EXPERIMENTAL STUDY ON STRENGTHS OF STEEL FIBER REINFORCED CONCRETE WITH EARLY-AGE LOADING HISTORY

An experimental research project was carried out to determine the modulus of rupture,splitting tensile and compressive strengths of steel fiber reinforced concrete(SFRC) ever loaded at early ages.The specimens were first subjected to a load nondestructively at early ages and their strengths were then tested at age of 28 days.The effects of the age and the stress level of the early loading,as well as the contents of steel fibers,were investigated.The test results were then compared with those for plain concrete specimens.It shows that the early-age loading decreases the 28-day strengths of SFRC and this unfavorable effect is smaller than that for plain concrete because of steel fibers.With the increase of the contents of steel fibers,the 28-day strengths of SFRC influenced by early-age loading can be significantly improved,especially for the modulus of rupture and the splitting tensile strength.This is a useful measure in engineering practice to avoid severe weakening of concrete when it has to be heavily loaded at very early ages.