自密实轻骨料混凝土约束收缩试验及抗裂性能研究

Experimental Study on Restrained Shrinkage and Crack Resistance of Self-compacting Lightweight Aggregate Concrete

试验采用高强页岩陶粒及Ⅰ级粉煤灰制备工作性能良好的自密实轻骨料混凝土(SCLC),通过环形约束收缩试验,进行密封与外侧面干燥两种条件下的约束收缩试验,研究自密实轻骨料混凝土约束收缩应变随着龄期发展规律及抗裂性能。研究结果表明:自密实轻骨料混凝土在3d前的自生收缩与干燥收缩大于普通混凝土,14d后的自生收缩与干燥收缩低于普通混凝土;掺加Ⅰ级粉煤灰可以明显提高新拌SCLC浆体的工作性能,也能有效抑制SCLC的自生收缩,但其掺量应该控制在25%以内较合适;以开裂风险系数η作为混凝土的抗裂性能评价指标,自密实轻骨料混凝土的抗裂能力要高于普通混凝土,但SCLC在达到临界开裂状态后很快产生贯穿性裂缝,其开裂的时间反而比普通混凝土早。

The self-compacting lightweight aggregate concrete(SCLC) with good workability was prepared using grade I fly ash and high-strength shale ceramsite,the shrinkage tests of the SCLC under sealing and drying conditions were carried out by ring restrained shrinkage test. The development of shrinkage strain of SCLC with age and the crack resistance were studied. The results show that the autogenous shrinkage and drying shrinkage of SCLC before 3 d are greater than that of ordinary concrete,and after 14 d the autogenous shrinkage and drying shrinkage are lower than that of ordinary concrete. The grade I fly ash can obviously improve the working performance of fresh SCLC paste and effectively restrain the autogenous shrinkage of SCLC,but the content should be controlled within 25%. With evaluation index η of cracking risk,the cracking resistance of self-compacting lightweight aggregate concrete is higher than that of ordinary concrete,but SCLC develop transverse cracks soon after reaching critical cracking,and the cracking time is earlier than that of ordinary concrete.