Water resistance and a comprehensive evaluation model of magnesium oxychloride cement concrete based on Taguchi and entropy weight method

In this paper, phosphoric acid (PA) and fly ash (FA) were added to improve the water resistance of magnesium oxychloride cement concrete (MOCC). The effects of the single or compound addition of PA and FA on the compressive strength and internal deterioration based on Taguchi method, water resistance, phase composition, and microstructure were studied in detail by means of compression test, relative dynamic elasticity modulus test, X-ray diffraction (XRD) and scanning electron microscope (SEM). Furthermore, a comprehensive evaluation model of MOCC was established on the base of entropy weight method, and the critical value of its comprehensive water resistance coefficient was given. The results showed that the single or compound addition of PA and FA decreased the compressive strength of MOCC but led to an increase in the water resistance. The water resistance of MOCC with the combination of PA and FA was better than that with single-doped PA or FA, and the water-resistant effect of FA was far less than that of PA. It was also noted that the above conclusions were mutually validated by multiple methods. Besides, the comprehensive evaluation model could reduce the test error, improve the reliability of test analysis, and effectively evaluate the water resistance of MOCC. For MOCC, the critical value of comprehensive water resistance coefficient was 0.80. (C) 2020 Elsevier Ltd. All rights reserved.