NCJ Number
132317
Journal
Journal of the Forensic Society Volume: 31 Issue: 1 Dated: (January/March 1991) Pages: 67-75
Date Published
1991
Length
9 pages
Annotation
The effect of various fire conditions on the chipping or degradation of a concrete surface (spalling) is explored through a literature review and in controlled fire experiments.
Abstract
In the literature review, the various causes of concrete spalling were examined as well as the composition of concrete relevant to spalling. Mechanical movement, electrolyte decay of interior metal reinforcements, penetration by mineral acid gases, ozone, organic acids, sulfate ions and acids in water, chlorides, all can cause concrete surface degradation. However, fire related spalling can result from surface pitting, corner break offs, and explosive spalling. The hypothesis that only flammable liquids cause a darkened ring at the perimeter of explosive spalls was tested in experimental tests. When up to two liters of gasoline were poured onto a slab and ignited, no spalling resulted. Conversely, small fires of normal construction materials resulted in extensive spalling accompanied by darkened areas at the perimeter of the spall. These experiments as well as the literature review, cast doubt on the theories that gasoline or volatile petroleum liquid fluids used in arson fires cause explosive spalling on concrete slabs or that the presence of a dark ring at the perimeter of the spall indicates pouring of a liquid accelerant. 2 tables, 2 figures, and 40 references (Author abstract modified)