparing also with traditional OPC and PPC and considering standards applied in the island. Secondly, an economic assessment of production and investment costs is carried out using life cycle costing (LCC) technique. Afterwards, to assess environmental impacts a simplified life cycle assessment is performed to compare both cements, OPC and PPC. Cement based on LC2 reports economic advantages in comparison with the other cements: industrial LC3, OPC and PPC. Environmental results show a similar behaviour for local and industrial LC3 but a significant decrease of emissions and energy demand versus OPC and PPC. Technical comparison shows that local LC3 results are variable but complies with the standard for its use in mortars and non-structural applications. Finally, results show that LC3 introduction is a feasible option to reduce impacts of the cement industry in Cuba, and a combination of its local and industrial production is the best alternative to achieve sustainability goals in the short and mid-terms. Main opportunities of local LC3 are the reduction of costs, the easier storage, the use of local materials, amongst other. Main challenge is related to a correct use of the mineral addition in localities.

In this paper, a model is presented, which can predict propagation time due to carbonation-induced corrosion. This model is developed using existing models in the literature. Corrosion rate determination is a crucial step in modeling the propagation phase. An assembled model of corrosion rate is presented, which takes into account w/c ratio, relative humidity, temperature, pH, and cement-type effects into it. Corrosion rate model also considers effects coming due to the accumulation of rust products so as these products keep piling, corrosion rate reduces with time. This corrosion rate model shows good agreement with the experimental data, which is available for different scenarios in the literature for the OPC. From this corrosion rate model, a propagation time model is being developed using Faraday’s law and critical mass for cracking model. The propagation time for the LC3-added cement concrete is calculated.

Life cycle assessment (LCA) has been conducted to obtain the potential reduction in the environmental impact due to the production of limestone calcined clay cement (LC3), with respect to ordinary portland cement (OPC) and fly ash-based portland pozzolana cement (PPC). A case study of a typical cement plant in South India is considered. It is found, for this particular case and the assumptions made, that the CO2 emissions and the energy demand could decrease by 34% and 18%, respectively, if LC3 is used instead of OPC, with the corresponding reductions being 26% and 21% for PPC. A parametric study of some key factors that could influence the impact of LC3 showed that the CO2 emissions and the energy demand could vary by 13% and 20%, respectively, with variations in the calcination energy requirement while the clay transportation distance did not have any significant influence.

Metakaolin can be considered as a model compound for an aluminosilicate-rich supplementary cementitious material (SCM) because of its composition and highly pozzolanic properties. This work presents a systematic investigation of the hydration of white Portland cement (wPc)–metakaolin (MK) blends cured at different temperatures by 29Si and 27Al MAS NMR with the main focus on the structure and composition of the C-(A)-S-H phase. White Portland cement–MK paste samples with wPc replacement levels of 0, 10, 20, and 30 wt% have been prepared and hydrated for 1–8 weeks at five different temperatures (5, 20, 40, 60, and 80 °C). Information on the degree of reaction for alite, belite, and MK is derived from the 29Si NMR spectra and shows that the hydration of the wPc–MK blends is accelerated with increasing temperature except for the blend with the highest MK level (30 wt%). The AlIV/Si ratio of the C-(A)-S-H phase is found to be independent on the hydration time but increases slightly with curing temperature. On the other hand, a significant increase in the average aluminosilicate chain lengths is observed for blends with increasing temperature, reflecting a decrease in the Ca/Si ratio for the C-(A)-S-H phase. Strätlingite is present in the wPc–MK blends at 20 °C and the fraction of this phase decreases with increasing curing temperature.

The use of supplementary cementitious materials (SCMs) as partial clinker substitute permits to reduce the environmental impact of cement production. Calcined clay is one of the most attractive SCMs because it is widely available. Its combination with limestone in limestone calcined clay cement (LC3) benefits from the synergy effect between metakaolin and calcite. This study investigates the effect of curing temperature between 20 °C and 30 °C on the properties of LC3. Increasing temperature promotes the hydration of clinker and the pozzolanic reaction resulting in a boost of strength development of LC3 at early ages. A coarser threshold pore diameter is observed on the samples cured at 30 °C for 28 days but it does not affect the strength of LC3.

An experimental work was conducted for studying the influence of early age curing temperature on the performance of low clinker blends. Three low clinker blends, limestone calcined clay cement (LC3), Portland pozzolanic cement (PPC) using fly ash, and Portland slag cement (PSC) were used in this study. The clinker replacement level was kept at 50% by weight for all the blends. In addition to the isothermal curing conditions at 27 and 50 °C till 28 days, samples were also exposed to two different temperature regimes by changing the specimens from 27 to 50 °C at the age of 1 day and 3 days. Mortar compressive strength and X-ray diffraction were carried out at the age of 28 days. Strength and degree of hydration of clinker phases were compared. The later age performance of low clinker blends observed to be detrimental at a higher temperature (50 °C). It is observed that reduction in performance is relatively higher in LC3 as compared to PSC and PPC. However, when the time of temperature exposure delayed by 24 h, the adverse effect of temperature on LC3 was disappeared, and the blend has shown better performance than the other two blends.

It has been well established by several studies that LC3 requires an additional amount of gypsum on top of the normal dosage contained in OPC. In this manner, the second (aluminate) peak does not overlap with the first (silicate) peak. This required adjustment of the system sulfate content is attributed to the additional aluminate phases introduced to the system by the addition of calcined clay. However, a correlation between metakaolin (aluminosilicate) addition and the amount of additional gypsum has not been found, and the relationship between these parameters and the position of the aluminate peak is not clear. This study explored in depth this issue in order to further understand the driving mechanism controlling the sulfate demand in LC3. Our results show that there is no direct link between the aluminate phase content and the gypsum demand. On the contrary, the driving mechanism is linked to the specific surface area that the mineral additions (calcined clay and limestone) introduce to the system.

The present study tries to understand the effect of sulphates on the hydration of Portland cement—calcined clay systems. Calcined clay was obtained by calcining a clay having 95% kaolinite at temperatures ranging from 700 to 800 °C. The calcined clay was used to replace 30% of clinker. A clinker with low aluminate and low alkali content was used. Laboratory grade gypsum was used as the source of sulphates. In this study, the sulphate content in the cement system was varied as 2.5 and 5.0%. Mainly, the effect of sulphates on the hydration of cement was studied by conducting isothermal calorimetry on cement pastes for 48 h. In addition, the phase assemblage studies were done at 1 day and 3 days by performing X-ray diffraction on the paste samples. It was observed from calorimetry that the blends with higher sulphate content show a significant delay in aluminate hydration. It was again noticed that the main hydration peak was also affected with increase in sulphates. In calcined clay blend, the amount of ettringite formed was lesser than the normal OPC blend at similar sulphate content. In the other case where the dosage of sulphate was high, the ettringite continues to form till 3 days.

Limestone cements (IL) are becoming commonly available for structural applications. Calcined clays have great effect on performance enhancement of IL systems. Blending of those systems typically occurs in cement plants; however, for markets where blending occurs in concrete ready-mixed facilities, optimization of sulfate content is critical for the successful use of this new ternary blend. Optimum sulfate content for calcined-clay-limestone-cement systems was assessed using isothermal calorimetry, with hemihydrate as a sulfate source. The optimums are determined at 1, 2 and 3 days of hydration using both IL and ordinary portland cement (OPC) with two clay sources. Maximum heat of hydration was found to vary with age as well as the blended material sources. Less sulfate is required to optimize the limestone blended cement system. The replacement level of clay and the sulfate demand in the blended system are also examined. At the same replacement level, the optimum SO3/Al2O3 ratio is similar, irrespective of cement type or clay type.

