砂浆-花岗岩界面过渡区的劈裂拉伸试验研究

Experimental Study on Split Tension of Mortar-aggregate Interface Transition Zone

从细观层次看,骨料周围水泥砂浆即所谓的界面过渡区(Interfacial Transition Zone,简称ITZ)的形貌、成分、密度等特征与水泥砂浆基体显著不同。由于ITZ往往被看成混凝土中的"薄弱环节",其性能在很大程度上影响着混凝土的宏观力学性能。本文采用巴西圆盘劈裂法,设计一定宽度的弧形垫条,以形成2α=20°的平台对含界面的砂浆-花岗岩试样进行准静态劈裂拉伸试验。考虑试样的不同直径、不同砂浆强度、不同长径比、不同应变率及花岗岩骨料表面不同粗糙度等多种因素对界面拉伸强度的影响。采用正交分析法对试验数据进行系统分析。同时,在劈裂拉伸试验中,结合散斑图像采集系统对劈裂试验过程中试样表面的图像进行实时采集,从而获得试样在加载过程中的破坏形式与形态。

From the mesoscopic level, cement mortar around the aggregate, a so-called Interfacial Transition Zone（Interfacial Transition Zone, ITZ）, its morphology, composition and density and other characteristics are significantly different from the cement mortar matrix＇s. Since the ITZ is usually considered to be the ＂weak link＂ in concrete, its performance affects the macroscopic mechanical properties of concrete to a large extent. In this paper, the Brazilian disc splitting method is used, and a certain width of arc pad article was designed to form a 2α=20° platform for the quasi static splitting tensile test of containing interface mortar-granite samples. In the test, the diameter of samples, mortar strength, length-diameter ratio, strain rate and surface roughness of granite aggregate and other factors＇ effects on the interface tension strength were all researched. Orthogonal analysis method was applied to systematically analyze the experimental data.Meanwhile, in the splitting tensile test, a speckle image acquisition system was used, realized real-time acquisition for surface images of the sample in order to obtain the destruction pattern and form of samples in the loading process.