Concrete construction cost is one of the crucial and major components of total cost of a project. It greatly influences the total cost, so it is required to be estimated accurately. There are several parameters that influence the cost of concrete construction for instance grade of concrete, cost of materials like formworks, reinforcement steel, labors, finishing etc.
The cost of these parameters are not constant but rather vary from one location to another one, in addition to the material quality which also affect concrete construction cost.
Moreover, if concrete construction cost is overestimated, it leads to overestimation in the total project cost and the owner would have to spend more money, or he/she probably makes a decision not to proceed with the project.
However, if construction costs are underestimated, there would be several unexpected expenses during the construction stage. These costs affect the contractor, the owner, or both, in addition to substantial loses. Therefore, it is considerably important to have adequate information about different variables and item of concrete construction cost.
Costs for specific items of concrete construction varies from one location to another one. There are many variables that need to be considered which are being discussed below:
Grade of Concrete
Surface Preparation Cost
Cost of Formwork
Cost of Reinforcing Materials
Finishing Work Cost
Cost of Hiring Engineers
1. Grade of Concrete
The most important item to consider is the cost of concrete whether it is ready mix concrete or onsite mix concrete. Commonly, concrete supplier gives the cost of concrete after the project specifications and the job location are provided. The cost of concrete is priced per cubic meter.
It should be known that, the price of concrete increases with the increase of concrete grade. According to Allied ready mix concrete price list, Grade 25 concrete price in Canada range from 182 to 200$ per cubic meter whereas Grade 35 concrete price range from 202 to 217$. The distance between project site and concrete plant would influence concrete construction cost. As the distance increase the cost would rise.
Fig. 1: Onsite Concrete Mixer
2. Surface Preparation Cost
If concrete is poured over nearly leveled soil surface, then the ground should be prepared for concrete placement. This involves cost of grading, compaction, excavation, trenching, and other components. special work is needed to prepare the site.
In contrary, when concrete is placed on a surface which is not leveled. Then the cost of surface preparation would be greater than previous case. It includes excavation and filling with suitable material or removing a soft soil.
If filling process is needed, then the distance between the project and the borrowing material source affect preparation cost.
Fig. 2: Surface preparation
3. Cost of Formwork
Cost of formwork make up fairly large quantity of the entire cost of concrete construction. There are certain details which should be known so as to be able to estimate cost of formwork.
For instance, cost of type of formwork employed, how the it is fixed, and whether the form is rental or bought, the use of crane is needed or not, machines used to transport formwork materials, re-using formwork material, and repair of forms after multiple utilization. Commonly, the cost of formwork is priced and expressed in square meter of the concrete area. Added to that, the cost of working hours of labors shall be included. The cost of labor who fix formwork ranges from 180 to 215$ per 2.6h in the United States.
Fig. 3: Fixing Formwork
4. Cost of Reinforcing Materials
There are various types of reinforcements which are used to reinforce concrete. For example, steel bars, wire mesh, fiber reinforced polymer (FRP) bars, plastic mesh, and fiber added to concrete mixer to improve strength and crack resistance.
The cost of reinforcing materials would vary based on the material type and size of reinforcement. for example, the cost of FRP bars are higher than steel reinforcement and larger diameter bars are costlier than small ones. Lastly, cost of reinforcement installation is one of the major components of material cost. In 2017, the price of reinforcing steel was 619$ in the United States.
5. Concreting Cost
It begins after formwork is fixed and reinforcements are installed. The technique used for concrete placement and equipment used for placement, spreading, and compacting concrete affect concrete costing, in addition to labor costs. Concrete may be ready mix and pumped to the specified locations or mixed onsite and require other machinery to deliver fresh concrete to its final position.
6. Finishing Work Cost
The type of finishing and its complexity determined in the design controls the cos of finishing operations. Concrete could be finished in number of different ways for example smooth surface, exposed aggregate surface, or stamped concrete finish.
Certain surfaces may require only a strike-off and screed to proper contour and elevation, while other surfaces, a broomed, floated, or troweled finish may be specified. Finally, the cost of any curing compound or testing services is also included in finish work cost.
Fig. 4:Finishing Concrete Surface
7. Cost of Hiring Engineers
Frequently, it is required to hire an engineer to supervise the project and make sure that the work is done in accordance with applicable codes and specifications. So, the cost of services provided by the engineer should be taken into considerations.
8. Contingency Cost
Obviously, no construction work is totally accurate and there is no guarantee for stoppage of concreting due to technical problems or natural events like rain. This needs to be accounted for in the total cost of concrete construction and allocate certain quantity of money for contingency works. This amount is commonly specified by experienced estimator based on their experience.