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Bowers Roach technical data

This technical data sheet was compiled by the Building Research Establishment (BRE) at the request of Albion Stone and is updated by Albion Stone to incorporate current test results. The 866 tests have been carried out in accordance with current European standards by the BRE on Albion Stone's behalf, or by other accredited testing houses. The early test data that pre-dates the introduction of Euro-codes has been included providing the test methods were very similar. The work carried out by the BRE on this technical data sheet has been undertaken as a paid commission and does not represent an endorsement of the stone by the BRE.

This data includes the Lowest and Highest Expected Values (LEV & HEV) using the statistical calculations from the Euro-codes. We are confident that these results give a good indication of the stones value, but as it is a natural material we, like other stone producers, are unable to guarantee individual results for specific stones. Instead, we recommend that an appropriate factor of safety is used to ensure satisfactory performance, Annex 1 of the Technical Manual provides further information, but we suggest that a suitably qualified stone consultant with geological and testing experience is employed to provide further information.

Petrography

The stone is an open textured oolitic limestone from the Portlandian formation (Jurassic). The stone is formed from ooliths in a micrite (fine grained calcium carbonate) matrix. It is an extremely shelly stone with a large number of holes scattered throughout it. The holes are due to the removal of fossil shells by percolating rain. The finer-grained parts of the stone is very similar to Whitbed.

Strength

Compression - BS EN 1926
Lowest Expected Value 23.96 Mpa
Highest Expected Value 75.09 Mpa
Average: 44.24 Mpa from 32 tests

Flexural Strength - BS EN 13161
Lowest Expected Value 2.02 Mpa
Highest Expected Value 6.70 Mpa
Average: 3.94 Mpa from 140 tests

Breaking Load at Dowel Hole - BS EN 13364
Lowest Expected Value 1,981 N
Highest Expected Value 8,264 N
Average: 4,288 N from 30 tests

Durability

Water Absorption - BS EN 13755
Lowest Expected Value 3.38%
Highest Expected Value 9.71%
Average: 5.99% from 153 tests

Density - BS EN 1936
Lowest Expected Value 2,023 kg/m³
Highest Expected Value 2,551 kg/m³
Average: 2,205 kg/m³ from 212 tests

Porosity - BS EN 1936
Lowest Expected Value 18.52%
Highest Expected Value 26.56%
Average: 22.31% from 117 tests

Saturation Coefficient - BS EN 1936
Lowest Expected Value 0.59
Highest Expected Value 0.67
Average: 0.65 from 111 tests

Salt Crystallisation - BS EN 12370
Lowest Expected Value 1.18%
Highest Expected Value 5.91%
Average: 2.88% from 11 tests

Abrasion Resistance

Abrasion Resistance - EN14157
Lowest Expected Value 20.29
Highest Expected Value 24.95
Average: 22.5 from 12 tests

Slip Resistance - TRRL Pendulum Test: Grit 120 Filled (Internal Flooring)
Lowest Expected Value 82
Highest Expected Value 88
Wet Average 85 from 48 tests

Internal Flooring
Bowers Roach is suitable for all flooring applications up to intensive use such as shopping centres and airports with estimated visitor numbers of 500,000,000 with a service life without significant wear of 20 years. The dry slip resistance results of over 40 demonstrate that the stone will be safe in all normal applications, however the wet figure of 31 would suggest that safety should be carefully considered if the stone is used in a wet area such as a swimming pool surround or shower tray.

Technical summary

Prepared by: Dr T Yates, BRE (Building Research Establishment)

Durability and Weathering
It is important that the results from the sodium sulphate crystallisation tests are not viewed in isolation. They should be considered with the results from the porosity and water absorption tests and the performance of the stone in existing buildings. Stone from the Portland Roach bed is traditionally acknowledged as being very durable and is comparable with Whitbed. It has been used in extreme environments, for example coastal walls. It is difficult to compare the results for the Roach Bed Stone from Bowers Quarry to those collected from buildings and exposure trails as the stone has been little used in building construction. However, the overall test results suggest that the stone compares well with the traditional view of Portland Whitbed. Previous research by the BRE has shown that Portland Limestone which has a low saturation coefficient (>0.72) will have good weathering resistance when used on buildings. The crystallisation tests results show the stone to be Class A-B which BRE Report 141 suggests that it is suitable for most uses.

Based on current research it seems likely that the stone would weather at a rate of between 1 and 2 mm per 100 years but it could be greater in severe exposures.

(Weathering rates are based on the BRE interpretation of historical data dating from 1932)