Experimental investigation on the effect of silica fume and zeolite on mechanical and durability properties of concrete at high temperatures

Fire assessment of structures is an important area of concern. When the knowledge of concrete structures behavior at high temperatures is insufficient, there will be irreparable damage and financial losses. In this study, the mechanical and durability properties of concrete, aiming to overcome the adverse effects of high temperature by substituting a portion of cement with pozzolans is presented. The mechanical properties at the hot condition and the durability characteristics were tested when they reach the ambient temperature. The mechanical properties including compressive, tensile and shear strength, and the durability were evaluated based on the surface water absorption, water penetration depth, electrical resistance, and weight loss tests. Tests were conducted at different temperatures ranging from 28 to 800 degrees C. The results show that by increasing the temperature, the mechanical properties of the concrete decreased, with further increase in temperature they recovered and then started to decrease. Application of silica fume improved the compressive and tensile strength in a range of 1.35-26.74%, and 0.37-234.58% at the tested temperatures. However, pozzolans have not a significant impact on the shear strength. The study of the durability of concrete has shown that the heat reduced the durability of concrete while the addition of zeolite and silica fume compensated this reduction. In tests based on capillary properties and in the electrical resistivity test, samples containing zeolite had better durability properties. Meanwhile, in samples containing zeolite, those with a higher content of zeolite were better in terms of durability properties.