As sustainability moves to the forefront of trends in construction, concrete mixture proportions must be adjusted and adapted to a new set of economic and environmental demands. While high-volume fly ash concretes have been investigated extensively since the 1980s, recently, renewed interest has been generated for these concretes as viable options to address sustainability concerns. The concurrent U.S. paradigm shift towards increasing limestone (filler) contents in cement-based systems has provided the impetus for investigating ternary blends consisting of fly ash, limestone powder, and cement. This paper presents results for the development of viable (economical and environmentally friendly) concrete mixtures based on the combination of a fine (~1 µm median diameter) limestone powder, either Class C or Class F fly ash, and either Type I/II or Type III portland cement. Mixtures that replace 40 % to 60 % of the portland cement on a volume basis with supplementary materials have been developed. These mixtures provide equivalent or superior performance to a conventional concrete mixture with a water-to-cement ratio of 0.40 on a mass basis, based only on ordinary portland cement. Performance has been evaluated by measuring setting times, compressive strength development, and durability-based transport properties such as electrical conductance (rapid chloride permeability test, RCPT) and surface resistivity. The different electrical property measurements are compared and found to be consistent with one another. At equal strength levels, the ternary blend concretes provide further reductions in RCPT values and increases in surface resistivity in comparison to the ordinary portland cement concrete, most likely due to the further refinement of pore structure in these concretes.
Citation: Concrete International
Pub Type: Journals
High-volume fly ash, limestone, sustainability, ternary blends, Type III cement.