Modeling the Effects of Frost Damage on Concrete Structures

Abstract

Deteriorating concrete structures demand reliable methods for assessing and quantifying damage. In cold regions, concrete structures are susceptible to freeze and thaw cycles which cause frost damage. Frost damage has been observed to cause most severe type of deterioration in concrete structures as it significantly reduces the strength, stiffness and durability. Due to the climate conditions, concrete infrastructure in Canada is especially prone to frost damage. Since the 1930s, entrained air was found to greatly increase the concrete resistance against surface scaling by deicing salts. Air entrainment has since become an efficient measure against frost damage of concrete used in environments with freezing and thawing. Currently, however, Canadian standards for concrete structures do not provide explicit guidelines for the evaluation of frost damage. Understanding the effects of frost damage on concrete structures is essential for developing methods to effectively quantify and assess the impact of this deterioration mode on the structural capacity of concrete infrastructure. This study proposes a structural analysis method that accounts for the degradation of the load carrying capacity and stiffness of frost-damaged reinforced concrete flexural members. The method is developed through nonlinear finite element analyses of reinforced concrete beams in which frost damage is accounted for by modifying mechanical properties according to existing analytical constitutive models for frost-damaged concrete in compression and tension, and for bond steel-concrete interaction. The analysis procedure is validated with published experimental results of reinforced concrete beams subjected to frost damage. A parametric analysis of design variables and level of frost damage is also presented in order to establish the importance of each in the behavior of damaged reinforced concrete beams.