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The pre-eminence of concrete as the constitutional material used for rigid pavement construction has emanated through the millennia thereby amplifying the concern associated with its adverse effect on the environment. In this context, geopolymer concrete not only proposes a sustainable solution but also addresses the problems associated with extensive industrial waste generation and its imprudent disposal. This study aims to highlight the relevance of fly ash (FA) and red mud (RM) as geopolymer synthesizing source materials for pavement quality concrete (PQC). Investigations were designed to study the effect of varying replacement levels of FA (10%, 20%, 30%, and 40%) with RM in conjunction with different concentrations of sodium hydroxide in terms of molarity (10 M, 12 M, 14 M). The specimens subjected to ambient curing and oven curing at 60 °C were tested for compressive strength, flexural strength, and split tensile strength. Results portray that in the case of ambient cured FA-RM specimens, the highest compressive strength and flexural strength that could be achieved were 31.5 MPa and 4.32 MPa, respectively. Thereby, indicating inadequate strength development as per the requirements of PQC, even at a higher concentration of sodium hydroxide. Moreover, replacing FA with RM is mostly not effective at replacement values greater than 20% in both compression and tension. Furthermore, a defined study for assessing durability properties was also conducted by immersing the specimens in a 5% sulfuric acid solution. 11.46% and 7.25% reduction in compressive strength of control mixes was observed for specimens corresponding to 10 M and 14 M respectively, thereby substantiating decreased strength loss at higher molarity. [ABSTRACT FROM AUTHOR]

Geopolymer is an environment friendly construction material that could be synthesized using either the natural source or the industrial byproducts such as flyash and GGBS. The characteristics of the Geopolymer rely on the proportion of the flyash and GGBS and the concentration of the activator solution used. In this research work, the effect of partial replacement of flyash with GGBS in proportions such as 0, 10, 20, 30 and 40% is investigated. Also Molarity of NaOH are tested from 8 to 14 M and both the parameters are optimized. In this optimized Geopolymer concrete, the utilization of iron slag as a partial substitute for river sand in various proportions such as 10, 15, 20, 25, 30 35, 40 and 45% are investigated. The optimized Geopolymer concrete with iron slag is investigated for its performance as a paver block with incorporation of banana fiber in proportions such as 0, 0.5, 1 and 1.5 and is compared with conventional cement concrete paver block. The results show that there is a significant enhancement in the properties of Geopolymer concrete with the different levels of optimization and the utilization of natural banana fiber. The developed sustainable paver block was found to with stand medium traffic conditions as per IS 15658:2006. Further this study employed random forest (RF) algorithm for the prediction of compressive strength of geopolymer concrete specimens for the variable parameters such as molarity of alkaline solution, Flyash/GGBS ratio and partial replacement of river sand with iron slag. The performance evaluation parameters represented high accuracy of developed RF model. This research work unleashes a heft potential of Geopolymer concrete to develop economical eco-friendly sustainable paver blocks to the society through mitigation of environmental strain on the ecosystem. [ABSTRACT FROM AUTHOR]

Geopolymer is an environment friendly construction material that could be synthesized using either the natural source or the industrial byproducts such as flyash and GGBS. The characteristics of the Geopolymer rely on the proportion of the flyash and GGBS and the concentration of the activator solution used. In this research work, the effect of partial replacement of flyash with GGBS in proportions such as 0, 10, 20, 30 and 40% is investigated. Also Molarity of NaOH are tested from 8 to 14 M and both the parameters are optimized. In this optimized Geopolymer concrete, the utilization of iron slag as a partial substitute for river sand in various proportions such as 10, 15, 20, 25, 30 35, 40 and 45% are investigated. The optimized Geopolymer concrete with iron slag is investigated for its performance as a paver block with incorporation of banana fiber in proportions such as 0, 0.5, 1 and 1.5 and is compared with conventional cement concrete paver block. The results show that there is a significant enhancement in the properties of Geopolymer concrete with the different levels of optimization and the utilization of natural banana fiber. The developed sustainable paver block was found to with stand medium traffic conditions as per IS 15658:2006. Further this study employed random forest (RF) algorithm for the prediction of compressive strength of geopolymer concrete specimens for the variable parameters such as molarity of alkaline solution, Flyash/GGBS ratio and partial replacement of river sand with iron slag. The performance evaluation parameters represented high accuracy of developed RF model. This research work unleashes a heft potential of Geopolymer concrete to develop economical eco-friendly sustainable paver blocks to the society through mitigation of environmental strain on the ecosystem. [ABSTRACT FROM AUTHOR]

Geopolymer is an environment friendly construction material that could be synthesized using either the natural source or the industrial byproducts such as flyash and GGBS. The characteristics of the Geopolymer rely on the proportion of the flyash and GGBS and the concentration of the activator solution used. In this research work, the effect of partial replacement of flyash with GGBS in proportions such as 0, 10, 20, 30 and 40% is investigated. Also Molarity of NaOH are tested from 8 to 14 M and both the parameters are optimized. In this optimized Geopolymer concrete, the utilization of iron slag as a partial substitute for river sand in various proportions such as 10, 15, 20, 25, 30 35, 40 and 45% are investigated. The optimized Geopolymer concrete with iron slag is investigated for its performance as a paver block with incorporation of banana fiber in proportions such as 0, 0.5, 1 and 1.5 and is compared with conventional cement concrete paver block. The results show that there is a significant enhancement in the properties of Geopolymer concrete with the different levels of optimization and the utilization of natural banana fiber. The developed sustainable paver block was found to with stand medium traffic conditions as per IS 15658:2006. Further this study employed random forest (RF) algorithm for the prediction of compressive strength of geopolymer concrete specimens for the variable parameters such as molarity of alkaline solution, Flyash/GGBS ratio and partial replacement of river sand with iron slag. The performance evaluation parameters represented high accuracy of developed RF model. This research work unleashes a heft potential of Geopolymer concrete to develop economical eco-friendly sustainable paver blocks to the society through mitigation of environmental strain on the ecosystem. [ABSTRACT FROM AUTHOR]

In recent years, the reuse of industrial waste has become increasingly important for sustainable development. Therefore, this study investigated the application of granulated blast furnace slag (GBFS) as a cementitious replacement material in fly-ash-based geopolymer mortar containing silica fume (GMS). The performance changes in the GMS samples manufactured with different GBFS ratios (0–50 wt%) and alkaline activators were evaluated. The results indicated that GBFS replacement from 0 wt% to 50 wt% significantly affects GMS performance, including improving the bulk density from 2235 kg/m3 to 2324 kg/m3, flexural-compressive strength from 5.83 MPa to 7.29 MPa and 63.5 MPa to 80.2 MPa, respectively; a decrease in water absorption and chloride penetration, and an improvement in the corrosion resistance of GMS samples. The GMS mixture containing 50 wt% GBFS demonstrated the best performances with notable results regarding strength and durability. Owing to the increased production of C-S-H gel, the microstructure of the GMS sample containing more GBFS was denser, as obtained via the scanning electron micrograph analysis results. Incorporating the three industrial by-products into geopolymer mortars was verified when all samples were determined to be in accordance with the relevant Vietnamese standards. The results demonstrate a promising method to manufacture geopolymer mortars that aid sustainable development. [ABSTRACT FROM AUTHOR]

Naturally available plants such as fiber, straw, sawdust, and wood used as reinforcing additives in building materials require an alkali treatment to reduce the moisture sensitivity of additives and to interlock matrix and additive. However, the discharge of alkali-treated plant wastewater (ATPW) is extremely detrimental to the environment. The purpose of this study is to evaluate the effects of recycled ATPW from NaOH-treated sisal leaves, poplar leaves, poplar stems, and corn stems on the characteristics and microstructures of alkali-activated composite materials (AACMs) made from solid wastes. The ATPWs were produced by soaking green and dead plants for 24 h in a 15% NaOH solution. The AACMs were manufactured using ATPW as an alkaline activator and a mixture of slag powder, red mud, fly ash, and steel slag as a binder. The fresh and hardened properties, such as electrical conductivity (EC), fluidity, flexural strength, compressive strength, and density, were examined along with drying shrinkage resistance. Furthermore, SEM, EDS, CT, and FTIR techniques were used to observe and evaluate the pore distributions, morphologies, and products. The results demonstrate that the effects of ATPWs produced from dead sisal leaves were remarkable on the properties and microstructures of AACMs. The sample (DSL) with ATPW exhibits an increase of 43.08% in fluidity and a drop of 50.00% in EC, 44.30% in density, 34.25% in dry shrinkage, 84.44% in flexural strength, and 88.50% in compressive strength, relative to the control without ATPW. Moreover, AACMs physically sequester the organic components of ATPW during the early stage of hardening. The ATPW serves as a unique physical foaming agent in AACMs. The results provide original data on the dual recycling of industrial wastewater and solid waste to promote clean operations. [ABSTRACT FROM AUTHOR]

