Maharashtra HSC Construction Technology (Vocational) cheat sheet

Standard brick (modular): 190 × 90 × 90 mm; conventional brick 230 × 110 × 70 mm; 10 mm mortar joint gives 200 × 100 × 100 mm module.

Brick classification by compressive strength (IS 1077): class 35 = 35 N/mm², class 25, class 20, class 17.5, class 15, class 12.5, class 10, class 7.5, class 5, class 3.5 N/mm² minimum average.

Initial setting time of ordinary Portland cement: not less than 30 minutes; final setting time: not more than 600 minutes (10 hours).

Cement soundness tested by Le Chatelier apparatus (unsoundness from free lime); fineness by Blaine air permeability (specific surface, m²/kg) or 90-micron sieve.

Mortar mix 1:4 or 1:6 (cement:sand) for brickwork; 1:3 for plaster on external faces; richer mix = higher strength and lower workability retention.

Concrete grades: M20 = 20 N/mm² characteristic cube strength at 28 days; nominal mixes 1:1.5:3 (M20), 1:2:4 (M15), 1:3:6 (M10).

Aggregate: coarse aggregate nominal size 20 mm for normal RCC, 40 mm for mass concrete; fine aggregate grading Zone I (coarse) to Zone IV (fine) per IS 383.

Timber: seasoning reduces moisture to 10-12% for carpentry; kiln seasoning faster than air seasoning; shrinkage is greatest along the tangential direction.

Curing: minimum 7 days for OPC concrete, 10 days for blended cement; strength gain continues with moisture and temperature above 5 °C.

Scale: representative fraction = drawing length / actual length; 1:50 means 1 mm on paper = 50 mm (50 mm real per mm drawn).

Standard scales: 1:100 for site plans, 1:50 for plans/elevations, 1:20 or 1:10 for details, 1:1000 for location plans.

Line conventions: continuous thick = visible outlines; dashed = hidden edges; chain/dash-dot = centre lines and section cutting planes; continuous thin = dimension and projection lines.

Dimensioning: dimension line with arrowheads at both ends, numerals above a continuous line, dimensions in millimetres for building work unless stated otherwise.

Long wall–short wall method: long walls measured centre-to-centre plus one wall thickness; short walls centre-to-centre minus one wall thickness.

Centre-line method: total centre-line length × breadth × height; junctions counted once, so it is quicker for symmetrical plans.

Trapezoidal rule for irregular trenches: Area = d/2 × [(first + last ordinate) + 2 × (sum of intermediate ordinates)].

Prismoidal rule: Volume = d/3 × [first + last + 4 × (sum of even ordinates) + 2 × (sum of odd ordinates)].

Approximate estimate: plinth area × plinth area rate; percentage-based approximate quantities use coefficients of the total cost (e.g., earthwork, concrete, brickwork shares).

Contingency and work-charged establishment are added as percentages; centage charges cover tools, plant, and supervision.

Chain surveying: principles of triangulation; base line measured most carefully; check lines verify the framework; offsets taken at right angles (perpendicular) or oblique.

Ranging: direct ranging when stations are intervisible; reciprocal ranging when ends are not visible from each other.

Obstacle to chaining but not ranging (river): measure perpendicular offsets and use similar triangles; obstacle to ranging: use reciprocal ranging or a random line.

Levelling: Height of Instrument (HI) = Reduced Level (RL) + backsight; RL of new point = HI − intermediate or foresight.

Rise and fall method: Rise = previous staff reading − current reading; arithmetic check: ΣBS − ΣFS = ΣRise − ΣFall = last RL − first RL.

Curvature and refraction correction for levelling: combined correction = 0.0673 D² (D in km, result in metres), applied as a negative correction to staff readings.

Theodolite: face left and face right readings cancel instrumental errors; horizontal angle = difference of vernier readings; sum of interior angles of a closed traverse = (2n − 4) × 90°.

Bearings: whole-circle bearing measured clockwise from north, 0° to 360°; fore bearing − back bearing = ±180°.

