Na_2SO_4和NaNO_2对混凝土自收缩的影响

Influence of Na_2SO_4 and NaNO_2 on Concrete Autogenous Shrinkage

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。

Using traditional indicator, the present thesis shnnkage zero concrete whose test points W/C is 0. 3 autogenous shrinkage law at test method of dial studies the autogenous of two set of reference and 0. 5 mid the concrete early phase when the two reference concrete are rr,ixed with 1% Na2SO4, 2% Na2SO4,1.5% NAN02 and! 3% NAN02 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 c.oncrete mixed with 1% NaESO4 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. 556 and 3% NaNO2 are both bigger than reference specimen.