The necessity of low-cost building and mortar-free wall construction (dry stack masonry) led to the development of a newly proposed block called a fly ash-lime-slag dry stack block (FaL-S DSB) with ingredients from industrial waste materials (fly ash, lime, and ground-granulated blast-furnace slag). The perforations in the proposed DSB accommodate the connecting element between the courses of masonry and headed to mortar-free construction. The scaled FaL-S DSB was produced with five different mix proportions (L10S20, L15S20, L15S25, L20S20, L20S25) by pressing method. The experimental studies were carried out to examine the physical, mechanical, and durability properties and also analyzed the embodied energy and carbon emissions of FaL-S DSB. The compressive strengths of a prism and wall panel made of FaL-S DSB were also studied. Out of five mixes, L20S25 resulted in higher dry and wet compressive strength values of 11.50 and 7.89 MPa, respectively. The values were compared with commercially available red brick (RB). The FaL-S DSB was also observed for loss in weight and loss in strength by immersing in acid (H2SO4) for 1, 3, 7, 28, 56, and 90 days. The L20S25 mix FaL-S DSB exhibited minimum loss in weight (5.69%) and loss in strength (11.50%) compared to other proportions. [ABSTRACT FROM AUTHOR]

Geopolymers are high-performance, cost-effective materials made from industrial waste that ideally fit the needs of 3D printing technology used in construction. The novelty of the present work lies in the investigation of methods to mix geopolymer concrete from fly ash (FA) class F, ground granulated blast furnace slag (GGBS), and raw calcined kaolin clay (RCKC) to determine the mixing procedure which provides the best mechanical strength and structural integrity. The experimental results show that aluminosilicates with different reaction parameters when mixed one after another provide the optimal results while the geopolymer concrete possesses the highest compressive strength and the denser structure. The results demonstrated that the reactivity of GGBS, FA, and RCKC increased for different depolymerization speeds of the selected aluminosilicates. This research will provide results on how to improve the mixing order for geopolymer synthesis for 3D printing demands. The highest compressive strength and denser structure of geopolymer concrete is achieved when each type of aluminosilicate is mixed with an alkaline medium separately. [ABSTRACT FROM AUTHOR]

Geopolymer (GP) concrete is a novel construction material that can be used in place of traditional Portland cement (PC) concrete to reduce greenhouse gas emissions and effectively manage industrial waste. Fly ash (FA) has long been utilized as a key constituent in GPs, and GP technology provides an environmentally benign alternative to FA utilization. As a result, a thorough examination of GP concrete manufactured using FA as a precursor (FA-GP concrete) and employed as a replacement for conventional concrete has become crucial. According to the findings of current investigations, FA-GP concrete has equal or superior mechanical and physical characteristics compared to PC concrete. This article reviews the clean production, mix design, compressive strength (CS), and microstructure (Ms) analyses of the FA-GP concrete to collect and publish the most recent information and data on FA-GP concrete. In addition, this paper shall attempt to develop a comprehensive database based on the previous research study that expounds on the impact of substantial aspects such as physio-chemical characteristics of precursors, mixes, curing, additives, and chemical activation on the CS of FA-GP concrete. The purpose of this work is to give viewers a greater knowledge of the consequences and uses of using FA as a precursor to making effective GP concrete. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) exhibits enhanced performance compared to conventional concrete across various dimensions. These include decreased CO 2 emissions, elevated mechanical strength, improved thermal insulation, greater fire resistance, the valorization of industrial wastes and increased efficiency in energy conservation and production costs. This review focuses on the impact of 11 factors such as class F Fly Ash (FA) characteristics (fineness, SiO 2 /Al 2 O 3 ratio, and iron content), sodium-based alkaline activators parameters such as molarity of sodium hydroxide (SH), Silicate Modulus (SM) of sodium silicate (SS) solution, ratio of SS/SH solution, alkaline liquid to binder ratio, water to binder (w/b) ratio, H 2 O/Na 2 O equivalent , and process variables such as heat curing temperature and heating duration on the compression strength of low calcium (class F or siliceous) FA-based geopolymers (GP). Existing literature explicitly indicates that the molarity of NaOH solution is the primary strength parameter that significantly affects the compression strength of the GPC, among other factors. The range of alkaline activator parameters and heat curing temperature contingent on the SiO 2 /Al 2 O 3 ratio of FA moreover accurately the reactive SiO 2 /Al 2 O 3. Among all factors, one of the crucial parameter is the water content because of its importance in geopolymerization; the additional water released during the chemical reaction has to be considered in the mix design. The aforementioned eleven parameters are analysed and reported in the development of the compressive strength. • Physical, chemical, morphological, and mineralogical properties of class F FA are exhibited. • A pseudo-ternary diagram of FA is constructed by incorporating the principal oxide composition together with alkalis. • The influence of 11 distinct factors on the compressive strength of FA-GP is elucidated. • The potential impact of numerous unexplored factors on the efficacy of FA-GP are suggested as further research endeavours. [ABSTRACT FROM AUTHOR]

The accumulation of industrial solid wastes will cause waste of land resources and environmental pollution. In order to improve the utilization rate of industrial solid wastes, this paper uses cement, saponified slag (SS) and fly ash (FA) as raw materials to prepare saponified slag fly ash foam lightweight soil (SS-FA foam lightweight soil). This study mainly focuses on the basic performance indexes of foam lightweight soil, such as dry density, compressive strength, water absorption and fluidity. The optimization interval of water-binder ratio, SS dosage and FA dosage of SS-FA foam lightweight soil is determined through single factor test. Based on the single factor optimization interval, the orthogonal experiment of three factors and three levels is designed, and the optimal mix proportion of SS-FA foam lightweight soil is obtained through the comprehensive balance method. The results showed that the optimization intervals for each factor of SS-FA foam lightweight soil were 0.51–0.59 water-binder ratio, 5 %-15 % SS dosage, and 5 %-15 % FA dosage. When the water-binder ratio is 0.55, SS dosage 5 %, FA dosage 10 %, the comprehensive performance of SS-FA foam lightweight soil reaches the best. Finally, the microstructure and hydration mechanism of SS-FA foam lightweight soil were studied by means of microscopic means XRD and SEM. It is confirmed that the addition of appropriate amount of SS can effectively improve the pore structure of fly ash foam lightweight soil, promote the early depolymerization of FA, and improve the compactness and bonding performance of fly ash foam lightweight soil. • A novel saponified slag (SS) fly ash (FA) foam lightweight soil (SS-FA foam lightweight soil) was prepared. • SS has good synergistic reaction with FA. • The optimum mix ratio for SS-FA foam lightweight soil was determined. • The microstructure of SS-FA foam lightweight soil as well as the hydration mechanism were analyzed. [ABSTRACT FROM AUTHOR]

In the present research, industrial wastes, e.g., fly ash (FA), lithium slag (LS), ground granulated blast furnace slag (GGBS), and red mud (RM) were utilized to prepare the magnesium phosphate cement (MPC)-based grouting material by a two-component grouting method. Successive additions of GGBS within 40% (C1–C5) led to reduced fluidity, increased pH value, and shortened setting time. The compressive strength increased first and then decreased. The strength value reached the maximum at a 20% dosage (C3). Increasing the content of RM from 0% (C4) to 25% (C9) resulted in prolonged setting time and an increased pH value. The fluidity and compressive strength increased first and then decreased. The fluidity and strength value became the highest at a 15% additive ratio (C7). GGBS can significantly improve the strength and water resistance at 7 days and 28 days by the potential hydraulic property. RM has a smaller particle size than MP, making the microstructure denser by the pore-filling effect. Thus, the drying shrinkage was increased after adding GGBS, while it was decreased when incorporating RM. The MPC-based grouting material has a controllable short setting of 3–21 min, self-leveling fluidity above 200 mm, a near-neutral pH value, high early strength (1 day compressive strength of 5 MPa), minor drying shrinkage (one-tenth of OPC), and excellent water resistance (over 85%), which is much superior to traditional grouting materials. [ABSTRACT FROM AUTHOR]

