WBBSE Madhyamik Vocational Construction flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Water absorption of good brick

A good burnt clay brick absorbs no more than about 20% of its dry mass after 24 hours of soaking, indicating adequate burning and durability.

Initial setting time of cement

The time from adding water until cement paste begins to lose plasticity; for ordinary Portland cement it must be at least 30 minutes.

Nominal mix M20

A concrete mix of cement, fine aggregate and coarse aggregate in proportions 1:1.5:3 by volume, giving characteristic strength of 20 N/mm² at 28 days.

Bulking of sand

Increase in the volume of moist sand due to films of water around grains; it can be 20–30% and must be accounted for in volume batching.

English bond

A brick bond with alternate courses of headers and stretchers; it is strong and commonly used for load-bearing walls of one brick or more.

Damp proof course

A layer of impervious material, often 40–50 mm cement concrete with waterproofing compound, placed at plinth level to stop rising dampness in walls.

Standard stair riser and tread

For comfortable use, risers are typically 150–190 mm and treads 250–300 mm, with a stair width of at least 900 mm and headroom of 2100 mm.

Pile foundation

A deep foundation made of long slender members driven or cast into the ground to transfer loads to a strong bearing stratum below weak soil.

Spirit level use

A tool with a bubble in a curved vial; the bubble centred between marks shows the surface is horizontal, and it is used to check level and plumb.

Safe working load

The maximum load a sling, chain, hoist or scaffold is designed to carry safely, marked on the equipment and never exceeded during lifting.

Needle vibrator

An internal concrete vibrator inserted vertically into fresh concrete and withdrawn slowly, compacting it and removing air voids without causing segregation.

Ladder 1 in 4 rule

A leaning ladder should be set so that the base is one unit out for every four units of height, giving an angle of about 75 degrees.

Representative fraction

The ratio of drawing distance to ground distance expressed as a fraction, such as 1:1000, meaning one unit on paper equals 1000 units on ground.

Check line

A survey line measured between two fixed points on the framework to verify that the chain lines have been laid out correctly and without error.

Height of instrument

The reduced level of the line of sight of a level, calculated as the reduced level of a known point plus the backsight reading on it.

Rise and fall method

A leveling booking method where the difference between successive staff readings gives a rise or fall, and reduced levels are obtained by adding rises and subtracting falls.

3-4-5 rule

A setting-out method using a triangle with sides in the ratio 3:4:5, which is a right-angled triangle, to establish a perpendicular corner on site.

Diagonal check for squareness

For a rectangular layout, both diagonals must be equal; the diagonal length equals the square root of the sum of the squares of the two sides.

Long wall short wall method

A quantity take-off method where long walls are measured out-to-out and short walls in-to-in, using centre-line lengths adjusted by half wall thickness.

Centre line method

An estimating method where the total centre-line length of walls is multiplied by breadth and depth; junctions need careful adjustment to avoid double counting.

Section drawing

A drawing showing a vertical cut through a building, revealing internal heights, foundations, floors and roof, with materials indicated by hatching patterns.

Hidden line in drawing

A dashed line used on a construction drawing to show an edge or feature that is not visible in the view but exists behind the visible surface.

Finished floor level

Abbreviated FFL, it is the reduced level of the top finished surface of a floor, used as a reference for setting door and window heights.

Bar bending schedule

A table listing bar mark, diameter, shape, cutting length and number of reinforcement bars, used for fabrication and for calculating the total steel weight.

Personal protective equipment

Safety items such as helmet, goggles, gloves, safety shoes and dust mask worn by workers to protect against site hazards; it is the last line of defence.

Trench shoring

Temporary supports of timber or steel placed against the sides of an excavation deeper than about 1.5 m to prevent soil collapse and protect workers.

Silicosis hazard

A lung disease caused by inhaling fine silica dust from cutting, grinding or drilling concrete and stone; controlled by water suppression and dust masks.

Plinth area estimate

A quick approximate estimate found by multiplying the plinth area of the building by a standard plinth area rate per square metre for similar construction.

Dry volume factor for mortar

Mortar or concrete wet volume is multiplied by about 1.30–1.35 for mortar and 1.52–1.54 for concrete to get dry volume, allowing for voids in sand.

Steel bar weight formula

The weight of a reinforcement bar in kilograms equals diameter squared divided by 162, multiplied by its length in metres, with diameter in millimetres.

Rate analysis

The process of working out the cost per unit of an item from material, labour, plant, overhead and profit components, forming the basis of the estimate.

Curing of concrete

Keeping freshly placed concrete moist for 7–14 days so that cement hydration continues, developing strength and reducing shrinkage cracks.

Measurement book

A record book in which site measurements of completed work are entered accurately and jointly, forming the basis for billing and payment.