Hoover dam bridge construction animated

Hoover dam bridge construction animated

Tour inside Burj Khalifa (Burj Dubai)

148 floors in the sky: The view from the Burj Khalifa

Far above the desert, in the heart of the city of Dubai, stands the tallest building in the world. A stunning tower of steel, concrete and glass.

What is Bitumen and its uses?

What is Bitumen and its uses?

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Bitumen is the binding material present in asphalt. Sometimes it is also known as mineral tar. Bitumen is produced by partial distillation of crude petroleum.

Please , tell us procedure of Bulk density of bricks?

Please , tell us procedure of Bulk density of bricks?

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Objective:

To determine the bulk density of bricks.

which one is better ,concrete block or brick masonry?

which one is better ,concrete block or brick masonry?

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Both concrete block and brick masonry are strong, fire-resistant, insect-proof building materials. They have a lot of thermal mass, which helps them retain heat and makes up for their relatively low insulation value. However, despite their similarities, block and brick have some major differences.

What does 33,43 and 53-grades of cement mean?

What does 33,43 and 53-grades of cement mean?

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Cement is a very important building material used in the construction industry. It’s essentially a fine powder, which when mixed with water undergoes chemical change and thereafter allowed to set and harden is capable of uniting fragments or masses of solid matter together to produce a mechanically strong material.

When and Where Pile Foundations are Used?

When and Where Pile Foundations are Used?

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Pile foundations are generally adopted in the following situations:

1. The sub-soil water table is very high which can easily affect other foundations.

Flow Table Test

Flow Table Test

This test was covered by BS 1881 : 105 : 1984. The test is appropriate for concrete of high and very high workability, including flowing concrete which would exhibit a collapse slump.

What is meant by 80/100 grade bitumen?

What is meant by 80/100 grade bitumen?

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A 80/100 grade bitumen indicates that its penetration value lies between 80 & 100.Grading of bitumen helps to assess its suitability in different climatic conditions and types of construction. For bituminous macadam and penetration macadam, IRC suggests bitumen grades 30/40, 60/70, 80/100.

HOW TO CHECK QUALITY OF CEMENT AT SITE?

HOW TO CHECK QUALITY OF CEMENT AT SITE?

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Cement is one of the most important materials used in construction. The strength of a structure depends upon several factors, cement quality is one of them. To achieve the desired strength of concrete and to increase the longevity of structure good quality cement should always be used.

How to move loads in the expansion joints in bridge

How to move loads in the expansion joints in bridge

What are the different types of Loads on Structures?

What are the different types of Loads on Structures?

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The types of loads acting on structures for buildings and other structures can be broadly classified as vertical loads, horizontal loads and longitudinal loads. The vertical loads consist of dead load, live load and impact load. The horizontal loads comprises of wind load and earthquake load. The longitudinal loads i.e. tractive and braking forces are considered in special case of design of bridges, gantry girders etc..

How to calculate specific gravity of cement?

How to calculate specific gravity of cement?

Using Le Chatelier Flask method, we can determine this value. This is an experiment conducted at the site level.

Staircas-reinforced details

Staircas-reinforced details

QUALITY CONTROL MEASURES AT SITE

QUALITY CONTROL

MEASURES AT SITE

Study duties responsibilities, Tender specification, standards, codes of practice and work instruction.

Evolve effective acceptance/rejection procedures for construction materials in coordination with the project purchase department.

Do proper sampling and testing of steel, cement, concrete, aggregates, water, etc., and verify test results in view of standards and work specifications prior to their use in construction. Also control quality of electrodes to their use in welding.

Set procedures to control quality at the points of storage for raw materials, mixing and placing of concrete.

Follow the prescribed curing and deshuttering schedules.

Observe procedures to control quality of welded joints of structural steel members.

Evolve a system to check quality of workmanship in all construction activities.

Keep all revised Indian Standards and codes of practice available in QC laboratory and have them handy during discussion with client/consultant.

Maintain sequence of construction required under any activity.

Discuss QA/QC issues as a separate agenda during site review meetings with staff.

Observe regular schedule for maintenance, repairs and calibration of plants and equipments.

Keep spare parts/materials for laboratory equipments weigh batchers, batching plant, etc., always keep spare vibrators ready at site.

