BUILDING MATERIALS : Brick and brick masonry & stones Notes

By Deepanshu Rastogi|Updated : March 30th, 2021



Composition of Good Brick Earth

Following are the constituents of brick earth:

1. Alumina

It is the chief constituent of every kind of clay. A good brick earth should contain about 20 to 30 per cent of alumina. This constituent imparts plasticity to earth so that it can be moulded.

2. Silica

  • A good brick earth should contain about 50 to 60 per cent of silica. Presence of this constituent prevents cracking, shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks.
  • Excess of silica destroys the cohesion between particles and bricks become brittle.

3. Lime

  • It should be present in a finely powdered state and not in lump.
  • Lime prevents shrinkage of raw bricks. Sand alone is infusible. But it slightly fuses at kiln temperature in presence of lime.
  • Excess of lime causes the brick to melt and hence, its shape is lost. Lumps of lime are converted into quick lime after burning and this quicklime slakes and expands in presence of moisture.

4. Oxide of Iron

  • About 5 to 5 per cent is desirable in good brick earth. It helps lime to fuse sand. It also imparts red color to bricks.
  • Excess of oxide of iron makes the bricks dark blue or blackish

5. Magnesia

A small quantity of magnesia in brick earth imparts yellow tint color to bricks and decreases shrinkage. But excess of magnesia leads to the decay of bricks.

Harmful Ingredients in Brick Earth

1. Lime

  • It causes unsoundness in brick if present in excess amounts.

2. Iron pyrites

  • If iron pyrites are present in brick earth, bricks are crystallized and disintegrated during burning.

3. Alkalies

These are mainly in the form of soda and potash

4. Pebbles

The presence of pebbles or grits of any kind is undesirable in brick earth because it will not allow the clay to be mixed uniformly and thoroughly which will result in weak and porous bricks.

5. Organic Matter

Presence of organic matter in brick earth assists in burning. But if such matter is not completely burnt, bricks become porous.

Manufacture of bricks

1. Preparation of clay

Clay of bricks is prepared in the following order:

  1. Unsoiling
  2. Digging
  3. Cleaning
  4. Weathering
  5. Blending
  6. Tempering

2. Moulding

Hand Moulding

  • Machine Moulding


  • Plastic Clay Machine
  • Dry Clay Machine

3. Drying

4. Burning: Burning of bricks is done either in clamps or in kilns.

(a) Clamps: Its shape in plan is generally trapezoidal. Floor of clamp is prepared in such a way that short end is slightly in the excavation and wider end is raised at an angle of about 15° from ground level.

(b) Kilns: A kiln is a large over which is used to burn bricks. The kilns which are used in the manufacture of bricks are of the following two types.

(i) Intermittent kilns (ii) Continuous kilns

(i) Intermittent Kiln: This may be over ground or underground they are classified in two ways: (a) intermittent up-drought kilns, (b) Intermittent down-drought kilns

Comparison between bull's trench kiln and Hoffman's kiln


Comparison between clamp Burning and kiln Burning


Tests For Bricks

1. Absorption

  • A brick is taken and it is weighted dry. It is then immersed in water for a period of 16 hours.
  • Then weight again and the difference in weight should not, in any case, exceed
    (a) 20 per cent of weight of dry brick for first class bricks.
    (b) 22.5 per cent for second class bricks.
    (c) 25 per cent for third class bricks.

2. Crushing strength

  • Minimum crushing strength for first class bricks image004 and for second class bricks image005

3. Hardness

In this test, a scratch is made on brick surface with the help of a finger nail. If no impression is left on the surface, brick is treated to be sufficiently hard.

4. Presence of soluble salts

  • Soluble salts, if present in bricks, will cause efflorescence on the surface of bricks.
  • It is immersed in water for 24 hours. It is then taken out and allowed to dry in shade. Absence of grey or white deposits on its surface indicates absence of soluble salts.
  • If the white deposits cover about 10% surface, the efflorescence is said to be slight.
  • When white deposits cover about 50% of surface thin it is said to be moderate.
  • If grey or white deposits are found on more than 50% of surface, the efflorescence becomes heavy and it is treated as serious.

