External Plastering Work Checklist - To follow in Building Construction

The external plastering work in a building project is a pretty important work because it provides the outer finish of the building. Not only that, it is the foundation for the building’s aesthetics. For these reasons, every constructor should keep in mind some basic steps in order to do it right. As such, the following checklist can be very helpful in external plastering work in building construction.

1. Clean the surface: Make sure that the external surface of the building is clean. That means the block or brick masonry and concrete surface. These should be clear of dust, oil grease, loose materials, mortar dropping, nails, wood, metal strips, etc. You should have an even, smooth surface to work on. Otherwise the bonding will not work.

2. Make scaffoldings: You need to erect a scaffolding in order to reach the entire outside surface. Conversely, you might be needing a double scaffolding as well. You have to do this without making a hole in the wall. Since in this phase you must not damage the wall in any way. However, if authorities permit, you can take support from other parts of the building.

3. Mortar and socketing: The gaps between the masonry and the beams that show on the outside needs to be filled with rich mortar. Also, you need to finish out the socketing works.

4. Chicken mesh: Then, fix a chicken mesh on the joint of RCC and masonry wall. The mesh should be 6 inches wide. Nail this mesh at 230mm intervals only.

5. Plumb measure: Use the plumb (also the line) from top to bottom to ensure the accuracy of the plastering.

The plastering here should be of a single coat of 10-12mm only. Also, you must check all the edges.

6. Handle jutting out stuff: Sometimes, a beam or a column, or other parts of construction may be budging out of the plastering. In this case, first take approval of the designer to see if you can break it off. If you can, then use a sharp chisel or hammer to break off the jutting-out portion. Also, you can use a concrete breaker in this. Do take care that it doesn’t hurt any other part of the building.

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What is Portland Cement and How is it Used in Construction

What is Portland Cement

The Portland Cement is a particular type of cementing material used in building construction. It is essentially an amalgamation of clay and chalk. This blend, when subjected to water, hardens up and when it is hard, mimics the portland stone in color. The Portland Stone is found in quarries in Portland, Dorset in England initially. This type of hydraulic cement was patented in 1824.

The portland cement is exceptional in giving strength to structural properties. Most commonly, it is used in making concrete. However, the portland cement can also be directly used in creating stucco or be used as a mortar. Some non-specialty grout also uses this type of cement as one of the main ingredients.

ASTM 150 defines the Portland Cement as “hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers which consist essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition.”

How is Portland Cement Made

Usually created from heating limestone and clay minerals in a kiln, portland cement needs a little bit of gypsum in it to give it the desired setting qualities and to prevent flash setting. The chemical constituents of portland cement and their ratio are as follows:

1. Calcium oxide (61-67%)
2. Silicon dioxide (19-23%)
3. Aluminum oxide (2.5–6%)
4. Ferric oxide (0–6%)
5. Sulfur oxide (1.5–4.5%)
6. Gypsum (2-10%)

The Mix is generally a thin, light powder. Depending upon the ratio of materials in the clinker and the cement, this powder can be gray, white or something in-between. The most common form, called the OPC, displays a soft gray color. After hardening, it resembles the portland stones found in Dorset.

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M Sand Vs River Sand - Which sand is better for Construction?

M Sand or Robo Sand is gaining popularity due to ecological factors and insufficient number of superior quality river sand

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Method of silt content test

Sand is considered as one of the vital construction materials for concrete, plastering, brickwork and flooring. Therefore, it is always recommended to use standard quality sand in the construction works.

To check the quality of sand, silt content test should be conducted. Silt content stands for a fine material that is lower than 150 micron. It becomes unstable in the existence of water.

When silty sand is applied for bonding, the strength will be decreased and rework should be required. It is mostly found when the plastering is going on for roof where the plaster continuously peels off at the time of being plastered with the mortar.

Extreme quantity of silt decreases the bonding of cement and fine aggregates as well as hampers the strength and stability of work.

In the job site, it is required to carry out silt test for each 20 Cum of sand although it may differ.

Silt Content Test for Sand

Purpose: Determine the silt content in sand (fine aggregate).

Necessary Tools:

• 250 ml measuring cylinder
• Water
• Sand & Tray

Test Method:

• Initially, the measuring cylinder should be filled with 1% solution of salt and water up to 50 ml.
• Include sand to it unless the level goes to 100 ml. Then fill the solution up to 150 ml level.
• Cover the cylinder and shake it properly.
• Once 3 hours are completed, the silt content settled down over the sand layer.
• Now record the individual volume of silt layer as V1 ml (settled over the sand).

