EXAMPLE 2.4.2. VOLUME METHOD: ESTIMATING CONCRETE FOR FOOTINGS

Estimate the quantity of concrete components for four 1.2m-square footings (depth of 0.40m) to be used for a small structure.

Start with taking the volume of the footings.

                   
                   

The typical design mix for footings is Class A (1:2:4):

• For cement:

             Using 40kg bag:  
                  Using 50kg bag:  

• For sand:

              

                   Consider sand bulking:

                   

• For gravel:

       For footings or any part of the structure that comes in contact with the soil, additional quantity of gravel is required for bedding. Gravel bedding ranges from 30mm to 75mm.

       Assume 50mm (2 inches) bedding:

       

                    

                    

          So, volume for gravel bedding is:

                   


         Estimate gravel needed for the footing:
               
                    

         Taking the total of gravel needed:

               


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