Proceedings of the RILEM Spring Convention and Conference 2024

Accelerated urbanisation generates large quantities of construction and demolition waste (CDW). Most of this waste is inert and poses no environmental risk. In France, according to article R541–8, 72% of this waste is inert, and 26% is non-hazardous. Landfilling CDW involves ecological risks such as water and air pollution and a disastrous visual impact on the landscape. Concrete waste is the largest component of CDW, producing recycled gravel (RG) and recycled sand (RS). These recycled aggregates (RA) are natural aggregates (NA) coated with around 30 to 40% of old mortar. For many years, numerous researchers have studied the characteristics of concrete made with RA. However, RA generally contains non-hazardous waste (NHCDW) such as bricks, bitumen, earthenware, tiles, plastics, etc. There is a general lack of knowledge concerning the effects of NHCDW in RA. No more studies are available focusing on the impact of NHCDW on the behaviour and acceptability criteria of CDW materials used in activities such as backfilling, building, and landscaping. This study is part of the European project 101091679-MOBICCON-PRO (MOBile and Innovative Circularity for CONstruction PROducts)-HORIZON-CL4–2022-TWIN-TRANSITION-01). It aims to study the effect of these non-hazardous wastes on mortars’ physical and mechanical properties. The main objective is to establish threshold values for NHCDW (sand) to guarantee the required mortar properties. The experimental approach involves characterising NHCDW sands (density, porosity, water absorption) and designing mortars containing at least 30% of these sands with different proportions. The main properties studied are mechanical strength, porosity and density of the mortars.

Lightweight structural concrete offers an opportunity to decrease the dead load which is of great importance for improving both resource efficiency and earthquake behaviour of reinforced concrete and combined structures. Manufactured lightweight aggregate however are characterised by high embodied energy which reduces the environmental benefits of lightweight concrete. The aim of the current study was to evaluate the possibility for up-cycling of clay bricks construction and demolition waste (CDW) as aggregate in structural concrete. Three concrete compositions having different content of recycled bricks aggregate (RBA) were designed. The main characteristics of that concrete, required for the design of reinforced concrete structures, were determined. The bonding between RBA concrete and steel reinforcement bars was studied. Some durability (drying shrinkage and carbonation) were also investigated. It was concluded, that the valorization of masonry CDW as aggregate for concrete is possible and, depending on the RBA content, concrete for various purposes might be produced – an ordinary structural concrete when RBA share is of order of 20% of the total coarse aggregate and a lightweight concrete, having reduced dead load and satisfactory compressive strength and bonding with rebars when the replacement rate varies from 60% to 100%. Other aspects of the RBA lightweight concrete such as modulus of elasticity, shrinkage and carbonation depth showed lower performances. Therefore, RBA containing concrete requires adjustments in the mix design and in the behaviour prediction models, as well as measures to ensure the durability, similar to those for concrete with other type of lightweight aggregate.

The construction industry's quest for sustainability has heightened interest in alternative construction materials, particularly the adoption of fine recycled concrete aggregates (FRCA) as a viable substitute for natural sand in concrete and mortar. The carbonation of FRCA, attributed to the adhered cement paste, has demonstrated the ability to enhance the properties of fine RCA, thereby broadening its applications. This study delves into an underexplored research area concerning carbonated FRCA, specifically examining their influence on the long-term sulfate and acid resistance of mortar. This inquiry stems from concerns about potential thaumasite sulfate attack, which could arise due to the presence of carbonates resulting from the carbonation process of fine RCA, coupled with moisture exposure. In this investigation, carbonated FRCA serves as a complete replacement for natural sand in mortar mixes, subjected to magnesium sulfate solution and hydrochloric acid. Furthermore, the study evaluates the sulfate resistance of carbonated FRCA mortar with a reduced water/cement ratio and explores the inclusion of ground granulated blastfurnace slag (GGBS) as a partial replacement for Portland cement. Additionally, XRD analysis of samples extracted from deteriorated specimen surfaces provides insights into their mineralogical compositions. This research offers a good understanding of long-term performance implications. By contributing to discussions on sustainable construction practices, it underscores the necessity for further exploration in this promising field.

With the ecological transition and the move towards net zero emission, lithium is the subject of much attention. Lithium is a key element in the manufacturing of batteries for electrical vehicles, which are expected to dominate the market in the European Union from 2035 onwards.Lithium occurs in more than 100 minerals including spodumene, petalite, or lepidolite. In Australia, spodumene is the main source of hard rock lithium. Australia is the world leader in lithium production, with five mines representing almost half of the world’s total lithium production in 2022. It is ranked second in the world in terms of proven reserves, with 6.2 million tonnes.Spodumene contains about 6% Li2O when it is pure. In order to extract lithium, α-spodumene must undergo a phase transformation that is activated by heat. Therefore, the spodumene processing results in several waste components both in the solid and liquid streams. The solid residue may contain aluminosilicates that are intrinsic to the spodumene crystal and other components that are due to the process itself including sodium sulphate (obtained upon sulphating β-spodumene) and various hydroxides that result from the acid neutralisation. Overall, significant quantities of residues can be formed that can become an environmental burden if not reused in a circular economy.The objective of this research is to elaborate geopolymer mortars with different proportions of β-spodumene as alkali-activated materials and slag. It has been established that an optimum binder is obtained with 25% β-spodumene and 75% slag.

The growing interest in repurposing industrial alkaline wastes for construction has driven research toward sustainable practices, aiming to address environmental concerns and circular economy principles. This study focuses on the utilization of carbide lime waste, a by-product of acetylene gas production, in construction materials. The current large amounts of calcium carbide produced worldwide, leading to carbide lime waste, underscore the urgency of finding alternative uses for this material. Carbide lime waste is typically discarded in ponds, a disposal method that poses significant environmental threats. Recycling carbide lime in construction not only addresses waste management issues but also offers a sustainable solution for capturing greenhouse gases via its carbonation. Here we present a comprehensive analysis of carbide lime properties, comparing them with traditional calcitic limes. For this task, we used X-ray diffraction, porosimetry, thermogravimetric analysis, and electron microscopy. Carbide lime, primarily composed of calcium hydroxide, demonstrates unique features, including micro and nanoscale portlandite particles, and compatibility with various building constituents. Our study highlights the challenge posed by impurities in waste carbide lime (i.e., sulfides and heavy metals) and underscores the need for optimal process control. Notably, we unveil the remarkable carbonation dynamics and kinetics of carbide lime, which outperforms traditional calcitic limes. Key developments and findings include the purification and optimization of carbide limes, morphological distinctions in carbonated lime crystals, pore characteristics, and (enhanced) reactivity, as compared with industrial hydrated lime.

Alkali activated materials (AAMs) are an interesting class of alternative construction materials with potentially low environmental impact and physicochemical properties fulfilling the requirements for a wide range of engineering applications. One reason therefore is their ability to utilize mineral wastes and industrial by-products as raw materials to produce clinker-free binders. To date the research is mostly focused on fly-ash, GGBS and metakaolin-based AAMs, whereas the utilization of other probable viable wastes and by-products for AAM production (e.g. metallurgic slags, mineral wools, and construction and demolition waste) are often overlooked. Such wastes and by-products are produced in substantial amounts and frequently deposited in landfills, posing a notable environmental burden. In this work, the systematic evaluation of various Austrian mineral wastes and by-products to be utilized as AAM precursors is presented. First, the physical, chemical and, mineralogical characteristics of wastes were assessed. Thereafter, their potential reactivity as binder components was systematically investigated in AAM paste mixes series. The developed binder systems were investigated by characterizing fresh and hardened pastes through visual observations, spread flow, and compressive strength. Moreover, a fundamental understanding of the environmental material characteristics was attained by leaching tests. This strategy enabled a preliminary reactivity evaluation of different mineral wastes and the development of binder systems, exhibiting high waste content, suitable fresh properties and high strength development, for further tuning and optimization.

