EFFECTS OF FLY ASH AND TiO2 NANOPARTICLES ON RHEOLOGICAL, MECHANICAL, MICROSTRUCTURAL AND THERMAL PROPERTIES OF HIGH STRENGTH SELF COMPACTING CONCRETE

Strength enhancement and durability-related characteristics and also the rheological, thermal and microstructural properties of high strength self compacting concrete (HSSCC) containing nano TiO2 and industrial waste ash (fly ash (FA)) were investigated. Portland cement was replaced by up to 15 wt% waste ash and up to 5 wt% TiO2 nanoparticles. It was found that, with the aim of energy saving and recycling of waste materials, FA addition as a natural pozzolan can improve the rheological, mechanical and durability properties of concrete at higher ages. Up to 4 wt% TiO2 nanoparticles as a partial replacement for cement could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence improve the microstructure of concrete, leading to improved durability-related properties and strength enhancement of the concrete. Empirical relationships to predict the flexural and split tensile strength of concrete based on compressive strength for HSSCC containing FA and nano TiO2 at different ages were obtained. An energy-based assessment of strength enhancement of nano-containing concrete is presented.