粗骨料对砂浆裂缝扩展影响的试验研究

发布时间：2019-02-23 21:55

【摘要】：细观上混凝土是由砂浆、骨料以及它们之间的界面过渡区(ITZ)组成,混凝土的力学性能取决于三相的性质以及它们之间的相互作用,而砂浆、骨料、界面过渡区三者性质复杂,这更加大了从细观上分析原有混凝土裂缝问题的难度。混凝土作为多相复合材料,裂缝的扩展路径取决于材料的抗力和应力状态,而影响裂缝扩展路径的混凝土材料抗力包括混凝土各相介质及交界面的相对强度。因此,为了更好地了解粗骨料对混凝土、砂浆裂缝扩展的影响,本文开展了如下的研究工作：(1)砂浆-岩石界面抗拉强度试验研究采用一半砂浆一半岩石,尺寸为200mm×100mm×100mm的界面复合试件。研究了不同砂浆强度、岩石种类、岩石表面粗糙度的砂浆-岩石界面的直接拉伸、劈裂抗拉强度。结果表明,随着界面粗糙度、砂浆强度的增加,砂浆-岩石界面的抗拉强度大幅提高；(2)砂浆-岩石界面断裂特性试验研究对尺寸为700mm×150mm×40mm的一半砂浆、一半岩石的试件进行了三点弯曲试验,考虑了砂浆强度、岩石种类、岩石表面粗糙度对界面断裂特性的影响。结果发现,岩石表面经过处理后,其承载力、起裂时的应力强度因子、断裂能均有所提高。因此,可以通过增加岩石表面粗糙度的方式提高界面的承载力；岩石种类对界面性质影响很大,对于其他组成相同的花岗岩试件的承载力、断裂能均小于砂岩试件。(3)砂浆预埋粗骨料试件三点弯曲试验研究对尺寸为700mm×150mm×40mm的砂浆预埋粗骨料试件进行了三点弯曲试验,通过改变砂浆强度、骨料种类、骨料表面粗糙度,实现了裂缝尖端遇到骨料后裂缝扩展的不同路径：裂缝穿过骨料扩展；裂缝沿着界面绕骨料扩展。试验结果表明,硅灰的加入改善了界面过渡区的性质,提高了砂浆强度,对裂缝扩展路径有很大影响。所有高强砂浆试件,裂缝均穿过骨料扩展；所有试件的起裂应力强度因子均小于同等强度的砂浆的起裂韧度,可见在砂浆中加入粗骨料使得砂浆的抗裂性变差；相比于裂缝穿过骨料扩展,裂缝沿界面绕着骨料扩展时,拉应力将骨料从水泥砂浆中拔出,由于骨料与水泥砂浆的粘结,使得裂缝可以继续传力,从而改善了砂浆的断裂脆性。
[Abstract]:The concrete is composed of mortar, aggregate and interfacial transition zone (ITZ). The mechanical properties of concrete depend on the properties of three phases and the interaction between them. The three properties of the interfacial transition zone are complex, which makes it more difficult to analyze the crack problem of the original concrete from a meso view. As a multiphase composite material, the crack propagation path depends on the resistance and stress state of the material, and the resistance of concrete material which affects the crack propagation path includes the relative strength of each phase medium and interface of concrete. Therefore, in order to better understand the effect of coarse aggregate on the crack propagation of concrete and mortar, the following research work has been carried out in this paper: (1) the tensile strength of the interface between mortar and rock is tested with half mortar and half rock. The interfacial composite specimen with the size of 200mm 脳 100mm 脳 100mm. The direct tensile and splitting tensile strength of the interface between mortar and rock with different mortar strength, rock type and rock surface roughness are studied. The results show that the tensile strength of the interface between mortar and rock increases greatly with the increase of interface roughness and mortar strength. (2) the experimental study on the fracture characteristics of the interface between mortar and rock; the three-point bending test of half mortar and half rock with the size of 700mm 脳 150mm 脳 40mm is carried out, and the effects of mortar strength, rock type and rock surface roughness on the interfacial fracture characteristics are considered. The results show that the bearing capacity, stress intensity factor and fracture energy of rock surface are improved after treatment. Therefore, the bearing capacity of the interface can be improved by increasing the roughness of the rock surface. The type of rock has a great influence on the interfacial properties, and the bearing capacity of other granite specimens with the same composition, The fracture energy is lower than that of sandstone specimen. (3) the three-point bending test of mortar pre-buried coarse aggregate specimen with size 700mm 脳 150mm 脳 40mm has been carried out by changing the strength of mortar and the type of aggregate. The roughness of aggregate surface realizes different paths of crack propagation after crack tip meets aggregate: crack propagates through aggregate; The cracks spread around the aggregate along the interface. The experimental results show that the addition of silica fume improves the properties of the interfacial transition zone, increases the mortar strength, and has a great influence on the crack propagation path. The crack spread through the aggregate in all the high strength mortar specimens, and the crack initiation stress intensity factor of all the specimens was lower than that of the mortar of the same strength, so the crack resistance of the mortar became worse by adding coarse aggregate to the mortar, and the crack initiation stress intensity factor of all the specimens was lower than that of the same strength mortar. Compared with the crack propagating through the aggregate, the tensile stress pulls the aggregate out of the cement mortar when the crack spreads around the aggregate along the interface. Because of the bond between the aggregate and the cement mortar, the crack can continue to transmit force, thus improving the fracture brittleness of the mortar.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU578.1

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