Investigation on the mechanism of explosive spalling of high performance concrete at elevated temperatures

Experiments were performed on several types of high performance concrete, including high strength concrete and self compacting concrete with different dosages of polypropylene fibers. Differential thermal and thermo gravimetric analyses were used to capture the physcial and chemical developments with temperature. After a special heating process, scannning electron microscopy and mercury instruction porosimetry were applied to investigate the microstructure. Gas permeability test was carried out in order to determine the effect of micro-structural changes on the permeability. Based on the results, the cause of micro structure development with elevated temperature was analyzed. The melting of polypropylene fibers was captured and its influence on the micro structure was also discussed. The relationship between micro structure and gas permeability and the factors affecting gas permeability were also investigated. The conclusions are helpful for understanding the spalling of high performance concrete at elevated temperatures, and would promote further usage of high performance concrete.