水饱和度对再生混凝土力学性能的影响及微观机理分析

Effect of water saturation on mechanical properties of recycled concrete and micro-mechanism analysis

为探究再生混凝土在水工建筑物中应用的可行性,提升资源利用效率,对4种骨料取代率下不同水饱和度的再生混凝土进行力学性能试验研究,并结合核磁共振和电镜扫描试验对再生混凝土进行微观机理分析。结果表明:随着骨料取代率和水饱和度的增加,混凝土弹性模量逐渐增大,而抗压强度、峰值应变和劈裂抗拉强度逐渐减小;对试件横向弛豫时间(T2谱)曲线进行分析发现,骨料取代率为0%、30%、50%和70%试件内的小孔隙数量占比分别为83%、77%、82%、84%;通过扫描电镜观察发现,混凝土基质密实度随再生骨料取代率增加而下降,易被自由水渗透,对再生混凝土的力学性能产生不利影响。本文研究成果可为再生混凝土在水工结构上的应用提供参考。

In order to explore the feasibility of recycled concrete application in hydraulic buildings and improve the efficiency of resource utilization,the mechanical properties of recycled aggregate concrete with different water saturation degrees under four aggregate substitution rates were experimentally investigated.The micro-mechanism of recycled concrete was analyzed by combining nuclear magnetic resonance and electron microscope scanning tests.The results show that the modulus of elasticity of recycled concrete gradually increase with the raise of aggregate substitution rate and water saturation degree.The compressive strength,peak strain and split tensile strength gradually decrease.The analysis of T2 spectrum curve of the specimen find that the number of small pores in the specimen with 0%,30%,50%and 70%aggregate replacement rate accounted for 83%,77%,82%and 84%,respectively.It is found by scanning electron microscope that the density of concrete matrix decrease with the increase of regenerated aggregate substitution rate.The concrete matrix is easily permeated by free water,which will affect the mechanical properties of the recycled concrete.The research results can provide reference for the application of recycled concrete in hydraulic structures.