Basics of Cement concrete.
It get by mixing the following four ingredients in predetermined proportions.
- Gravel and
- First Step – In a Concrete mixer when we mix the above four ingredients .
- Second step – We get the plastic mass of concrete.
- To get a desired shape of concrete we poured the mix into a define shape of a mould.
- The plastic mass poured in Moulds, standing into hard solid mass.
- The chemical reaction of cement, and in the mix, is slow
- Chemical reaction requires time and favorable temperature for its completion.
- This time, known as setting time.
- This Setting time divided into three distinct phases.
The first phase.
- The first phase is known as initial setting time.
- It requires from 30 minutes to about 60 minutes for completion.
- During this phase, the mixed concrete decreases its plasticity
- Mixed concrete develops pronounced resistance to flow.
The second phase
- The second phase, known as final setting time.
- It may vary ·between 5 to 6 hours after the mixing operation and
- During this phase, concrete is soft solid without surface hardness.
The third phase
- The third phase consists of progressive hardening and an increase in strength.
- The process is rapid in the initial stage, until about one month after mixing, at which time the concrete almost attains the major portion of its potential hardness and strength.
properties of concrete
- Properties of concrete depend on the quality and proportions of the ingredients used in the mix
- Concrete has enough strength in compression, and little strength in tension.
- concrete is weak in bending, shear, and torsion.
Uses of Plain concrete
- The use of plain concrete is limited.
- Where great compressive strength and weight are the principal requirements, plain concrete is used. and Where tensile stresses are either absent or are extremely low plain cement concrete is used.
Uses of Reinforced cement concrete
- To use cement concrete for common structures such as beams, slabs,and retaining structures etc. steel bars also may be placed at tensile zones of the structure which may then be concreted. and The steel bars, known as steel reinforcement, are embedded in the concrete take the tensile stresses. therefore The concrete so obtained is termed as reinforced cement concrete commonly abbreviated as R.C.C.