Effect of elevated temperature on properties of neem seed husk ash concrete

Abstract

High temperature rise mostly caused by fire is currently becoming a threat that endangers concrete’s structural performance for buildings and the safety of dwellers. The behavior of concrete after fire subjection has been of much interest for structural materials design purposes. This study investigated the physical properties and the compressive strength of cement - neem seed husk ash blended concrete exposed to elevated temperatures. The neem seed husk ash was produced by calcining neem seed husks at 800 ℃ for 6 hours and then sieved through the 125 μm sieve. The cement – neem seed husk ash blended concrete was made by partially replacing cement with 3%, 5%, 7% and 10% of neem seed husk ash. The strength of concrete employed is M25. One hundred and fifty concrete cubes of 150 mm sizes were formed and appropriately cured by immersing in water for 7 and 28 days. The cured concrete cube samples were then exposed to and through targeted different levels of temperature; 25 ℃, 200 ℃, 400 ℃, 600 ℃ and 800 ℃, retained for 3 hours in an electric furnace. It was observed that an optimal replacement of cement by 5% of neem seed husk ash yields concrete with improved fire resistance. The experimental results indicate that the compressive strength of the blended concrete (with 5% of neem seed husk ash) exposed to temperatures up to 400 ℃ is 21.3% and 23.8% better than the normal concrete at 7 and 28 curing days respectively. Surface cracks and spalling are noticeable at 600 ℃ for all samples considered in this study. Keywords: Neem seed husk ash, Concrete, Elevated temperature, Spalling, Mass loss, Compressive strength.