Experimental investigation of thermal characteristics of Ultra high performance concrete

In the recent years، development in concrete technology results in production of ultrahigh performance fibre concrete. Having more than 150 MPa compressive strength and ductile behavior are two main characteristics of this concrete. Concrete structures experience different thermal conditions during their age and these conditions have direct influences on mechanical properties and durability of concrete. These effects can be natural atmospheric temperature difference or manmade conditions like fire. So investigation of temperature effects on concrete specially ultrahigh performance concrete which is expected to have high strength، is very important. In this research thermal characteristics of an ultrahigh performance concrete reinforced with steel fibres is investigated through calculating thermal expansion coefficient and resistance against high temperature. thermal expansion coefficient of ultrahigh performance fibre concrete is higher than high performance concrete and normal concrete. In high temperature experiment، in wet specimens، by increasing the temperature to 400 ºC the strength of specimens decreased. In dry specimens، ultrahigh performance concrete is more sensitive to temperature increase than high performance concrete.