Building Material (Part-III) (GENERAL ENGINEERING) (SSC JE)

Fire bricks are used for the following purposes–

• These are used for inner surface lining of kilns, turnacco, chimney etc.

• To build fire-resistance structures thereby reducing the damage of the structure against fire accidents.

• For inner lining of wood-fire ovens.

• As on insulating material for furnaces, ovens because of their lower thermal conductivity.

In paint zinc impart white colour.

Sap wood– The portion of the timber enclosed between the heart wood and cambium layer is known sap wood. Sap wood is light in colour than the heart wood.

Medullary rays – The thin radia fiberss extending from pith to cambium layer are known as the medullary rays. These rays help to hold the annual rings together.

Cambium layer – The function of cambium is to grow wood cells on the inside and smaller bast cell on the outside.

Bark – It protect the wood against mechanical damage. Its inner layer called bast conveys. The nutrients from the crown downwards and stores them.

Quick lime : Calcium oxide (CaO), commonly known as quick lime or burnt lime, is a widely used chemical compound. it is a white, caustic, alkaline, crystalline solid at room temperature.

Lean lime : It is used in rough masonry work.

Hydraulic lime –

• It has ability to set under water in thick damp condition with no air circulation.

• Used in foundation of underwater work.

Hydraulic lime–It is different in chemical composition from fat line in that it contains a definite amount of clay in addition to CaO, clay content in hydraulic lime may range from 10 to 30% by weight.

• This clay plus lime composition gives the hydraulic lime a property of hydraulicity.

Subdivision based on hydraulicity–

Class A – Eminently hydraulic – Clay content (21-30%)

Class B–Moderately hydraulic – Clay content (11-20%)

Class C – Feebly hydraulic – Clay content (5-10%)

Class D – Rich in magnesium, suitable only for finishing coats, do not process hydraulicity

Linseed oil most common material used as a vehicle of paint. It is extracted from flax seeds. It is used in various grades.

Carrier in paint:– Carrier or vehicles are the liquid substances which hold the ingredients of a paint in liquid suspension.

They are required mainly for two reasons:–

(a) To make it possible to spread the paint evenly & uniformly.

(b) To provide a binding for the ingredients of paints various vehicles used in paints are as following–

(i) Linseed oil
(ii) Tung oil
(iii) poppy oil
(iv) Nut oil

Argillaceous rocks–The predominant constituent is clay alumina which is actually clay, remains mixed up in varying proportion with siliceous, calcueous and carboneous matter. These are hard, brittle, durable and dense in nature.

Ex.–Laterite, slate,

The age of a tree can be estimated by the number of concentric rings on a cross-section of its trunk. A tree's age can be determined by counting the annual growth rings in its trunk. Each ring represents one year, and the ring's thickness reveals the relative amount of rainfall that year.

The component in cement which has the property of hydrating rapidly and is responsible to provide not only early strength but also the ultimate strength is tricalcium silicate.

Composition of cement clinker–

(i) I.S.- 1077 : 1992 – Clause 4.1 : The common brunt clay bricks shall be classified on the basis of average compressive strength.

(ii) I.S.- 456 : 1978 – IS code of practice for plain and reinforced concrete.

(iii) I.S.- 3495 : 1992 – Part 1 - Compressive strength test of bricks.

(iv) I.S.- 455 : 1989 – Portland slag cement specification.