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This Study is focused on suitability of industrial wastes in cement stabilized soil. The investigation is based on Unconfined compressive strength (UCS) tests. Experimental work is carried out to compare the UCS of cement stabilized soil specimens with different proportion of industrial wastes like Iron ore tailing, Quarry dust, Fly ash and Bagasse ash. The mix proportion is designed such that clay content is maintained at 10.5% for fine grained soil and density of 17.5 kN/m³. It is observed that the mix comprising industrial wastes and fiber have improved the mechanical properties compared to cement stabilized soil. Fiber addition has improved post peak behavior of soil specimen. The Scanning Electron Microscopy (SEM) microstructure images depict soil particle flocculation, leading to an increase in compressive strength and Energy Dispersive X-ray Spectroscopy (EDS) studies suggest the use of industrial wastes with natural soil helps in strengthening of soil cement stabilization, as well as to minimize the environmental pollution. [ABSTRACT FROM AUTHOR]

There are many environmental problems caused by factory waste. Sugar factory waste, in the form of bagasse ash, and PLTU factory waste, in the form of fly ash, are currently in the spotlight of science studies. This study used waste bagasse and fly ash to substitute Portland cement as the main ingredients for mortar. Baggash and fly ash waste were collected, processed, and then used to replace cement by up to 40% to determine to what extent they could be used in brick masonry work, wall plastering, and masonry paste. Experimental tests were carried out on mortar cube samples measuring 5×5×5 cm, comparing four types of samples consisting of Portland cement, bagasse ash, and fly ash. The compressive strength results were obtained after 28 days. Normal Mortar (MN=11.75 MPa) had higher compressive strength than the substitute mortar types MA (3.23 MPa), MB (3.09 MPa), and MC (2.98) MPa. According to SNI 6882- 2014, MA, MB, and MC mortars can be used as O-type mortar (2.4 MPa). Therefore, they can be applied to wall plastering or walls not bearing loads. [ABSTRACT FROM AUTHOR]

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]

Developing of green construction and reducing CO2 emissions in the environment is a priority for industry in the coming years. Recycling fly ash in the concrete industry is a well-known way to reduce environmental impact. Aside from this benefit, there are numerous other positive effects of incorporating fly ash into concrete; however, in this research, the objective is to replace cement with a different percentage of non-class fly ash with high CaO, more than 42%. The analyzed variables are non-class fly ash properties, the effect of fly ash presence on the main properties of concrete and examining the optimum of non-class fly ash in ordinary concrete C-25/30 and high-performance concrete C-50/60. All investigations took place in the laboratory by producing 24 different mix designs and more than 1000 specimens to examine: consistency, setting time, shrinkage, and compressive strength in the short and long terms of curing. Recycling industrial waste in new construction, especially fly ash because of its non-uniform properties, still has some obstacles and is not a practical issue, but the future must be environmentally friendly, and this research proves that the objective of producing sustainable ordinary and high-performance concrete was achieved by replacing 40% of cement with non-class high CaO content fly ash. [ABSTRACT FROM AUTHOR]

In order to improve the high-value utilization of industrial solid waste materials, this study prepared a solid waste-based cementitious material (SWCM) using slag, fly ash, desulfurization gypsum, and gangue. The mechanical strength and hydration process of the SWCM and an ordinary Portland cement (OPC) were studied. The results showed that the compressive strength of the SWCM was lower than that of OPC at 3 d, but the compressive strength exceeded that of OPC after 7 d. The isothermal calorimetry results showed that the induction period of the SWCM was five times that of OPC, and the total 4 d exothermic amount of OPC was 1.7 times that of the SWCM. XRD and SEM showed that the hydration products of the SWCM were mainly ettringite (AFt) and hydrated calcium silicate gel (C-S-H). The unconfined compressive strength and dry shrinkage of stabilized macadam were also studied by using the SWCM to replace OPC. The results indicated that the unconfined compressive strength of the SWCM-stabilized macadam is comparable to that of the OPC-stabilized macadam. The dry shrinkage strain was only 79.7% of the OPC- stabilized macadam. [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]

