Some useful tips to examine concrete formwork in job site

 The finalized inspection of concrete formwork should be examined prior to set the reinforcement bars in exact location. By implementing perfect form work, honey combing, blow holes, grout less or discoloration of concrete can be circumvented and consequently the finished surface of concrete becomes superior.

Prior to commencement of concreting work, shuttering surface should be fully cleansed and does not contain any defect/deposits in order to provide rightly straight smooth concrete surface. Shuttering surface does not contain any damage and unnecessary roughness to its surface.

While building concrete form work, the following should be examined properly.

1. Any member to be retained in position once the general dismantling is completed, should be labeled perfectly.
2. The applicable materials should be thoroughly examined in order that no incorrect items/rejects are utilized.
3. When excavations exist nearby reformatory and strengthening action should be undertaken to impact the safety of form work.
4. The quality of bearing soil should be strong and it should be arranged properly and the sole plates should bear well on the ground. Sole plates should be perfectly placed on their bearing pads or sleepers. The bearing plates of steel props should not be deformed. There should be adequate bearing areas for the steel sections on the bearing members.

5. There should be proper safety provisions to get rid of impact of traffic, scour caused by water and accidental impacts.
6. To maintain proper strength and durability of form work at intermediate stage, bracing, struts and ties should be provided together with the advancement of form work. Avoid ‘Tilting and overturning of steel sections.
7. While applying customizable steel props, no damage and evident bents should be observed; steel pins should be arranged, restricted latterly near each end.
8. Screw adjustments of adaptable props should not be over extended.

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Published By
Rajib Dey
www.constructioncost.co
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Types, applications and benefits of aggregates

 Aggregates are the vital components in concrete. They are granular materials obtained from the natural rocks, crushed stones as well as natural gravels and sands. The aggregates are amalgamated with a binding material in fixed ratios to form concrete.

Aggregates normally capture about 70% to 80% of the concrete volume and they significantly affect the different properties like strength, hardness and stability of the concrete. Aggregates function as fillers or volume increasing components.

Applications of aggregates:

1. They are used as an underlying material for foundations and pavements.

2. They are used as constituents in portland cement concrete & asphalt concrete.

Properties of Aggregate: Aggregate should contain the properties given below -

1. It should be chemically static that means they should not respond to cement or any other aggregate or admixture.

2. It should contain adequate hardness to avoid scratching and erosion in the hardened state.

3. It should contain adequate toughness to sustain impact and vibratory loads.

4. It should be physically strong to carry compressive and normal tensile loads in ordinary mixture.

5. It should not contain impurities, inorganic or organic in nature for which the quality of concrete will be affected significantly.

6. It should have capabilities to produce usable plastic mixture after getting mixed with cement and water.

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Published By
Rajib Dey
www.constructioncost.co
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Step-by-step guidelines to calculate the volume of a trapezoidal footing

 Isolated footings alias pad or spread footings are mostly found in shallow foundations with the intention of conveying and distribution of concentrated loads resulting from columns or pillars. Isolated footings either comprise of reinforced or non-reinforced material. For the non-reinforced footing, the height of the footing should be larger to maintain the required spreading of load.

To apply Isolated footings, there should not be fluctuating settlements under the whole building.

Necessity of materials for Isolated Footing : The following materials will be utilized for building up a isolated footing - Shutter Material, MS Rod, Binding Wire, Cover Block and Chair, Concrete.

Shutter Material for Isolated Footing: In isolated footing, generally wooden shutter materials are utilized. Often, steel shutter materials can also be applied.

This type of footing is utilized under the following conditions : Columns are not arranged narrowly. Fewer loads enforce on footings. The safe bearing strength of the soil is usually extreme.

In this construction video tutorial, one will learn how to make calculation for finding out the volume of Trapezoidal Footing at construction site.

Trapezoidal footing is formed by combining cuboid & truncated pyramid. Cuboid may be rectangular or square in shape. A special case of footings is the trapezoidal footing that may be utilized to bear two columns of unbalanced loads when distance outside the column of the massive load is restricted.

A trapezoidal footing is applied in such a manner that the center of gravity of the footing is located under the outcome of the loads. In that order, the distribution of contact pressure will be consistent.

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Published By
Rajib Dey
www.constructioncost.co
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Some useful tips to work out the length of the bent bars

 While fabricating reinforcing bars with bends, the straight bar is primarily cut to a length that is under the sum of the specified dimensions of the bent bar.

The variation among the detailed length and the cut length belongs to the “bend curvature deduction” and called as various names like gain, creep, and gyp. Usually, the fabricators and programmers get the bend curvature deduction from a bend deduction table.

