Experimental Study on Interfacial Bonding Property of New and Old Cement Mortar

Abstract

Abstract: Under the load and environmental factors, concrete structures suffer from varying degrees of deterioration. In order to ensure the safety and durability of the structures, it is necessary to repair the damaged cement-based materials. The bonding strength between repair mortar and matrix was influenced by the moisture state of old mortar, the roughness of interface, the water cement ratio of repaired mortar and the curing condition. Old mortars with different moisture states (0%, 30%, 70% and 100%) were selected as the matrix and then new mortars with water cement ratio of 0.4 and 0.6 were poured. The composite specimens were cured in sealing condition for 28 d. The shear test results show that when the water cement ratio of new mortar is 0.6 and the moisture states of old mortar change in the order of 70%, 30%, 100%, 0%, the shear strength gradually decreases. When the water cement ratio of new mortar is 0.4 and the moisture states of old mortar change in the order of 30%, 0%, 70%, 100%, the shear strength gradually decreases. Moreover, when the water cement ratio of new mortar is 0.4, the interfacial shear strength is generally greater than that when the water cement ratio of new mortar is 0.6. The interfacial roughness was changed by grooving method, and then the new mortar with water cement ratio of 0.6 was poured. The composite specimens were cured in standard condition. The shear test results show that when the interface is rough, the shear strength is 1.26 times of that when the old mortar is smooth. Old mortars with different moisture states (0% and 100%) were selected as the matrix and then new mortars with water cement ratio of 0.4 and 0.6 were poured. The specimens were cured in sealing and standard condition respectively. The experimental results show that when the moisture states of old mortar and water cement ratio of new mortar are the same, the shear strength in standard condition is obviously higher than that in sealing condition.

Key words: cement mortar, bonding strength, moisture state, roughness, sealing curing, shear test

CLC Number:

TU528

MENG Fanqiang, XUE Shanbin, ZHANG Peng, WANG Junjie, GAO Shizhuang. Experimental Study on Interfacial Bonding Property of New and Old Cement Mortar[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2020, 39(12): 3791-3798.

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