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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 707 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 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.
A. Petrography
Macro Examination
This is a fine-grained sedimentary rock – probably limestone. Light creamy-white coloured matrix containing an abundance (>10%) of highly elongate light-grey (brownish-grey when weathered) coloured fossiliferous material. This material was orientated primarily in one direction which probably represented bedding. These fossiliferous clasts were observed up to 3mm in length. Voidage appeared modest and the fluorescent resin take up appeared high. This sample appeared to be a fairly uniform fine-grained material in which no bedding or linear features other than the fossiliferous material was apparent.
Microscopical examination
This limestone exhibited a moderately well compacted structure, which had moderate to poorly sorted appearance. No microcracking, linear or bedding related features other than the preferential orientation of the fossiliferous clastic material were observed. The clast to matrix ratio was approximately 90:10. Clast to matrix bond appeared good, with no separation cracks detected.
Clasts
These consisted of materials having a great range of sizes (3000µms down to <10µms). The larger fossiliferous material (>1mm) was elongate and was comprised primarily of Brachiopoda and Mollusc valves. Internally some of these clasts had open porosity now partially filled with secondary sparitic calcite. There was also evidence of conversion or replacement of the internal areas of some shells by large quartz crystals.
The finer (>1mm) material was also composed largely of fossiliferous materials including Brachiopoda and mollusc valves, along with bryozoa stems, algal material and colonial corals. However, the majority of this finer material was composed of micritised Ooliths, some of which were seeded with quartz sand grains and fossil debris. Other less abundant clastic constituents included included lithoclasts (Oosparite/Oomicrite). The edges of the larger clasts and all of the finer material were composed of micrite size carbonate material. Worm action was observed on a pre-existing fossil shell fragment.
The clastic material was dominated by fossiliferous material with an almost equal amount of oolitic material also present. The fossiliferous clasts were more prominent in the coarse sized material
Matrix
Though relatively rare, the matrix appeared to consist primarily of micrite-sized material. Some secondary sparite crystallisation had developed in some of the voidage and this partially filled some inter and intra-clastic voidage. Matrix material was felt to represent only a small component of the rock.
Voidage
This was felt to be in the range medium to high and was present largely at the finer <200µms size within individual voids. Occasional larger voids up to 4mm in length were found associated with a localised abundance of larger fossiliferous clasts and a lack of matrix material. The voidage was mainly inter-particle, but some partially filled intra-particle voidage and shelter voidage was detected. A visual estimation of the voidage, which was slightly patchy in appearance, ranged from 15 to 25%.
Composition
The clastic (ooliths and fossiliferous) material was composed of non-ferroan calcite. Micritic matrix material was composed of non-ferroan calcite. The relatively rare secondary sparite carbonate was composed of non-ferroan dolomite and non-ferroan calcite. Trace amounts of quartz sand grains, chert and silica associated with belemnite spins were detected but were felt to resent less than 1% of the total rock
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Classification
On the basis of the features described in this report, this rock would be classified as Oomicrite. However, it does contain an abundance of large fossiliferous material clasts.
(Test of the Grove Whitbed in Independent)
B. Strength
1. Compression - BS EN 1926
Average: 44.24 Mpa from 32 tests
Lowest Expected Value 23.96 Mpa
Highest Expected Value 75.09 Mpa
2. Flexural Strength - BS EN 13161
Average: 3.94 Mpa from 140 tests
Lowest Expected Value 2.02 Mpa
Highest Expected Value 6.70 Mpa
3. Breaking Load at Dowel Hole - BS EN 13364
Average: 4,288 N from 30 tests
Lowest Expected Value 1,981 N
Highest Expected Value 8,264 N
C. Durability
1. Water Absorbtion BS EN 13755
Average: 5.99% from 153 tests
Lowest Expected Value 3.38%
Highest Expected Value 9.71%
2. Density BS EN 1936
Average: 2,205 kg/m³ from 212 tests
Lowest Expected Value 2023 kg/m³
Highest Expected Value 2551 kg/m³
3. Porosity BS EN 1936
Average: 22.31% from 117 tests
Lowest Expected Value 18.52%
Highest Expected Value 26.56%
4. Saturation Coefficient BS EN 1936
Average: 0.63 from 111 tests
Lowest Expected Value 0.59
Highest Expected Value 0.67
5. Salt Crystallisation
Average: 2.88% from 11 tests
Lowest Expected Value 1.18%
Highest Expected Value 5.91%
D. Abrasion & Slip Resistance
Test results specific to Flooring/Paving
1. Abrasion Resistance – EN14157
Average: 22.5 from 12 tests
Lowest Expected Value 20.29
Highest Expected Value 24.95
2. Slip Resistance – TRRL Pendulum Test
Wet Average 85 from 48 tests
Grit 120 Filled (Internal Flooring)
Lowest Expected Value 82
Highest Expected Value 88
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 generally being a 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 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)
Revision 6
DECEMBER 2007
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