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This study investigates the mechanical properties of geopolymer concrete made with ground granulated blast furnace slag (GGBS) and silica fume (SF) as binders. The influence of varying binder proportions and sodium silicate-to-sodium hydroxide (SS-to-SH) ratios of 1.5 and 2.0 in the alkali-activated solution was examined. Experimental tests evaluated slump, compressive strength, modulus of elasticity, and splitting tensile strength at 1, 7, and 28 days. Increasing SF content up to 50% in the binder with a solution ratio of 1.5 improved the 28-day compressive strength by 50% compared to mixes made solely with slag. However, further increase in SF reduced splitting tensile strength and compressive strength by 79 and 56%, respectively, at 28 days. Increasing the solution ratio from 1.5 to 2.0 enhanced compressive strength for slag-dominant mixes by up to 63% but reduced strength for SF-rich mixes by up to 87%. The highest modulus of elasticity, 18.7 GPa, was achieved with slag-only binders and a solution ratio of 2.0, marking a 240% increase over its counterpart mix with a lower solution ratio. Equal GGBS and SF blends improved splitting tensile strength compared to SF-rich mixes but were surpassed by GGBS-rich mixes in terms of overall structural performance.

Incorporation of the waste glass powder (WGP) as an aluminosilicate precursor material in the geopolymer concrete preparation has been researched for the past twenty years as an alternative to the sustainable construction material because of its significant impact on the reduction of greenhouse gases. This paper reviews the various applications of the WGP in the geopolymer matrix production as binary and ternary source material and the impact of the inclusion of WGP on the fresh and hardened characteristics of geopolymer concrete. More research articles associated with the usage of WGP in geopolymer concrete were published in the last ten years. Collective information on the WGP as an aluminosilicate source material in binary, ternary and quaternary blended geopolymer concrete is not available. This review article sums up the newest findings and developments achieved in the synthesis of geopolymer concrete containing WGP as one of the aluminosilicate source material. The study concludes that WGP could be utilized as an innovative and promising eco-friendly aluminosilicate source material to manufacture geopolymer concrete, thereby providing an environmentally eco-friendly solution for the glass and Portland cement based industries.

In this paper, details and results of experimental and predictive studies carried out to determine the mechanical properties of Aluminosilicate materials like Ground Granulated Blast furnace Slag (GGBS) and Fly Ash (FA) based geopolymer concrete specimens are presented and discussed. The major parameters considered in the experimental study are the percentages of GGBS and Fly ash and the percentage of manufactured sand (m-sand) used to replace conventional river sand used in the production of geopolymer concrete. Sodium hydroxide and sodium silicate solutions were used as the activator in the production of geopolymer concrete. The mechanical properties of the geopolymer concrete determined were the compressive strength, split-tensile strength and flexural strength. The test results showed that the mechanical properties of geopolymer concrete improved with increase in the percentage use of GGBS. Also, it was observed from the test results that increase in the percentage use of m-sand increased the mechanical properties of the geopolymer concrete up to an optimum dosage beyond which reduction in the mechanical properties was observed. The predicted mechanical properties of the geopolymer concrete using Artificial Neural Network (ANN) was found to be in good agreement with the test results.

Geopolymer is the product resulting from a geosynthetic reaction of aluminosilicate minerals in the presence of strong alkalis. This communication reports a comparative study on the utility of lower concentration of sodium and potassium hydroxides and alkali silicates at room temperature. The study reveals that the liquid demand is lower for geopolymers with potassium activators. The test results show that potassium activators lower the initial setting time, enhance the reactivity of the components and thereby improve the compressive strength. Sucrose and sucrose with tartrate are attempted as workability and set control aids. Sucrose provided workability in potassium geopolymer but decreased the strength.

This paper aims to perform a comparative investigation on the corrosion protection of steel in the simulated pore solutions of alkali-activated slag (SH) by NO3− and NO2− intercalated Mg-Al layered double hydroxides (MAL) which were fabricated by the calcination rehydration method. The corrosion potential, electrochemical impedance spectroscopy, potentiodynamic polarization and corrosion condition of steel were measured. Furthermore, changes in the microstructures of NO3− intercalated MAL (MAL-N3) and NO2− intercalated MAL (MAL-N2) before and after the adsorption of chloride ion were observed by X-ray diffraction and Fourier transform infrared spectroscopy. The results show that compared to the simulated concrete pore solution (OPCH), MAL-N3 and MAL-N2 exhibit lower chloride adsorption capacities and better corrosion inhibition effects in SH. The chloride adsorption capacity of MAL-N2 is lower compared with that of MAL-N3 due to the different volumes of intercalated anions. In contrast, MAL-N2 presents superior corrosion inhibition than MAL-N3. Furthermore, the decreases in [OH−] in SH due to the additions of MAL-N3 and MAL-N2 are more prominent than those in OPCH. The different synergistic effects due to the competitive anion-exchanges in the interlayers of NO3− and NO2− intercalated MAL in the two solutions contribute to the above effects.

