Ultra-high performance concrete and fiber reinforced concrete: achieving strength and ductility without heat curing

TLDR: In this paper, the packing density of the cementitious matrix was optimized by using very high strength steel fibers, tailoring the geometry of the fibers and optimizing the matrix-fiber interface properties.

Abstract: Ultra-high performance concrete (UHPC) and ultra-high performance fiber reinforced concrete (UHP-FRC) were introduced in the mid 1990s Special treatment, such as heat curing, pressure and/or extensive vibration, is often required in order to achieve compressive strengths in excess of 150 MPa (22 ksi) This study focuses on the development of UHP-FRCs without any special treatment and utilizing materials that are commercially available on the US market Enhanced performance was accomplished by optimizing the packing density of the cementitious matrix, using very high strength steel fibers, tailoring the geometry of the fibers and optimizing the matrix-fiber interface properties It is shown that addition of 15% deformed fibers by volume results in a direct tensile strength of 13 MPa, which is 60% higher than comparable UHP-FRC with smooth steel fibers, and a tensile strain at peak stress of 06%, which is about three times that for UHP-FRC with smooth fibers Compressive strength up to 292 MPa (42 ksi), tensile strength up to 37 MPa (54 ksi) and strain at peak stress up to 11% were also attained 28 days after casting by using up to 8% volume fraction of high strength steel fibers and infiltrating them with the UHPC matrix