The Spalling of Normal Weight and Lightweight Concrete Exposed to Fire


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Title: The Spalling of Normal Weight and Lightweight Concrete Exposed to Fire

Author(s): W.J. Copier

Publication: Special Publication

Volume: 80


Appears on pages(s): 219-236

Keywords: beams (supports); climate; concretes; fire resistance; fires; fire tests; heat transfer; hi h temperature; lightweight concretes; moisture content; plates structural members); spalling.

Date: 7/1/1983

Spalling of Concrete exposed to fire is understood to be the explosive detachment of large or small pieces of concrete from the concrete surface subjected to heating. It was known from literature that spalling is very much related to the moisture content of concrete. In addition to several tests done in an earlier stage, 25 fire tests were carried out on both beams and plate like elements to investigate the influence of the moisture content. In these tests other parameters than the moisture content were incorporated like gravel as coarse aggregate and several kinds of light weight coarse aggregate as well; the compressive stress; the compressive strength; the thickness; reinforcement and one or two sided heating. In addition it was investigated both by tests and caculations which moisture content of concrete could be expected in buildings in course of time. It can be concluded that a high moisture content can give rise to severe spalling only if in addition, one or more other unfavorable working factors to be present at the same time. When the moisture content is low (7% v/v) which content can be expected in centrally heated buildings, about 5 years after completion, the risk of spalling diminishes. Explosive dislodging of many small pieces occuring continously than does not appear at all while the risk of explosive dislodging with a few large pieces is lower but still exsists.