Effects of slag and cooling method on the progressive deterioration of concrete after exposure to elevated temperatures as in a fire event

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0905 Civil Engineering | Journal article

Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/93237

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Title: Effects of slag and cooling method on the progressive deterioration of concrete after exposure to elevated temperatures as in a fire event
Author(s): Mendes, Alessandra; Sanjayan, Jay G.; Collins, Frank
Abstract: In the present work OPC and OPC/slag concretes were exposed to elevated temperatures, 400 and 800°C. The critical temperature of 400°C has been reported for OPC paste. Above 400°C, the paste hydrate Ca(OH)2 dehydrates into CaO causing the OPC paste to shrink and crack. After cooling and in the presence of air moisture, CaO rehydrates into Ca(OH)2, resulting in disintegration due to re-expansion of OPC paste. Therefore, the present work assessed whether this also applies to OPC concretes. Two cooling methods were used: furnace and water cooling. Following the heat treatment/cooling method, compressive tests and Infrared (IR) spectroscopic studies were conducted. Results showed that after 400°C, water cooling caused all concrete, regardless of the type of blended cement binder, a further 20% loss in the residual strength. After 800°C, water cooling caused OPC concrete a further 14% loss while slag blends presented around 5% loss. IR indicated that the further loss observed in the OPC concrete is due to the accelerated CaO rehydration into Ca(OH)2. Afterward, the non-wetted furnace cooled specimens were exposed to air moisture for one week, resulting in further strength loss of 13%. IR results suggested that slow rehydration of CaO occur with exposure to air moisture. In conclusion, water cooling caused more damage in OPC concrete, while the concrete that has not been wetted undergoes progressive deterioration. This indicates a need to monitor the non-wetted concrete after a fire event has occurred for potential further deterioration.
Publication type: Journal article
Research centre: Swinburne University of Technology. Faculty of Engineering and Industrial Sciences
Source: Materials and Structures, Vol. 44, no. 3 (Apr 2011), pp. 709-718
Publication year: 2011
FOR Code(s): 0905 Civil Engineering
Keyword(s): Cooling methods; Elevated temperatures; OPC; Ordinary Portland cement; Progressive deterioration; Slag concrete
Publisher: Springer
ISSN: 1359-5997
Publisher URL: http://dx.doi.org/10.1617/s11527-010-9660-2
Peer reviewed