Industrial waste usage in the technology of construction materials is currently in a relevant and promising direction. Materials made of industrial waste have a lower cost and are highly environmentally friendly. The objective of this study is to develop effective compositions of sulfur concrete based on the maximum possible number of various wastes of the local industry for this and to investigate the characteristics of this composite. Test samples of sulfur concrete were made from sulfur, fly ash, mineral aggregates and bitumen additive. The dosages of fly ash, sand and bitumen varied, while the content of sulfur and crushed stone remained constant. The following main characteristics of sulfur concrete were determined: density; compressive strength; and water absorption. Tests of sulfur concrete were carried out after 1 day and 28 days of hardening. The best values of compressive strength (24.8 MPa) and water absorption (0.9%) were recorded for the composition of sulfur concrete at the age of 28 days with the following content of components: sulfur—25%, modified with 4% bitumen of its mass; fly ash—10%; crushed stone—40%; and sand—25%. The optimal composition of modified sulfur concrete showed compressive strength up to 78% more and water absorption up to 53% less than the control composition. The characteristics of the sulfur concrete samples after 28 days of hardening differ slightly from the values after 1 day of hardening (up to 1.8%). An analysis of the structure confirmed the effectiveness of the developed composition of sulfur concrete in comparison with the control. [ABSTRACT FROM AUTHOR]

In recent years, nano-sized graphene oxide (GO) has come to the fore as a promising material for enhancing the mechanical and durability performance of cementitious composites. On the other hand, partial substitution of industrial wastes and by-products into cementitious composites attracts the attention of researchers in order to ensure long-term sustainability. In order to combine these two aspects, the main focus of this study is to examine the effect of 0.05% and 0.1% GO-reinforcement on the slump, 7 and 28-day compressive and flexural strength and 28-day rapid chloride permeability test (RCPT) properties of cementitious composites. In this context, mixtures with three different binder combinations, a control, a silica fume (SF) substitution, and a fly ash (FA) substitution, were designed. The results showed that GO-reinforcement reduced the slump values of the mixtures between 5-15 mm, while the 28-day compressive strengths increased in the range of 9.82%-13.61% with 0.05% GO-reinforcement, and in the range of 17.02%-20.68% with 0.1% GO-reinforcement. The 28-day flexural strength of the mixtures increased by about 10% on average as a result of 0.1% GO-reinforcement. According to the RCPT anaylses, it was observed that the chloride permeability of the mixtures decreased up to 18.85% with 0.1% GO-reinforcement. [ABSTRACT FROM AUTHOR]

Fly ash is a massive industrial waste. Owing to the abundance of oxides, such as SiO2 and Al2O3, fly ash is considered a high value material. In this study, we assessed its application in the industrial deoxidation of nitrogen oxides, a major environmental pollutant, using the selective catalytic reduction technology. Fly ash was used as the main raw material and bentonite was used as an auxiliary material in the catalyst. Silica sol, starch, and glycerol were added to improve the compressive strength and denitrification performance of the catalyst. The use of silica sol as a binder improved the compressive strength of the catalyst due to the production of Si–O–Si. In addition, the availability of acidic functional groups could improve the denitrification performance of the catalyst. The optimal dosages of the additives were as follows: 6% silica sol, 6% starch, and 5% glycerol. Under these conditions, the catalyst formation was the easiest, the cracks were the least, the compressive strength of the catalyst reached 1434 kPa, and the denitrification performance improved. The findings presented here are relevant for the development of an economical and practicable solution for tackling environmental pollution caused by nitrogen oxides. [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]

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]

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]

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Concrete is the most used construction material in the world. Sustainable construction practice demands durable material. A particular type of concrete that flows and consolidates under its weight is proposed to reduce labor dependency during construction, called self-compacting concrete. It is installed without vibration due to its excellent deformability and flowability while remaining cohesive enough to be treated without difficulty. Evaluating its compressive strength is essential as it is used in important construction projects. An artificial neural network (ANN) is a predicting tool that can predict output in various sectors. This study evaluated the compressive strength of industrial waste such as fly ash and silica fume incorporated in self-compacting concrete at various ages. A non-linear relationship was used to develop the model relating mix composition and SCC compressive strength using an Artificial Neural Network (ANN). The experimental and expected outcomes were compared with the model prediction to evaluate the predictive capacity, generalize the generated model, and observe suitable matches. The developed ANN network can predict the desired output, i.e., compressive strength incorporating industrial waste. Furthermore, the influence of individual parameters viz. cement, silica fume, and fly ash, w/b were also evaluated using parametric analysis, which shows the sensitivity of various materials on the compressive strength of Self-compacting concrete. As a result, a higher correlation coefficient of 0.9835 with a smaller value of MAPE (0.0347) and RMSE (2.4503) is obtained. Finally, a process of creating tools for practical engineers and field users is proposed, which would be very handy and fast for predicting the strength of SCC. [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]

