SSC JE Building Material Questions with Detailed Solutions

Defects in Bricks
i) Chuffs : Shape of bricks changes due to falling of rain water on hot bricks.
ii) Bloating : Spongy like structure due to presence of sulphur in brick earth.
iii) Blistering : Red stain blisters in drainage system.
iv) Efflorescence : White patches appears on the brick surface due to presence of alkali in the brick earth.

• Pig Iron : Pig iron is obtained after smelting of calcined ore in a blast furnace.
Carbon Content = 3.5% to 4.5%
• Wrought Iron : It is the purest form of iron.
Carbon Content = up to 0.08%
• Cast Iron : Carbon Content = 2% to 4%
• Mild Steel : It is an alloy of iron and carbon having carbon content of about 0.23%

Natural defects in timber :
i) Coarser Grain : If tree grows rapidly, the annual rings are widened. It is known as coarse grain timber and posses lesser strength.
ii) Knots : It is the most common defect in timber. It occurs when branches die off and the base become enclosed by a second layer of wood.
iii) Burls : They are formed when tree receives shock or injury in its young age.
=> Due to injury the growth of tree is completely upset and irregular projection appear on the body of tree.
iv) Twisting : The fiber of tree get twisted due to high wind velocity.
v) Shake : This defect occurs due to lack of nutrients.

Fly Ash:
It is a byproduct of the burning of coal in electric power generating plants.
It is called fly ash because it is transported from the combustion chamber by exhaust gases.
It is collected from the exhaust gases by electrostatic precipitators or bag filters.

Rapid Hardening Cement: -
Rapid Hardening Portland Cement (IS: 8041) has high lime content and can be obtained by increasing the C₃S content but is normally obtained from OPC clinker by finer grinding (450 m2/kg).
The basis of application of rapid hardening cement (RHC) is hardening properties and heat emission rather than setting rate. This permits addition of a little more gypsum during manufacture to control the rate of setting.
RHC attains same strength in one day which an ordinary cement may attain in 3 days. However, it is subjected to large shrinkage and water requirement for workability is more.

Igneous Rocks:
Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust.
The two main types of igneous rocks are extrusive and intrusive.
Example: - Granite, Basalt, Pumice and pegmatite etc.
Sedimentary Rocks:
Sedimentary rocks are formed by the deposition and subsequent cementation of the material at the Earth’s surface within the bodies of water.
Examples: - Limestone, Chalk, Clay, Sandstone, Shale etc.
Metamorphic Rocks: 
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism.
Examples: -  Gneiss, Quartzite, Slate, Schist, Quartzite and marble etc.

Extruded Particle Board : -
A board manufactured by mixing particles of wood and/or other lignocellulosic materials of predetermined sizes and shapes with synthetic resins and pressing while the mix is being forced through an extrusion hot platen press, pressure being applied in the direction of the length of extrusion which tends to orient the particles considerably in a direction at right angles to the direction of extrusion.

If the fineness of the cement is greater, surface area of the particles of the cement is also greater. And greater surface area leads to an increase in rapid hydration reaction.
Hydration reaction is increase so, the strength of development of cement will also increase.
So, increase in fineness of the cement will ultimately lead to increase in development of the strength of the cement.

Pith: 
It is the innermost part of tree consisting of cellular tissue which is used for nourishment of tree in young age.
Heartwood: 
The inner annual rings surrounding the pith are known as heartwood. It imparts rigidity to the tree.
Cambium Layer: 
It is a thin layer of sap between sapwood and the inner bark.
Inner bark: 
It gives protection to the cambium layer.
Outer bark: 
It is the outermost part of the tree.

Freezing of freshly laid concrete seriously impairs the structural integrity of concrete and results in strength loss due to the formation of ice lenses in capillary cavities. It happens in cold weather concreting.
Effect of cold water on concreting :
→ In cold weather hydration process of cement get slow due to this delay in setting time taken place.
→ To overcome the delay in setting accelerator may be used as admixture.
→ Hot water may be used to overcome from delay setting.
→ When temperature falls below the freezing point the formation of ice lenses occurs in capillary cavity due to this structural integrity of concrete takes place and ultimately loss of strength of concrete takes place.

According to Abraham law with increase in the water-cement ratio, compressive strength of concrete get decreases and vice-versa.
When water-cement ratio of cement increases then chances of segregation of concrete increases and also shrinkage of concrete increases due to more heat of hydration due to which compressive strength of concrete decreases.
Relation between compressive strength of concrete and water cement ratio

• Initial setting time of cement : It is the time elapsed after adding the water to the cement, when the cement paste start loosing its plasticity is known as initial setting time of cement.
• Final setting time of cement : It is the time elapsed after adding water to the cement, when cement paste has hardened sufficiently in such a way that 1 mm needle makes and impression on paste in the mould but 5 mm needle does not make any impression.

Quarrying of stones:
The process of taking out stones from natural rock beds is known as the quarrying of stones.
The operations carried out under the ground at a great depth are known as the mining of stones. 
The operations carried out at ground level are known as the quarrying of stones.
Dressing of stones:
The stones after being quarried are to be cut into suitable sizes with suitable surfaces.
This process is known as the dressing of stones.
Seasoning of stones:
The stones obtained fresh from the quarry contain some moisture which is known as quarry sap.
The process of removing moisture from freshly quarried stones with the help of any method or technique is known as stone seasoning.