自密实混凝土自生约束收缩下应力松弛性能研究

以水胶比、胶凝材料用量为主要参数,研究较长龄期内自密实混凝土的自由自生收缩性能及圆环约束收缩下钢环应变的发展规律,通过分析得到自密实混凝土在自生约束收缩下的应力松弛性能。结果表明:自密实混凝土自生变形在经过1d左右的小幅膨胀后开始收缩,3～7d内收缩增长较快,接下来在长达100d的测试过程中缓慢而持续地增长;自生收缩在受约束时应力增长也有类似的规律。自生约束收缩引起的应力松弛主要发生在3～7d的早龄期,之后应力松弛的增长几乎停滞;自密实混凝土的应力松弛率随水胶比的提高显著增大,随胶结料用量的增加有增大的趋势。

Study on the Stress Relaxation Properties Induced in Restrained Autogenous Shrinkage of Self-compacting Concrete

Internal stress development and stress relaxation induced by restrained autogenous shrinkage of self-compacting concrete (SCC) were investigated under different water/binder ratios and different amounts of cementitious material. Test results show that the free autogenous deformation expanded within 1 d and then shrank rapidly from 3 d to 7 d; afterward, the autogenous shrinkage grew slowly and steadily. The development of stress during restrained autogenous shrinkage also had a similar trend. The stress relaxation mainly developed at early ages within 7 d, and then its growth was almost stagnant. The stress relaxation rate of SCC increased significantly with the increase of water/binder ratio; it also increased with increasing cementitious contents.