Evaluation of short- and long-term properties of heat-cured alkali-activated fly ash concrete

Shekhovtsova, Julia; Kovtun, Maxim; Kearsley, Elsabé P.

doi:10.1680/macr.14.00377

Cited by 26 publications

(4 citation statements)

References 16 publications

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“…Therefore, using aeolian sand and fly ash as the filling materials can not only reduce the amount of waste disposal and disposal costs, but also save cement and reduce the filling cost [12]. Engineering practice has proven that adding fly ash to structural concrete can improve concrete performance, increase concrete strength in the later period, increase the compactness and resistance to concrete, reduce the shrinkage of concrete [13][14][15][16][17], and bring good economic and social benefits [18][19][20]. Therefore, aeolian sand and fly ash are some of the more cost-effective paste filling materials in the Yushenfu mining area, China.…”

Section: Introductionmentioning

confidence: 99%

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Shao

Wang

et al. 2020

Energies

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Backfill mining is the most environmentally friendly mining method at present, which can effectively control the surface subsidence, improve the recovery rate, and has good social and economic benefits. The purpose of this study is to solve the environmental problems caused by solid waste, combined with the rich geographical advantages of aeolian sand in the Yushenfu mining area of China. The rheological properties of the aeolian sand-fly ash-based filling slurry with different fly ash content are studied by experiments, and the strength development law of the filling body under different age and fly ash content are studied from the macroscopic and microscopic points of view. The rheological experiments showed that the increase of the amount of fly ash has a significant effect on the thixotropy, plastic viscosity, and yield stress of the filling slurry. Additionally, rheological properties of aeolian sand-fly ash-based filling slurry conform to the Bingham model. With the increase of the amount of fly ash, the performance of the filling slurry has been significantly improved. Uniaxial test and scanning electron microscope observation showed that the influence of fly ash on the strength of the filling body was mainly reflected in the late stage of maintenance, but was not obvious in the middle stage. Fly ash particles mainly bear the role of “water reduction” and a physical filling effect, which makes the filling slurry thicker and the internal structure more closely spaced. The volcanic ash reaction of fly ash is lagging behind the hydration reaction of cement; the secondary product of the delayed reaction is filled in the pores of cement hydrates, which can greatly reduce the porosity of the backfill body and increase the later strength of the backfill body. It provides a guarantee for the safe replacement of coal pillars in the working face.

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Section: Introductionmentioning

confidence: 99%

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Shao

Wang

et al. 2020

Energies

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“…Investigations about the deformation behavior of low‐calcium FA‐based geopolymer concrete were mostly focused on drying shrinkage after heat curing . So far, deformations during heat curing were rarely investigated.…”

Section: Deformation Of Geopolymer Concrete During Heat Curingmentioning

confidence: 99%

“…Investigations about the deformation behavior of lowcalcium FA-based geopolymer concrete were mostly focused on drying shrinkage after heat curing. [10][11][12][13][14][15][16] So far, deformations during heat curing were rarely investigated. The following deformations can take place during heat curing: thermal deformation caused by a temperature increase or decrease, drying shrinkage due to water loss, an autogenous deformation because of the alkaline activation of the FA and a possible self-desiccation.…”

Section: Deformation Of Geopolymer Concrete During Heat Curingmentioning

confidence: 99%

Investigations on the coefficient of thermal expansion of a low‐calcium fly ash‐based geopolymer concrete

Dehn

2017

Structural Concrete

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In this paper, the deformation of a sealed low‐calcium fly ash‐based geopolymer concrete during heat curing was investigated. The sealed sample underwent thermal deformation due to temperature change and possible autogenous deformation related to alkaline activation of the fly ash. For the separation of the both deformation types the coefficient of thermal expansion (CTE) is a paramount issue. The CTE evolution of the geopolymer concrete from plastic to hardened state was determined by means of a new method proposed in this paper. Based on the experimental results, the CTE is mathematically described as a function of the so‐called equivalent time. The thermal dilation during heat curing was then calculated using the CTE equation. The autogenous shrinkage of the fly ash‐based geopolymer concrete is comparatively low. The thermal dilation during the heat curing cannot completely reverse, if the concrete is cooled down to its temperature at the beginning of the heating. After the heat curing no further autogenous deformation was observed on sealed samples continuously cured at room temperature.

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“…The papers are concerned with early-age performance through to long-term durability, while covering both applied fields and fundamental studies.The first paper, by Shekhovtsova et al (2016), investigates the temperature rise and early-age performance of alkaliactivated fly ash geopolymeric systems; continuing the work of this group in the field of heat-cured alkali-activated systems (Shekhovtsova et al, 2015). They show that the exothermic alkali activation of fly ash geopolymers can affect curing temperatures, especially at high alkali contents or in large samples.…”

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confidence: 99%

Editorial

Black

2016

Advances in Cement Research

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This issue of Advances in Cement Research contains seven papers that span a broad range of topics within the field of cement science; from Portland cement to alkali-activated systems, composite cements and polymer-modified cements. The papers are concerned with early-age performance through to long-term durability, while covering both applied fields and fundamental studies.The first paper, by Shekhovtsova et al. (2016), investigates the temperature rise and early-age performance of alkaliactivated fly ash geopolymeric systems; continuing the work of this group in the field of heat-cured alkali-activated systems (Shekhovtsova et al., 2015). They show that the exothermic alkali activation of fly ash geopolymers can affect curing temperatures, especially at high alkali contents or in large samples. This may have implications for precast geopolymer quality control.The second paper (Santacruz et al., 2016) is a fundamental study into the structure of strätlingite. The work show that the hydration conditions in which strätlingite forms may affect its microstructure; mostly related to the occurrence of dehydration during hydration or sample preparation. Loss of water during certain high-temperature curing regimes is reflected in subtle changes in X-ray diffraction (XRD) patterns, a point of note for those wishing to perform quantitative XRD analysis on systems where strätlingite may be a key phase, such as belite calcium sulfoaluminate cements.The third paper (Zeng et al., 2016) is another fundamental study, this time concerned with accurate determination of the pore structure of cement matrices. The authors have used a combination of mercury intrusion porosimetry (MIP) and nitrogen adsorption to follow changes in the pore structure of cement pastes with age. A combination of the two techniques gave information on the specific surface area, pore volume and pore size distribution. As the authors say 'the hydrates filling process can be best captured by total MIP pore volume and the SSA values are more related to calcium-silicate-hydrate growth'.The next paper (Tasci and Yılmaz, 2016) shifts the focus from later-age properties to early-age performance. The authors have looked at the interparticle interactions between cement particles and pozzolans, performing chemical, physical, mineralogical and electrokinetic analyses of samples. This was coupled with determination of free surface energy components by Van Oss, Chaudry and Good equations.The two final papers look at more applied aspects of cement science, but considering very different timescales. The first of these (Liu et al., 2016) investigates the early-age properties of polymer-modified cements, specifically the effects of asphalt emulsions on cement hydration. In addition to studying asphalt emulsion-cement mixes, the authors also investigated how the individual components affected cement hydration. Overall, hydration was slowed, due primarily to the presence of a cationic lignin-amine emulsifier. The other phases present, non-ionic emulsifier and hydrochloric aci...

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Evaluation of short- and long-term properties of heat-cured alkali-activated fly ash concrete

Cited by 26 publications

References 16 publications

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Investigations on the coefficient of thermal expansion of a low‐calcium fly ash‐based geopolymer concrete

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