Effect of Additives and Protective Coating on the Indirect Tensile Strength and Oblique Shear of Concrete under the Sulfate Attack and Salt Crystallization Using Hybrid FMEA and Fuzzy TOPSIS Technique

Abstract

The fuzzy FMEA technique was used to identify failure risks in the operation of wastewater plants. The mentioned risks were found by employing experts in the water and sewage industry then a matrix of fuzzy RPN parameters was shaped, and the risks were ranked based on the fuzzy TOPSIS method. The results indicated that the risk of low durability of structural concrete (0.72) obtained the first rank of the cause leading to wastewater plant failure followed by the quality of inlet sewage (0.66) and appropriate repair and maintenance (0.63), which obtained second and third ranks, respectively. Because the quality of concrete structures exposed to wastewater was at first rank, it was decided on manufacturing resistant concrete in the laboratory. The concrete structures are obviously in contact with wastewater exposed to sulfate ions. These aggressive ions produce new compounds by reacting to hydration products causing a crack or splitting in the concrete due to expansion. Therefore, concrete protection solutions must be created in such environments. Additives and protective coatings are some of these solutions. The present study evaluated the effect of additives, including polymer latex and micro-silica, and protective coatings such as epoxy and crystallization on concrete durability under the simultaneous effect of sulfate attack and salt crystallization. For this purpose, concrete specimens were exposed to sodium sulfate solution and successive wetting-drying cycles. The decline in concrete strength resulting from destructive factors was then determined, by using indirect tensile strength and oblique shear strength tests. The results showed that a minimum reduction in indirect tensile strength occurs when using 10% latex and 5% micro-silica, while 20% latex and 10% micro-silica are used in the oblique shear test to achieve the minimum decline in this indirect tensile strength of concrete. Epoxy coating outperformed crystallization in case of increasing concrete durability.