Development of Cement-Free Concrete Using Finely Grained Slag for Portland Cement

The present study concerns a development of cement-free concrete using finely grained ground granulated blast furnace slag (GGBS) rather than ordinary Portland cement (OPC) as a binder in concrete mix. The GGBS was very finely ground to the level of 10,000 cm(2)/g, prior to casting concrete, compared to OPC of which the Blaine value accounts for about 3,200 cm(2)/g. In concrete casting, the NaOH activator was added to mixing water to enhance the hydration rate for cement-free concrete. To ensure the compatibility of GGBS in concrete, a development of concrete strength, ionic penetrability and pore structure were examined. As a result, it was found that cement-free concrete using the GOBS has a higher concrete strength at all ages from 7 to 56 days. In turn, the ionic penetrability, in terms of chloride diffusivity, was slightly lower in cement-free concrete than OPC concrete, presumably due to the dense pore structure, which was confirmed by the mercury intrusion porosimetry. Simultaneously, the adiabatic temperature for cement-free concrete initially rose more rapidly, leading to an accelerated hydration process. This suggests that the cement-free concrete containing GOBS can be used for structural concrete structures, imposing an economical benefit and structural stability.