Effect of curing conditions, slag type and replacement level on the transport properties of composite cements

The partial replacement of Portland cement (OPC) with ground granulated blast furnace slag (GGBS) is a common practice both here in the UK and on an international level. It serves to reduce both embodied energy and embodied carbon whilst making use of an industrial by-product, creating a double saving through negating the need for landfilling. It has been found that such composite cements have the ability to improve physical and chemical performance through their hydration within a cementitious matrix; however their reduced rate of hydration compared to pure OPC means that they are more susceptible to changes in curing conditions. This study has been performed in order to assess and compare the effects of variations in curing conditions on the performance of these composite cements. Samples were prepared from CEM I with 0, 40 or 70% replacement by GGBS and cured either in ‘field’ conditions (externally, within a sheltered area) or in ‘ideal’ conditions (in a curing room at 20°C ±1°C and 98% RH) for 28 and 56 days. UCS, permeability and sorptivity were measured with additional characterisation via SEM-BSE.