Interviews and Exams questions : ALL About Cement

1: Name the component that responsible for early strength of concrete:

Ans: C3S ( Tri Calcium silicate ) , that react with water and produces more heat of hydration is responsible for early strength of concrete.

2: Which compound contribute to the later strength of concrete ?

Ans: C2S ( Di Calcium silicate ) that hydrates slowly , contribute to the later strength of concrete .

3: After how many days , the compressive strength developed by C3S and C2S are equal .

Ans: ONE year  

4:For road rapid work which type of cement is recommended :

Ans: Rapid hardening cement

5: In how many  days , about 50% of the total heat evolution occurs.

Ans: During the first 3 days of hydration 

6:Which oxides are responsible for high early strength of cement ?

Ans: High total alumina and high ferric oxide content favour the production of high early strength in cement

Compounds : When components of cements added up with water than they called compound in simple language ..

Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength.

In general, the early strength of portland cement concrete is higher with increased percentages of C3S.

Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days.

Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect set times.

Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However, acts as a flux during manufacturing. Contributes to the color effects that makes cement gray.aakes cement gray.

Compounds by percentage :

Role of compounds on properties of cement : MOST IMP

Civil Engineering Competitive Exams Books :For GATE Aspirants :1: http://amzn.to/2A4iy9K 
2: http://amzn.to/2hqwfrR ( more preferably)For SSC JE Aspirants :1: http://amzn.to/2hqwfrR
2: http://amzn.to/2z7CGtm ( Highest rated book for SSC JE)
3: http://amzn.to/2iOjtqm

RCC Book: Best suitable for deep study :
1: http://amzn.to/2iMfgUj (Reinforced Concrete Design - Third Edition ) by Devdas Menon (Author), S. Pillai (Author)

Read More

Los Angeles Abrasion Test , Why and How To Perform

LOS ANGELES ABRASION TEST:

This is hardness test for aggregates, used in Laboratory  to determine the hardness value or abrasion value 

APPARATUS :

 Los Angeles Abrasion Testing Machine ,

Abrasive Charge – Cast iron or steel balls ,
Test sieve – 1.70 mm IS sieve ,

 Balance of capacity 10 kg , Oven , Tray

The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. 

When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. 

The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. 

Therefore, the road aggregates should be hard enough to resist abrasion. 

The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. 

The percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.

Key point of los angles test:

Rotate the machine at a speed of 30 – 33 revolutions per minute. The number of revolutions is 500 for grading A, B, C & D and 1000 for grading E, F & G. The machine should be

5 kg of sample for grading A, B, C & D and 10 kg for grading E, F & G

THE CALCULATION PART:

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 - W2 g

Los Angeles Abrasion Value = (W1 - W2) / W1 X 100

Los angeles abrasion value should lies in below given range for different types of roads

Types of pavement layers                                         Max. Permissible Abrasion Value in %

1:WBM , SUB BASE COURSE                                                      60%

2:WBM BASE COURSE WITH BITUMEN SURFACE               50%

3: BITUMEN BOUND MACADAM                                             50%

4:WBM SURFACING COURSE                                                    40%

5: BITUMINOUS PENETRATION MACADAM                              40%

6:BITUMINOUS SURFACING DRESSING CEMENT
 CONCRETE SURFACING COURSE                                              35%

7:BITUMINOUS CONCRETE SURFACING COURSE                   30%

Read More

Test for bricks

(1) Absorption:

A brick is taken and it is weighed dry. It is then immersed in water for a period of 16 hours. It is weighed again and the difference in weight indicates the amount of water absorbed by the brick. It should not in exceed 20 per cent of weight of dry brick.

(2) Compressive/Crushing strength of Bricks:

The crushing strength of a brick is found out by placing it in a compression testing machine. It is pressed till it breaks.  the minimum crushing or compressive strength of bricks is 3.50 N/mm2. 

The bricks with crushing strength in between of 7 N/mm2 to 14 N/mm2 are graded as A and those having above 14 N/mm2 are graded as AA, 

(3) Hardness test on bricks:

In this test, a scratch is made on brick surface with the help of a finger nail. If no impression is left on the surface, the brick is r sufficiently hard.

(4) Presence of soluble salts:

The soluble salts, if present in cause efflorescence on the surface of bricks. For finding out the presence of soluble salts in a brick, it is immersed in water for 24 hours. It is then taken out and allowed to dry in shade. The absence of grey or white deposits on indicates absence of soluble salts.

