Estimation of Concrete

Terminologies, Standards and Specifications of Concrete

Description

In any civil Engineering project concrete is usually considered one of the expensive materials. Especially, when we talk about reinforced cement concrete, in which steel reinforcement is provided so it can increase the project cost if proper estimation will not be done. This article comprises the complete estimation of Concrete by considering the civil Engineering drawing plan. We will be estimating the volume of concrete for Roofing, lintels (small beams above doors), and foundation.

 

Before starting the estimation of Concrete, let’s have a brief overview of the history of concrete, Terminologies, standards, and drawing details of concreting.

Brief History of Concrete

The history of Concrete when it was invented depends on how inventors interpret the concrete.

It is cleared that it has come a long way when concrete was discovered. There are some notable events about the History of Concrete.

Discovery in the United Arab Emirates (UAE)

            As long as (6500 BC), the Nabataea traders who discovered the Concrete first time in the region of Jordan. They built small concrete structures and concrete floor

         

Discovery in Egypt and China

            As long as (3000 BC), they discovered concrete by mixing mud with straw. When it applied for binding of Bricks, notable binding properties were seen, they called it Concrete. Egyptians used Gypsum and lime mortar in the construction of the Pyramid. Similarly, In China a type of binding material was used in the construction of the Great wall, they Called it Concrete.

 

Discovery in Rome

            As long as (600 BC) it is cleared that the Romans were not first who invented the concrete but they were first who used Concrete for Various Purposes and Built a lot of Structures. They implemented the use of Concrete in various Civil Engineering projects. Apart from this, they invented a lot of combination of concrete with admixtures for more sustainability

 

 

 

They prepared a mixture of lime, Volcanic ash, and seawater then they stacked the blocks (just like bricks) when it hardened after pouring into wooden molds. After a long period, Roman structures were considered more sustainable and tall due to their discovery of admixtures.

Terminologies and their description

Concrete

Concrete is the mixture of four components; cement sand aggregates and water. their ratios usually vary, depending upon the strength you required.

On the basis of Reinforcement, there are two types of concrete.

 

  1. i )-Plain Cement Concrete (without Reinforcement)

Plain cement concrete (PCC) is the mixture of only cement sand aggregates and

Water. there is no steel reinforcement provided in PCC.

Where it is used?

            PCC is used where there is only compressive strength is required and tensile strength is not required

  1. II )-Reinforced cement Concrete (with reinforcement)

            Reinforced Cement Concrete (RCC) is the mixture of cement sand aggregates and water along with steel reinforcement

where it is used?

            RCC is used where there is a need of both compressive and tensile strength

          

Note:

Whenever we apply the load on any structural member there are two types of main stresses develop; tensile and compressive. Concrete is strong in compression and weak in tension whereas steel is strong in tension. If there is pure compression, then there is no need for steel and we use PCC while if there are compression and tension then there is need of steel reinforcement as concrete is weak in tension so we use RCC.

 

On the basis of many aspects concrete has been classified. Let’s discuss the classification of concrete on the basis of the quantity of cement

 

  1. i )-Lean concrete:

If the quantity of cement is less than 10% of total content, it is called lean concrete

It is usually used in floors and foundations.

For example: (cement: sand: aggregates) PCC (1:4:8) and (1:6:12)

  1. ii )-Normal concrete:

If the quantity of cement is between 10% to 15% of the total content, then it is called

Normal Concrete is generally used in the damped proof course and in floor finishing.

For example: (cement: sand: aggregates) PCC (1:2:4)

  • iii )-Rich Concrete:

if the quantity of cement is more than 15% of total content, then it is called rich

concrete. It is used in RCC when there is a heavy load on small structures.

For example: (cement: sand: aggregates) PCC (1:1.5:3)

 

Mix design of Concrete:

The calculation of right quantities of concrete ingredients; cement sand and aggregates for desire strength. It is called a mixed design of Concrete. If concrete mix design is accurate then the construction project can be economical.

Ordinary mix designs:

Typical cross-section details of Concrete:

Cross-section of Roof slab

Cross-section of concrete beam

Cross-section of Column

Let’s take an example of Civil Engineering drawing plan and calculate the concrete and steel for various structural members

Note:

It is cleared from our drawing plane that there are no main beams and columns. There are only roof slabs lintel (small beams above doors and windows) and foundation where the concrete will be used in our drawing plan. The process of estimation for concrete work will remain the same for all structural members.