Despite dwindling supplies of traditional SCMs like granulated blast-furnace slag (GBFS), a plethora of industrial mineral residues and by-products are currently not utilised in ordinary Portland cement (OPC) or alkali-activated material (AAM) binder systems. In many cases, this is due to unfavourable properties of these materials, such as low reactivity or high contents of harmful substances. This contribution demonstrates how various residues and by-products can be utilised as binder components by a thermal treatment at temperatures >1400 ℃ followed by wet granulation. Through chemical and mineralogical characterisation, it could be shown that resulting materials (“up-slags”) are similar to GBFS, consisting mainly of CaO, SiO2, Al2O3 and MgO with high amorphous contents. Subsequent R3 and activity index tests and fabrication of AAM mortar and paste with a combination of up-slag and non-treated material proved the reactivity of the up-slags in OPC and AAM systems, respectively. The results demonstrate that mineral residues can be valorised as reactive binder components through thermal treatment, supporting a pathway towards a climate-friendly, energy-efficient circular building materials economy while mitigating shortages of traditional SCMs. Through carbothermal reduction, potentially valuable metals (e.g. Fe, Mn, Cr) can be reclaimed during the upcycling process. Further research has also been identified as necessary to improve our understanding of chemical and mineralogical boundary conditions for using upcycled slags as AAM binder components.

The construction industry has a significant effect on the sustainability calendar, in terms of greenhouse gas (GHG) emissions, consumption of natural resource, and waste generation. The manufacture of ordinary Portland cement (OPC) is responsible for around 7% of the global CO2 emissions. Geopolymers are often considered as a potential eco-friendly alternative to OPC because of reduced environmental impact. In recent years, research on the use of construction and demolition waste (CDW) precursors to manufacture geopolymers has attracted worldwide interests owing to several significant advantages. It was found that, however, the reactivity of CDW precursors is generally low and the synthesized geopolymers exhibit low strength in most cases, except special curing regime is employed. Adding ground granulated blast furnace slag (GGBS) benefits to improve the performance of CDW-GGBS-based geopolymers. However, the influence of increasing GGBS/CDW ratio on the properties of geopolymers after ambient curing is not yet well understood. In this study, sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) are used as alkaline solutions, and the effect of raising GGBS/CDW ratio from 50/50 towards 80/20 is investigated on setting time, flowability index and compressive strength of the geopolymer composite (with Na2O/b = 8%, SiO2/Na2O = 1.33 and w/b = 0.35). The test results indicate that an increase in GGBS content has a beneficial effect on compressive strength increase and reduction in setting time until a GGBS/CDW ratio of 70/30. The test data helps to gain a better understanding of the fresh and hardened properties of CDW-GGBS-based geopolymers after ambient curing.

To overcome the common shortcomings such as high brittleness, low toughness, and susceptibility to cracking in geopolymers, a three-point bending fracture test was conducted to study the effects of carbon fiber (CF) length (6 and 12 mm) and different contents (0.3, 0.6, 0.9, 1.2, and 1.5%) on the fracture performance of a recycled powder-based geopolymer (RPG). Parameters such as Load-CMOD curve, peak load, initial fracture toughness, unstable fracture toughness, and critical effective crack were used as evaluation indicators. The results show that the addition of CF within a certain dosage range can improve the fracture performance of RPG; After adding CF to geopolymer, the peak load, initial fracture toughness, unstable fracture toughness, and critical effective crack of the specimen can be significantly increased. These fracture parameters show a trend of first increasing and then decreasing as the CF content gradually increases, reaching their maximum value at a CF volume fraction of 0.9%. At this point, the load–crack opening displacement curve of the specimen was the highest, and the envelope area between the coordinate axes was the largest. Compared with the 12 mm fibre, the 6 mm CF has a stronger enhancement effect on the fracture toughness of the geopolymer.

Reducing the carbon footprint of building material production (~9% of anthropogenic CO2) in the short term is essential to achieve global climate targets. In this regard, certain mineral wastes and secondary raw-materials show large potential as low-CO2 alternatives to be utilized in alkali-activated materials (AAMs). In order to establish mineral-waste-based AAMs as strong future competitors in the construction industry, functional binder systems have to be developed to meet material requirements. Tapping into these unexploited waste streams and exploring their potential as binder components is based on their respective mineralogical and chemical compositions, which determine the desired material properties of the mix-design (expressed e.g. in elemental ratios such as Si/Al). By generating waste-stream-related patterns and variable associations in the context of bulk chemistry and mineralogy of available waste types, factors for the binder development stage are elaborated. During this step, optimum experimental conditions can be achieved by statistical methods such as the design of experiments (DOE) and response surface methodology (RSM), including desirability function-based methods. Such approaches yield time- and/or cost-efficient strategies by optimising the amount of available resources used. For preliminary results the following interactive variables were considered: (i) waste content, (ii) compressive strength and (iii) water/binder ratio. Future focus is given on the evaluation of more complex systems containing a variety waste sources.

Construction and demolition waste represents one of the largest waste streams in the European Union. The soil and stone fraction accounts for the biggest share of these materials. This fraction includes waste materials from tunnelling and excavations, which often contain significant amounts of clay minerals. The demand for raw materials containing clays will increase significantly due to the growing interest for calcined clay as emerging SCM. As the extraction of primary raw materials is to be reduced on the way to a circular economy, secondary materials containing clay must be tapped and new processing methods developed. In this study, different samples from drill cores of planned tunnelling operations and soil excavations were characterized with focus on their mineralogical composition. All investigated materials show a high carbonate and a low to moderate clay content, dominated by 2:1 and 2:1:1 clay minerals. The samples were activated by thermal and mechanochemical activation and the alteration of the physical and mineralogical properties was analysed. The effects of mechanochemical activation on particle characteristics and crystal structures known from studies of pure clays could be confirmed. Mechanochemical activation was proven to significantly enhance the pozzolanic reactivity of a material with a clay content of 40 wt. %, while it showed no benefit regarding the activation of materials with clay contents of 20 wt. % or below. The study demonstrated that mechanochemical activation can have great potential as an alternative activation method for secondary clays, while the scale-up and associated energy demand still need to be proved.

The tailing used in this study, is a by-product of graphite mining and is generated from the floatation process of the finer ore concentrate. It is predominantly silicate and was provided in dry state which comprised a few lumps up to a size of 20 cm. The mineralogy of the mine tailing was studied, based on which, a treatment process of calcination at 850 ℃ for 2 h was adopted.This study examines the microstructure of hydrated cementitious pastes with 10%, 20%, and 40% treated mine tailing as ordinary Portland cement (OPC) replacement and with w/c ratios of 0.3, 0.4, and 0.5. Microstructure was examined after 7, 14, 28, 56, and 90 days of curing. Calcium hydroxide (C-H), calcium silicate hydrate (C-S-H), ettringite, biotite, and quartz were found in cementitious paste with mine tailing samples. Though the hydration products C-H, ettringite, and C-S-H were present in both OPC and OPC-mine tailing mixes, the C-S-H morphology in OPC-mine tailing mixes was different. Higher silica content in mine tailing created a constrained space, resulting in formation of a crumpled foil C-S-H. In OPC-mine tailings samples, C-H nucleation was also observed in later ages such as 56 days indicating secondary hydration. This also results in more compact matrices at the later ages. These findings together with the findings of FTIR and XRD studies give an insight into the hydration of cementitious pastes containing mine tailing.

The growing interest of the international community in a more circular economy has led to the introduction of materials from industrial production and/or recovery in the construction sector, formerly classified as waste for disposal but now considered of fundamental importance for environmental protection and for reducing the exploitation of natural resources. Several studies available in the literature have shown how slags from the production of steel in electric arc furnaces (EAF slags), if properly treated, can be reused for concrete production. Italian steel mills are almost all equipped with electric arc furnaces from which, in addition to the primary material, an estimated 2.1 to 3.1 million tonnes per year of EAF slags can be generated. Unfortunately, about 15–20% of these slags are still destined for landfill disposal. Given the advantages and disadvantages that EAF slags provide to the mix and the possibility of the Italian concrete market to incorporate the entire quantity of slags produced at national level, even with limited replacement percentages, the present work aims to provide a contribution on the study of concrete made with electric arc furnace slags (EAF). Three concrete mixtures have been produced and in two of which the natural fine and coarse aggregates has been replaced by two different percentage of EAF slag, 25 and 50%. Once the mechanical characterisation of the mixtures had been carried out, they were then used to produce full-scale beams in order to study both flexural and shear behaviour.

The aim of this study is to determine the impact of wood biomass ash (WBA) as a substitute for part of the clay on the properties of bricks and to validate laboratory tests in collaboration with brick manufacturers to ensure consistent product quality at industrial production level. Six samples of WBA from different locations in the Republic of Croatia were taken for testing purposes. This work examines the properties of bricks in which WBA partially replaces clay, employing the hand moulding method for brick preparation. Bricks are shaped into both disc and prism forms, allowing us to assess the impact of WBA on various properties such as shrinkage during drying and firing, compressive strength, and water resistance properties, including water absorption by boiling, absorption, and saturation coefficient. The results indicate that even a minimal substitution of only 3% of the clay with WBA significantly influences the water resistance and shrinkage properties. The sample preparation process significantly influences the properties of the bricks, which underlines the need to clearly outline how the samples were fabricated.