Due to increased global warming, the need to find an alternative to conventional cement concrete has increased in the construction industry as cement is known to consume natural resources and lead to higher carbon emissions for its production. This research paper examines the technical feasibility of using silica fume as an admixture to develop the M30, M50 and M70 grade geopolymer (GP) concrete by varying the proportions of industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBS), lowering the concentration of the alkali activator solution and including silica fume (SF) in the fly ash (FA) admixture. Based on their mechanical behaviour, the mix design was optimized for M30, M50 and M70 grade GP concretes. The results demonstrated that the maximum compressive strength (CS) of fly ash and GGBS based GPC at the age of 28 days varies from 38.64 to 57.24 MPa, whereas those of silica fume blended GPC achieved up to 78.57 MPa, was achieved at 70:30 FA:GGBS composition, when the concentration of alkali activator added is 3.5 M and liquid by powder (L/P) ratio is 0.6 for M30 grade GP concrete; at 70:30 FA:GGBS composition, when the concentration of alkali activator added is 5 M and L/P ratio is 0.47 for M50 grade GP concrete; and at 65:30:5 FA:GGBS:SF composition, when the concentration of alkali activator is 5 M and L/P ratio is 0.49 for M70 grade concrete. Using a scanning electron microscope (SEM-EDAX) and X-ray diffraction analysis (XRD), the microstructure of the modified mixtures was analysed and correlated with mechanical properties. Our analysis revealed that the addition of SF enhanced gel formation by increasing the reactivity towards alkali and filling the pores that ultimately resulted in enhanced strength characteristics, which was also confirmed through SEM. It can be concluded from the results that the addition of SF admixture for the strength improvement of GP concrete is technically viable. [Display omitted] • Optimization of mix design for GP concrete M30, M50 and M70 grades. • Increasing the molarity of solution has positive impact on mechanical strength. • SF enhanced the strength by availing the reactive species in the mixture. • Microstructure changes are matched with the strength results. • GP concrete slabs has tested for deflection characteristics. [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]

Natural and artificial pozzolans are widely used in building materials and play an increasingly important role in minimizing costs and mitigating environmental effects in the manufacturing of building materials. These pozzolans can be obtained as by-products from various industries, generally they are wastes without any application or added value. However, when implemented in cement mixtures, their effectiveness is somewhat questionable. Therefore, it is necessary to determine the properties, characteristics, and behavior of these materials. This study aims to summarize the main pozzolans used in building materials. Volcanic pozzolans, pozzolans of sedimentary origin, fly ash, blast furnace slag, silica fume, metakaolin, ceramic wastes, demolition, and construction wastes, rice husk ash, bagasse ash, biomass ash, and paper sludge were considered. The chief characteristics studied were particle size, specific area chemical composition, and mineralogical composition. In addition, the impact on mechanical properties and durability in cement mixtures using pozzolans was analyzed. It was observed that the mechanical properties of cement mixtures change by increasing pozzolan replacement. The maximum percentage of replacement depends on the characteristics of the pozzolan. In the case of durability, pozzolans decrease absorption and permeability by reducing the porosity of the binder. This decreases acid diffusion and autogenous shrinkage, thus improving concrete durability. Finally, future studies are suggested to consider the implementation of artificial intelligence techniques and machine learning algorithms to improve the properties of the concrete mixtures. [ABSTRACT FROM AUTHOR]

Pozzolan has been widely used as a supplementary cementitious material to improve concrete properties such as workability and shrinkage. Bagasse ash (BA) is an industrial waste that has pozzolanic properties like fly ash (FA), but its cost is relatively lower. Research conducted on concrete mixed with BA (CBA) were primarily on the properties of CBA, investigation on the bonding strength of steel rebars in CBA was still limited. This paper aims to investigate the effect of BA on the overall bonding strength of reinforced concrete using a pull-out testing method. Based on the range of the parameters considered in the present work, the results revealed that the bonding strength was inversely proportional to the BA content in concrete. The bonding strength of rebar in CBA was compared with that in ordinary cement concrete. It was found that the bonding strength of rebar in CBA was lower than that in concrete without BA at 28-day age. When the concrete age was more than 90 days, and BA content was not greater than 20% cement replacement, the difference in the bonding strength was insignificant. This outcome indicates that the current standard for designing the development length of rebars in CBA is still valid when the BA content is not greater than 20% of the cement. Further experiments are required to investigate any size effect. [ABSTRACT FROM AUTHOR]

