What are recommended mix proportions for good concrete?
Good concrete can be obtained by using a wide variety of mix proportions if proper mix design procedures are used. A good general rule to use is the rule of 6’s: • A minimum cement content of 6 bags per cubic yard of concrete, -A maximum water content of 6 gallons per bag of cement, • A curing period (keeping concrete moist) a minimum of 6 days, and • An air content of 6 percent (if concrete will be subject to freezing and thawing). Why does concrete crack? Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage. Why test concrete? Concrete is tested to ensure that the material that was specified and bought
Good concrete can be obtained by using a wide variety of mix proportions if proper mix design procedures are used. A good general rule to use is the rule of 6’s: A minimum cement content of 6 bags per cubic yard of concrete, A maximum water content of 6 gallons per bag of cement, A curing period (keeping concrete moist) a minimum of 6 days, and An air content of 6 percent (if concrete will be subject to freezing and thawing).
Good concrete can be obtained by using a wide variety of mix proportions if proper mix design procedures are used. A good general rule to use is the rule of 6’s: • A minimum cement content of 6 bags per cubic yard of concrete, • A maximum water content of 6 gallons per bag of cement, • A curing period (keeping concrete moist) a minimum of 6 days, and • An air content of 6 percent (if concrete will be subject to freezing and thawing). Question and answer courtesy of Portland Cement Association (PCA). More information is available at: http://www.cement.org/tech/cct_faqs.asp.
