Effects of elevated temperatures on properties of self-compacting-concrete containing fly ash and spent foundry sand

摘要

In this paper an attempt has been made to study the use of spent foundry sand and fly ash on the properties of Self-Compacting-Concrete (SCC) such as compressive strength, splitting tensile strength, modulus of elasticity, rapid chloride permeability, porosity and mass loss when exposed to elevated temperatures. The influence of fly ash as partial replacement of cement, and spent foundry sand as partial replacement of sand on the properties of SCC is investigated. In this research, mixes were prepared with three percentages of fly ash ranging from 30% to 50% and one controlled mixture without fly ash was also prepared for comparison. Fine aggregate was replaced with 10% of spent foundry sand. The specimens of each concrete mixture were heated up to different temperatures (27 ℃, 100 ℃, 200 ℃, and 300 ℃). In order to ensure a uniform temperature throughout the specimens, the temperature was held constant at the maximum value for 1 h before cooling. Using Ordinary Portland cement, an increase of about 24-25% in compressive strength, 18-22% in splitting tensile strength was observed at 28 days when fly ash content was decreased from 50% to 30%. Also test results clearly show that there is little improvement in compressive strength within the temperature range of 200-300 ℃ as compared to 27-200 ℃. But the rate of splitting tensile strength and modulus of elasticity loss was higher than that of the compressive strength loss at elevated temperatures and with the increase in percentage of fly ash. In this paper X-ray diffraction and Scanning Electron Microscopic (SEM) observations were also made to explain the observed residual compressive strength increase between 200 and 300 ℃.