The influence of water absorption and porosity on the deterioration of cement paste and concrete exposed to elevated temperatures, as in a fire event

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Sanjayan, Jay G. | 0905 Civil Engineering

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Title: The influence of water absorption and porosity on the deterioration of cement paste and concrete exposed to elevated temperatures, as in a fire event
Author(s): Mendes, Alessandra; Sanjayan, Jay G.; Gates, Will P.; Collins, Frank
Abstract: This study investigates why CaO rehydration causes total strength loss of OPC paste compared to only 65% loss of OPC concrete after 800 °C exposure. Subsequent water sorptivity tests revealed paste reacted instantaneously with water, completely disintegrating within minutes. This was attributed to an accelerated rehydration of CaO into CaOH 2. This was not observed in concrete. Sorptivity tests using acetone eliminated the disintegration due to CaO reaction with water. Porosity tests indicated a higher porosity and coarser capillary pore size distribution (PSD) in paste compared to paste in concrete. This has an influence on the rate of water absorption. The rate of water absorption determines the CaO rehydration rate and ultimately the growth rate of CaOH 2 crystals and type of CaOH 2 crystals formed. Different types of CaOH 2 crystals cause different levels of deterioration, not always leading to total disintegration. Therefore, the rate of water absorption is the determining factor controlling the extent of deterioration caused by CaO rehydration.
Publication type: Journal article
Research centre: Swinburne University of Technology. Faculty of Engineering and Industrial Sciences
Source: Cement and Concrete Composites, Vol. 34, no. 9 (Oct 2012), pp. 1067-1074
Publication year: 2012
FOR Code(s): 0905 Civil Engineering; 1202 Building
Keyword(s): Cement paste; Concrete; Elevated temperatures; Porosity; Strength loss; Water absorption
Publisher: Elsevier
ISSN: 0958-9465
Publisher URL: http://dx.doi.org/10.1016/j.cemconcomp.2012.06.007
Research Projects: Development of an alkali activated slag based construction material for high fire risk infrastructures, Australian Research Council grant number DP0558463
Peer reviewed