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Geopolymers represent a distinct class of materials characterised by their X-ray amorphous nature and nanoporous, nanoparticulate structure. Geopolymers can be conveniently mixed, poured, and cured under ambient conditions. This makes this class of materials an interesting alternative to ordinary Portland cement for structural processes. Additionally, the addition of alumina can improve mechanical properties, while the addition of glass can form an impermeable glaze which could be useful for molten salt containment. Therefore, in this investigation, potassium metakaolin-based geopolymer composites with varying proportions of glass particles and alumina platelets were fabricated, cured, heat-treated, and analyzed to study the effects of composition on material properties. Various attributes including rheological properties, densities, mass loss, shrinkage, and porosities were compared. It was observed that certain compositions exhibited high viscosities, making high shear mixing challenging, while also displaying significant permeability that would hinder their ability to contain liquids without leakage. Additionally, certain samples showed reduced densities, suggesting potentially weaker mechanical properties; however, the investigation did not include a direct assessment of mechanical properties. The most promising candidates for containing liquids at high temperature contained 50 wt% KGP, 25 or 35 wt% glass powder, and 25 or 15 wt% alumina platelets, respectively. ASH-G slurries required a minimum of 65 vol% KGP to produce a homogenous material compatible with additive manufacturing. The minimum amount of glass phase to form surface glazes was 16 vol%. Only samples containing more glass phase than alumina phase produced glazed composites. [ABSTRACT FROM AUTHOR]

This research investigates the structural performance and failure mechanisms of beam‐column joints reinforced with aramid fiber‐reinforced polymer to bolster the durability and seismic resilience of concrete structures. It meticulously selects and proportions materials such as ordinary Portland cement Grade 53 cement, fine and coarse aggregates meeting IS: 383–1970 standards, and water conforming to IS: 456–2000 specifications. Tests confirm the high quality of ordinary Portland cement, crucial for optimal beam‐column joint performance, while carbon fiber‐reinforced polymer enhances structural integrity with its lightweight composition and substantial tensile strength (3800 MPa–4200 MPa). Failure analysis reveals that non‐aramid fiber reinforced polymer wrapped beam‐column joint specimens predominantly failed due to concrete crushing, whereas aramid fiber‐reinforced polymer‐wrapped specimens failed due to fracture in the aramid fiber‐reinforced polymer composite, emphasizing stress concentration areas. This study underscores the pivotal role of stress distribution in failure mechanisms and underscores the significance of robust reinforcement design in bolstering structural resilience. These insights advance retrofitting strategies and reinforce techniques aimed at enhancing the longevity and seismic resistance of concrete structures. [ABSTRACT FROM AUTHOR]

Production of Portland cement consumes a huge amount of silica mineral. The present work aims to introduce desert sand to replace the natural mineral to achieve green manufacturing of silicate cement clinker, as well as further decreasing the synthesis temperature and increasing the production efficiency. The effects of desert sand, industrial quartz and high‐purity quartz as raw materials, and Al2O3 and Fe2O3 as additives on phase transformation and microstructure of calcium silicate powder were comparably investigated using X‐ray diffractometer, differential scanning calorimeter, and scanning electron microscopy. Results show that the main phases of all samples with different raw materials and additives were 3CaO·SiO2 (C3S) and 2CaO·SiO2 (C2S). In which, the samples prepared using desert sand had the lowest phase transformation temperature for C2S and C3S. When adding Al2O3 and Fe2O3, the phase transformation temperatures of C2S and C3S further decreased, which were 1032.5°C and 1270.9°C, respectively, meanwhile phase content reached the maximum (C2S of 65.6 wt.% and C3S of 61.2 wt.%). In addition, the most uniformly and finely distributed crystalline phases formed at an optimal calcination temperature of 1350°C. This is beneficial for reducing production costs, saving mineral resources, and promoting the sustainable development of the cement industry. [ABSTRACT FROM AUTHOR]

Polycarboxylate ether (PCE) superplasticisers have been widely used in cement formulations. However, it is not until recently that several studies have analysed the relationship between the properties and the molecular structure. In the present work, PCEs with different side chain lengths and charge densities synthesised through free radical copolymerisation are used to analyse the effect they have on the hydration of ordinary Portland cement (OPC). It was found that the addition method of these PCEs to the OPC significantly affects the hydration kinetics of the cement paste. When PCEs are added through the direct addition method, a linear dependency between the retardation of hydration and the microstructure of the used PCEs is observed. On the contrary, when PCEs are added through the delayed addition method (PCEs are added to the cement paste 5 min after water), no retardation in hydration is observed, but the rate of hydration is reduced. [ABSTRACT FROM AUTHOR]

Artificial cementation of granular soils results in improved stabilization, increased stiffness, and greater mechanical strength. The porosity index and volumetric cement content η / C i v a is presented as a key measure to study the evolution of different soil stabilization types. However, this index had not been previously studied or adjusted for sands in Colombia. Therefore, this study evaluates the applicability of the η / C i v a index on unconfined compressive strength (q u ) and stiffness ( G o ), complemented by microstructural analysis, in four sandy soils from Luruaco (Atlántico), Lorica (Córdoba), Medellín (Antioquia), and Bogotá D.C. The soils were stabilized with Type III Portland cement in dosages of 3%, 5%, 7%, and 9%, and subjected to UCS, ultrasound, and SEM-EDS tests after a curing period of 7 days. It was found that increasing cement content results in higher q u values for the samples, and higher molding density also leads to higher q u values. Additionally, the grain size distribution influenced the adjustment of parameter "a". In the sands from Bogotá and Lorica, with high uniformity, the value of "a" was 1.00. In contrast, mineralogy and particle shape played a predominant role in the sands from Medellín and Luruaco, where the coefficient of uniformity is higher, suggesting a possible inverse relationship between particle angularity and the value of "a". [ABSTRACT FROM AUTHOR]

In tunnel construction, grouting is frequently used to decrease the permeability and increase the rock mass strength. One of the most challenging steps in grouting is choosing the best grout type to achieve the highest penetration and sealing efficiency in the joints. The main purpose of this study is to investigate the sealing efficiency of different grout types in the joints of a high-risk section of the Kerman water conveyance tunnel (KWCT). For this purpose, the penetrations of three types of grouts including Ordinary Portland Cement (OPC), Ultra-Fine Cement (UFC), and silica sol were determined using analytical equations. Thereafter, the sealing efficiency of each type of grout in joints with different apertures was calculated. Also, the penetration radius of each type of grout was simulated and calculated using UDEC code. Based on the results of the analytical equations, by performing the grouting for 20 min using silica sol-based grout, the joints of the high-risk section of the KWCT with apertures of 0.5–2.5 mm and 2.5–10 mm can be sealed at 'Fair' and 'Excellent' levels, respectively. Furthermore, based on the results of numerical simulations, the UFC and silica sol-based grouts can seal the joints in 'Good' and 'Excellent' levels, respectively. [ABSTRACT FROM AUTHOR]

