Introduction - Geomaterials: Under the Microscope - page 3

to other construction materials. The technique requires
specialist equipment and operators with appropriate
qualifications and petrographic experience. Through the
microscope the petrographer can determine the composi-
tion of geomaterials, assess their quality, and investigate
the causes and extent of deterioration. Photographs taken
through the microscope (photomicrographs) provide
compelling evidence for clients. Around the world, tens of
thousands of petrographic examinations are performed on
construction materials each year. The main requirements
for a commercial geomaterials petrography laboratory are:
• It must led by an experienced
petrographer/geomaterials practitioner.

• The examinations should be conducted using very
high-quality optical microscopes.
• It should have good in-house specimen preparation
facilities.
• An extensive collection of petrographic specimens
should be available for the petrographers' reference.
• There should be access to complementary
microscopical and chemical analysis techniques.

Commercially, petrographic examination is conducted in
accordance with the published standards listed in Table 2 .
Standard methods have still to be agreed for certain types
of material and in certain geographic regions.

Table 2 Current standards for the petrographic examination of geomaterials

Material British standard European standard American standard

Building stone Use European standard EN 12407 1 WK2609 2

Roofing slate Use European standard EN 12326-2 3 None*

Rock None, use ISRM 1977 4 and BS 5930 5

Armourstone Use European standard Use EN 932-3 6 None*

Aggregate BS 812-104 7 EN 932-3 6 ASTM C295 8

Concrete None - use American standard None - use American standard ASTM C856 9

Mortar None - use American standard None - use American standard ASTM C1324 10

Bricks and ceramics None* None* None*

Bituminous mixtures None* None* None*

* Adapt the techniques described in other petrography standards as appropriate.
1 British Standards Institution (2007). Natural Stone Test Methods - Petrographic Examination:BS EN 12407. BSI, London.
2 ASTM International (2006). New Standard Guide for Petrographic Examination of Dimension Stone.WK2609 (proposed new
standard in draft form and under development). ASTM International, Philadelphia.
3 British Standards Institution (2000). Slate and Stone Products for Discontinuous Roofing and Cladding - Part 2: Methods of Test:BS
EN 12326-2. BSI, London.
4 International Society for Rock Mechanics (ISRM) (1977). Rock Characterisation, Testing and Monitoring. Suggested Method for the
Petrographic Description of Rock.Pergamon Press, Oxford.
5 British Standards Institution (1999). Code of Practice for Site Investigations:BS 5930. BSI, London.
6 British Standards Institution (1997). Tests for General Properties of Aggregates - Part 3: Procedure and Terminology for Simplified
Petrographic Description:BS EN 932-3. BSI, London.
7 British Standards Institution (1994). Testing Aggregates - Part 104: Method for Qualitative and Quantitative Petrographic
Examination of Aggregates:BS 812. BSI, London.
8 ASTM International (2008). Standard Guide for Petrographic Examination of Aggregates for Concrete.ASTM C295-08. ASTM
International, Philadelphia.
9 ASTM International (2004). Standard Practice for the Petrographic Examination of Hardened Concrete.ASTM C856-04. ASTM
International, Philadelphia.
10 ASTM International (2005). Standard Test Method for Examination and Analysis of Hardened Masonry Mortar.ASTM C1324-05.
ASTM International, Philadelphia.