Concrete mix formula
Concrete is a binding material that is in a pourable form. It is a mixture of cement, water, sand, and gravel that later hardens into a super-strong binder. The hardening is caused by a chemical reaction between water and the cement due to which the concrete grows stronger. It is one of those materials that are used by humans at a huge rate.
The high strength and durability of concrete depend upon the proportion of the material mix, the properties of the ingredients, the compaction method, and controls during placing, compaction, and curing. Concrete is more economical than steel and possesses high compressive strength. It is also a non-corrosive material that can be made by using locally available items. The concrete mix formula can only be achieved if the materials required are properly obtained and mixed to give the desired result.
Ingredients required to obtain concrete mix formula
Cement
Cement is an adhesive. The principal ingredient in cement is calcium oxide. It also consists of iron, aluminum, silicon, and other secondary ingredients. Cement is considered to be the bonding item that holds the concrete mix together once it cures. Although cement is very hard, its strength cannot be compared to that of rock and sand. It is also to be kept in mind that more cement used does not mean greater compressive strength, it actually means better adhesion.
Sand
Sand is an element that has a high compressive strength in the concrete mix. It is not only considered as the filling element, but it also helps eliminate spaces or air pockets between the individual crushed rocks.
Aggregate
Aggregate is the element that provides compressive structural integrity to the concrete mix. It is a layer of washed and crushed rock. The aggregates and sand give their support to the concrete when it becomes compressed.
Water
A chemical change occurs in the quicklime of cement that helps it to stick to the rock and sand. That chemical change happens with the addition of water. The mixing, forming, and finishing of concrete can be done only with the use of water.
Concrete Mix Formula
The best concrete is four-two-one (4:2:1), which means, four parts aggregates, two parts sand, and one part cement. Hence, the mix has seven parts. When the concrete is mixed, the four-two-one ratio can be mixed on different ranges of scales. For example, four shovels of aggregates can be mixed with two shovels of sand and one shovel of cement. This ratio, even though considered to be the best mix, is not suitable for every situation. There are some construction projects that require extreme compressive strength; a mixture of five-two-one (5:2:1) and a half ratio is required. Similarly, in a construction project when high compressive strength is not required, for example, a garden fountain, more sand, and less aggregate are required, hence, the mix ratio turns out to be something like a two-four-one (2:4:1), etc.
The water proportion in a concrete mix formula depends on the humidity, the air temperature, the amount of direct sunlight, and the concrete mix ratio. Generally, the least necessary amount of water is to be used as that helps in creating the best adhesion. But then again, there are structures where workability is the top priority than structural integrity and water is the main ingredient to achieve workability.
