Showing papers on "Geopolymer published in 2017"
TL;DR: The use of fly ash in concrete dates back to the late 20th century and its advantages and disadvantages had been widely researched as mentioned in this paper, however, the level of replacement is still limited to a maximum of 35% of cement by mass.
417 citations
TL;DR: In this paper, the performance of geopolymer concretes manufactured using either class-F fly ash or blended fly ash and granulated lead smelter slag (GLSS) was evaluated.
349 citations
TL;DR: In this article, an industrial robot was employed to print geopolymer mortar in layer-by-layer manner directly from 3D computer-aided design (CAD) model and the characteristic of raw materials and fresh properties were examined by rheology, x-ray diffraction (XRD), and scanning electron microscopy (SEM).
300 citations
TL;DR: In this article, the authors investigated the properties of blended low-calcium fly ash geopolymer concrete cured in ambient condition, and they found that the density of hardened GPC mixtures is similar to that of normal-weight OPC concrete.
295 citations
TL;DR: In this article, the microstructure and strength of metakaolin-based geopolymers were characterized through XRD, SEM, NMR and compressive strength measurements, and the dissolving rates of Al and Si species in geopolymerization were measured, and freeze-dried N-A-S-H gel was characterized by FTIR spectra.
Abstract: Metakaolin-based geopolymers were synthesized at Si/Al ratios of 1:1, 1.5:1, 2:1, 3:1, 4:1, and 5:1 by using silica fume as silica corrector to alter Si ratios. The microstructure and strength of these geopolymers were characterized through XRD, SEM, NMR and compressive strength measurements. The dissolving rates of Al and Si species in geopolymerization were measured, and freeze-dried N-A-S-H gel was characterized by FTIR spectra. Modelling and simulation were employed to calculate the binding energy of one Si atom and the total energy of geopolymers formed at various Si/Al ratios. At Si/Al ratio of 2:1, high concentrations of Si and Al species are dissolved from precursors, high contents of Si-O-T linkages are formed and the geopolymer is of high compressive strength. The mechanical strength of geopolymers at various Si/Al ratios is dependent on the formation of N-A-S-H gel, rather than the zeolitic nuclei or silicate derivatives. This study might provide fundamentals for the geopolymerization of mine tailings, which usually possess high Si/Al ratios.
246 citations
TL;DR: A comprehensive overview of state-of-the-art research on sustainable geopolymers for repairing deteriorated and damaged concrete structures as well as restoring their integrity is provided in this article.
Abstract: Environmentally sustainable repair materials with reduced carbon footprint have been in great demand by the construction industry worldwide. Gradual deterioration of concrete containing large quantities of Portland cement is inevitable, and requires repair or replacement. Numerous repair materials including cementitious mortars, polymer-modified cementitious mortars, resinous mortars, etc. have been utilized to rectify the problem. Cement-free geopolymer mortars prepared from waste materials with high content of silicate aluminum and alkaline activator solution are emerging as prominent sustainable repair materials. Geopolymer binders are preferred because they generate 70–80% less carbon dioxide with remarkably lesser greenhouse gas emissions than ordinary Portland cement. These new binders are highly sought-after due to their enhanced durability performance, sustainability, and environmental affability. This paper provides a comprehensive overview of state-of-the-art research on sustainable geopolymers for repairing deteriorated and damaged concrete structures as well as restoring their integrity. Present challenges and future prospects of various geopolymer mortars as repair materials are emphasized.
243 citations
TL;DR: In this article, an effort has been made to enhance the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag at various percentage levels, which can improve the setting time and compressive strength.
220 citations
TL;DR: In this paper, the Taguchi method has been used to design optimum mix proportions for geopolymer concrete with ground granulated blast furnace slag (GGBFS) as aluminosilicate source at ambient curing condition.
217 citations
TL;DR: In this paper, a review summarizes different types of industrial wastes such as biomass ash, red mud, recycled glass and heavy metals waste, in their application for geopolymer production.
197 citations
TL;DR: In this paper, Ordinary Portland Cement (OPC) was added as additional calcium in the geopolymer system as fly ash replacement (0, 10, 20 and 30%).
196 citations
TL;DR: In this paper, a summary of developments in partially replaced cement composite and geopolymers by industrial by-products along with different nano-materials is presented along with the health related issues on using nano materials and methods can be used to overcome the risks of exposure.
TL;DR: In this article, the effect of silica fume on durability properties of fly ash based geopolymer concrete have been investigated by immersing the cubes in 2% sulphuric acid and 5% sodium chloride solutions.
TL;DR: In this paper, the case of using fly ash and a local high-magnesium nickel slag (HMNS) as solid materials to manufacture geopolymer cement under the room temperature conditions was reported.
TL;DR: In this article, the flexural behavior of fly ash-based geopolymer composites reinforced with different types of macro steel and polypropylene fibers with higher aspect ratio was investigated.
Abstract: Like ordinary Portland cement concrete, the matrix brittleness in geopolymer composites can be reduced by introducing appropriate fiber reinforcement. Several studies on fiber reinforced geopolymer composites are available, however there is still a gap to understand and optimize their performance. This paper presents the flexural behavior of fly ash-based geopolymer composites reinforced with different types of macro steel and polypropylene fibers with higher aspect ratio. Three types (length-deformed, end-deformed and straight) of steel fibers and another type of length-deformed polypropylene fiber with optimum fiber volume fraction of 0.5% are studied. The effects of different geometries of the fibers, curing regimes (ambient cured and heat cured at 60 °C for 24 h) and concentration of NaOH activator (10 M and 12 M) on the first peak strength, modulus of rupture and toughness of the geopolymer composites are investigated. The quantitative effect of fiber geometry on geopolymer composite performance was also analyzed through a fiber deformation ratio. The compressive strength, splitting tensile strength and flexural toughness are significantly improved with macro fibers reinforcement and heat curing. The results also show that heat curing increases the first peak load of all fiber-reinforced geopolymers composites. End-deformed steel fibers exhibit the most ductile flexural response compared to other steel fibers in both heat and ambient-cured fiber reinforced geopolymer composites.
