adsense analytic

Monday, November 12, 2018

Benefits of post-tensioning concrete slabs in building

Post-tensioned concrete slabs in buildings provide various benefits over reinforced concrete slabs & other structural systems toward both single and multi-level structures. Described below, some of the advantages of the slabs :-

Longer Spans: Longer spans are utilized to lessen the number of columns. It leads to bigger, column free floor areas which significantly enhance the adaptability of application for the structure as well as leads to greater rental returns.

Entire structural cost: The complete cost of materials, labor and formwork which are essential to build up a floor is decreased for spans higher than 7 meters and consequently leads to huge cost savings.

Minimized floor to floor height: Thinner slabs are utilized for the similar imposed loads. The decreased section depths facilitate least building height together with consequent savings in facade costs. As a substitute, toward bigger buildings, it facilitates more floors to be developed inside the original building envelope.

Deflection Free Slabs: Unwanted deflections under service loads are virtually removed.

Water-resistant slabs: Post-tensioned slabs are designed to remain free from cracks and as a result water-resistant slabs should be formed with proper design, detailing and construction. The selection of concrete mix and curing method together with standard workmanship are also very important.

Early formwork stripping: The earlier stripping of formwork and curtailed backpropping requirements facilitate rapid construction cycles as well as fast reprocessing of formwork.

Materials Handling: The decreased material quantities in concrete and reinforcement significantly offer benefit to on-site carnage requirements. The stability of post-tensioning strand is roughly 4 times that of traditional reinforcement. So, the whole weight of reinforcing material is considerably minimized.

Column and footing design: The decreased floor dead loads are applied to create cost-effective design of the reinforcement concrete columns and footings. In multi-storied buildings, decreased column sizes may raise the floor net rentable area.

Benefits of post-tensioning concrete slabs in building

Read more

Published By
Rajib Dey

Tuesday, November 6, 2018

Some vital points to be remembered before purchasing ready mix concrete

The ready mix concrete is better as compared to the ordinary concrete mix since it needs less labour, time, efforts and cost. It facilitates to retain homogeneous quality during the work and provides the high speed of concrete construction.

With ready mix concrete, various types of issues like inferior workability, segregation, and bleeding, inappropriate water cement ratio, insufficient mixing time can be easily resolved in the construction site.

Prior to order ready mix concrete, the following points should be taken into consideration :-

01. Grade of Concrete or Mix Design

• Types of work where the concrete will be poured i.e. foundation slab, floor slab, pavements, etc.
• Grade of concrete necessary on site, i.e. M15, M20, M25, M30, etc.
• Slump of concrete both at the batching plant and at the job site.
• The quantity of concrete in cubic meter or cubic yard.
• Address or place of concrete pouring.
• Time of requirement of ready mix concrete on site.
• Time of interval among the two consecutive deliveries of RMC (in the case of higher quantity i.e. exceeding 6 cubic meter).

02. Fly Ash should not be used extra: It is essential to get the proper ratio of fly ash in the concrete. Some RMC producer includes extreme amount of fly ash in concrete which aren’t suggested also by the standards.

Generally, the fly ash is added in concrete at levels which vary from 15% to 25% by mass of the cementitious material component. Plant owner accomplishes this so that the cost is decreased and the profit is raised. So, the purchase should be careful for buying RMC at lower rates, and not get deceived with this lower rates.

It is also essential to get the source of every concrete ingredients (cement, aggregates, admixture, and water), the ratio and quantity of the concrete material per cubic meter, and the types of admixtures applied in RMC. So, prior to give order for ready mix concrete, obtain the above information. i.e. details of mix design from dealer.

03. Source of materials: The RMC dealers buy various concrete materials from diverse sources. The quality of materials may not be always good. So, all the sources should be assessed carefully. If their sources are recognized in the local market for the quality, then the ready-mix dealer can be selected, who will purchase the concrete materials from those renowned sources.

04. Time for Transportation: According to IS 4926:2003, it is recommended to pour the ready mix concrete within 2 hours from the time of loading at the central batching plant. However, a higher period is allowed if retarding admixture is utilized. But, determine the type of retarder used and all steps are followed as suggested by retarding manufacture.

05. Application of Admixture: Sometimes the extra dose of admixture is included at the project site to retrieve the workability of concrete. Some admixtures have chlorides, and if so, it is required to get the amount of chloride content in percentage of the total mass of admixture. If the amount of chloride is increased in ready mix concrete, it will lead to corrosion of the reinforcement steel and the service life of the house or building will be significantly affected. Hence, such admixtures should not be used.

