CFRP confinement of circular concrete columns affected by alkali-aggregate reaction

Abstract

Alkali-aggregate reaction (AAR) is known to cause expansion and cracking in concrete, which adversely affect the mechanical properties of concrete, leading to a decrease in the service life of structures. Wrapping damaged elements with epoxy-bonded carbon fiber reinforced polymer (CFRP) is a method of rehabilitation. This paper investigates the level of expansion in concrete caused by AAR and its effects on the mechanical properties of concrete during a period of one year. The decreases in compressive strength, flexural strength, splitting tensile strength and modulus of elasticity reached 74%, 81%, 76% and 93% respectively. Twenty six reinforced and plain columns of dimensions 200mm in diameter and 500mm in height were fabricated from normal and reactive concretes. The latter contained fused silica at 7.5% of total aggregate as reactive component. The columns developed high expansion levels due to AAR in the storage period between 120 and 180days, which caused severe cracking in the affected columns. One, two and three layers of CFRP were used to confine the affected and unaffected columns. Results indicated that CFRP wrapping increased the strength and strain capacities of confined columns compared to unconfined columns. Larger number of applied CFRP layers also increased the capacity of the affected columns.