Types of Bricks in Construction

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Questions and Answers

What is the primary purpose of First Class Bricks?

For pointing, exposed face work in masonry structures, flooring and reinforced brick work (correct)

For foundation and floors in lime concrete and road metal

For centering of reinforced brick and RCC structures

For building temporary structures

What is the maximum water absorption percentage allowed for Second Class Bricks?

16-20% of its dry weight (correct)

10-15% of its dry weight

20-25% of its dry weight

25-30% of its dry weight

What is the minimum crushing strength required for Second Class Bricks?

8.0 N/mm2

7.0 N/mm2 (correct)

5.0 N/mm2

6.0 N/mm2

What is the main characteristic of Third Class Bricks?

They are soft and light-coloured Signup and view all the answers

What is the recommended use of Fourth Class Bricks?

For foundation and floors in lime concrete and road metal Signup and view all the answers

According to ASTM C62, what grade of bricks is intended for use in areas subjected to frost action?

Severe Weathering (SW) Signup and view all the answers

What is the main factor that determines the durability of bricks?

All of the above Signup and view all the answers

Why are highly absorptive bricks problematic?

They can cause efflorescence and other problems in the masonry Signup and view all the answers

What is the purpose of grading bricks according to properties related to durability?

To determine their resistance to weathering Signup and view all the answers

What happens to brick if silica is present in excess?

It becomes brittle and weak Signup and view all the answers

What is the primary function of alumina in clay?

To absorb water and make clay plastic Signup and view all the answers

What happens if lime is present in excess in clay?

It causes the brick to melt and lose its shape Signup and view all the answers

What is the effect of magnesia on the brick?

It affects the colour and makes the brick yellow Signup and view all the answers

What is the primary function of iron oxide in clay?

To impart red colour on burning Signup and view all the answers

What is the result of burning bricks at a high temperature (more than 800°C)?

Red bricks are obtained Signup and view all the answers

What is the effect of excess ferric oxide on the brick?

It makes the brick dark blue Signup and view all the answers

What is the result of improvements in brick manufacturing?

More efficient brick plants with improved quality Signup and view all the answers

What is clay?

One of the most abundant natural mineral materials on earth Signup and view all the answers

What is the first phase of the manufacturing process?

Mining and storage of raw materials Signup and view all the answers

What is the purpose of storing sufficient quantities of raw materials?

To ensure continuous brick production regardless of weather conditions Signup and view all the answers

What is the purpose of blending the clays?

To produce more uniform raw materials and control color Signup and view all the answers

What is the purpose of size reduction machines?

To break up large clay lumps and stones Signup and view all the answers

What is the purpose of the pug mill?

To mix the raw materials with water Signup and view all the answers

What is the range of water mixed into the clay in the stiff-mud process?

10 to 15 percent Signup and view all the answers

How many principal processes are there for forming brick?

3 Signup and view all the answers

What is the purpose of tempering?

To produce a homogeneous, plastic clay mass Signup and view all the answers

What is the sixth and final phase of the manufacturing process?

De-hacking and storing finished products Signup and view all the answers

What is the maximum percentage of holes allowed in a solid brick?

25 per cent Signup and view all the answers

What is the minimum crushing strength required for a good brick?

10 N/mm2 Signup and view all the answers

What is the purpose of silica in brick making?

It enables the brick to retain its shape Signup and view all the answers

What is the maximum percentage of water absorption allowed for a good brick?

20 per cent of its dry weight Signup and view all the answers

What is the characteristic of a good brick in terms of its size and shape?

Uniform size and plane, rectangular surfaces Signup and view all the answers

What is the function of alumina in brick making?

It is not a main ingredient in brick making Signup and view all the answers

What is the characteristic of a good brick in terms of its texture and compactness?

The surfaces should not be too smooth Signup and view all the answers

What should be the sound produced when two good bricks are struck together?

A metallic sound Signup and view all the answers

What should be free from in the brick earth?