The utilization of waste industrial materials such as Blast Furnace Slag (BFS) and Fly Ash (F. Ash) will provide an effective alternative strategy for producing eco-friendly and sustainable concrete production. However, testing is a time-consuming process, and the use of soft machine learning (ML) techniques to predict concrete strength can help speed up the procedure. In this study, artificial neural networks (ANNs) and decision trees (DTs) were used for predicting the compressive strength of the concrete. A total of 1030 datasets with eight factors (OPC, F. Ash, BFS, water, days, SP, FA, and CA) were used as input variables for the prediction of concrete compressive strength (response) with the help of training and testing individual models. The reliability and accuracy of the developed models are evaluated in terms of statistical analysis such as R2, RMSE, MAD and SSE. Both models showed a strong correlation and high accuracy between predicted and actual Compressive Strength (CS) along with the eight factors. The DT model gave a significant relation to the CS with R2 values of 0.943 and 0.836, respectively. Hence, the ANNs and DT models can be utilized to predict and train the compressive strength of high-performance concrete and to achieve long-term sustainability. This study will help in the development of prediction models for composite materials for buildings. [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]

Manufacturing waste has been quickly increasing over time as a result of the fast-rising population as well as the consumption of foods that are thrown away dishonestly, resulting in environmental contamination. As a result, it has been suggested that industrial waste disposal may be considerably reduced if it could be integrated into cement concrete manufacturing. The aim of this study is to analyze the properties of concrete employing waste glass (WG) as a binding material in proportions of 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. The fresh property was assessed using a slump cone test, while mechanical performance was assessed using flexural, compressive, splitting tensile, and pull-out strength after 7, 28, and 56 days. Furthermore, microstructure analysis was studied by scan electronic microscopic (SEM), Fourier-transform infrared spectroscopy (FTIR) and thermo-gravimetric analysis (TGA) test. The results reveal that the addition of discarded glass reduces the workability of concrete. Furthermore, mechanical performance was increased up to a 20% substitution of waste glass and then gradually declined. Waste glass can be employed as a micro filler or pozzolanic material without affecting the mechanical performance of concrete, according to microstructure research. [ABSTRACT FROM AUTHOR]

Featured Application: This work aims to further decrease the environmental footprint of alkali-activated materials by using an industrial wastewater to partially replace a commercial activator. Alkali-activated materials are generally considered a more sustainable alternative to Portland cement binders. This derives not only from the use of solid wastes as precursors, but also from the low temperatures required for their synthesis. However, to increase the environmental advantages of these materials, alternative activators should be explored, as the common route involves the use of commercial activators such as sodium silicate or sodium hydroxide solutions. In this work, the possibility of using an alkaline industrial wastewater, coming from a Portuguese paper and pulp industry, as a partial replacement of the commercial sodium hydroxide solution was studied. The results show that the use of the industrial wastewater decreased the workability of the pastes and their setting times, higher incorporations inducing a stronger reduction. Despite this, the results demonstrate the feasibility of replacing up to 25 vol.% of the sodium hydroxide solution with the industrial wastewater without compromising the mechanical performance of the binder. The compressive strength of this composition reached 22.7 MPa, this being slightly higher than the value seen in the reference (20.0 MPa). The use of a waste-containing activator, as reported here, might be a key driver to foster the wider use of this technology. [ABSTRACT FROM AUTHOR]

Three-dimensional concrete printing is a promising technology and attracts the significant attention of research and industry. However, printable and mechanical capacities are required for 3D printable cementitious materials. Moreover, the quantitative analysis methods of printable performance are limited and have low sensitivity. In this study, the orthogonal experiment through samples combining 3D concrete printing method with fly ash, silica fume, and ground granulated blast furnace slag was designed to obtain the printable and mechanical property influence of various mix proportions. Furthermore, multiple industrial wastes were utilized to improve material sustainability. Meanwhile, the static and dynamic extrusion pressure measured by the original 3D printing extrudability tester were verified to achieve a high-sensitivity evaluating indicator. Thereby, a novel high-sensitivity quantitative analysis method of printable capacity was established to explore the influence of industrial wastes usage on the printability of 3D printable mortars. The optimum dosage of fly ash, silica fume, and ground granulated blast furnace slag was 20 wt.%, 15 wt.%, and 10 wt.%, respectively, based on printable and mechanical property experiments. Furthermore, the optimum dosage was employed to print the sample and achieved a higher compressive strength (56.3 MPa) than the control cast. [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]

