再生砖骨料混凝土力学性能及破坏机理研究

Study on Mechanical Properties and Failure Mechanism of Recycled BrickAggregate Concrete

以8种设计配合比的再生砖骨料次轻混凝土为研究对象,以水灰比、最大骨料尺寸和粗骨料种类为试验参数,开展了混凝土干密度、立方体抗压强度和劈裂抗拉强度试验研究,重点分析了骨料界面特征与再生砖骨料混凝土的破坏机理。结果表明:使用再生粘土砖骨料制备的次轻混凝土28 d抗压强度可达36 MPa,干密度不大于2200 kg/m^(3),能够减轻自重8%~16%;随着水灰比和取代率的降低,混凝土抗压和劈裂抗拉强度均呈显著增加的趋势;最大骨料尺寸对混凝土抗压和劈裂抗拉强度的影响较小;拟合所得混凝土干密度与力学性能换算公式的相关性较好;砖骨料-砂浆界面过渡区微观结构较为密实,混凝土界面性能得到增强;界面过渡区性能和砖骨料强度是影响再生砖骨料混凝土力学性能的两个关键因素,且砖骨料强度是其中最主要的因素。综合考虑,使用再生粘土砖骨料制备次轻混凝土具有良好的经济性和广阔的工程应用前景。

In this work,8 kinds of recycled brick aggregate lightweight concrete with design mix ratio were taken as the research object,and water-cement ratio,maximum aggregate size and coarse aggregate type were taken as the test parameters.Experiments on dry density,cube compressive strength and split tensile strength of concrete were carried out,and the interface characteristics of aggregate and failure mechanism of recycled brick aggregate concrete were analyzed emphatically.The results show that the 28 d compressive strength of the secondary lightweight concrete prepared with recycled clay brick aggregate can reach 36 MPa,and the dry density is no more than 2200 kg/m^(3),which can reduce the dead weight by 8%—16%.With the decrease of water-cement ratio and replacement ratio,the compressive and splitting tensile strength of concrete increased significantly.The maximum aggregate size had little influence on the compressive and splitting tensile strength of concrete.The correlation between the fitted concrete dry density and the conversion formula of mechanical properties was good.The microstructure of brick aggregate-mortar interfacial transition zone was relatively compact,and the interfacial performance of concrete was enhanced.The performance of interfacial transition zone and the strength of brick aggregate were two key factors affecting the mechanical properties of recycled brick aggregate concrete,and the strength of brick aggregate was the most important one.Taking the recycled clay brick aggregate into consideration,it had a good economic and engineering prospect to prepare the specific density concrete.