Na2SO4和NaNO2对混凝土自收缩的影响

采用传统千分表测试方法,研究了W/C为0.3和0.5的两组基准混凝土的自收缩零点测试点,以及这两种W/C下分别单掺1％ Na2SO4、2％ Na2SO4、1.5％ NaNO2和3％NaNO2的混凝土早期自收缩的规律.结果表明,W/C为0.3的基准混凝土自收缩开始测试点为搅拌加水后13 h,掺入2％ Na2SO4混凝土自收缩与基准试件较为相近,掺入1％Na2SO4的混凝土自收缩较基准件显著增大.NaNO2的掺入使得混凝土早期自收缩减小,同时,掺入1.5％ NaNO2混凝土的早期自收缩比掺量为3％NaNO2的略大.W/C=0.5的基准混凝土自收缩开始测试时间为搅拌加水后21 h,掺入1.5％和3％ NaNO2的混凝土自收缩均比基准试件大.

Influence of Na2SO4 and NaNO2 on Concrete Autogenous Shrinkage

Using traditional test method of dial indicator,the present thesis studies the autogenous shrinkage zero test points of two set of reference concrete whose W/C is 0.3 and 0.5 and the concrete autogenous shrinkage law at early phase when the two reference concrete are mixed with 1%Na2SO4、2%Na2SO4、1.5%NaNO2 and 3%NaNO2 respectively.The result shows that autogenous shrinkage starting test point of the reference concrete whose W/C is 0.3 is 13 h after being added with water and stirred;the autogenous shrinkage of concrete mixed with 2%Na2SO4 is more similar with reference test specimen;the autogenous shrinkage of concrete mixed with 1%Na2SO4 rises notably compared with reference specimen.Adding of NaNO2 makes concrete autogenous shrinkage at early phase decrease.At the same time,concrete autogenous shrinkage mixed with 1.5%NaNO2 at early phase is a little bigger than that of concrete added with 3%NaNO2.Autogenous shrinkage starting test point of the reference concrete whose W/C is 0.5 is 21 h after being added water and stirred.Autogenous shrinkage of concrete mixed with 1.5% and 3%NaNO2 are both bigger than reference specimen.