间歇浇筑板式混凝土的早期约束收缩效应分析

以桥梁高性能混凝土为研究对象,测试老混凝土约束下新混凝土板的收缩变形。通过试验分析界面粗糙度对其影响,并考察混凝土内部早期温、湿度变化与收缩应变的关系,分析养护时间对混凝土材料收缩应力的影响。结果表明:老混凝土约束下的新混凝土厚度随新老混凝土黏结界面粗糙度的提高而增大,新混凝土内部拉应力随界面粗糙度的提高而降低,但新、老混凝土界面粗糙度对黏结面处的收缩影响不显著;距黏结面越近的截面收缩应变越小,在黏结面处达到最小,表现出显著的不均匀性,并随龄期逐渐增大。延长养护时间可减小混凝土收缩变形和内部由于不均匀收缩导致的拉应力,降低混凝土板早期开裂的风险。

ANALYSIS OF RESTRAINED SHRINKAGE OF INTERMITTENT CASTING CONCRETE SLAB IN THE EARLY AGE

Aiming at the high performance concrete in bridge engineering,bonding restrained shrinkage experiment of old and new concrete slabs with the different interface roughness and curing duration were conducted to investigate the early time-varying characteristics of the temperature and humidity of concrete and analyze the impact of curing duration on shrinkage stress of new concrete and bonding surface. The experimental results show that the thickness of new concrete impacted by the restraint of old concrete increases and the inner tensile stress of new concrete decreases with increasing of the roughness of bonding surface,however it is not so prominent for the effect of roughness on the shrinkage at bonding surface; the shrinkage strain of section reduces with reduction of the distance of section to bonding surface and reaches minimum at bonding surface,which reflects prominent inhomogeneity and increases gradually with concrete age; extending the curing duration can reduce shrinkage deformation and tensile stress induced by internal inhomogeneous shrinkage of concrete,thus reducing the risk of early crack of concrete slab.