Journal of Advanced Concrete Technology
Online ISSN : 1347-3913
ISSN-L : 1346-8014
Scientific paper
Microscopic Change in Hardened Cement Paste due to High-Speed Impact
Yuya SakaiIvwananji SikombeKeiko WatanabeHiroyuki Inoue
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2019 Volume 17 Issue 9 Pages 518-525

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Abstract

Impact load was applied to hardened cement paste (HCP) specimens using a gas gun to investigate microscopic changes in the specimens and develop a better response model of concrete subjected to impact load. Plasma emission was observed at the moment of impact at 420 metres per second and the colour of the portion near the impact point turned brighter. This brighter portion was analysed, and it was observed that the pore structure was coarser compared to the other portion. However, the results of thermogravimetry and X-ray diffraction analysis were similar. A possible reason is that the generated heat was instantaneous and the rate of the temperature increase in the HCP decreased due to evaporation of water in the HCP. These results indicate that during impact at a few hundred metres per second, porosity increase due to heat effect is more dominant than porosity decrease due to mechanical compaction.

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© 2019 by Japan Concrete Institute
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