Hollowcore slab with alternative cementitious materials for winter conditions

Abstract

The precast industry, due to its specific early age strength requirements for hollowcore (HC) slab products, has been reluctant to introduce alternative cementitious materials like ground granulated blast furnace slag (GGBS), due to the slower strength development of such materials. This paper reports on a study undertaken at a precast production facility to examine how to overcome the consequences of strength loss due to replacement of up to 50% of the CEM I (42·5R), as usually used in cold weather conditions, with GGBS, for environmental or durability reasons. The GGBS concrete slabs were activated using thermal, chemical and mechanical means to enhance early age strength gain. The results were compared at early ages in terms of temperature profile during curing, cube compressive strengths, load carrying capacities for transportability requirements, ultimate load and short term creep. In addition, 28 day densities and strengths were compared for in-situ cubes and cores extracted from HC slab samples. The experimental results showed a favourable potential for replacing CEM I (42·5R) cement with up to 50% GGBS in winter without compromising on factory productivity.