Evaluation of Australian porphyry stone

A request was made to Stone Initiatives and Materials Testing Group Pty Ltd to carry out a series of testes on supplied samples of Australian Porphyry Stone.

RESULTS

Results are summarised in the table to the right, the results are compared with the ASTM specifications for granite(1) and sandstone(2) dimension stone.

DISCUSSION
4.1 Water Absorption/Bulk

Specific Gravity
The mean water absorption of the Australian Porphyry Stone was determined to 0.30% by weight, this compares favourably with the granite ASTM specification which specifies a maximum absorption level of 0.40%:
the result is considerably lower than the requirement stated in the sandstone specification. A lower water absorption capacity generally reduces the risk
of staining and the establishment of biological growths as well as assisting the stone’s durability. The mean bulk specific gravity of the Australian Porphyry Stone was determined to be 2.70 tonnes/metre(3), this figure also complies with both ASTM specifications.

4.2 Modules of Rupture
The mean modulus of rupture of the Australian Porphyry Stone was found
to be 23.2MPa dried and 27.5MPa in a soaked condition. These strength results comply with the requirements of both the granite sandstone ASTM specifications and is far superior to most dimension stone products on the market. The results make the stone eminently suitable for commercial paving projects particularly where the pavement maybe subjected to vehicular traffic.

4.4 Abrasion Resistance
The Australian Porphyry Stone was found to have a mean Abrasion Index of 52, the stone is considered to have high abrasion resistance; suitable for all commercial and domestic paving situations.

4.5 Resistance to Salt Attack (Durability) The mean weight loss of the Australian Porphyry Stone was determined to be less than 0.01% by weight, this gives the stone an AA Grade Durability classification that is considered suitable for all standard construction uses including pool surrounds or locations that are continually exposed to salt or wetting or drying cycles.

4.6 Slip Resistance
The split face surface of the Australian Porphyry Stone complies with the slip resistance requirements of the Sydney City Council.

With a V slip resistance classification(5), Australian Standards handbook HB 197.99 recommends that the split face surface is suitable for use in a wide range of locations including external ramps, colonnades, pool ramps and surrounds and external stairs.

(5)The highest slip resistance classification

4.3 Compressive Strength
The mean compressive strength of the stone was found to be 147.4MPa in a dried condition. This result complies with both ASTM specifications stated.