Carry work instruction cards in pocket while supervising/inspecting works.

Regularly maintain the formats prescribed under ISO 9002 Quality assurance system

Practice sound house keeping methods to achieve saving, safety and quality.

How to Calculate Number of Bricks Per Square Foot?

How to Calculate Number of

Bricks Per Square Foot?

No matter what the nature of a brickwork project, calculating the number of bricks per square foot helps determine how many bricks are needed for the project as a whole. You also need to know the square footage of the area where the bricks are needed, such as a wall or a patio. Once you've calculated these figures, you can estimate the amount of bricks needed. Include 5 to 10 percent of overage as well, in case of breakage or damaged bricks.(Figure-1)

Step 1:

Measure the length and width of one brick with a tape measure. Multiply the length and width, such as 4 inches wide by 8 inches long, to get the total square inches. Note: This is for bricks that will install with their broad faces up, as with patio pavers. If the bricks will install with their front faces exposed, as with standard wall brick, measure the length and the height, not the width..(Figure-2)

Step 2:

Divide the total square inches into 144, which is the total number of inches in a square foot. If the brick is 32 square inches, for instance, the result is 4.5 bricks per square foot (144 divided by 32)..(Figure-3)

Step 3:

Measure the length and width of the project space, such as a patio or wall 10 feet high, 12 feet wide. The resulting number -- in this case, 120 -- is the square footage of the project space..(Figure-4)

Step 4:

Determine the amount of bricks needed for the job by multiplying the square footage -- 120 square feet -- by the number of bricks in a square foot -- 4.5. For this instance, 540 bricks are needed. Keep in mind some bricks may be damaged or unusable, so purchase more than necessary for the job. A project such as a patio or walkway may not require mortar between bricks as a wall does. A mortarless installation requires more bricks than a project involving mortar..(Figure-5)

PROPER METHODS FOR CONCRETE PLACEMENT

PROPER METHODS FOR 

CONCRETE PLACEMENT 

PROCEDURE FOR PLACING 

OF CONCRETE:

Before any concrete is placed the entire placing programme consisting of equipment, layout, proposed procedures and methods is planned and no concrete is placed until formwork is inspected and found suitable for placement. Equipment for conveying concrete should be of such size and design as to ensure a practically continuous flow of concrete during depositing without segregation of materials considering the size of the job and placement location.

Concrete is placed in its final position before the cement reaches its initial set and concrete is compacted in its final position within 30 minutes of leaving the mixer and once compacted it should not be disturbed.

In all cases the concrete is deposited as nearly as practicable directly in its final position and should not be re-handled or caused to flow in a manner which may cause segregation, loss of materials, displacement of reinforcement, shuttering or embedded inserts or impair its strength. For locations where direct placement is not possible and in narrow forms suitable drop and Elephant Trunks to confine the movement of concrete is provided. Special care is taken where concrete is dropped from a height especially if reinforcement is in the way particularly in columns and thin walls.

Concrete should be placed in the shuttering by shovels or other methods and should not be dropped from a height more than one metre or handle in a manner which will cause segregation.

Concrete placed in restricted forms by borrows, buggies, cars, sort chutes or hand shoveling should be subjected to the requirement for vertical delivery of limited height to avoid segregation and should be deposited as nearly as practicable in it’s final position.

Concreting once started should be continuous until the pour is completed. Concrete should be placed in successive horizontal layers of uniform thickness ranging from 150 mm to 900 mm. These should be placed as rapidly as practicable to prevent the formation of cold joints or planes of weakness between each succeeding layers within the pour.

The thickness of each layer should be such that it can be deposited before the previous layer has stiffened. The bucket loads or other units of deposit should be spotted progressively along the face of the layer with such overlap as will facilitate spreading the layer to uniform depth and texture with a minimum of shoveling. Any tendency to segregation should be corrected by shoveling stones into mortar rather than mortar onto stones. Such a condition should be corrected by redesign of mix or other suitable means.

The top surface of each pour and bedding planes should be approximately horizontal unless otherwise specified in drawings.