This work aims to investigate the possibility of reusing tunnel excavated material to produce an earth-based mortar. The elaborated earthen mortars will be used as interior partition walls or coating to replace plaster materials. The challenge of this technic is multiple, in the context of a strategy to achieve a neutral carbon footprint in building: (1) to avoid the use of gypsum-based materials which, during demolition, can pollute the waste destined for re-use; (2) to reduce as far as possible the need to landfill excavated earth; (3) to develop panels or coating materials with improved thermal efficiency and environmental impact.The mechanical, thermal and hydric properties of excavated earth mortars were characterized after 28 days. A previous study pointed out that the increase of cement content improves the mechanical characteristics but at the same time affects negatively the thermal properties as well as the environmental factor. Hence, all mortars developed were stabilized with cement at 5% by mass. In total, 9 formulations were developed by varying the amount of hemp fibres and tannin powder. It is established that the addition of 1% tannin and 1.2% hemp fibres provided the best solution for optimum mechanical, thermal and hydric properties.This study not only facilitates the development of a material with favourable thermal properties and other suitable usage characteristics but also addresses a crucial issue concerning the management of excavated materials from major infrastructure projects. By proposing a solution aligned with the principles of the circular economy and sustainable development, it offers a practical approach to handling excavated materials in an environmentally responsible manner.

The current global trend towards sustainability has generated a fresh enthusiasm for the conversion of waste materials into useful resources across all industries. Within the construction industry, conventional cement-based materials have played a crucial role in the advancement of infrastructure. However, there is a growing recognition of the pressing requirement for more environmentally sustainable alternatives. Within this particular framework, the reclamation and repurposing of Waste Fishing Trawl (WFT) fibers made from polyethylene and Waste Fishing Rope (WFR) fibers made from polypropylene emerge as a noteworthy strategy that combines environmental awareness with innovative manufacturing techniques.This study investigates the impact of polyethylene-based WFT fibers and polypropylene-based WFR fibers on the mechanical characteristics of Cementitious Composites (CC). The study sheds light on the difference in the effects of the two types of fibers on the mechanical properties of the CC. Significantly, the incorporation of these fibers elicits discernible alterations in the mechanical characteristics. The mechanical properties, particularly flexural and tensile strength, demonstrate a notable enhancement, but the compressive strength remains nearly unchanged. Additionally, an intriguing fact emerges about the porosity of the cement-based material. The present work provides evidence of an observed increase in porosity as a consequence of the inclusion of WFT and WFR fibers. When discussing the fresh state properties, the incorporation of both types of fibers led to a reduction in the workability of the cementitious matrix.

Concrete waste fines (CWF) are a major by-product of concrete recycling. Recycled coarse aggregates have already been introduced into the construction industry. However, little has been done on the utilization of the fine fraction of concrete waste. This research investigated a method of recycling CWF to produce expanded lightweight aggregate (LWA) using gypsum as a foaming agent. Further, the effects of quartz and bauxite addition on the bloating characteristics of LWA were studied by utilizing the CWF by different ratios of 25, 36, 72, and 100%. This was done to modify the chemical composition of the mixture in accordance with Riley’s ternary diagram. A physical and chemical analysis of the raw materials was conducted initially using X-ray diffraction, and inductively coupled plasma spectroscopy. A series of tests were conducted with the burning temperatures and gypsum content as experimental variables. A detailed analysis of the apparent density, water absorption, and bloating index was conducted and the microstructure of LWA particles and pore sizes were studied using optical fluorescence microscopy. The experimental results demonstrated that adding 15% of gypsum by weight to the 25% CWF mixture and a maximum heating temperature of 1200 ℃, resulted in a bloating index of 155%, an apparent density of 573 kg/m3, and a water absorption of 128 wt. %. This expansion of LWA was achieved primarily due to the gypsum acting as a bloating agent. The research confirmed the feasibility of producing high-quality LWAs by combining fine concrete waste with gypsum.

Low-carbon binders, particularly Limestone Calcined Clay Cement (LC3), are emerging as sustainable alternatives to Ordinary Portland Cement (OPC). LC3 significantly reduces CO2 emissions, offering satisfying mechanical strength, increased durability, and reduced environmental impact. Simultaneously, the traditional ceramic production process generates residual powder that could serve as a viable cement substitute. Ceramic waste materials, including scraps, waste powder, sludge, and tile residues, may exhibit pozzolanic behaviour, making them valuable in construction materials.This research investigates potential benefits and challenges of incorporating grinding powders of porcelain stoneware into low-carbon cement. The LC3 formulated with recycled ceramic was analysed and compared to reference cement containing 50% of clinker and calcined clay to limestone proportion of 2:1. Mortar rheology was investigated by flow table test at different superplasticizer dosage and the fresh material was further investigated by 1H Time Domain-Nuclear Magnetic Resonance (TD-NMR) to detect the amount of capillary water available to fluidify the mixture. Colorimetric analysis was performed to quantify the visual impact of ceramic substituents on the material. Mechanical strength at 2 days enabled to validate the suitability of industrial waste to prepare eco-friendly mortar.The results show that the particle size distribution plays a crucial role in regulating superplasticizer need to reach acceptable workability. The TD-NMR findings validated that the cement composition influences the amount of detectable capillary water. However, the assessment of mechanical strength highlighted that ceramic waste can provides comparable performance to reference material encouraging the possible integration of recycled ceramics into low-carbon cement.

The current study attempts to utilize crude urease extracted from watermelon seeds along with urea and calcium source, for the treatment of recycled concrete aggregates. The experimental program involved extraction of urease in a phosphate-EDTA buffer to ensure the stability of the active sites of the enzyme. Its activity was assessed using spectrophotometric method. Subsequently, varying concentrations of this crude urease extract were used to treat recycled concrete aggregates at different temperatures. The results indicated a significant reduction in water absorption for the treated aggregates compared to untreated ones. Furthermore, image analysis of scanning electron images revealed a notable decrease in total porosities of the treated recycled aggregates compared to their untreated counterparts. X-ray diffraction analysis confirmed the presence of calcite, vaterite and aragonite polymorphs of calcium carbonate in the precipitates produced by the activity of the urease enzyme.

The use of supplementary cementitious materials is the most common approach to reduce environmental impact of concrete production. However, the total replacement of cement is not possible because of the dramatically reduction of the mechanical properties of the concrete.The paper presents an experimental study aimed at comparing the mechanical properties (compressive, bending strength and shrinkage) of ordinary concrete with those of blended concretes (with and without steel fibres) with partial cement replacement with Limestone Calcinated Clay (LC3).The results show that the partial replacement with LC3 leads to a different development of the mechanical properties with respect to ordinary concretes. A brief discussion on the structural implications of this behaviour is also presented.

In this paper, the experimental findings on the use of Limestone Calcined Clay Cement (LC3) in the stabilization of sub-grade expansive soils are reported. The effect of LC3 on mechanical properties of subgrade soil was investigated experimentally through the soaked California Bearing Ratio (CBR), Proctor and Atterberg limits tests. The difference in the performance between LC3 and Ordinary Portland Cement (OPC) treated subgrade soils was studied for comparison purposes. The LC3 and OPC stabilizers were separately mixed with the soil in the proportions of 1%, 1.5% and 2% by dry weight of the soil. The results showed that the addition of both LC3 and OPC increased plastic limit, reduced plastic index, liquid limit and linear shrinkage of the treated soils. The Maximum Dry Density (MDD) of the soil was observed to increase with a corresponding decrease in Optimum Moisture Content (OMC) upon adding varying cement dosages. Additionally, the soaked CBR of the treated soil was observed to increase significantly with increasing cement content. The maximum CBR and MDD improvement were observed at 2% cement dosage, while OMC was reduced, hence, it could be regarded as the optimum dosage for soil stabilization. The performance between LC3 and OPC treated subgrade was quite comparable. In conclusion, LC3 was found to improve the strength and stability of subgrade soil.

