岩基约束橡胶集料混凝土开裂应变试验

Experiment on crack strain of rubber aggregate concrete restrained by bedrock

解决岩基混凝土开裂有利于提高水工建筑物的耐久性和安全运行。采用约束圆环试验、电阻应变仪、电子扫描电镜和压汞试验,分析了橡胶集料砂浆约束开裂应变及其作用机理。在岩基混凝土内埋设应变计,观测橡胶集料混凝土的约束应变。结果表明:橡胶集料在应力作用下,改变了水泥石中孔的形态,缓冲部分应力,普通砂浆开裂时,橡胶集料开始表现硬化应变。在45d和90d龄期时,岩基普通混凝土应变急剧降低,混凝土出现开裂。岩基橡胶集料混凝土约束应变大,混凝土无开裂。橡胶集料有利于改善岩基混凝土的抗裂性能,为解决岩基混凝土裂缝提供一种新的技术措施。

Prevention of bedrock concrete cracking can improve the durability and operation safety of hydraulic structures. In this work, the cracking mechanism and restrained strain of rubber aggregate motar were studied through an experiment of restrained loop with resistance strain gauges, scanning electron microscrope and mercury porosimeter. The strain gauges were buried into bedrock concrete for measurement of restrained strain of rubber aggregate concrete. The results reveal that the rubber aggregate material under stressing causes a change in the shape of pores in the cement paste matrix and part of its stress is released. In the condition of ordinary motar cracking, this material develops curing strain and larger restrained strain, so the concrete does not crack. At the ages of 45d and 90d, the restrained strain in ordinary bedrock concrete is reduced quickly and its cracks start developing. Thus, rubber aggregate can improve the performances of bedrock concrete against cracking. This study provides an effective technical measure for prevention of bedrock concrete cracking.