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ASTM Selected Technical Papers
Roofing Research and Standards Development
RA Critchell
RA Critchell
Eastman Kodak Co.
Rochester, NY 14650
symposium chairman and editor
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ASTM International
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In cold climates, roofing membranes are subjected to at least two forms of critical loading:

1. In a fully adhered system, significant forces and deformations can be induced in the membrane by thermal deformation and movement at the joint in the substrate.

2. In severe climates, ice can form and bond to the top of the membrane. When the ice cracks, significant forces can be induced in the membrane.

The tension test is currently used as the standard test for the strength and elongation properties of most roof membrane materials. For fully adhered systems, such as modified bituminous membranes, the tension test is of only limited use since it does not simulate the actual in-place performance of the membrane or the constituent materials, especially for the load cases noted.

An alternative to the tension test is considered. A joint-bridging test procedure is developed that more closely models the loading to which a fully adhered roof system could be subjected.

The test specimen consists of a section of the roof system or membrane material that is fully adhered to a substrate. The substrate is separated into two sections. Each substrate section is gripped in the test machine jaw and these are separated at a constant rate. The force required to separate the substrate sections and the width of the joint opening between substrate sections are continuously measured.

It is evident that the joint-bridging test provides a better basis for understanding the behavior of fully adhered roof systems than does the tension test. The joint-bridging test simulates a realistic situation and it permits the study of reinforcement considerations.

H. E.
, “
PVC Roof Membranes—Factors Affecting Tensile Tests
Second International Symposium on Roofing Technology
Gaithersburg, MD
, pp. 161-163.
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