Effects of nano-TiO2, nano-Al2O3, and nano-Fe2O3 on rheology, mechanical and durability properties of self-consolidating concrete (SCC): An experimental study

The objective of this study is to assess and compare the effects of different nanoparticles, namely nano-TiO2, nano-Al2O3 and nano-Fe2O3, on the performance of self-consolidating concrete (SCC) in terms of fresh, mechanical, and durability properties through performing different experiments. TiO2, Al2O3, and Fe2O3 nanoparticles with the average diameter of 18, 15, and 14 nm were used with two different contents of 3% and 5% by weight of cement. For assessing the fresh properties of SCC, slump flow, V-funnel, L-box, and column segregation tests were conducted. For the mechanical properties, compressive strength of concrete was investigated, and for the durability properties rapid chloride migration (RCM), electrical resistivity, rapid chloride penetration (RCP), and water penetration depth tests were carried out. The result showed that the workability properties of the mixes slightly improved by 3% addition of nanoparticles while increasing this value to 5% decreased the workability. For higher content of nanoparticles, the incorporation of nanoparticles in the mixes increased the water demand and consequently caused a reduction of workability. For compressive strength, nano-Fe2O3 showed a superior effect on the enhancement of strength in comparison to nano-Al2O3 and nano-TiO2. This observation was attributed to the formation of calcium ferric hydrate (C-F-H) gel in the microstructure. Moreover, the addition of all the nanoparticles resulted in an improvement of durability properties. High surface area of nanoparticles provided nucleation sites for cement particles and expedited the hydration process development. The formation of a higher content of hydration products helped the densification of microstructure. Moreover, nanoparticles controled the growth pattern of C-S-H gel, which led to the formation of a homogenous microstructure with smaller pore sizes and consequently to lower permeability against penetration of aggressive ions i.e., chloride. It is concluded that partial replacement of cement with nanoparticles on average improved the compressive strength and durability properties of SCC, but resulted in a reduction of workability. (C) 2020 Elsevier Ltd. All rights reserved.