Jordans Whitbed has a Medium shell content. Inclusions being predominantly grey with some occasional white fragments. The shells are mainly large thin clams up to 80mm long laid parallel to the bedding.
The shells are randomly distributed across the stone, but due to the large clam shells, banding is evident particularly in larger slabs.
Mostly a tight uniform matrix with some evidence of openness and voids associated with light shell banding.
Typical Portland colour - creamy/white mellowing to grey/white over time.
The stone was classified as a moderately sorted, moderately compacted, clast supported Oosparite Limestone. The clasts were predominantly composed of ooliths, but mollusc shell and echinoderm fragments 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.
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Compression - BS EN 1926
Lowest Expected Value 35.53 Mpa
Highest Expected Value 61.06 Mpa
Average: 47.04 Mpa from 26 tests
Flexural Strength - BS EN 13161
Lowest Expected Value 3.75 Mpa
Highest Expected Value 9.32 Mpa
Average: 6.11 Mpa from 72 tests
Breaking Load at Dowel Hole - BS EN 13364
Lowest Expected Value 3,749 N
Highest Expected Value 5,668 N
Average: 4,667 N from 20 tests
Water Absorption - BS EN 13755
Lowest Expected Value 5.48%
Highest Expected Value 8.69%
Average: 6.93% from 18 tests
Density - BS EN 1936
Lowest Expected Value 2,021 kg/m³
Highest Expected Value 2,132 kg/m³
Average: 2,101 kg/m³ from 30 tests
Porosity - BS EN 1936
Lowest Expected Value 19.35%
Highest Expected Value 24.58%
Average: 21.85% from 34 tests
Saturation Coefficient - BS EN 1936
Lowest Expected Value 0.61
Highest Expected Value 0.66
Average: 0.64 from 10 tests
Freeze/Thaw – BS EN 12371 & 12372
168 Freeze/Thaw Cycles
Mean Value 3.5 MPa
38% reduction in strength
Abrasion Resistance - EN 14157
Lowest Expected Value 20.55
Highest Expected Value 28.99
Average: 24.48 from 9 tests
Slip Resistance - TRRL Pendulum Test: Grit 120 (Flooring)
Lowest Expected Value 68
Highest Expected Value 84
Wet Average value 76 from 24 tests
Lowest Expected Value 79
Highest Expected Value 97
Dry Average value 88 from 24 tests
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 Jordans 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 these criteria. The average crystallisation test results show the stone to be Class 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)
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