This study explores the effect of kaolinite content from 20 to 95% on porosity refinement and mechanical properties of LC3-50 and LC3-65 (50% and 65% clinker factor, respectively) systems by dilution of pure metakaolin. The effect of metakaolin dilution was coupled with other factors that were observed to have a significant impact on hydration kinetics and strength. The effect of limestone particle size was studied in terms of packing optimization and workability enhancement. A detailed comparison between LC3-50 and LC3-65, currently allowed in the European standard, is provided showing that the main difference in mechanical properties occurs at 1 d for an equivalent kaolinite content. Finally, guidelines for effective and optimized utilization of clays of different grades (kaolinite contents) in LC3 systems are given.

The objective of the study was to evaluate the effect fineness of grind of metakaolin (MK) on age strength development of metakaolin/cement blend pastes. Five batches of metakaolin designated MK1, MK2, MK3, MK4 and MK5 were investigated. The metakaolins were each ground to three different fineness—95% passing 75 µm, 95% passing 53 µm and 95% passing 45 µm. Cement pastes containing 0 and 30% of MK were prepared at a constant water/binder ratio of 0.3. The compressive strengths of the cement pastes were determined at 2, 7, 14 and 28 days. The results indicated that the compressive strengths of the cement pastes with MK were not significantly affected by the fineness of grind of the MK between 75 and 45 µm particle sizes. The results showed that the highest compressive strengths were achieved with cement pastes that contained MK3 and MK5 which had the highest metakaolinite contents. MK1 which had the lowest metakaolinite content but the highest mullite and cristobalite contents exhibited the lowest compressive strength at all ages. Based on this study, it was concluded that the coarser MK can be utilized for partial replacement of OPC reducing grinding costs and ultimately market prize of the MK/cement blends.

There is a wide scope for use of calcined clays in cement as kaolinitic clays are available in huge quantities around the world. Similarly, fly ashes are also available in substantial quantities, though the quality of fly ash is still a major concern. One is used in large quantities, and the other has the potential and the resources to be utilized. The difference in their physical and chemical properties and their behavior in alkaline medium are studied in this work. One class F fly ash and one calcined clay with 60% kaolinite are selected for this study. The materials are characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to find chemical composition, mineral composition and morphology. The difference in their solubility behavior in alkaline medium was determined using ICP-MS to find the dissolution of silica, alumina and calcium ions in NaOH solution at 20 °C. Though the hydration behavior of calcined clays and fly ash in cement systems are very distinct, their solubility behavior was found to be similar. Calcined clays exhibited higher dissolution of Si and Al ions in the solution compared to fly ash. The effect of dissolution of Si and Al on the compressive strength of mortars is also studied. Strength activity index of mortars increases quickly starting from day 1 for calcined clay and reaches a maximum at 7 days, while for fly ash it increases steadily and reaches a maximum at 28 days.

This study explored the effect of calcite (calcium carbonate) and gibbsite (aluminum hydroxide) impurities on the reactivity of a model calcined clay. Pure metakaolin was combined with calcite and gibbsite to prepare model raw clays, which were then calcined in a furnace at 800 °C for 1 h. The R3 test was used to assess reactivity of the calcined materials, and physical and mineralogical characterizations were performed. It was observed that calcite forms a layer of granular deposit over kaolinite particles, reducing its specific surface area. However, the impact on reactivity is relatively minor if the effect of dilution is accounted. In the case of gibbsite, it completely dehydrates upon calcination and transforms into inactive crystalline alumina. The effect of its presence was compared to quartz, and no significant differences were found. Thus, natural clays with calcite and gibbsite impurities are suitable for LC3 applications.

Demonstrate the feasibility of an illitic clay-based geopolymer is the purpose of this study. If the thermal activation of standard precursors such as kaolin is a well-known process, the reactivity of illitic precursors required the combination of thermal and mechanochemical activation. The structural changes of the precursor material submitted to various grinding durations were followed by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) and the amorphous phase rate calculated from XRD analyses were correlated with this parameter as well as the compressive strength (Rc) of the manufactured geopolymers. Mechanical properties increased with the grinding time and the decrease of L/S ratio of the geopolymer paste. Illitic clay-based geopolymers may reach high performance as demonstrated with a Rc at 28 days reaching 102 MPa. Finally, the relations between the amorphization rate and the compressive strength of the geopolymers have been highlighted.

This contribution reports on some preliminary studies on the use of lateritic soils from Cameroon as raw materials for the production of alkali-activated binders. These soils contain about 40–60% kaolinite and variable amounts of quartz, hematite, and other minor phases. After calcination at 800 °C, this material is blended with up to 30% waste marble powder, which is produced in large amounts during quarrying, cutting, and processing of marble. The results of our tests show that a careful mix design allows a good mechanical performance to be achieved, with the values of the cubic compressive strength larger than 30 MPa after 28 days. The role of Fe on the performance of this material is investigated by comparison with Fe-free blends of commercial metakaolin, waste marble powder, and quartz. Calorimetric data suggest that the use of alkanolamines as Fe chelating agents may accelerate the early-age reactivity, depending on dosage, although the effect on the development of mechanical properties is minor. It is argued that alkali-activated calcined laterite represents a viable option for the development of sustainable binders, especially for the African market, where it could be used, for example, to produce compressed stabilized earth blocks, in substitution of masonry units based on Portland cement or fired clay bricks. The use of waste marble powder adds further environmental value to this material.

Gangue, a typical waste associated with the coal mining process in northern China, was characterized before and after thermal treatment by XRF, XRD, TGA-DSC, and SEM. The pozzolanic reactivity of calcined gangue with different calcined temperature was tested by standard mortar strength and R3 calorimetry test. The performance of blended cement was evaluated by mortar strength and flow. The XRD and TGA-DSC analyses showed that the main minerals that present in the raw gangue were kaolinite, and a small amount of carbon-based compounds and metakaolin were almost the only phase in calcined gangue. After thermal treatment and depending on the temperature, it showed very high reactivity especially combined with limestone. The strength property of limestone calcined gangue cement with 45% replacement of clinker was higher than reference cement (CEM I 42.5 N) on 7 and 28 days. Furthermore, it is found that the calcined gangue has less influence on the workability of LC3 according to particle morphology compared with a typical calcined clay, based on the results of SEM observation.

The low early age strength gain of fly ash-based Portland pozzolana cement (PPC) poses a challenge in many applications. This study tries to improve the early age strength gain of fly ash-based PPC by blending it with limestone calcined clay pozzolan (LC2). Ordinary Portland cement was blended with a typical low calcium fly ash (FA) at replacement levels of 30 and 40% termed as PPC-30% and PPC-40%, respectively. To enhance the mechanical performance of PPC-30% and PPC-40%, the fly ash was blended with LC2 in 1:1 mix proportion. Hydration and strength gain were evaluated using isothermal calorimetry and strength activity tests. Heat evolution results show that the addition of LC2 pozzolana has increased the early age hydration of the blended pastes. Strength activity index of mortar showed improvement in early age performance in both the mixes compared to PPC. Moreover, 30% replacement by LC2 is found to be more beneficial and can achieve strengths comparable to that of OPC.

The density of C-A-S-H was investigated by 1H-nuclear magnetic resonance (NMR) on white plain cement and LC3. Despite the high variations in binder composition, the density of the C-A-S-H is found similar between all the systems, also being independent of the calcined kaolinite content of calcined clay in LC3.

This paper investigates the microstructural development of limestone calcined clay cements (LC3) using microstructural modelling. The microstructure of ternary blended cements containing 15, 30 and 45% limestone and calcined clay is simulated using microstructural modelling platform μic. It is found that replacing cement with limestone and calcined clay significantly increases the porosity of pastes. The increase in the porosity is observed to depend on the percentage replacement of cement with limestone and calcined clay. It is also observed that just the addition of fine limestone and calcined clays is not sufficient to explain the reduction in experimentally observed threshold pore diameter in pastes containing limestone and calcined clay. The results suggest that it is important to consider the modification in the hydration product (CASH) in order to explain the reduced threshold pore diameter of LC3 systems.