Red mud, fly ash and waste sawdust are bulk solid wastes discharged from the alumina, power and wood processing industries respectively, and their increasing accumulation has brought serious hazards to the ecological environment and huge waste of secondary resources. A novel rapid roasting method was adopted to produce the ultra-lightweight ceramsites (ULC) using red mud, fly ash and waste sawdust in this work, and the various performances, microstructure and formation mechanism of ULC were investigated using FTIR, XRD, BET, SEM-EDS and Micro-CT. The fly ash significantly enhances the compressive strength of ULC by promoting the formation of small pores and FeAl 2 O 4 , and the increase in roasting temperature is beneficial for the expansion of ULC until they are over burning. As the mass ratios of red mud, fly ash, clay and waste sawdust are 46: 10: 36: 8, the ULC with a compressive strength of 2.25 MPa, a bulk density of 465 kg/m3 and a water absorption of 8.8% are prepared when roasted at 1125 ºC for 5 min after preheating at 600 ºC for 5 min. The environmental assessment results indicates that the ULC are environmentally safe due to the effective solidification of hazardous elements. This study provides a promising way to produce ULC by utilizing industrial solid wastes. • ULC was prepared by novel rapid roasting using red mud, fly ash and sawdust. • The performances and formation mechanism of ULC were investigated. • Fly ash promotes formation of small pores and FeAl 2 O 4 to enhance the strength. • The mesopores generated on the surface contribute to the low water absorption. • The relationship between the performances and microstructure was revealed. [ABSTRACT FROM AUTHOR]

• Industrial ceramic waste being used as a replacement aggregate is a certainty. • Geopolymer with ceramic waste replacement aggregate provides optimal compressive strength. • The type of ceramic waste influences whether the interfacial transition zone (ITZ) is weak or dense in the geopolymer specimen. • Geopolymer compressive strength gradually increases during curing time. This study aims to utilize a range of ceramic waste to replace sand as a fine aggregate in fly ash geopolymer. Ceramic waste aggregates comprised of brick (BR), floor tile (FT), roof tile (RT), and sanitary ware (ST) have been employed for river sand replacement at 0 %, 25 %, and 50 %. The development in compressive strength was investigated on geopolymer mortar at the ages of 7, 14, and 28 days. The results showed that incorporating FT, RT and ST aggregates exhibited comparable and even higher compressive strength than natural sand. The optimum compressive strength was achieved at 47.4 MPa for 50 % ST specimen, accounting for a 17.52 % improvement. The microstructure revealed that ST aggregates exhibited better interfacial transition zone (ITZ) than sand aggregate, thereby increasing the compressive strength of geopolymer mortar. [ABSTRACT FROM AUTHOR]

The reduction of CO2 emission has recently become a global concern. The use of Portland cement has been responsible for the main global warming effects in the construction industry, Geo-polymers have emerged as a new generation of alternatives. Construction has been most important human activity since early ages. The main aim is to study strength characteristics and flexural behaviour of Geo-polymer concrete with Construction Demolition Waste. In this study, Geo-polymer concrete is produced with fly ash, GGBS, and sodium hydroxide and sodium silicate is used as a binder. The mix design is carried out for 12M concentration of sodium hydroxide. Alkaline activator solution ratio of 2.5 and alkaline liquid to fly ash ratio 0.4 is selected for this investigation. The specimen of size 100x100x100mm cubes 100x200mm cylinders and 1200x150x100mm beam were casted and the specimens of Geo-polymer concrete are cured at ambient temperature for 3days, 7 days and 28 days. The cured specimens were then tested for compressive strength, split tensile strength and flexural strength respectively. [ABSTRACT FROM AUTHOR]

The great increase of carbon emission and waste generation has been a major threat to sustainable constructions and buildings. To address this, magnesium oxysulfate cement (MOSC) has recently been introduced as a green and sustainable alternative of Portland cement with lower carbon footprints. This article investigated the binding capability of MOSC with multi-source industrial and forestry wastes by mechanical experiments. 18 samples with waste dosage of 0–70 wt% substituting MgO were prepared and cured for 90d. Multi-source solid wastes improved the flexural strength up to 57.05% and reduced the compressive strength by 3.44% at least. The maximum displacement and absorbed energy before fracture were increased by 63%∼226% and 79%∼274% under flexural loads; the energy absorption capacity under compressive loads reduced by 6.75%∼30%. Six indexes were defined to compare the effects based on both Index Ranking method and Targeted Index Value method. Four samples exhibiting outstanding mechanical strength and low brittleness were found by substituting 40%∼65% mass of MgO. The optimal sample consisting of 20 wt% poplar powder, 20 wt% fly ash, 20 wt% ground slag and 5 wt% bamboo powders as MgO' mass had flexural and compressive strength of 17 MPa and 76 MPa, respectively. Mechanism of wastes' effects on MOSC was discussed by microscopic experiments. The economic and environmental benefits as well as potential application of the optimal composite were discussed. These findings will contribute to the development of more sustainable cement products and improve the utilization of multi-source solid wastes. [Display omitted] • Multi-source industrial and forestry wastes were added into MOSC to prepare new composites. • Flexural strength of MOSC were improved by 57% with outstanding fracture resistance. • Optimal composite containing 65% wastes as MgO' mass had flexural and compressive strength of 17 MPa and 76 MPa. • The cost and benefits of optimal composites were discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chemical compositions of SCM sourced from agricultural waste indicates that they are more pozzolanic than cementitious hence their blends with SCMs sourced from industrial waste provides a sustainable use. • Pozzolanic activities of SCMs provide viable solutions to durability in terms of ASR and chloride sulphate action while cementitious activities exhibit structural performance. • It is shown that ground granular base slag and Pulverised fuel ash reduces the risk of poor compressive strength when used as SCMs by at least 2% and at most 75%. Supplementary cementitious materials (SCM) are alternative to the conventional cement and have been studied by so many authors owing to the high carbon content of cement. The use of SCM is significant in addressing challenges of carbon emission and its impact on the 2050 carbon reduction RoadMap. Available studies shows that SCM obtained from both industrial and agricultural wastes presents significant variability in performance as cement dosage in concrete increases. The first aim of this study is to map and synthesize the available evidence from literatures to support this variability. The second objective is to provide statistical evidence from available literatures of certain SCM that enhance the structural performance of low carbon concrete in terms of compressive strength. From the results, trend of findings from literatures on the use of SCM shows a surge in research for cement replacement occurring over the last decade with optimal performance for industrial waste SCM shown to be limiting at 40% cement replacement while that from agricultural waste occurs at 10% cement replacement. Data were sourced from Scopus database and selected from peer review journals of both primary and secondary studies on cement replacement materials. 728 published articles were obtained from the search using four strings namely,'Recent cement* replacement and cementitious materials", ''Recent supplementary cementitious materials', ''Eco-friendly and cementitious materials" and ''Low carbon intensive cement replacement materials'. Meta-analysis is carried out on the selected articles having quantitative data to synthesise some of the result of the published articles to examine the impact of Ground granular base slag and Pulverized Fuel Ash cement on concrete strength development as cement replacement. It is shown that Ground granular base slag, Pulverized Fuel Ash and Metakaolin improve and enhance the eco friendliness of the concrete. From the results, optimal percentage of cement replacement is a gap which remains unresolved due to mineralogy and reactivity of the SCMs and would provide the solution for the desired green concrete optimization. It is shown with statistical evidence from meta -analysis that ground granular base slag and Pulverised fuel ash decreases the effect of low compressive strength by at least 2% to about 75% which is considered in our opinion as effective to enhance the sustainability of concrete. [ABSTRACT FROM AUTHOR]

• Carbonation curing compensates strength decreasing effect of mineral admixture. • Chloride ion permeability resistance was improved by carbonation curing. • Fly ash exhibits the best promoting effect on carbonation curing and GGBS ranks second. • The formation of CaCO 3 mainly fills the pores with diameters of 0.1 ∼ 1 μm. This paper aims to investigate the influences of limestone powder, fly ash and ground granulated blast-furnace slag (GGBS) on carbonation curing of cement pastes. These three mineral admixtures were incorporated at percentage of 20% by weight to replace cement and compressive strength and chloride ion permeability test were performed to evaluate the carbonation curing effects. On the other hand, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), mercury intrusion porosimeter (MIP) and scanning electron microscope (SEM) measurements were performed on typical samples. Experimental results show that the addition of mineral admixture decreased the compressive strength of uncarbonated specimens but strengthened the improvement effect of carbonation curing on compressive strength. This better improvement effect can partly compensate the decreasing strength induced by the incorporation of mineral admixtures. Among those mineral admixtures, fly ash exhibited the best improvement effect and GGBS ranked second. The chloride ion permeability of cement mortars were decreased by the addition of mineral admixtures but improved by the carbonation curing. The formation of CaCO 3 upon carbonation curing refined the pore structure and presented a higher effectiveness for filling pores with diameters of 0.1 ∼ 1 μm. Therefore, carbonation curing provides a good method for both efficiently recycling industrial wastes as mineral admixtures and capturing more greenhouse gas. [ABSTRACT FROM AUTHOR]