06. Test of Concrete: It is indicated in standards that the ready mix concrete dealers should arrange test facilities at its premises to conduct routine tests, i.e. concrete slump test, concrete cube testing, etc. So, it is possible to double check the workability and strength of ordered concrete.

The workability of concrete can also be verified with slump test on site. Slump of concrete is primarily based on the condition of placement and the requirement of degree of workability. According to IS 456:2000, low reinforced sections like slabs, beams, walls, columns, etc. are casted with the slump of 25 to 75 mm. Heavily reinforced sections like slabs, beams, walls, columns, etc. are casted with the slump of 50 to 100 mm. From slip form work or pumped concrete, the appropriate slump of concrete is 75 to 100mm.

07. Information about Delivery Ticket of Ready Mix Concrete

The information given below, should be providedd in the ready mix concrete delivery ticket for each batch:

• Name and number of the ready-mixed concrete plant.
• Date and serial number of the ticket
• Truck Number
• Name of the purchaser and location of the site
• Grade of concrete
• Mix design details
• Type and size of concrete ingredients and their weight in table format.
• The quantity of concrete in the cubic meter
• Time of loading
• Slump results at the batching plant
• Signature of the concrete plant operator

The information given below, is required to be filled on ready mix concrete ticket on site.

• Time of arrival on site
• The time when discharge was completed
• Any water/admixture added on site
• Location of pouring of concrete
• Slump test result at the site
• Signature of RMC receiver

Some vital points to be remembered before purchasing ready mix concrete

Read more

Published By
Rajib Dey

Monday, November 5, 2018

How leftover concrete casting structures are used to reduce project cost

In high-rise building projects, the construction materials significantly contribute to find out the value of a project, the profit and loss of the project, even in the acceleration of the project's time.

Concrete is the prime material that is frequently utilized in multilevel projects as it is user-friendly, strong, and cost-effective.

The concrete that is utilized recurrently wasted in the process because of several errors in the execution of casting. The factors that influence the wasting of The ready mix concrete is wasted due to several factors like miscalculations / calculations in the job site, impaired equipment, awful weather, as well as inaccurate application processes.

Given below, some useful guidelines to utilize the remaining concrete casting structures so that the expenditure of a project is reduced significantly.

Utilized as a practical column or precast lintel beam.

In some big projects, practical columns or lintel beams on the wall installation work already apply precast methods. Generally, the concrete applied is instant concrete with K-225 or K-250. It is suggested that the residual structural casting concrete should be employed to minimize the waste of concrete and purchase instant concrete.

Utilized as Cansteen: Cansteen stands for edge of the pedestrian, the sidewalk, the separator, the edge of the road, the park, the boulevard, and so on. It acts as a booster for the road. Normally, cansteen is budgeted in BQ ordering finished products just by precast. The leftover structural casting concrete is utilized as a cansteen to reduce the budget.

Utilized as a Car Stoper: Car stopper belongs to the embankment in the safety parking area for providing to stop any car. Different types of materials like iron pipes, concrete and rubber are normally applied as car stopper.

Utilized as Paving Block: Paving blocks usually applied as outdoor parking areas, jogging tracks, parks, sidewalks, home yards and pedestrians are made precast with the rest of the concrete casting structure.

Some of the application of the remaining concrete casting structure which if employed can minimize project costs should be carefully examined and controlled effectively in the arrangement of the material as without that it will confine the project loading dock area that impacts the disruption of work execution.

How leftover concrete casting structures are used to reduce project cost

Read more

Published By
Rajib Dey

Saturday, November 3, 2018

How to measure the land area for irregular & large land tracts

Various types of surveying methods are used for conducting survey of irregular and large land tracts. Some methods are easily understandable and based on elementary geometry, others are complicated and may contain GPS and satellite imagery.

In this article, useful information is given on various options and technologies accessible to the surveyor.

The calculation should be done for Land for different purposes like prior to purchase, while performing stock taking, erecting a boundary wall, controversy with a neighbor over demarcation, etc. Making calculation for regular land area is simple since they contain mostly rectangle or other geometrical shapes. Recalling geometry studied in High School we can do the measurements and arrive at the results. But, the process becomes difficult for measurement, if the area of land is extremely irregularly shaped or large tracts of land are purchased like a farm measuring miles across.

In this article, you will be familiar with some self-reliant methods of calculating your land and some high technology solutions.

Given below, some useful methods for measuring the land with simple geometry, maps and planimeter, GPS, Aerial photography, Satellite imagery, Google earth, maps and graphs, measuring wheels.