If the white deposits cover about 10 per cent surface, the efflorescence is said to be slight and it is considered as moderate, when the white deposits cover about 50 per cent of surface. If grey or white deposits are found on more than 50 per cent of surface, the efflorescence becomes heavy and it is treated as serious, when such deposits are converted into powdery mass.

(5) Shape and size:

In this test, a brick is closely inspected. It should be of standard size and its shape should be truly rectangular with sharp edges. For this purpose, 20 bricks of standard size (190 mm x 90 mm x 90 mm) are selected at random and they are stacked lengthwise, along the width and along the height.

(6) Soundness test on brick:

In this test, the two bricks are taken and they are struck with each other. 
The bricks should not break and a clear ringing sound should be produced.

Other test can be perform but these 6 are the important once.

Read More

Building Demolitions through controlled explosions!

Read More

Compostition of cement

Read More

What is actually poisson's ratio.. Read it u will learn something most important

Poisson's ratio is defined as the negative of the ratio of the lateral strain to the axial strain for a uniaxial stress state. If a tensile load is applied to a material, the material will elongate on the axis of the load ﴾perpendicular to the tensile stress plane﴿,

Tensile deformation is considered positive and compressive deformation is considered negative. The definition of Poisson's ratio contains a minus sign so that normal materials have a positive ratio. Poisson's ratio, also called Poisson ratio or the Poisson coefficient, or coefficient de Poisson, is usually represented as a lower case Greek nu, n. 









Note: Poisson's Ratio has no units

Poisson's ratio is sometimes also reffered to as the ratio of the absolute values of lateral and axial strain. This ratio, like strain, is unit less since both strains are unit less.

For stresses within the elastic range, this ratio is approximately constant. For a perfectly isotropic elastic material, Poisson's Ratio is 0.25, but for most materials the value lies in the range of 0.28 to 0.33.

Generally for steels, Poisson's ratio will have a value of approximately 0.3. This means that if there is one inch per inch of deformation in the direction that stress is applied, there will be 0.3 inches per inch of deformation perpendicular to the direction that force is applied.


In other words poission ratio indicates the fraction by which a material is deformed by the action of compressive  or tensile(elongating) force in one of its perpendicular direction...

the best example to understand its physical effect is when u stretch a rubber band,it increases its length and at the same time,its diameter decreases , amount of decrement is given by poisson's ratio wrt its elongation

Read More

Characteristic strength of concrete

Characteristic strength of concrete is one of the important properties of concrete which indeed unanimously by design engineeror any other person involved in the construction sector.

The compressive strength of concrete is given in terms of the characteristic compressive strength of 150 mm size cubes tested at 28 days (fck)- as per Indian Standards (ACI standards use cylinder of diameter 150 mm and height 300 mm). The characteristic strength is defined as the strength of the concrete below which not more than 5% of the test results are expected to fall.

This concept assumes a normal distribution of the strengths of the samples of concrete.

                               

Normal Distribution curve on test specimens for      determining compressive strength

The above sketch shows an idealized distribution of the values of compressive strength for a certain number of test specimens. The horizontal axis represents the values of compressive strength in MPa. The vertical axis represents the number of test samples for a

particular compressive strength. This is also termed as frequency.

The average of the values of compressive strength (mean strength) from the graph is 40 MPa. The characteristic strength (fck) is the value in the x-axis below which 5% of the total area under the curve falls. From the graph we can clearly say that 30 MPa is the characteristic strength of the given concrete mix. The value of fck is lower than fcm (40 MPa- mean strength) by 1.64σ, where σ is the standard deviation of the normal distribution.

So we can say the given concrete mix has a characteristic strength of 30 MPa or it is a M30 grade mix.

   M- Mix

* Note: For a 95% confidence level k=1.64 , hence k value varies on the confidence level of the experiment

Definition:

Characteristic strength of concrete is the strength of concrete specimens casted and tested as per given code of practice and cured for a period of 28 days; 95% of tested cubes should not have a value less than this value.

Read More

About piles

End Bearing Piles ::-

1:-In end bearing piles, the bottom end of the pile rests on a layer of especially strong soil or rock.

2:- The load of the building is transferred through the pile onto the strong layer.

3:-In a sense, this pile acts like a column.

4:-The key principle is that the bottom end rests on the surface which is the intersection of a weak and strong layer. The load therefore bypasses the weak layer and is safely transferred to the strong layer.

