Basic Knowledge of civil Engineer

How Much number of bricks required 1cum & how much mortar Quantity Required 1 cum?

500 no. of bricks (brick size - 20cm.*10cm.*10cm.) required
for 1 cum of brick masonry.

and suppose, ratio = 1:6
then, sum = 1+6 = 7

We use 30% mortar in brick work, So 1 cum of brickwork has 0.3 cum of mortar. Quantity for 1:6 mortar mix
as we know, total dry mortar required for 1 cum. of brick
masonry = 0.30 cum.

Therefore following dry material required.

Cement = 1* 0.30/7 = .04 cum. *(1/0.0347) = 1.15 bags.

Density of cement=1440Kg/cum
So 1 bag of Cement Density=50/1440=0.0347Kg

Sand = 6* 0.30/7 = 0.26 cum.
or 0.26 cum. * 35.3 = 9.18 cft.
Material required for 1 cum. of brick masonry in mortar
ratio of 1:6.

Cement = 1.15 bags.
Sand = 9.18 cft.
Bricks = 500 nos. 

Initial & Final setting Time of cement & concrete

Minimum thickness of slab is 125 mm.

Water absorption should not be more than 15 %.

Dimension tolerance for cubes + – 2 mm.

Compressive strength of Bricks is 3.5 N /mm²

Maximum Free fall of concrete allowed is 1.50 m.

In soil filling as per IS code for every 100 sqm 3 sample for core cutting test should be taken.

Electrical conduits shall not run in column

Earth work excavation for basement above 3 m should be stepped form

Any back filling shall be compacted 95% of dry density at the optimum moisture content and in layers not more than 200mm for filling above structure and 300 mm for no structure

F soling is specified the soling stones shall be laid at 45° to 60° inclination (and not vertical) with interstices filled with sand or moorum.

A set of cube tests shall be carried out for each 30 cum of concrete / each levels of casting / each batch
of cement.

Water cement ratio for different grades of concrete shall not exceed 0.45 for M20 and above and 0.50 For M10 / M15 contractor

For concrete grades M20 and above approved admixture shall be used as per mix design requirements.

Cement shall be stored in dry places on a raised platform about 200mm above floor level and 300mm away from walls. Bags to be stacked not more than 10 bags high in such a manner that it is adequately protected from moisture and contamination.

Samples from fresh concrete shall be taken and at least a set of 6 cubes of 150mm shall be prepared and
cured. 3 Cubes each at 7 days and 28 days shall be tested for compressive strength. The test results
should be submitted to engineer for approval. If results are unsatisfactory necessary action/rectification/remedial measures has to be exercised.

Water used for both mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar and organic materials or other substances that may be deleterious to concrete or steel. The ph. shall be generally between 6 and 8.

Cement shall be tested for its setting.
1. The initial setting time shall not be less than 30 minutes.
2. The final setting time shall not be more than 10 hours.

Slump IS 456
Lightly reinforced 25 – 75 mm
heavily reinforced 75 – 100 mm
Trench fill (insitu & Tremie) 100 – 150 mm (For Tremie no need of vibrator)

Curing Days Required
Super Sulphate cement: 7 days
Ordinary Portland cement OPC: 10 days
Minerals and Admixture added cement: 14 days

Cube Samples as per IS-456-2000 Pg. No:29
1 – 5 M³ : 1 No.
6 – 15 M³ : 2 No’s
16 – 30 M³ : 3 No’s
31 – 50 M³ : 4 No’s
Above 50 M³ : 4 + 1 No of addition sample for each 50 M³.

SETTING PROCESS OF CEMENT

When water is mixed with cement to form a paste, reaction starts. In its pure form, the finely ground cement is extremely sensitive to water. Out of the three main compounds, viz. C3A, C3S and C2S, reacts quickly with water to produce a jelly-like compound which starts solidifying. The action of changing from a fluid state to a solid state is called ‘setting’ and should not be confused with ‘hardening’.