Compressive strength models for ordinary portland cement composites are typically deterministic and rely on parameters such as water-to-cement ratio, porosity, and chemical composition. While these models can estimate compressive strength, they often lack the ability to quantify uncertainty in their predictions. Various factors contribute to this uncertainty, including diverse testing protocols, limited data, overly complex mathematical formulations, and constraints in capturing the variability of the phenomenon through model parameters. This study introduces a comparative evaluation of representative compressive strength–porosity models for cement paste, adopting a probabilistic perspective and using data from various testing protocols found in the literature. Experimental data encompassing compressive strength and porosity, spanning porosity values from 1% to 30%, were gathered from hot-pressed and conventionally cast specimens. Results were obtained following the Bayesian Analysis Reporting Guidelines (BARG) with combined decision criteria using a 95% High Posterior Density (HPD) interval and the Range of Practical Equivalence (ROPE). A probabilistic version of Ryshkewitch's model emerges as the most plausible based on porosity data. These results hold promise for integration into risk analysis and decision-making tailored for structural analysis and design. Ultimately, this research contributes insights into enhancing the reliability of compressive strength predictions for cement composites by accounting for the inherent uncertainty of the underlying models. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of chitosan addition on mortar performance during sulfuric acid attack. Twenty-four mortars were prepared using Brazilian portland cements, varying traces, and chitosan dosages ranging from 0% to 3%. Mortar expansion tests were performed to evaluate sulfuric acid attack resistance. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) were performed to evaluate the morphology, XDR was performed to confirm the FTIR results. Chemical structure and bending (3 points) and compressive tests were conducted to evaluate mechanical properties. The study demonstrated that mechanical properties as well the sulfuric acid-attack resistance are sensitive to the biopolymer incorporation, with noticeable effects even at low concentrations, 1% chitosan improves bending strength for CP V-ARI and CP V-ARI-RS in trace A, but decreases it for all cements in trace B, an outcome reflected in SEM images. FTIR results reveal lower levels of gypsum and ettringite formation in mortars with added biopolymer, except for CP V-ARI-RS. Tests on mortar expansion demonstrate that chitosan enhances sulfuric acid attack resistance by reducing mortar expansion by up to 60%. Practical Applications: The degradation of cement-based materials due to sulfuric acid-attack is a significant issue, as it leads to the formation of expansive products that progressively weaken concrete structures and increase its vulnerability to penetration by other substances. This research aims to investigate the impact of incorporating chitosan, a biopolymer, into mortar prisms in terms of sulfuric acid resistance. The study examines changes in mechanical properties, alterations in material structure, and the performance of mortars with and without chitosan when exposed to sulfuric acid attack. Findings indicate that both mechanical properties and resistance against sulfuric acid deterioration are influenced by the addition of biopolymer and chitosan enhances protection from sulfuric acid attack by reducing mortar expansion. This research has application on concrete structures subject to sulfate attacks present on soil and water. So, reservoirs, sewage treatment plants and pipes are some of the practical applications of this study. [ABSTRACT FROM AUTHOR]

High-ferrite cement (HFC) has attracted widespread attention due to its advantages, such as low sintering temperature and excellent corrosion resistance. The application of Cu-containing waste in HFC will promote the cement industry toward low-carbon and sustainable development. However, massive amounts of CuO can cause a delay in HFC hydration. The main aim of this paper was to investigate the retardation mechanism of CuO on the hydration of HFC using X-ray diffraction, mercury intrusion porosimetry, isothermal heat-conduction calorimetry, scanning electron microscopy, inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis and derivative thermogravimetry, among others. The results showed that compared with the undoped clinker, the maximum heat release peak of the clinker doped with 1.5% by weight of CuO was delayed for about 60 h, the hydration induction period was extended from 37 to 89 h, and the compressive strength was zero at 3 days. Through the study of cement suspension at 3 days, it was found that the retardation mechanism is mainly due to the obstruction of Ca leaching. On one hand, the C3S content in the HFC clinker decreases and the grain size of the calcium silicate minerals increases, on the other hand, the Ca2(OH)4·4Cu(OH)2·H2O coats clinker particles at the early stage, leading to a lower hydration degree of the HFC clinker. [ABSTRACT FROM AUTHOR]

Pond ash is a mixture of fly ash and bottom ash obtained from thermal power plants. The cement treatment of pond ash results in improved cohesion and strength gain due to cement hydration and pozzolanic reactions. The optimum moisture content (OMC) obtained from standard Proctor compaction tests on untreated and cemented pond ash is about 25%. This study investigates the sufficiency of this OMC for complete hydration of cement, especially for higher dosages, in cement stabilized pond ash systems. The degree of hydration is quantified using Fourier transform infrared (FTIR) spectroscopy, and the corresponding improvement in strength is evaluated using unconfined compressive strength (UCS) tests. The corresponding porosity is not measured directly, but calculated from the dry unit weight and specific gravity of the material. Three water contents (OMC-2% , OMC, and OMC+2%), five cement dosages (2%, 4%, 6%, 8%, and 24%) and three curing periods (7, 14, and 28 days) are adopted. The results show that the untreated pond ash did not undergo hydration reactions upon adding water due to its lower calcium content. For cement-treated pond ash, the formation of calcium silicate hydrates (C-S-H) increases with cement dosage, curing period, and water content. At intermittent curing conditions of 7 and 14 days, the C-S-H formation reached a saturation point for lower cement dosages at OMC but continued to increase with the increase in water content for 24% cemented pond ash system. For 28 days curing, the C-S-H formation reached a maximum at OMC, and a further increase in water content did not increase the C-S-H content. Here, further addition of water does not contribute to hydration and pozzolanic reactions, but water acts as a pore-filling fluid. This is reflected through a corresponding variation in porosity and the UCS value. [ABSTRACT FROM AUTHOR]

Calcium nitrate (CN: Ca(NO3)2) has been shown to mitigate alkali–silica reaction (ASR) in concrete. Such ASR mitigation has been suggested to be on account of precipitate (i.e., barrier or passivation layer) formation‐induced dissolution inhibition of reactive/dissolving aggregate surfaces. Herein, we examine the ability of CN to mitigate ASR across two cements (Type I/II and Portland Limestone Cement), for aggregates of varying reactivity, and across different types and dosages of SCMs (supplementary cementitious materials, i.e., amorphous steel slag and Class C and Class F fly ashes). Based on expansion measurements carried out as per ASTM C1260/C1567, it is observed that CN, as a function of dosage, substantively mitigates ASR in mortar formulations across aggregate types. Careful microstructural examinations, dissolution studies, and thermodynamic calculations indicate that CN induces the formation of C–S–H, portlandite (Ca(OH)2), and calcite (CaCO3) precipitate mixtures, which form on aggregate surfaces at the expense of typical ASR gels. Such precipitates create a dissolution barrier and inhibit ASR in both SCM‐free and SCM‐containing formulations. The outcomes indicate that CN is an efficient and cost‐effective ASR mitigation additive (∼$250–$600 per tonne), particularly in a time of dwindling fly ash supplies and unaffordable lithium prices (>∼$12 000 per tonne). [ABSTRACT FROM AUTHOR]

