TEST FOR GOOD CONCRETE IS NECESSARY TO CHECK THE ACCURACY OF THE CEMENT CONCRETE LAID IN THE FOUNDATION.

The width of foundation should be determined by the bearing capacity of the soil and the resistance of concrete to tensional and the shear stresses is low , therefore the projection of the concrete laid over the width of the foundation beyond the wall (or offsets) ,must be so limited and the depth must be sufficiently great,as to prevent the cantilever action and to give the maximum shearing area . Crushing tests on cubes of the concrete show that the plane of the greatest shear occurs at an angle of 45 degree .It is considered usually sufficient to fix the depth of the concrete by drawings line at forty five degree from the base of the wall to intersect the side of the concrete bed .Projection of the concrete beyond the offset should be not less than 15 cm on either side since the edges are not generally well consolidated,and it's thickness should be not less than its projection beyond the offset and in no case less than 15 cm . Minimum size for 1:3:6 Cement Concrete wall foundation should be twice the thickness of the wall plus 30 cm for the width and is considered thumb rule for ordinary buildings .In case of mass concrete foundation in the good ground stressed in direct compression should not be lesser than 1:4:8 .The tension in the concrete is permitted up to 4.2 kg /sq cm so in the weak ground the concrete should not be lesser than 1:3:6 .Test for good concrete is necessary for which two days after ramming is completed a hole is made in the concrete and filled with water .If the water stays in the hole the concrete is good and if the water runs through it the concrete is either not properly rammed or insufficient mortar has been used .