Study On The Behavior Of Bond-slip Of Geopolymer Concrete And Steel Section

Geopolymer concrete is a new building material with excellent mechanical and durability properties,which has a wide range of development prospects in civil engineering.Compared with traditional Portland cement concrete,geopolymer concrete releases less carbon dioxide in the production process,which can significantly mitigate the greenhouse effect.Research on geopolymer concrete has been increasing rapidly in recent years,but most of these studies focus on its material properties.As the research on geopolymer concrete develops,more and more attention has been paid to its application in practical engineering.In practical engineering,geopolymer concrete must be combined with steel.Moreover,their interaction is the basis for them to work together.Scholars have achieved some research results regarding bond-behavior between rebar and geopolymer concrete.However,there are few research reports on bond-behavior between steel section and geopolymer concrete,which leads to insufficient theoretical support when analyzing steel-reinforced geopolymer structures.Therefore,the paper focuses on the interface bond-behavior between steel section and geopolymer concrete,and the main research contents and results are as follows:(1)The whole process of crack development was observed through the put-out test of 15 steel-reinforced geopolymer concrete specimens.The failure pattern of the specimen was analyzed,and the bond-slip mechanism between steel section and geopolymer concrete was further studied.(2)Based on the test results,the load-slip curves of the specimens were obtained,and a typical curve model was determined.The curve can be divided into four stages:the no-slip stage,the load-increasing stage,the load-decreasing stage,and the horizontal residual stage.Three characteristic load values were defined,and the influencing factors of the characteristic load values were studied.The results showed a positive correlation between four design variables and characteristic load values.Moreover,the anchorage length of steel section had the most significant influence on characteristic load values,while the stirrup ratio had the most negligible influence.(3)The average bond strength was used as an indicator of the bond behavior of specimens.Three characteristic bond strength values were defined.The relationship between the four design factors and the characteristic bond strength of the specimens was studied by analyzing the characteristic bond strength value of the specimens.The results showed that there was also a positive correlation between four design variables and characteristic bond strength values.(4)By studying and analyzing bond-slip curves of specimens,a bond-slip constitutive relationship for steel reinforced geopolymer concrete was established.The fitted specimen bond-slip curves using this model had a high degree of agreement with experimental curves.Mathematical regression was used to determine calculation formulas for characteristic bond slip strength and characteristic slip values for steel reinforced geopolymer concrete.The error analysis of the calculation results is carried out,and the results of the formula meet the accuracy requirements.(5)Strain gauges were placed inside steel section to measure its strain.According to the strain data,the distribution law of bond stress on the anchorage length of the specimen is deduced.The result showed that bond stress was approximately exponentially distributed in the load increase stage.The closer to the loading end,the more obvious bond stress change.Mathematical fitting obtained mathematical expression for specimen bond stress by the ultimate state.The calculation result difference with experimental result small.(6)In ABAQUS software,the connector element was used to simulate the bond stress between steel section and geopolymer concrete.The results showed that positive stress along anchorage length decreased from the loading end to the free end.The normal stress distribution of geopolymer concrete is opposite.The simulation results show that the longitudinal shear stress on the section steel surface is uniformly distributed.The effect of bond stress on the inner side of the flange is strong,and the effect of bond stress on the outer side of the flange and the web is poor.The simulated load-slip curves of specimens agree with the test curves,which indicates that the method can simulate the bond stress of steel and geopolymer concrete wells.