Investigation of the effect of sodium hydroxide to sodium silicate ratio on compressive strength of geopolymer concrete containing recycled concrete aggregates: Experimental and modeling studies

Document Type : Original Article


1 PhD Student in Civil Engineering, Faculty of Engineering, Islamic Azad University of Roodehen, Tehran, Iran

2 Department of Civil Engineering, Roudehen Branch, Islamic Azad University, Roudehen, Iran

3 Assistant Professor, Department of Materials Engineering, Faculty of Engineering, Islamic Azad University of Roodehen, Damavand, Iran.


Geopolymer concrete has been proposed in recent years as a green alternative to conventional concrete, which can reduce the negative environmental effects of Portland cement production. In this study, the effect of three different factors such as metakaolin replacement, Na2Sio3/NaOH ratio and polypropylene fiber percentage on the compressive strength of geopolymer concrete at 7 and 28 days was evaluated. The results showed that with increasing the ratio of sodium silicate solution to sodium hydroxide, the compressive strength of concrete increases significantly up to 22%. Also, in the analysis of the metakaolin replacement per fly ash, it was concluded that with increasing the percentage of metakaolin replacement up to 30%, the compressive strength of the control sample increased to about 14%. Also, as a general result, adding polypropylene fibers up to 1.5% by volume did not have much effect on the compressive strength of geopolymer concrete. Moreover, the mixed designs obtained along with the compressive strength of the specimens were modeled using the artificial neural network and multivariate regression analysis. Based on the training and testing results, the artificial neural network method in the RMSE and MAE semesters with values of 1.998 and 1.5899, respectively, has an acceptable performance compared to the multivariate regression analysis in predicting compressive strength of geopolymer concrete. In addition, the results of sensitivity analysis showed that Na2Sio3 / NaOH and sample age had the most effect and polypropylene fibers had the least effect in predicting the compressive strength of geopolymer concrete.


Main Subjects

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