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Bowers Basebed 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 1,136 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
Material Description:
Cream fine to medium oolitic and bioclastic limestone containing bioclasts (5mm in width by 20mm in length)
Material Composition:
Ooliths: 75%
Bioclasts: 15%
Sparry Calcite Cement: <1%
Quartz: 1%
Voids: 9%
Petrographic details
The rock was a grain supported oobiomicrite made up of predominantly rounded micritic ooliths showing concentric structure and ranging from 50 µm to 300 µm in diameter, numerous bioclasts up to 5 mm by 20 mm in size and sporadic irregular quartz grains 100 µm nominal size. There was an apparent pressure adhesion of the grains and some matrix between the ooliths and this results in occasional intergranular voids. Sporadically sparry calcite infilled or partially infilled intergranular spaces or replaced central parts of bioclastic debris.
The ooliths consisted of micritic calcite and the bioclasts generally exhibited original aragonitic texture.
The rock contained occasional voids 100 µm nominal size. The micrite was also microporus with pores beyond the resolution of a transmitted light petrological microscope.
No deleterious constituents or features were observed.
B. Strength
1. Compression - BS EN 1926
Average: 55.39 Mpa from 54 tests
Lowest Expected Value 27.41 Mpa
Highest Expected Value 100.22 Mpa
2. Flexural Strength - BS EN 13161
Average: 7.16 Mpa from 68 tests
Lowest Expected Value 4.06 Mpa
Highest Expected Value 11.50 Mpa
3. Breaking Load at Dowel Hole - BS EN 13364
Average:
4,601 N from 20 tests
Lowest Expected Value
3,459 N
Highest Expected Value
5,950 N
C. Durability
1. Water Absorbtion BS EN 13755
Average: 5.21% from 119 tests
Lowest Expected Value 3.33%
Highest Expected Value 8.42%
2. Density BS EN 1936
Average: 2,226 kg/m³ from 287 tests
Lowest Expected Value
2,124 kg/m³
Highest Expected Value
2,331 kg/m³
3. Porosity BS EN 1936
Average:
15.36% from 448 tests
Lowest Expected Value
12.69%
Highest Expected Value
18.37%
4. Saturation Coefficient BS EN 1936
Average:
0.76 from 251 tests
Lowest Expected Value 0.67
Highest Expected Value 0.85
5. Salt Crystallisation BS EN 12370
Average: 62.18% from 81 tests
Lowest Expected Value 25.29%
Highest Expected Value 100%
D. Abrasion & Slip Resistance
Test results specific to Flooring/Paving
1. Abrasion Resistance – EN14157
Average: 23.57 from 9 tests
Lowest Expected Value 19.78
Highest Expected Value 27.92
2. Slip Resistance – TRRL Pendulum Test
Grit 120 (Internal Flooring)
Wet Average 71 from 48 tests
Lowest Expected Value 69
Highest Expected Value 87
Dry Average 91 from 24 tests
Lowest Expected Value 87
Highest Expected Value 95
Internal Flooring
Bowers Basebed is suitable for all flooring applications up to semi-intensive use such as shops and offices with estimated visitor numbers of 5,000,000 with a service life without significant wear of 20 years. The slip resistance results of over 40 demonstrate that the stone will be safe in all applications.
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 Basebed is traditionally acknowledged as being less durable than Whitbed but it has been used extensively where a faster rate of weathering is acceptable or where its working qualities were required. It is possible to compare the results for the Basebed Stone from Bowers Quarry to those collected from buildings, exposure trials and tests on quarry samples collected by BRE during the last 70 years. This shows that the stone compares well with the traditional view of Portland Basebed. Previous research at BRE has shown that Portland limestone which has a low saturation coefficient (>0.72), a high microporosity (>11.0 of the stone by volume) and an increased amount of micritic matrix will weather more rapidly than Whitbed when used on buildings. The results summarised on these sheets show that most of the samples tested are of this type. The crystallisation test results show the stone to be Class D -E which BRE Report 141 suggests that it is suitable for plain walling and cladding. The results from the other tests suggest that soundest stone may well perform better than this class in the current environment. Where more severe exposure conditions are expected, for example high concentrations of sulphur dioxide or severe frosts, or where a long life is required (for example >50 years) then it may be desirable to use a more durable stone (e.g. Portland Whitbed). When using Bowers Basebed it is especially important that the detailing of the stonework is designed to offer the maximum protection to rainwater and rainwater runoff.
Based on current research it seems likely that the stone would weather at a rate of between 3 and 4 mm per 100 years but it could be greater in severe exposures or on the edges of stonework.
(Weathering rates are based on the BRE interpretation of historical data dating from 1932)
Revision 6
December 2007
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