Title: Effects of Different Fibers and Cement Substituting Minerals on Mechanical Properties of Ultra-High- Performance Fiber-Reinforced Concrete

Author(s): Nima Mohammadian Tabrizi, Davood Mostofinejad, and Mohammad Reza Eftekhar

Publication: Materials Journal

Volume: 120

Issue: 5

Appears on pages(s): 15-30

Keywords: cement replacement materials; curing; mechanical properties; synthetic fiber; ultra-high-performance concrete (UHPC)

DOI: 10.14359/51738888

Date: 9/1/2023

Abstract:
This paper is aimed at investigating the effects of different fiber inclusion on the mechanical properties of ultra-high-performance concrete (UHPC) by adding mineral admixtures as cement replacement materials to reduce production costs and CO2 emissions of UHPC. Throughout this research, 21 mixture designs containing four cement substitution materials (silica fume, slag cement, limestone powder, and quartz powder) and three fibers (steel, synthetic macrofibers, and polypropylene) under wet and combined (autoclave, oven, and water) curing were developed. To investigate the mechanical properties in this research, a total of 336 specimens were cast to evaluate compressive strength, the modulus of rupture (MOR), and the toughness index. The findings revealed that at the combined curing, regarded as a new procedure, all levels of cement replacement recorded a compressive strength higher than 150 MPa (21.76 ksi). Furthermore, the mechanical properties of the mixture design containing microsilica and slag (up to 15%) were found to be higher than other cement substitutes. Also, it was shown that all levels of the fiber presented the MOR significantly close together, and samples made of synthetic macrofibers and steel fibers exhibited deflection-hardening behavior after cracking. The mixture design containing microsilica, slag, limestone powder, and quartzpowder, despite the significant replacement of cement (approximately 50%) by substitution materials, experienced a slight drop in strength. Therefore, the development of this mixture is optimal both economically and environmentally.