5. Shape and Size

  • Its shape should be truly rectangular with sharp edges.
  • 20 bricks are randomly selected of standard (19 × 9 × 9 cm) for good quality bricks, the results should be within the following permissible limits:
    Length – 368 cm to 392 cm
    Width – 174 cm to 186 cm
    Height – 174 to 186 cm

6. Soundness

  • In this test, two bricks are taken and they are struck with each other.
  • Bricks should not break and a clear ringing sound should be produced.

7. Structure

  • It should be homogenous compact and free from any defects such as holes, lumps, etc.
  • High duty fire-clays can resist temperature range of 1482°C to 1648°C; medium duty fire-clays can resist temperature range of 1315°C to 1482°C and low duty fire-clays can resist temperature up to 870°C only.

Quality of Good Bricks

  • The bricks should be table-moulded, well burnt in kilns, copper-coloured free from cracks and with sharp and square edges.
  • The bricks should be uniform in shape and should be of standard size.
  • The bricks should give a clear metallic ringing sound when struck with each other.
  • The bricks when broken or fractured should show a bright homogeneous and uniform compact structure free from voids.
  • The brick should be sufficiently hard. No impression should be left on brick surface, when it is scratched with finger hail.
  • The bricks should not break into pieces when dropped flat on hard ground from a height of about one meter.
  • The bricks, when soaked in water for 24 hour should not show deposits of white salts when allowed to dry in shade.
  • No brick should have the crushing strength below 5.50 N/MM2.

Classification of Bricks

The bricks can broadly be divided into two categories:

1. Unburnt Bricks: The unburnt or sun dried bricks are dried with the help of heat received from the sun after the process of moulding. These bricks can only be used in the construction of temporary and cheap structures. Such bricks should not be used at places exposed to heavy rains.

2. Burnt Bricks: These are classified in four categories:

  1. First Class Bricks
    • These bricks are table-moulded and of standard shape and they are burnt in kilns.
    • The surfaces and edges of the bricks are sharp square smooth and straight.
    • First class bricks have all qualities of good bricks.
    • These bricks are used for superior work of permanent nature.
  2. Second Class Bricks
    • These bricks are ground moulded and they are burnt in kilns.
    • The surface of these bricks is somewhat rough and shape is also slightly irregular.
    • These bricks are commonly used at places where bricks work is to be provided with a coat of plaster.
  3. Third Class Bricks
    • These are ground moulded and they are burnt in clamps.
    • These bricks are not hard and they have rough surface with irregular and distorted edges.
    • These bricks gives dull sound when struck together.
    • They are used for unimportant and temporary structures.

Size and Weight Of Bricks(For India)

  • Standard size of bricks is 19 cm × 9 cm × 9 cm
  • Normal size (with mortar) is 20 cm × 10 × 10 cm.
  • The commonly adopted nominal size of traditional bricks is 23 cm × 11.4 cm × 7.6 cm.
  • It is found that the weight of 1 m3 of bricks earth is about 1800 kg. Hence the average weight of a brick will be about 3 to 3.50 kg.

Shape of Bricks

1. Bulinose Brick

  • A brick moulded with a rounded angle is termed as a bulinose. It is used for a rounded quoin.
  • A connection which is formed when a wall takes a turn is known as quoin.


2. Channel Bricks

  • These bricks are moulded to the shape of a gutter or a channel and they are very often glazed.
  • These bricks are used to function as drain.

3. Coping bricks

  • These bricks are made to suit the thickness of walls on which coping is to be provided.
  • Such bricks take various forms such as chamfered half-round or saddle-back.


4. Cownose Bricks

  • A brick moulded with a double bulinose on end is known as cownose.

5. Curved Sector Bricks

  • These bricks are in the form of curved sector and they are used in the construction of circular brick masonry pillars, brick chimneys.
  • The perforation may be circular, square, rectangular or any other regular shape in cross-section.
  • The water absorption after immersion for 24 hour in water should not exceed 15% by water.
  • Compressive strength of perforated bricks should not be less than 7 N/mm2 on gross area.

6. Hollow Bricks

  • These are also known as cellular or cavity bricks. Such bricks have wall thickness of about 20 mm to 25 mm. They are prepared from special homogeneous clay. They are light in weight about one third the weight of the ordinary bricks of the same size. The use of such bricks leads to speedy construction. They also reduce the transmission of heat, sound and damp. They are used in the construction of brick partitioning.