• Then record the sand volume (underneath the silt) as V2 ml.
• Apply the method twice to obtain the average value.
• Silt Content = V1 / V2 x 100

The allowable silt content in sand percentage should be only 6%.

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Common Defects In Plastering

Several types of defects are found in plastering work which range from blistering, cracks, efflorescence, flaking, peeling, popping, softness and uneven surfaces. When these defects are visible, they should be repaired instantly.

Types of Defects in Plastering :-

1. Blistering of Plastered Surface: Blistering of the plastered surface is happened when small patches are expanded outside the plane of the plastered surface. Blistering is visible for plastered surface inside the building.

2. Cracks in Plastering: Cracks are developed on the plastered surface. Two types of cracks are found i.e. hairline cracks and wider cracks. The hairline cracks can’t be seen easily whereas the wider cracks are observed easily. The formation of fine cracks is termed as crazing.

Cracks on a plastered surface occur because of thermal movements, discontinuation of surface, structural defects in the building, defective workmanship, too much shrinkage etc.

3. Efflorescence on Plastered Surface: Efflorescence is developed on plasters when soluble salts are found in plaster making materials and building materials like bricks, sand, cement etc. Even water applied in the construction work may include soluble salts.

When a wall (newly built up) dries out, the soluble salts are provided to the surface and they become visible in the form of a whitish crystalline substance. Such a growth is defined as efflorescence and the adhesion of paint with the wall surface is severely damaged with it.

Efflorescence provides a very ugly appearance and can be eliminated slightly through dry-bushing and washing the surface frequently.

4. Flaking: The development of a very small loose mass on the plastered surface is called flaking and it is mainly occurs because of bond failure among consecutive coats of plaster.

5. Peeling: In peeling, the plaster from some section of the surface are detached and a patch is developed. Peeling is primarily occurred because of bond failure among successive coats of plaster.

6. Popping: Sometimes the plaster mix comprises of particles which get bigger on being set. A conical hole in plastered surface is created in front of the particle. This conical hole is termed as blow or pop.

7. Irregular Plaster Surface: Irregular surface defect becomes apparent because of substandard workmanship of the plastering work.

8. Softness of the Plaster: The extreme dampness at specific points on the plastered surface transforms that section soft. The softness mainly happens owing to unnecessary thinness of the finishing coats, existence of deliquescent salts, extreme suction of the undercoats etc.

9. Rust Stains on Plastered Surface: Rust stains are sometimes visible on the plastered surface specifically when plaster is provided on metal lath.

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How to measure the volume of silt content in sand

In this civil engineering video tutorial, you will learn some vital tips to work out silt percentage in sand or course sand to ensure that whether the sand is eligible to be used in concrete or not. It is recommended that the percentage of silt content of sand in concrete should be over 6%.

The silt stands for a very fine particle and the size of it is under 150 Microns. Silt content can be shrinked and inflated because of the weather condition. Therefore, it can impact the strength of the structure.

Impacts of Silt:

1. Crack will be created on concrete. (some cracks are found in the wall)
2. Silt content includes evaporated matters and salts. (mortar will be exposed at the time of plastering)
3. It engrosses more water. (broadened & shrink owing to the weather condition.

To determine the percentage of silt conent, the following items will be required :-

a. 250 ml, measuring cylinder
b. Course or fine sand
c. Water
d. Sand

The calculation is done as follow - Initially, it is required to area of cylinder as the cross sectional area from top to bottom will be same for the cylinder.

Area of cylinder = πr2 x Height

Suppose, the cylinder is filled with sand up to 100 ml, then water is added up to 50 ml. So, total volume will be 150 ml. Then, shake the bottle and wait for 2 hours. Now, it is found that the percentage of silt content in the sand is 5 ml. You can check the percentage of silt content in the following way :-

= Volume of silt (taken as V2) / Volume of sample (sand or course sand; taken as V1) x 100
= 5 / 100 x 100 = 5%

To get more information, watch the following video tutorial.

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Different grades of Ordinary Portland cement

Ordinary Portland Cement(OPC) is extensively utilized in the construction sectors as primary component for developing concrete, mortar, stucco, and non-specialty grouts. Ordinary Portland Cement is graded on the basis of its strength. The grade specifies the compressive strength of the mortar cube that will be achieved once 28 days of setting is completed.

Grades of Ordinary Portland Cement - The following grades of OPC are available:

1. OPC 33 Grade Cement: This grade of cement is suited for general construction under normal ecological condition.

Compressive Strength of OPC 33 – The average compressive strength of minimum three mortar cubes with a face area of 50 sq.cm is considered at the time of verifying the compressive strength. These mortar cubes comprise of one part of cement and three parts of standard sand.

