Characterisation studies on the particle size effect of calcium carbonate in high-strength concrete

Abstract

The main objective of this study was to determine the hydration activity and shrinkage of high-strength concrete (HSC) after the incorporation of different particle sizes of calcium carbonate (CaCO3). Three different sources of calcium carbonate – lime sludge (a residue collected from the paper and pulp industry, size ∼43 μm), commercial micro-calcium carbonate (size ∼13 μm) and commercial nano-calcium carbonate (size <100 nm) – were used as partial replacements of cement in HSC. Particle size analysis, heat of hydration, compressive strength and shrinkage aspects for various mixes were studied. The results showed an enhancement of the hydration reaction due to the nucleation effects of calcium carbonate and a considerable improvement in the reduction of shrinkage volume, hence the minimisation of shrinkage cracks. It was also found that shrinkage was significantly reduced with the incorporation of nano-sized particles rather than micro-sized particles. Compared with the control mix, all the mixes with different sizes of calcium carbonate showed a significant increase in compressive strength. To substantiate the obtained results, qualitative and quantitative analyses (X-ray diffraction, thermogravimetric analysis and differential thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy) were carried out to determine the hydration behaviour of cementitious pastes incorporating calcium carbonate without aggregates.