As explained in few articles and blogs previously, concrete is the most important component of grey structure construction of house or building. Concrete is made by mixing cement, sand (fine aggregate) and crush (course aggregate) with a certain ratio of water. Concrete mixing is a very sensitive process for all grades of concrete and the strength of concrete depends upon the workmanship and professionalism during mixing process. Unfortunately due to non availability of locally produced economical construction machinery/equipment and lack of interest by the governments in vocational training of labour, concrete mixing has never been up to the mark on small scale construction sites(residential & commercial). Concrete is mixed manually by hand or small mixing machines are used which too are not locally produced hence every labour contractor can not afford to purchase his own machine. Only option is to get the machine on daily rental basis the reason due to which contractors hire the machine only for slab pouring stages throughout the construction process.
Best recommended method for mixing of concrete is by using a batching plant. Concrete mixed in a batching plant is often termed as READY MIX CONCRETE. This type of concrete is ready to be poured at construction site once it is out of batching plant. A batching plant is a computer guided plant that uses automation process to make sure concrete is mixed perfectly in whatever grade/ratio is required. Batching plants are expensive and requires a decent enough space to be assembled and made operational. It requires staff who has to manage daily based operations. Due to its high capital and operational cost, end product i-e ready mix concrete is expensive as compared to conventional on site concrete mixing. In this article we will explain and calculate in detail the comparison of per cubic feet ready mix concrete cost and conventional concrete cost.
Let us suppose an area of 100 cubic ft & 1:2:4 ratio concrete for calculation
Wet volume of Concrete = 100 cft
Dry volume = Wet volume x 1.54
= 100 x 1.54
= 154 cubic ft
Sum of ratio 1:2:4 = 7
Cement in cubic ft required = 154/7
= 22 cft
Cement in bags required = 22/1.25
= 17.6 bags
Sand in cubic ft required = 22 x 2
= 44 cft
Crush in cubic ft required = 22 x 4
= 88 cft
Water required approx = 450 ltr
Now to calculate cost of concrete, we will use latest market construction material rates as of OCT 2019.
Cement = 540 Rs/bag
Crush sargodha plant = 75 Rs/cft
Sand chenab = 32 Rs/cft
Water = Rs .5/ltr
Cement = 17.6 x 540 = 9504 Rs
Sand = 44 x 32 = 1408 Rs
Crush = 88 x 75 = 6600 Rs
Water = 450 x .5 = 250 Rs
Total = 17762 Rs/100 cft
Per cubic ft cost of concrete = 17762/100 = 177.62 Rs
Now as per the market sources that provide ready mix concrete around Lahore, average rate of 3000 psi 1:2:4 concrete is around 8000 Rs/cubic meter using same material as above as of OCT 2019.
Per cubic meter ready mix concrete cost = 8000 Rs
per cubic ft ready mix concrete cost = 8000/35.3 = 226.66 Rs
It is important to note here that above costs include expenses that are to be incurred in making of concrete only i-e material & labor for mixing only. This estimate does not include pumping cost of concrete. That will remain same in both cases if concrete is poured using local lift and labor system. However ready mix concrete cost will significantly go upwards if mobile concrete pump is used.
As we can see in the table above that ready mix concrete has higher cost as compared to conventional concrete, but this higher cost can save from many other hassles involved in conventional concrete mixing such as:
- On site material dumping/offloading in huge quantities for cement, sand and crush that will require extra space
- water provision non stop
- approximate ratio mixing instead of accurate
- hiring labor and mixing machine for the process
Now there are definitely some cons in ready mix concrete too such as
- Higher per cubic ft cost
- non-availability of batching plant in closest areas around your site
- time travel distance from batching plant to your site as ready mix concrete has a life of 1.5-2 hours
- access of concrete mixer truck from batching plant to your site might only be possible at night times only as most cities do not allow heavy traffic entry in day times
- if your site is located in societies with narrow roads, open wires hanging on poles, it will be impossible for concrete mixer truck to reach the site
It is safe to conclude that if you are willing to use ready mix concrete during construction of your house, proper calculations are required keeping in mind above pros & cons. Concrete pouring is a sensitive process that is to be carried out in single go, if lets suppose total concrete quantity that is required for completing the slab has not been calculated before placing the order at batching plant, or if the batching plant lacks workmanship and has insufficient concrete mixer trucks to meet your requirement, then that slab pouring can be a nightmare for you!