Experimental Study On Bonding Properties Between Reinforcement And Concrete At Cryogenic Temperatures

The study on bonding properties between steel bar and concrete at cryogenic temperatures is a sub-topic of the researches on the mechanical performance of reinforced concrete at low temperatures(Natural Science Foundation (51078260)).The cooling equipment such as the cooling box was designed pre-independently, the existing loading device in the structure lab was modified in order to complete the study on bonding properties at cryogenic temperatures. Relevant formulas were put forward, and the work included as followings:According to the existing loading device in the structure lab, a loading program for the test was worked out, and a loading rack of test for the research was designed.The specimen of adhesive anchor pull-out test were divided into 4 large groups of A, B, C, D. Considering the impact of the parameters of temperature, the bar diameter, cover thickness, anchoring length, steel models, bonding properties between steel and concrete at ultra-low temperatures were analyzed. Six temperatures from 20℃to -165℃selected, considering the parameters above, total production of the specimen were 36 groups, three for 1 group, and the total specimen summed 108.Based on this test and analysis, the following basic conclusions can be obtained:Firstly, a test load rack was developed, and the reinforced concrete pull-out test could be completed easily and efficiently.Secondly, the bonding properties are significantly affected by temperature. The bonding strength increases linearly as temperature decreases in the temperature range from 20℃to -120℃, but the bonding strength remains unchanged for temperature range of -120℃to -165℃, .Thirdly, The increasing coefficient of bonding strength at low and cryogenic temperatures are affected by the parameters of temperature, cover thickness, concrete strength, bar diameter, anchoring length, and steel models. Temperature and cover thickness play a decisive role, the parameters of anchoring length and steel model are secondary factors, which can be ignored.Finally, bonding strength formulas at different low temperatures are proposed to provide a reference for the practical applications.