Early activation of high volume fly ash by ternary activator and its activation mechanism
Early activation of high volume fly ash by ternary activator and its activation mechanism
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三元活化剂对高掺量粉煤灰的早期活化及其活化机理
DOI：
10.1016/j.jenvman.2020.110638
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发表时间：
2020
影响因子：
8.7
通讯作者：
Liu Zhiyong
中科院分区：
文献类型：
--
作者：
Sun Guowen;Tang Qingqing;Zhang Jianjian;Liu Zhiyong
为了解决粉煤灰在水泥基材料中的大掺量使用所带来的早期强度低、塑性开裂严重等问题。选择三乙醇胺（TEA）、氢氧化钙（Ca（OH）2）和硅酸钠（Na 2SiO 3）或硫酸钠（Na 2SO 4）进行三元掺杂试验。通过测定试件的抗压强度，确定激发剂的最佳配比、掺量和时效性，并通过各种微观试验研究激发剂的作用机理。建立了粉煤灰-水泥体系主要水化产物的定量计算模型。基于分子动力学模拟，研究了碱活化条件下NASH凝胶的结构。结果表明：TEA：Ca（OH）2：Na 2SiO 3的最佳配比为2：75：25，最佳掺量为胶凝材料的1.02%。水化14 d后，体系中存在大量针状钙矾石、花瓣状水化铝酸钙和团簇状水化硅酸钙凝胶，而板状CH含量明显减少。NASH凝胶中Si/Al为3，Al以四面体配位为主，键稳定性和原子迁移率的顺序分别为Si-O > Al-O > Na-O和Na > O > Al>。在Na+和碱环境下，Si（OH）4和Al（OH）4-发生缩聚反应，形成改革聚合物Si-O-Si和Al-O-Si，形成大量NASH凝胶。
To solve the problems of low early strength and severe plastic cracking caused by high volume fly ash used in cement-based materials. Triethanolamine (TEA), calcium hydroxide (Ca(OH)2), and sodium silicate (Na2SiO3) or sodium sulfate (Na2SO4) were selected to conduct a ternary doping test. The compressive strength of samples was measured to determine the best ratio, content, and time effect of the activator, and its action mechanism was studied by various micro test. The quantitative calculation model of main hydration products was established in the fly ash-cement system. Based on the simulation of molecular dynamics, the structure of NASH gel was studied under alkali activation. The results show that the optimal mixing mass ratio of TEA:Ca(OH)2:Na2SiO3is 2:75:25 and the optimal dosage is 1.02% of the cementitious material. There are a large number of needle-like ettringite, petaloid hydrated calcium aluminate and clusters of hydrated calcium silicate gel in the system, whereas the amount of plate-like CH decreased significantly at hydration for 14 days. The Si/Al is three and aluminium coordination is predominantly tetrahedral, and the order of bonds stability and atoms mobility are Si–O > Al–O > Na–O and Na > O > Al> in the NASH gel, respectively. Under the Na+and alkali environment, the Si(OH)4and Al(OH)4-formed polycondensation reaction to reform polymers Si–O–Si and Al–O–Si, forming a large amount of NASH gel.