In the following table 1, the deductions for 45- and 90-degree bends of common bar sizes are provided.

Figure 1 illustrates a No. 8 (No. 25) bar with a standard hook and sides estimating 1 ft 4 in. and 4 ft (400 and 1220 mm). The detailed length of this bar is obtained by summing up the two sides, or 5 ft 4 in. (1620 mm). From Table 1, the deduction for a 90-degree bend on a No. 8 (No. 25) bar is 2-1/2 in. (65 mm). So, in such a case, the cut length of the bar should be 5 ft 1-1/2 in. (1555 mm).

The usual standard for working out the cut length of a bar is along the actual centerline of the bar, that is equivalent to the neutral axis of the bar cross section before bending. The cut length of a bent bar is less than the sum of the finished dimensions due to the following reasons :-

with a easy-to-follow mathematical calculation.

If the exterior fibers of the bar are elongated easily, the inner fibers of the bar are constrained by friction against the bending mandrel, so, the neutral axis shifts inward approaching the mandrel. It is critical to measure this component. The inconsistency arises from computing the lengths on the basis of the actual centerline is not very important.

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Published By
Rajib Dey
www.constructioncost.co
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What are the maximum bearing capacity of various types of soil

 In this construction video tutorial, one will be familiar with how to determine maximum bearing capacity of various types of soil.

Safe Bearing Capacity of Soils is defined as the maximum strength of loading that the soil will bear securely devoid of the risk associated with shear failure.

The bearing capacity of soil refers to the maximum average contact pressure among the foundation and the soil which should not lead to shear failure in the soil.

In the jobsite you will be provided with drawings along with soil investigation report. From soil investigation report, you can get various information about the soil upon which the building will be constructed like number of fillings in the soil, the bearing capacity of soil, bearing pressure of soil to undergo.

There may be some errors in the report or higher value for bearing capacity.

In this video, you will learn how to find out maximum bearing capacity of soil and tally this figure with the soil test report to check for any discrepancy.

In the video, there are two heads like soil type and safe bearing capacity of soil. In soil type, there are different types of soil like combination of soft, wet and muddy clay, fine/loose or dry sand, soft clay, black cotton soil, moist or sand clay mix, loose gravels, compacted gravels, soft rock, sand or lime stone, hard rock/granite/trap etc. For each type of soil, the maximum safe bearing capacity is provided.

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Published By
Rajib Dey
www.constructioncost.co
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Some useful tips to measure loads on column, beam and slab

 In order to work out the total load on columns, Beam and Slab, there should be clear ideas on the types of loads enforcing on the column.

Different Loads operating on Column:

1) Column Self Weight X Number of floors
2) Beams Self Weight per running meter
3) Load of walls per running meter
4) Total load on Slab (Dead load + Live load + Self weight)

Apart from above loading, the columns are also susceptible to bending moments which should be taken into consideration in the final design.

For Colomn: The Self weight of Concrete remains approx 2400 kg/m3, that is similar to 240 kN and self weight of steel is approx 8000 kg/m3.

Therefore, if we consider a column size of 230 mm x 600 mm with 1% steel and 3 meters standard height, the self weight of column is approx 1000 kg per floor that is equivalent to 10 kN.

At the time of making calculation, self weight of columns is taken as 10 to 15 kN per floor.

For Beam: Similar method is also used for making calculations of beam. Suppose, each meter of beam contains dimensions of 230 mm x 450 mm without slab thickness. Therefore, the self weight should be approx 2.5 kN per running meter.

For Walls: The Density of bricks differs among 1500 to 2000 kg per cubic meter. For a brick wall with thickness 6 inch, height 3 meter a length 1 meter. The load / running meter should be equivalent to 0.150 x 1 x 3 x 2000 = 900 kg, that is identical to 9 kN/meter. This method is useful for working out the load of brick per running meter for any brick type.

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Published By
Rajib Dey
www.constructioncost.co
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How to Test the Consistency of Cement

 Definition: The standard consistency of cement paste is the level of water required, where the plunger infiltrates into the cement paste of about 5mm to 7mm from the base of the shape and in the other word consistency of cement is the base measure of water required to start a synthetic response among water and cement to frame a paste.

A Minimum quantity of water required to initiate the chemical reaction between water and cement to form a paste is known as consistency of cement. The cement consistency which will allow the Vicat plunger to penetrate to 5-7 mm point from the bottom of Vicat mould is known as standard consistency. For reference purposes, the standard consistency of a Portland cement fluctuates between 25–35%.