Contour interval is constant for a map; closer contours indicate steep ground; contours crossing a valley form a V pointing upstream.

Total station combines EDM distance measurement with electronic theodolite angle measurement and onboard coordinate computation.

Excavation: side slopes depend on soil type; shoring/strutting needed for deep trenches in loose soil; dewatering by sump pumping or wellpoint system.

Foundation types: isolated footing (column), combined footing (two columns), raft/mat (low bearing capacity or heavy loads), pile (weak strata at depth).

Minimum depth of foundation per Rankine: d = (q/γ) × [(1 − sin φ)/(1 + sin φ)]², where q = bearing capacity, γ = unit weight, φ = angle of repose.

Concrete placing: free fall limited to about 1.5 m; compaction by needle vibrator at 300-600 mm spacing; construction joints roughened and wetted before resuming.

Formwork striking times (OPC, ordinary conditions): vertical sides of beams/walls 24-48 h; soffit of slabs up to 3 days; beams up to 7 days; props retained longer for long spans.

Masonry: English bond alternates header and stretcher courses and is strongest; Flemish bond alternates header and stretcher in each course; quoin, queen closer, and frog positions matter for strength.

Bar bending: standard hooks 9d for a 180° hook, 8d for a 135° stirrup hook; lap length typically 40-50 times bar diameter; cover per IS 456 depends on exposure.

Site layout: locate stores, batching plant, and labour camps to minimise haul distance; bar chart (Gantt) shows sequence, CPM/PERT network shows critical path and float.

Critical path = longest path through the network; total float = latest start − earliest start; a zero-float activity lies on the critical path.

Stress = load / area (N/mm²); strain = change in length / original length (dimensionless); Young's modulus E = stress / strain within the elastic limit.

Simple bending: M/I = σ/y = E/R; section modulus Z = I/ymax; rectangular section Z = bd²/6; bending stress σ = M/Z.

Shear: average shear stress = V/A; for a rectangular section maximum shear stress = 1.5 × average; for a circular section 4/3 × average.

Deflection limits (IS 456): span/250 for total deflection, span/350 for deflection after partitions, span/125 for cantilever total deflection.

Concrete mix design (IS 10262): target mean strength = characteristic strength + 1.65 × standard deviation; water-cement ratio controls strength and durability.

Workability tests: slump (most common), compaction factor, Vee-Bee consistometer; slump cone dimensions 100 mm top, 200 mm bottom, 300 mm height.

Cube test: 150 mm cubes, cured 28 days, tested in compression; cylinder strength is about 0.8 of cube strength; flexural strength ≈ 0.7√fck.

Durability: minimum cement content and maximum w/c ratio depend on exposure class (mild, moderate, severe, very severe, extreme); cover increases with exposure severity.

Admixtures: plasticiser improves workability at same w/c; superplasticiser gives high slump; retarder slows setting for hot weather; accelerator speeds setting for cold weather repairs.

Water supply: minimum residual pressure at ferrule depends on building height; storage tank capacity commonly 100-150 litres per head per day for domestic use.

Pipe sizes: 15 mm for a single tap, 20 mm for a group of taps, 25-32 mm for a bathroom group; flow velocity kept below about 2 m/s to limit noise and erosion.

Sanitary fittings: water closet, wash basin, sink, floor trap, gully trap, inspection chamber; soil pipe carries sewage from WCs, waste pipe carries sullage from sinks and basins.

Drainage slopes: 1:40 to 1:60 for 100 mm soil pipe; 1:60 to 1:100 for 150 mm drains; self-cleansing velocity about 0.6-0.75 m/s.

Septic tank: retention 24 h, sludge storage, and soak pit or dispersion trench for effluent; not permitted where a public sewer is available.

Trap seal (water seal) depth 50-75 mm prevents sewer gas entry; vent pipe equalises pressure and protects seals.

