Types and properties of bricks

Bricks is produced from well clay molding, that is dried and then burnt. The size of the brick varies from 90 mm × 90 mm × 90 mm and 190 mm × 90 mm × 40 mm. With mortar joints, the size of brick varies from 200 mm × 100 mm × 100 mm and 200 mm × 100 mm × 50 mm.

Types of Bricks: Bricks are categorized as -

(i) Building bricks, (ii) Paving bricks, (iii) Fire bricks, (iv) Special bricks.

Properties of Bricks: The standard quality bricks should contain the following properties -

(i) Colour: The color should have been identical and clear.

(ii) Shape: Shape of the bricks should have been sharp and genuine rectangular angles.

(iii) Size: There should be standard dimensions for bricks with adherence to codes.

(iv) Texture: A standard brick should contain a fine, solid and consistent texture. They should be free from fissures, cavities, loose grit and unburned lime.

(v) Virtue: If the brick is hit with another brick, there should be a metal sound.

(vi) Hardness: If scratches are made with finger on a brick, there should not be any mark on the brick.

(vii) Strength: The breaking strength of brick should not be under 3.5 N / mm2. A field test is conducted to check the strength by dropping the brick from a height of 0.9 m to 1.0 mm on a hard surface. If the brick has good strength, the stone should not be broken into pieces.

(viii) Water absorption: Once the brick is drowned in water for 24 hours, the water absorption rate should not exceed 20 percent by weight. For class I bricks, this limit remains 15 percent.

(ix) Efficiency: There should not be any white patches in bricks when they are drenched in water for 24 hours and then allowed to dry in the shade. White stains may appear because of the existence of sulfate of calcium, magnesium and potassium. They retain masonry in wet and humid conditions.

(x) Thermal conductivity: Bricks should contain low thermal conductivity, so the buildings developed with bricks should have cold temperature in summer and warm temperature in winter.

(xi) Sound insulation: Bigger bricks have poor sound insulators whereas light and hollow bricks have superior sound insulation.

(xii) (xii) Fire resistance: Normally, the fire resistance capacity of brick is good. Actually, bricks are utilized to trap steel columns to safeguard them from fire.

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Published By
Rajib Dey
www.constructioncost.co
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Some vital plastering defects and remedies to resolve them

Besides, cracking, there may be other flaws with plastering. John Roxburgh who performs lecturer at The Concrete Institute’s School of Concrete Technology, highlights the following points for plastering defects as well as proper solutions for resolving them.

1. Debonding: Plaster, particularly very thick layers, is set to debond from the wall if the exterior skin compresses at a diverse rate except for the plaster touching with the wall. It will be the outcome of insufficient substrate formation.

Areas greater than regarding the size of a plate should have been eliminated and substituted with the following :-

• Cleaning filthy or greasy wall surfaces completely.
• Maintain the exact moisture content for the walls.
• Prior to plastering, apply a cement slurry or spatterdash coat.
• Apply bonding liquids and abide by the method suggested by the manufacturer.

2. Hardness Scarcity: There do not exist any specifications for the hardness or strength of plaster, but soft plaster happens due to the followings:

• Inadequate cement.
• The sand contains unnecessary quantities of dust (in excess of 15% by mass going through the 0,075mm sieve).
• The utilization of a mix with sub-standard water-retention properties.
• The inclusion of supplementary water too long after first mixing (a practice called as re-tempering).

Sometimes, It becomes necessary to provide a slightly lower plaster that occasionally demonstrates vital cracking or debonding, as compared to strong one.

3. Instant drying: Normally, extreme early moisture loss occurs due to the following:

• Evaporation may occur if plastering is done in sun and wind.
• Suction into the walls, when the masonry units are not moistened.
• Apply bad grade sand that does not contain fine material (below 5% by mass passing the 0,075mm sieve).
• Refrain from applying building lime or a masonry cement when there is no fine material in sand.

4. Grinning: Grinning means when the mortar joints are evidently seen through the plaster. It occurs due to the variation in suction among the masonry units and the mortar, along with extraction of mortar joints.

To get rid of grinning, use an undercoat or a spatterdash coat prior to plastering.

5. Expansion: It contains swelling, softening, layer cracking and spalling of the plaster. It happens because of proprietary gypsum-based products in the mix. Under moist conditions, the sulphate from the gypsum reacts with the Portland cement paste and develops compounds of increased volume which mess up the plaster.

Just eliminate and substitute the plaster to get rid of expansion-induced disruption because of gypsum in the mix.

6. Popping: Pop-outs stand for conical fragments that appear on the plaster surface. These happen because of pollutant particles in the mix, which, when react with the moisture in the mix, extend and produce cavities in the plaster.

As soon as the reason for the pop-out is eliminated, the hole is filled with a proprietary filler and painted over.

Article Source: www.buildinganddecor.co.za

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Published By
Rajib Dey
www.constructioncost.co
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Some useful civil engineering notes

This construction video tutorial is very useful for civil engineering students as it contains 10 objective types of questions on civil engineering and their solutions.

Some of the sample questions & their answers are given below :-

As per pertinent IS code, the weight of the timber will be treated as perfect if there is 12% moisture content in it.

The strength of the timber will be optimal if applied load is parallel to grain.

A standard brick should not engross water by weight in excess of 20% (after immersed in water for 24 hours)

When ‘p’ denotes the standard consistency of cement, 0.85 percent water is utilized in performing the initial setting time test on cement.

The lime mortar is normally formed with hydraulic lime.

The compressive strength of a standard good 1:3 portland cement – sand mortar after the completion of 3 days of curing, should not be under 175 kg/cm2.

The split tensile strength of M15 grade concrete is 15 to 20% of its compressive strength.

For brief explanation, watch the following construction video tutorial.

Video Source: Technical Atyachar

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Published By
Rajib Dey
www.constructioncost.co
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Variations among plastering & pointing

This construction video tutorial teaches you how to separate plastering and pointing on various aspects.

1.  Plaster is applied to different types brick surfaces (made with first class bricks, second class bricks, third class bricks etc).
The pointing is done for only 1st class bricks as the edges and edges of 1st class bricks are perfect.

2.  In plastering, the materials on which it is applied are disguised.
But in pointing, the materials are visible as only the joints in bricks are filled up with mortar.

3.   After plastering, the surface becomes smooth and even.
But, after pointing, the surface becomes unsmooth as only joints are covered with pointing and there may be some gapes in joints and bricks.

4.  In plastering, large quantities of materials are required as plastering is done to all surfaces of the bricks.
As pointing is done to the joints of the bricks, so, materials like cement, sand and mortar are required in less quantities.

5.  Plaster is done to the both side of the wall (inside and outside).
Pointing is done to the one side of the wall particularly to the outside of the wall.

6.  Plaster safeguards the uncovered surface of the wall from rain, heat, moisture.
In pointing, the rain, heat, moisture are consumed within the wall.

7.  In plastering lime mortar, cement mortar or lime-cement mortar are used with cement and sand.
In pointing, cement mortar and sand is applied.

8.  Plastering forms a base for employing white/color washing.
In pointing, white washing or color washing is ruled out.

9.  In plastering, defects of masonry can’t be detected.
In pointing, the masonry work is completely visible.

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Published By
Rajib Dey
www.constructioncost.co

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