Hydration of triclinic tricalcium silicate (C3S) blended with three different natural clays was investigated in this work. Pure C3S, C3S blended with metakaolin and fine quartz was used as references. Blends were made with 1:2 ratio of calcined clay/quartz and C3S. A water-to-solid ratio of 2/3 was used. The samples were cured at 20 °C for 7 days of hydration. The total heat release was measured using isothermal calorimetry, and the degree of hydration of C3S was determined using XRD/Rietveld analysis and portlandite content using TGA analyzed by tangent method. The results show that there is a higher heat release with higher kaolinitic content. The degree of hydration of C3S in blends with calcined clay was found to be lower after 7 days of hydration compared to the reference systems.

The tensile strength of limestone calcined clays (LC3) and Ordinary Portland Cement (OPC) pastes was determined by a point load test (PLT). Testing was carried out on reduced size cubic specimens (10 × 10 × 10 mm), and the results were analysed using the Weibull probabilistic distribution. Mercury intrusion porosimetry (MIP) was also carried out to complement the investigation. Results showed that, despite being slightly more porous, LC3 has higher tensile strength than OPC due to the pore refinement caused by pozzolanic reactions. The data variability was three times lower for LC3 in comparison to OPC, which may be related to the slightly higher fracture energy of the LC3 samples.

Alternative and supplementary cementitious materials originate from different sources in nature and also from industrial productions. These materials came into focus again as their use can contribute substantially in the reduction of CO2 during the manufacturing of cementitious materials. Also, the aspect of reducing the industrial residues by recycling is of substantial importance. As the addition of supplementary cementitious materials leads to different composite cements, it is highly necessary to determine the reaction behavior and their part during the hydration of the interground or interblended components. The different natural occuring materials from volcanic and sedimentary sources like clays and pozzolanic materials are available in high quantities and can be used. Due to their formation, the natural materials differ in their mineralogical and chemical composition and should be optimized for this application. Therefore, clays are often thermally treated to be activated, whereas other products are used without treatment with their original composition. Natural and industrial pozzolans also contain high amounts of amorphous phases which should be determined as they are partially reactive. As these materials do not contain typical cement minerals as calcium silicates and calcium aluminates, their reaction behavior is often caused by their amorphous contents. Other basic sources of mineral additions are coming of artificial sources and are mainly based on industrial residues coming from the processing of ores and include slags ore coming from energy production like fly ashes and bottom ashes. As these materials showing different compositions, their chemical and mineralogical phase relations must be determined also. Some of these supplementary cement additions are known for long times, and like latent hydraulic slags, others must be investigated and characterized newly. As these components vary in their reaction behavior, it is highly likely that their mineralogical quantification relates to their various properties and can be determined by different methods: Rietveld method of these complex systems, including determination of amorphous contents Set up and application of a referenced file using Partial or not known crystal structure (PONKCS) method for further quantification Cluster analysis including the various 2–4 component systems and summarizing similar phase contents and properties Set up and determination of phases and contents by partial least squares refinement (PLSR) method. Different artificial mixtures based on various OPCs with different additions of pozzolans, metakaolinite, limestone, anhydrite, and the quantification of their crystalline and amorphous contents will be demonstrated.

The use of supplementary cementitious materials (SCMs); fly ash and granulated BF slag, by lowering clinker content in cement is a viable strategy to bring down CO2 emission during cement manufacture. Due to the large availability of clay and limestone all over the world, a new ternary cementitious cement system containing calcined clay and limestone could increase clinker substitution to about 50% without significantly influencing cement performance due to the synergy between aluminates from calcined clay and carbonates from limestone. In the present study, mechanical properties of different limestone calcined clay cement blends, prepared maintaining clinker substitution of 0.40, 0.45, 0.50, 0.55 and 0.60 was measured as per Indian standard IS:4031 and showed compressive strength comparable to the minimum strength requirements for blended cements as specified in Indian standard, in case of cement having clinker substitution rate of 0.50. Comparative evaluation of compressive strength of OPC and limestone calcined clay cement showed substantial increase in strength at later ages in case of limestone calcined clay cement as compared to OPC. The heat evolution of limestone calcined clay cement using isothermal calorimeter showed higher heat evolution with early attainment at all ages as compared to OPC. The limestone calcined clay cement showed its resistivity to different aggressive solutions such as seawater, sulfate and chloride solution salts along with lean water up to the period of 12 months.

In mass concrete construction, huge amount of cement is usually used and normally creates high temperature gradient across the thick section. Replacing suitable supplementary cementitious materials (SCMs) to ordinary Portland cement (OPC) is one of the potential strategies to reduce temperature rise of concrete. Although many benefits on the durability of concrete using limestone calcined clay cement (LC2 cement) have reported, very few studies have been published regarding the risk of thermal cracking when LC2 cement is used. Heat of hydration and thermal properties of LC2 cement are necessary parameters of the thermal cracking analysis and must be clarified before its application to the mass concrete construction. In this study, the calorimetric heat flow and cumulative heat of hydration are tested with isothermal calorimetry. The intensity of aluminum peak from calorimetric heat flow is the main hydration peak of LC2 cement pastes. The intensity of aluminum peak increases with higher LC2 cement replacement due to high Al2O3 content of LC2 cement. After the age of 12 h, the cumulative heat generation of LC2 cement pastes becomes lower than that of OPC pastes. Moreover, thermal properties which are specific heat (c), thermal conductivity (k) and coefficient of thermal expansion (CTE) of LC2 cement pastes are also investigated. The results showed that the specific heat of LC2 cement pastes decreases for 8% and 14% with 30% and 45% replacements, respectively, compared with OPC pastes. With higher LC2 cement replacement, the thermal conductivity decreases while the coefficient of thermal expansion increases. These changes are believed to be related to the pore structure development of LC2 cement pastes. Moreover, semi-adiabatic temperature rise is tested to observe the temperature rise. The peaks of temperature are 66.9 °C and 60.6 °C in the case of 30% and 45% LC2 concrete, respectively, which are lower than that of OPC concrete.

With the advent of the Industrial Revolution, science and technology grew rapidly with the producing era coming into view. The early industrial sectors engaged in small scale production of the major pollutant, smoke. Owing to the emergence of numerous factories and large scale jobs, the problems of industrial contaminating activities began to assume much importance. These issues made the burning up of industrial as well as agricultural waste products from industrial activities become the main focus of waste eradication study for environmental, economical, as well as technical reasons. Discarding of waste techniques became the problem emerging from constant industrial and technological development. Partial replacement of pozzolans by manufacturing waste product is not just efficient but an improvement to features of clean as well as cynical concrete. This is because it involves reducing the shrinkage, minimizing the cracks, as well as enhancing the sturdiness. Besides, the safe removal of waste substances serves as a means of shielding the surroundings from contamination. The main purpose of this research is to observe the ability and strength of the mortar by mixing the calcined clay in a mortar mix in the proportion of 0, 4, 8, 12, 16 and 20% and with this, the effect of mortar on HCl and acetic acid mixed in water in a proportional proportion has been studied.

This study aims to investigate the pozzolanic strength activity of three kinds of supplementary cementitious materials (SCMs)—a limestone-calcined clay from India and class F fly ashes from China as well as India. Using the ASTM C311 strength activity index test method, the effect of the different pozzolan replacement levels of cement (0, 20, 50 and 80%, by weight) was investigated. Compressive strength at 3, 7, 14, 28 and 90 days under standard curing was recorded. It was observed that the effectiveness of the pozzolan in mortars depends on particle size distribution, glassy or amorphous nature, surface area and replacement level. The results in this study provide insights into the mix design and applications of high-volume pozzolanic cementitious materials that promote solid waste recycling in construction industry.

