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A w/c ratio higher than 0.60 is not acceptable as fresh concrete becomes "soup" [2] and leads to a higher porosity and to very poor quality hardened concrete as publicly stated by Prof. Gustave Magnel (1889-1955, Ghent University, Belgium) during an official address to American building contractors at the occasion of one of his visits in the ...
[citation needed] In the concrete and petroleum industry, however, a bag of cement is defined as 94 lb (43 kg) because it has an apparent volume close to 1 cubic foot (28 litres). [61] When ready-mix concrete is specified, a "bag mix" unit is used as if the batching company mixes 5 literal bags of cement per cubic yard (or cubic metre) when a ...
The Oxford English Dictionary has a definition of "bag" as "A measure of quantity for produce, varying according to the nature of the commodity" and has quotations illustrating its use for hops in 1679, almonds in 1728 (where it is defined by weight as "about 3 Hundred Weight" i.e. 336 pounds (152 kg) in Imperial units) and potatoes in 1845 ...
The most common use for portland cement is in the production of concrete. [17] Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element.
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Regular concrete can typically withstand a pressure from about 10 MPa (1450 psi) to 40 MPa (5800 psi), with lighter duty uses such as blinding concrete having a much lower MPa rating than structural concrete. Many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water. [citation needed]
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Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. The density of concrete varies, but is around 2,400 kilograms per cubic metre (150 lb/cu ft). [1]