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Effects of calcium formate on early-age strength and microstructure of high-volume fly ash cement systems
Magazine of Concrete Research ( IF 1.8 ) Pub Date : 2021-01-06 , DOI: 10.1680/jmacr.20.00118
Zhiyuan Zhou 1 , Massoud Sofi 1 , Aocheng Zhong 1 , Amin Shahpasandi 1 , Marvel Cham Sarabia 1 , Priyan Mendis 1
Affiliation  

Replacement of Portland cement (PC) by fly ash (FA) is currently limited to 15–30% by mass, mainly due to low early age strength development of concrete. This research uses calcium formate (Ca(HCO2)2; CF) as an admixture to high-volume FA (HVFA) composites to improve its strength properties. HVFA represents 60–70% of cement replaced by FA and dosage of CF varies from 0.5% up to high dosage of 9% of cement content. Compressive strength, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy were conducted to investigate the effects of CF on hydration and microstructural aspects. The results show that both HVFA pastes with 60% and 70% FA achieved the highest strength at the CF dosage of 3%. At the age of 28 days, adding 3% CF to HVFA mixes led to higher consumption of FA as well as higher formation of calcium hydroxide (Ca(OH)2), calcium silicate hydrates, calcium carbonate (CaCO3) and ettringite, which contribute to the increase of strength. The addition of very high dosages of CF at 9% increased the hydration of tricalcium aluminate but could hinder the hydration of tricalcium silicate in both PC and HVFA pastes with 60% and 70% FA.

中文翻译:

甲酸钙对高掺量粉煤灰水泥体系早期强度和微观结构的影响

用粉煤灰 (FA) 替代波特兰水泥 (PC) 目前仅限于 15-30% 的质量,主要是由于混凝土的早期强度发展较低。本研究使用甲酸钙 (Ca(HCO 2 ) 2; CF) 作为高容量 FA (HVFA) 复合材料的混合物,以提高其强度性能。HVFA 代表 60-70% 的水泥被 FA 取代,CF 的用量从 0.5% 到水泥含量的 9% 的高用量不等。进行了抗压强度、等温量热法、热重分析、X 射线衍射和扫描电子显微镜检查,以研究 CF 对水合和微观结构方面的影响。结果表明,含 60% 和 70% FA 的 HVFA 糊剂在 3% 的 CF 剂量下都达到了最高强度。在 28 天龄时,向 HVFA 混合物中添加 3% CF 导致更高的 FA 消耗以及更多的氢氧化钙 (Ca(OH) 2 )、硅酸钙水合物、碳酸钙 (CaCO 3) 和钙矾石,有助于提高强度。添加 9% 的非常高剂量的 CF 会增加铝酸三钙的水合,但会阻碍 60% 和 70% FA 的 PC 和 HVFA 糊中硅酸三钙的水合。
更新日期:2021-01-06
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