Odisha CHSE +2 Vocational Building Maintenance flashcards

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

Modular brick size

Standard modular brick per IS 1077 measures 190 × 90 × 90 mm; with a 10 mm mortar joint the nominal size becomes 200 × 100 × 100 mm, giving 500 bricks per cubic metre of masonry.

Bulking of sand

Increase in loose volume of sand due to moisture films around particles, typically 20–30% at 4–6% moisture content; must be accounted for when measuring sand by volume for mortar.

Slump test

Workability test using a cone 100 mm top, 200 mm bottom, 300 mm high; concrete is filled in three layers, rodded 25 times each, and the settlement measured in millimetres.

Initial setting time of cement

Minimum 30 minutes for ordinary Portland cement when tested by Vicat apparatus; mortar must be placed and compacted before this time to avoid loss of strength.

English bond

Brick bond with alternate courses of headers and stretchers; strongest bond for walls one brick or thicker, with queen closers next to quoin headers to break vertical joints.

Queen closer

A brick cut lengthwise into two halves; placed next to the quoin header in English and Flemish bond to adjust bond and prevent continuous vertical joints at corners.

Cavity wall

Two leaves of masonry 90–100 mm thick separated by a 50–75 mm air gap; galvanised steel wall ties at 900 mm horizontal and 450 mm vertical spacing tie the leaves together.

Through stone

A stone extending the full thickness of a rubble masonry wall, placed at 1.5 m intervals both longitudinally and transversely to tie the wall faces and distribute load.

Plaster thickness for brick walls

12 mm for internal brick walls, 15–20 mm for external walls, and 6 mm for ceilings; two-coat work uses a 10 mm undercoat plus a 6 mm finish coat.

Plaster of Paris setting time

Plaster of Paris sets in 5–15 minutes after mixing with water; used for decorative cornices and mouldings but unsuitable for damp locations because it softens with moisture.

Punning or three-coat plaster

High-quality plaster finish made of a 12 mm backing coat, 6 mm floating coat, and 3 mm finishing coat of lime or gypsum; used for smooth internal surfaces in quality work.

Trap seal depth

Depth of water in a trap that prevents sewer gas entry; minimum 50 mm for water closets and floor traps, and 75 mm for gully traps in drainage systems.

One-pipe drainage system

System in which soil and waste pipes discharge into a single vertical stack, with a separate vent pipe to equalise pressure and prevent trap seal loss.

Self-cleansing velocity

Minimum flow velocity of 0.75 m per second in horizontal drains that keeps solid matter moving and prevents silt deposition; achieved by gradients of 1 in 40 to 1 in 80.

Inspection chamber spacing

Inspection chambers are provided at intervals not exceeding 30 m on straight drain runs, and at every change of direction, junction, or change of gradient.

RCCB tripping current

Residual current circuit breaker for human protection trips at 30 mA earth leakage; for fire protection the setting is 100 mA; the test button should be pressed monthly.

Earthing resistance limit

Earth electrode resistance should not exceed 1 ohm for a single electrode in ordinary soil; measured with an earth tester and kept low by charcoal and salt backfill.

Lighting circuit load limit

A single lighting circuit should carry not more than 800 watts or 10 points; power circuits are kept separate, and the main switch and meter are sized from total connected load.

Mortise and tenon joint

Joint in which a projecting tenon on one member fits into a mortise cut in the other; used in door frames and furniture because it resists tension and bending well.

Standard residential door size

Per IS 10021, a residential door is commonly 900 × 2000 mm or 800 × 2000 mm, with a leaf thickness of 35–40 mm; bathroom doors are typically 700 × 2000 mm.

Holdfast

A mild steel flat about 300 mm long, fixed to the door or window frame and embedded in masonry at top and bottom on each side to anchor the frame.

Emulsion paint coverage

One litre of emulsion paint covers about 8–10 square metres per coat; enamel covers 10–12 square metres; primer covers 10–12 square metres; recoat after 4–6 hours.

French polish

Shellac dissolved in methylated spirit, applied with a rubber pad in circular motion; gives a high-gloss transparent finish on internal wooden furniture.

Paint blistering

Formation of raised bubbles under a paint film caused by moisture trapped beneath the surface; cured by removing the film, drying the substrate, and repainting.

Epoxy injection for cracks

Repair method for fine cracks in concrete: ports drilled at 200–300 mm spacing, surface sealed, low-viscosity epoxy injected at low pressure, then cured for 24 hours.

Concrete spalling repair

Chip back to sound concrete, clean reinforcement, apply rust converter and bonding agent, then fill with polymer-modified mortar and cure to restore section and protection.

Column jacketing

Retrofitting technique in which a column is enlarged with 75–100 mm of new concrete and reinforcement, tied to the original section by shear keys and dowels.

Steel bar weight formula

Weight of a steel bar in kilograms per metre equals the square of its diameter in millimetres divided by 162; a 12 mm bar therefore weighs 0.888 kg per metre.

Dry volume factor for concrete

Wet concrete volume is multiplied by 1.54 to obtain dry volume of ingredients; cement bags equal dry volume times cement ratio divided by sum of ratios and by 0.035.

Centre line method

Estimation method suitable for walls of equal thickness: total centre line length multiplied by width and depth, with deductions at junctions to avoid double counting.

Personal protective equipment on site

Helmet, safety shoes, gloves, goggles, ear plugs, dust mask, and full-body harness for work above 1.8 m; all must be inspected before use and replaced when damaged.

Leaning ladder slope rule

A leaning ladder should be set at a 4:1 slope, extend at least 1 m above the landing, be secured at top and bottom, and never be worked from the top three rungs.