To study the processes of interaction and formation of the phase composition in slag-alkali binders based on fly ash, the alkaline ingredient solution was proportioned after 28 days of aging and after heat treatment, steam curing or setting in natural conditions. The products of interaction of slags and soda-sulfate mixture with highly basic additives were studied. Their phase composition was determined by the type of slag, additives, and setting conditions. The increase in density of alkaline ingredient solution from 1,100 to 1,300 kg/cm³ resulted in a 1.7-2 times higher compressive strength of set binder, which is 30.7, 47.1 and 45.9 MPa, depending on the liquid glass module. When the soda-sulfate mixture was introduced into the formula, the compressive strength of the steam-cured samples was 7-22% higher than that of the samples exposed to dry heat treatment. The strength of slag-alkali binders based on fly ash depended on the fineness of fly ash. The developed binding formulas can be used for the preparation of high-strength concretes and building materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The matrix of augmented-simplex-centroid mixture design in a ternary system was adopted to generate the experiments. • The mixture design methodology optimized the development of a geopolymer paste based on three aluminosilicate precursors. • The physicochemical properties of elaborated geopolymers containing different formulations were investigated and discussed. • The combination 75 %FA-25 %MK was recommended for enhancing the compressive strength of the geopolymeric binder. • The formation of N -A S H gel in synthesized geopolymers was confirmed by structural and microstructure analysis. This study focuses on the application of mixture design as a novel approach to developing a geopolymer paste with optimized mechanical properties. It also aims to utilize the abundance of natural or industrial aluminosilicate precursors through their combination for synthesizing high-performance geopolymers. The synthesis factors studied are kaolin (K), metakaolin (MK), and fly ash (FA) as aluminosilicate sources. Different mixture proportions were prepared by adopting an augmented simplex-centroid design. Twelve geopolymer pastes were synthesized by activating the mixtures with an alkaline solution of sodium hydroxide and sodium silicate. After 28 days of solidification under ambient conditions, the compressive strength (MPa) and bulk density (g/cm3) of the geopolymer samples were measured. The structural and microstructural properties of the raw and elaborated materials were analyzed using a range of physicochemical techniques, including X-ray Fluorescence (XRF) spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM/EDS), and Transmission Electron Microscopy (TEM). The results showed that the compressive strength and bulk density of the geopolymeric pastes ranged from 7.59 to 19.48 MPa and from 1.52 to 1.82 g/cm3, respectively. According to the validated special cubic models and optimization results, the optimum mixture of FA (75 %) and MK (25 %) was found to develop the optimized geopolymer (GPO) paste with the best performance. The optimized geopolymer matrix had a non-porous structure mainly formed by a dense amorphous sodium aluminosilicate gel, which gave excellent mechanical properties (1.82 g/cm3 and 20.80 MPa). The practical application of the results of this study includes the development of an efficient geopolymer paste with excellent mechanical properties that can be employed in construction and civil engineering applications. The significance of this work lies in its potential to reduce environmental impacts and minimize waste disposal by utilizing abundant natural resources and industrial waste in the formulation of practical and efficient products. Overall, this study provides valuable insights into the development of an improved geopolymer paste through the application of a mixture design methodology, which can have a significant impact on the construction and civil engineering industries. [ABSTRACT FROM AUTHOR]

The growing interest in utilization of industrial waste and green construction has motivated the present work. Red mud is an industrial waste produced in the process of extraction of aluminum from bauxite by Bayer’s process. The paper presents the studies conducted to assess the influence of mechanical activation of red mud and curing methods on the strength of red mud-fly ash geopolymer paste. Red mud was used in both unprocessed and pulverised form and the alkali activated paste samples were cured thermally as well as in ambient condition. The percentage of red mud varied from 0 to 90% and alkalinity from 6 M to 12 M NaOH solution. X-ray diffraction (XRD) was carried out to identify the mineral phases in pulverised and unprocessed red mud. SAED (selective area diffraction diagram) test was done on the red mud, along with SEM (scanning electron microscopy), TEM (transmission electron microscopy) and HRTEM analysis (high resolution transmission electron microscopy) to study the effect of mechanical activation and validate the experimental findings. Mechanical activation increased the reactivity of silica and the hematite phase of red mud as reflected in the silica reactivity and Fourier transform infrared spectroscopy (FTIR) test results. Use of pulverised red mud enhanced the mechanical properties of ambient cured paste and the specimens possessed maximum 7 day compressive strength of 40 MPa at 6 M alkalinity with 30% mechanically activated red mud content. [ABSTRACT FROM AUTHOR]

The production of ordinary portland cement that binds the concrete together not only consumes significant amount of raw material and energy but also emits enormous amount of CO2.Growing environmental concern and the need for sustainable construction material had driven the material scientist search for alternative binder to OPC. In recent past geopolymers, generally viewed as subset of alkali activated materials (AAM) where the binding phase is almost alumino-silicate which are highly coordinated. In this type of binder, binding gel is usually low in calcium with high alumina content, so as to form pseudo zeolitic framework rather than formation of calcium silicate hydrate as in the case of ordinary portland cement. The commercial implementation of geopolymer concrete technology is currently being driven by multiple teams consists of materials chemists, civil and infrastructure engineering, practicing engineers, operating in different parts of the world. In India, geopolymer concrete technology is still mostly confined at laboratory levels.This research paper describes the utilization of industrial by-products Fly ash from thermal power plants and granulated blast furnace slag (GGBS) from iron smelting for the full scale production of geopolymeric solid building blocks, with the partnership with leading precast industry. The optimization of process conditions used based on the laboratory and pilot level production by our team and satisfactory performance according to the code specification achieved. Based on the results optimized process operation conditions fixed for full scale production of solid blocks produced at the field conditions. The mechanical strength attainment of 5 MPa meet all of the technical specifications of precast industrial products. [ABSTRACT FROM AUTHOR]

• A one-pat geopolymer was synthesized from alkali-fused lead–zinc tailings. • RSM was used to optimize the preparation of geopolymer precursors. • Synthesized optimum geopolymer sample was used to produce masonry mortar. • The effectiveness of different admixtures in this geopolymer system was evaluated. Currently, various industrial wastes such as tailings and smelting slag are recycled as raw materials in the field of construction. Tailings such as lead–zinc tailings (LZTs) are generally low-reactivity materials. In this study, LZTs were activated through alkali fusion and combined with slag to synthesize a one-part geopolymer. The optimal preparation process, including calcination temperature, alkali consumption, dwell time, and slag content, was determined using response surface methodology (RSM). Subsequently, the optimal geopolymer sample was used to produce a masonry mortar. Influences of the binder–sand ratio and water-reducing admixtures, including polycarboxylate, naphthalene, and sulfonation melamine, on the properties of the mortars were investigated. Based on the results, the geopolymer paste samples produced by activated LZTs (with 20 % alkali added and calcined at 568 °C for 83 min) and 60 % slag content exhibit the optimal compressive strength of 47.2 MPa. Moreover, with a decrease in the binder–sand ratio, the water/binder content required to achieve similar consistency increased continuously; thus, the 28-d compressive strength of the mortar samples reduced significantly from 34.0 to 12.8 MPa. Owing to the incorporated three admixtures, the consistency and 28-d compressive strength of mortar samples were significantly improved; in particular, sulfonation melamine was found to increase these factors by up to 61 % and 95 %, respectively. [ABSTRACT FROM AUTHOR]