Total Volume of Concrete:

Total Center line (9”) = 13’ + 6’ + 13’ + 11’ + 5.5’ + 10’ + 6.5’ +

  10’ + 6.5’ + 5.5’ + 13’ + 11’ + 19’ + 13.33’ + 13’ + 11’ + 6’ + 6’ +

  (9” + 4.5” + 9” + 9” + 9” + 9” + 9” + 9” + 9” + 9” + 9” + 9” + 9”

   + 4.5”) = 189.08’

 Total Center Line (4.5”) = 4.25’ + 6’ + 9” = 11.25’

Note:

  1. Junction correction of walls for PCC in the foundation

Correction = total length (9’’ wall) – 1/ 2(t1) N1

Where N is the number of the junction where the 9-inch wall is meeting with each other and t

Is the thickness of the wall

Correction = total length (4.5’’ wall) – 1/ 2(t1) N1

Where N is the number of the junction where a 4.5-inch wall is meeting with each other and

t is the thickness of the wall

  1. The total volume of Roofing= total area of plan thickness of the slab

  2.  

Estimation of Concrete in Foundation:

As this is estimation for house plan so commonly “stepped foundation” is used and the PCC layer is applied after the excavation.

 

Mix Design for Foundation: M 7.5 (1:4:8)

Area of foundation= 511.45 ft2

Thickness of PCC layer= 9” = 0.75’

Volume = Area  thickness = 511.45  0.75 =  383.58 cubic feet

Note:

as we know the wet volume of concrete is less than then dry volume because as we mix the cement sand and aggregate with water due to evaporation of air voids there is a reduction in volume by 54%

Dry volume = (wet volume) (1.54)

Dry volume = (383.58) (1.54) = 590.71 cubic feet

Sum of ratio = 1+4+8= 13

Calculation of cement bags

Cement =   = 45.43 cubic feet

Volume of one bag of cement = 1.25 cubic feet

Total number of bags = 45.43 / 1.25 = 37 bags = 1850kg

Calculation of sand

Sand =   =  181.75 cubic feet

Calculation of aggregates

 Aggregate = =   =   363.51 cubic feet

 

Quantity of water

Water cement ratio = weight of water/ weight of cement

Usually w/ c = 0.5

Weight of water = 1850 0.5= 925kg (liter)

Estimation of Concrete in lintel: (RCC)

            The lintel is small concealed (hidden) concrete beams above doors and windows

Mix design for Lintel = M 20 = 1:1.5:3

 The total volume of Concrete for lintel = 30.56 Cubic feet

Note:

Quantity of steel (Thumb Rule)

  • Slab 0.6% of Concrete

  • Beam 1% of Concrete

  • Column 1 – 4 % of Concrete

  • For Steel: – 1cu.ft = 490lbs= 222.26kg

  • m = 7850kg

Dry volume = (wet volume) (1.54)

Dry volume = (30.56) (1.54) = 47.062 cubic feet

Sum of ratio = 1+1.5+3= 5.5

Calculation of cement bags

Cement =   =  8.5cubic feet

Volume of one bag of cement = 1.25 cubic feet

Total number of bags = 8.5 / 1.25 = 7 bags = 350kg

Calculation of sand

Sand =   =  12.83 cubic feet

Calculation of Aggregates

 Aggregate = =   =   25.56 cubic feet

 

Quantity of water

Water cement ratio = weight of water/ weight of cement

Usually w/ c = 0.5

Weight of water = 350 0.5= 175kg (liter)

Steel = 1% of 47.06 =0.47 = 104kg

Estimation of Concrete in Slab: (RCC)

 

Mix Design= 1:2:4

Total Volume: 412.31 Cubic feet

Dry volume = (wet volume) (1.54)

Dry volume = (412.31) (1.54) = 634.95 cubic feet

Sum of ratio = 1+2+4 = 7

Calculation of cement bags

Cement =   = 90.7 cubic feet

Volume of one bag of cement = 1.25 cubic feet

Total number of bags = 90.7 / 1.25 = 73bags =3650

Calculation of sand

Sand =   =  181.41 cubic feet

Calculation of aggregates

 Aggregate = =   =   362.82 cubic feet

 

Quantity of water

Water cement ratio = weight of water/ weight of cement

Usually w/ c = 0.5

Weight of water = 3650 0.5=  1825 kg (liter)

Steel = 0.6% of 634.95= 3.80 = 845 kg

Conclusion

From the above estimation, it is concluded that there are some technical aspects which need to keep in while during the calculation concrete work


  1. Standard mix designs should be used for various structural members if you don’t how to prepare mixed designs for desire strength.
  2.  
  3. Mix designs in concrete play a vital role in cost estimation. If proper mix design will not be used for a structural member then the project can be uneconomical

Follow us

All Posts

Reviews

3D Studio Max

Projects

+ Building Works

+ Infra Structure

+ Surface Drainage System

+ Roads & Highways

+ High Rise Buildings & Towers

+ Water Supply & Sewerage System

+ Pipeline Construction