G George Quercia

Effect of Olivine Nano-silica Additions on Cement Based System

In this study, the influence of olivine nano-silica (OnS) additions in cement based systems has been addressed. The obtained results demonstrate that the addition of OnS (1.5–3.8 % bwoc) increases the viscosity, yield point and hydration degree of the cementitious systems, mainly due to the increase of the total specific surface area of the mix. This holds also for the case when a fixed amount of SP is applied. Based on the performed analysis, it is concluded that the OnS acts as an accelerating and pozzolanic agent in concrete.

Hydration kinetics study of class G oil-well cement and olivine nano-silica mixtures at 20–60 °C

In this study the heat evolution of standard density slurries (1.89 g/cm3) of Class G oil-well cement and olivine nano-silica additions (0.5–2.0 % bwoc), cured under different temperatures (20–60 °C) and atmospheric pressure, were examined by isothermal calorimetry. Under isothermal and isobaric conditions, the dependency of cement hydration kinetics on curing temperature is related to the activation energy of the cementing slurry. The estimated apparent activation energy of the different slurries with olivine nano-silica varies from 38 to 44 KJ/mol using a dynamic method, at the temperature range of 20–60 °C. It is demonstrated that the addition of olivine nano-silica increases the rate and the heat of hydration of oil-well slurries. These effects are temperature dependent. Finally, comparable hydration degrees were obtained between slurries containing 0.5 % bwoc of olivine nano-silica and 10 % bwoc of oil-well grade micro-silica (mS).

Effects of Nano-silica (NS) Additions on Durability of SCC Mixtures

In this study, three different types of nano-silica were applied in self-compacting concrete (SCC), one produced by the controlled dissolution of the olivine mineral and two having similar particle size distributions (PSD), but produced through two different processes: fumed powder nano-silica and precipitated silica in colloidal suspension. The influence of the nano-silica on SCC was investigated with respect to the properties of the concrete in fresh (workability) and hardened state (durability properties). Additionally, the densification of the microstructure of the hardened concrete was analyzed by SEM and EDS techniques. The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its durability properties. Considering the reactivity of the different nano-silica studied, the colloidal type showed a higher reactivity at early age, which influenced the final SCC properties.