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