Recycling concrete waste through a thermal treatment approach is a promising eco-friendly solution against CO2 emissions related to the cement industry. Various researchers have treated laboratory-produced hydrated cement fines (HCFs) at different intermediate temperatures to produce thermally reactivated cement fines (RCFs) and highlighted the recycling possibilities by recovering the essential strength-forming clinker phases. RCFs are known for their loose and porous particle morphology, which has an adverse effect on their workability and mechanical strengths. This research intends to improve the particle morphology as well as the physico-mechanical properties of RCFs with the addition of ground blast furnace slag (GBFS). 28-day hydrated cement specimens (HCS) are crushed to particle sizes of <2 mm to produce hydrated cement fines (HCFs). HCFs are treated in an electric furnace at 700 ℃ to produce thermally reactivated cement fines (RCF-700 ℃). RCF-700 ℃ (<2 mm) are replaced with 25 wt.% and 50 wt.% of GBFS. The mixtures of RCF-700 ℃ and GBFS are milled using a planetary ball mill and sieved to achieve a particle size of <250 µm. The results indicate that RCF-700 ℃ – GBFS samples show improved particle fineness, lower water demand, lower porosity and enhanced compressive strength as compared to 100% RCF-700 ℃.

Slag-blended cement is a sustainable binder for building materials. However, when slag blends are mixed with ordinary Portland cement (OPC), the initial hydration reaction takes longer time, thus limiting its use. This research focuses on the characteristics of ground-granulated blast furnace slags from various sources based on their chemical and physical properties to assess their reactivity. Furthermore, to improve its early age reactivity, a mechanical activation was performed on slags to enhance its specific surface area and particle size distribution. The hydration and crystallinity degrees were investigated with calorimetry and X-ray diffraction tests. Moreover, the slag-cement binder strength development in the initial 72 h were assessed with the help of the ultrasonic measuring device. The results showed that the mechanical treatment significantly increased the reactivity of the slag already after 24 h, leading to a higher degree of hydration and modulus of elasticity. It was observed that mechanical activation of slag was also efficient from the point of view of strength development.

Hydraulic binders are inorganic materials that harden when mixed with water and are widely used in the building industry. The conventional production process of portland cement results in significant greenhouse gas emissions.To address these environmental concerns, alternative hydraulic binders, including geopolymeric and alkaline-activated binders, have been developed. These binders offer reduced carbon dioxide emissions and are produced using materials like granulated blast furnace slags combined with an alkaline activator.Ground granulated blast furnace slags are obtained through the rapid cooling of blast furnace slag, a by-product of pig-iron production. A critical challenge with this material is the sustainability and supply limitations of blast furnace slag, which is directly linked to the production of cast iron.This strict dependency makes it challenging to meet the growing demand for raw materials in a cost-effective and sustainable manner.The paper introduces a potential solution to these issues by proposing a process to create a synthetic precursor for hydraulic binders that is independent of the pig-iron production process.This method relies on a reaction between steel slag in the molten state and silica: the resulting material rapidly quenched has a composition and characteristics similar to granulated blast furnace slag.The process has been verified at the laboratory scale with success, the key point for its industrialization is the energy balance that is evaluated through thermodynamic simulations using FactSage 8.3.

Fulfilling the ambition for maintaining global carbon neutrality, utilizing alternative low-carbon resources is becoming more essential in the design of building materials. Recently, high-volume fly ash (HVFA) cementitious materials have been gaining attention in the industry due to their low environmental impact in terms of carbon dioxide (CO2) emissions and resource efficiency. However, applications are limited because of major material-related problems, such as increasing setting time and low early strength development. This study aims to overcome the challenges in the material system by modifying HVFA mortars with clinoptilolite zeolite. The HFVA mortar designs were established using 70%, 60%, and 50% F-type fly ash. A portion of fly ash (5 and 10%) was replaced with reactive clinoptilolite zeolite. The influence of zeolite replacement on the performance of HFVA cementitious materials was evaluated by compressive strength and initial setting time. The rheological analysis assessed the impact of zeolite addition on the yield stress and thixotropy of HVFA pastes. The results show that adding clinoptilolite zeolite reduced the delay in initial setting time in HFVA mortars and increased the yield stress and thixotropy of cementitious pastes. On the other hand, incorporating zeolite into the mix resulted in a lower compressive strength than neat HFVA mortars without any zeolite. Therefore, clinoptilolite zeolite has the potential to be used as a viscosity-modified agent in HVFA cementitious materials instead of chemical admixtures.

As the supply of some traditional supplementary cementitious materials (SCMs) decreases, the necessity to study new materials to reduce the CO2 emissions of the concrete industry arises. In that context, this study investigates the new and mostly unexplored potential SCM siderite (FeCO3), an iron carbonate extracted from the Austrian Erzberg mine. For this contribution, different batches of siderite were mixed into siderite-cement binders and tested for heat of hydration, activity index, and miniature sintering potential. According to heat of hydration, siderite retards the hydration of cement, expectedly from the reaction of Fe2+ with cement. Siderite-cement mortars show a decrease in 2-day strength in the range of 37–90%, in comparison to pure cement mortars. Factors such as fineness and storage time of the siderite powder, as well as quarry differences, influence the reactivity and, consequently, the magnitude of the strength reduction. Late strength, however, can remain higher than 80%, according to past studies. Miniature sintering potential of accelerated siderite-containing binders depicts an improvement in the durability of concrete, with a 21% reduction of Ca2+ leaching. This is attributed to the consumption of portlandite by siderite to form Fe-AFm phases, preventing the Ca(OH)2 from dissolving.This investigation shows that siderite could be used as an SCM in future applications, as it can improve the durability properties of concrete while maintaining high late strengths. More evaluations need to be conducted to properly understand the hydration mechanisms. Herewith proper recommendations and optimization of cement mixtures could be estimated and implemented in the future.

The demand for sustainable construction materials is on the rise with global urbanization, demanding an intensified search for innovative solutions. This study investigates the utilization of marine dredged sediments (DS) as a supplementary cementitious material (SCM). The DS was calcined to improve its pozzolanic properties. An extensive examination of the physical, chemical, and mineralogical properties of raw and calcined DS was conducted. Subsequently the pozzolanic activity through suspension studies and paste studies were assessed. Comparative analyses with traditional cementitious materials offer crucial insights into the potential of calcined DS as a cement replacement. The calcination of DS affected its pozzolanic properties. Findings reveal that the material calcined to specific temperatures possesses pozzolanic potential comparable to that of fly ash. The compressive strength of mortar incorporating calcined DS was found to be comparable to that of fly ash-based mortar. These results underscore the viability of calcined DS as an effective cement substitute in construction applications, offering both sustainable and performance benefits.

Carbonated wollastonite is a potential novel supplementary cementitious material. Because of the limited natural reserves only industrially manufactured wollastonite, which can be produced in conventional cement kilns from limestone and a silica source, emitting 30% less CO2 than PC clinker, is of global interest. Upon carbonation, a silica-rich amorphous phase and calcite form. In blends with Portland cement, early hydration is accelerated, and the silica-rich amorphous phase shows a pozzolanic reaction. This participation in the cement hydration reactions leads to a positive contribution to compressive strength.

The notable environmental impact of Portland cement concrete manufacture is of great concern, driving the efforts towards the design of sustainable binders with reduced cement component. Here, information about the dehydration of cement pastes containing limestone and metakaolin, and the hydration characteristics of the materials obtained after heat treatment (1 h at 800 ºC), are reported. The analytical techniques used include X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and isothermal conductive calorimetry. The results showed that the dehydration of the studied cement paste fines led to the formation of clinker phases and CaO, with C2S being dominant. The increase of limestone content in cement resulted in the formation of lower amounts of clinker phases, while less CaO formed in the thermally treated paste containing metakaolin. The re-hydration process was accelerated with the increasing limestone content in cements, but it was considerably delayed in the case of the thermally treated blend with metakaolin. Re-hydration of the thermally treated fines resulted in the recovery of the hydrated phases, and it was characterized by increased formation of Ca(OH)2 and adsorption of water, as well as by the formation of C-S-H with less polymerized silicate chains, compared to the original cement paste fines.

The demand for increasingly larger quantities of locally available waste materials has led the cement industry to move away from conventional Supplementary Cementitious Materials (SCMs) and focus on other waste materials, such as recycled soda lime glass. It does not only contribute to lowering the CO2 footprint of cement, mortar and concrete, but also improves the late performance of composite blends due to its pozzolanic activity. Concerns associated with its use include increased alkali content and slow strength development at early ages. Certain activators can compensate for this behaviour, but their role in the overall hydration of the system remains to be fully clarified. In this study, sodium thiosulfate was selected as an accelerator with the aim of understanding the performance enhancement of cement-glass mixtures. The hydration of activated and non-activated mixtures was followed using isothermal calorimetry, X-ray diffraction, and thermal analysis. The compressive strengths of standard mortars were also evaluated. It was found that the values of the activated systems after 1 day were significantly better than for the non-activated system.