• The 1d compressive strength of the sample can reach 24.8 MPa. • The effect of compound activator is better than that of single activator. • Preparation of fly ash geopolymer with Na 2 SiO 3 /carbide slag synergistic wet-grinding. • Compound activators are expected to reduce the use of NaOH activators. • It provides an effective way for the utilization of low calcium fly ash. As the raw material of geopolymer, F-class fly ash (FFA) often needs strong alkali such as NaOH to stimulate due to its low reactivity. In this study, FFA was refined and activated by a wet grinding process, and the activation effect of calcium carbide slag (19 %) and sodium silicate (1 %, 3 % and 5 %) was evaluated when used alone or in combination. The results show that the compound activator significantly improves the hydration products and mechanical properties of the wet-grinding FFA geopolymer. Compared with the single activation system, the 28-day hydration product content of the compound activation (co-activation) system increased by 67 %, and the 1-day compressive strength reached 24.8 MPa (at least an increase of 118 %). In addition, the co-activation system significantly improved the pore structure of the geopolymer and increased the chain length and Al/Si ratio of the C-S-H gel. The results of this study showed that co-activation and mechanical activation can significantly enhance the FFA geopolymer's mechanical characteristics and microstructure, greatly encourage the ingestion of industrial solid waste, lower the application costs of high pH activators, and efficiently provide a method for the utilization of FFA. [ABSTRACT FROM AUTHOR]

This paper presents the concept of industrial symbiosis in which four industries available locally (steel plant, thermal power plant, aluminum plant, and stone quarry) are connected with the concrete industry. By-products generated by these industries (slag, fly ash, red mud, and quarry dust) were activated with a small amount of clinker to form four concrete mixes. The heat of hydration and the autogenous shrinkage were monitored on the fresh concrete mixes. The chloride migration and electrical resistivity of the concrete were measured at different concrete ages over 91 days. Drying shrinkage was monitored for 56 days, and compressive strength was tested after 28 and 91 days. The concrete prepared with a high volume of fly ash, slag, red mud, and quarry dust had very low chloride migration coefficients and less drying shrinkage compared to concrete prepared with ordinary cement. The synergetic beneficial effect of these by-products is explained by their complementary chemistry and particle-size distribution. [ABSTRACT FROM AUTHOR]

• The use of CDP reduced water demand and increased the setting time of paste blends. • CDP improved the early strength of concrete, contributing positively to industrial waste recycling. • Mortar mixtures incorporating up to 50% CDP exhibited comparable 28-day compressive strength to the control mixture. • CDP type and curing procedure have no significant effect on the 28-day strength of concrete. This study evaluated the strength development in hyperalkalized concrete mixtures incorporating cement waste-derived Portlandite (CDP), synthesized from two variants of cement kiln dust (CKD). The source CKDs (coded CKD1 and CKD2) and synthesized CDPs (coded CDP1 and CDP2) were characterized physically and mineralogically, after which the CDPs were used as cement replacement, from 0 to 60 %, in the mortar phase of a base concrete mixture at w/b of 0.5 and 0.425. After in-mold curing, the mortar mixtures were subjected to 12 h of accelerated carbonation curing (ACC), and then moist–cured until 28 days. The strength development and alkalinity of mortar mixtures were investigated using the strength activity factor (SAF) and pH analysis, respectively. The incorporation of more alkaline and fine-grained CKD1 (D50 = 14.74 µm) was found to increase the water demand and setting time of CKD-cement paste blends, compared with the coarse-grained CKD2 (D50 = 27.51 µm). Additionally, the use of CDP reduced water demand but increased the setting time of paste blends. Further, the incorporation of CDP increased the early-age compressive strength of mortar, but its effect diminished as the mixtures matured, with SAF reduction of over 50 % in most cases. Finally, CDP1 mixtures exhibited about 30 % higher early–age compressive strength than CDP2 counterparts but the difference evened out at a later age, with the studied mixtures exhibiting 28-day compressive strengths varying between 23 and 54 MPa. [ABSTRACT FROM AUTHOR]

• The CFBFA-CS-DG ternary composite gelling system can be applied to the preparation of artificial stone. • The compressive strength of the solid-waste-based artificial stone could reach 103.5 MPa at a pressure of 20 MPa, temperature of 90 °C and pressure-stabilising time of 4 h. • The hot pressing (HP) helps to improve the hydration reaction. In order to alleviate the pressure on the environment caused by natural stone mining , for large-scale and high-value utilisation of industrial solid waste and to reduce the production cost of artificial stone, in this study, a solid-waste-based artificial stone was prepared by hot pressing (HP), and the influence of pressing temperature, pressure and pressure-stabilising time on the hydration of the stone were investigated. Using circulating fluidised bed fly ash (CFBFA), carbide slag (CS) and flue gas desulfurisation gypsum (DG) as raw materials, the compressive strength of the solid-waste-based artificial stone could reach 103.5 MPa at a pressure of 20 MPa, temperature of 90 °C and pressure-stabilising time of 4 h,which meets the GB/T 9966.1-2020 'Natural Stone test Methods' compressive strength standard. [ABSTRACT FROM AUTHOR]

• GBFS, UCG and MFASB were used to synthesis the ternary OAGM. • Effects of various factors on flowability, setting time and strength were studied. • Borax is the optimal retarder for the ternary OAGM. • The ternary OAGM with BR has high compressive strength and great flowability. • Reaction product, microstructure and pore structure of different OAGMs were studied. To obtain an environment-friendly grouting material suitable for in situ application, the granulated blast furnace slag (GBFS), uncalcined coal gangue (UCG) and microscopic fly ash sinking beads (MFASB) were used to synthesis the one-part alkali-activated grouting material (OAGM). Firstly, OAGMs with different combination of precursors were prepared respectively, which are GBFS-based OAGM (the unitary OAGM), GBFS/UCG-based OAGM (the binary OAGM) and GBFS/UCG/MFASB-based OAGM (the ternary OAGM). The flowability, setting time and compressive strength of them were measured to analyze their applicability and feasibility in grouting engineering and obtain the OAGM with a reasonable combination of precursors. Next, the effects of different water to solid ratios (W/S ratios), different retarders, and the content of selected retarder on the OAGM were investigated to put forward its rational composition under the best overall performance. Finally, the reaction product, microstructure and pore structure of OAGMs were characterized to probe into their mechanism. Results show that compared with other OAGMs, the ternary OAGM with the retarder borax (BR) has the best overall performance. This material not only has the best flowability and the longest setting time, but also has high compressive strength, thus, it is more suitable for grouting engineering. Microstructural tests reveal that adding UCG and MFASB sequentially into GBFS-based OAGM makes important impacts on the formation of C-A-S-H gel, thus affecting the compressive strength. And adding MFASB into the binary OAGM increases the harmless pores, causing the ternary OAGM has higher porosity. However, the increase of porosity does not necessarily bring about the decrease of compressive strength. Besides, pore structure characteristics shows that adding BR increases the porosity of the ternary OAGM. This study can provide guidance for preparing environment-friendly OAGM suitable for in situ application and promote the recycling of industrial solid wastes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Prediction on compressive strength of ECC through ANN technique. • ANN model trained using Levenberg-Marquardt algorithm. • Effect of SCM on compressive strength of ECC at 28 days. • Correlation of experimental investigation with ANN output. • Validation of ANN model with existing standard benchmark. In recent times, Machine Learning Techniques are emerging continuously as an affordable and efficient in predicting how the property of the materials influences the properties, cost and time of the proposed mixes. In Civil engineering domain, the utilization of ML techniques are need to be strengthened with respect to the incorporation of Supplementary Cementitious Materials (SCM) to the conventional proportioning of mix. Hence to increase the sustainability and thereby reduce the environmental pollution that occurs due to disposal of the Industrial wastes which also holds the pozzolanic property. In this study one of the ML techniques namely Artificial Neural Network (ANN) are used to determine the 28 days compressive strength of the Engineered Cementitious Composite (ECC) incorporated with industrial pozzolans like Fly ash and Ground Granulated Blast Slag (GGBS) with respect to mix proportions and physical properties of polyvinyl alcohol fibres (PVA). The physical properties of fibre and mix proportions such as the ratio of cement, fly ash or GGBS, fine aggregate, water to binder (W/B) ratio, high range water reducer to binder (HRWR/B) ratio, length of fibres, diameter, tensile strength, density, modulus of elasticity and elongation were used to predict the compressive strength of ECC. Furthermore, the experimental investigations were conducted on the compressive strength of ECC with fly ash and GGBS separately and also verified with the ANN outputs. Hence, the present model (Levenberg-Marquardt algorithm) is validated by considering the standard benchmark with respect to the coefficient of determination (R2) which is highly correlated. [ABSTRACT FROM AUTHOR]

