Cement is a component of concrete. Cement and water make the "glue" which holds concrete together.
Answers will vary.
cement- reacts with water to form "glue"
water- reacts with cement, the amount also determines strength
aggregate- makes concrete stronger, more durable, and less costly
Cement which is workable is able to be poured into forms without difficulty. A slump test is used to measure workability.
gravel, sand, vermiculite, perlite,
Aggregate makes the concrete stronger and cheaper.
Sugar can be added to the concrete to retard hardening. For example, if the concrete needs to be transported a long distance, then a retarding admixture would be desired.
Calcium chloride solution can be added to speed the hardening of concrete. For example, in cold weather it is desirable to speed up the hardening process and produced higher heat of hydration.
The aggregate would depend upon how the concrete is to be used in the building. Lightweight aggregates like shale are used for insulating properties. However, normal weight aggregate would be required for strength. Availability and economy of aggregate are important, too.
Concrete will most likely crack due to drying shrinkage. The hydration reaction which strengthens concrete will be halted from lack of water resulting in weaker concrete.
A lightweight aggregate would be desirable for building a ship needing to float. However, the boat would be dangerous because of poor tensile properties of concrete. It would have to be reinforced to be safe.
The dormancy period of fresh concrete is the period during which the concrete is in a plastic state and the reaction is very, very slow. This state lasts from 1 to 3 hours and allows contractors to transport concrete to the job site and consolidate it before it hardens. After the dormancy period, the hydration reaction accelerates, and the concrete sets and becomes hard.
A slump test can be performed on freshly mixed concrete to determine its consistency. This is done by pouring it into an inverted cup with the bottom cut out. Once the cup is removed, the concrete is observed. It is desirable that the concrete stay 50-75% of its original height for good workability.
The water to cement ratio determines the strength of concrete. The less water that is used to obtain a workable concrete, the more strength the resulting hardened concrete will have. However, remember that workability is lost if water to cement ratio is too low.
A superplasticizer is an admixture which is used to make concrete more workable with the use of less water. Using a superplasticizer will result in a stronger concrete because less water is used.
Gloves should be worn while mixing concrete because one of the products of the hydration reaction is calcium hydroxide, a base. In fact, upon mixing concrete, the pH rises to 12 which means the solution is strongly basic. This can burn, irritate, and dry out the skin.
Water transports harmful substances that lead to concrete degradation. Water is the central issue in freeze-thaw damage of concrete.