Performance of concrete containing recycled springs in post-fire conditions

The main objective of this study was to assess the performance of concrete containing recycled springs with various volume fractions of 0·2, 0·4 and 0·6% at temperatures of 25, 100, 250, 500, 700 and 900°C. In addition, a comparison between concrete mixes containing steel and polypropylene fibres was performed using tensile and compressive strength tests to attain an optimum mix design. The results showed that the compressive and tensile strengths of concrete specimens were improved by adding the percentages of 0·2, 0·4 and 0·6% springs. However, these strengths decreased by increasing the volume fraction of springs. Furthermore, the optimal compressive strength of concrete containing springs was 2–3 times greater than that of concrete containing steel and polypropylene fibres at various temperatures, but there was no significant difference between the tensile strengths of concrete containing springs and steel fibres. In addition, the use of fibre in concrete caused a decrease in the width of the cracks created after the splitting tensile test, by up to three times.