Environmental Engineering Reference
In-Depth Information
10.1.3.2.
Uniaxial compressive strength test
The compressive test is the most classical of mechanical tests. Thanks to its
simplicity, it is the most easily adapted to quantify the weakening of mechanical
properties of stone linked to its state of alteration. The corresponding French norm is
the “Test methods for natural stones - determination of compressive strength” [AFN
99b]. This norm enables various probe shapes: cubes or drill cores. The material is
dried before testing. At least five specimens are required to limit dispersion of
measurements made. RILEM proposes a similar test to this called n°III.5 “Rupture
compressive strength”.
Although it was initially defined for ground tiles, it is possible to refer to UPEC
classification to determine the compatibility of replacement stones for elevation,
structure and ground pavement.
N
OTE
: These mechanical tests are usually performed on dry materials. By
carrying out these tests on water-saturated specimens, a low limit would be obtained
for strength that would only be encountered in extreme conditions
in situ.
10.1.3.3
. Traction strength test
Whereas stones in building masonry are scarcely submitted to traction, such
forces may occur as a result of compressive strengths. A traction strength test may
be relevant to evaluate the conservation state of a material. For this purpose, tests or
norms can be used:
- RILEM test n°III.4 “traction test”. A load is applied continuously and
smoothly at both extremities of the specimen. The rupture constraint, which is
obtained, is expressed as the ratio of the load over the affected surface of the
specimen.
- Splitting test, so-called “Brazilian test” [AFN 81a]. This norm deals with
concrete specimens, but can also be applied to rocks.
- ISO 4108, February 1980 “Concrete - determination of the rupture in traction
by splitting of specimens” [AFN 80].
10.1.3.4.
Flexure strength test
A flexure strength test may be discriminating regarding the damage state of a
stone block. One of the current norms is the NF EN 12372, “Test method for natural
stones - determination of the flexure strength under central load” [AFN 99c]. The
test is carried out on specimens of dimension (7X7X28) cm
3
, the material being
dried before the test and at least five specimens used. The Young's modulus given
by the test will be expressed in N/mm
2
. In test n°III.6, RILEM proposes another
