Statistical properties of steam-cured plant-produced SCC for prestressed precast applications

Self-consolidating concrete (SCC) has been in the last years increasingly used by precast construction industry due to its superior fresh state performance which may significantly optimize the whole manufacturing process. As a matter of fact for prestressed elements accelerated curing is performed to rapidly achieve the strength required for prestressing release. In this paper a comparative study on the strength development due to accelerated heat curing has been performed with reference to an ordinary and a self consolidating concrete, designed for the same target strength (fck = 45 N/mm2 at 28 days) and employed for precast prestressed roof elements. With reference to 15 months of continuing concrete production (April 2007-June 2008) data referring to fresh state properties (slump/slump flow and air entrainment) and compressive strength tests at different ages (16 hours, 7 and 28 days) have been analyzed in order to calibrate a strength development law and assess the role of mix constituents (limestone filler) and seasonal temperature variations on the strength development as well as on the robustness of the production. This also in the sight of a better calibration of strength reduction factors for the limit state design in the framework of the Eurocode approach. The study is the first part of a wider investigation aimed at assessing the effect of heat curing on the physical and mechanical properties of self consolidating concrete for precast application with reference to ordinary concrete.