The durability problems in Portland cement are related to decalcification of C–S–H; alkali-activated composites are proposed as alternative, focusing on acid exposure and resistance. They were prepared from recycled materials, basic oxygen furnace carbonated and desulfurization slags. The standard material is 100% metakaolin geopolymer compared to slag-based alkali-activated materials (AAMs) with and without reinforcement of fibers (basalt, and cellulose), added in 4 wt%. The acidic environments are H2SO4, HCl, and HNO3N = 2.14 (10, 7.5, and 12.5 wt%, respectively). The chemical resistance is improved by the addition of basalt fibers. The decrease in weight loss is 48% in HNO3 and 47% in HCl for AAM-Bas sample, while for AAM-Cell it is 9% in HCl and 34% in HNO3. The compressive strength of the AAM and AAM-Bas samples remains constant after HCl attack, while this acid attacks cellulose samples, which are stable in HNO3 and have a compressive strength of 10 MPa. [ABSTRACT FROM AUTHOR]

This study investigates the impact resistance of performance-based geopolymer concrete beams through drop-weight impact tests. Three ordinary portland cement (OPC) beams and 12 geopolymer concrete (GC) beams were tested, considering several research factors, such as concrete strength, longitudinal reinforcement ratio, stirrup ratio, and drop height. The experimental findings indicate that increasing the longitudinal reinforcement ratio or stirrup ratio within a certain range can effectively mitigate damage and deformation in GC beams subjected to impact loading. Furthermore, an increase in strength was observed to result in decreased midspan and residual displacement, while a deflection prediction formula with high accuracy and low dispersion was developed for designing impact-resistant GC beams with an error of no more than 5.5%. Lastly, a dynamic damage criterion for GC beams is proposed to assess their damage under impact loading. [ABSTRACT FROM AUTHOR]

Cementing, as an important part of the petroleum industry, plays a crucial role in ensuring the normal production and development of oil and gas resources. However, due to the brittle nature of Portland cement, it is prone to microcracks when subjected to downhole impact or vibration, which affects normal operations. Moreover, conventional elastic particles have a significant impact on the performance of cement paste, prompting people to continuously research new toughening admixtures. This article reviews the mechanism of toughening additives for oil well cement, the research status of physical toughening agents (fibers/whiskers, graphene) and polymer toughening agents (latex, epoxy resin, asphalt), aiming to provide reference and guidance for the development of new toughening additives. [ABSTRACT FROM AUTHOR]

In the event of a fire, the performance of concrete becomes pivotal for structural integrity. Concrete undergoes significant changes in its mechanical properties when exposed to high temperatures. This study investigates the mechanical and micro‐characterization of concrete incorporating ground granulated blast furnace slag (GGBFS) under ambient and exposed conditions. The study examines alkali‐activated concrete (AAC) by implementing sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as alkali activators. Three different fractions of GGBFS and alkali activators (AAs) were employed in the concrete mixes. The mechanical properties of the AAC were evaluated under ambient and elevated temperatures, and the results were compared with those of Portland slag cement (PSC). The study's findings indicate that AAC outperforms PSC, and the study recommends using 93% GGBFS with 7% AAs as a suitable replacement for PSC. The mechanical properties of AAC are enhanced by 20%–47% at ambient conditions. The strength loss for the AAC with increased temperature is also less than that of the PSC concrete. [ABSTRACT FROM AUTHOR]

Significant amounts of waste material are generated at various stages of andesite stone processing, including mining, cutting, and polishing. Despite this, limited research has been conducted on the potential use of waste andesite powder (WAP) as a mineral admixture. The impact of WAP on the high‐temperature resistance of cement‐based composites remains largely unexplored. This study aims to evaluate the benefits of incorporating WAP as a partial substitute for Portland cement. Self‐compacting mortars (SCMs) with varying WAP replacement rates (5%–30%) were produced and subjected to temperatures of 300°C, 600°C, and 900°C. Additionally, ternary mixtures of WAP and silica fume were produced for comparative analysis. The results showed that SCMs containing up to 10% WAP exhibited higher 90‐day compressive strength compared to the control sample. Furthermore, WAP inclusion improved high‐temperature resistance, and the use of WAP at higher replacement rates was feasible when combined with mineral admixtures possessing high pozzolanic activity, such as silica fume. [ABSTRACT FROM AUTHOR]

Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement manufacture by 15% to 20%, providing a promising prospect for the large-scale production of low-carbon cement with a lower environmental effect. To effectively manufacture LC3 concrete, this study utilized limestone (15%), calcined clay (30%), and gypsum (5%) as supplementary cementitious materials (SCMs), replacing 50% of ordinary Portland cement (OPC). However, in regions abundant in sulfate, sulfate attack can cause interior cracking of concrete, reducing the longevity of the building. To address this issue, microcapsules containing microcrystalline wax, ceresine wax, and nano-CaCO3 encapsulated in epoxy resin were prepared and successfully incorporated into LC3 concrete. Sulfate resistance tests were conducted through sulfate dry–wet cycles, comparing samples with and without microcapsules. The findings revealed that the initial mechanical and permeability properties of LC3 concrete did not significantly differ from OPC concrete. LC3 concrete with added microcapsules (SP4) exhibited enhanced resistance to sulfate attack, reducing mass loss and compressive strength degradation. SEM images displayed a mesh-like structure of repair products in SP4. After 14 days of self-repair, SP4 exhibited a 44.2% harmful pore ratio, 98.1% compressive strength retention, 88.7% chloride ion diffusion coefficient retention, 91.12 mV maximum amplitude, and 9.14 mV maximum frequency amplitude. The experimental results indicate that the presence of microcapsules enhances the sulfate attack self-healing performance of LC3 concrete. [ABSTRACT FROM AUTHOR]

This paper presents an experimental approach to the study of the compressive strength, isothermal calorimetry and life cycle assessment (LCA) of alkali-activated pastes based on soda–lime–silica glass, established to investigate the effect of the nature and proportion of the activator. Four different activators are compared: Portland cement, sodium silicate, sodium carbonate (at four percentages by weight: 5, 10, 15 and 25 wt% relative to glass) and sodium hydroxide (3.5 wt%). Portland cement and sodium carbonate were added in dry form (powder), while sodium hydroxide (pellets) and silicate were used in solution. At room temperature, glass exhibited slow reaction kinetics, with mechanical performance increasing significantly beyond 28 days of curing. The nature of the activator had a direct impact on the mechanical performance of the activated glass. Cement-activated pastes and those containing 25 wt% of sodium carbonate developed strength at an early age (0–7 days). The other activators showed lower strength development before 28 days of reaction. While a higher activator content improved short-term performance, it also increased the environmental impact, primarily due to the activator. The LCA, conducted on 11 indicators, revealed that the environmental impact was largely driven by the type and amount of activator used. A performance impact indicator (PII) related to global warming was introduced to compare pastes with different performance values. At an early age (0–28 days), the PII was lower when the activator level was high but decreased over time as the strength improved. In terms of long-term performance (360 days), hydroxide and sodium carbonate (10 wt%) achieved compressive strengths of 91 and 74 MPa, respectively. These systems offered a balance between high performance and a reduced environmental impact, making them of interest for sustainable applications. [ABSTRACT FROM AUTHOR]