The paper studies the effects on the behavior of concrete produced using two major industrial wastes: Fly Ash (FA) and Granulated Blast Furnace Slag (GBFS). There are some works where both FA and GBFS have been replaced individually with cement and fine aggregates. But there are very few studies on the extent of improvement by using FA as cement replacement and GBFS as natural sand replacement in that same concrete mix. In this study, concretes with binary and ternary mixes, including FA as a binder and GBFS as filler constituents, were produced to investigate their effects on the mechanical characteristics of concrete with respect to various replacements and ages. In binary mix, Ordinary Portland Cement (OPC) was partially replaced (20%, 30% and 40%) with FA by weight. In ternary mix, Natural Sand (NS) was replaced 50% by weight with GBFS and again OPC was partially replaced (20%, 30% and 40%) with FA ash by weight in the same mix. Due to the replacement of OPC by FA and replacement of NS with GBFS, the slump was reduced from 9.3% to 25.6%. The test result shows that the binary mix gives up to 32.57% less strength than control mix. But the ternary mix with same FA replacement and 50% GBFS replacement improves the strength by 25.93% in 28 days and 13.93% in 90 days age. The best result achieved in all curing ages for the mix is 40% FA and 60% OPC with 50% NS and 50% GBFS. So, this mix can be used easily and effectively in any kind of normal concrete work. It will make the green concrete much more economical. [ABSTRACT FROM AUTHOR]

Geopolymers are novel, environmentally friendly and economical materials. These materials are produced from industrial wastes, such as fly ash and slag. The geopolymer material used in this study is made from recycled materials, including fly ash and slag, and aqueous solution of NaOH and silicate. All of the specimens are produced using a fixed liquid-to-solid ratio (L/S = 0.5), different ratios of fly ash and slag (fly ash replaces slag by 0%, 20%, 40%, and 60%) and various alkaline solutions (0.5%, 1% and 1.5%). The engineering properties of slump, flow, slump flow, flow time, setting time, compressive strength, ultrasonic pulse velocity and anti-sulfate attack are tested at different curing ages 1, 3, 7 and 28 days. The findings show that when the replacement of fly ash is fixed, the slump value, flow value and slump flow increase with the alkalinity of the solutions. The slump value (98 mm) before replacement with 1.5% alkaline solutions 1.5% is increased by approximately 20 mm compared with different replacements of fly ash. Before the addition of any additive with a slow setting effect, the setting time can be shortened by reducing the alkaline solutions. When the alkaline solution increases from 0.5% to 1.0% or 1.5%, the compressive strength quickly develops. The ultrasonic pulse velocity increases with the addition of alkaline solutions. When alkaline activator 0.5% compared to 1.5% of an alkaline activator sulfate, they get more weight loss. The result shows more alkaline activator, less porosity, higher strength, durability relatively is better. These results are expected to upgrade the technical level of slag-based geopolymer with fly ash to further develop Taiwan’s energy saving, carbon reduction and environmentally friendly recycled admixtures. [ABSTRACT FROM AUTHOR]

• IFA was utilized as a non-toxic waste to produce green ICB products. • Properties of the ICB samples were greatly influenced by the IFA contents. • The effectiveness of the DMDA method for ICB mix design was verified. • Correlations among the properties of the ICB were identified and discussed. The reuse of industrial waste plays a vital role in sustainable development in recent years. In this study, the potential of using the densified mixture design algorithm (DMDA) to utilize waste incineration fly ash (IFA) as a cementitious replacement in interlocking concrete brick (ICB) was investigated. The differences in dimensions, visible defects, engineering properties, and long-term performance of ICB samples produced using different IFA replacement ratios (0%, 15%, 30%, 45%, and 60%) were examined. The results indicate that the IFA replacement level affects ICB properties significantly with increasing levels of IFA replacement associated with decreasing compressive strength, abrasion resistance, bending strength, and bulk density whereas increasing water absorption and void volume. The results of a scanning electron micrograph analysis indicate that higher IFA content is associated with a progressively less-homogeneous microstructure. The effectiveness of the DMDA algorithm was clearly verified, as all of the samples were found to comply fully with relevant Vietnamese standards. The relationships among the tested properties were then established and discussed. The findings of this study prove a promising approach for the combination DMDA algorithm and IFA materials in the production of interlocking bricks adapting sustainable development. [ABSTRACT FROM AUTHOR]

Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils' mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers. [ABSTRACT FROM AUTHOR]

• Using industrial wastes in bricks increases performance and prevents pollution. • Kiln burnt bricks incorporated 2–10% silica fume (SF) and fly ash (FA) as additives. • 4% SF and FA was determined optimal which enhanced strength by 27.55% and 17.36%, respectively. • The addition of SF and FA reduced density, water absorption, and efflorescence. • The additives caused variation in brick dimensions; however, it was within acceptable range. Rapid industrialization over the past few decades has increased the disposal of waste materials in open-air landfills. The utilization of industrial wastes for the preparation of bricks can improve its functional characteristics and reduce the environmental pollution caused by landfill sites. This research investigated the effects of silica fume (SF) and fly ash (FA) on the structural and durability properties of burnt clay bricks (BCB) manufactured at the industrial kiln site. The SF and FA were added to the brick earth with a percentage variation of 2–10%. Results showed that the addition of 4% SF in brick earth increased the compressive strength of BCB by 27.55%, while 4% FA increased the compressive strength by 17.36%. Results also revealed that the addition of SF and FA reduced the weight of BCB, water absorption, and efflorescence while increased the structural efficiency. The incorporation of SF and FA resulted in variation of all dimensions of the burnt clay bricks. Nonetheless, the variation was observed within the range of testing standards. [ABSTRACT FROM AUTHOR]

Downsizing fossil fuel dependence and greenhouse gas emissions is at the forefront of a sustainable future. The expansion of renewable energy while striving to minimize dependence on fossil fuels has led to biomass taking the lead among renewable energy sources, with wood having the broadest application. Along with the growing trend of using biomass as a renewable energy source, the combustion of wood biomass results in wood biomass ash (WBA), leading to compelling amounts of waste. In this study, the technical feasibility of fly WBA from different Croatian power plants was analyzed to evaluate its potential use in precast concrete drainage elements and curb units. By implementing a performance-based design, the influence of various factors in thermal processing of wood biomass was investigated, together with a detailed characterization of WBA in order to assess the feasibility of using WBA as a secondary raw material in a large-scale industrial batching plant. The compressive strength and durability properties (water absorption, permeability, and freeze–thaw resistance) of concrete mixtures with WBA as a replacement for 15 wt% cement were evaluated and compared with the precast concrete manufacturer's technical requirements. The main concerns identified were compositional inconsistency of WBA, workability downturn, delay in initial reactivity rate, and increased water absorption. Concrete with WBA based on a circular design has been found to be a viable solution to cement depletion, stepping up from recycling to reuse of industrial waste. [ABSTRACT FROM AUTHOR]

• Foamed geopolymer was successfully produced from industrial wastes. • Foamed geopolymer consisted of geopolymer binders, unreacted and nonreactive phases. • The factors influencing the mechanical properties of geopolymer were studied. The characteristics of strong alkalinity and concentrated heavy metals make it difficult to dispose and re-utilize Bayer red mud (RM). As for another industrial waste, ZSM-5 (Zeolite Socony Mobil-5) waste is deactivated ZSM-5 catalysts that was formed from the industrial cycles. Herein, a new kind of foamed geopolymer composite (containing various ratios of RM/FA) with micropores was fabricated at elevated temperature from three industrial wastes: Bayer red mud (RM), fly ash (FA) and ZSM-5 waste. The final geopolymer products were characterized by compressive strength tests, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, FT-IR spectral analysis, and mercury intrusion porosimetry to evaluate the relationship between their microstructure, geopolymerization reactions and mechanical properties. ZSM-5 waste has the strong ability to foam because it contains ZSM-5 that possesses numerous mesoporous. The addition of ZSM-5 waste generates a microporous structure. Higher RM/FA ratios generally result in a lower compressive strength owing to the lower reactivity of the RM; however, excessive RM particles may cause the negative effect. The compressive strength in overall decreases from 10.7 to 8.0 MPa and the bulk density increases from 1.04 to 1.26 g/cm−1 with the increased RM/FA ratios of 0.4–1.0, respectively. Microscopic morphology analysis demonstrates that the final products are composites consisting of geopolymer gels and unreacted phases, such as mullite and hematite phases, as fillers. This research can shed light on the utilization and mechanisms of industrial RM and ZSM-5 waste into the construction and building materials. [ABSTRACT FROM AUTHOR]