The complexity surrounding the cement composition due to the presence of numerous hydrates requires a multidimensional approach to bridge the existing knowledge gaps. Thermodynamic modelling provides a fast and efficient way of predicting the cement hydrates assemblages and involved reaction mechanisms with the possibility of changing factors affecting reactions such as temperature and system composition. Thermodynamic modelling is currently being used to complement experimental data and vice versa. In the current study, we explored the role of kunkur fines, sourced as quarrying waste, in ternary blended cements. Specifically, the effect of kunkur fines addition on the physico-mechanical properties and fire resistance were assessed, in comparison with OPC and LC3 cement. The ambient temperature behaviour was modelled using the GEMS software, whereas the predicted phase assemblage at high temperature (750 ℃) was obtained by the FactSage software. The results show that kunkur fines contributed to the overall cement reactivity and influenced phase assemblage, which in turn had a role in controlling the mechanical properties and behaviour at high temperature.

The use of locally sourced raw materials has the potential to reduce the environmental impact and cost of cement, especially in those locations where the supply of conventional resources for cement production, such as limestone, is based on massive import. To this aim, this study investigates the utilisation of volcanic ashes sourced in Kenya in both blended and alkali-activated cements. Quantitative X-ray powder diffraction (XRD) phase analysis of the ashes was performed in combination with XRF with the aim of evaluating the amount and chemical composition of the amorphous fraction, as an aid to the proper formulation of the alternative cement mixes. The compressive strength and degree of hydration, and compressive strength and yield stress, were tested for the blended and alkali-activated cements respectively. The results show that the volcanic ashes are characterised by a significant amount of an amorphous glassy phase. However, the relatively low Al/Si ratio of the amorphous fraction leads to different behaviours of the volcanic ashes in blended and alkali-activated cements. The high Si content activates the pozzolanic reaction in blended cements and it is observed that the mechanical properties of ternary blends based on volcanic ashes are comparable to those of control LC3 blends. With respect to the alkali-activated cements, the limited concentration of Al in the amorphous fraction of the volcanic ashes inhibits the precipitation of N-A-S-H, therefore the addition of 37 wt.% metakaolin, based on a Design-of-Experiments (DoE) approach, was found to be suitable for optimising both the mechanical performance and workability.

The roadmap to carbon neutrality of concrete provides, as one of the main actions, the partial replacement of clinker by supplementary cementitious materials (SCMs) in blended cements. Most SCMs are characterized by a much lower carbon footprint compared to clinker and therefore blended cements represent the best solution for producing concrete with low carbon content (LCC, Low Carbon Concrete). Recently, a new class of Low Carbon Concrete Admixtures (LCCAs) has been developed to compensate the loss of both early and final strength of blended cements in comparison with ordinary Portland cement (OPC). Different formulations of LCCAs have been proven to be effective in activating blended cements, some of them for improving early strength, others for enhancing final strength, or both. In the present work, a chemometric approach was used to highlight specific admixture-binder interactions aiming to identify the most effective LCCA for different blended cements. The application of Principal Component Analysis (PCA) and Design of Experiment (DoE) on datasets of compressive strength of mortars prepared with different blended cements and different LCCAs allowed to identify specific interactions related to the chemical composition of blended cements and to optimize the formulation of LCCAs for specific applications.

Looking into high education programmes across European countries reveals that training in building with bio-composites is still not sufficiently developed; teachers and students lack competence as well as knowledge and skills. Bio-composites are often neglected in civil engineering, architecture and other construction-related programmes. This gap in education and skills was the driving force behind the Erasmus + project BIO-FIBRE – Sustainable construction with bio-composite materials. Here, the project is presented, namely: the development of a methodological framework based on innovative student-centred learning approaches and improved pedagogical competence among teachers; the development of a new course contributing to increasing the use of bio-composites by educating students in sustainable construction practices with these materials; a strategy to ensure open awareness of the project’s results at the local, national, EU and transnational levels, promoting sustainable construction in higher education.

This paper reports some of the outcomes of RAPCON, a 3-year-project financed by Fondazione Cariplo in the framework of the 2019 Call “Scientific Research – Circular Economy for a Sustainable Future”. The main objectives of RAPCON project were (i) the investigation of the use of RAP (Reclaimed Asphalt Pavement) as replacement of natural aggregates in concrete to study mechanical, microstructural and durability performances of RAP-based concrete; (ii) the assessment of the expected service life of concrete with increasing RAP content and determination of relevant environmental impacts by life cycle analysis (LCA); (iii) draft proposal of an European Assessment Document (EAD) aimed at the certification procedures of RAP as aggregate for concrete.RAPCON project allowed the analysis of a complete scenario related to the use of RAP as replacement of natural aggregates for structural concrete, highlighting the advantages and limitations related to the material, environmental and cost impacts and industrialization.

In the framework of the conservation of twentieth-century heritage, the re-functionalization of the Manifattura Tabacchi in Bologna into technopole represents an opportunity to reflect on intervention strategies and materials for the preservation of concrete-based architecture. Focusing on the Fabbricato Lavorazioni, a building of the industrial complex realized by Pier Luigi Nervi during the 1950s, the paper presents structural measures that involve the use of innovative and fibre reinforced cementitious materials as a sustainable alternative to traditional strengthening interventions. The proposed structural solution involves the use of prefabricated elements made of high-performance and fibre reinforced concrete, thus ensuring an optimized use of materials. For the local shear strengthening, the use of carbon fibre reinforced polymer rods is proposed, according to the near-surface mounted technique. The presented interventions are compared with the actual steel-based design, following environmental and economic sustainability criteria including the life cycle of the materials and the cost estimation. The results show that the reinforced concrete solution is more advantageous both in economic and environmental terms. Indeed, the introduction of reinforced concrete shear walls mitigates the seismic actions on the original structure, with a consequent reduction of local interventions and the improvement of the overall sustainability.

Floating Offshore Wind Turbines (FOWTs) are designed to harness the energy produced by wind. Since these structures are in deep waters, the engineering and dynamics of steel and or concrete structural elements (floaters, chains, mooring, etc.) is important to ensure significant performance. The durability of concrete in submerged zones is affected by biological and chemical deterioration mechanisms, with the latter being controlled by transport of aggressive ions. The influence of concrete on biodiversity developing on its surface plays a significant role as it contributes to the overall environmental footprint of the structure. The aim of this experimental research was to identify the surface interactions between cementitious materials such as concrete, biofouling at their surface, and seawater on short-term exposure. CEM III concrete specimens were submerged at a depth of 27m at SOLA station, Banyuls-sur-mer, France. The microstructural and chemical changes in the cementitious material were analysed with scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) and electron probe micro analysis (EPMA). The results of SEM-EDS analysis showed the formation of three zones, namely, magnesium-rich, sulfur-rich, and chloride-rich zones. Using Environmental DNA analysis, bacterial diversity was identified, revealing high abundances of alphaproteobacteria and gammaproteobacteria, and 18s rRNA sequencing unveiling a diverse eukaryotic community.

Advancing towards a circular economy necessitates the efficient reuse and maintenance of structural materials, which relies on accurate, non-damaging condition assessments. This paper introduces an innovative AI-driven adaptive sampling (AS) technique integrated with Non-Destructive Testing (NDT) to optimize this process. AS focuses on critical data points, reducing the amount of data needed for precise assessments—evidenced by our method requiring on average only 7 samples for Logistic Regression and 8 for Random Forest, contrasted with 29 for traditional sampling.By reducing the necessity for extensive data collection, our method not only streamlines the assessment process but also significantly contributes to the sustainability goals of the circular economy. These goals include resource efficiency, waste reduction, and material reuse. Efficient condition assessments promote infrastructure longevity, reducing the need for new materials and the associated environmental impact.The circular economy aims to create a sustainable system where resources are reused, and waste is minimized. This is achieved by extending the lifecycle of materials, reducing the environmental footprint, and promoting recycling and reuse. Longevity directly contributes to the circular economy by maximizing the utility and lifespan of existing materials and structures. Longer-lasting infrastructure means fewer resources are needed for repairs or replacements, leading to reduced material consumption and waste generation. This aligns with the circular economy's principles of sustainability and resource efficiency. This research not only advances the field of structural health monitoring but also aligns with the broader objective of enhancing sustainable construction practices within the circular economy framework.

