Effect of fillers on the behaviour of heavy-weight concrete made by iron sand

Abstract

Heavy-weight concrete refers to the concrete with unit weight ≥ 2600 kg/m3, which is produced using high-density (specific gravity ≥ 3.0) aggregates. It is commonly adopted as the construction material in nuclear power stations and nuclear medicine facilities due to its superior radiation shielding performance. However, the mechanical properties, especially passing ability of heavy-weight concrete reduced significantly since the cement paste is not able to hold the high-density aggregates firmly. To solve this problem, cementitious fillers, such as silica fume (SF) and fly ash (FA) was adopted, which was well-known to be effective in increasing the flowability by improving the wet packing density (WPD) such that more excess water could be produced to lubricate the solid particles. Moreover, the fillers could enhance the segregation resistance by increasing the fine powders content. Therefore, in this paper, a total of 75 heavy-weight concrete mixes with and without SF or FA partially replacing cement were designed and tested for their flowability, segregation resistance, passing ability, unit weight and compressive strength. Results demonstrated that SF could improve the passing ability and WPD simultaneously whereas FA could improve passing ability but not necessarily WPD of heavy-weight concrete. At last, at a given cementitious materials composition, the passing ability could be positively correlated to WPD of heavy-weight concrete.