外加剂对混凝土收缩与开裂性能影响的试验研究

摘要

针对传统混凝土中加入矿物外加剂会导致混凝土开裂的问题,提出在传统方法上加入粉煤灰和硅灰.为验证方法的可行性,采用不同实验配方比,并结合单掺和复掺方式,对上述方法进行验证.实验表明:复掺30％～ 40％的粉煤灰和矿粉可有效降低混凝土的开裂面积;硅灰与粉煤灰和矿粉在二元或三元复合下可降低砂浆自收缩和干燥收缩,且混凝土强度不会降低.由此得出昆凝土收缩与开裂和砂浆收缩存在显著相关性,砂浆的自收缩和干燥收缩是影响开裂的主要因素.%Aiming at the problem of concrete cracking caused by addition of mineral admixture in traditional concrete,the method of adding fly ash and silica fume in the concrete was put forward.By using different experimental formula,combined with single and compound admixtures,the feasibility of above-mentioned method was verified.Experimental results show that the complex with 30％ ～ 40％ fly ash and slag can effectively reduce the cracking area of concrete;adding silica fume and fly ash and slag can reduce the self shrinkage and drying shrinkage in two-element or three-element compound,and the concrete strength is not reduced.So it is concluded that there is a significant correlation between concrete shrinkage and cracking with mortar shrinkage.The self shrinkage and drying shrinkage of mortar are the main factors to affect the cracking of concrete.