Experimental Evaluation of the Effect of Water-Cement Ratio on Compressive, Abrasion Strength, Hydraulic Conductivity Coefficient and Porosity of Nano-Silica Concretes

Dams are considered as strategic structures due to their initial role in economic system of the country, therefore, they are expected to be fully functional and powerful. Nano technology could be an effective factor of abrasion and compressive strength, porosity and hydraulic conductivity coefficient of the concrete, thus more scientific research is essential to be carried out on these types of concrete due to their quite modern and high technology. In the current study, the effects of water-cement ratio on compressive and abrasion strength, porosity and hydraulic conductivity coefficient of concrete was investigated. The constructed concrete samples with 4% Nano-silica and water-cement ratios of 0.35 to 0.55 were tested. Other design features remained fixed in all concrete samples. The compressive strength of block samples of 150×150×150 mm were assessed in terms of time lasting 7, 28 and 90 days. The abrasion strength of the identical block samples were tested after 28 days. The hydraulic conductivity coefficient of cylindrical shape samples with the diameter 150 mm and height of 300 mm were experimented after 28 days. The results of the experiments indicated that by reducing the water-cement ratio from 0.55 to 0.35, the compressive strength increased 37.13, 40.14 and 38.22% for 7, 28 and 90 days age samples respectively and abrasion strength of concrete increased 38.22% and the hydraulic conductivity coefficient (m/s) and depth of penetration (mm) of the concrete decreased from 27.76×10⁻¹⁵ and 2.756 to 1.5×10⁻¹⁵ and 0.784 respectively. In addition porosity decreased from 12.76 to 11.22%.