Improvement of hardened concrete durability by nanosilica electromigration

Abstract

Application of nanotechnology in construction industry is a quite new field with many interesting and promising possibilities. Nanosilica self healing properties, based on the high reactivity of these particles with the calcium components of cement, are of great interest in rehabilitation treatments of hardened concrete. In present work, the application of nanosilica to hardened concrete is proposed as innovative technology to improve the effectiveness of electrochemical repair methods and to increase the durability of rehabilitated structures by sealing the concrete pores. An accelerated methodology, compatible with the electrochemical repair treatments of concrete, is proposed to introduce nanosilica in hardened concrete by connecting an external electric field. Two different commercial products with SiO2 of 7 nm and 12 nm in diameter have been analysed. Silica nanoparticles have been transported through a mortar sample under a 12 V electric field. The interaction between the SiO2 nanoparticles and the concrete have been characterised by different techniques: resistivity measurements, mercury intrusion porosity, scanning electron microscopy. The results show that the interaction concrete/nanosilica takes place in the first centimetre of concrete cover from the surface of the nanosilica application. A denser microstructure with higher content of capillary pores is obtained after the nanosilica penetration. Also the resistivity of the mortar increases due to the treatment with nanosilica.