The present study aims to explore the potential of using limestone calcined clay (LC2) blend as a supplementary cementitious material. The cement was replaced with LC2 blend (by volume), and experiments were carried out at the same solid volume concentration. Initially, the influence of LC2 particles on cement was assessed through wet packing density studies. Further, fresh properties were evaluated using rheological studies, setting time for all the experimental combinations. Also, the compressive and flexural strengths for different combinations were determined at various ages (up to 56 days). The results are discussed in the light of optimal and maximum replacement levels based on the performance of cementitious mortars in the fresh and hardened state.

Strain-hardening cementitious composites (SHCC) exhibiting tensile strain-hardening and multiple-cracking behaviors are attractive for many construction applications. Compared to conventional concrete, typical SHCC are cost-, energy- and carbon-intensive. Specifically, the cement content of typical SHCC mixtures can be as high as 600–1200 kg/m3. To reduce the material cost and improve the sustainability of SHCC, one possible approach is to replace cement with supplementary cementitious materials (SCM). It has been shown in the literature that the limestone calcined clay (LC2) system is a promising source of SCM for conventional concrete. This paper presents an attempt to use ultrahigh-volume LC2 (80% by weight of binder) to produce polyvinyl alcohol (PVA) fiber-reinforced SHCC with adequate compressive strength and excellent tensile performance. This version of sustainable SHCC is applicable for many practical applications, and the substitution of high percentages of cement with LC2 can reduce the environmental impact significantly.

High-tensile strength strain-hardening cementitious composites (HTS-SHCC) can reduce the size of structural members, enhance the flexibility of architectural design and make 3-D printed structures without steel reinforcements possible. To produce HTS-SHCC, high-performance polyethylene (PE) fiber is widely used, due to its high-tensile strength of about 3 GPa. However, PE fiber has a hydrophobic and smooth surface, which limits the fiber/matrix interfacial bond strength. Therefore, a large dosage of very fine powders (e.g., micro silica) has been generally included in the matrix to densify the fiber/matrix interface and ensure sufficient fiber-bridging capacity. Recently, it has been proved in the literature that limestone calcined clay (LC2) system has a strong porosity refinement effect in cementitious materials. Thus, LC2 has the potential to ensure sufficient fiber/matrix frictional bond strength by replacing a fraction of cement by LC2 in HTS-SHCC, which can also reduce the material cost and the environmental impact of the materials. This paper presents a feasibility study of incorporating different dosages of LC2 (0, 20, 40, 60 and 80% of binder) in HTS-SHCC, with the focus on the tensile performance in terms of tensile strength, ultimate tensile strain and crack pattern. The findings in this study provide a new, low-cost and sustainable approach to produce HTS-SHCC.

This study investigates the creep properties of limestone calcined clay cement. A series of paste samples using limestone and calcined clays as replacement materials were tested under basic compressive creep. The ternary mixes showed lower creep compliance than the plain cement references, even when using low reactivity clays or lower replacement fraction. A finite element model was used to back-calculate the visco-elastic properties of the C-S-H matrix and C-S-H gel. Whereas the elastic properties of C-S-H were found to be similar between LC3 and plain cement, the viscous behaviour of C-S-H gel appeared to be noticeably different for LC3.

In this paper, the utilization of waste marble powder for the production of limestone calcined clay cement is investigated. Limestone calcined clay cement is an advanced ternary blended cement made by using the combination of low grade calcined clay, limestone and gypsum. It can be replaced by 50% of clinker which is beneficial for the reduction of carbon dioxide (CO2) emission at the time of production of cement. In the existing paper, the physical and chemical characteristics, chemical analyses carried out by X-ray fluorescence, lime reactivity test for pozzolanic behaviours, mechanical properties of LC3 using marble powder, i.e. compressive strength and spilt tensile strength are checked and compared to the Portland pozzolana cement (PPC) and ordinary Portland cement (OPC).

This paper presents the beneficial role of silica nanoparticles (SNPs) in high volume fly ash (HVFA) cementitious system. The dosages of fly ash (FA) replaced with cement in the present study were 40% (40 FA) and 50% (50 FA). The dosages of SNPs were first optimized in mortar, and the optimized dosages were used in the concrete study. The fresh stage properties of mortar show that delay in setting time in HVFA system can address using SNPs as the initial final setting time gets shorten in the presence of SNPs. In addition to this, mechanical strength improves significantly especially at an early age of hydration. Compressive strength of the concrete containing 3% SNPs resulted in the speedy construction because we can achieve maximum compressive strength in 7 days in spite of 28 days, which is around four times faster. Long-term carbonation results revealed that SNPs incorporated mixes show a reduction of carbonation depth up to 45% with respect to control specimens containing 40 FA, while with 50 FA mix, the reduction was ~38%. Similarly, SNPs incorporated specimens show significant resistance towards the sulphate attack of about 41% with 40 FA and 34% with 50 FA samples and as compared to control specimens. Therefore, the incorporation of SNPs in concrete leads to the improvement of its durability and service life.

Recently developed limestone calcined clay cement (LC3) with low clinker factor is growing rapidly in the construction industry because of its several benefits over ordinary Portland cement (OPC) and Portland pozzolana cement (PPC). In this paper, monitoring strength development of cement substituted by (LC3) using different piezo configurations was studied. The experimental study was carried out on concrete cube specimens of OPC and LC3, in which different piezo configurations such as embedded piezo sensor (EPS), surface-bonded piezo sensor (SBPS), jacketed piezo sensor (JPS) and non-bonded piezo sensor (NBPS) are installed to the specimen to acquire data in the form of conductance and susceptance signatures via electro-mechanical impedance (EMI) technique. The sensitivity of the different piezo configurations was calibrated with the compressive strength, based on the results, it can be concluded that the compressive strength of OPC and LC3 is comparable to each other. All the piezo configurations were effective in monitoring the compressive strength; however, the embedded sensors, EPS and JPS, perform the best in LC3 and OPC, respectively.

To investigate the mechanical properties of the localized LC3 concrete and interfacial bond behavior between LC3 concrete and steel rebar, different design mixtures of LC3 concrete and normal concrete were prepared. The compressive strength in different curing ages was evaluated experimentally compared with that of normal concrete with the same W/B ratio. The interfacial bond strength was evaluated by pullout test on the steel rebar from the concrete block. The test results show that rebar–LC3 concrete has comparable good bond strength and has higher secant stiffness in bond-slip curve than that of rebar–normal concrete.

This paper aims to study the possibility of using piezoelectric-based patches to characterize the hydration of cement-based mortar mix blended with calcined clay (CC). An embedded piezoelectric-based sensor is used for monitoring for the early age as well as long-term hydration of binder paste. Progressive changes in hydration of mortar were studied in terms of admittance signatures recorded over a period of 28 days. This study examines the behavior of cement mortar with CC as partial replacement of cement at various substitution levels of 4–12%. 70.6 mm mortar cubes of 1:3 (cement:sand) were cast for the study. Setting time, compressive strength and hydration of cement-based mortar mix were studied on formulated binder paste. The experimental results with 6% replacement of cement showed maximum compressive strength as compared to other mixes, and similar trend of results has been noted by electromechanical impedance (EMI) technique. Delay in setting time and approximately linearly decrease in flow value have been observed with rising the percentage of CC replacement as cement in cast mortar mixes. To study the hydration of cement mortar mixes, signatures were recorded from 0 to 28 days on the prepared cubes of 70.6 mm with different percentages of CC. To relate the EMI spectra, statistical metrics such as root mean square deviation (RMSD) has been used for all cement mortar mixes. RMSD was found to be reasonably effective in estimating the hydration in terms of compressive strength gain of cement mortar over the time.

