Test: Building Materials- 3 - SSC JE MCQ

IS: 1141-1958- Classification of timber for seasoning purposes

IS: 399-1963- Classification of commercial timbers and their zonal distribution

IS: 1708-1969-Methods of testing of small specimen of timber

IS: 4970-1973-Key for Identification of commercial timbers

Requirements of Good Brick-earth are:

1) It must have proper proportions of sand, silt and clay.

2) It must be homogeneous

3) It should have sufficient plasticity (so that the bricks can be properly and conveniently moulded with sharp and well defined edges)

4) It must be free from lumps of lime or nodules of kankar.

5) It must be free from earth containing alkaline salts, kankar etc.

6) It must be free from pebbles, grits and lumps of earth.

7) It must not contain vegetable and organic matter.

8) It should not be mixed with salty water.

9) It should be well brunt.

Taking the average of size of aggregates between 40 to 50 mm.

Average size of aggregate m

An aggregate is said to be elongated if its greatest dimension is greater than 1.8 times the mean diameter.

Slot length to test elongation of aggregate = 1.8 x 45 = 81 mm.

Density of cement bag = 1440 kg/m³

Volume of 1 bag of cement of mass 50 kg is:

Slenderness ratio of the wall is defined as the ratio of its effective length or effective height (minimum of these two) to the effective thickness.

As per IS 456:2000, section 32.2.3,

The ratio of effective height to thickness. H_we/t (slenderness ratio) of masonry wall shall not exceed 30.

As per IS 3495:1976,

The rating of efflorescence for up to class 12.5 bricks should not be more than moderate

For the bricks of class higher than 12.5 it should not be more than slight

Lignin is regarded as lying outside of the microfibril forming a protective sheath.

As lignin is located only on the exterior it must be responsible for cementing together the fibrils and in imparting shear resistance in the transference of stress throughout the composite.

Most resin or "gum" varnishes consist of a natural, plant- or insect-derived substance dissolved in a solvent, called spirit varnish. The solvent may be alcohol, turpentine, or petroleum-based. Some resins are soluble in both alcohol and turpentine. Generally, petroleum solvents, i.e. mineral spirits or paint thinner, can substitute for turpentine.

The resins include amber, dammar, copal, rosin, sandarac, elemi, benzoin, mastic, balsam, shellac, and a multitude of lacquers

Note: There is no wax in Spirit varnish

Rind galls: Rind galls are curved swellings of trees which are formed at a point where a branch of the tress is improperly removed or fell down.

Heart rots: Heart rot is caused in the trees when the heart wood is attacked by fungi through its newly formed branch. This type of fungi makes the tree hollow by consuming heart wood. This defect is known as heart rot.

Knots: When the base of branches forms a mark on the stem which results dark coloured stains on the surface after conversion. This dark coloured at the central part or stem are known as Knots.

With reference to the various test results on aggregate:

For aggregate to be used in pavement construction:

Aggregate impact value, Aggregate Abrasion value, Aggregate crushing value, should not be greater than 30.

For aggregate to be used in any other type of construction except pavement:

Aggregate impact value, Aggregate crushing value should not be greater than 45 and Aggregate Abrasion value should not be greater than 50.

Defect arises due to conversion of timber:

Chip mark, Torn grain, Diagonal grain and wane.

Defect arises due to Fungi:

Heart rot, Brown rot, White rot, Dry rot, Wet rot, Sap stain and Blue stain.

Defects arises due to Natural forces:

Cup shakes, Ring shakes, Heart shakes, Star shake and radial shake.

Defects arises due to Seasoning:

Bow, warp, cup and Twist.

Plywood: It is made by gluing together plywood layers, also called veneers. These veneers are glued together with adjacent plies having their wood grain at right angles to each other. This allows them to form a composite material.

Phenomenon: Cross-graining, i.e. having the wood grain at right angles to each other, reduces the tendency of wood to split, as well as reduces expansion and shrinkage. It also makes the strength of the panel consistent across both directions.

Water absorbing cement is not a type of Portland cement.

A Portland cement interground with a water-repellent material such a stearate (e.g., sodium or aluminium); reduces capillary water transmission under little or no pressure but does not completely stop water-vapour transmission.

Rapid Hardening Portland Cement (RHPC) is Portland cement that is modified (usually by further grinding) to hydrate more rapidly in the first few hours after casting.

Stacking is not the step involved in the preparation of brick.

Manufacturing of bricks consists of the following 4 operations or steps:

i) Preparation of brick clay or brick-earth

ii) Moulding of bricks

iii) Air drying of bricks

iv) Burning of bricks

Rapid hardening of cement can be obtained by fine grinding of clinker, thus increases the surface area of the cement particles, which in turn increases the rate of hydration of cement that leads to decrease in setting time of cement.

While Gypsum and calcium sulphate are retarders which increases the setting time of cement.

Quarrying is the process of removing the rock, sand, gravel or other minerals from the ground in order to use them to produce materials for construction or other uses.

Dressing: It is the process of giving a proper size, shape and finish to the roughly broken stones as obtained from the quarry

Temperature for brick burning varies from 1000° to 1200°C,

Temperature for cement burning varies from 1300° to 1500°C.