| Abstract: |
The durability of high strength concrete (HSC) was experimentallyinvestigated. The evaluation was based on the performance of (HSC) underthree types of mechanical tests (compression, indirect tension and pull-out).The (BSC) specimens were exposed directly to five different types ofenvironmental- attack. These include, sulfate, chloride, seawater, air, andwater. The specimens were submerged in three solutions of sodium sulfate of(5%, 6%, 7%) concentration and sodium chloride of (2%, 3%, 4%)concentration. The specimens were tested after 28, 360, 540 and 720 days.The effect of silica fume (SF) addition ratio (0%, 5%, 10%, 15%) by weightof cement was considered.The results of this work indicated that the compressive strength of highstrength concrete specimen’s increases with increasing silica fume additionratio, also the tensile and bond strengths generally increase, with higher earlyage strength and higher early rate of strength gain with time up to about oneyear, 15% silica fume concrete shows the greatest improvement in strength.High strength concrete, incorporating silica fume, when exposed tosulphate and chloride solutions, exhibits the highest values, higher rates ofincrease and the lowest rates of decrease of compressive strength up to 18months, 10% silica fume addition ratio gives the best results especially athigher degrees of aggressiveness of the environment.X -ray diffraction (XRD) patterns of the hardened specimens wasplotted for all cured conditions, which explain the chemical compoundsfanned after hardening and the effect of SF content on these compounds.The carbonation depth in high strength concrete incorporating SF,demonstrated by Ph.Ph. test, was diminished. The impermeably of SFconcrete increased with the increase in silica fume content.
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