Environmental requirements include sustainable materials with low investment costs and high performance for water treatment applications. The process of hydrothermal carbonization, on the other hand, offers a quick, economical, and green way to transform waste from natural resources into sustainable products. This study aims to produce a novel hydrochar-based material from pomegranate peel using NaOH cold-alkali activation. Extensive physicochemical characterization of the obtained material (NaOH-HCPP) was conducted. To assess the ability of NaOH-HCPP to remove acebutolol (ACE) drug from an aqueous solution, batch adsorption tests were performed, reaching (97.25 mg g−1) under optimal parameters. The isotherm fit best with the Freundlich model, whereas the kinetics were well described by both the PSO and Elovich models, indicating that the process was physicochemical. Moreover, thermodynamic studies stated that acebutolol uptake was distinguished by spontaneity (ΔG° < 0) and exothermicity ΔH° (− 31.91 kJ mol−1). Furthermore, a discussion of the empirical results and further analysis revealed that ACE adsorption onto NaOH-HCPP is controlled by pore filling, van der Waals forces, electrostatic attraction, hydrogen bonding, π–π, and n–π interactions. Thus, NaOH-HCPP has demonstrated high promise for removing acebutolol and possibly other pharmaceuticals from aqueous media.

As the relative performance of alkali activated slag (AAS) concretes in comparison to portland cement (PC) counterparts for chloride transport and resulting corrosion of steel bars is not clear, an investigation was carried out and the results are reported in this paper. The effect of alkali concentration and modulus of sodium silicate solution used in AAS was studied. Chloride transport and corrosion properties were assessed with the help of electrical resistivity, non-steady state chloride diffusivity, onset of corrosion, rate of corrosion and pore solution chemistry. It was found that: (i) although chloride content at surface was higher for the AAS concretes, they had lower chloride diffusivity than PC concrete; (ii) pore structure, ionic exchange and interaction effect of hydrates strongly influenced the chloride transport in the AAS concretes; (iii) steel corrosion resistance of the AAS concretes was comparable to that of PC concrete under intermittent chloride ponding regime, with the exception of 6 % Na 2 O and Ms of 1.5; (iv) the corrosion behaviour of the AAS concretes was significantly influenced by ionic exchange, carbonation and sulphide concentration; (v) the increase of alkali concentration of the activator generally increased the resistance of AAS concretes to chloride transport and reduced its resulting corrosion, and a value of 1.5 was found to be an optimum modulus for the activator for improving the chloride transport and the corrosion resistance.

The very early stages of alkaline activation of slag control its rheology and setting, but also affect its hydration, which occurs later. Simultaneously, these parameters are dictated by the nature and dose of the alkaline activator. Therefore, we investigated and compared the changes in slag particles (SEM, BET, laser diffraction), as well as in the pore solution composition (ICP–OES), pH, and conductivity, of alkali-activated slag (AAS) pastes containing the three most common sodium activators (waterglass, hydroxide, and carbonate) and water during the first 24 h of its activation. To ensure the best possible comparability of the pastes, a fairly nontraditional mixture design was adopted, based on the same concentration of Na+ (4 mol/dm3) and the same volume fraction of slag in the paste (0.50). The results were correlated with the pastes’ hydration kinetics (isothermal calorimetry), structural build-up (oscillatory rheology), and setting times (Vicat). Great differences were observed in most of these properties, in the formation of hydration products, and in the composition of the pore solution for each activator. The results emphasize the role of the anionic groups in the activators and of the pH, which help predict the sample’s behavior based on its calorimetric curve, and offer data for further comparisons and for the modelling of AAS hydration for specific activators.

The purpose of this study is to synthesize geopolymer binders as an environmentally friendly alternative to conventional cement using available local raw materials. Waste materials such as chalcedonite (Ch), amphibolite (A), fly ash from lignite combustion (PB), and diatomite dust (D) calcined at 900 °C were used to produce geopolymer binders. Metakaolin (M) was used as an additional modifier for binders based on waste materials. The base materials were subjected to fluorescence X-ray fluorescence (XRF) analysis and X-ray diffractometry (XRD) to determine chemical and phase composition. A laser particle size analysis was also performed. The various mixtures of raw materials were activated with a 10 M solution of NaOH and sodium water glass and then annealed for 24 h at 60 °C. The produced geopolymer binders were conditioned for 28 days under laboratory conditions and then subjected to microstructural analysis (SEM) and flexural and compressive strength tests. The best compressive strength results were obtained by the Ch + PB samples—more than 57 MPa, while the lowest results were obtained by the Ch + D+A + M samples—more than 20 MPa. On the other hand, as a result of the flexural strength tests, the highest flexural results were obtained by D + A + M + PB binders—more than 12 MPa, and the lowest values were obtained by binders based on Ch + D+A + M—about 4.8 MPa.

In this work, laterite (LA) and rice husk ash (RHA)-based alkali-activated materials (AAMs) with varying %RHA contents (0, 5, 10, 15, and 20%) were prepared for the removal of malachite green (MG) dye from water. The precursors and AAMs were characterized by standard methods (XRF, XRD, TG/DTA SEM, and FTIR). The SEM micrographs and iodine index values showed that the incorporation of RHA improves the microporosity of laterite-based geopolymers. The incorporation of RHA did not result in any new mineral phases after alkalinization. Geopolymerization increased both the adsorption rate and capacity of the geopolymers relative to LA by approximately 5 times. The maximum adsorption capacity was 112.7 mg/g, corresponding to the GP 95−5 (5% RHA) geopolymer. The adsorption capacity was therefore not solely controlled by the RHA fraction. The adsorption kinetics data was best predicted by the pseudo-second-order (PSO) model. The adsorption mechanism entails electrostatic interactions and ion exchange. These results show the suitability of laterite-rice husk ash (LA-RHA)-based alkali-activated materials as adsorbents for the efficient sequestration of malachite green in aqueous solution.