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STONE. CITY. IN. THE. Dr Tim Yates. BRE Ltd. There’s no such thing as bad stone – only badly used stone. Tim Yates, BRE 12 th March 2008, Stone in the City, The Natural Stone Show 2008 . Where do we begin ?. Choosing by appearance – colour, texture, etc
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STONE CITY IN THE
Dr Tim Yates BRE Ltd
There’s no such thing as bad stone – only badly used stone Tim Yates, BRE 12th March 2008, Stone in the City, The Natural Stone Show 2008
Where do we begin ? • Choosing by appearance – colour, texture, etc • Meeting a required performance – strength, durability • Performance or prescription? • Trial and error? • Past performance • Testing and assessment
How many types of stone are available? • Locally – for example Bath Stone • About 6 • Nationally – for example UK • Around 250 • World Wide – • Over 8000
Where do we begin ? Variable Variable Fixed Stone properties Project needs Failure! At the limit! Success! Fixed Project needs Stone properties Stone properties Project needs
How do we match a stone to a project? • Failure mode effect analysis • What can go wrong? • What can we test for this? • How can we manage the risk? • Is it safe? • Will it last? • Is it strong enough?
Specifying by experience Local Stone Trial and error Observation Experience Measurement Traditional Use Testing Classification Portland Stone in London - observation of balusters on buildings in Whitehall - failure of stone at the Palace of Westminster
Performance versus Product specification Example 1: • Resistant to 10 m/s wind loading • 70mm thick cladding • London limestone
Performance versus Product specification Example 2: • “Durable” for 50 years • Weathering rate 2mm per 100 years • Class B • London limestone (based on tradition)
Product specification • BS 8298: 1994 Design and installation of natural stone cladding and lining • Use stone like this and it will be alright • BS 680: 1971 Specification for roofing slates • Use slates that pass (Now replaced by BS EN123630 • BS5385 Part 5 :1994 Wall and Floor Tiling: Design and installation of terrazzo tile and slab, natural stone and composition block flooring • Doesn’t matter what you use as long as you do it right
Different types of test (1) • Index tests • Petrographic description • Porosity, Density and Water Absorption • Saturation Co-efficient • Strength tests • Compressive • Flexural • Modulus of Rupture • Strength around a fixing • Point load
Different types of test (2) • Durability tests • Freeze-thaw resistance • Salt resistance • Thermal Shock • Safety • Slip and skid resistance • Component tests • Wind loading • Fire • Impact
Deterioration of natural stone • Erosion and spalling • Large, solid stones • Loss of strength • Thermal and moisture cycles • Biological growths • Westminster Abbey, London
Deterioration of cladding • Bowing and distortion of marble cladding • Large, thin panels • Loss of strength • Thermal and moisture cycles • University Library, Göttingen, Germany
Deterioration of cladding • Bowing and distortion of marble cladding • Large, thin panels • Loss of strength • Thermal and moisture cycles • Finlandia Hall Helsinki • Amoco Tower Chicago
Different uses of stone in construction - Flooring and Paving
A few pointers • Select the stone with care • Establish what performance requirements of the project • Recent test results • Assurance that the material is consistent • Extra tests if needed • Workmanship • A good contractor • Sorting • Laying • Any questions?
Some conclusions Performance Life time Realism