Adhesion / Pull Off Tester

Evaluate the bond strength (adhesion) of a coating (e.g. screed, resin or coating) from a rigid substrate such as a concrete or metal floor.

Testing can be in accordance with the British and European standard BS EN 13892-8:2002, BS 8204-6:2008+A1:2010 or BS EN1542:1999 and also the American standard ASTM D7234.

The bond strength is determined as the failure tensile stress applied by a direct load perpendicular to the bond area. The bond strength is calculated as the quotient between the failure load and the test area. The test area is defined by coring through the screed or topping into the substrate.

Testing is carried out as follows

1. A minimum of 5 test areas of approximately 50mm cross section are cored through the screed material or coating. The cutting will extend through the screed to a depth of more than 5mm into the substrate (usually concrete)
2. The pull head plates (or dollies) are then bonded centrally to the test areas with a suitable adhesive. The adhesive will be allowed to cure overnight.
3. The tensile load shall be applied perpendicular to the test area through the pull head plates using the pull off tester. The load is applied without shock and at a uniform rate.
4. The failure load is recorded. The bond strength is calculated as the mean value of all the failure loads recorded.
5. From a visual assessment, the type of failure of the specimen is determined. If there is a combination of types of failure, a visual inspection of the failure face to estimate the percentage of each type of failure, based on the surface area is required.

e.g. Cohesive failure in the concrete substrate, failure between the substrate and the screed, cohesive failure in the screed, failure between the adhesive layer and the pull-head plate.

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