Experimental Research On Fire Performance Of Steel Fiber Reactive Powder Concrete

Reactive powder concrete(RPC)is a material of high strength, high tough-ness and high durability,most of RPC are mixed with fiber materials such as steel fibers.The mechanical properties of steel fiber RPC in high temperature have not been reported until now, therefore, the experimental study on fire performance of steel fiber RPC has important practical significance.Full curves of uniaxial stress-strain relationship of steel fiber RPC under normal as well as high temperatures is established by experiments to determine the influence of the dosage of steel fibers and temperature on the high-temperature behavior (prism compressive strength, peak strain, initial elastic modulus, peak secant modulus, compressive toughness and crack form ) of steel fiber RPC. Rigid components are used to achieve the measurement of the descending branches of the stress-strain curves. 45 prim specimens with the size 70.7mm×70.7mm×228mm are fabricated and divided into three groups, of which the volumetric con-tent of steel fibers is 1%, 2%, 3% respectively. Test of full stress-strain curves is immediately carried out as the temperature interior the specimens is consistent with that exterior under five temperature cases , i.e. 20℃, 200℃, 400℃, 600℃, 800℃.It is found that the free expansion deformation and the peak strain of steel fi-ber RPC increase as the temperature rises, whereas, its prism compressive strength, initial elastic modulus and peak secant modulus reduce drastically. The prism compressive strength at T=200℃, 400℃, 600℃and 800℃is approximately 76%~82%, 53%~62%, 33%~42% and 14%~19% of that under normal temperature, respectively. However, no significant influence of the steel fiber on the high-temperature free expansion deformation, peak strain, initial elastic modulus and peak secant modulus is observed. In the low temperature zone, the prism compres-sive strength and the compressive toughness increases as the dosage of steel fiber is raised, on the other hand, RPC with the steel fiber content of 2% indicated the maximum strength and considerable toughness in the high temperature zone. The crack form of the steel fiber RPC are mainly diagonal crack and vertical crack,shifting from the former to the latter as the content of steel fibers and tem-perature increase.The stress-strain curves of steel fiber RPC under high temperatures are nor- malized and the unixial compression constitutive model of steel fiber RPC under high temperatures is proposed. The constitutive model is in good agreement with experimental results, it can provide the basis for fire-resistant analysis and design of RPC structure and element.