Crack Bridging Tests

Crack Bridging Test Laboratory

This test method includes a laboratory procedure to determine the ability of a waterproofing membrane to bridge a crack in the substrate.

The concept of crack bridging is generally applied when there are mechanisms behind the crack tip that inhibit crack growth. Even after the crack tip is enlarged, the crack surfaces can bridge the cracks, and the fibers, grains, or boils (in polymers) can remain attached to crack the crack faces. Crack Bridging can provide extrinsic hardening to the material.

The experience gained through the use of an appropriate performance test and use for accelerated testing and assessment of crack bridging capability of roofing membranes exposed to real climatic conditions has been described. The tester consists of a reinforced concrete slab measuring 100 cm x 50 cm x 5 cm on free-standing horizontal supports. A transverse crack of medium length and controlled width is formed. The membrane under test may be applied before or after inducing the crack.
The crack opening and closing is due to the differential thermal movements between the concrete slab and the two black aluminum profiles in the “solar panels olan which are longitudinally connected on both sides of the slab. On cracked sunny days, 0,7 mm opens during daylight hours and closes at night. The typical temperature changes recorded during the calibration period and the resulting crack widths are discussed. Also included are the results of comparative tests on different roofing materials compared to the device. From the experience gained so far with the device, it is concluded that the crack bridging capabilities of different roofing membranes can be compared and evaluated after exposure for only a few months for the specified crack width movement.

A surface coating for concrete may be subjected to a wide variety of environments, movements and stresses depending on the application in which the structure is used. Therefore, coatings have different requirements to satisfactorily protect concrete structures in different service environments. As water penetrates, it usually leads to degradation of the substrate (concrete) and / or water permeability is an important factor to consider in the evaluation of the performance of a coating when steel is present in the electrochemical reaction (reinforced concrete). Another important feature that should be evaluated if the ability of crack bridging coatings is a coating, a protection concrete structure is definitely broken.

Values ​​stated in SI units or inch-pound units should be considered separately as standard. The values ​​specified in each system may not be exactly equivalent; therefore, each system should be used independently of the other. Combining values ​​from two systems can cause incompatibility with the standard.

This test method is used to demonstrate the ability of a waterproofing membrane to maintain its integrity while bridging a pre-existing crack in the substrate at low temperatures at low temperatures where the membrane's flexibility is least.

You can work with our laboratory EUROLAB for crack bridging capability tests.