Friction Piles ::-

1:-Friction piles work on a different principle.

2:- The pile transfers the load of the building to the soil across the full height of the pile, by friction.

3:-In other words, the entire surface of the pile, which is cylindrical in shape, works to transfer the forces to the soil.

NOTE: In practice, however, each pile resists load by a combination of end bearing and friction

Read More

POINTS TO REMEMBER FOR CIVIL SITE ENGINEERS

Following are few general points to remember for civil site engineers to make the construction work easier while maintaining quality of construction.

• Lapping is not allowed for the bars having diameters more than 36 mm.
• Chair spacing maximum spacing is 1.00 m (or) 1 No per 1m2.
• For dowels rod minimum of 12 mm diameter should be used.
• Chairs minimum of 12 mm diameter bars to be used.
• Longitudinal reinforcement not less than 0.8% and more than 6% of gross C/S.
• Minimum bars for square column is 4 No’s and 6 No’s for circular column.
• Main bars in the slabs shall not be less than 8 mm (HYSD) or 10 mm (Plain bars) and the distributors not less than 8 mm and not more than 1/8 of slab thickness.
• Minimum thickness of slab is 125 mm.
• Dimension tolerance for cubes + 2 mm.
• Free fall of concrete is allowed maximum to 1.50m.
• Lap slices not be used for bar larger than 36 mm.
• Water absorption of bricks should not be more than 15 %.
• PH value of the water should not be less than 6.
• Compressive strength of Bricks is 3.5 N / mm2.
• In steel reinforcement binding wire required is 8 kg per MT.
• In soil filling as per IS code, 3 samples should be taken for core cutting test for every 100m2.

Density of Materials:

Material	Density
Bricks	1600 – 1920 kg/m3
Concrete block	1920 kg/ m3
Reinforced concrete	2310 – 2700 kg/ m3

Curing time of RCC Members for different types of cement:

Super Sulphate cement: 7 days

Ordinary Portland cement OPC: 10 days

Minerals & Admixture added cement: 14 days

De-Shuttering time of different RCC Members

RCC Member	De-shuttering time
For columns, walls, vertical form works	16-24 hrs.
Soffit formwork to slabs	3 days (props to be refixed after removal)
Soffit to beams props	7 days (props to refixed after removal)
Beams spanning upto 4.5m	7 days
Beams spanning over 4.5m	14 days
Arches spanning up to 6m	14 days
Arches spanning over 6m	21 days

Cube samples required for different quantity of concrete:

Quantity of Concrete	No. of cubes required
1 – 5 m3	1 No’s
6 0 15 m3	2 No’s
16 – 30 m3	3 No’s
31 – 50 m3	4 No’s
Above 50 m3	4 + 1 No’s of addition of each 50 m3

Read More

A Step-by-Step Guide to the Home Building Process

1. Prepare site and pour foundation: Often, site preparation and foundation work are performed by the same crew, but this may not be the case with a wooded lot. Using a backhoe and a bulldozer, the crew clears the site of rocks, debris and trees for the house and, if applicable, the septic system. The crew levels the site, puts up wooden forms to serve as a template for the foundation, and digs the holes and trenches. Footings (structures where the house interfaces with the earth that supports it) are installed. If your home is going to have a well, it will be dug at this point.

If the home has a full basement, the hole is dug, the footings are formed and poured, and the foundation walls are formed and poured. If it’s slab-on-grade, the footings are dug, formed and poured; the area between them is leveled and fitted with utility runs (e.g. plumbing drains and electrical chases); and the slab is poured.

Once concrete is poured into the holes and trenches, it will need time to cure. During this period, there will be no activity on the construction site.

After the concrete is cured, the crew applies a waterproofing membrane to the foundation walls; installs drains, sewer and water taps and any plumbing that needs to go into the first-floor slab or basement floor; and backfills excavated dirt into the hole around the foundation wall. 

INSPECTION #1: When the curing process is complete, a city inspector visits the site to make sure foundation components are up to code and installed properly. This inspection may be repeated depending on the type of foundation (slab, crawl space or basement). Your builder will then remove the forms and begin coordinating step 2, the framing phase.

2. Complete rough framing: The floor systems, walls and roof systems are completed (collectively known as the shell or skeleton of the house). Plywood or oriented strand board (OSB) sheathing is applied to the exterior walls and roof, and windows and exterior doors are installed. The sheathing is then covered with a protective barrier known as a house wrap; it prevents liquid water from infiltrating the structure, while allowing water vapor to escape. This reduces the likelihood of mold and wood rot.