Alkali-activated concrete (AAC), produced from industrial by-products like fly ash and slag, offers a promising alternative to traditional Portland cement concrete by significantly reducing carbon emissions. Yet, the inherent variability in AAC formulations presents a challenge for accurately predicting its compressive strength using conventional approaches. To address this, we leverage machine learning (ML) techniques, which enable more precise strength predictions based on a combination of material properties and cement mix design parameters. In this study, we curated an extensive dataset comprising 1756 unique AAC mixtures to support robust ML-based modeling. Four distinct input variable schemes were devised to identify the optimal predictor set, and a comparative analysis was performed to evaluate their effectiveness. After this, we investigated the performance of several popular ML algorithms, including random forest (RF), adaptive boosting (AdaBoost), gradient boosting regression trees (GBRTs), and extreme gradient boosting (XGBoost). Among these, the XGBoost model consistently outperformed its counterparts. To further enhance the predictive accuracy of the XGBoost model, we applied four state-of-the-art optimization techniques: the Gray Wolf Optimizer (GWO), Whale Optimization Algorithm (WOA), beetle antennae search (BAS), and Bayesian optimization (BO). The optimized XGBoost model delivered superior performance, achieving a remarkable coefficient of determination (R2) of 0.99 on the training set and 0.94 across the entire dataset. Finally, we employed SHapely Additive exPlanations (SHAP) to imbue the optimized model with interpretability, enabling deeper insights into the complex relationships governing AAC formulations. Through the lens of ML, we highlight the benefits of the multi-faceted synergistic approach for AAC strength prediction, which combines careful input parameter selection, optimal hyperparameter tuning, and enhanced model interpretability. This integrated strategy improves both the robustness and scalability of the model, offering a clear and reliable prediction of AAC performance. [ABSTRACT FROM AUTHOR]

China is the largest producer and user of Ordinary Silicate Cement (OPC), and rapid infrastructure development requires more sustainable building materials for concrete structures. Portland cement emits large amounts of CO2 in production. Given proposals for "carbon peaking and carbon neutralization", it is extremely important to study alternative low-carbon cementitious materials to reduce emissions. Alkali-activated slag (AAS) cement, a new green cementitious material, has high application potential. The chemical corrosion resistance of AAS concrete is important for ensuring durability and prolonging service life. This paper reviews the hydration mechanism of AAS concrete and discusses the composition of hydration products on this basis, examines the corrosion mechanism of AAS concrete in acid, sulfate, and seawater environments, and reviews the impact of its performance due to the corrosion of AAS concrete in different solutions. Further in-depth understanding of its impact on the performance of concrete can provide an important theoretical basis for its use in different environments and provides an important theoretical basis for the application of AAS concrete, so that we can have a certain understanding of the durability of AAS concrete. [ABSTRACT FROM AUTHOR]

Steel corrosion is one of the main factors limiting the durability of existing reinforced concrete components. Based on the corrosive circumstances, different prevention and repair methods can be applied. In the case of carbonation-initiated corrosion, chemical re-alkalisation (CRA) is one of the standard measures to counteract alteration processes in the concrete that lead to reinforcement corrosion. The current state of research on the CRA of carbonated concrete and the various materials that have been investigated in terms of their applicability for this repair measure are summarised. The review summarises current research results in the field of carbonated concrete and the proven pozzolanic reactivity of the carbonation products in contact with portlandite, which suggests an inhibitory effect on CRA, although this has not yet been investigated. There are also initial attempts that deviate from the application of classic Portland cement as a repair material, but their applicability in practice must be questioned. The use of alternative binders and the associated different compositions of pore solutions and varying alkalinity of these binders (e.g. composite cements with a high substitution rate or alkali-activated binders), have not yet been investigated for repair processes such as CRA, although the chemical composition of binders is of the greatest importance for successful application of the repair measure. [ABSTRACT FROM AUTHOR]

Alkali-activated materials (AAMs) are regarded as a substitute for Portland cement. They have high chloride resistance and a low carbon dioxide footprint. The aim of this review is to provide a multi-scale perspective to understand material–product–microstructure–property relationships in terms of the chloride binding behaviour of AAMs. The physical and chemical chloride stability of different reaction products is summarised from nanostructure, to microstructure to macro properties. An analysis of studies in the literature gives an overview of recent progress in chloride transport in AAMs influenced by different reaction products. Results show that a higher calcium/silicon, aluminium/silicon molar ratios and alkali content increase the formation of amorphous phases, leading to a denser microstructure and lower chloride penetration in AAMs. Higher magnesium oxide and aluminium oxide contents result in increased formation of hydrotalcite. The enhanced physical and chemical absorption of chloride by hydrotalcite leads to higher resistance of chloride penetration in AAMs. Investigation of increasing chloride resistance could potentially focus on increasing gel and hydrotalcite formation. [ABSTRACT FROM AUTHOR]

Cement plays a crucial role in mortar composition, and its particles exhibit a strong tendency to flocculate when mixed with water. This flocculation necessitates the addition of substantial water to improve the workability of mortar or concrete. However, this extra water does not contribute to the hydration reaction, potentially weakening the mechanical properties of the mortar. The introduction of superplasticizers has addressed this issue by reducing the water demand. Nevertheless, a common practice in construction is to use a standard dosage of superplasticizers for the same type of cement, even when sourced from different cement factories, which may affect material performance. This study investigated the influence of varying superplasticizer dosages on Portland pozzolana cement from different Ethiopian cement factories, examining the morphological characteristics of masonry mortar. Specifically, it evaluated the impact on cracks, porosity, and surface structure across different curing ages, as well as assessed the mortar's physical and mechanical properties. Mortar samples prepared using cement from three factories, labeled A, B, and C, with constant cement‐to‐sand ratios of 1:3 and water‐to‐cement ratios of 0.5. Superplasticizer added in varying amounts 0%, 0.6%, 0.8%, and 1%. The morphological analysis conducted using a 3D optical surface profiler microscope at 1, 7, 21, and 28 days. Besides these standard physical and mechanical tests also performed on all samples. The results demonstrated that addition of superplasticizers significantly influenced the surface morphology of mortar samples. Mortars A and B exhibited denser structures with superplasticizer dosages 0.8% and 1%, respectively, whereas mortar C displayed a denser structure in its control state (without superplasticizer). The flexural and compressive strength tests also revealed notable differences. Sample A2 (0.8%) from group A, sample B3 (1%) from group B, and sample C0 (0%) from group C achieved the highest strength within their respective groups at 28 days. The findings suggest that it is essential to evaluate the specific properties of cement before applying a standardized superplasticizer dosage, as variations in cement production can significantly influence the performance of the mortar. [ABSTRACT FROM AUTHOR]

Soil stabilization using Portland cement is a widely adopted technique. Previous research has demonstrated that molasses, which contains sugars, enhances the reaction between cement and aggregates. This study investigates the impact of adding molasses to soil stabilized with Ordinary Portland Cement (OPC) on geotechnical properties. Expansive clay soil samples from Taru Jabba, District Nowshera, Pakistan, were treated with various combinations of molasses and cement. The concentrations of each stabilizer were varied at 0%, 4%, 8%, and 12% by dry weight of the soil. Additionally, the soil was treated with constant molasses contents of 4%, 8%, and 12%, while varying the cement content at 4%, 8%, and 12% by dry weight. Geotechnical tests, including Proctor compaction, Atterberg limits, Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and swelling potential, were conducted to assess the effects of the stabilizers. The results indicated that the addition of molasses improved soil strength, mitigated shrinkage cracks, and reduced brittleness. Specifically, the CBR value increased from 3.2% in the native soil to 12.3% with 12% molasses and 12% cement. The Plasticity Index (PI) decreased from 14.23% to 8.12%, and the CBR swell value reduced from 9.66% to 3.82%. Furthermore, the UCS of the stabilized soil increased by 64.7% compared to the untreated soil after a 7 day curing period. [ABSTRACT FROM AUTHOR]

