Effect of Mixing Methods of Nano Silica on the Properties of Recycled Aggregate Concrete

Abstract

Concrete is generally a mixture of granular materials of diverse sizes and the size range of the created solid mix, covers varied intervals. The properties of the concrete in the fresh state (flow properties and workability) are governed by the particle size distribution (PSD), however, the properties of the concrete mix in the hardened state, such as strength and durability, are largely affected by the mix grading and the resultant particle packing. Another way to further enhance the packing of the particles is to increase the solid size range. Individually, the progress in nanoscience had caused a tremendous influence on the concrete industry. Over the past decade,nanomaterials have been used in the concrete industry. It has been shown by the research that incorporation of nanoparticles in cement environment could highly improve mechanical properties and durability of cement-based materials. The research work on "effect of mixing methods of nano silica on the properties of recycled aggregates concrete (RAC)" aims at analyzing the effect of mixing methods on concrete with a view of their benefits for concrete production. The objective of research work was to determine the mixing method that gives more improvement in properties of RAC. Concrete was design and tested as per IS code. As comparing of mixing methods of nano-silica in RAC, the presoaking of RAC in NS solution gives better performance than the direct mixing of NS in concrete. In this investigation, four series are considered. First and second series are controlled series that contains 100% Natural Course Aggregate (NCA) and 100% RAC, respectively. In the third series, 2% of NS used through direct mixing and in the fourth series, 2% of NS used through presoaked RAC in NS solution in concrete. Results show the better improvement in the mechanical and durability properties of presoaked RAC in NS as compared to the direct mixing of NS in concrete. The reduction in water absorption, sorptivity, RCPT and water permeability in presoaked RAC in NS as compared to the direct mixing. With presoaked RAC in NS fills the micro-cracks and pores and densified the microstructure, resulting in an improvement in properties.