Grove Whitbed

Portland Stone Grove Whitbed

 

Description

Shell Content

Shelly Whitbed - predominantly grey shells with some large white shell fragments. The shells are mainly large thin clams up to 100mm long laid parallel to the bedding.

Shell Distribution

The shells are randomly distributed across the stone, but due to the large clam shells, some banding is evident particularly in larger slabs.

Texture

The large clam shells are associated with voids. The texture in between the voids is often tight and dense.

Colour

Typical Portland colour - creamy/white, although the large concentrations of grey shells can darken the overall colour.

Technical data

This appeared to be a fine-grained sedimentary 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 3 µm 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.

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 2.47 MPa
Highest Expected Value 8.13 MPa
Average: 6.03 MPa from 82 tests

Flexural Strength - BS EN 12372 (Pre-thermal testing)
Lowest Expected Value 3.83 MPa
Highest Expected Value 6.15 MPa
Average: 4.88 MPa from 10 tests

Flexural Strength - BS EN 12372 (After 20 cycles - BS EN 14066)
Lowest Expected Value 4.04 MPa
Highest Expected Value 7.11 MPa
Average: 5.40 MPa from 10 tests

Breaking Load at Dowel Hole - BS EN 13364:2002

Specimen Thickness (mm)

Mean Breaking Load (N)

Lowest Expected Value (N) /
Highest Expected Value (N)

75

4667

3749 / 5668

60

2249

1777 / 2816

50

1860

1460 / 2342

40

1191

922 / 1519

30

667

539 / 817

Water Absorption - BS EN 13755
Lowest Expected Value 3.54%
Highest Expected Value 10.30%
Average: 6.29% from 49 tests

Density - BS EN 1936
Lowest Expected Value 2,002 kg/m ³
Highest Expected Value 2,315 kg/m ³
Average: 2,155 kg/m ³ from 60 tests

Porosity - BS EN 1936
Lowest Expected Value 13.88%
Highest Expected Value 25.79%
Average: 19.24% from 83 tests

Saturation Coefficient - BS EN 1936
Lowest Expected Value 0.56
Highest Expected Value 0.92
Average: 0.73 from 22 tests

Salt Crystallisation - BS EN 12370
Lowest Expected Value 0.00%
Highest Expected Value 6.14%
Average: 2.05% from 6 tests

Thermal Shock Resistanc - €”BS EN 14066 
% change in elastic modulus
Lowest Expected Value 0%
Highest Expected Value 32%
Average: 4.51% from 10 tests

Water Absorption by Capillarity - BS EN 1925
59.41g/m ².sec-2

Freeze/Thaw - BS EN 12371 & 12372
168 Freeze/Thaw Cycles
Mean Value 3.5 MPa
38% reduction in strength
Pass

Abrasion Resistance - EN14157
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

Light Reflectance - tested using NCL Colour Scan instrument - Grit 60
Mean Value 57

Internal Flooring
Grove Whitbed 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.

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, Cladding 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.

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 (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 run-off. 

Based on current research it seems likely that the stone would weather at a rate of between 1 and 2mm 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).

Mine Report No. 85

  • Winter 2017
  • Jordans Mine, Portland

Maximum Block Sizes

  • Overall Size: 10.44m³
  • Length: 4.4m
  • Bed Height: 2.90m

Average Block Sizes in Stock

  • Overall Size: 2.77m³
  • Length: 1.92m
  • Bed Height: 1.25m

Current Availability

  • (0-3 months) 9,000-10,000m³

Future Availability

  • (3-12 months) 10,000-12,000m³

CE Certificates and Declarations of Performance

Technical Data Sheets

Specification Clauses