Improving the passing ability of SSCA-IS ultra-heavy-weight concrete by optimizing its packing structure

Abstract

Heavy-weight concrete (HWC) is one of the most widely adopted radiation shielding material in the nuclear industry. In this study, two kinds of high-density aggregate, i.e., iron sand (IS) and steel slag coarse aggregate (SSCA), were adopted to fully replace river sand and natural coarse aggregate, respectively to make ultra-heavy-weight concrete (UHWC) with unit weight of more than 3800kg/m3 to ensure excellent radiation shielding performance. However, the use of IS and SSCA impaired the passing ability of UHWC seriously as the cement paste could not hold the IS and SSCA as firmly as natural aggregates owing to their high-density. To overcome this issue, the rheology of UHWC should be optimized, which could be achieved by replacing the cement with superfine silica fume (SSF) partially and using suitable amount of superplasticizer (SP) simultaneously to enhance the wet packing density (WPD) of UHWC. A total of 28 UHWC mixes with different replacement ratios of SSF (0%, 5%, 10% and 15%) and different dosages of SP were designed and the segregation width, flowability, L-box passing ability, unit weight and WPD were tested. Results revealed that incorporating an appropriate quantity of SSF and SP improved the WPD of UHWC, resulting in improved resistance to segregation, enhanced flowability, increased passing ability and a higher unit weight. Lastly, there exists a positive correlation between the flowability, passing ability and WPD of UHWC.