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Aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, crushed stone. As with other types of aggregates, it is a component of composite materials, particularly concrete and asphalt. Aggregates are the most mined materials in the world,[1][2] being a significant part of 6 billion tons of concrete produced per year.[3] Aggregate serves as reinforcement to add strength to the resulting material. Due to the relatively high hydraulic conductivity as compared to most soil types, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under building foundations, roads, and railroads (aggregate base). It has predictable, uniform properties, preventing differential settling under the road or building. Aggregates are also used as a low-cost extender that binds with more expensive cement or asphalt to form concrete. Although most kinds of aggregate require a form of binding agent, there are types of self-binding aggregate which require no form of binding agent.[4] More recently, recycled concrete and geosynthetic materials have also been used as aggregates.
The City of Leeds is a city and metropolitan borough in West Yorkshire, England. The metropolitan borough includes the administrative centre of Leeds and the towns of Farsley, Garforth, Guiseley, Horsforth, Morley, Otley, Pudsey, Rothwell, Wetherby and Yeadon.[4] It has a population of 793,139 (mid-2019 est.), making it technically the second largest city in England by population behind Birmingham, since London is not a single local government entity. It is governed by Leeds City Council.
The current city boundaries were set on 1 April 1974 by the provisions of the Local Government Act 1972, as part a reform of local government in England. The city is a merger of eleven former local government districts; the unitary City and County Borough of Leeds combined with the municipal boroughs of Morley and Pudsey, the urban districts of Aireborough, Garforth, Horsforth, Otley and Rothwell, and parts of the rural districts of Tadcaster, Wharfedale and Wetherby from the West Riding of Yorkshire.
For its first 12 years the city had a two-tier system of local government; Leeds City Council shared power with West Yorkshire County Council. Since the Local Government Act 1985 Leeds City Council has effectively been a unitary authority, serving as the sole executive, deliberative and legislative body responsible for local policy, setting council tax, and allocating budget in the city, and is a member of the Leeds City Region Partnership. The City of Leeds is divided into 31 civil parishes and a single unparished area.