During the next stage of hydration, cement paste starts hardening owing to the reaction of C3S and C2S with water and the paste gains strength. The first few minutes, the setting action is more predominant and later on the hardening action becomes dominant. In practice, such solidifying action or loss of plasticity is required to be delayed, because some time is needed for mixing, transporting and placing of concrete into final position before the mix loses its plasticity due to the setting action.

It is usually specified that the plastic concrete should be placed and consolidated before initial set has occurred and it should not then be disturbed until concrete has hardened. This initial setting time should not be too small and therefore, the standard specifies minimum initial setting time.

Once initial stiffening of concrete has taken place, it is desirable that it should harden or gain strength as rapidly as possible, so that there is a minimum of delay before shuttering can be removed and the risk of frost damage in cold climate is minimized. The standard, therefore, specifies the maximum value of final setting time.

It is not however, possible in practice to exactly locate the initial setting time and final setting time. The Indian Standards have selected two arbitrary points which relate setting of cement to the time measured from the moment the water is added.

‘Initial setting time’ is defined as the period elapsing between the time when water is added to the cement and the time at which the needle of 1 mm square section fails to pierce the test block to a depth of about 5 mm from the bottom of the mould. A period of 30 minutes is the minimum initial setting time, specified by ISI for ordinary and rapid hardening Portland cements and 60 minutes for low heat cement.

The ‘final setting time’ is defined as the period elapsing between the time when water is added to cement and the time at which the needle of 1 mm square section with 5 mm diameter attachment makes an impression on the test block . 600 minutes is the maximum time specified for the final set for all the above mentioned Portland cements. IS: 269-1976 specifies the strengths in compression on the standard mortar-cube.

Fig: Vicat Apparatus for Cement Setting Time Test

Compressive strength test has two functions to fulfill. Firstly, it is a final check on the quality of cement. Secondly, in case of doubt, it also helps us to classify the cement as ordinary Portland cement, rapid hardening Portland cement or low heat Portland cement, according to the strength it gives after 3 days and 7 days curing.

It is important to note the difference between setting and hardening of cement at this stage. As has been explained earlier C3A reacts first with water forming hydrated calcium alumino silicates. These compounds contribute very little to the mechanical strength of concrete, but cement starts losing its plasticity because of loss of water due to reaction and formation of gel. This loss of plasticity without development of strength is called setting action.

Cement is said to harden when the cement paste further reacts with water bringing C2S and C3S into action. These compounds contribute to the mechanical strength. Hardening, therefore, is associated with the development of strength.

Sunday, 2/06/2013

1 Cum contains how many Bricks?

no. of bricks = total volume of work/ volume of one brick

1 cubic meter contains 500 bricks of size 20cm x20 cmx 10cm
this is standard.


If size of brick varies then u can find it like this

How much Brick, Cement and sand required in 1 cum Brickwork (1:4)?

For brick size 200mmx100mmX100mm (1:4) for 1 cum

Volume of 1 brick=0.2X0.1X0.1=0.002

Say 12mm thick mortar on brick layer

So vol of brick 212mmX112mmX112mm=0.00265 Cum

No.of Bricks for 1Cum=1/0.00265=376 num bricks

Volume of bricks for 1 cum=376X0.002=0.752cum

Volume of cement mortar 1~0.752=0.25cum                                                        

Add 15% for waste=0.287cum

Add 30% for dry mortar 0.287cum=0.37cum

For cm 1:4=1+4=5

Qty of cement 1/5X0.37=0.074cum

1 Bag of cement=50kg/1440kg/cum=0.0347cum

0.074/0.0347=2.13 Bags

Sand=0.074X4=0.296 cum=10.44 Cuft

Measuring box Sizes?