In the lab experiments, the compressive strength (CS) of cement mortar, three pre-setting water/binder (W/B) ratios, five substitution rates of burned joss paper ash (SR-BJPA), and three curing temperatures (T) were tested for the 45 samples. The results were recorded at 3, 7, 28, 56, 90, and 120 days after curing (#days) for each sample. The correlations between CS and each experimental factor (W/B ratio, SR-BJPA, T, and #days) and the effects of each factor or pair of factors on CS were determined using four univariate and six bivariate regression models. All the models were significant (i.e., the factors and the pairs of factors can be used to predict CS); however, each model had a different ability to fit the data and explain the data variance, making some models not that suitable. The effects on CS of substituting cement with different BJPA proportions and curing the mortar at different temperatures were mainly identified. A knowledge base for predicting the CS was established before any sample is to be made in future practise. Finally, using an SR-BJPA of 5% and raising the curing temperature to 50 °C (or 75 °C, if additional heating energy consumption needs not be considered) while keeping the W/B ratio at 0.4 is recommended to obtain an optimal CS for the full-aged sample (i.e., at #days = 120) in future practise, subject to the aim to consume the BJPA wastes by using it to replace Portland cement, in order to reduce the vast volume of carbon emitted along with the production of the cement material. [ABSTRACT FROM AUTHOR]

Geological, mineralogical, and physicochemical information were used to analyze the possible industrial applications and general observations of the Ammacio kaolin occurrence, which is located southwest of the Central Main Ethiopian Rift. The principal lithologic units present in the study area are basalt, unwelded tuff, and Quaternary sediment. The parent rock for the kaolin is the unwelded tuff unit. The petrographic study of the parent rock indicates the presence of plagioclase, alkali-feldspar, and quartz phenocrysts in a fine-glassy groundmass. X-ray diffraction, Fourier transforms infrared, and scanning electron microscopy analyses suggest that the kaolin samples are made up mostly of kaolinite and quartz minerals, with traces of halloysite and feldspar. The distributions of major and selective trace elements in the parent rocks and the kaolin samples, along with the higher chemical index of alteration (CIA = 84.4%) and chemical index of weathering (CIW = 92.4%), indicate that the kaolin is formed by intense chemical weathering of the unwelded tuff. The overall mineralogical and physicochemical findings suggest that Ammacio kaolin may be employed in a variety of sectors, including in paper coating, as a filler (in the paper, rubber, plastic, and paint industries), ceramics, agriculture, pottery, brick, soap and detergent, cosmetics, fiberglass, pharmaceutical, Portland cement, and synthetic zeolites productions industries. [ABSTRACT FROM AUTHOR]

This paper aimed to investigate the durability of ambient-cured fly ash-phosphogypsum blended geopolymer mortar (GPM) when exposed to a water and sulfate environment at different durations. Water absorption, porosity, and sulfate resistance tests were conducted to determine the durability. The GPM was prepared at 0 wt%, 30 wt%, and 40 wt% PG replacement of fly ash content in the mixture. The mix proportions were determined experimentally at 10 M sodium hydroxide, alkaline liquid/precursor of 0.4, sodium silicate/sodium hydroxide of 1.5, and binder/aggregate of 1.0. The samples were immersed in potable water and magnesium sulfate solution. The changes in weight, length, and compressive strength were monitored. Scanning electron microscopy-energy dispersive X-ray spectroscopy was used to analyze the structure and composition. The findings showed that GPM with 30 wt% phosphogypsum added had lower water absorption, porosity, and sulfate attack than GPM with 0 wt% phosphogypsum attributed to the formation of hydrated gels leading to a dense microstructure and improved strength. The changes in weight, length, and strength variations trend for GPM were within optimal performance standards. This has implications for the practical application of GPM in construction where it can be used as an alternative to Portland cement mortar in sulfate-rich environments. [ABSTRACT FROM AUTHOR]

This study focuses on the role of low-quality calcined Fanja (FNJ) clay in enhancing the behavior of cured cement mortar (CM) and its resistivity to chloride and sulfuric acid attack. Ordinary Portland cement was replaced with different quantities (10%, 25%, 35%, and 50% by weight) of FNJ, which was calcined at different temperatures (620 °C, 760 °C, and 900 °C). After 28 days of curing, all the hardened mortars were immersed in 5% sulfuric acid for up to 12 weeks. Additionally, a rapid chloride permeability test was conducted on the 91-day cured CM and CM-FNJ samples to evaluate the affinity of calcined FNJs to retard the chloride diffusion into CM. The results showed that all samples containing FNJ900 showed better physical and mechanical properties than the control sample, while CM with NFJ760 recorded nearly similar performance as CM-NFJ900. In contrast, the CM-FNJ620 mixtures showed lower properties than those of other mixtures. In addition to the pozzolanic reactivity of the calcined clay, the presence of hematite in the calcined clay strongly contributed to increasing the mechanical properties of the hardened mortar through forming calcium ferrosilicate hydrate binding phase, as confirmed by X-ray diffraction. Moreover, the existence of hematite increased the resistivity of CM against sulfuric acid attack as it acts as a buffer for an acidic medium. Compared with CM-FNJ900, the CM-FNJ760 is recommended for use as it exhibited a higher strength activity index and comparable resistance to accelerated chloride diffusion and sulfuric acid accompanied by lower energy demand and lower CO2 emission, achieving the concept of 'sustainability'. [ABSTRACT FROM AUTHOR]

The utilization of geopolymer as a grouting material has gained significant attention in research and construction applications. Geopolymer grout is a type of binding material that differs from traditional grouts, typically based on Portland cement. Researchers have explored its effectiveness and potential applications in grouting processes, considering its unique properties and characteristics. In this paper, various studies employing and utilizing geopolymer as a grouting material are reviewed. The emphasis is on mixture design of geopolymer grout, physical property, chemical composition of geopolymer grout, rheological behavior of geopolymer grout such as yield stress (in case of Bingham fluid) and viscosity, and engineering properties such as compressive strength, expansion, shrinkage, etc. [ABSTRACT FROM AUTHOR]

