China
Africa
Explore chapters and articles related to this topic
Roofings
Published in Michael McEvoy, External Components, 2014
Natural slates Natural roofing slate, a dense fine-grained metamorphic rock, is obtained from the rock beds of Wales, north Lancashire, Westmorland and Cornwall and imported, particularly from Spain, France, Portugal and South America. Slates should comply with BS 680 Roofing slates Part 2: 1971 Metric units which describes those from the Cambrian, Ordovician, Silurian, Devonian, and Dalradian formations, and describes characteristics, standard designations, thickness gradings, marketing descriptions, testing procedure for atmospheric conditions, lengths and widths. MBS: Materialschapter 4 gives specific information regarding metamorphic stone under which slate is categorized; it is formed by immense earth pressures acting upon clay which results in planes of cleavage. Roofing slates are manufactured by splitting along these planes; the resulting surface may not be perfectly flat. Good slate, such as that complying with BS 680, provides a most durable roofing material; poor slate may begin to decay in a few months, especially in damp conditions in industrial areas. Imported slates have proved to be of excellent quality but, before fixing, all slates should be inspected for consistency in size and shape and colour (particularly since imported slates tend to come from more than one quarry). Care should be taken if using a material which is not native to the UK climate and BS 680 tests should be carried out, although they do not establish the ultimate quality of the material they do indicate a minimum standard. Included are two tests that all slates should pass — a water absorption test, and a wetting and drying test. Slates to be used in polluted areas should pass a further test involving immersion in sulphuric acid (this was introduced in the 1940s and is less generally applicable now given the intervening improvements in air quality). British slate has a fine well-compressed grain that enables slates to be of consistent thickness and have an expected life of up to 400 years in the UK. Although continental slates have considerable durability they may not last as well in the climate of this country.
Mineral extraction from asbestos-containing waste (ACW) and changes in its morphology during treatment with ammonium salts
Published in Journal of the Air & Waste Management Association, 2023
Sangwon Park, Yeon-Sik Bong, Gwangmok Kim
For this study, roofing slate waste containing asbestos (raw waste) was collected. Because the samples had been neglected in outside for a long time before collection, It meant that the amount of CaCO3 might have remained on the surface of the sample. Therefore, ammonium salt needed relatively long time to react with magnesium and silicon in the sample. After considering the effect of weathering on the slate samples, the change in the concentration of the positive ions in the raw waste material was measured at intervals of 10, 30, 60, 120, and 360 min.