It is well established that alkali aggregate reaction (AAR) causes extensive cracking in concrete and reduces the tensile strength, modulus of elasticity and to a certain extent, the compressive strength. This would undoubtedly bring the safety of the structure into question and may require extensive repairs to be carried out.

This study is carried out to investigate the benefit of using carbon fibre reinforced polymers (CFRP) as a strengthening system to confine square and circular reinforced concrete columns damaged by AAR. The columns were confined with one or two layers of high and normal modulus CFRP at various ages of concrete. The repaired concrete columns were subjected to 38°C and 100% humidity for a minimum period of 6 months, and then tested in unaxial compression. Contaminated specimens without CFRP confinement were tested to evaluate the residual capacity of the concrete in comparison with normal concrete columns.

The results have shown that the high modulus CFRP is not effective in controlling the AAR expansion in the concrete due to its low tensile strain capacity. Normal modulus CFRP has proven to be more effective as it has a higher tensile strain capacity. However, the effectiveness of normal modulus CFRP is dependent on the time of application relative to the expansion history of the contaminated concrete. If the CFRP application is carried out at an early stage of concrete expansion, the CFRP provides active confinement. The confinement becomes passive if the application is carried out at late stages of expansion history.