Compressive behavior of fiber-reinforced concrete strengthened with CFRP strips after exposure to temperature environments

Reinforced concrete constructions are extremely vulnerable to fire damage over their lifespan. Despite its non-flammability, concrete is nonetheless affected by fire exposure, which impacts its stress-strain characteristics and durability. Therefore, developing strengthening methods is an economical option compared to the costs of demolishing and rebuilding constructions. This article aims to experimentally and numerically examine the strengthening of fiber-reinforced concrete cylinders by using carbon fiber-reinforced polymer (CFRP) strips after exposure to 600 degrees C. Four different concrete mixtures have been investigated. A total of 48 cylinders were subjected to axial compression testing. The testing program primarily focused on three variables: (i) exposure temperature (600 degrees C); (ii) the effect of using various types of fibers (steel fiber, polypropylene, and hybrid fibers); and (iii) CFRP strengthening. Finite element (FE) models were created using the ABAQUS program to conduct numerical analysis of concrete cylinders in exposure to heating scenarios and strengthen them with CFRP strips. The results show that when subjected to a temperature of 600 degrees C, the compressive strength decreased significantly, ranging from 23.7 to 53.3%. The presence of fibers significantly impacted compressive strength, regardless of the fiber type, leading to an enhanced ratio of up to 34.7% in comparison to the control cylinders (i.e., unheated and unstrengthened cylinders). The suggested strengthening procedures using CFRP strips effectively repaired the heat-damaged cylinders, surpassing the initial compressive strength of unheated cylinders. The FE prediction shows satisfactory, consistent results in comparison to experimental data.