Concrete Strength and Bond Behaviour in Chemically Aggressive Environments

Abstract

The results of pullout and compression tests of concrete subjected to a simulated aggressive chemical environment is presented. About one hundred and tour pull out test specimens and one hundred and fourteen cubes were tested for ultimate local bond strength after curing for one hundred and eight days in different aggressive media. Two of the simulated environments were acid based while the third was caustic. The cubes cured in the acid based environment namely, Sulphuric and Hydrochloric acids showed a remarkable strength loss for the grade 30 and 40 concrete used. The caustic medium, Sodium Chloride solution did not show any convincing strength loss. A natural occurring material, Rubber Latex ( Poly 1- 4 Isoprene ) for coating small diameter bars in “light” structures was examined. With an appreciable Bond Ratio range of 0.97 to 1.05 the material is found acceptable as a coating medium for concrete reinforcement bars. The simulated aggressive media had volume fractions restricted to 2 percent for the Pullout test and 3 percent for the Compressive Strength Test. It was observed that for Local Bond requirements to be controlled, higher grade of concrete may be necessary depending on the nature of the aggressive environment and the bar diameter. It was also observed that the limiting volume fraction for maximum ultimate bond stress is a function of the bar size and the concrete grade. Thus for grade 30 concrete, the limiting value is between the range of (0.57 to 0.74) percent for sulphuric acid simulated medium and (0.95 to 1.0) percent for hydrochloric acid simulated medium. That of grade 40 concrete in a sulphuric and hydrochloric acids simulated media are within the range of (0.95 to 1.45) percent and (1.10 to 1.20) percent respectively.