Calcined Clays for Sustainable Concrete

Table of Contents

1. Frontmatter

2. The Experience of Cuba TRC on the Survey of Kaolinitic Clay Deposits as Source of SCMs—Main Outcomes and Learned Lessons

   Adrián Alujas Díaz, Roger S. Almenares Reyes, Florencio Arcial Carratalá, Luis A. Pérez García, Carlos A. Leyva Rodríguez, José F. Martirena Hernández

   Abstract

   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.

3. Potential of Selected South African Kaolinite Clays for Clinker Replacement in Concrete

   Emmanuel S. Leo, Mark G. Alexander

   Abstract

   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.

4. Potential for Selected Kenyan Clay in Production of Limestone Calcined Clay Cement

   Joseph Mwiti Marangu, Kyle Riding, Anfal Alaibani, Abla Zayed, Joseph Karanja Thiong’o, Jackson Muthengia Wachira

   Abstract

   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.

5. Feasibility Study for Calcined Clay Use in the Southeast USA

   Brandon Lorentz, Hai Zhu, Yuriy Stetsko, Kyle A. Riding, Abla Zayed

   Abstract

   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.

6. An Approach for the Evaluation of Local Raw Material Potential for Calcined Clay as SCM, Based on Geological and Mineralogical Data: Examples from German Clay Deposits

   Matthias Maier, Nancy Beuntner, Karl-Christian Thienel

   Abstract

   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.

7. Clay Deposits from the Northeastern of Cuba: Characterization, Evaluation, and Use as a Source of Supplementary Cementitious Materials

   Roger S. Almenares Reyes, Adrián Alujas Díaz, Carlos A. Leyva Rodríguez, Lisandra Poll Legrá, Luis A. Pérez García, Sergio Betancourt Rodríguez, Florencio Arcial Carratalá, José F. Martirena Hernández

   Abstract

   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.

8. Potential of Marine Clay for Cement Replacement and Pozzolanic Additive in Concrete

   Hongjian Du, Anjaneya Dixit, Sze Dai Pang

   Abstract

   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.

9. Evaluation of Ceramic Waste from Goa as SCM

   Harald Justnes, Christian J. Engelsen, Tobias Danner, Monica N. Strøm

   Abstract

   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.

10. Potential of Calcined Recycling Kaolin from Silica Sand Processing as Supplementary Cementitious Material

    Matthias Maier, Benjamin Forster, Nancy Beuntner, Karl-Christian Thienel

    Abstract

    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.

11. Comparison of Brick Clays and a Kaolinitic Clay Regarding Calcination and Performance in Blended Cement Mortars

    Nsesheye Susan Msinjili, Patrick Sturm, Hans-Carsten Kühne, Gregor J. G. Gluth

    Abstract

    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.

12. Utilization of Clay Brick Waste Powder for Partial Replacement with Cement in Cement Mortar

    Hemraj R. Kumavat, Narayan R. Chandak, Dhananjay J. Jadhav

    Abstract

    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.

13. Qualifying of Low Grade Clay for Geopolymer Mortar: A Preliminary Assessment

    Sreedevi Lekshmi, Reesha Bharath, Sunitha K Nayar, J Sudhakumar

    Abstract

    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.

14. Alkaline Activation of Blended Cements with Calcined Illitic Clay Using Glass Powder Wastes

    Mónica A. Trezza, Edgardo F. Irassar, Viviana F. Rahhal

    Abstract

    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.

15. Why Low-Grade Calcined Clays Are the Ideal for the Production of Limestone Calcined Clay Cement (LC3)

    Sreejith Krishnan, D. Gopala Rao, Shashank Bishnoi

    Abstract

    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.

16. The Effect of Calcite in the Raw Clay on the Pozzolanic Activity of Calcined Illite and Smectite

    Tobias Danner, Geir Norden, Harald Justnes

    Abstract

    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.

17. Activated Calcined Clays as Cement Main Constituent

    Simone Elisabeth Schulze, Roland Pierkes, Joerg Rickert

    Abstract

    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.

18. Simple and Reliable Quantification of Kaolinite in Clay Using an Oven and a Balance

    François Avet, Karen Scrivener

    Abstract

    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.