Performance of cementitious composites subjected to combined fire and blast loading

Abstract

This thesis is focused on the study of influence of the material properties of different types of concrete on the resistance to fire and blast loading. The interaction of fire and blast loading has not yet been quantified so far in any way. The aim of this thesis is to quantify this interaction based on an original experimental program. Mainly focusing on the properties of the materials studied, the original experimental program is divided into three main parts. In the first part, the material properties of five materials are determined as a function of the elevated temperature. The determined properties are: bulk density, porosity, thermal conductivity, specific heat capacity, permeability, and compressive strength. In the second part of the experimental program, specimens of three materials are subjected to fire and subsequent blast loading. The specimens are subjected to an elevated temperature of 400 °C, followed by near blast using 40 g of Semtex at a distance of 30 mm from the specimen. The result of these experiments is the level of damage to the specimens and the velocity of the flying debris (soffit velocity) measured using Photonic Doppler velocimetry. In the last part of the experimental program, a numerical simulation of the experiments is performed. the numerical analysis is performed for only the reference material. Within this part, both the change of the mechanical properties by elevated temperature and the blast is simulated. The result is the velocity of the flying debris (soffit velocity) and a comparison of the shock wave propagation velocity through the specimen. As a result of the undertaken experimental program, a trend of behavior is determined, where the main parameter influencing the behavior of concrete elements subjected to fire and subsequent blast loading seems to be the tensile strength. Tensile strength decreases quickly with increasing temperature and is also a key property for the element's resistance to blast.