Thermal cycling of wheat straw ash concrete

This study investigated the effect of wheat straw ash (WSA) on the performance of concrete in response to thermal cycling, which was evaluated by measuring the compressive strength and electrical resistivity and by visual inspection of cracks in the concrete specimens. Three levels of WSA replacement—5, 10 and 15% by weight of sand—were utilised. The other experimental parameters investigated in the study were: aggregate type (volcanic tuff and crushed basalt), water-to-cement ratio (w/c; 0·5 and 0·7) and air entrainment (non-air-entrained and air-entrained). After an initial moist curing period of 90 days, the concrete specimens were subjected to thermal cycling over the range 30–150°C for a period of 24 h using an electric furnace. The results of the study showed that thermal cycling of WSA concrete induced many cracks that were dispersed over the surface of the specimens. The WSA concrete was found to be more resistant to the effects of thermal cycling in comparison with plain concrete and furthermore, the performance of WSA concrete in response to thermal cycling improved with increasing WSA content. WSA concrete containing tuff aggregate showed more resistance to thermal cycling than that containing basalt aggregate. In response to thermal cycling the WSA concrete at a w/c ratio of 0·5 was observed to show better performance in comparison with WSA concrete at a w/c ratio of 0·7. The air-entrained WSA concrete showed a greater improvement in response to thermal cycling in comparison with non-air-entrained WSA concrete.