Strengthening and shape modification of fire-damaged concrete with expansive cement concrete and CFRP wrap

Abstract

This paper reports the results of an experimental study that involved the investigation of the axial capacity of fire-damaged specimens repaired by expansive cement concrete and CFRP wrap. Specimens were subjected to axial compressive loading and their resulting stress-strain curves were recorded. Since the fiat sides of the square samples remained unconfined, the cross-sections of the tested specimens largely remained unconfined. The FRP jacket was efiective only along the two diagonals of the cross-section. Confinement is generally more efiective in specimens with circular cross-sections than in those with square ones. The change in cross-section for some of the specimens from square to circular ones was implemented. To modify the shape, expansive cement concrete was utilized to fill the gap between the circular and square cross-sections. The test results indicated that heating up to 500C caused a severe decline in compressive strength and the elastic modulus of concrete. Two layers of CFRP wrap around the concrete not only compensated the drop in compressive strength, but also increased the strength beyond that of unheated specimen. However, the efiect of wrapping alone on the stifiness and the elastic modulus is negligible. The heated square specimens that were first subjected to shape modification and, then, wrapped by CFRP sheet experienced an increase in the strength and the elastic modulus. Therefore, the stifiness and the compression strength of fire-damaged square concrete specimens could be compensated fully by the use of shape modification and CFRP wrapping of the cross-section.