In this post, we are going to discuss "How to calculate concrete volume and it's ingredients?"
How to Calculate Concrete Volume?
If it is a volume, then we know there must be 3 dimensions, Length, Height, Width or Breadth.
For Slab, If we need to calculate the concrete volume,
Volume = Length x Breadth x Width / Thickness = 5 x 3 x 0.125 = 3.75 cu.m
For Beam, If we need to calculate the concrete volume,
Volume = Length x Breadth x Width = 5 x 0.6 x 0.3 = 0.9 cu.m
For Column, If we need to calculate the concrete volume,
Rectangular Column, Volume = Height x Breadth x Width = 5 x 0.6 x 0.3 = 0.9 cu.m
Circular Column , Volume = 𝛑r˄2h = 3.14 x (0.15)˄2 x 5 = 0.35 cu.m
CONCRETE INGREDIENTS CALCULATION:
For cement, sand and coarse aggregate.
This is a volumetric calculation.
Assuming we need 2 cu.m of concrete for M20 mix,(Mix ratio, M20 = 1:1.5:3)
Total part of the concrete = 1 + 1.5 + 3 = 5.5 parts
Therefore, Cement Quantity = (Cement Part / Concrete Parts) x Concrete Volume
= (1 / 5.5) x Concrete Volume = (1 / 5.5) x 2 = 0.3636 cu.m
Density of Cement = 1440 kg / cu.m = 0.3636 x 1440 = 523 kg = 10.5 approx.bags
Sand Quantity = (Sand Part / Concrete Parts) x Concrete Volume = (1 / 5.5) x 2 = 0.5454 cu.m
Coarse Aggregate = (Coarse aggregate part / Concrete parts) x Concrete Volume = (3 / 5.5) x 2 = 1.09 cu.m
WATER CEMENT RATIO:
According to IS 10262 (2009), Assuming Water-Cement Ratio for the concrete as 0.45
Required amount of water = W/C ratio x Cement volume
Therefore, Water = 0.45 x 0.3636 = 0.16362 cu.m
[Unit Weight of Water = 1000 liters/cu.m]
Required amount of water = 0.16362 x 1000 = 163.32 liters
Therefore,we need 10.5 bags of cement , 0.5454 cu.m of sand , 1.09 cu.m of coarse aggregates and 163.62 liters of water.
DIFFERENCE BETWEEN PLASTERING AND POINTING:
Plastering and pointing or two common terms in building construction. However, both are not same. The difference between plastering and pointing are as follows:
1. The main objective of plastering is to protect the exposed surface of the masonry. That's why motor is applied to the total surface of the masonry. But in pointing only joints are filled with mortar.
2. Cement, sand, lime mortar is used in plastering. But only cement mortar is used in pointing.
3. Plastering is done both the inside and outside surfaces. Pointing is done only on the outside parts.
4. Large amount of materials is required for plastering work. On the other hand less amount of materials is required in pointing work.
5. After plastering the surface becomes smooth and plain. It gives better appearance to the structure. But after Pointing the surface do not become plain as plastering.
6. After plastering the defects of masonry are not visible, but the defects of masonry can be seen in case of pointing.
7. Plastering can be done in all types of brick surface. But pointing is only suitable for first class bricks.
BRICKWORK CHECKLIST FOR SITE ENGINEERS:
While on site, a site engineer must ensure that the brickwork is going on as per quality requirements. Some of the general requirements of quality of brickwork are mentioned below. Use this as a checklist while executing brickwork.
1. The thickness of joint in brick masonry should not exceed 1 cm.
2. The face joints should be raked to a depth of 15mm by raking tool when the mortar is still green so as to provide proper key for plastering or pointing.
3.Brick work should be taken up in layers not exceeding one meter height at a time.
4.Check that the brick work is in plumb.
5.Check that the brick courses are in level.
6.Check the quality of bricks with specific reference to
- Strength
- Efflorescence
- Dimensional accuracy
- Water absorption
7.Check that no brick bats are used as queen closer.
8.Check strength of mortar by scratching with sharp instrument like screw driver.
9.Check the quality of sand in mortar.(Test for fitness modulus and silt content).
10.Check mixing of mortar whether done by hand or by machine, whether mixing is done on a proper platform.
11.Check arrangements for curing.
12.Whether raking of green joints done or not.
13.Whether soaking of bricks done or not.
14.Check general quality of works with reference to lines, levels,
thickness and trueness of the joints.
15.Whether brick corners are provided properly by a proper brick closer and not by pitting brick bats.
16.Whether top courses in plinth, in window sill and below RCC slab and parapet are provided with brick on edge.
17.Whether joints of brick work are filled with mortar fully, check especially vertical joints.
18.Check type of scaffolding and whether tied and braced properly.
19.Check reinforcement in brick partition wall, whether provided.
20.Check bonding of cross wall with long walls.
21.Whether holes left in the brick work while execution for supporting scaffolding are filled with concrete and not with dry bricks.
