Nano-ChemoMechanical assessment of Rice Husk Ash cement by wavelength dispersive spectroscopy and nanoindentation

Abstract

Cement global production stands at 3 Giga tons making concrete the most consumed structural mateial worldwide. This massively produced material comes with a heavy environmental footprint rendering the cement industry contributing about 5% to global CO₂ emission. Rice Husk Ash (RHA) among many other silicious materials, has the potential to partially replace cement and enhance the properties of the final product. The goal of this thesis is an investigation of the fundamental properties of RHA cement. For a set of RHA cement paste samples, we investigate at the nano-scale the effect of RHA incorporation on chemical and mechanical properties of cement. RHA is found to have high pozzolanic properties through its reaction with portlandite to form different types of calcium silicate hydrate (C-S-H). It is found that C-S-H in RHA cement has lower Ca/Si ratios compared to pure ordinary portland cement (OPC) samples prepared under the same conditions. Incorporation of RHA has minor effect on the mechanical properties of cement paste at the nano scale for low water-to-binder ratios while significant improvement in mechanical properties is found at high water-to-binder ratios. We arrive at these conclusions as a result of a dual chemical-mechanical analysis at the nanoscale in which electron probe microanalysis (EPMA) and nanoindentations are employed.