Cavitation Properties of Rendering Mortars with Micro Silica Addition

Abstract

Micro-silica is a highly efficient mineral additive whose role is reflected in improvements of microstructure packing, strength and durability of non-shaped composite building materials such as concrete and mortar. A comparative study of performances of rendering mortars with different quantities of micro silica was conducted. The experimental program included production of reference mortar based on Portland cement and quartz sand (CM) and three mortars with 5, 10, and 15 % addition of micro silica (SCM-5, SCM-10, and SCM-15). The effect that micro silica addition has on the thermal behavior and mechanical properties of mortars was discussed. Hydration mechanisms and thermally induced reactions were studied at temperatures ranging from ambient to 1100 °C by differential thermal analysis. The results were supported by X-ray diffraction analysis. The cementing efficiency of micro silica was assessed by cavitation erosion test. The changes in the morphology of mortar samples prior and upon cavitation testing were monitored by means of the scanning electron microscope imagining. It was found that 5 % of superfine micro silica (SCM-5 mortar) has positive effects on mechanical strengths (15 % increase in compressive strength) due to microstructure densification arising from the successive filling of voids by the micro silica. Addition of micro silica also improved the cavitation erosion resistance in comparison with reference cement mortar (SCM-5 showed cavitation velocity as low as 0.09 mg/min). This qualifies mortars with micro silica addition as building materials which can be safely employed in potential hydro-demolition environment.