The cardinal difference between Working Stress Method (WSM) and Limit State Method (LSM) is : WSM is an elastic design method whereas LSM is a plastic design method.
In elastic design, i.e WSM, the design strength is calculated such that the stress in material is retained to it's yield limit, under which the material follows Hooke's law, and hence the term "elastic" is used. This method yields to uneconomical design of simple beam, or other structural elements where the design governing criteria is stress (static).
However, in case of shift of governing criteria to other factors such as fatigue stress, both the methods will give similar design. Also, WSM substantially reduces the calculation efforts.
Now coming to the plastic design, i.e. LSM, as the name suggests, the stress in material is allowed to go beyond the yield limit and enter into the plastic zone to reach ultimate strength. Hence the "moment rotation" capacity of beam, for example, is utilized making the design more economical. However, due to the utilization of the non-linear zone, this method involves arduous calculation.
All other differences are mostly derived from the above stated fundamental difference along with few general differences. Some of these differences are stated below:
- Serviceability check in case of LSM is required because after the elastic region strain is higher, which results in more deformation, hence a check is necessary.
- LSM is strain based method whereas WSM is stress based method.
- LSM is non-deterministic method where WSM is deterministic approach.
- The partial safety factor is used in LSM whereas Safety factor is used in WSM.
- Characteristic values (derived from probabilistic approach) are used in case of LSM whereas Average or static values are used in WSM.
CALCULATION OF SHUTTERING AREA:
Shuttering or formwork is a temporary, rigid structure in which the cast in situ concrete is poured for casting the members to required shape. Different formworks are used for different shape members.
In this article,we will discuss how to calculate the shuttering area before construction.
Before calculating the shuttering area first, we need to know how to calculate the peripheral length of any shape.
PERIPHERAL LENGTH/PERIMETER:
We know that perimeter is the distance around a 2D(two dimensional) shape.
For example, square has four sides. Let's be the length of one side,then
∴The peripheral length = S+S+S+S = 4S.
Rectangle has four sides also but the length ans breadth is different, let length is 'l' and breadth is 'b'
∴Peripheral length = l+b+l+b = 2l+2b
Now coming to the calculation of shuttering area.
Shuttering area = Peripheral length x Depth
Let me show you an example,
Here the shape is rectangle,
∴Peripheral length = 2l + 2b
= (2x1) + (2x0.8)
= 2 + 1.6
= 3.6
∴Total shuttering area = Peripheral length x Depth
= 3.6 x 4
= 14.4 sq.m
Following are the steps to calculate the quantity of steel for RCC slab:
- Prepare a bar bending schedule in order to classify different shapes of bars (bent up bar, straight anchor bar, curtail bar etc) and diameters.
- List down all the shapes of bars from the drawing.
- Count the number of bars of each of those shapes.
- Then calculate the cutting length of each of those bars.
Cutting length of bar = (length of member - deduction for cover on both sides) + development length.
- Then calculate the unit weight of each dia bars by the following formula:
W = d² / 162.
where,
d is the dia in mm
w is the weight in kg.
- Then calculate the weight of rebar
Weight of rebar = no. of bars x cutting length x unit weight
- Add all the weight to get the total steel quantity.
NOTE:
1. Minimum % of steel as per Indian standards are:
- Beam (Tension reinforcement):
As = 0.85 bd/fy of gross section area.
- Slab - 0.12% of total area
- Column - 0.8% of total area.
2. Maximum % steel as per Indian standard are:
- Beam - 4% of cross-section area
- Slab - 4% of cross-section area
- Column - 6% of cross-section area.
3. Development length is usually specified in the drawings, but if not then you can calculate it as,
D.L = Depth - 2 times cover.
4. Binding wire = 10 grams per kg of reinforcement.
5. No. of stirrups = (length of member - 2 x cover)/spacing + 1.
RCC STAIRS OR REINFORCED CONCRETE STAIRS:
RCC stairs may be the most common stairs widely used than any other type of stairs. These stairs can be easily moulded to any desired shape and are better tear and fire resistant. The steps of RCC stairs are made by using ordinary cement concrete. Besides ordinary cement concrete, some other superior finishing materials are also used such as marble, terrazzo, tiles etc. to give them better appearances.
ADVANTAGES OF RCC STAIRS:
The advantage of R.C.C stairs are as following:
- R.C.C stairs are better fire resistant than any other stairs.
- They are adequately strong and more durable.
- The steps are no-slippery.
- They offer better and pleasant appearances.
- The stairs can be designed for greater widths and longer spans.
- They can be easily cleaned.
- R.C.C stairs can be precast or cast in situ.
- The maintenance cost is almost nil.
- In modern sky scraper construction always framed structures are adopted, for such structures R.C.C stairs are the one and only stairs which can be used.
Volume = Length x Breadth x Width = 5 x 0.6 x 0.3 = 0.9 cu.m