TL;DR: In this article, the effects of silica fume on properties of fly ash-based geopolymer under thermal cycles were revealed, and it was shown that the incorporation of fume improves the microstructure and improves the thermal resistance.
Abstract: This work aims to reveal the effects of silica fume on properties of fly ash based geopolymer under thermal cycles. Geopolymer specimens were prepared by alkali activation of fly ash, which was partially replaced by silica fume at levels ranging from 0% to 30% with an interval of 10%, by mass. Microstructure, residual strength and mass loss of fly ash based geopolymer blended with silica fume before and after exposed to 7, 28 and 56 heat-cooling thermal cycles at different target temperatures of 200 °C, 400 °C and 800 °C were assessed and compared. The experimental results reveal that silica fume addition enhances strength development in geopolymer. Under thermal cycles, the compressive strength of geopolymer decreases, and the compressive strength loss, as well as the mass loss, increases with increasing target temperature. The strength loss is the same regardless of silica fume content after thermal cycles. Microstructure analysis uncovers that pore structure of geopolymer degrades after thermal cycles. The pores of geopolymer are refined by the addition of silica fume. The incorporation of silica fume optimizes the microstructure and improves the thermal resistance of geopolymer. Silica fume increases the strength of the geopolymer and even though the strength loss is the same, the strength after heat cycle exposure is still good.
TL;DR: In order to reduce municipal solid waste incinerator (MSWI) ash, the effect of replacement level of high calcium fly ash by MSWI bottom ash on fly ash based geopolymer properties were studied as mentioned in this paper.
TL;DR: In this paper, the pore structure and shrinkage behavior of metakaolin-based geopolymer pastes and mortars containing 0-30% fly ash were investigated, and it was shown that fly ash substitution decreases average reactivity of the solid precursors, resulting in a lower reaction rate and accompanying longer reaction time.
TL;DR: In this article, the authors compared the performance of AAS concrete and low calcium fly ash geopolymer (FAGP) concretes up to 540 days and found that AAS had higher compressive and tensile strength, elastic modulus and lower permeation characteristics than FAGP concrete.
TL;DR: In this paper, a new geopolymer/alginate hybrid spheres (GAS-4) was fabricated from the green geopolymers and sodium alginate by a feasible one-pot method.
TL;DR: In this paper, the effect of mix design on both reactions is discussed and correlated with the properties of the resulting geopolymer foams, and the mesoscale-based finite element analysis is performed to create a predictive tool for correlating the pore size distribution with their mechanical properties.
TL;DR: In this paper, the authors explored the chloride permeability and initiation of chloride induced corrosion of geopolymer concrete in accelerated chloride environment using longer test period, and showed that the apparent chloride diffusion coefficient of blended fly ash and slag-based concrete is lower than that of OPC concrete.
TL;DR: In this paper, the authors evaluated the life cycle impacts of a geopolymer produced from a kaolin sludge residue from the Brazilian mining industry and found that the use of RHA-derived sodium silicate may reduce environmental impacts by more than 60%.
TL;DR: In this paper, the compressive strength and permeation properties of fly ash-based geopolymer concrete were investigated and the results indicated that compressive strong increased with the increase in OPC content at all ages, with optimum being at 20%.
TL;DR: In this paper, three initial concentrations of NaOH were considered (8, 10 and 12 M) with the aim to investigate on the optimum dissolution and formation of silica oligomers capable to act as binder during the geopolymerization.
TL;DR: In this article, a study on the synthesis of geopolymers based on alkaline activation of waste-glass powder using aqueous solutions of sodium hydroxide and sodium silicate with different Na2O contents as alkali activators was presented.
TL;DR: In this paper, the kinetics of one-part "Just add water" geopolymerisation reaction is studied in the system of fly ash as an aluminosilicate precursor and solid sodium silicate as alkali activator.
Abstract: The kinetics of one-part “just add water” geopolymerisation reaction is studied in the system of fly ash as an aluminosilicate precursor and solid sodium silicate as alkali activator. The rates of the release of Si and Al nutrients from source materials can significantly affect their availability for reaction and their extent of participation in geopolymer gel structure. The crystalline phases that usually appear in fly ash geopolymers are missing in the one-part mix binders studied here, and by increasing the Si/Al ratio the amount of Si contribution in the final geopolymer gel is decreased. The sample with lower water content sees the participation of more Si in both stages of gel formation. Adjusting the composition of raw materials can improve the mechanical properties of the final one-part mix binder. Reasonable mechanical strength with the maximum strength of 65 MPa is achieved.
TL;DR: In this article, the effect of wetting-drying (w-d) cycles on the strength and microstructural changes of RAP-FA blend and RAPFA geopolymer was investigated by unconfined compression strength test.
TL;DR: In this article, the authors investigated the durability of a low-calcium fly ash based geopolymer concrete (GPC) mix in a saline lake environment and found that the particular GPC mix design was more vulnerable to carbonation and the deterioration effects due to chloride and sulphate ingress in GPC were higher than OPC concrete after 6 years of exposure.
TL;DR: In this paper, compressive strength in FA (Fly Ash)-based geopolymer is evaluated considering four test variables covering Na 2 O content, SiO 2 /Na 2 O molar ratios, curing temperature/period, and pre-curing period.
TL;DR: In this paper, the effect of micro-encapsulated phase change materials (MPCM) in solid and liquid states on the mechanical properties and microstructure of geopolymer and Portland cement concretes is investigated.