China
Africa
Explore chapters and articles related to this topic
Durability and service life assessment
Published in James Douglas, Bill Ransom, Understanding Building Failures, 2013
Any deterioration through pollution, salts and frost is likely to be enhanced if sedimentary stones are laid so that the natural bed lies parallel to the vertical face of the wall. This is known as face bedding and should be avoided. The greatest durability is achieved when the natural bedding plane lies parallel to the horizontal courses in a wall. Metamorphic rocks are derived from sedimentary rocks through the action upon them of great heat and pressure arising from movements of the Earth’s crust. The structure of the rock is then changed radically. The only metamorphic rocks of significance for building purposes in the UK are marble (derived from limestone) and slate (derived from clays). Marble is used for cladding and is very durable: it is not immune from attack by sulphur gases but this is rare in reality. Slates are used for roofing, for cladding and as DPCs. Roofing slates are exposed to the most severe conditions and can be affected by sulphur gases. Those slates conforming to BS 680, however, are highly resistant to attack. The Standard includes a sulphuric acid immersion test which is intended to simulate, but accelerate, the attack by sulphur gases dissolved in rainwater on any calcium carbonate present in slates. One major cause of damage to all stones can arise if the fixings embedded in them corrode. In the past, the rusting of iron and steel cramps and dowels has caused extensive damage, particularly to limestones and sandstones. Appropriate metals to use are stated in BS 5390.
Stone and cast stone
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Slate is derived from fine-grained sand-free clay sediments. The characteristic cleavage planes of slate were produced when the clay was metamorphosed, and frequently they do not relate to the original bedding planes. Slate can be split into thin sections (typically 4–10 mm for roofing slates), giving a natural riven finish, or it may be sawn, sanded, fine-rubbed, honed, polished, flame-textured or bush-hammered. A range of distinctive colours is available: blue/grey, silver grey and green from the Lake District; blue, green, grey and plum red from North Wales; and grey from Cornwall. Slate is also imported from Ireland (grey/green), Canada (blue/grey), France (blue/grey), India (blue/grey), China (blue/green/grey), Brazil (grey/green/plum), and Spain (blue/black), which is the world’s largest producer of the material. Slate is strong, acid- and frost-resistant, lasting up to 400 years as a roofing material. The minimum recommended pitch for slate roofing is 20° under sheltered or moderate exposure and 22.5° under severe exposure, and these situations require the use of the longest slates (460, 560 or 610 mm). However, if rubber seals are incorporated between each slate, a minimum pitch of 12° can be achieved. Where thick slates (up to 20 mm in thickness) are used for a roof pitch of less than 25°, it should be noted that the slates lie at a significantly lower pitch than the rafters. Fixing nails should be of copper or aluminium. Slate is also used for flooring, cladding, copings, cills and stair treads. When used as a cladding material, it should be fixed with non-ferrous fixings or cast directly onto concrete cladding units.
Exterior Enclosure Components
Published in Kathleen Hess-Kosa, Building Materials, 2017
Slate is a shale rock formed from compressed sediment that over time become thin, flat, layered clay-like stone. Shales are highly variable in content, mostly a mix of clay, quartz, calcite, and other minerals. Some of the other minerals may lend color to the shale. Mostly a dark gray, shales with carbon compounds are black. Shales with ferric oxide are red. Shales with iron hydroxide are brown. Shales with metal silicates minerals are green. Of all the various components of shale (or slate), quartz contains amorphous and crystalline silica.
Processing of electric ceramic insulators from slate rocks and MgO
Published in Materials and Manufacturing Processes, 2020
S. M. Naga, M. Sayed, M. M. El-Omla, Ahmed R. Wassel, N. El-Mehalawy
In the current study, ceramic bodies enriched with cordierite were fabricated using naturally occurring slate rocks. Slate is tenderized metamorphic rock with a moderately high degree of schistosity. Its color ranges between green, gray and red. Its mineral constituents are rearranged based on the type of stress applied to the rock. The minerals can be squeezed, stretched and rotated to align in a given direction. Slate is mainly composed of alumina and silica, and it is a soft rock that can be crushed to produce an extremely fine powder. It is composed of calcite, quartz, muscovite, talc, albite and chlorite. Slate rock possesses an abundance of fine-grained sheet-like silicates, giving the rock a greasy feel and discriminatory cleavage, which causes the rocks to facilely break into slender sheets.[22,23] Slate is a material of great geological multitude that is present in the Eastern Desert and the Sinai Peninsula. It is a cheap material serviceable for application in the ceramic industries. The present study aims to determine the usability of slate rock as a cheap local starting aluminum silicate material for the production of ceramic bodies enriched with cordierite. The effect of partially replacing slate with MgO on the physical, microstructure, mechanical properties, thermal expansion coefficient and dielectric behavior of the fabricated sintered bodies employed as electrical insulators was evaluated.
Experimental investigations on the elastic parameters and uniaxial compressive strength of slate under freeze–thaw cycles
Published in Geomechanics and Geoengineering, 2019
Helin Fu, Jiabing Zhang, Zhen Huang, Yue Shi, Jing Wang
Often characterised by stratification, slate has the same physical and mechanical properties in the isotropic plane but varying properties in the vertical direction (Chen et al. 2016, Mokhtari et al. 2016); therefore, slate is usually referred to as a transverse isotropic body. A series of experimental studies on the elastic parameters and compressive strength of transverse isotropic rock have been conducted. In one study, the elastic modulus (E and E′), Poisson’s ratio (μ and μ′) and shear modulus (G′) were determined through a series of uniaxial compression tests, and the interrelation between the mechanical parameters and the bedding angle was determined (Amadei 1996). Later, a method based on complex function theory and the Brazilian splitting test was introduced to determine the elastic parameters, and the thermodynamic constraints of the elastic parameters were given (Chen et al. 1998). Several experimental studies concluded that the compressive strength with distribution of the bedding angle mainly falls into three categories: U type, undulatory type and shoulder type (Tien and Kuo 2001). Therefore, the bedding angle has a very significant effect on the elastic parameters and compressive strength for transverse isotropic rock. In addition, the influence of freeze–thaw cycles on transverse isotropic rock must be considered in cold regions.