Retrofitting of damaged reinforced concrete pipe with CAC-GGBFS blended strain hardening cementitious composite (SHCC)

Reinforced Concrete Pipes (RCP) has been widely used for long-distance sewerage pipeline globally. However, concrete pipes are susceptible to microbially-induced acid corrosion (MIC) which leads to premature failure far before reaching their asset life. The aim of this study is to investigate the effectiveness and efficiency of using CAC (Calcium Aluminate Cement) - GGBFS (Ground Granulated Blast Furnace Slag) blended SHCC (Strain hardening cementitious composite) to retrofit damaged RCP. Prior to the retrofit, RCP was pre-loaded to 70%, 80%, 90% of its ultimate strength to create cracks. Retrofitted pipes were tested under three-edge bearing (TEB) load for assessment. Load-deflection relationship, load-strain behaviour along with pipe ductility and stiffness were analysed and discussed. Experimental results show that the ultimate load-carrying capacity of the retrofitted RCP increased up to 50.6% compared to original RCP. The retrofitted pipe acted monolithically with the lining material without debonding observed before failure. Moreover, a prediction formula was proposed to calculate the load-bearing capacity of retrofitted RCP in addition to experimental work. The theoretical model considers the impact of the pre-loading level on the original RCP and was verified with the experimental results. CAC-GGBFS blended SHCC is proven to be an effective repair solution to damaged concrete sewerage pipelines.