The rapid population growth in Africa calls for an enormous increase in buildings both in urban and rural areas. This will dramatically increase the carbon emissions in Africa, particularly when not specific considerations are made with regard to the high level of informality in many urban African settlements and in the overall construction sector. After elaborating on the high climate impact of the informal African construction sector, the authors discuss some major differences and how structures and quarters would need to be designed to become sustainable, and materials concepts are presented that are sustainable even in a rapid urban growth situation as foreseeable in Africa, where whole city quarters will change their surface appearance inevitably within short cycles. A prediction for the example of Kenya is made on how much CO2 emissions can be reduced until 2050, when informal businesses are included or excluded in policies and technology developments for low carbon construction. The conclusions for longevity of urban settlements are that flexible and modular structures are better than efficiency optimised buildings, and that there is no alternative to multi-storey buildings, which, however, have to stay limited in height to avoid wasteful materials use. The vertical growth is also required to create social spaces, which are important for quarters to be safe from gentrification. Materials should be ideally fully reusable or renewable, hence, structural elements are best build from cementitious materials in a modular column, girder, slab system.

Over the last years, increasing awareness of the alarming proximity to critical climate tipping points is spreading, along with the knowledge that implications for the whole humanity would be exacerbated in case these limits are overcome. Thus, a series of international actions that also involve a rethinking of traditional steps for design, maintenance and dismantling in civil engineering applications initiated. One of the most demanding targets is to include environmental assessment of a structure already in the design phase to equate sustainability with other driving parameters, as e.g., economic benefits. Reduction of environmental impact cannot be reduced to a mere calculation, but it should be exploited for seeking new structural solutions in a comprehensive scenario. In such scenario, a composite slab made by concrete and engineered timber (Timber Concrete Composite, TCC) is a valuable answer to decrease environmental impact of such horizontal element, improving its rigidity, stiffness, and load-bearing capacity. In this context, a broad outlook supports a specific focus on uncertainties that may affect Life-Cycle Assessment (LCA) results: evaluation of multiple scenarios is the key to smooth uncertain data pertaining service life or End-of-Life events. Assessment of multiple scenarios allows for consideration of burdens and benefits currently treated as non-standard option, as e.g., mixed End-of-Life scenario exploiting both timber and concrete carbon capture inborn ability. In this way, the composite slab is used as concrete layer optimizer since the rationale behind this research pursues minimization of materials quantities through achievement of maximum environmental and structural performances. To deliver robust results, two sets of potential solutions are analzyed, characterised by the same bearing capacity or the same span, respectively.

Among the main actions to a net concrete zero future, saving in cement and binders by replacement of clinker with supplementary cementitious materials (SCMs) is considered a major task. Nevertheless, it is well known that SCMs react slower compared to clinker and can negatively affect the strength development, both at early and long curing times. Moreover, clinker itself never hydrates completely and residual unreacted fractions always remain in concrete. Under such premises, the expected reduction of the clinker-to-cement ratio from the actual value of 0.71 to the target value of 0.57 by 2050 might be hardly achievable. Low Carbon Concrete Admixtures (LCCAs) is a new class of admixtures that comes alongside the existing water reducers, retarders and accelerators and it is destined to take on a prominent role as an essential integration for the sustainability of concrete. LCCAs increase the degree of hydration (DoH) of cements and compensate the decline of both early and final strength of blended cements compared to Portland cements, assuring a more rationale use of cement. LCCAs permit to achieve the same compressive strength with reduced dosage of cement. Moreover, by using LCCAs it is possible to increase the fraction of SCMs in blended cements and in concrete without detrimental effects on compressive strength. In the present work, an introduction to the new class of LCCAs is presented with examples how they can effectively play a fundamental role to reduce the carbon foot-printing of concrete in the view of the Net Zero 2050 Scenario.

Low Carbon Concrete Admixtures (LCCAs) are the newest class of admixtures developed for reducing the carbon footprint and improving the sustainability of concrete. Their formulation involves multiple chemicals for enhancing the degree of hydration (DoH) and the compressive strength of cementitious binders at both early and longer curing times. In the present work, the fundamentals of LCCAs are disclosed. Secondary nucleation, augmented pozzolanic reaction, enhanced silicate and aluminate phases dissolution and limestone trigger are the levers which, separately or synergistically, determine the LCCAs effectiveness with blended cements. The mechanism of each controlling factor has been described by the review of the previous literature and studied by the execution of new experimental tests and a statistical analysis approach. Experimental measurements include time resolved XRD hydration kinetics and compressive strength testing of mortars with and without LCCAs. The wide range of chemical-physical processes involved and the possibility to combine the different ingredients in various proportions offer the possibility to formulate a range of products specifically designed for blended cements, which are believed to further expand both in number and composition in the coming years.

The use of Recycled Fine Aggregate (RFA) combined with limestone calcined clay cement (LC3) shows a potential to reduce the environmental impacts of the ordinary Portland cement (OPC) production process, while also providing a viable alternative to the depletion of natural resources for building materials. This study was carried out to examine the mechanical and physical properties of LC3–based mortar integrated with high dosages of recycled fine aggregates. An affordable, eco-friendly, and sustainable alternative binder has been prepared by substituting 50 wt% of the clinker in CEM I with a blend of calcined clay (CC) and limestone (LS) powder with CC:LS of 2:1 in mass. The mortar was produced with RFA from construction and demolition waste as a substitute for natural sand with different replacement ratios of 50 vol% and 100 vol%. The fresh state behaviour of mortars was evaluated by the flow table test. The 28-days mechanical properties (compressive strength) were evaluated, and similarly, water absorption, capillary water absorption rate, and porosity were investigated after 28 days of curing for the durability assessment. The LC3 binder showed better mechanical strength than CEM II at all levels of fine aggregate replacement and improved the 28-days compressive strength by 12% for natural sand, 9% for 50% RFA, and 23% for 100% RFA, respectively. Similarly, the LC3 binder compensates negative impact of recycled sand porosity and reduces the capillary water absorption coefficient by 39, 47, and 42% for natural sand, 50%, and 100% RFA respectively. Employment of LC3 binder with RFA for the production of mortar with superior mechanical properties is useful for the reduction of environmental depletion and waste management.

Low-carbon building materials, such as earth- and bio-based ones, have an excellent capacity to regulate indoor moisture levels. Thanks to their hygroscopic nature, they can buffer moisture from the indoor environment, absorbing it when humidity increases and releasing it when the air becomes drier. This moisture-buffering capacity can significantly improve indoor comfort and well-being. However, the extent of this benefit depends on factors like building usage, occupancy, ventilation rates, and external climate conditions. Thus, dynamic numerical simulations are often necessary to quantify the materials’ benefits considering specific building scenarios.This paper investigates incorporating moisture dynamics evaluation into early architectural design workflows using the Grasshopper interface of Rhinoceros. This integration offers an advancement beyond conventional building performance simulations provided by current Grasshopper plugins. The paper explores the effectiveness of the newly developed WaterSkater plugin in assessing the hygrometric benefits of using moisture-buffering materials in architecture. This study represents the first application of the plugin, with future studies planned to validate its accuracy and correctness.The plugin discussed in this study allows for integrating materials’ moisture buffering capacity into early-stage architectural design workflows. This step enables designers to strategically select materials that align not only with sustainability objectives and desired U-values but also understand their potential for indoor humidity regulation. The presented plugin enables the incorporation of low-carbon, moisture-buffering materials from the early stages of building design, allowing for a strategic use of their moisture-regulating potential to improve indoor comfort and reduce the need for ventilation and humidity-control mechanical systems.

This study explores the effects of replacing up to 30% of ground granulated blast furnace slag with recycled concrete fines (RCF), a secondary fine powder waste (<63 µm) from recycled concrete aggregate production, while maintaining a 50% cement replacement ratio. A limestone-slag cement benchmark group with 10% slag replaced by limestone powder was also prepared. The results indicate that the incorporation of RCF can enhance the early-age hydration reactions. Isothermal calorimetry results show a notable increase in heat release and emergency of a distinct secondary aluminate peak with the increased RCF fraction, while this is not observed in limestone-slag cement. This could be attributed to the presence of additional gypsum and calcium carbonate phases in RCF. XRD results reveal that a formation of Hemicarboaluminate (Hc) was already presented at 1 day in RCF blends. TGA results indicated an increased chemically bounded water content yet reduced portlandite content in RCF blended paste at 1 day, which confirmed RCF’s synergetic acceleration effect on slag early reaction. The initial setting time of slag-blended cement was significantly advanced from 446 min to 163 min by replacing up to 30% slag with RCF. This research proves that the incorporation of RCF can be a promising method to overcome the prolonged setting time and inefficient slag use issue in the high slag volume binder system.