3. Complete rough plumbing, electrical and HVAC: Once the shell is finished, siding and roofing can be installed. At the same time, the electrical and plumbing contractors start running pipes and wires through the interior walls, ceilings and floors. Sewer lines and vents, as well as water supply lines for each fixture, are installed. Bathtubs and one-piece shower/tub units are put in place at this point because there’s more room to maneuver large, heavy objects.

Ductwork is installed for the heating, ventilation and air-conditioning (HVAC) system, and possibly the furnace. HVAC vent pipes are installed through the roof, and insulation is installed in the floors, walls and ceilings.

After the roofing goes on, the house is considered “dried in.” The electrician then installs receptacles for outlets, lights and switches and runs wires from the breaker panel to each receptacle. Wiring for telephones, cable TV and music systems is included in this work.

Note that HVAC ducts and plumbing are usually installed before wiring, because it’s easier to run wires around pipes and ducts than vice versa.

INSPECTIONS 2, 3 and 4: Rough framing, plumbing and electrical and mechanical systems are inspected for compliance with building codes. Most likely these will be three different inspections. At the very least, the framing inspection will be conducted separately from the electrical/mechanical inspections.

At this stage, drywall (also known as plasterboard, wallboard or gypsum board) is delivered to the building site. Sheetrock®, a registered trademark of USG Corporation, is sometimes used as a generic term for drywall.

4. Install insulation: Insulation plays a key role in creating a more comfortable, consistent indoor climate while significantly improving a home’s energy efficiency. One of the most important qualities of insulation is its thermal performance or R-value, which indicates how well the material resists heat transfer. Most homes are insulated in all exterior walls, as well as the attic and any floors that are located above unfinished basements or crawl spaces.

The most common types of insulation used in new homes are fiberglass, cellulose and foam. Depending on the region and climate, your builder may also use mineral wool (otherwise known as rock wool or slag wool); concrete blocks; foam board or rigid foam; insulating concrete forms (ICFs); sprayed foam; and structural insulated panels (SIPs).

Blanket insulation, which comes in batts or rolls, is typical in new-home construction. So is loose-fill and blown-in insulation, which is made of fiberglass, cellulose or mineral-wool particles. Another insulation option, liquid foam, can be sprayed, foamed-in-place, injected or poured. While it costs more than traditional batt insulation, liquid foam has twice the R-value per inch and can fill the smallest cavities, creating an effective air barrier.

Fiberglass and mineral-wool batts and rolls are usually installed in side walls, attics, floors, crawl spaces, cathedral ceilings and basements. Manufacturers often attach a facing such as kraft paper or foil-kraft paper to act as a vapor barrier and/or air barrier. In areas where the insulation will be left exposed, such as basement walls, the batts sometimes have a special flame-resistant facing.

5. Complete drywall and interior textures; start exterior finishes: Drywall is hung and taped so the seams between the boards aren’t visible, and drywall texturing (if applicable) is completed. The primer coat of paint is also applied after taping is complete. Contractors begin installing exterior finishes such as brick, stucco, stone and siding.

6. Finish interior trim; install exterior driveways and walkways: Interior doors, baseboards, door casings, window sills, moldings, stair balusters and other decorative trim are installed, along with cabinets, vanities and fireplace mantels and surrounds. Walls get a finish coat of paint and are wallpapered where applicable.

Generally, exterior driveways, walkways and patios are formed at this stage. Many builders prefer to wait until the end of the project before pouring the driveway because heavy equipment (such as a drywall delivery truck) can damage concrete. But some builders pour the driveway as soon as the foundation is completed so that when homeowners visit the construction site, they won’t get their shoes muddy.

7. Install hard-surface flooring and countertops; complete exterior grading: Ceramic tile, vinyl and wood flooring are installed as well as countertops. Exterior finish grading is completed to ensure proper drainage away from the home and prepare the yard for landscaping.

8. Finish mechanical trims; install bathroom fixtures: Light fixtures, outlets and switches are installed and the electrical panel is completed. HVAC equipment is installed and registers completed. Sinks, toilets and faucets are put in place.

9. Install mirrors, shower doors and finish flooring; finish exterior landscaping:Mirrors, shower doors and carpeting are installed, and final cleanup takes place. Trees, shrubs and grass are planted and other exterior landscaping completed.