WRITING SPECIFICATIONS CONSTRUCTION CONTRACTS

WRITING SPECIFICATIONS FOR

CONSTRUCTION CONTRACTS

In writing specifications for construction contracts, care must be taken to ensure consistency of requirements throughout and conformity with what is written in other documents. This consistency can be promoted if one person drafts all the documents or, if parts are written by others, one person carefully reads through the whole finished set of documents. An inconsistency in the documents can give rise to a major dispute under the contract, having a serious effect on its financial outcome.

Some principle guidelines for writing specifications are as follows.

• The layout and grouping of subjects should be logical. These need planning out beforehand.

• Requirements for each subject should be stated clearly, in logical order, and checked to see all aspects are covered.

• Language and punctuation should be checked to see they cannot give rise to ambiguity.

• Legal terms and phrases should not be used.

• To define obligations the words ‘shall’ or ‘must’ (not ‘should’ or ‘is to’, etc.) should be used.

• Quality must be precisely defined, not described as ‘best’, etc.

• Brevity should be sought by keeping to essential matters.

It is not easy to achieve an error-free specification. It is of considerable assistance to copy model clauses that, by use and modification over many previous contracts, have proved satisfactory in their wording. Such model clauses can be held on computer files so they are easy to reproduce and modify to make relevant to the particular project in hand. Copying whole texts from a previous specification which can result in contradictory requirements should not be adopted. Entirely new material is quite difficult to write and will almost certainly require more than one attempt to get it satisfactory.

The specification has to tell the contractor precisely:

• The extent of the work to be carried out;

• The quality and type of materials and workmanship required;

• Where necessary, the methods he is required to use, or may not use, to construct the works.

Under the first an informative description is given of what the contractor is to provide and all special factors, limitations, etc. applied. Under the second the detailed requirements are set out. The extent of detail adopted should relate to the quantity and importance of any particular type of work in relation to the works required. Thus the specification for concrete quality may be very extensive where much structural concrete is to be placed; but it may be quite short if concrete is only required as bedding or thrust blocks to a pipeline. A ‘tailormade’ specification appropriate to the nature of the work in the contract should be the aim.

Repetition of requirements should be avoided. If requirements appear in two places, ambiguity or conflict can be caused by differences of wording. Also there is a danger that a late alteration alters one statement but fails to alter its repetition elsewhere.

The third of the items noted above needs careful consideration, as there may be dangers and liabilities involved in telling the contractor how to go about his work. Some methods may need to be specified, such as the requirements concerning the handling and placing of concrete, but these and similar matters should be specified under workmanship and materials clauses. Other directions on method should be given only if essential for the design. For instance, if it is necessary to under-pin or shore up an existing structure, the exact method used should not be specified for, if the contractor follows the method and damage ensues, the liability for damage may lie on the designer. Usually there is no need to specify a particular method, but there may be a need to rule out certain methods; for example, that the contractor is not to use explosives.

It is important to avoid vague phraseology such as requiring the contractor to provide ‘matters, things and requisites of any kind’, or ‘materials of any sort or description’, etc. d or reasonably to be inferred from the contract.’ Similarly the phrase ‘excavation in all materials’ is ineffectual. The drafter might think it covers any rock encountered but it does not if the geological data supplied with the contract or reasonably available to the contractor provides no evidence of the existence of rock. Definitions such as those used in the Civil Engineering Standard Method of Measurement should be followed.

Repair Of Concrete Columns

Repair Of Concrete Columns

Before starting the repair of a column, the axial dead load, axial live load, horizontal load and its associated moments must be known. Repairs to concrete columns can be divided into two categories. Surface or cosmetic repair only covers local deterioration and structural repair restores or strengthens the affected columns. If the deterioration does not significantly reduce the cross section, the conventional concrete repair can successfully be employed.

