Effects of ground granulated blast furnace slag in Portland cement concrete

Abstract

This research examined the impact of cement replacements with Grade 100 ground granulated blast furnace slag (GGBFS) on portland cement concrete performance. GGBFS was used to replace 0%, 30% and 50% of cement in a series of mixes with w/cm = 0.45 where primary variables were coarse aggregate type, cement manufacturer, and curing regime. The primary performance measures were compressive strength development and deicer freeze-thaw scaling resistance. The results show that the amount of time needed to reach 3000 psi traffic opening strength more than doubled from 3 days to 7 days with 30% GGBFS and to 10 days with 50% GGBFS. GGBFS concrete strength becomes comparable to ordinary portland cement concrete after 56 days. Deicer freeze-thaw scaling tended to increase with increasing GGBFS levels and appeared to be tied to the level of carbonation at the surface. Traditional curing methods were less effective with GGBFS concrete in providing a durable surface. In summary, under certain conditions Grade 100 GGBFS can be used successfully in Wisconsin pavements. The seemingly minor variations that result from different mix constituents in OPC appear to be accentuated in GGBFS concrete. A 50% GGBFS cement replacement level usually results in unsatisfactory performance from primarily a scaling perspective. A 30% GGBFS cement replacement level will often be acceptable but the outcome depends on the specific constituents and curing methods used.