In the light of the increasing demand for cement in construction and dwindling reserves of cement-grade limestone, the blend of ground limestone and lower grade calcined clay has emerged as a potential candidate for large volume cement replacement. Studies of such ternary blended systems in paste and concrete reveal very interesting physical and chemical effects on the structure development, strength and durability performance. This paper describes the results of durability studies conducted at IIT Madras on concretes prepared with limestone calcined clay Cement, in comparison with ordinary Portland cement and fly ash-based cement. The focus of the study was to delineate the chemical and physical effects caused by the binder composition on durability indicators for chloride-induced corrosion. The experimental strategy involved the assessment of the pore structure evolution and electrical properties on cementitious pastes, along with measurement of the durability parameters based on moisture absorption, chloride migration and diffusion. The results from the study reveal the complex interplay of the various factors that lead to improved performance of the blended cementitious systems. The synergistic interactions of the blend of calcined clay and limestone impact the physical structure positively at early ages as opposed to fly ash systems, which require prolonged curing to realize their potential.

In the context of climate changes, limestone calcined clay cement (LC3) represents a very promising alternative to ordinary Portland cement (OPC), not only to reduce by up to 30% the CO2 emissions but also to dramatically increase service life. Notably, the resistance to chloride ingress is significantly higher in LC3 systems, although understanding and quantifying the mechanisms responsible remain a challenge. In this study, the effect of porosity on chloride diffusion was investigated by comparing at water-to-binder ratios w/b = 0.3–0.5, OPC pastes and LC3-50 pastes (50% clinker, 30% calcined clay, 15% limestone and 5% gypsum). Chloride diffusion was measured using a mini-migration test developed for paste samples. The microstructure was further characterized in terms of porosity and diffusion tortuosity as obtained from the formation factor. The results showed how increasing the tortuosity of the porous network (by changing the binder type) led to a higher reduction of the chloride diffusion coefficient compared to decreasing the total porosity with lower water-to-binder ratios. These results strengthened the importance of the tortuosity as one of the key microstructure features to explain and model the chloride diffusion in alternative cementitious systems (along with the chloride binding and the composition of the pore solution).

Durability of reinforced concrete in marine environment depends largely on chloride resistance of concrete which should be always ascertained. In this article, an effect of limestone calcined clay (LC2) on chloride resistance is, thus, investigated. Limestone calcined clay cement with 7.5, 15, and 30% replacement by weight was tested with various methods. Rapid chloride penetration test (RCPT) was performed by measuring the total charge passed value according to ASTM C1202. The age of samples for RCPT was 60 and 90 days. At the age of 90-day, control sample had the charge passed of 4284 coulombs. The 7.5%, 15%, and 30% LC2 replacement samples had the charge passed of 3490, 2486, and 926 coulombs, respectively. Replacing cement with limestone calcined clay could decrease chloride ion penetrability of concrete. Moreover, the chloride binding capacity of LC2 cement paste was also tested by 42-day exposure in different concentration of NaCl solution. For 0.3 M concentration of NaCl solution, the bound chloride contents of 30% LC2 cement paste and control cement paste were 25.40 and 12.09 mg/g, respectively. The results significantly showed that LC2 cement paste had higher bound chloride content than control paste for any rate of replacement. Cement paste samples were submerged in NaCl solution for 168 days. Total and free chloride contents of pastes at different distance from exposed surface were tested according to ASTMC1152 and ASTMC1218, respectively, to compare apparent chloride diffusion coefficients of LC2 cement pastes and that of control cement paste. The results clearly showed that total chloride content of LC2 cement pastes was lower control paste. The chloride diffusion coefficient and surface chloride content of 30% LC2 was 150.05 mm2/year and 0.67% by weight, respectively. The cement paste with 30% LC2 had lower chloride diffusion coefficient and surface chloride content than control cement paste up to 50%

Nowadays, various concrete systems with fly ash, slag, limestone calcined clay, etc. exhibiting high ionic resistivity are used to enhance the resistance against chloride-induced corrosion. This study deals with the corrosion assessment of steel in three cementitious systems, namely (i) Ordinary Portland Cement (OPC), (ii) OPC + 30% fly ash, and (iii) limestone calcined clay cement (LC3) exhibiting ‘low to moderate’, ‘moderate to high’, and ‘very high’ resistivities, as per AASHTO T358 (2017). Results from the ASTM G109 and impressed current corrosion (ICC) tests were evaluated. It was found that LC3 systems have excellent resistivity against the ingress of chlorides and provide better corrosion resistance. It was also found that the corrosion products formed on steel in LC3 systems are different and less expansive than that found in the OPC systems.

When calcium bearing phases of hydration products react with carbon dioxide, it results in formation of calcium carbonate. The consumption of alkaline compounds leads to reduction in the pH of concrete, thereby affecting the stability of hydration product and increasing the risk of steel corrosion in low alkaline environment. The reaction of pozzolans with calcium hydroxide reduces the reserve alkalinity in the hydrated cement paste which accelerates the rate of carbonation. The main objective is to determine the change in mechanical and transport properties of carbonated and non-carbonated samples. In this investigation, a cement blend mix has been prepared using OPC and limestone calcined clay. Mortar specimens were prepared for using blend to sand ratio as 1:3 to prepare samples for testing compressive strength, sorptivity and porosity using boiling water test. Paste samples were cast to measure reserve alkalinity and carry out thermogravimetric analysis. Some specimens were kept in carbonation chamber for 90 days at 3% CO2 concentration and 60% relative humidity for carbonation to occur at an accelerated rate while the other samples were sealed to avoid carbonation. The results show that after carbonation, there is slight decrease in the compressive strength and increase in sorptivity after carbonation of LC3.

In this paper, durability parameters (water sorptivity, water penetration, chloride penetration and natural carbonation) are studied on conventional mixtures (w/cm = 0.50). Concretes were elaborated with Portland cement (PC) and blended Portland cements, containing 25% replacement by illitic calcined clay (ICC) and low-grade kaolinitic calcined clay (KCC). They were characterized by slump, compressive and tensile strengths and bulk porosity. Water sorptivity (ASTM C 1585) was determined on concretes cured 2, 7 and 28 days; water penetration test (EN 12390) and chloride penetration (ASTM C 1556) were determined on concretes cured 28 days. Carbonation depth undergoing a good and very good curing was assessed using a phenolphthalein indicator at 3 and 6 months of natural exposition. Results show that water sorptivity is reduced when concrete is curing for 2, 7 and 28 days for all concretes. KCC has a significantly lower sorptivity than PCC and ICC. At 28 days, the water penetration is deeper for ICC and lower for KCC concrete. All concretes have similar apparent chloride diffusion coefficients. After six months, the natural carbonation of all concretes is less than 2 mm, with a slightly lower performance of ICC and KCC than PCC.

Waterproofing of concrete is important to prevent deterioration of concrete due to corrosion and carbonation. Integral waterproofing admixtures give varied results, in terms of strength of concrete and transport properties, with the change of cementitious materials. Presently, there is a lack of substantiated data for blended cement in terms of their efficacy with waterproofing admixtures especially Limestone Calcined Clay Cement (LC3), which is a relatively new cement blend. This paper presents an experimental study on transport properties of mortar with the use of integral waterproofing admixtures. In this study, mortar mixes were prepared with LC3 using different waterproofing admixtures, and the results have been compared with OPC and other blended cement as well. The effects on transport properties were determined by carrying out various tests, including the sorptivity test and boiling water test. The results were found to be useful in understanding the influence on capillary pores and pore volume due to the action of various waterproofing compounds in different cement blends.

