Experimental Study On Bonding Property Between Steel Fiber And Mortar After High Temperature

Fire is one of the major disasters that threaten people’s personal safety and damage state property.Among them,building fire is one of the most serious kinds of fire.The fire in the building structure leads to the significant reduction or failure of the mechanical properties of concrete,which leads to the decrease of the safety level of the building structure,the failure to meet the requirements of the building code,and the possibility of the collapse of the building.In recent years,many scholars at home and abroad have conducted in-depth research on the mechanical properties of concrete and the maintenance and reinforcement of building structure after fire,and a series of achievements have been obtained.Steel fiber concrete(SFRC)is widely used in construction,water conservancy,transportation,marine and other engineering fields due to its good crack resistance,bending toughness and durability.Steel fiber concrete mainly improves the performance of ordinary concrete through the interfacial bonding between steel fiber and concrete matrix.Then,a lot of researches have been done on the interfacial bonding between steel fiber and concrete at home and abroad,but there is no systematic research on the interfacial bonding between steel fiber and cement mortar after fire.For this,strength grade of cement mortar,steel fiber type and fire simulation conditions are taken as parameters to systematically study the interface bonding performance of steel fiber and cement mortar after experiencing the effects of different fire simulation temperatures.The main research contents are as follows:(1)New bonding specimens and supporting test devices were used to pull out the 60 groups of steel fiber and cement mortar bond debonding out test specimens.The influence of steel fiber type and cement mortar strength on ultimate bonding strength and bond pulling energy consumption were studied at room temperature and simulated fire temperature(high temperature 200℃,400℃,600℃ and 800℃).The reasons for failure of the specimens were analyzed,and the effects of simulated fire temperature,steel fiber type and cement mortar strength on failure patterns were analyzed.(2)The damage degree of the ultimate bonding strength of the interface,the flexural and compressive strength of cement mortar were compared after high temperatures through testing the flexural and compressive strength of 25 groups of mortar prismatic specimens.The relationship between ultimate bond strength and temperature was studied,and the calculation formula of ultimate bond strength and temperature was established.(3)The microstructure of the interface between steel fiber and cement mortar,and the phase change of cement slurry are studied through modern microscopic analysis methods after different high temperatures.The damage mechanism of the interface performance between steel fiber and mortar matrix under high temperature conditions was analyzed.