Adoption of artificial lightweight aggregate in precast manufacture

Abstract

This study investigates the incorporation of lightweight sintered pulverised fuel ash (SPFA) as a partial/complete replacement for natural sand and aggregates within full-scale precast elements. It focuses on self-compacting concrete (SCC) mixes after short periods of strength development, owing to the lack of published experimental data for these concrete types and their significance in offsite manufacture. Aggregate failure means the use of SPFA reduces concrete capacity, particularly in shear and pull-out, and such reductions may be more prominent at an earlier stage of curing. These were investigated alongside the incorporation of steel fibres that may provide some compensation. The variation in the compressive strength obtained was less significant (3–5%), following 24 h of curing, than at 28 d (15%). A similar trend was observed across the range of densities and in the tensile and flexural strength tests, with a slightly increased workability also observed in the lightweight mixes. Similar testing of steel-fibre-reinforced concrete (SFRC) samples, with a 50 kg/m3 fibre content, challenges the appropriateness of current code design equations. More efficient element design may thus be possible for precast components where such design cases are prevalent. A 63% average increase in pull-out shear capacity also suggests an improved lifting capacity could be justified within precast elements.