LONG -TERM BEHAVIOR OF SILICA FUME CONCRETE EXPOSED TO DIFFERENT AGGRESSIVE MEDIA

Abstract

The durability of high strength concrete (HSC) was experimentally investigated in terms of compressive, tensile and bond strengths. The effect of curing media, (air and tap water) and the effect of emersion in sea- water were taken into consideration. The silica fume (SF) concrete specimens were exposed directly to two types of environmental attack (sodium sulphate and sodium chloride). The specimens were submerged in two different solutions of sodium sulphate having concentrations of 5% and 7% and sodium chloride of 2% and 4% concentrations. The specimens were tested after 28, 360, 540 and 720 days. The SF addition was 10% by weight of cement. Test results showed that the compressive, tensile and bond strengths generally increase, with higher early age strength and higher early rate of strength gain, with time up to about two years. High strength concrete, incorporating silica fume, when exposed to sulphate and chloride solutions, exhibits highest values, higher rates of increase and the lowest rates of decrease of compressive strength up to 24 months. X-ray diffraction (XRD) patterns of the hardened specimens were plotted for all cured conditions, which explain the chemical compounds formed aRer hardening.