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]

Geopolymer is a renewable construction material that reduces dependence on ordinary portland cement (OPC), where OPC manufacturing impacts carbon dioxide (CO2) emissions. The main aspect of geopolymers being studied is the precursor of pozzolanic material, used as a cement substitute because it contains aluminosilicate (Si-Al). Polymerization occurs between the precursors, reacted by alkaline activator solution (AAS). Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as AAS. In this study, local precursors from industrial waste and biomass were utilized. Fly ash was employed as a reference in the precursor by 5% - 10% substitution of glass powder, rice husk ash, bagasse ash, and palm shell ash. Moreover, 2% superplasticizer and 5% extra water were used to increase the flowability of fresh geopolymer. Tests were carried out on the setting time of paste, flow table, and compressive strength of geopolymer mortar. The tests were on the initial setting time of 25-75 minutes and the final setting time of 40-115 minutes. The setting time results revealed that the time of each substitution accelerated geopolymerization due to the substitution of precursors containing higher CaO and SiO2. Setting time and flowability/workability had a linear regression correlation (R2) of 0.95, with the flow table ranging from 180-250 mm. The compressive strength ranged from 25.88 - 36.36 MPa through a curing temperature of 70oC for 24 hours, followed by curing at ambient temperature for up to 28 days. [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]

Concrete is one of the most utilized and preferred construction materials in almost all the regions of the world. It is mainly known for its compressive strength. Several megastructures such as bridges, spillways, high-rise buildings, dams, etc. require sufficient compressive strength to suitably bear the upcoming large load on them. At the same time, in recent years, a lot of industrial by-products that are dumped as an industrial waste have attracted attention on concrete technologists. To safeguard the land from becoming the dumping zone/landfill sites, several researchers have come up and utilized these wastes as a supplementary cementitious material (SCM) in concrete. These SCMs can be used either in addition or in replacement of cement. In this paper, the effect of varying particle size and proportion of SCMs on compressive strength of concrete has been reviewed. Efforts have been made to showcase the effective utilization of various industrial by-products in manufacture of concrete with comparable compressive strength. [ABSTRACT FROM AUTHOR]

Geopolymer concrete is an eco-friendly concrete as it produces less CO compared to ordinary Portland cement. The 2 scarcity of natural river sand has led to many investigations to find a substitute for fine aggregates. Pond ash which is an industrial waste, has been used as substitution for fine aggregates. The current paper investigates effect of pond ash gradation on mechanical properties of geopolymer concrete by ANN and MLRA analysis. Various data samples collected from literature were fed into ANN and MLRA tool box in MATLAB and Microsoft Excel respectively to obtain the strength predictions. The outcomes of analysis of ANN and MLRA model showed that ANN and MLRA results match well with experimental data from literature. The predicted strength results of geopolymer concrete having pond ash belonging to zone II exhibited better strength properties than geopolymer concrete having pond ash belonging to Grade I, III and IV. [ABSTRACT FROM AUTHOR]

The need to reduce the global anthropogenic carbon dioxide has encouraged researchers to search for sustainable building material. The second most consumed product in the world is concrete. Cement contributes 7% of the global carbon emission. Geopolymer Concrete (GPC) which is manufactured using industrial waste like fly ash, Ground Granulated Blast Furnace Slag (GGBS) is becoming a more eco-friendly alternative to Ordinary Portland Cement (OPC) concrete. The objective is to study the fly ash and GGBS on the mechanical properties of geopolymer concrete at full replacement of cement. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution have been used as alkaline activators. The effect of replacement of cement with fly ash and GGBS at varying percentage on strength of geopolymer concrete is studied. Additionally, the feasibility of production of geopolymer concrete using fly ash and GGBS is also evaluated in this study. In the present investigation, it is proposed to study the mechanical properties viz. compressive strength and split tensile strength of fly ash-GGBS based geopolymer concrete. These properties have been determined at curing periods 7 & 28 days and at ambient room temperature. From this study it is concluded that full replacement of cement with fly ash and GGBS gives good strength properties. The maximum compressive strength is observed to be attained at full replacement of cement by fly ash and GGBS having a proportion ratio of 1:1 which is more than the optimum mix in full replacement had an increase in cost than the conventional mix. However, with respect to its strength characteristics it still economical. From these conclusions we can say that, it will be a good initiative to give a solution for solid waste disposal as well as to reduce the CO2 emission generated during the process of cement manufacturing. [ABSTRACT FROM AUTHOR]

