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A cement bag contains the most necessary component in mixing concrete. Cement is made from grinding together calcined limestone and clay to form a fine powder. It is then used to bind together water and aggregate to form concrete. You can purchase a cement bag at any do-it-yourself store.
A standard cement bag sold at a home supply store weighs between 50 to 80 lbs (22.5 to 36 kg). Cement is packaged and labeled according to bag mix. This refers to how many bags of cement it will take to make 1 cubic yard (0.764 cubic meters) of concrete. A 5 bag mix means that it will take 5 bags to make one cubic yard (0.764 cubic meters) of concrete.
Cement works through chemical reactions between the limestone and the clay. When mixed together with water and aggregate, bonds form on a molecular level These bonds are what gives cement a high level of strength and durability.
Concrete is made by mixing together cement, water and aggregate, which is a mixture of sand and gravel. The standard ratio for mixing concrete is 1 part cement, 2 parts sand, and 3 parts gravel. Slowly add the water to the mixture while stirring until it reaches the desired plasticity. This is usually determined by performing the slump test. Fill a slump cone with the concrete mixture and slowly lift it up to verify that it slumps between 3 to 4 inches (7.62 to 10.16 cm).
When not in use, the cement bag should be stored properly to prevent it from getting wet. As soon as moisture enters the cement bag, the chemical bonding begins, making it useless for mixing concrete. There are a few different ways in which to store your bags of cement.
The best way to store cement bags is in the garage or shed. Even unopened bags should stay out of the elements to prevent them from being ruined. Place them in the far back of the garage or shed, away from doors and windows. Bags of opened cement should be double wrapped in trash bags. Wrap each end of the cement bag and seal it in the middle with duct tape. Store the bag in a dry area.
Multiple bags of cement can be stored on a pallet to prevent humidity and rain water from forming under and between them. If possible, store the pallet in a shed or garage. If that isn't practical, cover them with a tarp that is secured to the pallet. You can ]hold the tarp down with concrete blocks to prevent rain and dew from forming underneath. The key is to keep the cement dry to prevent the chemical bonds from forming and rendering it useless.
I have been storing my bags of cement in my garage for awhile now. I just picked the bags up and many of them feel hard. I'm hoping the chemical bonds haven't occurred. I didn't think the garage had much moisture.