Electrical: single-phase 230 V, three-phase 415 V, 50 Hz in India; earth wire is green or green-yellow; live is red/brown, neutral black/blue in typical wiring.

Circuit protection: MCB rating chosen above load current and below cable current-carrying capacity; ELCB/RCCB (30 mA) protects against earth leakage and shock.

Illumination: luminous flux in lumens, illuminance in lux (lumens per m²); recommended levels roughly 100 lux for corridors, 300 lux for offices, 500 lux for drawing work.

Personal protective equipment hierarchy: eliminate, substitute, engineer controls, administrative controls, then PPE as the last line of defence.

Head protection: helmets replaced after a significant impact or typically every 2-3 years; safety footwear with steel toe for site work.

Fall protection: guardrails and toe boards at edges; full-body harness anchored above shoulder level when working at height above about 1.8-2 m.

Scaffolding: base plates on firm ground, ties to the structure, working platform fully boarded, double guardrail; never use incomplete scaffolds.

Excavation safety: shoring for trenches deeper than about 1.5 m in loose soil; ladder access every 7.5 m of trench length; keep spoil at least 0.6-1 m from the edge.

Electrical safety on site: 110 V or residual current protection for hand tools; lockout-tagout before maintenance; no temporary wiring lying in wet ground.

First aid: CPR ratio 30 compressions to 2 breaths for adults; report every accident in the accident register; near misses recorded too.

Environment: dust suppression by water sprinkling, silt fences and settling tanks before discharge, noise limits near residential areas, segregation of construction and demolition waste.

Hazard identification: use a risk matrix of likelihood × severity; residual risk re-assessed after controls are applied.

Break-even quantity = fixed cost / (selling price per unit − variable cost per unit); contribution = price − variable cost.

Working capital cycle = inventory days + receivable days − payable days; construction contractors are typically paid against running bills and retention money.

Tender documents: notice inviting tender, tender form, bill of quantities, specifications, conditions of contract; earnest money deposit and security deposit are percentages of estimated cost.

Types of contract: lump sum, item rate, percentage rate, cost plus; item-rate contracts are standard for public works in Maharashtra.

GST registration threshold for services is ₹20 lakh turnover (₹10 lakh in special category states); keep invoices and returns current.

Business entities: sole proprietorship, partnership (Indian Partnership Act 1932), LLP (LLP Act 2008), private limited company (Companies Act 2013).

Communication: 7 Cs - clear, concise, concrete, correct, coherent, complete, courteous; active listening includes paraphrasing and clarifying questions.

Formal report structure: title, executive summary, introduction, methodology, findings, conclusion, recommendations, annexures.

Employability: a curriculum vitae lists qualifications, skills, and experience in reverse chronological order; a cover letter is tailored to the specific employer and role.

Masonry practical: soak bricks before laying, use a string line and plumb bob, check level with a spirit level; frog of the brick faces upward in the top course.

Plastering practical: 12 mm single-coat or 20 mm two-coat; mortar 1:4 to 1:6; cure for at least 7 days; check with a 3 m straight edge for evenness.

Bar bending practical: use a bar bending schedule; hook length 9d, bend deductions per IS 2502; stirrups at closer spacing near supports.

Carpentry practical: measure twice and cut once; use try square and marking gauge; joints - half lap, mortise and tenon, dovetail; keep tools sharpened and oiled.

Surveying field practice: measure a base line twice and take the mean; close a traverse and check angular error against permissible limits; record readings in a field book in ink.

Concrete practical: weigh batching preferred over volume batching; slump test immediately after mixing; cast cubes, label, cure in water tank at 27 ± 2 °C.

Plumbing practical: cut pipe square, deburr, apply solvent cement or thread seal tape; pressure test the line before concealing it in walls.

Electrical practical: verify supply is off with a tester before working; strip wire to correct length; tighten terminal screws; test continuity and insulation resistance with a megger.

Safety in workshop: keep gangways clear, store tools in a rack, use a fire extinguisher appropriate to the fire class, and report damaged hand tools immediately.