Compressive Strength of OPC 33:

a) 72 +/- 1 hour = Not under 16 N/mm2
b) 168 +/- 2 hours = Not under 22 N/mm2
c) 672 +/- 4 hours = Not under 33 N/mm2

IS Code – IS 269 : 1989 for Ordinary Portland Cement, 33 Grade.

2. OPC 43 Grade Cement: Now-a-days, this grade of cement is gaining popularity in the construction sectors. OPC 43 is suitable for general RCC construction where the grade of concrete is up to M30. It can also be applied for the construction of various precast items like blocks, tiles, asbestos products like sheets and pipes, and for non-structural works like plastering, flooring etc.

Compressive Strength of OPC 43:

a) 72 +/- 1 hour = Not under 23 N/mm2
b) 168 +/- 2 hours = Not under 33 N/mm2
c) 672 +/- 4 hours = Not under 43 N/mm2

IS Code – IS 8112: 1989 for 43 Grade Ordinary Portland Cement.

3. OPC 53 Grade Cement: OPC 53 is useful while requiring concrete with greater strength at very reasonable cement content. OPC 53 facilitates 8 to 10% saving of cement in concrete mix design, for concrete M20 and over.

This cement grade is very effective for specialized works like pre-stressed concrete components, several precast items like paving blocks, building blocks etc, runways, concrete roads, bridges, and other RCC works where the grade of concrete remains M25 and over.

Compressive Strength of OPC 53:

a) 72 +/- 1 hour = Not under 27 N/mm2
b) 168 +/- 2 hours = Not under 37 N/mm2
c) 672 +/- 4 hours = Not under 53 N/mm2

IS Code – IS 12269 : 1987 for Specification for 53 grade ordinary portland cement.

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Brief overview of metal casting

Casting means development of hot liquid metals or several metals which are cooled after obtaining the constituents like clay, plaster and concrete mixed in. This method is also utilized in forming cars or planes.

Various types of castings are found in construction industries. Given below, the detail lists of them :-

Non-expendable mold casting - This type of casting is categorized as continuous, centrifugal, die, and permanent casting.

Continuous casting - It is utilized as a superior procedure of casting for high-volume, continuous production of metal sections with constant cross-section. Here, the liquefied metal is poured into a water-cooled and open-ended copper mold. It offers a layer of solid metal to be developed over the still-liquid centre.

Continuous casting is very economical and hence it is mostly recognized among construction professionals. The metals incessantly casted are aluminum, copper, and steel.

Centrifugal casting - This option is not influenced by both-pressure and gravity since its own force feed is constructed by means of utilizing a temporary sand mold in a spinning chamber. The completion time fluctuates with regards to the application itself. True-and-semi-centrifugal processing facilitates 30 to 50 pieces to be finished every hour.

Die-casting – It is most crucial of all the methods, Under this method, the melted metal is forced into cavities of mold in high pressure. These castings include non-ferrous metals, especially-alloys of aluminum, copper, and zinc.

Sand casting – It is considered as the most convenient and most recognized casting types. It entails very small size operations. Here, the bonding of sand occurs with the use of clays. The process can be initiated prior to recycling.

Plaster casting - It is also applied extensively and is closely equivalent as sand casting, excluding plaster.

If it is required to construct your own metal works, just consult with a brand or professional relating to equipment and safety tips.

Source: civilengineersite.com



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Some useful terms and definition used in brick masonry

Brick masonry is applied for developing buildings and other structures by bonding brick stone, stone blocks, brick blocks with various types of masonry.

For temporary sheds mud mortar is suitable but for all permanent buildings lime or cement mortars are utilized.

Different terms and definitions associated with Brick Masonry:

Course: A course refers to a layer of the same unit that runs parallel in a wall.

It is also described as a continuous row of any masonry unit like bricks concrete masonry units (CMU), stone, shingles, tiles, etc.

Bed: It belongs to the surface of stone vertical to the line of pressure. It specifies the lower surface of bricks or stones in every course.

Back: It is the inward surface of a wall that is not uncovered. The material that is used to develop the back is called backing.

Face: The outside of wall uncovered to weather is called face. The material that is utilized in the face of the wall is named as facing.

Hearting: It belongs to the inside part of a wall among n the facing and backing.

Side: It refers to the surface that builds up the boundary of bricks or stones in a transverse direction to the face and bed.

Joint: It is the meeting point of two or more bricks or stones. If the joint is parallel to the bed of bricks or stones in a course then it is termed as bed joint. Alternatively, it is a horizontal layer of mortar on which masonry units are arranged.

The joints which are set perpendicular to the bed joints are called vertical joints or side joints or just joints.



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