Dimension Stone Testing
With the opening of the world stone trade through the internet stone is now readily available to anyone - from anywhere. But what does the purchaser know about the technical characteristics of the stone and how do those characteristics impact on the immediate and long-term performance of the stone in its intended applications?
Where the stone is a structural element in any construction it is necessary to assess a number of engineering parameters to establish its limitations - much the same as other construction elements. However, being a natural material, as opposed to manufactured, the range of variation in stone is much greater and often unpredictable. And with over 12,000 stones available on the world market the differences in stone are considerable. Establishing the limitations of each stone is critical for successful construction.
To achieve this it is necessary to test the natural material. Over the
years a number of properties have been defined as being important in assessing
the performance of stone, namely the mineralogical, textural and structural
make-up (petrography), compressive strength (for load bearing), flexural strength
(for vertical applications), impact strength (modulus of rupture for paving),
absorption, slip resistance, stain resistance, salt resistance, and degree of
expansion. Collectively, these properties will determine where and
how the stone can be successfully used. A wide number of international
standards are in place to provide the necessary guidelines for testing to
ensure consistency during the testing and also between laboratories.
Importantly, stone is not a uniform product. Sedimentary rocks such
as sandstone are bedded, granitic rocks may contain veins, basaltic rocks may
contain vesicles, felsic volcanic rocks may contain a mineralogy that is
reactive to cements, and metamorphic rocks may contain unusual minerals with
properties that require careful investigation. A stone scientist or stone
specialist is required to organize and conduct the tests that will be
appropriate for the intended construction. Sending random samples of
stone to a laboratory is a total waste of time and money; a laboratory
technician does not know anything about the stone and its properties and
its intended application - he/she only has to know how to use the testing
apparatus and compile the results.
Hensel
Geosciences has a long history of stone, rock and mineral testing - from the
most sophisticated geochronological techniques (rock dating, isotopic
characterization), through mineral investigations (electron microprobe,
scanning electron microscope, X-ray diffraction, FTIR, XAS, ICP, XRF and
petrological studies), to the more fundamental tests required for stone and
rock analysis. Knowing what tests are required is important not only to
the client (in terms of costs) but also to the engineer (in terms of
suitability to facilitate construction). Additionally, knowing which
laboratories provide the most reliable results, at a good turn-around and at
the most reasonable price is advantageous in construction.
Hensel
Geosciences also has a long history in the evaluation of the test
results. Many test results of stone are manipulated and it is therefore
important to be able to discern the erroneous/inconsistent results. This
requires a long-term in-depth knowledge of the natural product that only comes
with experience. The most common form of data manipulation is in
sample selection; therefore it is fundamental that the stone scientist selects
the product and conducts the testing programme.
Requirements for sandstone testing Requirements for granite testing