Significance: We as a whole realize that the strength of concrete relies upon the quality Cement. To get the necessary cement strength, we need to include the perfect measure of water. Water underneath standard security won't start the concoction response among water and cement, which will build the strength of cement.

Water less than the standard consistency would not initiate the chemical reaction between water and cement resulting in the strength of cement. Water more than the consistency results in excess water and strength reduction. That’s why it is important to know the standard consistency of cement material. On the other hand, overabundance of water over steadiness brings about abundance moisture and loss of strength. In this manner it is essential to know the standard consistency of cement.

Different tests on cement:

1. Fineness test of Cement by dry sieving method with 90 micron strainer
2. Adequacy test of cement by Le Chatelier

Reasons for the Test: We know that the cement we used on our site is mostly affected by the following

1. Weather Conditions.
2. Excessive combination of Silica. One of the cement ingredients which determines the initial and final setting time of cement paste.
3. The fineness of cement.
4. Manufacturing Defects.

By Standardising the consistency of cement, we know how much water is required to produce an effective cement which will eventually produce good quality concrete. Standard Consistency of an ordinary Portland cement varies between 25-35%. That means we need 25% of water in volume to make a standard consistency of cement.

For Example, If we need to calculate the amount of water required for a 200 g of cement which has 30% consistency means then we need 200*30% = 60g water to prepare a standard consistency. This is what we are going to find in this test.

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Published By
Rajib Dey
www.constructioncost.co
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Importance of mortar in brickwork construction

In brickwork construction, different types of mortars like M1, M2 etc. are applied. Normally, lime mortar and cement mortar are frequently utilized for brickwork. The characteristics, strength and applications of these mortars are discussed below :-

Consideration should given on the following factors for Mortar in Brickwork Construction :-

1. The strength of brickwork is not affected by the grade of the mortar used, i.e. several mortar mixes of diverse grades like M1 and M2 contain dissimilar strengths, but the strength of brickwork is not compromised. As for instance, mortars of mix ratios 1:6 and 1:4 provide equivalent strength of brickwork with the similar type of bricks, while they contain different strengths. It signifies that the strength of brickwork is based on the strength of bricks.

2. If the mortar mix ratio of 1:3 is applied for cement to sand or (cement + lime) to sand ratio, a solid mortar is produced with less voids.

3. Benefits of Lime Mortar – As the strength of lime mortar is under cement mortar, inclusion of lime in mortar brings the following benefits:

• Shrinkage in mortar is fewer, thus less susceptible to cracks because of shrinkage.
• The workability and plasticity of the mortar mix is enhanced with lime.
• Lime contains superior water retention strength and does not vaporize rapidly. Besides, dry bricks can’t absorb water from the lime mortar.
• Lime raises the volume of mortar and fills the voids so that it becomes water resistant against rain infiltration.
• Lime mortar can bond with bricks efficiently.
• Cement-lime mortar is more flexible and can adjust the normal movements of brick masonry without causing cracking. So, normally, cement lime mortar less susceptible to cracking as compared to cement mortar.

4. Lime mortar attains strength gradually and contains lower ultimate strength as compared to cement mortar. Besides, lime mortar with hydraulic lime can get superior and early strength. Lime mortar with fat lime does not consolidate at all in wet locations. While applying fat lime, some pozzolanic materials like burnt clay should be utilized instead of sand to enhance the strength of mortar.

5. Cement-lime mortar of leaner mixes from ratio 1:4 to 1:8 becomes rough specifically when the sand is coarse and not graded. Consequently, plasticizers should be utilized for better workability and plasticity of the mortar.

6. The strength of cement mortar is impacted by the following factors for the same ratio of cement and sand:

a. Grading of sand
b. Fineness and coarseness of sand
c. Angularity and roundness of the sand particles

7. If fineness of sand is raised, the workability of the cement-mortar mix is also increased. On the other hand, the surface area of the sand is also increased for which requirement for cement and water quantity for the same strength is also increased.

The strength will be reduced when the cement quantity is not raised. To attain the required workability, adequate water is necessary. This condition raises the water-cement ratio and as a result the strength is decreased.

8. Curing plays an important role to attain the maximum strength as well as maximum coating of the obtainable cement around sand particles.

9. Mortar beyond a mix ratio of 1:3 should not be applied in brickwork masonry construction due to high shrinkage and no considerable increase in strength of masonry, although the strength of mortar itself raises.

10. Overly thick joints decrease the strength of the brickwork.

11. Inclusion of pozzolana enhances the strength of the mortar as well as resistance capacity against chemical attacks.

Read more

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Published By
Rajib Dey
www.constructioncost.co
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