Test: Building Materials- 2 - SSC JE MCQ

Compacted stone: It is a type of rock which has the quartz or the sand bound together with the cementing minerals like mica, feldspar etc.

Compacted stone has following properties:

(a) It is a sedimentary rock

(b) Its colour depends upon that of the feldspar.

(c) It can be used as a road metal if the higher quality stones like basalt and granite is not available.

(d) It is fire resistant.

(e) Its specific gravity is 2.25

(f) Its crushing strength varies 35 to 40 MN/m².

Among all these Compacted sandstones has more fire resisting properties.

Argillaceous rocks: Argillaceous rocks are those sedimentary rocks which are made up of their finest clay particles. These are those rock which contain clay or aluminium as the main constituent. These rocks are made of clay, a hydrated silicate of alumina. Such rocks are formed in the sea or lakes. However, flood deposits are more common. Examples are slate, laterite, Kaoline.

Sedimentary rocks: These are the type of rocks which are formed due to gradual deposition of materials like sand, clay etc., generally by setting water. Example are limestone and sandstone.

Siliceous rocks: These are the type of rocks which contain silica as main constituent. The granite, quartzite, gneiss is example of siliceous rocks.

Calcareous rocks: The calcareous rocks are those which contain lime or calcium carbonate as the main constituent. Example are limestone and marble.

Low heat cement: This cement is manufactured by reducing the proportion of C₃A and C₃S and increasing the proportion of C₂S. This cement shows low rate of development of strength. It contains 46% of dicalcium silicate.

Note: Whereas in Rapid hardening cement (which is formed by increasing the percentage of C₃S and decreasing the percentage of C₂S) contains only (9-10)% of C₂S. For OPC C₂S is generally 15%.

Gypsum is basically a Hydrated calcium sulphate (CaSo₄.2H₂O). It acts as a retarder in the cement and increase the setting time of cement. In places where setting time of cement required to be more, Gypsum is added in to that cement.

Important information about Gypsum: Gypsum is a mineral and is hydrated calcium sulphate in chemical form. Gypsum plays a very important role in controlling the rate of hardening of the cement. During the cement manufacturing process, upon the cooling of clinker, a small amount of gypsum is introduced during the final grinding process. Gypsum is added to control the “setting of cement”. If not added, the cement will set immediately after mixing of water leaving no time for concrete placing.

Nominal size of brick = 20 cm × 10 cm × 10 cm

Volume of 1 Brick = (0.20*0.10*0.10) m³

Number of Bricks required in 1500m³ of brickwork is =

II^nd Class Brick: It is Ground moulded, burnt in kilns. These class of bricks have surface hair cracks. Their edges may be sharp and uniform. These are commonly used at places where brickwork is to provided with a coat of plaster.

Note: While I^st class of brick is Table moulded and III^rd class of brick is Ground moulded but is used for unimportant works, temporary structures.

A lamin board is a board having a core of strips, each not exceeding 7 mm in thickness, glued together face to face to form a slab which in turn glued between two or more veneers, with the direction of the grain of the core strips running at right angles to that of the adjacent outer veneers. The lamin boards are light strong and do not split or crack easily. These are used for walls, ceilings, partitions. Their thickness varies from 12 to 25 mm.

Block board: Block board consists of smaller timber block up to 25 mm in width. These blocks are cemented edge to edge and on each face plies up to 3 mm thickness are glued. Block board is extensively used for construction of railway carriages, bus bodies, marine and river crafts and for furniture making, partitions, panelling, prefabricated houses, etc.

Batten board: The batten board is a board having a core made up of strips of wood usually 80 mm wide, each laid separately or glued or otherwise joined to form a slat which is glued between two or more outer veneers with the direction of the grain of the core running at right angles to that of the adjacent outer veneers. These are used for door panels, table tops etc.

Note: Fibre board are used for internal finish, wall panelling, floor, flush doors, table tops. These are used for fire and sound insulation in large commercial buildings and cinema houses. Hard board imparts internal appearance and finish to the structure.

In lime-cement Plaster, ratio 1 : 1 : 6 corresponds to cement : lime : sand.

The maximum permissible size of aggregate to be used in different construction work is as follows:

1. 40 mm for massive works like dams, retaining walls, etc.

2. 20 mm for Reinforced member.

3. 10 mm for floor.

1 m³ of wet cement mortar will correspond to 1.25 m³ of dry mortar

Sum of proportions = 1 + 5 = 6

Cement

1 m³ of cement = 1500 kg

So, 0.208 m³ of cement = 312.5 kg

Sand

Creosote is obtained from distillation of tar. For creosoting the timber is dried and then creosote oil is pumped under high pressure (1N/mm²) and high temperature. It is one of the best antiseptic against fungi and other agents.

Heart shakes and star shakes:

Radial ruptures in annual rings or splits radiating from the heart and extending towards the sapwood are called heart shakes. The shake occurring at near the pith and giving the appearance of a star at the end is called star shake. These shakes are caused by the quick drying of the central part of the tree.

Upsets: The defect caused by crushing or by injury in wood fibres.

Foxiness: This defect is due to the yellowish or reddish stains, caused by over maturity and lack of ventilation during storage.

As per IS 1077: 1992, clause 7.2, Bricks after immersion in cold water for 24 hours, water absorption shall not be more than 20 percent by weight upto class 12.5 and for the classes above 12.5 water absorption shall be between 12.5 and 15 percent.

Note: Water absorption for First class brick should not exceed 12-15 % of its dry weight. For second class brick it should be between 16-20%.

Le-Chatelier's Flask = For Specific Gravity

Le-Chatelier's Apparatus = Soundness due to  unburnt lime

Autoclave test= Soundness due to unburnt lime and magnesia

Characteristics of good building stone are:

• Compressive strength > 1000 kg/cm²
• High durability and coefficient of hardness > 14
• Specific gravity > 2.7
• Toughness index > 13
• Low water absorption

• Adulterants: Basin sulphate, calcium carbonate, Magnesium silicate etc
• Thinners: Petroleum, Spirit, naptha, turpentine oil
• Driers: letharge, Red lead, Cobalt, zinc
• Bases: White lead, Red lead, aluminium powder.

Los Angeles abrasion test is used to find abrasion resistance.

Los Angeles Machine: It consists of a hollow steel cylinder, closed at both the ends with an internal diameter of 700 mm and length 500 mm and capable of rotating about its horizontal axis.

Abrasive charge: Cast iron or steel balls, approximately 48mm in diameter and each weighing between 390 to 445g; six to twelve balls are required.

The surface on which distemper is to be done is first cleaned with sand paper and made smooth as far as possible. After the plaster gets dried up on the wall for minimum 60 days, only then distemper is to be done. First coat of lime is done on the plastered surface and after that 2 coats of distemper is applied.

These are water paints made with base as white chalk and thinner as water and are available as dry distemper and oil bound distemper.