Early-age properties and shrinkage induced stress of ultra-high-performance concrete under variable temperature and uniaxial restrained condition

Abstract

Researches have been continuously carried out on the mechanical properties and control measures on autogenous shrinkage of ultra-high-performance concrete (UHPC), while studies on the stress evolution and cracking behavior of UHPC under variable temperature and uniaxial restrained condition are insufficient. The development of restrained stress is not only closely associated with the elastic modulus and shrinkage, but also affected by creep. In this research, the volume deformation, stress evolution, and cracking behavior of UHPC incorporating steel fibres under variable temperature and uniaxial restrained condition were investigated by using temperature stress test machine, and the autogenous shrinkage, tensile creep, as well as stress relaxation were analyzed. The development of stress was aggravated by the shrinkage caused by the temperature drop and self-desiccation, which eventually resulted in the premature cracking of UHPC without fibres. The autogenous shrinkage of UHPC obtained from the free strain was reduced gradually when the volume proportion of fibres was raised. Incorporating steel fibres significantly reduced the early-age tensile creep of UHPC, and the tensile creep of UHPC changed little when the volume proportion of steel fibres was raised from 1.67% to 2.50%. The combined effect of creep and damage reduced the restrained stress by 77.3%, 76.1%, 76.1%, and 75.1% for UHPC incorporating 0%, 0.83%, 1.67%, and 2.50% volume proportion of steel fibres under the restrained condition, respectively.