Fact that the large-scale dumping of the mining and industrial waste causes various environmental impacts and health issues in human and animals. It is necessary to use the wastes in an effective manner to prevent such environmental problems. Fly ash and iron ore tailings are the two major wastes of such kind. Even though these two wastes are being used in various sector, the utilization of these waste is less than the waste generated. This study mainly concerns with the usage of fly-ash and iron ore tailings in construction industry in sustainable manner. Geopolymer coarse aggregates are synthesized by using the fly-ash and iron ore tailing with alkaline activator solution which activates geopolymeric source. The cubes of side 75 mm x 75 mm x 75 mm are prepared by mixing fly-ash and IOT in 70:30 proportion respectively with varying molarity of alkaline activator as 6M, 8M, 10M up to 12M. Compression test are carried out on the prepared cubes. It has been observed that as the molarity of alkaline activator increases, the compressive strength also increases. 10M of Alkaline activator is used for the synthesis of geopolymer coarse aggregates. Aggregates are prepared by crushing of cubes. XRD and SEM analysis are preferred for the characterization of raw materials. [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]

The increase of carbon emissions due to the annual growth of portland cement (PC) production has promoted research into the development of sustainable green concrete using a range of readily available industrial waste materials. The present study is focused on developing two high-volume fly ash (HVFA) concretes with cement replacement levels of 65% (HVFA-65) and 80% (HVFA-80). The required lime for both HVFA concrete mixtures was initially determined and the optimized mixture designs identified, based on the 28-day compressive strength, by varying the low-calcium Class F fly ash-hydrated lime composition. The optimized concrete mixtures achieved a compressive strength of 53 and 40 MPa (7.69 and 5.80 ksi) for HVFA-65 and HVFA-80 concretes, respectively. The early-stage strength development is dependent on the matrix produced in the specific HVFA concrete, which is itself dependent on the number of unreacted fly ash spheres. The increase of fly ash and hydrated lime dosage in HVFA concrete increases the rate of hydration of the C3A and C4AF phases, but decreases the hydration of the C3S phase, which resulted in lower early-age strength development than occurs in PC concrete. It was noted that the initial setting time of HVFA concretes increase with an increase of fly ash content. However, addition of hydrated lime accelerates the hydration and decreases the final setting time for HVFA concretes. [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]

Mineral carbonation for concrete curing is a promising route to large‐scale CO2 sequestration and the economic production of building materials. In this work, the carbonation curing of a kind of lightweight concrete, aerated concrete, was comprehensively studied. Three typical industrial wastes – fly ash, blast furnace slag, and red mud – were employed to replace part of the cement and to reduce the carbon footprint of products. The effects of carbonation curing time, pressure, and water‐to‐solids ratio on the CO2 uptake and compressive strength were investigated. Aerated concrete with red mud showed the highest CO2 uptake capacity, followed by concrete with fly ash, and concrete with blast furnace slag. The main crystalline carbonation products, needle‐like calcite and rod‐like aragonite, were observed to be embedded in the surface of fly ash and blast‐furnace‐slag‐based specimens. The orderly structures of carbonated crystals, as well as the reduction of mesoscale porosity (< 50 nm), resulted in an enhancement of mechanical properties. For red‐mud‐based specimens, calcite crystals with the appearance of grains (smaller than 1μm) were formed due to deeper carbonation. The rapid growth of calcite grains may lead to cracks from inside red‐mud‐based specimens and cause a negative effect on mechanical properties. In terms of mechanical performance, the blast furnace slag specimens, after carbonation curing, exhibited the largest compressive strength of 7.3 MPa, which was over 197% higher than that of natural curing for the same duration. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. [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]

[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]

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]

• 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]

• 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]