7. Paving bricks

  • These bricks are prepared from clay containing a higher percentage of iron. Excess iron vitrifies the bricks at a low temperature. Such bricks resist better the abrasive action of traffic. Paving bricks may be plain or checkered.


8. Perforated Bricks

  • Perforated bricks are used in the construction of brick panels for lightweight structures and multi-storeyed framed structures.







Stone has been defined as the natural, hard substance formed from minerals and earth material which are present in rocks, Rock may be defined as the portion of the earth's crust having no definite shape and structure. All rocks have definite chemical composition and made up of minerals and organic matter.


The rocks which are classified in the following three ways:

(i) Geological classification

(ii) Physical classification

(iii) Chemical classification.

(i) Geological classification: Geologically, the rocks are classified in the following three types:

(a) Igneous Rocks: The rocks which are formed by the cooling of magma are known as the igneous rocks. Igneous rocks are further classified in the following three classes:

Plutonic Rocks: Such rocks are formed due to cooling of magma at a considerable depth from earth's surface. The cooling is slow and the rocks possess coarsely grained crystalline structure. Example: Granite.

Hypabyssal Rocks: These rocks are formed due to cooling of magma at a relatively shallow depth from the earth's surface. The cooling is quick and hence these rocks possess finely grained crystalline structure. The dolerite is an example of this type of rock.

Volcanic Rocks: These rocks are formed due to pouring of magma at earth's surface. Due to rapid cooling these rocks are extremely fine grained in structure. The basalt is an example of this type of rock.

(b) Sedimentary rocks: These rocks are formed by the deposition of products of weathering on the pre-existing rocks. The examples of sedimentary rocks are gravel, sandstone. limestone Gypsum, lignite, etc.

(c) Metamorphic rocks: These rocks are formed by the change in character of the pre-existing rocks due to great heat and pressure. Gneiss, Phyllite, Schist, Slate are examples of metamorphic rocks.

(ii) Physical Classification: According to this classification, the rocks are of the following three types:

(a) Stratified rocks: These rocks possess planes of stratification or cleavage and such rocks can easily be split up along these planes. The sedimentary rocks are distinctly stratified rocks.

(b) Unstratified rocks: These rocks are unstratified. The structure may be crystalline granular or compact granular. The igneous rocks of volcanic agency and sedimentary rocks affected by movements of the earth are of this type of rocks.

(c) Foliated rocks: These rocks have a tendency to be split up in a definite direction only. The foliated structure is very common in case of metamorphic rocks.

(iii) Chemical classification: According to this classification, the rocks are of the following the types:

(a) Siliceous rocks: In these rocks, the silica predominates. The rocks are hard

and durable. They are not easily affected by the weathering agencies. The granites, quartzites, etc. are examples of siliceous rocks.

(b) Argillaceous rocks: In these rocks, the argil or clay predominates. These stones are hard and durable but brittle. The slates, laterites, etc. are examples of the siliceous rocks.

(c) Calcareous rocks: In these rocks, the calcium carbonate predominates. The limestones, marbles, etc. are examples of calcareous rocks.


The stones are obtained from the rocks are very important building material because of its durability and hardness. The stones are widely used in foundation, walls, columns, lintels, arches, roofs, floors etc.

Tests for Stones

Following are the test performed on stones to evaluate different properties:

(i) Acid test: In this test, a sample of stone weighing about 0.50 to 1 N taken. It is placed in a solution of hydrochloric acid having strength of one percent and it is kept there for seven days. The solution is agitated at intervals. Good building stone maintains its sharp edges and keeps its surface free from powder at the end of this period. If edges are broken and powder is formed the surface, it indicates the presence of calcium carbonate.

(ii) Attrition test: This test is done to find out the rate of wear of stones which are used in road construction. The sample of stone is broken into pieces of about 60 mm size. Such pieces, weighing 50 N are put in both the cylinders of Deval's attrition test machine. The diameter and length of cylinder are respectively 200 mm and 340 mm. The cylinders are closed. Their axes make an angle of 30° with the horizontal. The cylinders are rotated about horizontal axis for 5 hours at the rate of 30 R.P.M. After this period, the contents are taken out from the cylinders and they are passed through a sieve of 1.50 mm mesh. The quantity of material which is retained on the sieve is weighed. The Percentage wear is expressed loss in weight in percentage of initial weight of the sample.

