In situ examination of engineered local additives in cement paste via neutron based scattering techniques

Hydration behavior of cements with additives is complicated due to the multifarious nature of hydration products formed at various stages of hydration. Neutron-based scattering techniques are useful in detecting both the microstructural evolution and water dynamics of hydrating cement pastes. This work investigates the effect of early-age hydration on microstructural evolution of cement paste with local volcanic ash using neutron-based beamline techniques. Early-age hydration dynamics of Portland cement paste with volcanic ash was examined via inelastic neutron scattering (INS), while the evolution of microstructure was observed with small angle neutron scattering (SANS). The data obtained from the ratio of volume fractal to surface fractal clearly showed that greater than 30% substitution of volcanic ash leads to unreacted volcanic ash and coarser morphology, which could influence the chemo-mechanical properties of the resulting hydration products. INS results showed that the effect of finer-particle-sized volcanic ash contributes to initiation of gelation, which accommodates higher conversion of free water to bound water. The multi-scale analysis that combines a time-resolved study of water dynamics along with microstructure is found to provide a basis for effectively utilizing engineered additives for the local cement industry.