400mmX300mmX300mm

 

 

 

QUANTITIES OF MATERIALS PER CUBIC METRE OF CONCRETE

ESTIMATED QUANTITIES OF MATERIALS REQUIRED PER CUBIC METRE OF COMPACTED MORTAR OR CONCRETE

NOMINAL MIX			WATER CEMENT RATIO	WATER PER 50KG BAG OF CEMENT	CEMENT		SAND (CUM)	CRUSHED STONES (CUM)
CEMENT	F.A.	C.A.			BY WEIGHT (KG)	BY NUMBER OF BAGS
1	1	-	0.25	12.5	1015	20.3	0.710	-
1	1.5		0.28	14	815	16.3	0.855	-
1	2	-	0.3	15	687	13.74	0.963	-
1	2.5	-	0.35	17.5	585	11.7	1.023
1	3	-	0.4	20	505	10.1	1.06	-
1	4	-	0.53	26.5	395	7.9	1.106	-
1	6	-	0.7	35	285	5.7	1.197	-
1	8	-	0.9	45	220	4.4	1.232	-
1	1	2	0.3	15	560	11.2	0.392	0.784
1	2	2	0.42	21	430	8.6	0.602	0.602
1	1.5	3	0.42	21	395	7.9	0.414	0.828
1	1.66	3.33	0.48	24	363	7.26	0.419	0.838
1	2	3	0.5	25	385	7.7	0.539	0.808
1	2	3.5	0.53	26.5	330	6.6	0.462	0.808
1	2	4	0.55	27.5	310	6.2	0.434	0.868
1	2.5	3.5	0.57	28.5	305	6.1	0.534	0.748
1	2.5	4	0.6	30	285	5.7	0.499	0.798
1	3	4	0.65	32.5	265	5.3	0.556	0.742
1	2.5	5	0.65	32.5	255	5.1	0.446	0.892
1	3	5	0.69	34.5	240	4.8	0.504	0.84
1	3	6	0.75	37.5	215	4.3	0.452	0.904
1	4	8	0.95	47.5	165	3.3	0.462	0.924

Notes:

1. F.A. = Fine Aggregates, C.A. = Coarse Aggregates

2. The table is based on assumption that the voids in sand and crushed stone are 40 and 45 percent respectively.

3. Air content of 1 percent has been assumed.

4. For gravel aggregates decrease cement by 5 percent, increase sand by 2 percent and coarse aggregate in proportion to fine aggregate in mix.

4. No allowance has been made in the table for bulking of sand and wastage./>

1 cubic feet of concrete requires how much coarse aggregate and fine aggregate?

Grade is M20 and ratio for M20 is 1:1.5:3

Void ratio for cement is 100% compressive

Void ratio for fine aggregate 20%

Void ratio for coarse aggregate 32% from IS code

(Note: That means cement have compressive is 100%, fine aggregate needs compressive is 20%, Coarse aggregate needs compressive is 32% from IS code)

Total mix ratio = 1.52

Cement=1, Fine aggregate=1.5, Coarse Aggregate=3

Cement= (1*1.52)/5.5=0.28 m3

50 kg per bag of cement is=50/1440=0.0347m3

Number of bags required=0.28/0.0347=8.069bags=9.85cft

Fine aggregate= (1*1.5*1.52)/5.5=0.41m3=14.48cft

Coarse Aggregate= (1*3*1.52)/5.5=0.83m3=29.20cft

 

QUANTITY OF CEMENT & SAND CALCULATION IN MORTAR

QUANTITY OF CEMENT & SAND CALCULATION IN MORTAR

Quantity of cement mortar is required for rate analysis of brickwork and plaster or estimation of masonry work for a building or structure. Cement mortar is used in various proportions, i.e. 1:1, 1:2, 1:3, 1:4, 1:6, 1:8 etc.

Calculation of quantity of cement mortar in brickwork and plaster:

For the calculation of cement mortar, let us assume that we use 1m³ of cement mortar. Procedure for calculation is:

1. Calculate the dry volume of materials required for 1m³ cement mortar. Considering voids in sands, we assume that materials consists of 60% voids. That is, for 1m³ of wet cement mortar, 1.6m³ of materials are required.

