CONSTITUTIVE MODEL OF HIGTH STRENGTH CONCRETE BEHAVIOUR AT HIGTH TEMPERATURES

Abstract

When concrete is subjected to high temperatures, it experiences a series of chemical reactions that cause transformations in its microstructure and moisture content, which produce appreciable changes in the physical-mechanical properties of the material. In this paper a proposal of constitutive and state equations are presented, that have allowed to physically model the effect of the chemical transformations on high strength concrete and to describe the transitory evolution of the physical-mechanical properties with the increase of temperatures. In addition, a sensitivity analysis of the proposed model has been carried out which evaluates the responsiveness to the variation of different input parameters such as heating speed, intrinsic permeability, saturation and hydration initial degree and polypropylene fiber content. The results of the sensitivity analysis have shown that the assumptions and proposed equations allow to model the phenomenon with sufficient precision for its application for practical purposes. Keywords: pore pressure, concrete, physical-mechanical properties, fire, constitutive model