Modeling effect of SiO2 nanoparticles on the mechanical properties of the concretes

Abstract

In the present study, the effect of SiO2 nanoparticles on the mechanical properties (compressive, flexural and tensile strength) of the binary blended concrete is studied. SiO2 nanoparticles with two different sizes of 20 and 100 nm were used as partial cement replacement by 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0%. According to the obtained results, during the first few days of curing, the concrete specimens made with 20 nm SiO2 particles had a higher strength than those of 100 nm. It was interesting that in the last few days of curing, the situation was reversed. According to the SEM images, in the initial days of curing, a higher amount of C–S–H gel was formed around the 20 nm SiO2 particles compared to that of 100 nm ones. As an explanation for this event, one can mention to the presence of more nucleation sites which caused a significant acceleration in early age strength. It was while that, the growth of the C–S–H gel around the 100 nm particles was higher in 84 days of moist curing. An artificial intelligence based model was also presented for simulating the mechanical properties of the binary blended concrete. To construct the model, training and testing of the model were conducted by using experimental results from 51 specimens. The input parameters were five independent variables which consist of the number of the days of curing, quantity of SiO2 (%), quantity of SiO2 (kg), quantity of cement (kg) and the size of SiO2 nanoparticles. The training and testing results in the proposed model confirmed a strong capability for predicting mechanical properties of the binary blended concrete.