Combining the advantages of both lightweight concrete and self-compacting concrete in a single entity will be highly beneficial in offshore structures. Due to the addition of porous lightweight aggregate durability of these structures in adverse environment will be a matter of great concern. From the earlier studies, it was clear that the inclusion of metakaolin in normal aggregate concrete exhibits superior durable performance. The present study evaluates the effect of metakaolin in the corrosion performance of the high strength self-compacting lightweight aggregate concrete. The corrosion properties were accessed using various experimental techniques such as rapid chloride penetration test, surface resistivity, alkalinity and corrosion rate. All the concretes were developed with binder content 550 kg/m3 and water-binder ratio maintained as 0.28. The metakaolin replacement percentages have been varied as 7.5, 10, 12.5 and 15%. The results indicate that all the durable parameters of concretes have been improved due to the inclusion of metakaolin. Also pH level of all the concretes is well above the threshold value. This evidence justifies that metakaolin is potential material for the development of high performance lightweight self-compacting concrete.

The use of ternary blended cements with limestone filler and calcined clays can improve the durability of concrete structures exposed to aggressive environments and extend their service life. In sulfate-rich environments, the effects of supplementary cementitious materials depend on the replacement level and the progress of hydration. Low level of limestone filler contributes to the stabilization of AFt due to formation of monocarboaluminate. However, high replacement increases the effective w/c ratio and the capillary porosity, favoring the sulfate penetration. The use of active pozzolans improves sulfate resistance by reducing portlandite content and the permeability, which minimize ettringite and gypsum formation and sulfate penetration. It is generally assumed that curing prior to sulfate exposure should be extended to allow the pozzolanic reaction to progress. It is currently uncertain the effectiveness of calcined clay in combination with limestone filler when the cement is exposed immediately to aggressive environments. Typical structures affected by sulfate attack are commonly built in situ, thus being exposed to the aggressive environment since casting. This paper analyzes external sulfate attack of blended cements with 30% replacement by combinations of limestone filler and/or calcined clay exposed to Na2SO4 solution at two days after casting. For that, expansions, mass variation, visual appearance and compressive strength are monitored in mortars and pastes during 6 months. The evolution of microstructure was evaluated with XRD. Despite the lack of curing prior to sulfate exposure, cement with calcined clay showed an excellent resistance to external sulfate attack, while limestone cements presented a worse performance.

This work aims to assess the potential of limestone calcined clay cement (LC3) in mitigating alkali–silica reaction (ASR). Two General Purpose (GP) cement substitution rates using calcined clay and limestone were tested: 20 and 30% with a ratio 2:1 by mass of calcined clay and limestone. Silica ions dissolution of rhyodacite rock used as reactive aggregate, expansion of mortar specimens using the accelerated mortar bar test (AMBT) and the initial chemical composition of the mortars pore solution were investigated. The combination of calcined clay and limestone significantly reduced the expansion of mortar bars compared to reference mortar using 100% GP cement. The reduction in mortar bar expansion correlates well with the reduction in alkalis ions concentration and pH of the pore solution of LC3 mortars compared to reference mortar. 30% OPC substituted by calcined clay and limestone seems to be able to mitigate the risk of ASR in concrete using alkali-reactive aggregate.

The combination of Portland cement and mineral additions allows reducing the carbon footprint of cement-based materials and improving their resistance to several environmental actions. The development of binary binders is limited by the reactivity of pozzolanic materials at high substitution levels and the availability of industrial by-products such as slags and fly ash. Thus, it is necessary to develop new cements from natural raw materials such as clay and limestone and to combine them to design ternary binders with higher hydraulic activity. The study is focused on mortar based on binary and ternary binders (Portland cement, metakaolin, limestone filler) with a maximum substitution level of 45%. Two sets of mortar mixtures with different water-to-cement ratios were designed. The experimental program includes the determination of strength, porosity, hydration heat, portlandite content, shrinkage and natural carbonation. The analysis of data aimed at correlating the evolution of mechanical properties with hydration degree and reactivity of calcined clays. The results actually showed that the performances of ternary binders closely depend on the properties of the three studied metakaolins, especially their production process and physical properties. For a given substitution level, the studied ternary binders clearly showed better performances than other mineral additions. The reduction of water-to-cement ratio resulted in an acceleration of pozzolanic reaction. This allowed an improvement of short-term strength as well as potential durability.

Through the study of binary and ternary blends, the work is focused on the influence of the substitution of the cement by calcined clay and/or limestone filler on the mechanical properties. Besides of an ordinary Portland cement, three binders were analyzed: one binary blend where 30% of the cement is replaced by calcined clay and two ternary blends—one with 15% of calcined clay and 15% of limestone filler and the other with 30% of calcined clay and 15% limestone filler. First, the results show that the substitution rate does not influence the overall degree of reaction determined with the cumulated heat evolution. Then, we notice that the behaviors of the 30% substitution blends (binary and ternary) are similar when the ternary blend with only 55% of Portland cement is clearly different. Finally, the mechanical properties brought back to substitution rate seem to be enhanced for the ternary blend with only 55% of Portland cement. This shows that the limestone filler allows to keep, and even to enhance, the mechanical properties of a binary blend by increasing the level of substitution.

As limestone calcined clay cement (LC3) is on the verge of commercialization around the world, it is becoming more and more important to understand its durability under various conditions. It has been shown that LC3 is especially useful to achieve the cohesion required in self-compacting concrete. However, the influence of the higher paste content in the self-compacting concrete related to a regular workability concrete is not well understood. In this study, self-compacting concrete and normal vibrated concrete were prepared using fly ash and limestone calcined clay pozzolan, at various replacement levels of 20, 35 and 50%. The mixes were designed to have similar strengths, and their sorptivity and porosity were measured after curing for 28 days. The results indicate that self-compacting concrete has better durability characteristics than normal vibrated concrete made of similar strength grade.

In the present work, limestone powder (LSP) and calcined clay (metakaolin, MK) were used as mineral fillers in two different mixtures of high-performance self-compacting concrete (SCC). In the first mixture, LSP was used alone as the mineral filler, whereas in the second one, the mineral filler consisted of the blend of LSP and MK. For both SCC mixtures, dune sand was used as fine aggregate and crushed limestone particles were used as coarse aggregate. Both SCC mixtures were prepared using a total powder content of 500 kg/m3 (400 kg/m3 Portland cement and 100 kg/m3 mineral filler), a water/powder ratio of 0.3, and a fine/total aggregate ratio of 0.4. Dosages of superplasticizer and stabilizer were optimized through trials satisfying the self-compactability requirements. Performance of the SCC mixtures was evaluated in terms of selected mechanical properties, durability characteristics, and resistance against reinforcement corrosion that included compressive and splitting tensile strengths, modulus of elasticity, water penetration depth, rapid chloride permeability, electrical resistivity, and reinforcement corrosion monitoring. Both SCC mixtures achieved 28-day compressive strength (above 60 MPa), splitting tensile strength (above 5 MPa), and modulus of elasticity (above 40 GPa), low water permeability, very low chloride permeability, and negligible corrosion risk, indicating suitability of using LSP and MK as mineral filler for producing high-performance SCC. The self-compactability and mechanical properties of the mixture with the blend of LSP and MK were slightly better than the mixture with LSP alone; however, both mixtures showed the same durability characteristics and resistance against reinforcement corrosion.

Concrete has never been an environmental amiable substance neither for make nor for its use, or to dispose. Huge amount of water and energy is being used to get the raw material to make concrete and excavating for sand and other aggregates which cause ecological annihilation and air contamination. Concrete is also an assertion to be the colossal cause of carbon emission in the earth’s atmosphere. Some assert that concrete is accountable for up to 5% of the world’s cumulative carbon secretion which contributes greenhouse gases. Mixing of water in cement and cement production generate a huge amount of CO2 gases realizing in environment seriously detrimental ozone layer causing high temperature increasing seasonal temperature variation. This paper is a probe with partial replacement of cement by calcined clay in concrete collected from two cities. The work deals with compressive strength, split tensile strength, water absorption. Data therefore presents over a maximum curing of 28 days. The substitutions proportions used were 4, 8, 12, 16 and 20% by weight of cement.