Stones, kankars, organic matter, saltpetre, etc. Signup and view all the answers

What happens when bricks come in contact with moisture?

Water is absorbed and the alkalis crystallise Signup and view all the answers

What is the recommended way to remove efflorescence from a brick?

Dry brush it away Signup and view all the answers

What is usually found in clay as a sulphate?

Calcium, magnesium, sodium, potassium or iron Signup and view all the answers

What happens when carbon is present in the clay and insufficient time is given during burning?

The sulphur causes the formation of a spongy, swollen structure in the brick Signup and view all the answers

What is the effect of a large proportion of free water in clay during drying?

The clay shrinks considerably Signup and view all the answers

What is the effect of combined water in clay during burning?

The clay shrinks Signup and view all the answers

What is the effect of using water containing small quantities of magnesium or calcium carbonates during burning?

The brick becomes decoloured Signup and view all the answers

Why is it important to remove efflorescence before rendering or plastering a wall?

To prevent the salts from reappearing later Signup and view all the answers

What is the result of insufficient oxidation of carbon and sulphur during burning?

The brick becomes decoloured by white blotches Signup and view all the answers

Study Notes

Classification of Bricks

First class bricks: recommended for pointing, exposed face work, flooring, and reinforced brick work
Second class bricks: permitted to have small cracks and distortions, higher water absorption (16-20%), and crushing strength of at least 7.0 N/mm2; recommended for hidden masonry works and centering of RCC structures
Third class bricks: under-burnt, soft, and light-coloured; used for building temporary structures
Fourth class bricks: over-burnt, distorted, and brittle; used for foundation, floors, and road metal in lime concrete

Strength and Durability

Clay building bricks are graded according to properties related to durability and resistance to weathering, including compressive strength, water absorption, and saturation coefficient (ASTM C62)
Three available grades: severe weathering (SW), moderate weathering (MW), and negligible weathering (NW)
Absorption is an important property that determines the durability of bricks
Highly absorptive bricks can cause efflorescence and other problems in the masonry

Characteristics of Good Bricks

Size and shape: uniform, plane, rectangular surfaces with parallel sides and sharp straight edges
Colour: uniform deep red or cherry colour, indicative of uniformity in chemical composition and thoroughness in burning
Texture and compactness: surfaces should not be too smooth, and brick should have a precompact and uniform texture
Hardness and soundness: hard, with a metallic sound when struck together
Water absorption: should not exceed 20% of its dry weight when kept immersed in water for 24 hours
Crushing strength: should not be less than 10 N/mm2
Brick earth: should be free from stones, kankars, organic matter, saltpetre, etc.

Ingredients of Good Bricks

Silica: enables brick to retain its shape, imparts durability, and prevents shrinkage and warping
Alumina: absorbs water, renders clay plastic, and prevents cracking on drying
Lime: normally constitutes less than 10% of clay, reduces shrinkage, causes silica to melt on burning, and lowers fusion point
Magnesia: affects colour, makes brick yellow or softens clay at a slower rate
Iron: imparts red colour, improves impermeability and durability, and lowers fusion point
Sulphur: usually found in clay as sulphate, can cause spongy structure and decolouration of brick if not properly oxidized during burning
Water: can cause shrinkage during drying and burning, and affect brick's strength and hardness

Manufacturing of Bricks

Fundamentals of brick manufacturing have not changed, but technological advancements have improved efficiency and product quality
Phases of manufacturing: mining and storage, preparing raw materials, forming, drying, firing and cooling, and de-hacking and storing finished products
Raw materials: clay, shale, and fire clay are mined and stored in separate areas to facilitate blending and control colour
Preparation: large clay lumps and stones are broken down and mixed to control particle size and produce a homogeneous, plastic clay mass
Forming: three principal processes - stiff-mud, soft-mud, and dry-press; stiff-mud process involves mixing water with clay to produce plasticity

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Description

This quiz covers the different types of bricks used in construction, including their characteristics, uses, and required specifications.