Ground granulated blast furnace slag (GGBFS) conventionally has been mixed with ordinary Portland cement (OPC) owing to decrease the ecological impact and improve the engineering behavior. Concrete with GGBFS illustrates different strength enhancement of normal concrete, but sensitive, to environmental situation. Recently, the studies of decreasing the environmental impact of utilizing ordinary Portland cement in concrete production showed great attention. In this range, this study highlights the using of local blast furnace slag in producing cementitious material. In this paper, alkali-activated GGBFS replaced the OPC and ordinary GGBFS by ratios calculated by several compressive experiments. Compressive strength demonstrated that CB40 and CB50 have equal compressive strength as OPC. On the contrary, ACB60 showed (36%) increase in compressive strength over OPC for (28 days) curing. SEM and XRD analysis demonstrated formation of high content gels by incorporation alkali agent. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) represents an innovative alternative to traditional Portland cement concrete. The alkaline activators and precursors play pivotal roles in making GPC environmentally sustainable. This study delves into the positive effects of applying metakaolin (MK) as precursor in combination with an alkaline activator solution (AAS), consisting of calcium hydroxide (Ca(OH)2) and sodium silicate (Na2SiO3) on the strength enhancement. This study involves the exploration of several key factors, including water-to-solid binder ratios (W/B), Na2SiO3 to Ca(OH)2 ratios, alkaline activating solution to MK (AAS/ MK) ratios, superplasticizer dosages, MK quantities, curing temperature degrees, and heat curing durations. The objective of this article is to assess the consequences of optimizing MK with AAS on the Compressive strength (CS) of GPC. The experimental results demonstrated that optimization of GPC was achieved with a W/B of 0.75, a Na2SiO3 to Ca(OH)2 ratio of 1.5, a AAS to MK ratio of 1, a superplasticizer dosage of 1.5%, a MK quantity of 400 kg m-3, and an oven curing temperature of 80℃ for 24 hours, at a standard air curing duration of 28 days. Additionally, with an increasing curing age of the GPC specimens from 2 to 28 days, the CS increases from 14.74 MPa to 31.62 MPa. This reflects the successful formulation of GPC through the polycondensation process involving MK as a geopolymeric precursor and alkali polysilicates. The significance of this study lies in its contribution to the development of more environmentally friendly concrete solutions, promoting the use of alternative materials in the construction industry. [ABSTRACT FROM AUTHOR]

The global production of furfural generates substantial amounts of furfural residue waste annually, which, if not properly managed, can lead to significant environmental pollution. However, the ash produced from the combustion of this biomass waste shows promise as a cement additive, offering an innovative solution for furfural residue management. In this study, ash obtained from the combustion of furfural residue in industrial boilers was used as an additive in both Portland cement and magnesium oxysulfate cement, with concentrations ranging from 5% to 20%. Mortar specimens were then prepared and tested for compressive and flexural strength at 3, 7, and 28 days. The results indicated that at a 10 wt% addition, the formation of cotton-like structures and ettringite needles was most pronounced, resulting in the highest compressive and flexural strengths in the Portland cement specimens. Similarly, in magnesium oxysulfate cement, a 10 wt% ash addition significantly promoted the formation of the 5 · 1 · 7 phase, leading to the highest compressive strength. In summary, under appropriate conditions, furfural residue ash can be effectively utilized as a cement additive, contributing to resource recovery and sustainable waste management. [ABSTRACT FROM AUTHOR]

The present study aims to determine the mix proportion of binder, heavyweight aggregates, water-to-binder ratio, and additives to develop self-compacting concrete with a bulk density higher than 2600 kg m−3. It also aims to evaluate the engineering properties, pore structure, and microstructure of established heavyweight self-compacting concrete. Barite (BA), magnetite (MAG) or their mix (MIX) were used as fillers, while binder was composed of Portland cement, blast furnace slag, metakaolin, and limestone at a ratio of 65:15:5:15. Based on text results of V-funnel, S-Cone diameter and S-Cone time, the proportion mix and binder: filler: binder to cement ration was optimized as follows: 1) BA 1: 3.5: 0.42, 2) MAG 1: 4: 0.42, and 3) MIX 1: 3.75: 0.42 with maximal aggregate size not exceeding 2 mm. Not only the bulk density was influenced by aggregate, but also, the mechanical properties, shrinkage, dynamic modulus of elasticity pore structure, and microstructure were also found to be dependent on fillers. [ABSTRACT FROM AUTHOR]

The hydration heat of a four-component binder consisting of Portland cement (CEM I 42.5 R), blast-furnace slag (BFS), metakaolin (MK), and silica fume (SF) was investigated using a conduction calorimeter and thermal analytical method to optimize the material composition of self-compacting mortar (SCM). Then, the influence of material composition with different substitution levels (0, 25, 30, and 35% labelled as SCM100, SCM75, SCM70, and SCM65) on physical and mechanical properties of the mortars with two volumetric binder sand ratios of 1:1 and 1:2 (cement: sand) was evaluated. Furthermore, two mortar compositions comprising SCM75 and sand at 1:1 and 1:2 ratios were used to prepare fibre-reinforced self-compacting mortars in five combinations (0, 0.25, 0.5, 0.75, and 1%) of two fibres (polypropylene-PPF and basalt-BF) at a constant content of 1.00 vol%. The properties of the prepared samples were investigated with respect to the characteristics of self-compactibility and mechanical properties of fresh and hardened states, respectively. The rheology characteristics expressed by slump flow, V-funnel, and T20 were found following the EFNARC guidance. The partial replacement of cement by supplementary cementitious materials has enhanced the performances (compressive and flexural strengths, dynamic modulus of elasticity) of self-compacting mortars from the 7th day through pozzolanic activity. Furthermore, adding fibres has enhanced the DME and microstructure of the self-compacting mortars. [ABSTRACT FROM AUTHOR]

Stabilization of soil using cement can increase the bearing capacity, compaction, and strength characteristics. However, limited research has been conducted on cemented clayey sand, and there is a lack of knowledge of the combined effect of clay content and cement content on the strength and deformability characteristics of mixed soil. In the present study, two soil mixtures were prepared: (1) Soil A consists of 80% sand and 20% clay, and (2) Soil B consists of 60% sand and 40% clay. The prepared mixtures were stabilized by Portland cement at target ratios of 1%, 2%, and 3% by dry weight, and they were cured for 7, 14, and 28 days. A series of unconfined compression tests were performed on the untreated and cement-treated specimens. There was a continuous increase in the unconfined compressive strength (UCS) with the increase in cement content, clay content or curing period. The deformability index rose with the growth of the clay content, but it decreased over time with increasing the curing period. Two empirical equations have been developed on the basis of the cement and clay contents to predict the UCS of cemented clayey sand at any curing time (≤ 28 days). [ABSTRACT FROM AUTHOR]

The activation product chlorine-36 (36Cl) is an important radionuclide within the context of the disposal of nuclear wastes, due to its long half-life and environmental mobility. Its behaviour in a range of potential cementitious encapsulants and backfill materials was studied by evaluating its uptake by pure cement hydration phases and hardened cement pastes (HCP). Limited uptake of chloride was observed on calcium silicate hydrates (C-S-H) by electrostatic sorption and by calcium monosulphoferroaluminate hydrate (AFm) phases, due to anion exchange/solid solution formation. Diffusion of 36Cl through cured monolithic HCP samples, representative of cementitious materials considered for use in deep geological repositories across Europe, revealed a markedly diverse migration behaviour. Two of the matrices, a ground granulated blast furnace slag/ordinary Portland cement blend (GGBS–OPC) and an ordinary Portland cement (CEM I) effectively retarded 36Cl migration, retaining the radionuclide in narrow, reactive zones. The migration behaviour of 36Cl within the cementitious matrices is not strictly correlated to the measured sorption distribution ratios (Rd-values), suggesting that physical factors related to the microstructure can also have a distinct effect on diffusion behaviour. The findings have implications when selecting cementitious grouts and/or backfill materials for 36Cl-bearing radioactive wastes. [ABSTRACT FROM AUTHOR]

