The influence of sand nature on the residual physical and mechanical properties of concrete after exposure to elevated temperature

Abstract

A considerable number of investigations have been conducted on the physical and mechanical properties of concrete made with crushed calcareous sand at room temperature. However, no attention has been directed at studying the performance of concrete made with crushed calcareous sand at elevated temperature. This study investigates the effects of elevated temperatures on the residual mechanical and physical properties of concretes made of two types of sand (siliceous and calcareous). For each sand type, three water/cement ratios (w/c = .6, .42 and .27) were tested. Specimens were heated under six different temperatures: 20 °C (ambient temperature), 150, 250, 400, 600 and 900 °C. After cooling down to ambient temperature, the compressive strength, ultrasonic pulse velocity, mass loss, water porosity, density and specimens’ volume were determined. Also surface crack observations were conducted with Microscope. Results obtained show that there are no significant differences in the physical properties of concrete made with calcareous sand when compared to concrete made with siliceous sand. The evolution of the residual compressive strength with temperature depends on the mineralogical nature of sand and the water/cement ratio.

Keywords:

• Sand
• concrete
• high temperature
• physical properties
• compressive strength

Abbreviations:

• CaCO₃: calcium carbonate
• CaO: free lime
• CO₂: carbon dioxide
• Ca(OH)₂: portlandite
• NSC: normal strength concrete
• HSC: high strength concrete
• HPC: high performance concrete
• w/c: water/cement
• UPV: ultrasonic pulse velocity
• SC-C: concrete contained calcareous sand
• SS-C: concrete contained siliceous sand
• M_initial: initial mass (g)
• M_heated: heated mass (g)
• M_sat: saturated mass of a sample measured in the air (g)
• M_sat+imm: saturated mass of a sample measured in water (g)
• P: porosity (%)
• D: density
• V_v: variation of specimen’s volume
• V₂₀: volume of specimen before heating (cm³)
• V_t: volume of specimen after heating (cm³)
• ν: pulse velocity (km/s)
• L: length of the sample (m)
• s: time (s)