Accelerated Curing of Silica-Fume Concrete

Abstract

Silica fume is a common addition to high-performance concrete mix designs. The use of silica fume in concrete leads to increased water demand. For this reason, Florida Department of Transportation (FDOT) allows only a 72-h continuous moist cure process for concrete containing silica fume. Accelerated curing has been shown to be effective in producing high-performance characteristics at early ages in silica-fume concrete. However, the heat greatly increases the moisture loss from exposed surfaces, which may cause shrinkage problems. An experimental study was undertaken to determine the feasibility of steam curing of FDOT concrete with silica fume in order to reduce precast turn around time. Various steam-curing durations were utilized with small laboratory specimens. The concrete compressive strength, surface resistivity, and shrinkage were determined for various durations of steam curing. Results indicate that steam cured silica-fume concrete met all FDOT requirements for the 12, 18, and 24h of curing periods. All steam cured samples demonstrated excellent durability up to 1 year of age. It was recommended that FDOT allow 12h steam curing for concrete with silica fume.