An Experimental Study on Bond Strength of Reinforcing Steel in High-Volume Fly-Ash Concrete

Abstract

The production of Portland cement—the key ingredient in concrete—generates a significant amount of carbon dioxide. However, because of its incredible versatility, availability, and relatively low cost, concrete is the most consumed manmade material on the planet. One method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. An experimental investigation was conducted to compare the bond strength of reinforcing steel in high-volume fly-ash concrete (HVFAC)—concrete with at least 50 % of the cement replaced with fly ash—with conventional concrete (CC). This study investigated two HVFAC mixes [with one mix having a relatively high total cementitious content (502 kg/m3) and the other mix having a relatively low total cementitious content (337 kg/m3)], as well as a CC mix. Both HVFAC mixes utilized a 70 % replacement of Portland cement with a Class C fly ash. This experimental program consisted of 18 pull-out specimens, as well as nine full-scale beams (three for each concrete type). The pull-out specimens were based on RILEM recommendations, and the beam specimens were tested under a simply supported four-point loading condition. The CC test results served as a control and were used to evaluate the results from the HVFAC pull-out and beam specimen tests. Furthermore, a comparison was performed between results of this study and a bond database of CC specimens. These comparisons indicate that HVFAC beams possess greater bond strength than CC beams.