Describe how concrete is made from cement?
when you mix sand gravel with water cement a chemical action starts, the sand gravel are fillers, the cement and water are the chemical bonding agents when the two bond and sets up it becomes concrete and it takes 27 days for it to fully cure
Concrete contains: * Portland Cement - Sintered limestone, clay, and gypsum * Aggregate - filler such as rocks and sand * Additives - often nylon fibers, or chemicals, to affect strength or cure time * Reinforcement - optional, steel cable, wire, mesh, or bars. * Water - which binds the cement molecules chemically * Carbon dioxide - joins in from the air to help form crystals in the mixture. Concrete is made by: * Preparing the mold or form, such as laying boards, flattening soil, stamping a shape into sheet metal, or just digging a round hole. * Laying the reinforcements, such as a grid of textured steel bar, or maybe nothing at all. * Mixing the rest of the ingredients in a hopper large enough to handle the weight * Pouring the mud/slurry into the form * Packing, shoveling, or vibrating to help settle the mud and remove trapped air. Typical concrete may set (harden) in 30 minutes to a few hours. Cure time is longer (maximum strength) and typically takes from a few days to a month. Cure may be incomplete if the cement is allowed to dry out, so it's common to cover concrete with plastic, sealants, sprinklers, or use chemicals mixed in to help retain moisture during the cure. These same procedures happen, whether it's a bag of quick-crete poured into a hole with a mailbox post, or whether it's a million ton footing poured in a single session. A great way to see this in action is to look for road construction, or bridge construction.
Concrete is made from 4 elements: portland cement, sand, aggregate ( rock) and water. The ratio when mixing concrete by hand is one round nosed shovel full of cement, 3 round shovels of sand, 1 shovel of gravel and water to get the consistency of heavy toothpaste. The consistency can be thinner if adding to a form holding the concrete say in a tube buried in the ground to support a deck. You add the dry ingredients and using a hoe, mix until all the ingredients are one uniform color ( no longer sand or cement) which can take 3-5 minutes. Next start by adding a little water and bring the mix to the water with the hoe. Continue doing this until all the dry ingredients are thoroughly mixed and wetted to the consistency you wish. Want to avoid all this: buy premixed bags of Concrete Mix at Home Depot under $4 a bag for small projects. If you are contemplating a larger project you need more information about concrete finishing before ordering a load from a company that mixes it and delivers it to your house for you to spread around.
