Shrinkage characteristics of alkali-activated fly ash/slag paste and mortar at early ages

Lee, Namkon; Jang, Jeong Gook; Lee, Haeng‐Ki

doi:10.1016/j.cemconcomp.2014.07.007

Cited by 343 publications

(172 citation statements)

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“…A large broad peak is identified at approximately 29 o which has been reported to be poorly crystalline C-S-H (calcium silicate hydrate) type gel [39] and can be difficult to identify [40]. This C-S-H gel type varies according to its calcium/silica ratio [41]. In this case it is likely to be calcium aluminium silicate hydrate (C-A-S-H) or sodium aluminium silicate hydrate (N-A-S-H) gel or a coexistence of both called sodium calcium aluminium silicate hydrate (N-C-A-S-H) gel [42].…”

Section: Mass Lossmentioning

confidence: 99%

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Resistance of geopolymer and Portland cement based systems to silage effluent attack

Aiken

Sha

Kwasny

et al. 2017

Cement and Concrete Research

100

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Abstract:Traditional Portland cement (PC) concrete has been used for many years in the agricultural industry for the construction of silos and silage effluent storage facilities. However, the acidic nature of the silage effluent produced by silage has led to severe degradation of PC concrete which in turn has significant environmental and financial implications. This study compares the resistance of PC and geopolymer (GP) mortars and pastes to silage effluent over 12 months. The GP samples displayed increased resistance to silage effluent in terms of mass and strength loss. Analysis of microstructure suggests that the increased stability of the reaction products is the main factor behind increased silage effluent resistance when compared with PC. It was also found that pulverised fuel ash (PFA) and ground granulated blast furnace slag (GGBS) blends with a higher PFA content may offer increased long term silage effluent resistance due to the nature of the main binder gel produced in PFA dominant systems.

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Section: Mass Lossmentioning

confidence: 99%

“…Furthermore N-C-A-S-H gel may be a hybrid type phase of these gels formed in PFA and GGBS systems [41]. Bound water within the gel structure is removed between 30 and 650 o C [47].…”

Section: Mass Lossmentioning

confidence: 99%

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Aiken

Sha

Kwasny

et al. 2017

Cement and Concrete Research

100

View full text Add to dashboard Cite

show abstract

“…problems cannot be ignored [27,43,44]. Estimating and limiting this volume change is extremely important if the use of AAMs is to spread in civil engineering applications.…”

Section: Shrinkagementioning

confidence: 99%

“…GGBS-FA AAMs (paste [38][39][40][41][42][43], mortar [16,43,44] or concrete [45]) were also investigated. Kumar et al [38] revealed that at 27°C, the reaction of alkali-activated GGBS-FA blend paste is dominated by the GGBS activation (dissolution and precipitation of C-A-S-H) while at 60°C the reaction is due to combined interaction of FA and GGBS, which indicates that FA has lower reactivity than GGBS under ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Samson

Cyr

Gao

2017

Construction and Building Materials

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Highlights AAMs initial setting time, shrinkage, mass loss, compressive strength were studied. Low activation leads to high drying shrinkage because of important mass loss. Very low shrinkage values were found for MK-GGBS compared to the other AAMs. High early strength compressive strength was observed for MK-GGBS blends. Graphical abstract 2 AbstractStudies performed on alkali-activated materials (AAMs) in recent years reveal that they could be an alternative to ordinary Portland cement (OPC). The main precursors used are flash-calcined metakaolin (MK), fly ash (FA), and ground granulated blast furnace slag (GGBS). Usually, only one precursor is used to produce an AAM. The aims of this study were to measure and compare the performances of pure (one precursor) and blended AAMs (two precursors). Alkaline solution is added to activate the precursors and the influence of the activation rate was also investigated by changing the activator amount (15% and 25% of alkaline solution dry extract). Twenty-six different mixes were studied and are presented in a ternary representation. The mixtures were characterized in the fresh state (initial setting time) and the main properties useful for building applications (shrinkage, mass loss, and compressive strength) were recorded and analysed. In contrast to the situation in OPC systems, shrinkage and mass loss in AAMs were not directly correlated. The high shrinkage values observed for pure MK AAMs and pure GGBS AAMs were significantly reduced when they were associated in appropriate proportions. The association of MK and GGBS also proved very interesting regarding early age compressive strength.Keywords: Alkali-activated material (AAM), metakaolin (MK), fly ash (FA), ground granulated blast furnace slag (GGBS), compressive strength, shrinkage 3 IntroductionThe building sector is faced with the gradual exhaustion of natural resources and/or increasing difficulty in accessing them. 27°C, the reaction of alkali-activated GGBS-FA blend paste is dominated by the GGBS activation (dissolution and precipitation of C-A-S-H) while at 60°C the reaction is due to combined interaction of FA and GGBS, which indicates that FA has lower reactivity than GGBS under ambient conditions. There is only small interaction of fly ash and GGBS probably due to different kinetics of dissolution process and distribution of species. Puligulla et al.[39] studied GGBS-FA blend pastes. They found that the calcium that dissolves from slag significantly influences both early and late age properties. The availability of free Ca ions seems to prolong FA dissolution and enhance geopolymer gel formation. It is proposed that the hardening process is initiated by the precipitation of C-A-S-H and that rapid hardening continues due to accelerated geopolymerization. Liu et al. 5The studies mentioned above reveal that, under particular conditions, mixing two different precursors cangive very interesting results. However, these studies have usually focused on the identification of a particular property under particu...

