In the UNI EN 1015-12 a method for determining the adhesion between a plaster mortar and the support is defined as: "Determination of adhesive strength by pull-off of hardened rendering and plastering mortars on substrates. The adhesive strength is applied by a plate affixed on the surface of the mortar test "(UNI EN 1015-12).

For the performance of this test we need the cylindrical bronze or stainless steel rings with the truncated cone profile  (diameter: 50 ± 0.1 mm and height: 25 ± 0.5 mm, thickness of at least 5 mm), the metal stainless steel plates (diameter: 50 ± 0.1 mm and a minimum thickness of 10 mm), the adhesive-based resin, an apparatus for coring and a machine for Pull-Off test.

The support on which to perform the test, in case where it is not defined a specific support it is necessary to use concrete panels, rectangular of dimensions 550 mm x 150 mm and a thickness of 50 mm, cured for at least 28 days before plastering.

To perform the test, prepare at least 1.5 l of mortar (in volume terms) and at least two test samples.

After 10 minutes of mixing conclusion it is important to apply at least 10 ± 1 mm mortar on the support (held vertically).

In the layer of mortar, both in the fresh that in that hardened, it is necessary cutting five circular test surfaces (diameter about 50 mm); or after the application and start setting of the layer of mortar, press the cylindrical rings (lubricated) on the mortar until it reaches the support, respecting a minimum distance of 50 mm.

After curing of plaster mortar, the samples must be cut out using a core drill device (up to a depth of about 2 mm within the support).

Once mortar is hardened, we put the samples in a wrap (polyethylene sheet sealed) and store them for 7 days at (20 ± 2)°C. Subsequently, it is necessary to remove them from the package and store them in air at temperature of (20 ± 2)°C and a relative humidity of (65 ± 5)% for 21 days.

Once the curing time is ended, it is necessary to apply the metal plates in a central position on the test areas. After 28 days, you must apply adhesive strength in a gradual way and without tears (with speed between 0.003 N / (mm2 × s) and 0.100 N / (mm2 × s), so as to have the gap in a time between 20 s and 60 s.

 

Material type Standard Test method
restoring EN 1504-3 EN 1542
surface protection mortars EN 1504-2 EN 1542

 

Instruments used to perform the test: Core drill, Pull-off

 

The test describes a method for determining the adhesion between a plaster mortar and the support.