锂渣-CaO胶凝体系的火山灰反应性研究

Pozzolanic Reactivity of Lithium Slag-CaO Cementitious System

锂渣的火山灰反应性是其在水泥基材料中发挥活性的重要因素之一。本文采用锂渣-Ca(OH)2-H 2O胶凝体系来简化锂渣与水泥的化学反应过程,研究不同CaO含量的胶凝体系中锂渣反应程度、硬化浆体强度、水化产物组成及微观结构等火山灰反应性能,并建立锂渣反应程度与体系强度之间的关系。结果表明,在锂渣-Ca(OH)2-H 2O胶凝体系中,锂渣反应率随CaO含量及龄期的增长而增大,90 d反应率在21.46%~25.68%。体系发生火山灰反应主要生成了C-(A)-S-H凝胶、钙矾石(AFt)、单硫型水化硫铝酸钙(AFm)和沸石相等产物,各产物间早期联系较弱,体系结构松散,后期形成了致密的板状结构。其中CaO/锂渣值为0.25时,试样具有相对较高的强度,且能够相对充分地激发锂渣活性,促进C-(A)-S-H凝胶生成;CaO掺量过高会抑制锂渣初期水化反应,且未反应的CaO则以游离态(f-CaO)形式存在,对强度产生不良影响;未掺加CaO的锂渣自身没有水硬性。锂渣反应程度与胶凝体系强度呈现良好的e指数关系,在锂渣反应率大于11%时,浆体强度开始显著增大。

The pozzolanic reactivity of lithium slag(LS)is one of the important factors for its activity in cement-based materials.In this paper,the LS-Ca(OH)2-H 2O cementitious system was used to simplify the chemical reaction process of LS and cement.The pozzolanic reactivity such as,reaction degree of LS,strength of hardened paste,composition and microstructure of hydration products of cementitious systems with different CaO content were studied,and the relationship between LS reaction degree and hardened paste strength was established.The results show that in the LS-Ca(OH)2-H 2O cementitious system,the LS reaction rate increases with the increase of CaO content and age,which is between 21.46%and 25.68%at 90 d.The pozzolanic reaction in this system mainly produces C-(A)-S-H gel,ettringite(AFt),monosulfate(AFm)and epistilbite.The weak connection between the early products result in a loose structure and the later products form a dense plate-like structure.When the CaO/LS value of about 0.25,the sample has relatively high strength,and more fully excite the activity of LS,which promotes the formation of C-(A)-S-H gel.When the CaO content is too high,the initial hydration reaction of LS is inhibited,and unreacted CaO exists in the free state(f-CaO)will adversely affect the strength.The LS without CaO do not have hydraulic properties.The strength of hardened pastes and the LS reaction degree have a good e-index relationship.When the LS reaction rate is greater than 11%,the strength of the pastes begin to increase significantly.