11 - Compressive strength and durability of high-volume fly ash concrete reinforced with calcium carbonate nanoparticles

Abstract

The effects of calcium carbonate (CaCO3) nanoparticles on the mechanical properties and durability of high-volume fly ash (HVFA) concretes containing 40 and 60wt% fly ash as the partial replacement of cement are evaluated in this study. In the first part of this study, the effect of CaCO3 nanoparticle contents in the range of 1–4wt% on the compressive strength of cement mortar is evaluated. It has been found that 1wt% CaCO3 nanoparticles exhibited the highest compressive strength of approximately 42MPa (∼22% higher than that of cement mortar). Accordingly, it was then selected and used to evaluate its effectiveness to improve the compressive strength of HVFA concretes containing 40 and 60wt% class F fly ash as the partial replacement of cement. The experimental results showed that the HVFA concretes reinforced with CaCO3 nanoparticles have reasonably higher compressive strength and high resistance to water sorptivity and chloride permeability when compared with the typical HVFA concrete counterparts. It is also found that 1wt% CaCO3 nanoparticles improves the microstructure by forming additional calcium silicate hydrate gels and decreases the porosity of HVFA concretes. It is also revealed that the addition of CaCO3 nanoparticles not only led to much denser microstructure in the HVFA matrix but also changed the formation of hydration products, hence contributing to improvement of the early age compressive strength and durability properties of HVFA concretes.