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

Preservation of timber is carried out to increase the life of timber Dichloro-diphenyl trichloro ethane (DDT), Creosote oil, organic solvent, ASCU treatment and various types of chemical treatment of timber which is used to protect timber from fungi and insects.
Various treatment process

Boucherie process–By this process, sapwood of almost all green timbers with the bark on and of bamboos in green condition soon after felling can be treated using any of the inorganic water soluble preservatives

Empty cell process–It is aimed at a maximum penetration of the preservative with a minimum net retention.

Classification of brick–
1. First class bricks–Its surface should be smooth and rectangular with parallel sharp and straight edges and square corner.
• Its water absorption should be upto 20%
• Its crushing strength = 105 kg/cm² or 10.5 N/mm²

2. Second class bricks–It is in irregular shape and size and its have rough, uneven faces may consist hairline cracks.
• Its water absorption should not greater than 22%
• Its crushing strength = 70 kg/cm² or 7 N/mm²

3. Third class bricks–It is in non-uniform shape and size with irregular and distorted edges.
• Water absorption should not greater than 25%
• Crushing strength = 35 kg/cm²

Composition of paint–
(i) Base–It is principal constituent of paint. It makes the paint film opaque and possesses binding propeties which reduce shrinkage cracks. Ex.–white lead, road lead, zinc white, oxide of iron.
(ii) Solvent or thinner–It make the paint of workable consistency and evaporate during drying of the film. Ex.–Spirit, Naptha, Turpentine oil.
(iii) Vehicle–It works as a binder. It holds the constituent of paint in suspension and helps spread it over the surface to be pointed. Ex.–Linseed oil, nut oil, poppy oil, tung oil.
(iv) Pigments–It used to import the desired color.
(v) Adultrants–It helps to reduce the weight and increase durability of paint.

ASCU treatment–ASCU treatment is used for preservation of timber to enhance the strength of timber. ASCU stands for Arsenic Pentaoxide Copper Sulphate.

Creosote oil–It is also used for preservation of timber.

Sir Abel's process–It is used to treatment of timber making for fine resistance.

Efflorescence–These types of defect occurs in bricks due to excess of alkalies like as sodium or potassium salts in brick earth. These defects occur when bricks come in contact with moisture, water is absorbed and the alkalies crystalize.

Chuffs–Deformation of the shape of bricks caused by the rain water falling on hot bricks is known as chuffs.

Bloating–These types defeat observed as spongy swollen mass over the surface of burned bricks is caused due to presence of excess carbonaceous matter and sulphur in brick clay.

Soundness of cement– Soundness of portland cement refers to the ability of a hardened cement paste to retain its volume after setting without delayed expansion. Normal cement hydration reactions occurring due to setting and hardening tends to produce small charges in the volume of the hydrating paste if this change in volume of cement paste is in excess, then such cement is termed as unsound of expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO).

The test for fineness is conducted by sieve analysis or by finding the specific surface area. Sieve analysis 100 grams of cement is sieved through IS sieve no. 9 for 15 minutes and the residue is weighed this should not exceed 10 percent.

When water is added to cement, the chemical reaction called hydration takes place and contributes to the final concrete product and heat is generated. The calcium silicates contributes most of the early strength.