The present research focuses on durability aspects of limestone calcined clay cement (LC3) using different piezo configurations specifically aimed at acid attack. The experimental study was carried out on concrete cylindrical specimens of ordinary Portland cement (OPC) and LC3, which were immersed into the sulphuric acid (H2SO4) and hydrochloric acid (HCl) solution. Different piezo configurations were installed to acquire the data in the form of conductance and susceptance signatures via electro-mechanical impedance (EMI) technique. From the acquired data, the equivalent structural mass parameter was extracted which was then validated with actual mass obtained by physical measurement. Based on the results, it can be concluded that the equivalent mass parameter is able to identify the mass loss in the specimens subjected to acidic environment non-destructively.

In this study, the compositional robustness of limestone-calcined clay combination as clinker replacement in cement, and its effect on concrete performance was assessed in detail. The ratio of limestone-calcined clay in the LC3 with 55% clinker was varied from 1:1.25, 1:2 and 1:3.5 with increasing limestone dosage from 10 to 20%. Additionally, binary binders with calcined clay at 30% (CC30) and 42% (CC42) replacement were studied for benchmarking and dissociating limestone’s contribution to the performance of LC3 binder. Concretes were prepared with 360 kg/m3 and 0.45 with fly ash-limestone and calcined clay-limestone combinations. Early hydration benefits from limestone ensured that binders with a combination of limestone-calcined clay showed higher compressive strength than the binary substitution of 45% calcined clay binder up to 180 days. The higher reactivity of calcined clays resulted in a tremendous rise in resistivity for all calcined clay binders by early curing duration, i.e. 7 days. Resistivity development confirmed the synergistic impact of limestone-calcined clay combination, which reaffirms the potential ability of the calcined clay to complement the utilization of higher amount of less energy-intensive limestone in the cementitious materials. Additionally, the influence of varying limestone-calcined clay ratio on time-dependent change in chloride resistance by migration test was probed, and the impact of chloride build-up at the steel surface during service life is also discussed.

With the aim of reducing the environmental impact associated with cement production, during the last decade, different percentages of clinkers have been replaced in cement by supplementary cementitious materials (SCMs). When new SCMs are incorporated in concrete, it is necessary to evaluate, not only the mechanical properties (as strength and stiffness) and the durability but also the deformations that can generate cracking and decrease the service life of the structures. This paper is focused on the study of volumetric changes at the early ages of pastes made with blended cements with the addition of illitic calcined clays from the Buenos Aires province, Argentina. The objective of this work is to present preliminary studies on the effect of illitic calcined clays on the autogenous and chemical shrinkage of pastes. The studies were made on pastes (water/cementitious material ratio equal to 0.275) using a Portland cement type II/A-L, with the incorporation of different percentages (10%, 20% and 30%) of illitic calcined clays. A device for direct deformation measurement was used to register linear dimensional changes; the general guidelines of ASTM C 1608 were applied for the determination of chemical and autogenous shrinkage. The volumetric changes measured with direct device are the sum of the chemical and autogenous shrinkage accompanied with the expansion due to the heat released during hydration. It was found that pastes incorporating calcined clays had early deformations similar to or lower than reference paste without clay.

The present study investigates the effect of concrete mixture proportioning on two major performance parameters which include compressive strength and surface resistivity for limestone calcined clay cement (LC3) and FA30 (70% OPC + 30% Class F fly ash) binders. The findings show that there was a significant early strength development of about 38–88% of the 28th-day strength by 3 days in the range of concrete studied, despite only 50% clinker in LC3 binder. In comparison, FA30 with 70% clinker had about 30–61% of 28th-day strength by 3 days. All LC3 concretes had higher resistivity than FA30 counterparts indicating higher resistance to ionic transport in the binding phase. By 90 days of curing, the surface resistivity values varied between 50–200 and 10–80 kΩ cm for LC3 and FA30 concretes, respectively. Furthermore, a dramatic rise in surface resistivity was seen by 7 days for LC3 concretes conforming to the early impact of calcined clay on the concrete physical structure. In the case of fly ash concretes, resistivity measurements showed a major increase only after 28 days. The pore structure refinement was found to be the significant factor controlling the early development of durability indices in LC3 concretes.

Geopolymer mortars were prepared by treating calcined clay (CC) with sodium hydroxide and sodium silicate solutions in the presence of alccofine powder (AF) and recron fiber (RF). Alccofine powder increased the compressive strength of geopolymer mortar due to increased geopolymerization and filling of the pores. Recron fiber on the other hand decreased the strength. This was due to water absorption by the fiber. SEM was used to study the morphology. Rapid chloride permeability test showed that geopolymer mortar in the presence of AF is much more durable as compared to other mortars in the absence of AF. Durability of mortars in sulfuric acid indicated that geopolymer mortar containing AF is quite durable as compared to that containing RF. The overall results have shown that calcined clay of high surface area on reaction with concentrated NaOH (14 M) in the presence of AF gives mortar of high strength even at room temperature curing.

Loam is a very ecological building material with a great potential. It is found worldwide and completely recyclable. Under dry conditions, loam develops high strength values. However, loam is not moisture-resistant. Permanently acting moisture reduces the strength dramatically. The idea to improve the water resistance of loams is adding materials to the loam with the same basic structure. Therefore, metakaolin, calcined clay, here, so-called metaclay and a specially developed geopolymer were selected. Blends of four different loams with different amounts of these additives were produced and tested. Criteria for an evaluation are the dynamical modulus of elasticity and the water resistance. These studies were supplemented by structural investigations using a light and a scanning electron microscope and XRD. The results are very interesting, and the effects depend strongly on the kind of loam too. Not all additives lead to an improvement of the mechanical properties. Nevertheless, not the samples with the highest mechanical values show the best water resistance behavior. Obviously, a balanced structure between loam and additive particles is necessary. Such structures are not so dense but enough resistant to water to guarantee the positive property of fast water absorption and delivery of natural loams. The service lives of the loam prisms could be increased from certain minutes to several days. The best results are obtained with geopolymer-based materials as an additive. This is not so surprising because both the loam and the geopolymer form aluminosilicate structures during hardening.

The technology for the manufacture of a ternary cement based on Portland cement, calcined clay and limestone has gained interest in the region Latin America. Several cement companies have embraced the technology, and many of them are moving toward industrial production within the next 2–3 years. The introduction process must overcome a series of challenges associated with: (i) the choice of clay deposits rich in kaolinitic clays that are accessible to cement plants. Depending on the geological origin, several accompanying mineral can come with the clay, and some of them can compromise the reactivity of the activated clay; (ii) the choice of technology for clay calcination. Since this is a CAPEX dependent issue, each company has its own strategy for implementing the technology. The main trends are refurbishing old clinker kilns to convert them into calciners; opting for rotary kilns for the calcination and alternatively for flash calciners; (iii) The grinding strategy, which can opt for separate grinding or co-grinding, each with benefits and setbacks. Issues like grinding aids can be crucial in terms of achieving the best particle size distribution and avoiding excess grinding of some components and (iv) The strategy for the use of the ternary cements in mortar and concrete. The high specific surface of the calcined clays poses a challenge to the manufacture of concrete, since water demand is high. The strategy for the use of plasticizers differs from ordinary practices with Portland cement, but good flowing concrete can be achieved with a relatively high amount of calcined clay in its cement. Most of the results discussed in this paper are produced through the interaction of the Cuban Technical Resource Center with clients in the region.