INSPECTION #5: A building-code official completes a final inspection and issues a certificate of occupancy (C.O.). If any defects are found during this inspection, a follow-up inspection may be scheduled to ensure that they’ve been corrected.

10. Final walkthrough: Your builder will walk you through your new home to acquaint you with its features and the operation of various systems and components, and explain your responsibilities for maintenance and upkeep as well as warranty coverage and procedures. This is often referred to as a pre-settlement walkthrough. It’s also an opportunity to spot items that need to be corrected or adjusted, so be attentive and observant. Examine the surfaces of countertops, fixtures, floors and walls for possible damage. Sometimes disputes arise because the homeowner discovers a gouge in a countertop after move-in, and there’s is no way to prove whether it was caused by the builder’s crew or the homeowner’s movers.

A Few Words about Inspections: Your new home will be inspected periodically during the course of construction. In addition to mandated inspections for code compliance, your builder may conduct quality checks at critical points in the process. (In the story above, we point out when these inspections typically take place.) The idea is to catch as many potential problems as possible before construction is finished, though some issues may not surface until you’ve lived in the home for a period of time.

Talk to your builder early on about attending inspections, with or without your real-estate agent. Even if your presence is not required, it’s an opportunity to learn more about what’s behind the walls of your new home and how everything works. If you’re planning to hire your own inspector to do an additional review of the home, notify your builder prior to the start of construction.

For safety as well as logistical reasons, builders discourage customers from dropping in unannounced at the construction site. If you’d like to pay a visit, be sure to arrange it in advance. Chances are your builder will conduct regular walkthroughs to bring you up to speed on the progress of the work.

Working with the builder who'll construct your new home is the fifth of six steps to your new home. Here in our New Home Guide, you'll find helpful and inspiring articles, slideshows and videos that will make your new home journey easier and more rewarding.

Read More

BURJ KHALIFA : THE NAME TELLS EVERYTHING== >>

Read More

10 Highest Bridges In The World = =>>

1. Sidu River Bridge, China – Height of 496 m (1,627 ft). This 1,222 m (4,009 ft) long suspension bridge is the world’s highest bridge since 2009. Located in the Hubei Province, it  crosses the valley of the Sidu River

2. Baluarte Bridge, Mexico – Height of 403 m (1,322 ft). A cable-stayed bridge, located along the Durango–Mazatlán highway. The bridge has a total length of 1,124 m (3,688 ft), the second-highest bridge overall

3. Baling River Bridge, China – Height of 370 m (1,210 ft). A suspension bridge in Guizhou Province. The bridge spans over the Baling River Valley. The bridge has a total length of 2,237 m (7,339 ft)

4. Beipanjiang River 2003 Bridge, China – Height of 366 m (1,201 ft). A suspension bridge in Guizhou Province. The bridge has a span width of 388 metres. Between 2003 and 2005, it was the world’s highest bridge

5. Aizhai Bridge, China – Height of 350 m (1,150 ft). A suspension bridge in Hunan, China. It is the world’s highest and longest tunnel-to-tunnel bridge

6. Beipanjiang River 2009 Bridge, China – Height of 318 m (1,043 ft). A suspension bridge in Guizhou Province. It crosses the Beipan River. It was opened to the public in 2009, just 6 years after another (and higher) bridge crossing the same river was opened (see number 4 in this list)

7. Liuguanghe Bridge, China – Height of 297 m (974 ft). A beam bridge in Guizhou, China. It held the record for world’s highest bridge between 2001 and 2003. It is still the highest beam bridge in the world

8. Zhijinghe River Bridge, China – Height of 294 m (965 ft). The highest arch bridge in the world. The bridge crosses the valley of the Zhijinghe River and is opened to the public since 2009

9. Royal Gorge Bridge, Colorado, United States – Height of 291 m (955 ft). The Royal Gorge Bridge is a tourist attraction within a theme park. The bridge deck crosses the Royal Gorge 955 feet (291 m) above the Arkansas River, and held the record of highest bridge in the world from 1929 until 2001. The bridge is 1,260 feet (384 m) long It is the highest in the United States

10. Beipanjiang River Railway Bridge, China – Height of 275 m (902 ft). The world’s highest railway bridge. The bridge spans a deep canyon on the Beipan River in Guizhou province. This is the third bridge within this list spanning over the Beipan river

Read More