CEMENT CONCRETE ROAD  :

WHAT IS CONCRETE
Concrete is the product of mixing, aggregate, cement and water.
The setting of concrete is a chemical reaction between the cement and the water, not a drying process
This reaction is called hydration, it evolves heat as does any chemical reaction, and the process is irreversible.
There is an initial set when the concrete will cease to be liquid but have little strength (e.g. 6 to 24hrs. old), thereafter the concrete will gradually gain strength over time until it achieves the strength required.
Differing mix proportions and cement types will achieve required strengths in differing time spans.

CONSTITUENTS OF CONCRETE
Cement, Aggregate and Water, (and sometimes additives).
Aggregate
Aggregates are usually distinguished between fine and coarse aggregate.
Aggregates are classed as inert materials, such as washed natural sand (fine); and natural gravel, which can be crushed to produce the appropriate size and grading of aggregate, and similarly crushed, quarried stone (coarse).
The aggregate must have a minimum inherent strength requirement for structural concrete, the coarse aggregate must not be weaker than the concrete paste.
All aggregate must be "clean", i.e. not contaminated with organic matter or clay/silty soils and overburden during extraction and storage.
Cement
Basically a material made by heating limestone and a suitable clay to produce a clinker rich in calcium silicates.
This clinker is ground to produce a fine powder, this is cement. By using different clinkers, grinding them to differing degrees of fineness and the use of additives many different types of cement are produced with varied properties in their use, e.g. rapid hardening cement, sulphate resisting cement, etc..
Generally speaking the more cement in a mix the stronger more durable the concrete produced will be, but this does have to be related to other factors, primarily the amount of water used in the mix, i.e. water/cement ratio.
Water
Water is an extremely important part of concrete, and drinking quality water is usually required, or water from an approved source free from impurities.
Additives
The most commonly used additive is a "foaming" agent to produce air entrained concrete, mainly for carriageway concrete, but also other exposed situations.

Another common use of an additive is to increase the workability of concrete without adding extra water and thus increasing the water/cement ratio and decreasing the strength of the concrete.