This study aimed to develop optimized alkali-activated concrete using ferronickel slag for high-temperature applications, focusing on minimizing environmental impact while maintaining high compressive strength and slump. A response surface methodology, specifically the mixture design of experiments, was employed to optimize five components: water, FNS-based alkali-activated binder, and three aggregate sizes. Twenty concrete mixes were tested for slump and compressive strength before and after exposure to 600 °C for two hours. The optimal mix achieved 88 MPa compressive strength before heat exposure and 34 MPa after, with a slump of 140 mm. An upscaled version with improved workability (210 mm slump) maintained similar unheated strength but showed reduced post-heating strength (23.5 MPa). Replacing limestone with olivine aggregates in the upscaled mix resulted in 65 MPa unheated and 32 MPa post-heating strengths. Life Cycle Analysis revealed that the optimized ferronickel slag alkali-activated concrete's CO2 emissions were 77% lower than those of ordinary Portland cement concrete of equivalent strength. This approach demonstrated the applicability of mixture design of experiments as an alternative design methodology for alkali activated concrete, providing a valuable performance-based design tool to advance the application of alkali-activated concrete in the construction industry, where no prescriptive standards for alkali-activated ferronickel concrete mix design exist. The study concluded that the developed ferronickel slag alkali-activated concrete, obtained through a performance-based mixture design methodology, offers a promising, environmentally friendly alternative for high-strength, high-temperature applications in construction. [ABSTRACT FROM AUTHOR]

Alkali activated materials (AAMs) offer significant advantages over traditional materials like Portland cement, but require the use of strong alkaline solutions, which can have negative environmental impacts. This study investigates the synthesis of AAMs using metakaolin and wollastonite, aiming to reduce environmental impact by eliminating sodium silicate and using only sodium hydroxide as an activator. The hypothesis is that wollastonite can provide the necessary silicon for the reaction, with calcium from wollastonite potentially balancing the negative charges usually countered by sodium in the alkaline solution. This study compares raw and carbonated wollastonite (AAM-W and AAM-CW) systems, with raw materials carefully characterized and binding networks analyzed using TGA, FT-IR, and XRD. The results show that while wollastonite can reduce the amount of sodium hydroxide needed, this reduction cannot exceed 50%, as higher substitution levels lead to an insufficiently alkaline environment for the reactions. The carbonation of wollastonite enhances the availability of silicon and calcium, promoting the formation of both N-A-S-H and C-A-S-H gels. [ABSTRACT FROM AUTHOR]

Cement-based construction materials, commonly known as "cement concrete", result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material's strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%. [ABSTRACT FROM AUTHOR]

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally activated natural zeolite on the structural and physical-mechanical characteristics of cured mortars based on white Portland cement and river sand was investigated. The phase compositions were determined by wavelength dispersive X-ray fluorescence (WD-XRF) analysis, X-ray powder diffraction (PXRD), diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and scanning electron microscopy (SEM), as well as thermogravimetric analysis simultaneously with differential scanning calorimetry (TG/DTG-DSC). The results show that the incorporation of zeolite increases the amount of pores accessible with mercury intrusion porosimetry by about 40%, but the measured strengths are also higher by over 13%. When these samples were aged in an aqueous environment from day 28 to day 120, the amount of pores decreased by about 10% and the compressive strength increased by nearly 15%, respectively. The microstructural analysis carried out proves that these results are due to hydration with a low content of crystal water and the realization of pozzolanic reactions that last over time. Replacing some of the white cement with thermally activated natural zeolite results in the formation of a greater variety of crystals, including new crystalline CSH and CSAH phases that allow better intergrowth and interlocking. The results of the investigations allow us to present a plausible reaction mechanism of pozzolanic reactions and of the formation of new crystal hydrate phases. This gives grounds to claim that the replacement of part of the cement with zeolite improves the corrosion resistance of the investigated building solutions against aggressive weathering. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of different curing temperatures on the hydration and mechanical properties of high-volume fly ash (HVFA) concrete. The key variables were curing temperature (13 °C, 23 °C, 43 °C) and fly ash (FA) content (0%, 35%, 55%). The hydration characteristics of HVFA cement were examined by evaluating the setting time and heat of hydration under different curing temperatures. The mechanical properties of HVFA concrete were analyzed by preparing concrete specimens at various curing temperatures and measuring the compressive strength at 7, 28, 56, and 91 days. The results indicated that concrete with high FA content was more sensitive to curing temperature compared to ordinary Portland cement. [ABSTRACT FROM AUTHOR]

This paper presents a novel low-carbon binder formulated from fly ash (FA), ground granulated blast furnace slag, steel slag, and desulfurization gypsum as a quaternary solid waste-based material. It specifically examines the influence of FA content on the mechanical properties and hydration reactions of the quaternary solid waste-based binder. The mortar test results indicate that the optimal FA content is 10%, which yields a 28-day compressive strength 11.28% higher than that of the control group without FA. The spherical particles of fly ash reduce the overall water demand and provide a "lubricating" effect to the paste due to their continuous gradation, improving the fluidity of the slag-steel slag-gypsum cementitious materials. The micro test results indicate that fly ash has minimal effect on the early hydration products and process of the solid waste-based cementitious materials, but after 7 days, it continuously dissolves silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons, consuming Ca2+ and OH− in the system. After 28 days, the amount of ettringite and C-(A)-S-H gel generated increases significantly. The pozzolanic activity of fly ash is mainly stimulated by the Ca(OH)2 from steel slag in the later hydration stage. Additionally, spherical fly ash particles can fill the voids in the hardened paste, reducing the formation of cracks and weak zones, and thereby contributing to a denser overall structure of the hydrated binder. The findings of this paper provide data support for the development of low-carbon cement-free binders using fly ash in conjunction with metallurgical slags, thereby contributing to the low-carbon advancement of the construction materials industry. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance. [ABSTRACT FROM AUTHOR]

The effects of micro-sized montmorillonite clay (MMT) on Portland cement concrete were examined in this study, focusing on regular and calcined MMT as partial cement replacements. Key properties assessed include consistency, setting time, flexural strength, and compressive strength at 7 and 28 days. Regular MMT initially acts as an inert filler, potentially reducing compressive strength, while calcined MMT improves compatibility and strength. Both types extend the setting time, with regular MMT causing more delay. The study highlights that the regular MMT increases water demand and setting time, whereas calcined MMT enhances strength and mitigates these issues. The results emphasize the importance of carefully choosing MMT type and dosage. [ABSTRACT FROM AUTHOR]

The present study investigated the synergistic influence of coal bottom ash (CBA) on the shear strength of concrete. CBA was milled for 2, 6, and 10 h to form grinded CBA (GCBA). "L" shaped specimens were prepared with 10%–30% GCBA and 25%–50% CBA as alternative of Portland cement and natural fine aggregates. Concrete containing 20% GCBA (grinded for 6 h) and 25% CBA reported the highest shear strength owing to pozzolanic reactiveness and filler action. X-ray diffraction, scanning electron microscopy–energy-dispersive spectroscopy and Fourier transform infrared also supported the experimental outcomes. Well fitted mathematical models were derived followed by optimization using desirability function approach recommending 5.71 h of grinding, 26.27% GCBA, and 36.69% CBA as the optimum amount for its successful utilization in concrete. This approach further leads to significant reduction of about 22% in carbon footprints and eco-costs in comparison to conventional concrete. [ABSTRACT FROM AUTHOR]

