The term adhesion strength indicates the maximum measurable resistance for unit surface area by means pull-off or cutting (UNI EN 120004). In the UNI EN 1348 a method for the determination of this resistance (by pull-off on cementitious adhesives for ceramic tiles) is defined. It is applicable to cementitious premixed adhesives or separate components for interior and exterior coatings and walls (UNI EN 1348).

To perform the test you need of 10-square-size ceramic tiles (50 ± 1) mm x (50 ± 1) mm, Pull-off able to exert a force of (250 ± 50) N/s, 10 metal plates of dimensions (50 ± 1) mm x (50 ± 1) mm and a minimum thickness of 10 mm with a connection to the Pull-Off, loads able to exert a force of (20 ± 0.05) N with a section of 50 mm x 50 mm, a notched trowel and a concrete slab.

The concrete slab, according to the UNI EN 1323, must have a minimum thickness of 35 mm, a lower moisture content of 3% mass, a surface absorption after 4h included between 0.5 cm3 and 1.5 cm3.

To carry out this test, prepare a minimum 2 kg of adhesive (primarily housing for the liquid in the mixer, then the mass and mixed for 30 seconds. After removing the paddle, it is necessary clean it and mix it again finally for 1 min).

Once the adhesive is prepared, apply a thin layer on the concrete slab, with a smooth trowel. Subsequently, a thicker layer with the notched part of the trowel (with an angle of 60 ° compared to the support). After 5 min., 10 tiles are placed, distancing of 50 mm and loaded with a weight of (20 ± 0.05) N for 30 s. After 27 days of curing under standard conditions (22 ± 2°C and 50 ± 5% relative humidity) must be applied on the tiles, with a glue high strength of adhesion, the metal plates. After 24 hours (always in standard conditions) you can be determined the bonding stress (in MPa) of the adhesive using a Pull-Off.

After using the Pull-Off you can have different types of breaking, ie:

  • adhesive breaking between adhesive and substrate;
  • adhesive breaking between tile and adhesive;
  • adhesive breaking between tile and adhesion plate;
  • cohesive breaking in the adhesive;
  • cohesive breaking in the support;
  • cohesive breaking in the tile.

 

Material typeStandardTest method
adhesives EN 12004 EN 1348
waterproofing EN 14891 EN 14891 §A.6.2

 

Instruments used to perform the test: Pull-off

 

Maximum resistance for unit surface measured by pull-off or cut tests. The method is applicable to cementitious premixed adhesives or with separate components for interior and exterior walls and coatings.