In recent years, various waste recycling strategies have emerged emphasizing the utilization of plastic waste in concrete mixtures. This practice offers a dual advantage by decreasing the demand for traditional aggregates, like sand and gravel, or lightweight aggregates while mitigating plastic accumulation in landfills and oceans, promoting a circular economy. Although high plastic content may worsen mechanical characteristics, proper mix designs can optimize concrete containing plastic aggregates to be lighter and beneficial for weight-sensitive applications.This study investigates the influence of plastic waste on concrete mechanical characteristics, incorporating different types of plastic waste in varying percentages to identify potential applications. Experimental results indicate that incorporating plastic waste does not significantly compromise concrete strength. Despite promising findings, challenges associated with using plastic waste in concrete must be addressed to optimize this practice and overcome drawbacks. These efforts align with sustainable waste management and eco-friendly construction practices, underscoring the importance of refining the use of plastic waste in concrete.

The quality of concrete is strongly dependent on the curing process. Environmental changes in temperature and relative humidity can result in premature drying, which in turn can cause cracking on the surface of the material. Hence, monitoring the concrete curing is essential to prevent undesirable behavior. Techniques such as Acoustic Emission (AE) have proven very promising for monitoring the curing of cement-based materials due to their high sensitivity level. Shrinkage cracking can be mitigated using admixtures such as SuperAbsorbent Polymers (SAPs) which provide internal curing for several hours after casting by releasing entrained mixing water back into the concrete matrix. This action taking place in the microstructure, although beneficial, is difficult to monitor or control. However, recently it was shown that release of SAP water into the cementitious matrix is accompanied by high AE recordings enabling, therefore, the monitoring of the process. This paper discusses the possibility of controlling the internal curing of concrete based on real-time AE data in order to ensure the desired concrete performance. The results showed that by applying a curing agent on the concrete surface, at the moments dictated by the increase of AE, the SAP activity is postponed. This indicates that their action can be deactivated and reactivated multiple times during curing, resulting in prolonged internal curing and thus, better hydration. The mechanical properties are also investigated, showing an increase in the compressive strength for the actively controlled SAP specimens.

Water is the most precious resource in the world. It is fundamental for basic human needs, economic growth, and sustainable development. Unlike carbon-related impacts, water-related impacts are local. Therefore, local water inventories are needed. In this study, the water consumption per cubic meter of concrete produced in Panama is estimated based on primary data from the industry. The technological routes for concrete production in Panama are described with a focus on water use based on 20 technical visits. The specific water consumption (L/m3) during 2022 is estimated for 11 concrete plants. Different concrete production practices, such as covering the aggregates, spraying the aggregates with water, and using cold water and ice for temperature control of the concrete mix, were observed. Most of the water use comes from the public water network and groundwater. However, in some cases, harvested rainwater and recycled water are implemented as water sources. The preliminary results show that the water consumption ranges from 189.88 to 641.84 L/m3. Through rainwater harvesting, water recycling, and covering of the aggregates, the water consumption from the public network and groundwater is reduced, which, in turn, decreases energy consumption, especially for groundwater extraction. This is an example of the water–energy nexus that could contribute to the carbon footprint. On the other hand, the aggregate spray process could increase water consumption, even more so when aggregates are not indoors and when sprinkling is not controlled. Furthermore, a standard water accounting methodology should be implemented to help achieve water-reduction strategies.

The prevention of moisture related damages in construction is extremely important to ensure the durability of buildings, to save resources in their management and to ensure safe and healthy environments for occupants. The assessment of the internal hygrothermal conditions of construction elements using real time monitoring is a powerful strategy to prevent them and can yield profound insights into the dynamics of each individual case examined. However, it is crucial to identify reliable sensors and installation strategies. The use of capacitive and resistive sensors is a prevalent approach; however, it is not without challenges. Drilling into the stratigraphy to place these sensors requires boreholes, which not only potentially alter the measurements but may also be impractical, both in existing buildings and new constructions. The ideal scenario is to integrate sensors during the construction or retrofitting phase to obtain reliable data but also in this case a careful planning and a correct selection of the sensors is needed. This study investigates these challenges in a controlled environment using a double climatic chamber and a real-scale timber frame façade that integrates a moisture-adaptive membrane on one side and a bituminous membrane on the other side to reproduce the stratigraphy of a flat roof. Different type of sensors as well as different installation approaches (including before and after assembly) are used and assessed. This research presents a new method for installing sensors after assembly. When applied precisely, the approach generates accurate sensor data comparable to pre-installed sensors. However, rapid changes in humidity can cause a decline in accuracy, and it’s important to restore the structure’s airtightness when mounting sensors in existing structures to ensure reliable data collection.

The integration of construction demolition waste (CDW) as a supplementary cementitious material presents a promising avenue to mitigate the environmental impact of concrete production by reducing clinker content. Notably, in some areas, up to 50% of CDW are brick residues, highlighting the substantial potential impact of incorporating these wastes into construction practices. This study specifically focuses on optimizing cementitious mixtures by partially replacing ordinary Portland cement (OPC) with recycled brick powder (RB). Different mix designs, with RB replacement spanning from 10 to 90%, are analyzed through rheology (i.e., small amplitude oscillatory shear or SAOS), isothermal calorimetry, and mechanical testing. An equal workability of each mix design is ensured through the use of a superplasticizer. Results from rheology and calorimetry show satisfactory cohesion and heat evolution for RB content up to 70%. At this high substitution level with only 30% of OPC, the 28-day compressive strength still reached 16 MPa. Mechanical testing on OPC/RB mortar shows satisfactory results, particularly for OPC replacement up to 50% with a compressive strength higher than 30 MPa after 28 days. A life cycle assessment (LCA) focusing on global warming potential (GWP) is conducted to quantify the potential environmental improvement of the optimized binder mixtures during the production stage. This combined methodology is promising for the development of environmentally friendly construction materials.

The cement industry is working towards CO2 cuts in clinker production, and ferrite-rich cement could be a solution. When compared to OPC cement, ferrite-rich cement requires less calcium, lower clinkering temperature and enables valorization of iron rich residues to a higher extent. Here, we utilize a novel Electric Arc Furnace (EAF) slag originating from new direct reduced iron ore (DRI) process route used in steel manufacture. The DRI process is an emerging low CO2 production pathway that employs hydrogen in the direct reduction of iron ore. This new process route is intended to replace conventional blast furnaces in some parts of the world in the near future. In this study, 18.9% of this slag was used as the clinker feedstock (with other materials) with the aim to increase the ferrite phase (26.4 wt.%) in the clinker. The clinkering was done at 1400 ºC and the clinker was rapidly cooled, the phase composition of the clinker was analysed through X-ray diffraction. Iron rich phases in cement, such as ferrite (also known as brownmillerite), typically have poor hydraulic properties, to enhance their hydration, triisopropanolamine (TIPA) at two different dosages (low and high) were added in the cement and hydrated. The effect of this dosages on the ferrite hydration were then studied via isothermal calorimetry, X-ray diffraction (XRD), and thermogravimetry analysis (TGA). Results shows the potential of valorising this slag as a feedstock in cement clinker, and the reactivity of the increased ferrite phase can be improved with the addition of TIPA during hydration.

Concrete is, as a matter of fact, the only construction material able to globally meet the growing demand for new structures and infrastructure. Hence, CO2 emissions related to the construction sector, mainly attributable to Ordinary Portland Cement (OPC), are expected to increase. Rapid and effective solutions are needed to meet future demands sustainably and achieve carbon neutrality by 2050. Among these, reducing clinker in cement and reducing cement in concrete are considered the most promising and ready-to-use. Limestone Calcined Clay Cement (LC3) is widely recognised as the most feasible blended cement addressing the former. Whereas the latter is currently prevented by the requirement of a minimum binder content in concrete in most existing prescriptive-based Standards. This work aims to minimize the CO2 emissions of standard-compliant structural concretes by suggesting a low-carbon and low-binder concrete design, thus providing evidence for an update of prescriptive codes. LC3 concrete mixes were designed to reduce the clinker content by up to -75% and binder content to 250 kg/m3 while targeting normal-use strength classes (C25/30, C30/37). The mechanical and durability properties of the low-binder LC3 mixes were compared to equivalent OPC mixes designed according to European codes. A life cycle analysis highlighted the CO2 reduction potential of the new systems while ensuring good mechanical properties and improved resistance to chloride penetration. Imposing a minimum cement content resulted in a conservative approach leading to overconsumption of cement (+30 to +70 kg/m3) and higher CO2 emissions (+45%) compared to an efficient mix design of blended cement concrete.

