Mechanical properties and fracture parameters of ultra high performance steel fiber reinforced concrete composites made with extremely low water per binder ratios

Abstract

This study examines the effects of high-volume micro-steel fibers (MSF) content on the mechanical properties, fracture parameters, and ductility of ultra-high performance fiber reinforced concrete (UHPFRCs). The MSFs used in this experiment had an aspect ratio of 37.5 with average length of 6 mm. The investigated parameters include very low water/binder (w/b) ratio and fiber content. Sixteen UHPFRC mixes were examined, eight mixes were made with w/b of 0.12 and eight fiber contents (0%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5, 4%) while the other eight mixes were made with the same fiber contents but with w/b of 0.14. The UHPFRC mixes were examined for various strengths (compressive, splitting tensile, flexural), elastic modulus, and fracture parameters. The experimental results showed that the mixture with 4% of MSFs content and 0.12 w/b ratio exhibited a compressive strength of more than 160 MPa, splitting tensile strength higher than 12 MPa, and modulus of elasticity greater than 43 GPa. Moreover, the results also demonstrated that with increasing MSFs content from 0 to 4% the load-displacement behavior, ductility, and all other fracture parameters were improved significantly.

Mechanical and Fracture Parameters of Ultra-High Performance Fiber Reinforcement Concrete Cured via Steam and Water: Optimization of Binder Content

“…This may be attributed to the chemical and physical changes due to temperature and humidity effects on potential for the stress transfer. Additionally, the modulus of elasticity for the water-cured UHPFRC at 1150 kg/m 3 binder content achieved in this study was 41.15 GPa, whereas the modulus of elasticity for the same MSF content, w/b, and curing condition at 1175 kg/m 3 binder content achieved by Qadir et al [ 28 ] was nearly 40 MPa.…”

“…In addition, the reason for the necessary increasing of SP with a greater increase in binder after 1150 kg/m 3 may be attributed to the better dispersion of micro silica particles at 1200 kg/m 3 of binder used. It was also reported that for the production of UHPC with 2% MSF and 1175 kg/m 3 binder content at 0.12 w/b the SP demand was nearly 70 kg/m 3 [ 28 ].…”

“…Therefore, steam-cured concretes are superior to water-cured concretes. Likewise, Qadir et al [ 28 ] studied water-cured UHPFRC having 1175 kg/m 3 binder content with 2% MSF content and 0.12 w/b; a compressive strength of nearly 150 MPa was achieved. Additionally, Yu et al [ 49 ] observed that the use of 2% MSF in the UHPC increased the compressive strength from 99 to 120.8 MPa.…”

“…Similar results were detected for UHPC with 1175 kg/m 3 binder and 2% MSF. For 28 days water curing, the compressive strength increment rate was 26%, compared to the 7 days results [ 28 ]. The preferable nature of SC than WC is may be because of congestions of high hydration and pozzolanic reaction resulting from the ingredients of the ultra-amount of binder (850–1200 kg/m 3 ) and SF (127.5–180 kg/m 3 ) that activated dramatically by the high moisture and temperature of curing.…”

“…Commonly, the utilization of fibers improves the tensile strength of concretes. This might be attributed to the fact that the fibers enable blocking tensile cracks and then followed by limiting crack growth [ 28 ]. The variations of splitting tensile strength of UHPFRC with the different amount of binders and two curing conditions are given in Figure 5 .…”