RESEARCH ON VISUALIZATION OF FRACTURE PROCESS OF SUPER-HIGH-STRENGTH CONCRETE

粗集料的抗压强度、弹性模量和韧性等力学性能对配制超高强度混凝土具有重要意义。为了研究粗集料对超高强混凝土抗压强度的影响，采用几种人工粗集料按一定方式排列的板试件进行了抗压试验。试验时，拍摄了裂纹在压缩条件下的萌生和扩展过程，并通过纸质应变片测量了应变的浓度和分布。试验结果总结如下：1。当粗集料的弹性模量高于砂浆，且粗集料与砂浆的粘结强度很小时，在加载初期就会出现粘结裂缝。如果结合强度存在一定程度，则在最大应力的一半水平上发生结合裂纹。2 .当粗集料抗压强度高于砂浆抗压强度时，如果粗集料含量较低，则不能指望粗集料起到止裂作用。为了制作抗压强度大于120mpa的超高强混凝土，应注意以下几点：(1)粗骨料和砂浆抗压强度均大于120mpa。(2)粗集料与砂浆的弹性模量差异较小。(3)粗集料坚韧。(4)存在较大的粗集料。

Mechanical properties of coarse aggregate such as compressive strength, modulus of elasticity and toughness are important for making super-high-strength concrete. In order to investigate the effect of coarse aggregate on compressive strength of super-high-strength concrete, plate specimens, in which a few types of artificial coarse aggregates were arranged in some ways, were tested in compression. When tested, the pictures of initiation and propagation of cracks under compression were taken, and the concentration and distribution of strain were measured by paper strain gauges. The test results are summarized as follows :1.In the case that modulus of elasticity of coarse aggregates are higher than that of mortar and bond strength between coarse aggregates and mortar is very small, bond cracks occur at the early stage of loading. If the bond strength exsists in some extent, bond cracks occur at the half level of maximum stress.2.In the case that compressive strength of coarse aggregates are higher than that of mortar, crack arresting by coarse aggregates cannot be expected if the content of coarse aggregates is small.3.In order to make super-high-strength concrete with compressive strength of more than 120 MPa, the attention should be payd to the followings.(1) Both coarse aggregate and mortar have compressive strength more than 120 MPa.(2) Difference of modulus of elasticity between coarse aggregate and mortar is small.(3) Coarse aggregate is tough.(4) Relatively large amount of coarse aggregate exsist.