Study On Thermal Expansion And Thermal Conductivity Of Ultra High Toughness Cementitious Composites

Ultra High Toughness Cementitious Composites(UHTCC) is a new kind of high performance fiber reinforced concrete.It shows prominent toughness and superior durability, and has been successfully applied to many practical projects in the world.So far,researches about UHTCC have been focused on mechanical properties,shrinkage and so on,while thermal property of UHTCC has not been studied yet.Hydration heat of cementitious materials and hot environment will cause nonuniform deformation and huge thermal stresses.These phenomena will accelerate extension of cracks,facilitate penetration of harmful substances into steel surface,and eventually decline the durability of structures.Besides,to ensure the ability of UHTCC to work with concrete and steel bars,and establish more advanced structures,it is very important to research on thermal expansion and thermal conductivity of UHTCC.This paper used fiber optical sensors,thermal expansion determination equipment and strain gauges to measure the coefficient of thermal expansion(CTE) of UHTCC and concrete in the temperature range of 25℃-70℃.Three methods were compared,and inaccuracy was analyzed in the process of experiments.Based on previous researches,this paper studied the ability of UHTCC to work with concrete and steel bars.What's more,coefficient of heat conductivity of UHTCC was measured,and the process of thermal conductivity was stimulated with Ansys.The major contributions are summarized as follows:In the temperature range of 25℃-70℃,the CTE of UHTCC is between 7×10^-6℃^-1 and 9×10^-6℃^-1,the CTE of concrete is 9.1×10^-6℃^-1;the CTE of steel bar is 12×10^-6℃^-1.So that UHTCC could cooperate with concrete and steel bars under thermal environment,in that CTE of the three materials are very close.Coefficient of heat conductivity of UHTCC is 0.529w/m·k, which is lower than concrete and mortar.In the simulation of thermal conductivity,it is proved that the heating process in the CTE measurement experiments with fiber optical sensor and strain gauges is reasonable.