Concrete cracking in structures is a ubiquitous problem which can lead to the deterioration of the structure. Other than affecting the strength aspect of a structure, cracking impacts the serviceability criteria as well. Although cracking phenomenon in any structure is highly inevitable, it has to be minimized in order to maintain a structure’s life effectively. Cracking in reinforced concrete structures is related to the bond strength developed between the bar and the concrete. It also depends on an ability of the bar to resist the stresses due to shrinkage to minimize the crack. Another important aspect is the resistance offered by the reinforcement to minimize the residual crack width after withdrawal of high loads beyond or near the yielding capacity. All these parameters were considered and have been studied as a part of this dissertation through experimental testing.
The variables used in the tests are the alternative coated reinforcements like textured epoxy, hot dipped galvanized, and continuously galvanized reinforcements. Variables also included uncoated (black) and conventional epoxy (smooth epoxy) reinforcements which have been used in structure for many decades. Considering all the tests conducted, an overview analysis was done to determine the best performing bar coating for crack control and rebar-concrete bond. The results show that textured epoxy bars were the best performer in 47% of tests. On the other hand, smooth epoxy bars were the worst performer in 47% of tests. Uncoated, hot dipped galvanized, and continuously galvanized bars were typically in-between textured and smooth epoxy bars in their performance.
This dissertation also analytically evaluated the bond mechanics associated with the variable bar coatings considered in the experimental program. Two different models of bar force variation at and around a crack location were considered to calculate the length over which forces transfer between the bar and concrete. The calculated lengths were compared to data from an associated peer study. It is inferred from the results that a small portion of a bar is de-bonded adjacent to the cracks and the forces transfer gradually at locations beyond the debonding. This inference applies to all the bar coatings in the data except the continuously galvanized reinforcement. Conclusions for continuously galvanized reinforcement could not be made because of limited and randomness in the data
