Efficiency of limestone in clinker-reduced binders: Consideration of water-binder ratio, capillary porosity and compressive strength

Multicomponent binders of Portland cement (C) in combination with granulated blast furnace slag (S) and limestone powders (LP), that can make a significant contribution to the desired decarbonization of the cement and concrete industry in the next few years, are investigated in this study. Considerably altered porous microstructure – i.e. increased specific inner surface and gel volume content as well as coarsened capillary porosity are observed, especially in case of ternary blends (C/S/LP) compared to binary (C/S) and (C/LP) mixes. A beneficial effect of LP on enhancement of hydration of C and S contributed to the compressive strength development, particularly between the first and 28th day of curing with an appropriate content of very fine LP at low w/b (water/binder) values. The effect of LP in the mix design can be described very well by means of an adjusted w/b_eff (with k_L = 0.15 of the LP). This is clearly displayed by very good correlations of w/b_eff and compressive strength as well as capillary porosity. The findings of this study provide guidance for optimizing the mix design of clinker reduced multicomponent mixes in order to reliably estimate their performances.