Effect of calcium oxide on mechanical properties and microstructure of alkali-activated slag composites at sub-zero temperature

Ju, Cheng; Liu, Yushi; Jia, Minjie; Yu, Kunyang; Yu, Zhenyun; Yao, Yang

doi:10.1016/j.jobe.2020.101561

Cited by 20 publications

(9 citation statements)

References 29 publications

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“…In this case, the strength contributing factor is the CaO in addition to the CaCO3, which contributes to a slight increase in the strength development up to a certain limit [135,136] while the Ca(OH)2 does not affect the strength [137]. This additional CaO accounts for more heat of hydration at an early stage due to its exothermic reaction with water [14,138]. Also, adding a given CES consisting of free CaO in the binder matrix can increase the strength of the concrete by improving the Hydraulic Modulus (HM) and Lime Saturation Factor (LSF) [139].…”

Section: Role Of Calcium Oxide In Strength Development In Mixes With Cesmentioning

confidence: 99%

Eggshells from Different Countries of Origin and Their Sustainable Application as a Partial Replacement of Cement

Maqsood,

Eddie,

et al. 2023

Preprint

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This study aims at the sustainable valorization of eggshells (ES) from different countries of origin in cement concrete as a cement replacement. For this purpose, sixteen different eggs from different regions across the world were selected. Firstly, the extent of uniformity in the weight and mineral content of sampled eggshells was assessed by a specific gravity test and thermogravimetric analysis (TGA), respectively. It was found that specific gravity varies between 2.02 – 2.39, having an average value of 2.20 ± 0.01, whereas the CaCO3 varies between 94.65% - 97.23%, having an average value of 96.33%. These values were a bit lower than extra-pure limestone (LS) because of having organic part and the porous structure of eggshells. Secondly, three different eggshells were selected for cement replacement in cement concrete both in the uncalcined and calcined state based on having the highest, medium, and lowest CaCO3 content, respectively. To get the calcined eggshells, the eggshells were calcined at 800oC for three hours. It was found that the strength of eggshells varies with the CaCO3, but the variation was acceptable. The calcined eggshells showed comparatively more compressive strength and were close to the LS because of free CaO and the absence of an organic part. In general, the variation in the basic properties of eggshells from different regions across the world is negligible and is suitable for use in as a cement replacement with acceptable variation in the strength.

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Section: Role Of Calcium Oxide In Strength Development In Mixes With Cesmentioning

confidence: 99%

Eggshells from Different Countries of Origin and Their Sustainable Application as a Partial Replacement of Cement

Maqsood,

Eddie,

et al. 2023

Preprint

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“…Moreover, these prototypes not only increase the total cost of production but also account to add in total CO 2 emissions. The most effective and economical alternative is to use accelerating and/or antifreeze chemical admixtures, which accelerate hydration and increase the early strength, thus preventing the mixing water from freezing and reducing the internal pressure of expanding ice [11,[19][20][21][22][23]. Antifreeze agents commonly react with calcium hydroxide to form hydroxy salts, which change the pH and ionic strength.…”

Section: Introductionmentioning

confidence: 99%

Early Age Performance of OPC-GGBFS-Concretes Containing Belite-CSA Cement Cured at Sub-Zero Temperatures

Kothari,

Buasiri,

Cwirzen

2023

Buildings

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This study determined how replacing sodium nitrate-based antifreeze admixture (AF) with belite-calcium sulfoaluminate (belite-CSA) cement affects the early age properties of ecological concretes based on ordinary Portland cement (OPC) and ground granulated blast-furnace slag (GGBFS). Concrete specimens were cured at −15 °C and treated in various ways before testing, i.e., no treatment, stored at 20 °C for 12 and 24 h. Generally, the addition of belite-CSA cement shortened the setting time due to the rapid formation of ettringite. The incorporation of 25 wt% of antifreeze admixture (AF) to the OPC-GGBFS concrete cured at −15 °C partially inhibited ice formation and enabled the continuation of hydration processes. This trend was observed for all samples, independent of the applied AF after freezing curing. On the contrary, the addition of 20 wt% of CSA failed to inhibit the ice formation and increased the risk of frost damage for concretes despite the treatment after freezing. These concrete specimens had lower hydration, lower strength, and a more porous binder matrix. The microstructure of the binder matrix was significantly affected by the amount of CSA and extreme negative curing, followed by no notable recovery post-curing at room temperature. Therefore, pre-curing at room temperature for at least 6 h has the potential to avoid frost damage. Concrete containing 25 wt% AF combined with 12 h and 24 h of curing at 20 °C after removal from freezing and prior to testing could enhance the compressive strengths of all concretes. The renewed hydration was indicated as the main influencing factor.

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“…In theory, this makes it feasible to produce AAS pastes at lower temperatures [18]. Various studies have demonstrated the feasibility of using AAS at low temperatures [1,5,19,20].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Polypropylene Fiber Addition on the Compressive Strength and Ultrasonic Pulse Velocity of Low-Temperature Cured AlkaliActivated Slag

2023

International Conference on Innovative Academic Studies

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Portland cement (PC) has long been a predominant binder material in the construction industry, but it is also a major contributor to carbon dioxide emissions. Alkali-activated materials (AAMs) have emerged as an environmentally friendly alternative in the construction industry. AAMs are formulated by activating aluminosilicate-based materials with alkali activators, offering potential environmental benefits by reducing carbon dioxide emissions compared to traditional PC-based binders. Due to its ability for continuous hydration at low temperatures, alkali-activated slag (AAS) stands as a promising binder material for winter construction applications. High alkali dosage (Na2O%) dosage and alkali modulus in AAS production may result in the occurrence of shrinkage cracks. This study employed 0.3% polypropylene fiber (PP) by volume to mitigate the potential negative impact of cracks, which may arise from elevated Na2O%, on the mechanical properties of AAS. AAS mortars were manufactured with Na2O% of 7% and 9%. Ultrasonic pulse velocity and compressive strength tests were conducted on samples aged 7 and 28 days. The results showed that the compressive strength increased with an increase in Na2O%. The sample with 7% Na2O% exhibited better strength development with increasing curing time compared to its 9% counterpart. There was a decrease in compressive strength with PP substitution.

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Effect of calcium oxide on mechanical properties and microstructure of alkali-activated slag composites at sub-zero temperature

Cited by 20 publications

References 29 publications

Eggshells from Different Countries of Origin and Their Sustainable Application as a Partial Replacement of Cement

Eggshells from Different Countries of Origin and Their Sustainable Application as a Partial Replacement of Cement

Early Age Performance of OPC-GGBFS-Concretes Containing Belite-CSA Cement Cured at Sub-Zero Temperatures

The Effect of Polypropylene Fiber Addition on the Compressive Strength and Ultrasonic Pulse Velocity of Low-Temperature Cured AlkaliActivated Slag

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