骨料-砂浆界面过渡区力学特性试验

Experiment of mechanics properties of interfacial transition zone between of aggregate and mortar

骨料-砂浆形成的界面过渡区对混凝土力学性能有显著影响,界面过渡区力学参数是开展混凝土细观数值模拟的基本力学参数。以大理石板的光滑面和粗糙面分别代表卵石和人工碎石骨料表面,应用岩体节理粗糙度系数测试原理和方法对其表面的粗糙度进行表征。分别对3种强度等级混凝土、2种最大骨料粒径的6种混凝土骨料-砂浆界面过渡区开展劈裂抗拉、变角剪切和三点弯曲断裂试验。试验结果表明,界面过渡区的劈裂抗拉强度、抗剪强度、断裂韧度较原配合比的混凝土低,约为原混凝土强度的50%。随着混凝土强度等级提高,界面抗拉强度、黏聚强度和断裂韧度增大,摩擦角有减小的趋势。增大骨料表面粗糙度、减小最大骨料粒径可以提高界面抗拉强度和断裂韧度。在相同强度等级和界面粗糙度情况,界面黏聚强度则随骨料粒径增大而增大,其规律与抗拉强度和断裂韧度相反。

The interfacial transition zone(ITZ)between of aggregate and mortar has an effect signally on mechanics properties of concrete.Mechanics parameters of ITZ are basically data for meso-level simulation of concrete materials failure.The smooth and rough surface of marble plate is regarded as surface of pebbles and gravel aggregate respectively.The surface roughness are characterized by the principle and method of rock joint roughness coefficient.Six group of concrete samples with ITZ surface are tested to obtain tensile strength,shear strength and fracture toughness.The experimental concrete includes three kinds of strength grade and two kinds of maximum aggregate particle size.The experimental results show that the tensile strength,shear strength and fracture toughness of the ITZ are lower than that of the original concrete,about 50%.With the increase of concrete strength,the tensile strength,cohesion strength and fracture toughness of the ITZ increases,and the friction angle decreases.Increasing the surface roughness of the aggregate and reducing the maximum aggregate size can improve the tensile strength and fracture toughness of the ITZ.At the same concrete strength and ITZ surface roughness,the cohesion strength of the ITZ increases with the increase of aggregate particle size,and its law is opposite to tensile strength and fracture toughness of the ITZ.