Portland cement concrete (PCC) is the construction material most used worldwide. Hence, its proper characterization is fundamental for the daily-basis engineering practice. Nonetheless, the experimental measurements of the PCC's engineering properties (i.e., Poisson's Ratio -v-, Elastic Modulus -E-, Compressive Strength -ComS-, and Tensile Strength -TenS-) consume considerable amounts of time and financial resources. Therefore, the development of high-precision indirect methods is fundamental. Accordingly, this research proposes a computational model based on deep neural networks (DNNs) to simultaneously predict the v, E, ComS, and TenS. For this purpose, the Long-Term Pavement Performance database was employed as the data source. In this regard, the mix design parameters of the PCC are adopted as input variables. The performance of the DNN model was evaluated with 1:1 lines, goodness-of-fit parameters, Shapley additive explanations assessments, and running time analysis. The results demonstrated that the proposed DNN model exhibited an exactitude higher than 99.8%, with forecasting errors close to zero (0). Consequently, the machine learning-based computational model designed in this investigation is a helpful tool for estimating the PCC's engineering properties when laboratory tests are not attainable. Thus, the main novelty of this study is creating a robust model to determine the v, E, ComS, and TenS by solely considering the mix design parameters. Likewise, the central contribution to the state-of-the-art achieved by the present research effort is the public launch of the developed computational tool through an open-access GitHub repository, which can be utilized by engineers, designers, agencies, and other stakeholders. [ABSTRACT FROM AUTHOR]

[Display omitted] • MSWI FA was solidified by MgO, CaO, and Portland cement for comparison. • MgO showed notably superior stabilization for heavy metals compared to CaO and PC. • The chemical form distribution and leachate pH influenced the leaching toxicity. • MgO can be adopted for the solidification and subsequent potential use of MSWI FA. The significant production of municipal solid waste incineration fly ash (MSWI FA) underscores the importance of developing efficient solidification materials. This study employed MgO and CaO for immobilizing MSWI FA (with a 70% fly ash incorporation), and the immobilization effect was compared with that of Portland cement (PC). Experimental findings revealed that MgO exhibited the most effective stabilization for heavy metals (Cd, Cu, Pb, and Zn) compared to CaO and PC. XRD, FTIR, TG, and SEM analysis indicated that the principal hydration products in MSWI FA binders solidified with MgO, CaO, and PC were Mg(OH) 2 , CaCO 3 , and C-S-H gel, respectively. Mg(OH) 2 efficiently immobilized heavy metals through chemical complexation and surface adsorption mechanisms. The MgO-treated MSWI FA demonstrated the highest residual fractions and the lowest easily leachable fractions. Moreover, the leaching characteristics of heavy metals were significantly influenced by the pH level, so MgO-treated MSWI FA with a leachate pH of 9.18 achieved the precipitation and stabilization of most heavy metals. In summary, this study provided an effective material selection for MSWI FA immobilization and presented a novel strategy for MSWI FA management. [ABSTRACT FROM AUTHOR]

• Recycled MSWI bottom ash as partial replacement of natural aggregates in concrete. • Incorporating Portland limestone cement presents another avenue for sustainability. • Both ash streams investigated met performance metrics for reuse. • Advanced metal recovery has little impact on MSWI-ash amended concrete performance. The optimization of alternative materials in concrete production continues to garner considerable attention in order to meet sustainability goals and supplement natural materials. Portland limestone cement (PLC) and municipal solid waste incineration (MSWI) bottom ash (BA) have been proposed separately as green cement and coarse aggregate supplement in low-strength concrete production, creating sustainable products and alternative disposal scenario for a waste material. This study discusses the impact of advanced ash processing techniques on aggregates and presents the performance of concrete incorporating both of these products with PLC for the first time. Two sources of MSWI BA were investigated, one as-produced (TMR) and one processed with novel advanced metals recovery (AMR). The AMR process reduced total Al content in ash compared to TMR (20,500 vs 17,000 mg/kg), though not aluminum oxide content, as the AMR process targets metallic aluminum. A composition study on both aggregates supports a reduction in ferrous and non-ferrous metals following the AMR process. All control and test mixes met 28-day compressive strength requirements (17 Mpa). Both AMR and TMR MSWI BA-amended concretes yielded compressive strengths below control specimens (no ash) ranging from 17 to 23 MPa, with little to no difference observed dependent on MSWI BA processing. The life-cycle discussion supports benefits deriving from supplementing naturally mined materials and recovering ferrous and nonferrous metals with the AMR process. [ABSTRACT FROM AUTHOR]

The present study examines the regulatory role of natural pozzolana (NP) on the early-age hydration process and microstructural development of Portland cement. Through a series of experiments, including low-field nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM), it was found that NP significantly influences the hydration kinetics and chemical shrinkage of cement paste. The addition of NP was shown to reduce the early-age chemical shrinkage and refine the microstructure by decreasing the quantity of harmful pores and increasing harmless pores, as evidenced by the bimodal distribution observed in pore size distribution (PSD) analysis. XRD and TG results indicate that NP reacts with calcium hydroxide to form additional calcium silicate hydrate (C-S-H) gel, thus improving the interfacial transition zone and resistance to carbonation. SEM micrographs further confirm the improved microstructure with fewer microcracks. The findings suggest that NP can be effectively utilized to optimize the early-age performance of concrete, offering a sustainable approach to improving its durability and long-term structural integrity. [ABSTRACT FROM AUTHOR]

Partial replacement of portland cement with supplementary cementitious materials (SCMs), such as fly ash, is an effective strategy for improving durability and reducing the CO2 footprint of concrete. However, using high-volume fly ash (HVFA) binders in precast and prestressed concrete is currently limited; largely due to reduced early-age strength development that impedes rapid production and prestressing of precast concrete. To investigate and address this challenge, HVFA mortars with a minimum of 40% fly ash by mass of cementitious materials were developed and tested in this study. Two fresh fly ashes (an ASTM C618 Class F and a Class C) and a landfilled fly ash (Class F) were included. Various strategies for improving the early strength were evaluated, including gypsum optimization, chemical accelerators, steam curing, use of CSA cements, and adding other reactive SCMs like silica fume, calcined clay, and slag cement. Steam curing and the use of CSA cement at high dosages (40% of total binder) were found to be the most successful strategies across all three fly ashes. Additionally, significant improvements were observed with gypsum optimization (for Class C fly ash) and the use of accelerators (for Class F fly ashes), and these strategies are likely to be more feasible considering later-age strength and economic viability. Interestingly, HVFA mixtures made with the landfilled fly ash used in this study were able to achieve high early strengths with water-to-cementitious materials ratio adjustment alone. These HVFA mixtures were also found to be less responsive to accelerators when compared to the fresh Class F fly ash, highlighting an important distinction between the materials despite the similarity in chemical composition. [ABSTRACT FROM AUTHOR]