Calcium nitrate as a modifier agent for metakaolin-based geopolymer mortar

IF 7.4 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Construction and Building Materials Pub Date : 2024-11-22 DOI:10.1016/j.conbuildmat.2024.139199

Alaa M. Rashad , Ghada M.F. Essa , W.M. Morsi , E.A. Fahmy

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引用次数: 0

Abstract

Calcium nitrate, that is a calcium source, is generally used as an accelerating agent, antifreezing admixture, and corrosion inhibitor for Portland cement systems. Metakaolin, which is regularly used as a precursor in the production of geopolymers, lacks calcium. This can cause inefficiency of the geopolymerization process and alter the properties of the cementitious product. To overcome this problem, the potential benefits of adding calcium nitrate as an alternative calcium source for the metakaolin geopolymer mortar were investigated. Different ratios of calcium nitrate, ranging from 0.5 % to 10 %, were added into metakaolin geopolymer mortar. Different tests were conducted to know the effect of calcium nitrate on some properties of metakaolin geopolymer specimens, which were cured in either air or water. Advanced analysis methods were leveraged to unlock deeper meaning from the findings. The results indicated that adding calcium nitrate led to increased flowability and shortened setting time. The addition of 0.5–7 % calcium nitrate increased mechanical strength but reduced transport properties, whilst the addition of 10 % calcium nitrate led to adverse effects. The addition of 0.5–7 % calcium nitrate can mitigate the strength deterioration rate resulting from water curing and decrease drying shrinkage. The incorporation of appropriate ratios of calcium nitrate can form calcium silicate hydrate gel and densify the microstructure.

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硝酸钙对偏高岭土聚合物砂浆的改性研究

硝酸钙是一种钙源，通常用作硅酸盐水泥体系的速凝剂、防冻外加剂和缓蚀剂。偏高岭土通常被用作生产地聚合物的前体，它缺乏钙。这可能导致地聚合过程效率低下，并改变胶凝产品的性能。为了克服这一问题，研究了在偏高岭土地聚合物砂浆中添加硝酸钙作为替代钙源的潜在效益。在偏高岭土地聚合物砂浆中加入不同比例的硝酸钙0.5 % ~ 10 %。通过不同的试验，了解了硝酸钙对偏高岭土地聚合物样品在空气和水中固化后某些性能的影响。利用先进的分析方法，从研究结果中揭示更深层次的含义。结果表明，硝酸钙的加入提高了浆料的流动性，缩短了凝固时间。添加0.5 ~ 7 %的硝酸钙提高了机械强度，但降低了运输性能，而添加10 %的硝酸钙会产生不良反应。添加0.5 ~ 7 %的硝酸钙可以减缓水固化引起的强度劣化率，降低干燥收缩率。适当比例的硝酸钙掺入可形成水合硅酸钙凝胶，使其微观结构致密。

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来源期刊

Construction and Building Materials 工程技术-材料科学：综合

CiteScore

13.80

自引率

21.60%

发文量

3632

审稿时长

82 days

期刊介绍： Construction and Building Materials offers an international platform for sharing innovative and original research and development in the realm of construction and building materials, along with their practical applications in new projects and repair practices. The journal publishes a diverse array of pioneering research and application papers, detailing laboratory investigations and, to a limited extent, numerical analyses or reports on full-scale projects. Multi-part papers are discouraged. Additionally, Construction and Building Materials features comprehensive case studies and insightful review articles that contribute to new insights in the field. Our focus is on papers related to construction materials, excluding those on structural engineering, geotechnics, and unbound highway layers. Covered materials and technologies encompass cement, concrete reinforcement, bricks and mortars, additives, corrosion technology, ceramics, timber, steel, polymers, glass fibers, recycled materials, bamboo, rammed earth, non-conventional building materials, bituminous materials, and applications in railway materials.