自密实混凝土自生约束收缩开裂性能试验研究

Experimental Study on Cracking Tendency under Restrained Autogenous Shrinkage of Self-compacting Concrete

通过钢环内壁贴应变片的环形约束收缩试验，研究了自密实混凝土由自生收缩引起的受力和开裂性能．以不同掺量的粉煤灰、矿渣单掺和复掺为主要因素，研究了自生约束收缩下自密实混凝土试件的钢环应变随龄期的发展规律，分析了钢环应变、混凝土有效自生收缩应变、混凝土收缩应力、开裂风险系数的相互关系．结果表明：单单自生收缩足以导致自密实混凝土环开裂，粉煤灰等量替代水泥能有效降低由自生约束收缩引起的混凝土应力，但掺量过高时混凝土的抗拉强度会明显下降；矿渣等量替代水泥或粉煤灰使混凝土的自生收缩应力增大，抗拉强度略有增加；混凝土环开裂时试件开裂风险系数为1．00～1．25，掺和料对开裂风险系数有影响．

Autogenous shrinkage of self-compacting concrete（SCC） was studied by restrained ring test. Taking fly ash and granulated blast-furnace slag（GBS） content as main parameters, development of steel ring strains as function of concrete age was investigated; correlations between steel ring strains, effective autogenous shrinkage, tensile stress and cracking risk coefficient（CRC） of SCC specimens were studied. The results show that the autogenous shrinkage alone can cause cracking of concrete specimens. Fly ash is helpful to decrease the tensile stress induced by autogenous shrinkage, but high content of fly ash may cause reduction of tensile strength. The stress and the tensile strength of the concrete are increased by the addition of GBS. Ring specimens cracking risk coefficient is in the range of 1.00-1.25 and cracking risk coefficient changes with concrete ages and mineral admixtures.