Concrete Cube Casting



 

                     
                      By hand the concrete cube should be filled by 3 layers 35 tampings on each layer by rod 16 mm dia The no of tampings are between 100 – 105 while preparing the concrete cube the no of tampings divides the no of layers
                      For eg cube is casted in 3 layers  ( 150 mm cubes )
                      105/3                 =                     35 nos of tampings
                      If cube is to be casted in 4 layers then ( 100 mm cubes )
                      100/4                 =                      25 nos of tampings
However the total no of tampings should be between 100 – 105 nos
                      Loading on the cube on strength machine should be 14/N/mm2 / per min

Rate of loading of concrete cube
Loading should be applied @ 14/N/mm2/min
                                           Or 140 kg / cm2/min       
140*15*15/101*60               =          5.198 KN/sec
                     
Note: to convert 140 kg to KN
                                              =          140/101
Area of cube               =          15 cm * 15cm
Minutes                                  =          60 min
IS 516
                   There should be a variation of +- 15 % from the average of the three cubes to each individual readings/ strength
Eg
                     Strength of 3 cubes
                     40 N / mm2
                     45 N / mm2
                     50 N / mm2
                           --------------------
                     45 N / mm2                                So 45*0.15      =          6.75

So 45+6.75    =            51.75

&  45-6.75     =            38.25
So readings should lie between  38.25 to 51.75 N/mm2

Decent value : the per unit weight of the concrete
                      Eg  for concrete PCC 2400 kg/m3
                            For concrete RCC 2500 kg /m3

Sounding     : the measurement of the pile depth measured by the chain other wise it can be checked by ordinary methods liks tie a stone with rope

The small mixture is called Gamjon mixture

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