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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]
A power screed being used to flatten concrete. A power concrete screed is a tool used to smooth and level freshly poured concrete surfaces. It can be used in place of a man-powered screed bar to strike off excess concrete. A power screed works by consolidating and/or vibrating the wet concrete mixture.
Admixtures can be used to reduce water requirements, entrain air into a mixture, to improve surface durability, or even superplasticise concrete to make it self-levelling, as self-consolidating concrete, [14] the use of admixtures requires precision in dosing and mix design, which is more difficult without the dosing/measuring equipment and ...
0.75 m³ (1 cubic yard) cart-away mixing trailer. A variant of standard concrete transportation is the concrete (or, cement) mixing trailer. These small versions of transit-mix trucks are used to supply short loads of concrete. They have a concrete mixing drum with a capacity of between 0.76 and 1.34 cubic metres (1 and 1.75 cu yd).
The durability design of reinforced concrete structures has been recently introduced in national and international regulations. It is required that structures are designed to preserve their characteristics during the service life, avoiding premature failure and the need of extraordinary maintenance and restoration works.
Cubic or cylindrical samples of concrete are tested under a compression testing machine to measure this value. Test requirements vary by country based on their differing design codes. Use of a Compressometer is common. As per Indian codes, compressive strength of concrete is defined as: Field cured concrete in cubic steel molds (Greece)
Mix and Giacomin derive comparable equations for all 12 scales that are standardized by ASTM D2240. [ 8 ] Another relation, that fits the experimental data slightly better, is [ 9 ] S = 100 erf ( 3.186 × 10 − 4 E 1 / 2 ) , {\displaystyle S=100\operatorname {erf} (3.186\times 10^{-4}~E^{1/2}),} where erf {\displaystyle \operatorname {erf ...
Air entrainment in concrete is the intentional creation of tiny air bubbles in a batch by adding an air entraining agent during mixing. A form of surfactant (a surface-active substance that in the instance reduces the surface tension between water and solids) it allows bubbles of a desired size to form.