Analysis of Engineered Cementitious Composite Bond Strength for Grouting Reinforcement to Concrete Members

Extending the operational life or improving capacity of concrete structures not only makes sense but is an environmentally sound practise as well. The strengthening or rehabilitation of deteriorated concrete sections can be achieved by adding additional reinforcement. This paper examines the role the binder material plays in the near surface mounting of fibre reinforced polymer bars. Recently, FRP products are being retrofitted to RC members due to their high tensile strength and resistance to harsh environmental conditions. In order to gain the full benefit of this material, the grout which binds the bar to the existing concrete must be able to handle the stresses involved. This raised the following questions for the researcher: - What grout mixture should be used; - Are some alternatives susceptible to a colder curing environment? Multiple sets of samples were prepared with a specific ECC mixture and a standard cement-sand grout used to bond FRP bars to grooved concrete blocks. One set of each binder material was cured under normal conditions while a second set of ECC specimens was cured at a constant 2.8C. Pull-out tests were conducted in order to determine the tensile load required to cause bond failure. The type of failure was also noted for further analysis. Analysis of gathered data reveals the ECC specimens achieved a much higher bond strength that the standard cement-sand specimens, i.e. approximately 9 times greater. ECC samples cured at a significantly lower temperature reached 92.6% of those cured in normal conditions. The ECC binder was not as affected by curing temperature as was expected. Cracking of some concrete members may have contributed to specimens failing prematurely. Recommendations for additional future research include: - increased sample size and concrete strength for improved data gathering; - curing of specimens at temperatures just slightly below and above 0C; - Extended exposure to harsh conditions e.g. a high salt environment