Environmental Engineering Reference
In-Depth Information
laboratory methods were used by Mamillan [MAM 64] to show the efficiency of
chemical cleaning methods of the calcin layer on limestones.
These equivalent tests consist of scratching the surface of the material with a
point. The width of the scratch is function of the superficial hardness. This method is
used to quantify the hardening of limestones due to sulfation [VER 96].
We can also find the norm NF B 10-507, “Produits de carriers - pierres calcaires
- mesure de la dureté Vickers” [AFN 73c]. This norm, usually used for metal, has
been adapted to rocks here.
Older abrasion tests remain: NF B 106508 [AFN 73d] and RILEM test n°IV.2
“Abrasion strength”. In both cases, abrasion strength is given by the amount of
matter removed with a grained abrasive in specific conditions.
A last test is proposed by RILEM (n°IV.3 “Superficial hardness measured by
rebounding”). It is carried out with the help of a sclerometer. The principle of the
measure relies on the rebound of a steel bowl. The superficial hardness corresponds
to the ratio between the kinetic energy of a bowl that falls and the energy elastically
recovered when it bounces.
10.1.3.8.
Freezing test
This behavior test allows us to determine the freezing resistance of natural
stones, but it can be also be used to characterize the state of rock alteration. In fact, a
stone block that is more resistant to this test is in a low state of alteration.
The norm NF B 10-513” [AFN 91] provides the procedure that should be
followed for this test. The material has to be dried before testing. Freezing and thaw
cycles are carried out as follows: six hours at freezing conditions in the air, then six
hours of thawing in water.
During the cycles, the alteration is monitored by visual examination of the
samples. Damage due to this cycling may be quantified, i.e. by measuring the
longitudinal dynamic elasticity modulus [AFN 75b].
RILEM, in test n°IV.2 “Freezing strength”, proposes a similar test with freeze-
thaw cycles identical to the French norm.
10.1.3.9.
Salt crystallization
Salt crystallization forces are very important. Within stone blocks, they can
result in cracks leading to blasting of the rock. A laboratory test is provided by NF B