• Formulated rammed earth mix using pulp mill fly ash as low carbon cementing agent. • Synthesized strong calcium aluminosilicate binder from fly ash by alkali activation. • Combination of non-activated ash and bentonite showed excellent frost resilience. • Cementitious products immobilized toxic elements within the rammed earth matrix. • Study showcases new greener approach to achieve sustainable growth in construction. Sustainable rammed earth (RE) material was formulated using pulp mill fly ash (PFA), an industrial waste product, as an alternative low carbon cementing material. The alkali-silicate activation of PFA in RE showed substantial strength improvement. However, combinations of calcium bentonite clay and raw PFA without activation imparted significantly better frost resilience properties. The recommended RE formulation with 5% PFA, 5% Portland cement and 15% bentonite showed 3.56 MPa compressive strength at 28 days curing and retained 92% strength after 12 freeze–thaw cycles. Further, the leachate analysis revealed that the cementitious reaction products immobilized toxic elements within the stabilized RE matrix. [ABSTRACT FROM AUTHOR]

• Fly ash-cement stabilized CSEBs are assessed in terms of compressive, split tensile, flexural and shear strength. • Inclusion of fly ash is effective to reduce the cement content significantly. • Inclusion of FA ≥ 20% with 5% and 7% cement satisfies the strength requirements. • Fly ash is effective in reducing the accumulated loss of mass. • Life cycle analysis suggest that CSEBs are superior to conventional fired clay bricks. Fly ash is a common industrial waste that requires a proper disposal which otherwise will have a detrimental effect on the environment. As such, utilization of fly ash in producing Compressed Stabilized Earth Blocks (CSEB) can provide suitable means to promote sustainability. Work herein focuses on investigating the performance of CSEBs stabilized with cement and fly ash (FA) as an alternative to traditional construction materials, like Fired Clay Bricks (FCB). Strength characteristics of CSEBs have been evaluated in terms of compressive, split tensile, flexural and shear strength. For durability, accumulated loss of mass due to cyclic drying-wetting test, wet strengths, submersion and efflorescence test have been performed. For this study, 270 CSEBs and 192 cylindrical samples are prepared with 0–10% cement and 0–30% FA (All the percentages are by dry mass of soil taken). Addition of 10–30% FA along with cement increases the compressive strength, flexural strength and split tensile strength by different magnitudes depending on the cement content used. Inclusion of FA ≥ 20% with 5% and 7% cement satisfies the strength criterion suggested by different standards. Moreover, FA was effective in reducing the cement content in the mix without sacrificing the strength. Cyclic drying-wetting test shows that with the increase of the amount of FA with cement, accumulated loss of mass reduces, which is in agreement with the observation of microstructural analyses. Strength retention of the samples after cyclic drying-wetting test ranged within 51–88%, showing the durable performance of cement-FA stabilized earth. Results of triaxial test indicate that FA improves the peak deviatoric stress-strain and failure stress-strain irrespective of cement content and confining stress. With the addition of 0–30% FA with 5% and 7% cement, the cohesion parameter varies within 159–315 kPa, and the angle of internal friction varies within 38.1–57.1°, indicating an improved shear response of cement-FA stabilized mixes. Life Cycle Analysis (LCA) shows that considering energy consumption, Global Warming Potential (GWP) and other environmental impacts, CSEBs are superior to the traditional FCBs. [ABSTRACT FROM AUTHOR]

Modification of a cement matrix using additives and admixtures has been a common practice for many years. The use of some mineral additives as substitutes for the cement, e.g., the siliceous fly ashes (FAs), has a positive effect on reducing the energy used in cement production. On the other hand, such activities may have negative effects due to the lowering of strength parameters of composites in early stages of curing. In order to solve this problem, over the last few years, thanks to the patented "seedings" technology, a branch of industry connected with the production of admixtures that accelerate the binding process has developed significantly. Therefore, the paper presents the results of research aimed at analyzing the parameters of FA cement matrix with the nanoadmixture containing the nanometric C-S-H seeds (nanoadmixture (NA)). By using the modern NA, an attempt was made to neutralize the negative influence of the used industrial waste on the structure of the cement matrix in the early stages of its curing. The paper presents the results of strength tests for the FA cement pastes modified by NA in seven test periods, i.e., after 8, 12, 24 and 72 h, and 7, 14 and 28 days. Additionally, hydration heat tests were carried out on the analyzed material in the first 24 hours of curing. [ABSTRACT FROM AUTHOR]

• Potential of industrial waste fly ash (FA) is studied along with cement for producing earth blocks. • Compressive strength, deformation characteristics, shear behavior, and durability of CSEBs are studied. • Effect of curing time, influence of FA-cement on density and porosity are analyzed. • 6–10% Cement and 20–30% FA provides satisfactory CSEBs in terms of strength and durability. This study is aimed at utilizing industrial waste Fly ash (FA) in combination with cement for production of environment friendly and economically viable Compressed Stabilized Earth Blocks (CSEBs). CSEBs are prepared with four cement contents (4%, 6%, 8% and 10%) and four FA contents (0%, 10%, 20%, 30%) and its performance are assessed in terms of strength and durability. Strength was measured using unconfined compression test, and consolidated undrained (CU) triaxial test; and durability was assessed in terms of water absorption test, wet compressive strength test, and accumulated loss of mass (ALM). Unconfined compression test shows that with the increase of cement, strength of the blocks increases for a definite FA content, however, for a fixed amount of cement, strength increases with addition of certain amount of FA, which is defined as the optimum FA content beyond which strength begins to drop. For 4% and 6% cement, optimum FA content was found 10%, for 8% cement, 20% FA was found to be the optimum content, whereas for 10% cement the optimum FA content is 30%. Deformation characteristics of CSEBs with different cement-FA combinations are analyzed in terms of stress-strain response and modulus of elasticity. Addition of proper amount of FA is found to improve modulus of elasticity, peak and failure strain response for a definite cement content. Moreover, microstructural investigation is carried out to investigate the arrangement of soil matrix for different contents of stabilizers. Optimum content of cement-FA obtained from unconfined compressive strength provide wet-to-dry strength ratio >0.33 which is an indicator of better durability performance. CU triaxial test results show that at a confining stress of 200 kPa and 300 kPa, maximum stress ratio and secant modulus occurs at a mix composition of 8% cement and 20% fly ash, which was considered optimum from compressive strength test scheme. Finally, test results were compared with the specifications of various existing standards and it can be concluded that with addition of optimum amount of cement-FA, CSEBs with acceptable strength and durability response can be produced. [ABSTRACT FROM AUTHOR]

• Fly ash, silica fume, rice husk ash, GGBS and metakaolin were incorporated in mortars. • Cement content was minimized in geopolymer mortars by 80 to 100% by using alkali-activated GGBS. • Compressive strength was improved by activating FA and GGBS with AS of NaOH and Na 2 SiO 3 with AS/ binder ratio = 0.25 in mortars. • The proposed AS of NaOH and Na 2 SiO 3 failed to activate each of silica fume, rice husk ash and metakaolin. Cement industry is one of the industries that contribute to global warming by emitting tons of carbon dioxide. On the other hand, there are lots of industrial wastes that are piling up daily. Therefore, minimizing the use of cement and reducing its negative impact on the environment is our scope. This paper targets to study the effect of alkali-activated pozzolanic materials used as partial or full substitution of cement in mortars cured at ambient temperature. Fly ash, silica fume, rice husk ash, metakaolin, as well as ground granulated blast-furnace slag were incorporated in mortars as cement substitute by ratios varied from 10% to 100% by weight of cement. Alkaline solution of sodium hydroxide and sodium silicate was utilized as activator with activation solution to binder ratio varies from 0.25 to 0.5. Besides, the ratio of sodium silicate to sodium hydroxide was kept 2:1 throughout the study. The results showed the potential of producing high early strength eco-friendly mortars using alkali-activated fly ash and slag as cement substitutions with ratios of 80% and 100% respectively, which is promising for sustainable construction. [ABSTRACT FROM AUTHOR]

• Concrete with cement replaced with waste materials fosters sustainable development. • High volume replacement of PC with pozzolans greatly enhances concrete durability. • The particle size of pozzolans significantly affects its performance in concrete. • GGBS and POFA have superior performance as PC substitutes at high percentages. Increasing urban development has increased the demand for cement and cement production significantly contributes to CO 2 emissions. These emissions are reduced when high volumes of cement are replaced with materials that do not give of high emissions. Sustainable development and considerations for a circular economy fuel the need to find alternative binders in concrete production that reduce the amount of carbon dioxide emissions and utilizes waste materials. Certain industrial wastes (fly ash and ground granulated blast furnace slag), municipal wastes (glass powder and ceramic waste powder) and agricultural wastes (palm oil fuel ash) have been used as a Portland cement (PC) substitute due to their pozzolanic properties. This article discusses the high volume replacement of PC in concrete with these waste materials in terms of the strength development of concrete, its effect on the hydration mechanism, the environmental impact of its use and its relation to alkali cement. [ABSTRACT FROM AUTHOR]