2. Now we calculate the volume of materials used in cement mortar based on its proportions.

Let’s say, the proportion of cement and sand in mortar is 1: X, where X is the volume of sand required.

Then, the volume of sand required for 1: X proportion of 1m³ cement mortar will be

3. Volume of cement will be calculated as:

Since the volume of 1 bag of cement is 0.0347 m³, so the number of bag of cement will be calculated as:

Example:

For cement mortar of 1:6, the quantity calculated will be as below:

Sand quantity:

Quantity of cement (in bags):

Volume of cement =

There number of bags required = = 6.58 bags.

What is clear cover of Beam, Slab, Column, lintel & foundation?

Clear cover for slab-15mm

For beam-25mm

For column-40mm

For foundation-40-60mm

For lintel-20mm

03/042013

Grades of concrete:

Grade of concrete	Mix Proportions	Cement in cum Bags	Water cement ratio
M25	1:1:2	10.95	0.3
M20	1:1.5:3	7.96	0.42
M15	1:2:4	6.25	0.55
M10	1:3:6	4.38	0.75
M7.5	1:4:8	3.36	0.95

How much wastage we considered for cement & steel?

Allowable wastage for steel works is 3 %( i.e. cutting/bending wastage).

For reconciliation purpose, + or -2% allowable for rolling margin in this accounts.

Above 25 mm dia of rods 5% wastage should be considered.

Unit Weights:

Water     -1000 Kg/cum

Cement -1440 Kg/cum

Steel       -7850 Kg/cum

Wood     -1200 Kg/cum

Sand      -1610 Kg/cum

P.C.C      -2400 Kg/cum

R.C.C      -2500 Kg/cum

07/06/2013

How to find out concrete cube Weight?

Unit weight (Density) of concrete=2400 Kg/cum

Density=Mass/volume

So we needed mass, i.e. formula is

Mass=Density X volume

Volume of cube=150mmX150mmX150mm

Mass=2400 X (0.15*0.15*0.15)

Weight of cube in kg=8.1

Units conversion

1m=1000mm

1m=100cm

1m=3.28feet

1m=39.37 inches

1ton=1000Kg

1cum=35.32cuft

1Hectares=100Ares

1hectare=10000m2

1hectare=2.47Acres

How to calculate steel Quantity?

Steel Quantity=Number of bars X Length of one Bar X unit weight of steel

Unit Weight of steel=D2/162

What is rolling margin for reinforced steel and how it is calculated?

Rolling margin is percentage of diviation in Sectional weight of Reinforcement steel allowable as per IS codes. Reinforcement steel is extruded from a mould which is made for a particular size e.g. 8mm Dia.When the mould is brand new, the sectional weight of 8mm steel extruded through mould would exact as per IS standard of lower than that.i.e. 0.395Kg per Metre or lessor. Mould gets little bigger after certain period of time or after certain quantity of production is taken from a particular mould. Now same 8mm dia bars extruded from the same mould will have more weight per Metre say 0.400Kg per Metre insted of 0.395 as per IS. That is more mass per Metre/Length is required for same length. This diviation in weight is defined in IS codes for different dia which is as under:-

8mm to 10mm +_ 7%

12mm to 16mm+- 5%.

20mm and above+ -3%.

Rolling Margin is calculated as under:-

Total Weight of Bars (Dia wise) / Total Running Metre of Bars = Actual Sectional Weight of bars.

Compare sectional weight with Standard IS Weight.

Weight as per IS Standard.= Dia X Dia / 162.

Rolling margin is the difference between the theoretical and actual weight of steel. This is because of the die which is used for casting of rebars.Over a period of time the shape of die changes and as a result the diameter of the steel bar also changes which results in difference in unit weight of steel.