Geometric Method: Under this method the odd shaped plot is surveyed and plotted over graph paper. The area of the plot is then subdivided into geometric figures and the areas of these figures are measured with formulae.

Initially, the greater size geomatric figure that can be perfectly drawn in the map is created and after that smaller shapes are produced unless the complete space is captured more or less.

Once the computation for areas of these figures is done, then these are added to determine the total area.

As for instance:
Area of Rectangle: Length x Breadth
Area of Square: Length x Length
Area of Triangle: 0.5 x Base x Height
Area of Trapezium: 0.5 x (Length 1 + Length 2) x Height
The above formulas are used to find out the exact area.

Planimeter on Map: Planimeter is a small gadget that is utilized for working out the areas of a graphically represented planar region. The planimeter can calculate all regular and irregular shapes. It is required to pivot it at any point and then run the end pin all over the perimeter of the area to be calculated. It contains a compliant linkage that facilitates it to move devoid of any effort in all directions.

How to measure the land area for irregular & large land tracts

Read more

Published By
Rajib Dey

Friday, November 2, 2018

Dewatering system at job site

Dewatering refers to a method that is applied to extract groundwater confined inside the soil of the construction site to make the foundation long-lasting.

Under this method, the water is released through storm drains, municipal sewer system and irrigation purposes.

The following methods are mostly used for dewatering :-

1. Open dewatering
2. Well point dewatering
3. Deep well dewatering
4. General sump pumping

Open dewatering system: It allows one to reduce the ground water table adequately in cohesive and low penetrable soils. Water is drained directly from sumps (ditches) along the toes of the slopes from the excavation works.

Well point dewatering system: It is performed by gravity or vacuum. This system allows one to reduce the ground water table adequately for deep and large construction. The water from high penetrable soils is drained from well points, set up along the trench of the site.

Deep well dewatering: This system allows one to reduce the groundwater table to substantial depth. A submersible pump is set up at the bottom of the well with casing containing a minimum 150 mm dia. The discharge pipes from the submersible pump of a number of adjoining wells are attached to a common delivery main. The water is uplifted from the well with the help of multi-staged pump.

General sump pumping: Sump pumps are suitable where excess water is drained from a specific area. They usually rest in a basin or sump that accumulates this excess water. This classification contains bilge and ballast pumps, centrifugal pumps, cantilever pumps, sewage pumps, submersible sump pumps and utility pumps.

To get more details, go through the following article

Dewatering system at job site

Published By
Rajib Dey

Thursday, November 1, 2018

Some useful guidelines to work out the dry volume of mortar

The dry volume of mortar is measured for determining the quantity of cement and sand for the formation of mortar for our masonry work.

In recent times, cement mortar is frequently utilized for different types of masonry work.

While making estimate of the volume of mortar for various types of masonry works, only the wet volume is obtained. In order to find out the necessary volume for cement and sand, the wet volume of mortar should be changed into the dry volume.

The Dry Volume of Mortar
The prime components of mortar are cement and sand.

The mortar is formed with the inclusion of water to the dry mix of cement-sand.

After adding the water to the dry mix of cement-sand, the volume of dry mix is decreased because of the existence of air voids in sand particles.

Since the volume of mortar is raised in dry conditions, it is required to multiply the wet volume with 1.30 to obtain the dry volume of mortar.

How to work out the volume of cement and sand in mortar.

Suppose, 10 cubic feet wet mortar is required and the proportion of cement and sand in the mortar is 1:4.

Given below, the detail process to work out the dry volume mortar and then sand and cement quantity for this 10 cubic feet mortar.

How to work out the dry volume of mortar
It is known that the dry volume of mortar is,
= Wet volume of mortar x 1.30
=10 x 1.30
=13.00 cubic feet.

The process for measuring cement and sand volume in mortar

The proportion of cement and sand in mortar is 1:4. It means one unit of cement will be blended with four units of sand.

Total units of elements in mortar are 1+4=5.
Therefore, the necessary volume of sand for the projected mortar quantity is,
= (13.00 ÷ 5) × 4
= 10.40 cubic feet.

Categories of chains applied in surveying:

And necessary cement quantity is,
= (13.00 ÷5) x 1
= 2.60 cubic feet.

Conclusion: To measure the dry volume of mortar, it is required to calculate the wet volume of mortar for your work item and then multiply that wet volume by 1.30.

As soon as you obtain the required dry volume of mortar, then it is possible to compute the required cement and sand quantity for the mortar on the basis of the mix proportion.

Some useful guidelines to work out the dry volume of mortar

Read more

Published By
Rajib Dey