Road infrastructures maintenance is one of the trend topics of the last years. Road transport is the principal mode of inland passenger travel in Europe and often their management and maintenance systems are dated. InfraROB is a European Union’s Horizon 2020 fonded project (09/2021–02/2025) which aims (among the others) to increase the availability of the transport network, to reduce the cost of the repetitive tasks and to upgrade the maintenance system of the road infrastructures. InfraROB entails advancement across different, but strictly interrelated, technological areas. Nuova Tesi System is involved in the development of an all-in-one multi-functional precast concrete element applicable as roadside safety/restraint system and as road construction element at the same time, but also in tests on new solutions for road maintenance exploiting Fiber Optic Sensors (FOS) technology for asphalt-paved roads. The sensors, embedded in the asphalt, can monitor parameters as strain and temperature along the stretch of interest (up to 2 km) with a resolution of 1 cm, using the Rayleigh scattering. Extensive test campaign (in both laboratory and real scale) inspected FOS parameter and performance, highlighting a 100% success rate in surviving to asphalt realization process and the capability of detecting residual stress during the pavement realization. The obtained results confirm the technology’s potential to revolutionize road maintenance.

Heritage structures, such as ancient buildings, monuments and artifacts are important cultural treasures that provide a glimpse into our rich history and cultural heritage. They represent our past, and their conservation is crucial to preserve our cultural identity for future generations. This paper focuses on safeguarding heritage structures by addressing key challenges in marble stone conservation. We have investigated the potential impact arising from simulated accelerated salt weathering, scrutinized the corrosive outcomes of artificially induced accelerated acid tests, and analysed the consequences of heat attacks on the marble stones. These findings underscore the need for stone-specific conservation strategies. Further the study investigates the effectiveness of basically three distinct consolidative compounds—Tetraethyl orthosilicate (TEOS), diammonium hydrogen phosphate (DAP), and ammonium oxalate solutions, and further the efficacy is assessed through integration of scanning electron microscopy (SEM) and petrography studies to comprehensively evaluate the impact of these compounds on marble structures. The insights gained hold practical implications for heritage preservation practices, with identified areas for future exploration.

Commercial plasters have found widespread use in the conservation of building heritage. Their use has been encouraged by the important advantages they offer, such as consistent product quality and the easy application. On the other hand, it is not possible to know all the components of the mixtures, as current regulations do not require a detailed declaration of the product’s composition. Among these materials, it has become common to find mixtures with a green label. These products are increasingly present on the market, especially since the introduction of the 2030 Agenda for Sustainable Development, which proposes a global approach to the production system that pays attention not only to the economic aspects of the production process, but also to the social and environmental ones. These materials are labelled green when the raw materials, their extraction and processing ensure a lower environmental impact than common industrial methods and should not contain substances considered harmful to humans, animals and the environment. The sustainability of materials can then be confirmed by specific declarations standardized (such as Environmental Product Declarations - EPDs), by national or international certification protocols or, in some cases, their sustainability is declared by the supplier without any document attesting to it.In this work, the environmental performance of a selection of ready-mixed, green-labelled plasters will be investigated. The evaluation will be carried out on the basis of the companies’ declared information. The aim is to assess whether this type of material guarantees an advantage in environmental terms. A comparison of the data provided by the EPDs of a selection of commercial plasters is therefore proposed.

When exposed to fire, the strength and stiffness of steel reduce significantly. Being it highly conductive, the exposure of steel structural members to fire results in sudden temperature rises, which trigger a significant strength and stiffness decay in a short time, above all in the case of thin steel plates. Therefore, passive protective systems are generally adopted to prevent structural collapse. In the perspective of consistently adopting the performance-based approach, the thermo-mechanical analysis cannot disregard the variability of the thermal conductivity of such protective materials with temperature. Aiming to identify the relationship between thermal conductivity and temperature, recently, at the University of Naples, framed in the project PROSYSSIF, a methodology combining experimental evidence and numerical modelling has been developed for a commercial spray-applied fire-resistant plaster. The latter, applied on steel elements, are tested in transient and stationary heat flux conditions, along with an extensive chemo-physical characterisation at increasing temperatures. Afterwards, the experimental results are used to calibrate the Multiphysics-Lattice Discrete Particle Model, which simulates the moisture and heat transport phenomena occurring within the plaster. Then, the model is used to realise a parametric study, in which three design parameters (i.e., the thickness of the protective layer, input heat flux, and steel section factor) are analysed to quantify their effect on the protective material performance and to derive meaningful insights on its practical applications. The relationship between the thermal conductivity and the temperature is eventually implemented into an FE-based structural model to compare a benchmark structure's unprotected and protected response against natural fire scenarios.

Ultra-high performance concrete (UHPC) is widely used in retrofitting damaged structures, but few studies on the strengthening of stone arch bridges have been reported. This paper presents a simplified analysis method and its application in a damaged stone arch bridge strengthened by using UHPC. Based on the limit analysis method, the collapse mechanisms and load collapse multipliers of Qixingguan Bridge (20 m span heavy load traffic solid belly stone arch bridge) strengthened with UHPC were analyzed, considering good interface bonding and interface debonding between the UHPC layer and the stone substrate. Four UHPC strengthening configurations, including intrados, extrados, wrapping for three sides and for four sides configurations were discussed. The analyses performed indicate that from the perspective of safety, the scheme of adding 12 cm thick UHPC at the intrados of the original arch ring and 10 thick UHPC layer on both sides can be adopted. The construction method of applying UHPC strengthening arch bridge can be referred to the traditional method of increasing the cross-section. The operation condition of the strengthened stone arch bridge is good, which reveals a promising prospect in strengthening existing stone arch bridges with UHPC.

In order to reduce the environmental impact of the construction industry, retrofitting/strengthening of existing buildings should be preferred to demolition and re-construction. In most cases, retrofitting should not significantly alter the geometry and aspect of the member and at the same time increase its strength and/or stiffness. For buildings including timber structural members, specific techniques are needed to reach these goals. Within this context, the near surface mounted (NSM) strengthening technique is a possible solution to strengthen timber members without changing their aspect/geometry. This technique consists of bonding a reinforcing profile into a groove cut within the member surface. Often, reinforcing profiles are made of fiber-reinforced polymer (FRP) composites bonded with epoxy resin, since they have a high strength-to-weight ratio and do not suffer from corrosion.In this paper, an experimental campaign is conducted to study the bending behavior of timber beams strengthened with NSM carbon FRP (CFRP) plates applied with an epoxy resin. Four direct-shear tests are first conducted on CFRP-timber joints. Peak loads and interfacial slips are obtained. Then, three three-point bending tests are performed to assess the bending capacity of the strengthened members. Load-deflection curve, peak load, and failure mode of the specimens are provided and discussed.

Infrastructures have a strategic role for the societal development, making it possible to move thousands of people and tons of freight that everyday needs to reach their target destinations. Considering all the structural typologies involved in the infrastructure network, tunnels can be considered among the most critical. Dealing with the Italian infrastructure network, most of the tunnels need maintenance interventions to restore their service life, having been built, in their largest share, not later than fifty years ago. To this purpose, in an era of rapid urbanization and growing environmental concerns, an important advancement must be done in the tunnel retrofitting technology, by speeding up the overall process reducing costs and time, as well as increasing the sustainability of the interventions, by reducing the CO2 emissions and by improving the waste management. A new methodology for the regeneration of existing tunnels by means of an automated process based on slip-forming fast strength gain Steel Fiber Reinforced Concrete (SFRC) has been recently proposed. The present work focuses on the comparison between this new retrofitting methodology and the traditional approach, with the use of ordinary steel rebars in the latter, highlighting the differences in the design, material properties and construction phases. The comparison made between the two approaches is referred to a specific case of study, the Ragnaia II tunnel in the A1 highway in the Italian roadway network, and has been performed through a cradle-to-gate Life Cycle Analysis (LCA), with particular concern on the Global Warming Potential (GWP) indicator. An additional analysis explores the influence environmental and socioeconomical influence of reduced traffic congestions, emphasizing dependence on the construction duration and highlighting the importance of extending the system boundaries beyond the gate.