Alkali-Activated Materials and Geopolymer: a Review of Common Precursors and Activators Addressing Circular Economy

Nodehi, Mehrab; Taghvaee, Vahid Mohamad

doi:10.1007/s43615-021-00029-w

Cited by 133 publications

(71 citation statements)

References 205 publications

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“…However, if strength gain is the engineering target, KOH and in particular K 2 CO 3 , showed a decay in strength when subjected to wetting-drying cycles or when subjected to water curing after 7 days of constant moisture curing. For AAC concrete, exposure in water through water curing has often been reported to result in lower strength gain compared to other curing methods [34,36,48]; this was attributed to dilution linked to reduced pH, and the leaching of the activator [48,56]. For the AAC systems studied here the exposure of the treated soil in water had perhaps similar effects, although most AAC treated samples were found to have pH>10 (the detailed pH results were not shown here for brevity).…”

Section: Discussionmentioning

confidence: 72%

“…GGBS is now a widely used by-product and an established commercially supplied low-cost supplementary cement material (SCM) in blended Portland cements for concrete. GGBS AAC systems for concrete have been shown to have good durability, for instance against sulphate or acid attack, and other chemically aggressive environments [44,48,49]; for ground improvement GGBS has been used in blends with calcium-based soil stabilisers to counteract effects of sulphate-induced heave [50]. There is therefore good potential for the use of GGBS in AAC if the right AAC system is chosen.…”

Section: Discussionmentioning

confidence: 99%

“…The good durability would contribute to the overall sustainability of the AAC soil stabilisation. In terms of supply availability, a global GGBS production of 300 million tons annually has been reported [48], although its established use as SCM in blended Portland cements, in addition to any local trends in the steel industry activities, could place a limit on its availability for AAC, especially as its use as SCM is much more widely understood by industry and hence established, compared to its use in the production of AAC. A major advantage of AAC is the possibility to include a wide variety of waste materials in the binder mix.…”

Section: Discussionmentioning

confidence: 99%

“…The results were also shown to be very sensitive to the composition of the binder mix. Higher molarities or concentrations of activators did not necessarily lead to higher strengths and in fact using too high a concentration of alkaline activator could lead to a reduction in strength, which has been attributed to premature coagulation due to potentially faster dissolution of precursors in the mixture [48]. Case-by-case optimisation of the mixes appears therefore to be required for a successful engineering design and to minimise activator costs.…”

Section: Discussionmentioning

confidence: 99%

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A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

et al. 2021

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In the context of sustainability in the civil engineering industry, chemical ground improvement is becoming increasingly used, as a generally more sustainable alternative to replacing and landfilling unsuitable for construction ground. However, traditional soil stabilisers such as Portland cement or lime are not environmentally impact-free; international research effort is thus focusing on the development of innovative cementing agents. This paper presents results from a feasibility study on the development of suitable alkali-activated slag cements for the stabilisation of two soils. A number of alkali-activators were considered, comprising potassium hydroxide, a range of alkali salts, as well as a material retrieved from waste (Paper Sludge Ash, PSA) which contains free lime. Indicative results of an extensive parametric study in terms of unconfined compressive strength (UCS) are shown, followed by results of ongoing oedometer tests to determine soil compressibility and some preliminary tests on selected soil/binder mixes to observe the durability to wetting-drying cycles. Overall, all alkali-activated cement mixes increased the UCS and stiffness of the soil. Carbonates and Na2SiO3 used on their own gave lower strength increases. The highest strengths were achieved from AAC with KOH and Ca(OH)2 from PSA, which showed similar strength gain. The latter material has shown consistently a lot of promise in terms of strength, stiffness and volumetric stability of the soil as well as treatment durability. Ongoing research focuses on further mix optimisation and a comprehensive mechanical and durability property testing supported by material analysis (mineralogical, chemical and microstructural) to gain a better understanding of the complex mechanisms involved.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

et al. 2021

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“…At present, the research on waste glass concrete, on both national and international levels, is mainly divided into the following parts: In the first group of studies, the ground glass is used as concrete fine aggregate [1][2][3][4][5], while in the second, it is used as inert filling material in concrete [6,7]; the third theme of research is to produce cement as cement clinker, and in the fourth, cement is partially replaced as an auxiliary cementitious material [8][9][10]. It is found that when waste glass is used as aggregate, the mechanical properties of concrete are reduced, mainly due to the existence of a weak interface [11,12].…”

Section: Introductionmentioning

confidence: 99%

Study on the Effect and Mechanism of Alkali–Silica Reaction Expansion in Glass Concrete

et al. 2021

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The suppression of ASR expansion hazards of glass concrete has always been a key and hot issue in the research of glass concrete. According to the ASTM C1260-14 fast mortar rod method, glass sand and glass powder act as fine aggregate and auxiliary cementing material, respectively. The changes in expansion rate with different amounts of glass sand content and different particle sizes of glass powder in mortar rods were compared, and the effects of glass sand content and the glass powder particle size on the expansion of ASR were analyzed. SEM was used to compare and analyze the microstructure of mortar rods to explore the mechanism of ASR expansion of glass concrete, and the results showed that the addition of glass powder had a certain inhibitory effect on ASR expansion. The larger the particle size of glass powder was, the better the inhibition effect on ASR expansion and the longer its duration. Compared with the three groups of experiments of 0–13 μm, 13–38 μm, and 38–75 μm, it was found that the influence of the glass powder particle size on the expansion of ASR was weaker than that of dosage. The inhibitory effect of glass powder on ASR expansion is related to the fact that glass powder is more involved in pozzolanic reaction in the early hydration process.

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The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

Kaya

Köksal

Bayram

et al. 2022

Structural Concrete

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As an alternative to ordinary Portland cement (OPC), alkali‐activated materials (AAMs) have more recently been studied and found to have certain suitability in reducing ecological footprint of OPC binding systems. Nonetheless, due to recent concerns over the availability of certain precursors used AAMs (such as the reduction of coal fly ash availability), this study utilized marble powder in various quantities to replace the naturally available kaolin as precursor. This composite use of natural precursors has been entertained to assimilate the production of carbon zero AAMs. To evaluate the physico‐mechanical and microstructural characteristics of the materials, 48 mixes with different sodium (Na) concentrations, curing temperatures, and marble powder content have been used. The results show that rising curing temperature is more effective than other variables, such as the Na and marble powder content on the physico‐mechanical performance of tested geopolymers. In this regard, it is found that a very high Na content can have adverse effect on the properties, potentially due to altered Na/Si, Na/Al ratio in the mixes. Furthermore, the inclusion of marble powder is found to be effective in decreasing the overall porosity up to ~31% and enhancing the physico‐mechanical properties of the specimens cured at 20 and 80°C. Nonetheless, results show that when specimens containing marble powder are exposed to higher curing temperatures (above 80°C) the presence of marble powder adversely affects physico‐mechanical properties. It is concluded that this phenomenon is caused by the dehydration of chemically bound water in higher temperatures when marble powder is used. This result is further confirmed by microstructural tests.

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Alkali-Activated Materials and Geopolymer: a Review of Common Precursors and Activators Addressing Circular Economy

Cited by 133 publications

References 205 publications

A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

A Study of Innovative Alkali-Activated Binders for Soil Stabilisation in the Context of Engineering Sustainability and Circular Economy

Study on the Effect and Mechanism of Alkali–Silica Reaction Expansion in Glass Concrete

The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

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