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“…[1][2][3] Many studies have been carried out on AAS to determine its microstructure characterization, 4,5 reaction kinetics, 6,7 and chemical resistance. 8,9 Additionally, the thermodynamic modelling of AAS cements 10 and the phenomenon of AAS composite shrinkage [11][12][13][14] have been studied. The latter has a negative effect on AAS properties, especially in terms of mechanical strength.…”

Section: Introductionmentioning

confidence: 99%

Influence of chemical additives and curing conditions on the mechanical properties and carbonation resistance of alkali-activated slag composites

Bulejko¹,

Bílek²

2017

Mater. Tehnol.

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The main aim of the presented work is to investigate the effect of the addition of air-entraining (AEA) and shrinkage-reducing agents (SRA) on the mechanical properties and carbonation resistance of alkali-activated slag (AAS). The materials used for the sample preparation were blast-furnace slag activated using sodium silicate and AEA or SRA in various amounts. The samples were cured in various conditions (air curing under laboratory conditions and water curing at the same temperature) and the influence of these was also studied. The prepared samples (specimens with dimensions of 100 mm × 20 mm × 20 mm) were tested for compressive and bending strengths. The experimental results show that the addition of AEA did not have a significant influence on the mechanical properties, while the addition of SRA had a negative effect. However, the carbonation resistance markedly decreases with an increase of both agents. The same is true for air curing, as mechanical strengths are lower compared to those samples cured in water, and the ratio of the strength of the air-cured composite and that of the water-cured composite decreases with an increase in the content of SRA. Keywords: alkali-activated slag, carbonation resistance, chemical additives, mechanical properties Glavni namen tega dela je preiskava vpliva dodatka za zmanj{anje vsebnosti zraka (angl. AEA) in dodatka za zmanj{anje kr~enja (angl. SRA) na mehanske lastnosti in odpornost na karbonacijo z alkalijami aktivirane`lindre (angl. AAS). Materiali za pripravo vzorcev so bili plav`na`lindra, aktivirana z natrijevim silikatom in razli~nim dodatkom AEA ali SRA. Vzorci so bili strjeni pri razli~nih pogojih (strjevanje na zraku v laboratorijskih pogojih in strjevanje v vodi pri enaki temperaturi) in {tudiran je bil njihov vpliv. Pripravljeni vzorci, z merami 100 mm × 20 mm × 20 mm, so bili preizku{eni na tla~no in upogibno trdnost. Rezultati preiskav ka`ejo, da dodatek AEA ni imel pomembnega vpliva na mehanske lastnosti, medtem ko je dodatek SRA nanje vplival negativno. Vendar pa se je odpornost na karbonacijo mo~no zmanj{ala z ve~anjem vsebnosti obeh dodatkov. Enako velja za strjevanje na zraku, saj so mehanske lastnosti slab{e v primerjavi z vzorci, strjenimi v vodi in se razmerje trdnosti vzorcev strjenih v vodi in razmerje trdnosti na zraku strjenih kompozitov, zmanj{a s pove~anjem vsebnosti SRA. Klju~ne besede: z alkalijami aktivirana`lindra, odpornost na karbonacijo, kemijski dodatki, mechanske lastnosti

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Shrinkage characteristics of alkali-activated fly ash/slag paste and mortar at early ages

Cited by 343 publications

References 43 publications

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Influence of chemical additives and curing conditions on the mechanical properties and carbonation resistance of alkali-activated slag composites

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