Concrete work in a project usually holds the maximum in terms of overall cost and work quantity. It becomes an important step to calculate the concrete related costs while preparing a project estimate. The cost of concrete making depends upon the cost of materials, mix design, workforce, and machinery.
In this, we calculate the cost of 1 cubic meter of concrete and other expenses that occur in the preparations of concrete.
Factors affecting the Cost of Concrete work:
1. Material Costs:
Costs of materials and supplies and the associated transportation charges affect the cost of any concrete construction project.
2. Labor Rates:
The local market labor wages or rate per day specified by the state affect the expenditure of a project.
3. Site Conditions:
The site condition and location of construction affect the cost of the project and concrete. Low and poor soil quality, wetlands, contamination, utility, environmental and traffic issues are few examples in this category.
If the project duration is too short for the type of work and activities involved, then project costs will be on the higher side. This is true for projects with a significant liquidated damage clause in their contracts.
As accidental amount contingency fund of about 10 % of the total expenditure is generally set aside by contractors to cover unforeseen costs. However, market changes and scarcity of materials and supplies might require a higher contingency of the range of 15-20%.
Cost of concrete for 1m3 of volume:
Let’s consider the concrete mix of M 20 (1:1.5:3), where, 1 is the part of cement, 1.5 is the part of fine aggregates and 3 is the part of coarse aggregates having size of 20mm. The water-cement ratio adopted for mixing of concrete is 0.45.
1. Cement = 1500 kg/m3
2. Sand = 1700 kg/m3
3. Coarse aggregates = 1650 kg/m3
2. Calculation of Materials for
Dry volume = Wet Volume X 1.52
Volume of Cement = (Dry volume X Cement ratio)/ Sum of ratio
Volume of Cement = (1 X 1.52)/(1+1.5+3)
= 1. 52/5.5
Weight of the cement = 0.28 X 1500
= 420 kg.
Volume of Sand = (1.5 X 1.54)/(1+1.5+3)
Weight of the Sand = 0.42 X 1700
= 714 kg.
Volume of Course Aggregate= (3 X 1.54)/(1+1.5+3)
Mass of the Course Aggregate = 0.84 X 1650
= 1386 kg.
3. Cost Calculation
Cost of cement for 1 m3 =
No of Bags = 420/50
As per present market rate, cost of 1 bag of cement is taken as Rs: 450
= 8.4 X 450
= 4200 Rs
Cost of sand for 1 m3 =
As per present market rate, cost of 1 m3 of sand is taken as Rs: 1400
= 0.42 X 1400
= 588 Rs
Cost of course aggregate for 1 m3 =
As per present market rate, cost of 1m3 of course aggregate is taken as Rs.2400
= 0.84 X 2400
= 2016 Rs
Therefore, total cost for 1m3 of M – 20 concrete is
=Cost of cement + sand + course aggregate
= 4200 + 588 + 2016
Say Rs 6400
Additional Cost of Concrete:
The above estimated cost is just for the raw materials of concrete. The complete cost of concreting work also includes the cost of mixing, transporting, compaction equipment, reinforcement, formwork and labour charges
The cost of transportation of materials into the mixer and the mixer charges are added to the concrete.
The properly mixed concrete is to transported to the concreting location with the help of machines and labours. If ready mix concrete is used then its cost is inclusive of transportation cost.
The machinery like vibration use for compaction of Concerte and other tools are also added up to the total cost of concreting.
For reinforced concrete work, the cost of steel and labour charges for the cutting and tieing of rebars is also calculated and added to the concrete works.
5. FormWork or Shuttering
Concreting work in beam, columns or slab, the formwork required to hold the concrete is also added.
6. Skilled Labour
The Labour force required to mix, transport, place, compact and finish the concrete is added to the concreting work cost.