Optimizing the use of recycled concrete fines in slag-cement

Ground granulated blast furnace slag (GGBFS) can be blended at fairly high proportions with ordinary Portland cement to produce a material with excellent long-term strength properties. This combination has the advantage of reducing both the amount of energy required for production as well as the amount of carbon dioxide released. Unfortunately, when high proportions of slag (25 to 40 % or more) are used, the early rate of reaction is slow. The addition of recycled concrete fines to interground slag-cement allows for the further reduction of Portland cement in the final mixture, and in some cases improves the early reaction rate of the blend.