UNIT 2: CONSTRUCTION MATERIALS - EXAM-FOCUSED SHORT NOTES

Based on RGPV past papers (2022-2025). Prioritized by frequency.

I. STONES (ROCKS)

A. Classification of Stones

1. Geological Origin:

2. Based on Physical Properties/Usage:

• Building Stones: For walls, columns, paving (e.g., Granite, Sandstone).

• Ornamental Stones: For decorative purposes (e.g., Marble, polished Limestone).

• Engineering Stones: For specific engineering works (e.g., Kota Stone for flooring, Slate for electrical insulation).

B. Quarrying and Dressing of Stones

• Quarrying Steps: Site selection → Drilling → Blasting → Loading → