Akademik Veri Yönetim Sistemi
IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY-TRANSACTIONS OF CIVIL ENGINEERING, cilt.47, sa.1, ss.265-280, 2023 (SCI-Expanded)
In this study, the effects of different percentages of fly ash (FA), silica fume (SF) and fly ash + silica fume had on the mechanical and microstructural properties of hardened cement paste (C-S-H ve CH) and concrete were investigated. Portland cement was replaced with fly ash, silica fume and fly ash + silica fume in quantities of 5%, 10%, 15%, and 20% (in terms of weight) of cement. The mechanical properties, compressive strength and microstructures of the samples were investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. According to the results, fly ash adversely affects the compressive strength of concrete in 7 days, while it increased compressive strength in 28 and 90 days of age. In concrete using silica fume, a higher compressive strength was obtained compared the control sample at all ages. In samples containing silica fume, the highest compressive strength was obtained by using 15% silica fume, 10% fly ash in the samples containing fly ash, and 15% in the case of silica fume and fly ash together. In the XRD analysis, the rate of CH formed as a result of hydration decreased with age and the ratio of fly ash, silica fume and fly ash + silica fume used. SEM analysis showed that the use of fly ash and silica fume decreased the voids and increased the C-S-H ratio. It was found that there was a linear relationship between the increase in C-S-H ratio due to the increase in silica fume and fly ash ratios used, and an inversely proportional relation between the CH concentrations. This is caused by the reduction of the amount of Ca(OH)(2) due to the reaction between fly ash and silica fume and calcium hydroxide (Ca(OH)(2)) and filling the gaps. The resulting portlandites combine the cement hydrate with the resulting fly ash of the resulting C3S and C2S to form C-S-H. Additionally, in the study, a model was developed to estimate the compressive strength of concrete in the direction of the data obtained from SEM and XRD analyses. The CH and C-S-H densities, silica fume ratio, fly ash and wet parameters obtained from modeled SEM and XRD data obtained on artificial neural networks (ANN) were taken as inputs and compressive strength were obtained. The results obtained from the model were compared with the results obtained from the experiments and 96.76% correct results were obtained. With this method, it is seen that the concrete pressure density can be calculated from the results obtained by SEM and XRD analysis of a small concrete sample without destroying the existing structure. According to the SEM and XRD results, a method has been proposed for estimating the compressive strength of concrete by non-destructive methods with the model developed using artificial neural networks.