受冻融损伤混凝土与新混凝土的粘结剪切性能试验研究

采用新老混凝土粘结Z形柱体试件,通过快速冻融试验方法,对经受冻融损伤的老混凝土与新混凝土之间的粘结剪切强度进行了试验研究,分析了冻融循环次数、粘结面粗糙度和界面剂种类等对粘结面剪切强度的影响。老混凝土经受冻融循环的次数n为0、25、50、75、100和125,界面的粗糙度为0.23～6.9mm,界面剂采用水泥浆、水泥砂浆和掺加10%UEA膨胀剂的水泥浆。结果表明,受冻融损伤的老混凝土与新混凝土之间的粘结剪切强度随冻融循环次数的增加而下降,表现为冻融初期的缓降和一定冻融循环次数后的陡降,本次试验的陡降点发生在n=75,与抗冻标准中相对动弹性模量下降的临界点基本一致;粘结面的粗糙度和界面剂对粘结剪切强度也有不同程度的影响,粘结面的剪切强度以凿毛面与水泥砂浆组合情况为好。

Experimental research on bonding shear property of old concrete damaged in freez e-thaw environment to young concrete

Using shear Z-shape specimens composed of young and old concrete, t he bonding shear strength and failure mechanism of young to old concrete were co nducted where the old concrete had been exposed to freezing-and-thawing cycles . The old concrete were experienced zero, 25, 50, 75 and 100 and 125 freezing cy cles. Freezing cycles, interfacial roughness (0.23-6.9mm )and interfacial adhes ion agents including cement paste, cement mortar and cement paste with 10 per ce nt UEA expanding agent were also investigated. The results indicated that the bo nded shear strength decreases with the increase of the numbers of freezing-and-thawing cycles, and that the shear strength performs slightly decreasing at th e early stage of freezing and declines suddenly after a certain freezing-and-t hawing cycles. The sharp degenerate point occurs at 75 freezing cycles, which al most accords with the critical point of relative dynamic modulus of elasticity i n frost resistance standard. The interfacial roughness and adhesion agent have d ifferent effects on the bonding strength. In three kinds of handling interfacial methods, to a certain numbers of cycles, the adhesive effectiveness of chipped surface combined with cement mortar is the best.