(iii) Crushing test: This test is performed to find out compressive strength of stones. The stone is cut into cubes of site 40 mm X 40 mm ×40 mm. The minimum number of specimens to be tested are three. Such specimens should be placed in water for about 72 hours or to test and there after tested in saturated condition.

The load is applied axially on the cube in a crushing test machine. The rate of loading is 13.72 N/mm2 per minute. The crushing strength of the stone is the maximum load at which its sample fails divided by the area of the bearing face of the specimen.

(iv) Crystallisation test: In this test, at least four cubes of stone with side 40 mm are taken. They are dried for 72 hours and weighed. They are then immersed in 14 per cent solution of Na2SO4 for 2 hours. They are dried at 100°C and weighed. The difference in weight is noted. This procedure of drying. weighing, immersing and reweighing is repeated at least five times. Each time, the change in weight is noted and it is expressed as a percentage of original weight.

(v) Freezing and thawing test: The specimen of stone is kept immersed in water for 24 hours. It is then placed in a freezing mixture at -12°C for 24 hours. tis then thawed or warmed at atmospheric temperature. This should be done in shade to prevent any effect due to wind, sun rays, rain, etc. Such a procedure is repeated several times and behaviour of stone is carefully observed.

(vi) Hardness test: This test is carried out to determine the hardness of a stone. A cylinder of diameter 25 mm and height 25 mm is taken out from the sample of stone. It is weighed and placed in Dorry's testing machine and pressed with a pressure of 12.50 N. The annular steel disc of machine is then rotated at a speed of 28 RPM. After 1000 revolutions, the specimen is taken out and weighed. The coefficient of hardness is found out from the following equation:

(vii) Impact test: The impact test is carried out to determine toughness of a stone. A cylinder of diameter 25 mm and height 25 mm is taken out from the sample of stone. It is placed on cast-iron anvil of machine. A steel hammer of weight 20 N is allowed to fall axially in a vertical direction over the specimen. The blow at which specimen breaks is noted. If it is nth blow, n represent the toughness index of stone.

(viii) Smith test: This test is performed to find out the presence of soluble matter in a sample of stone. The few chips or pieces of stones are taken and placed in a glass tube. This tube is then filled with clear water. After about an hour, the tube is vigorously stirred or shaken. The presence of earthy matter will convert the clear water into dirty water. If water remains clear, the stone be durable and free from any soluble matter.

(ix) Water absorption test: For this test, a stone weighing about 0.50 N is prepared. The cube is then immersed in distilled water for a period of 24 hours and weighed again after a period of 24 hours. The percentage absorption by the sample of stone after 24 hours is given by following formula:


W1 = Initial weight of sample

W2 = Weight of the sample after immersion in water

Qualities of Good Building Stones

Following are the qualities of a good building stone:

(i) Crushing strength: For a good structural stone, the crushing strength should be greater than 100 N/mm2.

(ii) Appearance: The stones which are to be used for face work should be decent in appearance and they should be capable of preserving their colour uniformly for a long time. A good building stone should be of uniform colour and free from clay holes, spots of other colour etc.

(iii) Durability: A good building stone should be durable. The various factors contributing to durability of a stone are its chemical composition, texture, resistance to atmospheric and other influences, location in structure, etc.

(iv) Hardness: The coefficient of hardness should be greater than 17 for a stone to be used in road work. If it is between 14 and 17, the stone is said to be of medium hardness. If it is less than 14 is said to be of poor hardness and such stone should not be used in road work.

(v) Percentage wear: In attrition test, if wear is more than 3 per cent, the stone is not satisfactory. If it is equal to 3 per cent. the stone is just tolerable. For a good building stone, the wear should be equal to or less than 3 percent.

(vi) Seasoning: The stones should be well seasoned before putting into use. A period of about 6 to 12 months is considered to be sufficient for proper seasoning. (vii) Specific gravity: For a good building stone, its specific gravity should be greater than 2.7.

(viii) Toughness index: In impact test, if the value of toughness index comes below 13, the stone is not tough. If it comes between 13 and 19, the stone is said to be moderately tough. If it exceeds 19, the toughness of stone is said to be high. (ix) Water absorption: For a good quality stone, percentage absorption by weight after 24 hours should not exceed 0.60.

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