effects of SiO₂ nanoparticles on physical and mechanical properties of high strength compacting concrete

In this work, compressive, flexural and split tensile strengths together with coefficient of water absorption of high strength self compacting concrete containing different amount of SiO₂ nanoparticles have been investigated. Strength and water permeability of the specimens have been improved by adding SiO₂ nanoparticles in the cement paste up to 4.0wt.%. SiO₂ nanoparticle could accelerate C–S–H gel formation as a result of increased crystalline Ca(OH)₂ amount especially at the early age of hydration and increase the strength of the specimens. In addition, SiO₂ nanoparticles are able to act as nanofillers and recover the pore structure of the specimens by decreasing harmful pores. Several empirical relations have been presented to predict flexural and split tensile strength of the specimens by means of compressive strength at a certain age of curing. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all also indicate that SiO₂ nanoparticles up to 4wt.% could improve the mechanical and physical properties of the specimens.