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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]
Accelerated curing techniques invariably involve high temperatures. This may induce thermal stresses in the concrete. Further, the water in the pores starts to exert pressure at higher temperatures. The combined effect of the pore pressure and thermal stresses causes a tensile stress within the body of the concrete. If the accelerated curing ...
The American Concrete Institute (ACI, formerly National Association of Cement Users or NACU) is a non-profit technical society and standards developing organization. ACI was founded in January 1905 during a convention in Indianapolis. [1] [2] The Institute's headquarters are currently located in Farmington Hills, Michigan, USA. ACI's mission is ...
Mass concrete is defined by American Concrete Institute Committee 207 as "any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from the hydration of cement and attendant volume change to minimize cracking."
The contribution of the muscle to the specific heat of the body is approximately 47%, and the contribution of the fat and skin is approximately 24%. The specific heat of tissues range from ~0.7 kJ · kg−1 · °C−1 for tooth (enamel) to 4.2 kJ · kg−1 · °C−1 for eye (sclera). [13]
The American Concrete Institute (ACI) definition of cold weather placement, ACI 306, [128] is: A period when for more than three successive days the average daily air temperature drops below 40 °F (~ 4.5 °C), and; Temperature stays below 50 °F (10 °C) for more than one-half of any 24-hour period.
A cement accelerator is an admixture for the use in concrete, mortar, rendering or screeds. The addition of an accelerator speeds the setting time and thus cure time starts earlier. [ 1 ] This allows concrete to be placed in winter with reduced risk of frost damage. [ 2 ]
ASTM C1293: "Test Method for Concrete Aggregates by Determination of Length Change of Concrete Due to Alkali-Silica Reaction". It is a long-term confirmation test (1 or 2 years) at 38 °C in a water-saturated moist atmosphere (inside a thermostated oven) with concrete prisms containing the aggregates to be characterised mixed with a high-alkali ...