Influence of limestone addition on the engineering and durability performance of Portland-blast furnace slag blended concretes

Abstract

The widespread use of ternary cement produced from Portland cement (CEM I), granulated blast furnace slag (GGBFS) and limestone powder in structural concrete can be anticipated given the recent standardisation of such ternary cements in EN 197–5. However, understanding of these cements is limited to paste or mortar-scale studies, and comprehensive studies on concretes produced from such cements are needed urgently. In this study, fresh and hardened properties including strength, elastic modulus, water absorption and chloride permeability of ternary cement concrete comprising 50 wt% CEM I blended with GGBFS and 10 or 20 wt% limestone are investigated, as a function of the curing duration. Reducing the GGBFS content, by replacing it with 10–20 wt% limestone powder, leads to satisfactory mechanical and durability properties relative to binary and CEM I concrete. It was established that the ternary concretes evaluated exhibit a progressive increase in compressive strength, reaching values comparable to those of the reference CEM I concrete by 365 days of curing. The flexural strength, static and dynamic elastic moduli of the GGBFS-containing concretes, with or without limestone, are comparable to CEM I concrete, at the investigated curing ages. The chloride permeability and water sorption studies demonstrated that concrete made of composite cements containing up to 20 wt% limestone has no detrimental implications on the resistance to chlorides and water ingress. This study also demonstrates that the mechanical properties of concretes with high replacement of blast furnace slag in Portland blended cements, with or without limestone, are compliant with ACI, fib and Eurocode 2 for structural concrete applications.