• Suitability of CSEB stabilized with cement and fly ash is assessed in terms of strength and durability. • Inclusion of fly ash is effective in reducing the cement content significantly. • Optimum fly ash content is 15% for 5–7% cement content. • Fly ash is effective in reducing water absorption capacity. • Fly ash and cement stabilized CSEBs are more suitable compared to fired clay bricks from economic standpoint. For saving natural resources, reducing pollution and increasing energy efficiency, Compressed Stabilized Earth Block (CSEB) can serve as a suitable alternative to conventional Fired Clay Brick (FCB). In this study, suitability of industrial waste, Fly Ash (FA) is assessed along with cement as stabilizers for producing CSEBs with coarse grained soil. Different combination of cement and FA (5–10% cement and 5–25% FA; by weight of dry soil) was considered to prepare CSEBs for finding the optimum mix composition in terms of strength, durability, deformation characteristics and cost effectiveness. Furthermore, strength and durability test results are compared to the design criteria reported in Indian Standard, Sri Lankan Standard, Standard Australia, British Standard and Malaysian Standard for assessing its viability as construction material. With the increase in cement content, strength of the blocks gradually increases; however, at a definite cement content, addition of FA increases strength up to a certain limit and then begins to drop. Inclusion of 7–8% cement and 15–20% FA is found to provide adequate dry compressive strength (>5 MPa), wet-to-dry compressive strength (>0.33) and enough durability in terms of water absorption (<20%) as recommended by British Standard and Standards Australia. The behavior of the CSEBs were also analyzed through microstructural investigation, where SEM images were taken to ascertain the morphologic and anatomic changes that occurred at different fly ash contents. At a definite cement content, with the increase of FA, peak strain and failure strain increase; thereby indicating an improved straining capacity of the blocks due to inclusion of FA. Moreover, modulus of elasticity improves with increasing amount of cement and FA for both dry and wet state. Furthermore, economic analysis of a typical house constructed with CSEBs and FCBs was performed and compared with literature. Considering all the parameters it can be concluded that CSEBs prepared with cement and fly ash as stabilizers can be used as a sustainable construction material. [ABSTRACT FROM AUTHOR]

Currently, alkali-activated binders using industrial wastes are considered an environmentally friendly alternative to ordinary Portland cement (OPC), which contributes to addressing the high levels of carbon dioxide (CO2) emissions and enlarging embodied energy (EE). Concretes produced from industrial wastes have shown promising environmentally-friendly features with appropriate strength and durability. From this perspective, the compressive strength (CS), CO2 emissions, and EE of four industrial powder waste materials, including fly ash (FA), palm oil fly ash (POFA), waste ceramic powder (WCP), and granulated blast-furnace slag (GBFS), were investigated as replacements for OPC. Forty-two engineered alkali-activated mix (AAM) designs with different percentages of the above-mentioned waste materials were experimentally investigated to evaluate the effect of each binder mass percentage on 28-day CS. Additionally, the effects of each industrial powder waste material on SiO2, CaO, and Al2O3 contents were investigated. The results confirm that adding FA to the samples caused a reduction of less than 26% in CS, whereas the replacement of GBFS by different levels of POFA significantly affected the compressive strength of specimens. The results also show that the AAM designs with a high volume FA provided the lowest EE and CO2 emission levels compared to other mix designs. Empirical equations were also proposed to estimate the CS, CO2 emissions, and EE of AAM designs according to their binder mass compositions. [ABSTRACT FROM AUTHOR]

A geopolymer is normally considered an environmentally friendly binder due to the utilisation of industrial wastes. This study focusses on the potential of geopolymer preparation at room temperature from landfilled fly ash (LFA) which has been discharged to the land for more than three years. To accelerate the reaction process, 20–30 wt.% LFA was replaced by ground-granulated blast-furnace slag (GGBS). The effect of water glass modulus, Na2O content, water-to-solid ratio, and GGBS content on the setting time and strength development of the binder was discussed. Results showed that to activate LFA, the optimal value of the sodium silicate modulus for alkaline solution was 1.4–1.6 with a Na2O content of 10%, and the water-to-solid ratio was 0.4. In addition, the setting time of the binder reduced with increasing content of GGBS replacement, and the compressive strength increased due to the coexistence of C–(A)–S–H and zeolite-like phases. The maximum compressive strength of the binder was 29.2 MPa after 56 days of curing. The relatively low strength was likely due to the absence of the Q4 unit with a three-dimensional structure. [ABSTRACT FROM AUTHOR]

• High mechanical strength geopolymers were prepared from EMR and fly ash. • The optimal preparation conditions of the EMR-FA were determinated. • EMR-FA were characterized by low leaching toxicity. • The mechanism of geopolymerization was discussed. A large amount of electrolytic manganese residue (EMR) has been produced in electrolytic manganese industry and caused great damage to the environment. In this study, industrial solid waste of EMR and fly ash (FA) were used as solid aluminosilicate raw materials (ASM) to prepare geopolymers with high mechanical strength and good environmental stability. The influences of EMR/ASM ratio, Liquid/Solid ratio (L/S) and curing conditions were studied to guide the production of geopolymers with excellent properties. The results showed that EMR-FA based geopolymer with acceptable compressive strength (16 MPa), good environmental stability and low leaching toxicity can be obtained under the conditions of EMR/ASM = 0.6, L/S = 0.25 and curing at 80 °C for 12 h. The mineral composition of geopolymers was analyzed by X-ray diffraction spectrometer (XRD), which indicated that the geopolymers were mainly amorphous aluminosilicate. By scanning electron microscope and energy dispersive spectrometer analysis, the EMR-FA based geopolymer exhibits a smooth and dense surface of cementitious material with the main elements of silicon, aluminum, calcium and sodium. The geopolymerization was analyzed by Fourier transform infrared spectra and the mechanism was discussed. [ABSTRACT FROM AUTHOR]

Calcium silicate slag (CSS) is an industrial waste residue produced by the extraction of Al 2 O 3 from high-alumina fly ash. CSS, along with cement, is used as a cementing material to reduce land pollution and to utilize industrial waste effectively. The effects of the replacement rate and age of CSS on the compressive strength and hydration degree of the cementitious composite system are examined, and a model for predicting compressive strength is constructed. Results show that the strength and hydration degree of the cementitious composites decrease slightly with the increase in the replacement rate of CSS. When the replacement rate did not exceed 50%, the strengths of the cementitious composites could still reach the 32.5 MPa standard. Microstructural analysis indicated that amorphous C-(A)-S-H, flaky CH, and a small amount of rod-like ettringite (e.g., AFt) made the sample structure compact. The compressive strengths of the cementitious composites were calculated using the response surface method (RSM), and the results show that RSM could predict the compressive strength of cementitious composites accurately. This study shows that CSS can be used as a substitute for cement, thereby providing an effective method for the large-scale utilization of CSS. Image 108752 • A cleaner production approach by effective use of calcium silicate slag industrial waste. • Evaluation of calcium silicate slag cement as partial replacement of cement. • Composite with 30% calcium silicate slag exhibits good compressive strength. • CO 2 emissions and cost of composite cementitious were quantitatively calculated. [ABSTRACT FROM AUTHOR]

• Alkali-activated fly ash cements incorporating soda residue were prepared by compaction. • Compressive strength and water absorption were investigated. • Microscale characteristics of alkali-activated cements at 90d were probed through SEM-EDS, XRD and FTIR. Alkali-activated material, a new eco-friendly alternative to conventional cement binders, has been produced using alumino-silicate material and alkaline activator. Those alumino-silicate material can be formulated by adding natural minerals, waste and /or industrial by-products. This study investigates the mechanical and microstructural properties of alkali-activated cement synthesized from fly ash and soda residue activated by NaOH. The mineralogy phases, microstructure and product compositions were characterized by SEM-EDS, XRD and FTIR. The study reveals that product gels are identified as the coexistence of hydration and polymerization gels containing Ca and Na, which show glassy microstructures in X-ray patterns. The results provide experimental basis for the scientific utilization of SR to an industrial scale. [ABSTRACT FROM AUTHOR]