發(fā)布時間：2019-02-23 21:55

【摘要】：細觀上混凝土是由砂漿、骨料以及它們之間的界面過渡區(qū)(ITZ)組成,混凝土的力學(xué)性能取決于三相的性質(zhì)以及它們之間的相互作用,而砂漿、骨料、界面過渡區(qū)三者性質(zhì)復(fù)雜,這更加大了從細觀上分析原有混凝土裂縫問題的難度�；炷磷鳛槎嘞鄰�(fù)合材料,裂縫的擴展路徑取決于材料的抗力和應(yīng)力狀態(tài),而影響裂縫擴展路徑的混凝土材料抗力包括混凝土各相介質(zhì)及交界面的相對強度。因此,為了更好地了解粗骨料對混凝土、砂漿裂縫擴展的影響,本文開展了如下的研究工作：(1)砂漿-巖石界面抗拉強度試驗研究采用一半砂漿一半巖石,尺寸為200mm×100mm×100mm的界面復(fù)合試件。研究了不同砂漿強度、巖石種類、巖石表面粗糙度的砂漿-巖石界面的直接拉伸、劈裂抗拉強度。結(jié)果表明,隨著界面粗糙度、砂漿強度的增加,砂漿-巖石界面的抗拉強度大幅提高；(2)砂漿-巖石界面斷裂特性試驗研究對尺寸為700mm×150mm×40mm的一半砂漿、一半巖石的試件進行了三點彎曲試驗,考慮了砂漿強度、巖石種類、巖石表面粗糙度對界面斷裂特性的影響。結(jié)果發(fā)現(xiàn),巖石表面經(jīng)過處理后,其承載力、起裂時的應(yīng)力強度因子、斷裂能均有所提高。因此,可以通過增加巖石表面粗糙度的方式提高界面的承載力；巖石種類對界面性質(zhì)影響很大,對于其他組成相同的花崗巖試件的承載力、斷裂能均小于砂巖試件。(3)砂漿預(yù)埋粗骨料試件三點彎曲試驗研究對尺寸為700mm×150mm×40mm的砂漿預(yù)埋粗骨料試件進行了三點彎曲試驗,通過改變砂漿強度、骨料種類、骨料表面粗糙度,實現(xiàn)了裂縫尖端遇到骨料后裂縫擴展的不同路徑：裂縫穿過骨料擴展；裂縫沿著界面繞骨料擴展。試驗結(jié)果表明,硅灰的加入改善了界面過渡區(qū)的性質(zhì),提高了砂漿強度,對裂縫擴展路徑有很大影響。所有高強砂漿試件,裂縫均穿過骨料擴展；所有試件的起裂應(yīng)力強度因子均小于同等強度的砂漿的起裂韌度,可見在砂漿中加入粗骨料使得砂漿的抗裂性變差；相比于裂縫穿過骨料擴展,裂縫沿界面繞著骨料擴展時,拉應(yīng)力將骨料從水泥砂漿中拔出,由于骨料與水泥砂漿的粘結(jié),使得裂縫可以繼續(xù)傳力,從而改善了砂漿的斷裂脆性。
[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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TU578.1

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