Investigating the Cause of Blistering in SBS Polymer Modified-Bitumen Roofing Membranes

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TypeTechnical Report
Series titleInternal Report, Institute for Research in Construction, National Research Council Canada; Volume 759
Physical description39 p.
SubjectRoofs; Roofs
AbstractThe cause of blistering in modified bituminous roofing membrane systems was investigated. Membrane samples were removed from several existing modified bituminous roofs containing blisters. Their mechanical behaviour was characterized by tensile tests. Gas content within the blisters were collected in canisters in the field and their chemical composition was determined quantitatively by Gas Chromatography /Mass Spectroscopy (GC/MS). Mechanical testing indicates that blister formation does not seem to depend onthe strength of the modified bituminous membrane. Also, the existence of blisters did not reduce the strength of the membrane, at least not where the blister remained intact. GC/MS revealed that the gas within the blisters was composed mainly of air and water vapour, with a negligible amount of volatile organic compounds. The relative humidity of the blister gas ranged from 30 to 75%. These findings indicated that the mechanism of blister formation and growth in modified bituminous roofs is possibly the same as that inbuilt-up roofing where water vapour promotes blister growth by exerting cyclic pumping action to the blister following the diurnal changes in temperature.
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
NRC number8199
NPARC number20331503
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Record identifier770bed80-ec9d-46e1-8823-78a001cde2fb
Record created2012-07-18
Record modified2016-10-03
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