Columns may be repaired by using one or more of the following methods:Encasement or enlargement of the column cross section (jacketing). Cathodic protection to stop reinforcing steel corrosion.Realkalization of the reinforcing steel to stop corrosion.Chloride extraction to retard the reinforcing steel corrosion.Confinement using steel plate, carbon, or glass fiber materials.Addition of shear collars to increase the shear capacity of intermediate floors. Addition of a steel plate assembly to increase moment capacity.Supplemental columns.The application of a protection system to prevent future corrosion. Following parameters are important for the design and the execution of the column repair:

Unloading columns

In those cases where the column deterioration is significant, unloading the column is usually required so that the entire cross section of the repaired column is capable of carrying the reintroduced design load. Without this unloading, the new repair will hardly carry any load. Drying shrinkage of new material may further reduce this share of load. Unfortunately, it can be difficult and expensive to unload columns, especially in high-rise buildings. If the existing load on a column is not removed before the repair, the jacket will only provide confinement to the existing column. The percentage of direct load taken by jacket will be very small (less than 25 percent of the jacket strength). If it is not possible to remove the load from the column, then a supplemental column system can provide an alternative method of support in combination with the repair of the existing column.

Redistribution of the load

In case of corrosion of reinforcement and significant concrete deterioration, the load is redistributed in the structure before repair to a new pattern which must be considered while designing the repair. Even the adjoining members may have been affected by this redistribution.

Supplemental reinforcing steel

The column ties can not usually be disturbed during the repair as it may cause buckling of the longitudinal bars. Hence, the supplemental vertical bars may be placed outside the original cage with extra ties. When the supplemental bars are placed outside the tie bars, the column dimensions should be increased to provide adequate cover. Hairpin ties, usually of stainless steel, are used to laterally support the supplemental bars.

Concrete removal

The removal of concrete within a column cage must only be done if the column is unloaded. Otherwise, the longitudinal bars may buckle and compression failure of column may take place.

Corroded reinforcing steel

It is not necessary to remove the corroded reinforcing bar with reduced cross-sectional area if the loss is supplemented with additional reinforcing bars. The lap length of such a splice must be provided corresponding to the area lost by corrosion to either side of the corroded portion of the reinforcing bar that is supplemented. The partially corroded reinforcing bars that are left in place must be thoroughly cleaned by sandblasting to obtain bare metal. The bars with excessive corrosion must be replaced with fresh reinforcement having full laps on both sides.

Corroded ties

The corroded ties can be replaced by adding stainless steel hairpin ties that are anchored into the concrete. It is often necessary to deposit extra material around columns to provide adequate cover over the supplemental ties.

Low-strength concrete

Where the concrete strength is low, resulting in insufficient load-carrying capacity, several alternatives are available:

Shore the column and remove and replace the in-place concrete.Shore the column and increase the size of the column to reduce the bending stresses, and to increase the confinement on already placed weak concrete. Wrap the column with carbon- or glass-reinforced plastic.Install a supplemental column.

Concrete without cement - A Green alternative:

Concrete without cement - A Green alternative:

Concrete without cement is possible with the use of flyash as an alternate for cement. Concrete is the most common material used for construction due to its properties such as strength, durability and easy availability. But cement is commonly used in preparation of concrete.

Cement has excellent binding property but its production requires large amount of energy which contributes for pollution and global warming. The process of cement production starts from mining for raw materials, crushing, blending and heating these materials at high temperature of 15000C and finally creating cement from heated materials.

All the process involved in manufacturing of cement requires large amount of energy, it involves huge costs, contributes to increase in CO2 emissions and other greenhouse gases. The production of cement contributes to 7% of the emissions of greenhouse gases and it is likely to double by the year 2014.

As the demand for more and more infrastructures is increasing day by day, the quantity of cement requirements is also increasing. With this, the control the emissions of greenhouse gases cannot be reduced to prevent global warming.

The green alternative to cement is the use of flyash, which has almost same property as cement, both physically and chemically. Flyash is a byproduct from the thermal power plants. It is a waste product and has no other use in power plants. The use of flyash also reduces the energy demand of cement plants as well as reduces the space required for its dumping thus reducing the environmental impact of both cement concrete construction and thermal power plants.

Flyash has been used in the production of cement known as Pozzolanic Portland Cement (PPC) due to its cementitious properties. Generally 25% of flyash is used in OPC to produce PPC.

The property of flyash produced depends on type of coal being used in power plants, nature of combustion process. And the flyash properties suitable for use in cement can be used for concrete construction.

Research at various places in the world has found that concrete in which cement was replaced with flyash, the concrete without cement offered exceptional performance in short term and long term strength of concrete and its workability relative to use of ordinary Portland cement concrete.