DURABILITY OF BOND BETWEEN REPAIR MATERIAL AND SUBSTRATE CONCRETE

Abstract

Patch repairs have remained as the most successful methods for addressing concrete * deterioration. But in the past durability of concrete repairs is a concerning issue. The study undertaken here evaluates the durability issue of concrete repairs related with different environmental exposure conditions. Substrate specimens after casting and curing for twenty eight days under water were subjected to different environmental exposure conditions for fifty days. After fifty days specimens were taken out, their surfaces were prepared and they were repaired using different repair materials. Repaired specimens were again subjected to their respective environmental exposure conditions for sixty days. After sixty days of exposure they were taken out and tested. Twenty four slant shear specimen for slant shear bond strength evaluation of repaired specimen after exposure to various environmental conditions has been tested. Pull off testing for same environmental exposure conditions has also been carried out. The importance of surface preparation method has been shown by using sand blasting, acid etching and no treatment while preparing substrate surface. Bond strength obtained is used as a measure of success of repair and comparison with corresponding value of bond strength for control specimen has been used for measuring degradation of bond strength. Results show that surface preparation method is important as far as bond strength is concerned and environmental exposure conditions can degrade the bond strength considerably. Bond strength obtained by using micro-concrete as a repair material and acid etching as surface preparation method are comparable to the bond strength obtained by using polymer modified concrete as repair material and sand blasting as surface preparation method, this finding proves the fact that poor surface preparation cannot be compensated by using good and expensive repair material. Of all the exposure conditions acidic water has the most deteriorating effect followed by varying temperature conditions and marine-water.