|
Bowers Whitbed 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 314 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
The stone was classified as a moderately sorted, moderately compacted, clast supported OospariteLimestone. The clasts were predominantly composed of ooliths, but mollusc shell and echinodermfragments and quartz were also present. The matrix was composed of sparitic syntaxial carbonate and some micritic carbonate. There was a moderate to high abundance of open voidage space. There was possibly some evidence of sedimentary bedding by the preferred alignment of elongate clasts.
B. Strength
1. Compression - BS EN 1926
Average: 37.70 Mpa from 45 tests
Lowest Expected Value 22.98 Mpa
Highest Expected Value 58.31 Mpa
2. Flexural Strength - BS EN 13161
Average: 5.57 Mpa from 40 tests
Lowest Expected Value 2.86 Mpa
Highest Expected Value 9.77Mpa
2.
Breaking Load at Dowel Hole - BS EN 13364
Average: 5,098 from 20 tests
Lowest Expected Value 3,359 N
Highest Expected Value 7,347 N
C. Durability
1.
Water Absorption - BS EN 13755
Average: 7.36% from 120 tests
Lowest Expected Value 6.29%
Highest Expected Value
8.55%
2.
Density - BS EN 1936
Average: 2,082 kg/m³ from 135 tests
Lowest Expected Value
2,005 kg/m³
Highest Expected Value
2,161 kg/m³
3.
Porosity - BS EN 1936
Average: 22.86% from 269 tests
Lowest Expected Value 20.70%
Highest Expected Value
25.15%
4.
Saturation Coefficient – BS EN 1936
Average: 0.63% from 190 tests
Lowest Expected Value
0.58
Highest Expected Value
0.69
5. Salt Crystallisation
Average: 5.83% from 36 tests
Lowest Expected Value 0.18%
Highest Expected Value 36.93%
D. Abrasion & Slip Resistance
Test results specific to Flooring/Paving
1. Abrasion Resistance – EN14157
Average: 22.14 from 9 tests
Lowest Expected Value 18.55
Highest Expected Value 26.28
2. Slip Resistance – TRRL Pendulum Test
Grit 60 (External Paving)
Wet Average: 83 from 23 results
Lowest Expected Value 81
Highest Expected value 86
Internal Flooring
Bowers Whitbed 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 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 Whitbed is traditionally acknowledged as generally being a very durable building stone and it has been used extensively in many towns and cities in the UK . Comparing the results for the Whitbed Stone from Bowers Quarry to those collected from buildings, exposure trials and tests on quarry samples collected by BRE during the last 70 years shows that this stone compares very well with the traditional view of Portland Whitbed. Previous research at BRE has shown that Portland limestone which has a low saturation coefficient (<0.72), a low microporosity (<11.0 of the stone by volume) and an open oolitic structure generally performs well over long periods when used on buildings. The results summarised on these sheets show that the limited number of samples tested meet seem to meet these criteria. The crystallisation test results show the stone to be Class B-C which BRE Report 141 suggests is suitable for most uses including where exposure conditions are to be more severe, for example high concentrations of sulphur dioxide or severe frosts, or where a long life is required (for example >50 years). In all cases it is important that the detailing of the stonework is designed to offer the maximum protection from rainwater and rainwater runoff.
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 7
DECEMBER 2007
|
