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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]

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]

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 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 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]

• 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]

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]

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]

• 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]