The size of the die is kept small and as a result rolling margin is negative in the initial stage of production, there after it is more of less close to theoretical weight and then the size of die increases which results in rolling margin on positive side.

If you purchase steel from same supplier over a period of time the rolling margin would be adjusted and you are not at a loss.

How to calculate steel quantity for footings, Columns, beams, Slab?

Approx., 1.5 to 2% steel in columns,

            1 to 1.5% steel in Beams

            0.7 to 1% steel in slabs

If concrete is 100cum in column

Than we take min 1.5% and max 2% steel

It will be 1.5 cum to 2.0 cum steel

1.5X7850=11775Kg/m3

2.0X7850=15700Kg/m3

Density of steel=7850Kg/m3

Footing reinforcement details?

One Way Slab:

One way slab is the slab having ratio of longer span to shorter span equal to or more than 2. In one way slab main tensile reinforcement is placed parallel to shorter side which will be the main steel,

Ly/lx>2 one way slab

One way slab=longer span/Shorter span >2

Two Way slab:

 If the ratio of longer span to shorter span is equal to or less than 2, then such slabs are called as two way slab.
Where as in two way slab both direction required main steel.

ly/lx<2 two way slab

Two way slab=longer span/shorter span<2

WHAT IS A COLUMN, SHORT COLUMN, LONG COLUMN

Column:
A column is a vertical compression member.  A column is subjected to axial compressive loads.

Short Column:
When the ratio of effective length to the least lateral dimensions of the column is less than 12, then it is
called a short column.

(or)
When the ratio of effective length to the least radius of gyration is less than 45, then it is called a short column

Long Column:
When the ratio of effective length to the least radius of gyration is greater than 45, then it is called a long column.

A long column is subjected to bending moment in addition to direct compressive stress.

The load carrying capacity of a long column is less than a short column

The load carrying capacity of a long column depends upon slenderness ratio (slenderness ratio increases then the capacity of the column decreases)

How to calculate the lap length rod of column, Beam, Slab?

Lap Length Definition:

For column

When fc’=4000psi, Minimum lap length is 12 inch.

Or fy less or equal 60000psi, lap length=0.0005*fy*db where

db. is diameter of reinforcement in inch or mm

When fy is greater than 60000psi, lap= (0.0009fy-24)db.

When fc’ is less or equal 3000psi, required lap will multiply with 1.33333

For Beam

In tension Zone, Lap=60db, where db. in mm

In compression zone, lap=44db, where db. in mm

For Slab Lap=50db

What the difference between lap splice length and development length is for rebar’s?

The difference between the two is in the application. A development length is the amount of rebar length that is needed to be embedded or projected into concrete to create a desired bond strength between the two materials. The lap splice length is the length two rebar pieces must overlap and be tied together to create a bond as if there was no break and the run is "continuous". So simply put, development is rebar to concrete, splice is rebar to rebar. The lengths of both splice and development do vary. They are dependent upon different factors. These include but are not limited to concrete strength, rebar size, rebar coating and concrete cover or clearance. So when you see a chart on one project, it can differ from another for these reasons.

Development Length:

Development length is the length overlap of bars tied to extend the reinforcement length. is about 50 times the dia of bar is consider to safe.

AnchorageLength:
Anchorage length- this is the additional length of bar required it insert in another at the junction. For example-Main bar of the beam in column at beam column junction. this length is similar to the lap length.

What is meant by carpet area, built-up area and super built-up area?

Carpet Area:

Carpet area is the actual usable area of an apartment, office unit, showroom, etc. minus wall thickness. Carpet area is the area enclosed within the walls, actual area to lay the carpet. 

This area does not include the thickness of the inner walls.

Build Up Area:

Built-up area is the carpet area plus the thickness of outer walls and the balcony. 

Super Build Up Area;

Super built-up area is the built up area plus proportionate area of common areas such as the lobby, lifts shaft, stairs, etc. The plinth area along with a share of all common areas proportionately divided amongst all unit owners makes up the super built-up area.