Punjab PSEB Matric NSQF Construction flashcards
Punjab PSEB Matric NSQF Construction · Build recall with a focused review session.
31 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Modular brick nominal size
- A modular brick measures 190 × 90 × 90 mm, and with a 10 mm mortar joint its nominal size becomes 200 × 100 × 100 mm, simplifying masonry dimension calculations.
- Initial setting time of cement
- The time from adding water until the cement paste begins to lose plasticity. For ordinary Portland cement it must not be less than 30 minutes.
- Final setting time of cement
- The time after which the cement paste has completely hardened and a needle cannot penetrate it. It must not exceed 600 minutes for ordinary Portland cement.
- M20 concrete nominal mix
- M20 is a nominal mix of 1 part cement, 1.5 parts sand, and 3 parts coarse aggregate by volume, giving characteristic compressive strength of 20 N/mm² at 28 days.
- Slump test purpose
- The slump test measures the workability or consistency of fresh concrete. Typical values are 25–75 mm for normal RCC and 75–125 mm for heavily reinforced sections.
- Safe bearing capacity
- The maximum pressure a soil can carry without shear failure or excessive settlement, obtained by dividing ultimate bearing capacity by a factor of safety of 2.5 to 3.
- Dumpy level versus auto level
- A dumpy level has a fixed telescope and relies on a bubble tube for levelling. An auto level uses an internal compensator that automatically keeps the line of sight horizontal.
- Plaster thickness standards
- Internal brick walls are plastered about 12 mm thick, while external walls and rough surfaces take 15–20 mm, usually with 1:4 to 1:6 cement mortar.
- Cement:sand mortar ratios
- Common volume ratios are 1:3 for load-bearing masonry and strong plaster, 1:4 for general brickwork, and 1:6 for internal plaster and non-structural work.
- Concrete curing duration
- Concrete should be kept moist for at least 7 days with ordinary Portland cement, extended to 10 days in hot, dry weather, using ponding or wet covering.
- Brickwork quantity per cubic metre
- One cubic metre of brick masonry requires roughly 500 bricks plus about 0.30 cubic metres of mortar, assuming standard brick size and 10 mm joints.
- 3-4-5 right angle method
- Measure 3 m along one line and 4 m along the other; adjust the angle until the diagonal is exactly 5 m, confirming a true 90-degree corner.
- Height of instrument formula
- Height of instrument equals the known reduced level of a point plus the backsight reading taken on that point. Subsequent RLs are HI minus foresight readings.
- Reduced level calculation
- The reduced level of any point equals the height of instrument minus the staff reading at that point, the basic calculation in levelling field books.
- Plumb bob use
- A plumb bob hung from a string establishes a true vertical line; masons use it to check the plumb of walls and columns during construction.
- Spirit level function
- A spirit level contains a bubble in a curved tube; when the bubble centres between marks, the surface or member is horizontal or vertical within the tool's accuracy.
- Mason's square use
- A mason's square is a right-angled tool used to check corners and squareness of masonry, formwork, and plastered surfaces at 90 degrees.
- Mortar dry volume factor
- Wet mortar volume is converted to dry volume by multiplying by about 1.33, because sand bulking and voids increase the dry material requirement.
- Sand bulking allowance
- Moist sand increases in volume by up to about 30 percent; quantity estimates for mortar must allow for this bulking to avoid short supply on site.
- Scaffold platform width
- Working platforms on scaffolds must be at least 600 mm wide, with guardrails at about 900 mm and 1800 mm heights for fall protection.
- Personal protective equipment on site
- Mandatory site PPE includes a safety helmet, safety shoes, and a high-visibility vest; eye protection and gloves are added for cutting and mixing tasks.
- Plastering sequence
- Clean and wet the surface, apply a backing coat of 1:3 to 1:4 cement mortar, roughen it, then apply the finishing coat and cure for at least 7 days.
- Concrete compaction purpose
- Compaction with a vibrator or rod removes entrapped air from fresh concrete, increasing density, strength, and durability and preventing honeycombing.
- Bull nose and quoin
- A quoin is the corner brick or stone of a wall, laid alternately to bond the masonry; a bull nose is a rounded brick used at exposed corners.
- English bond brickwork
- English bond alternates one course of headers with one course of stretchers, giving strong, stable walls; it is used for thick load-bearing walls.
- Flemish bond brickwork
- Flemish bond places alternate headers and stretchers in every course. It gives an attractive face appearance but is weaker than English bond.
- Aggregate size for concrete
- Coarse aggregate for normal RCC is usually 20 mm nominal size; it should not exceed one-quarter of the minimum member dimension or the bar spacing.
- Water-cement ratio
- The water-cement ratio is the mass of water divided by the mass of cement. Lower ratios increase strength; typical structural values are 0.4 to 0.5.
- Mortar joint thickness
- Brick masonry mortar joints are normally 10 mm thick; uniform joints distribute load evenly and control the overall height of the wall.
- Levelling staff reading
- A levelling staff is a graduated rod read through the level telescope; the backsight is taken on a known point and foresights on points to be determined.
- Curing methods on site
- Accepted curing methods include ponding with water, covering with wet gunny bags or sand, and continuous sprinkling, all keeping the concrete surface moist.