Effect of aggregate type on strength and deformation properties of high-strength concrete during heating

Introduction. High-strength concrete is widely used in contemporary construction. Expanded introduction of high-strength concrete necessitates the need for studying its behavior at high temperatures (in case of fire) in order to ensure the required fire resistance of load-bearing reinforced concrete structures made of high-strength concrete in terms of fire safety of buildings and structures. Aim. To determine the effect of aggregate types on strength and deformation characteristics of high-strength B100 concrete when heated to temperatures from 100 °C to 800 °C with a step of 100 °C. Materials and methods. Laboratory tests of prism strength and elastic modulus of basalt and granite high-strength concrete were carried out on prism samples in a heated state according to standard methods using special heating equipment combined with laboratory pressure equipment. Results. The authors determined structure behavior factors of basalt and granite high-strength concrete during heating, specifying the decrease in compressive strength and elastic modulus. Deformation diagrams during axial compression of high-strength granite and basalt concretes under heating were drawn. Conclusions. The dynamics of reduction in strength and deformation properties is similar for granite and basalt high-strength concrete under heating and is specific for silicate aggregate concretes. The elastic moduli of basalt high-strength concrete are higher than those of granite high-strength concrete, both at 20 °C and when heated, thereby determining the dependence of high-strength concrete deformation properties on the types of aggregates. Deformation diagrams during the axial compression of high-strength granite and basalt concretes showed specific character: unilinear – when heated to temperatures of about 300–400 °C, bilinear – at higher heating temperatures, therefore differing from traditional ideas and theoretical recommendations.