Calcined materials have a long history of use in concrete structures, with some now over 80 years old. Beginning in the 1950s, by-product supplementary cementitious materials (SCMs) began to replace natural pozzolans because of cost, availability, performance, and benefits of reuse. Specifications, mix designs, and performance data collected were built around an assumed continuous supply of these recycled SCMs. SCM availability, quality, and cost, especially for fly ash, is now in question. This has brought significant interest in alternative SCMs to provide durability in concrete structures. Calcined clay now appears to be a viable option going forward for concrete mixtures in the United States, especially when combined with ground limestone. This paper discusses the history of SCM use in the USA, potential for calcined clay use in concrete in the USA, barriers to use, and a path forward to overcome those barriers with only minimal changes in concrete specification, production, and placement methods. This paper will also discuss options to apply these and other potential strategies to other markets to speed adoption of concrete calcined clay use.

Limestone calcined clay cement (LC3) is being developed as a low-carbon alternative to conventional cements. The cement has the potential to reduce CO2 emissions by up to 30%, at the same time, demonstrating a higher performance in many types of exposure conditions. Being a conservative industry, the introduction of a new cement is a challenging process with many technical, commercial, psychological and political hurdles. Additionally, it is understood that the solutions for the reduction of CO2 emissions will be varied and will depend on various factors such as the availability of raw materials, the environmental conditions and the construction practices. It is, therefore, important to ensure that the engineering properties of concretes produced using any cement are well understood and that right type of cement is used for the right application. This article discusses the challenges that need to be overcome for the introduction of LC3 and the applications where the cement is especially at an advantage or disadvantage.

Portland cement is one of the most important binding materials in construction industry. It is manufactured at a very high temperature and thus consumes lot of energy. It consumes lot of good quality of limestone and at the same time it emits large quantity of CO2 responsible for global warming. Number of measures is being made to reduce CO2 emissions and decrease consumption of limestone and energy. One of the ways is to use waste natural materials like China clay, which is available many parts of India. Limestone calcined clay cement (LC3) was produced on a pilot scale in a JK Lakshmi cement grinding unit (Jhajjar, Haryana, India). Due to high water consistency compare with OPC cement. JK Lakshmi cement had developed the improved version of LC3 cement with low water consistency. LC3 cement are being studied all over the world but some of problems persist. In this paper, we have studied the hydration and durability of improved version of LC3 cement. Water consistency, setting times, non-evaporable water contents, compressive strength measurements, water percolation and X-ray diffraction studies were made to understand the hydration process.

New green additives are an innovative additive for concrete produced from widely available waste materials as a step towards sustainable infrastructure development. Being a versatile product it can be used as a direct additive during concrete production or as a partial clinker replacement. New green additives improve the properties of concrete by several simultaneous processes. The aluminosilicate of new green additives contributes in the pozzolanic reaction; smaller particle size of new green additives imparts filler effect providing extra sites for nucleation and growth of hydration products, the reaction of carbonates helps in improving efficiency.

Recent developments on the use of magnesium silicate (MgO–SiO2) as a potential binder material have been promising. Brucite, produced from the hydration of magnesium oxide, reacts with amorphous silica to produce magnesium silicate hydrate (M-S-H). Currently, silica fume is used as the primary source of silica in the majority of research into the M-S-H binder system. With increasing emphasis on sustainable construction, the identification and use of practical silica sources on a global commercial scale are imperative. The use of calcined kaolinitic clays, as supplementary cementitious material, has been widely established in the Portland cement industry and can also be used in production of magnesium silicate-based binder. In this study, the feasibility of using calcined kaolinitic clay alongside magnesium oxide was investigated. The effect of clay on the mechanical properties and hydration characteristics of the binder system are reported.

The study is focused on the evaluation of fresh and hardened properties of pastes and concrete with LC3. The plastic and hardened properties of LC3 are analyzed and compared with OPC 53. A comprehensive study is done on identifying the optimum admixture type for best LC3 paste fresh state properties and compared with OPC 53, PPC, PSC, OPC + 50% PFA (high-volume fly ash) and OPC + 70% GGBS (high-volume GGBS) pastes at varying water–binder ratios (w/b). Fresh and hardened properties of LC3 concretes are analyzed and compared with OPC, PPC, PSC, high-volume fly ash, and high-volume GGBS concrete. The concrete study is focused on achieving LC3 concrete fresh properties with regard to ready mix concrete industry requirements. The durability factors like resistance to chloride ion penetration, water permeability, and water absorption are studied on LC3 concrete and compared with OPC, PPC, PSC, high-volume fly ash and high-volume GGBS concrete. The study also compares material cost of M40 grade concrete in major Indian metro cities and arrives at a landed basic price for LC3 (in terms of percentage of OPC price) in these cities for commercial viability of LC3 use in Indian ready mix industry.

Historic lime binders were often modified by the addition of materials containing reactive silicates and aluminates. Roman builders utilized volcanic deposits from Pozzuoli near Naples, as the addition of this volcanic ash improved the performance of mortar. Pozzolans can be of natural or artificial origin; traditional artificial pozzolans were produced from natural materials, such as clay, after heat treatment. In India, pozzolan use was introduced by Mughals, and fired clay brick or ‘surkhi’ was extensively used in medieval times to improve mortar consistency and strength. However, much attention may not have been given to the mineralogical composition and firing temperature of clay, which are critical in determining the pozzolanic activity. In the present study, three different types of clays—kaolinite, montmorillonite, and a sundried brick from the field—were fired to temperatures from 600 to 900 °C to assess pozzolanic activity. The clay crystal structures are disrupted, and an amorphous phase is produced by heating at a temperature range of 700–900 °C. The crushed sundried brick obtained from the field was not pozzolanically active at any of the temperatures. The maximum pozzolanic activity was obtained at 800 °C for the kaolinite and montmorillonite clays, and the fall of pozzolanic activity after this temperature can be attributed to the formation of new minerals such as mullite and hematite. These commercial clays can be used as pozzolans in intervention mortars if they are heated between 700 and 900 °C.

Current study explores the understanding of various parameters such as the role of aluminum powder dosage, water-to-binder ratio, and initial curing temperature on the production of lightweight blocks. Three different cementitious systems were used: limestone calcined clay cement (LC3), Portland pozzolana cement, and ordinary Portland cement. The aluminum powder dosage and the water-to-binder ratio clearly influence the hardened properties of blocks, whereas the initial curing temperature does not show much improvement to overall properties. Hardened properties such as dry density, compressive strength, and water absorption of blocks were evaluated. The required aluminum powder dosage varies from system to system, and it depends on the required density. To maintain lower density, OPC system required higher dosage of Al powder, and it showed lower strength compared to other systems. LC3-based lightweight blocks are produced with 3 MPa strength, and it showed good performance compared to other systems.

Small-scale production of low-cost cements can be an alternative to the conventional cement in the masonry applications. Lime-based products can potentially replace ordinary Portland cement (OPC) in the production of masonry mortar. Lime–pozzolana cement (LPC) is one such binder which can be produced using low capital-intensive infrastructure. They can be used as alternatives to conventional mortar in low-rise load-bearing masonry applications. A variety of locally available ingredients can be used along with LPC to produce moderate-to-high-strength mortars. This paper provides the details of the mortar mixes which have been produced using predominantly soil and brick powder. An attempt has been made to mobilize the strength gain not only through the hydration of the LPC and pozzolanic materials but also through low-molar alkaline activation. It is well known that alkaline solution can be used with reactive silica and/or alumina, and alkali activation can be achieved even at ambient tropical temperatures. This paper provides the details of how the alkaline solution was optimized. Mortars need to be evaluated for strength and workability. All the strength properties needed for classification of mortar have been evaluated. It is found that the strength development depends on the combination of pozzolanic reaction and geopolymerization. All the mixes achieved adequate strength for application in masonry construction. The masonry properties are comparable to cement mortar, and some values have outperformed.