In order to perform rate analysis for reinforced concrete, two steps are involved:
1- Estimation of number of labour and equipment, quantity of materials, miscellaneous items required for for a certain quantity of reinforced concrete.
2- Determination of structural element for which the rate analysis is needed. This is because the amount of RFT varies for slabs, beams, columns, or foundation. Noting that the quantity of other materials like cement and aggregate are the same for the same mixture design. Regarding labour, the rates for RFT work might change for different structural elements as the amount of reinforcement steel changes. The quantity of materials like cement, sand and coarse aggregates change according to the mix design, for example, M15 (1:2:4), M20 (1:1.5:3), M25, M30 and so on
Next, the rate analysis for 1 m3 of reinforced concrete is to be calculated.
Step 1: Estimation of Materials:
1) No. of Cement Bags:
Volume of cement required for 1 m3 of concrete = [1 x 1.54] / [1 + 1.5 + 3] =0.28 m3
Number of bags of cement = Volume of cement required for 1 m3 of concrete / (volume of one bag of cement = 0.0347 m3) = 0.28 / 0.0347 = 8.07 bags.
2) Volume of Sand:
The types of structure component will determine the quantity of steel required as mentioned before.
Two approaches can be used to calculate the amount of steel required:
(a) Using the structural drawings, the total weight of steel required divided by total volume of concrete for different components can be calculated. This gives the weight of reinforcement per cubic meter of concrete.
(b) Approximate method by assuming the percentage of reinforcement as the following guide. These values can change for different structures and previous experiences.
- For slabs = 1.0 % of concrete volume.
- For Beam = 2 % concrete volume.
- For column = 2.5 % of concrete volume.
Assuming reinforcement required is 2.5%, weight of steel= [2.5 / [100 x 1] x 7850] = 196.25 kg.
Step 2: Labour and Equipement Requirement for 1 m3 of reinforced concrete
Labours are given as the number required for certain days to complete a certain job:
- Mason: One mason is required for 0.37 days.
- Labour: One Unskilled labour is required for 3.5 days.
- Water carrier: One water carrier required for 1.39 days.
- Bar Bender: Consider one bar bender required for 100 kg of steel as for 1 day.
- Mixer Operator: One mixer operator required for 0.0714 days.
- Vibrator Operator: One vibrator operator required for 0.0714 days.
Equipment and other charges can be assumed as a percentage of total material and Labour cost. Assume it as 7%.