The difference between voids and pores may be noted. The pores represent opening within individual particles. The process of consolidation of concrete can be carried out eir by hand or by means of vibrators.

The contraction joints are installed to allow for shrinkage movement in structure. It may eir be a complete contraction joint or a partial construction joint. In former case, re is complete discontinuity of both concrete and steel.

According to Electrolytic ory or Electrochemical corrosion, corrosion takes place due to chemical action in combination with electrolysis. It takes place at or near room temperature when metal comes into contact with moisture in contact with aqueous solution of salt, acid or bases.

The depth within which corrosion can occur under suitable conditions, is nearly twice than that of normal concrete. Hence special care will have to taken to overcome sufficient problems.

At time of placing, temperature of concrete should be between 15� Celsius to 25� Celsius and it should not be allowed to come into contact with water having a temperature of 35� Celsius.

In Chemical Action ory or Direct corrosion, corrosion produced by means of chemical attack and it includes oxidation in which oxygen of atmosphere combines with all or a part of surface of material.

In Maximum void method, a box is filled with varying proportions of fine and coarse aggregate. The proportion which give heaviest weight is n adopted. The method of maximum density is not very popular because grades cannot be accurately achieved.

The increase in volume of sand is due to fact that moisture causes film of water around sand particles and it results in increase of volume of sand. For moisture content of about 5% to 8%, this increase of volume may be as much as 20% to 40%, depending upon grading of sand.

The pipe extends from level of working platform to lowest point where concrete is to be deposited. The bottom of Tremie is provided with concrete block which is forced out when concrete starts.

The water lubricates aggregate and it facilitates passage of cement with voids of aggregates. This mean that water makes concrete workable.