Application of nano-silica in concrete : annual project report 2012

This report presents the achievements of the third year focusing on the application of olivine nano-silica in concrete. One nano-silica sludge (nSS) and the precipitated nano-silica from Olivine dissolution in acid (OnS) were used for the experimental work on mortars and concrete scale. The activities performed include: a) Study of the dispersibility behavior of OnS particles in water (viscosity of the dispersion and selection of stabilization agents). b) Study of the effects of admixtures on cement/nano-silica pastes applying rheometric tests to assess changes in the viscosity caused by the volumetric substitutions of cement. These rheological tests were complemented with isothermal calorimetric measurements and standards mortar compressive strength test, c) Tests on mortar level were carried out using standard sand, cement and different commercial nano-silica to study the effect on the behavior in fresh state (slump changes) and to determine the pozzolanic effect of OnS on the compressive and tensile splitting strength. d) Test to determine the water demand and the workability on mortar scale of the OnS were performed (water layer thickness validation). e) Experiments were performed to determine the maximum amount of OnS to be used as cement replacement in normal (vibrated) and self-compacting concrete (SCC). f) Studies to determine the effect of nSS as a cement replacement in self compacting mortars (SCM) and self compacting concrete (SCC) at laboratory and pilot scales were finished. g) Based on the SCC laboratory test the potential reduction in the CO2 footprint of concrete was estimated. The aim of these activities was to establish the main characteristics of olivine nano-silica, and to select the best particle size range and concentration in order to continue with the subsequent tests as reported in the project plan. Some general conclusions and recommendations have been drawn from the results. Considering the conclusions and recommendations of the third year, further research and a new experimental setup was planned.