Laboratory tests are essential to control the suitability of a stone to a specific work, including the dimensioning of parts and even definition of the placement system.
In the present case, the product standard “Natural stone tiles for use as outdoor flooring” (UNE-EN 1341:2013) indicates the basic tests to be performed for pavement marketed in Europe to be used outdoors:
In addition to these tests, others more specific can be made if the area where it is to be placed requires it, such as extreme climates, regular use of salts for thawing, etc.
All tests have a validity of 10 years, except for water absorption, density, porosity, and resistance to bending, which must be renewed every 2 years.
What are these tests used for?
-The resistance to bending is essential when sizing a pavement to avoid this type of breaks in the stone (see entry on the blog “Size your pavement” of June 9, 2017).
-To foresee the wear which may have a pavement depending on the intensity of the traffic to which it is subjected, the test of abrasion resistance is performed.
-The safety against slippage in a pavement is evaluated with the test of slippage resistance. Falls due to slippage are the second cause of physical handicaps. The slipperiness of a stone depends on its surface finish, so the more rugged a surface, the more non-slip it will be.
– 56 frost/thaw cycles (resistance to freezing) are performed as accelerated aging or durability tests, reproducing climatic conditions such as frost. Here the stone’s ability to maintain its essential characteristics of appearance, strength and resistance to decay is checked.56 frost/thaw cycles (resistance to freezing) are performed as accelerated aging or durability tests, reproducing climatic conditions such as frost. Here the stone’s ability to maintain its essential characteristics of appearance, strength and resistance to decay is checked.
– Water is the main agent for a rock to begin to alter; this occurs because the water circulates through the pores and fissures of the rock favouring the disturbance to a mineral scale, transport of salts, appearance of efflorescence, etc. The absorption of water at atmospheric pressure and open porosity are two of the tests that are used to predict if the stone will be more susceptible to be altered or less in rainy and/or humid areas. Granites, which have a fissured porosity, have a very low open porosity, generally about 1%, hence their low alterability compared to other natural stones or other building materials.
– The petrographic study, serves to define the type of rock, to know its mineralogical composition, grain size, texture, structure, porosity type, etc. allowing to know if there are potentially alterable minerals, if it has any type of oriented discontinuity that can affect the resistance of the stone or even the degree of alteration on a mineral scale, etc., all to avoid pathologies in works due to stone, contribute to the design of cleaning and maintenance protocols, etc.
Nuria Sánchez Delgado
Doctor in Geology
CENTRO TECNOLÓGICO DEL GRANITO DE GALICIA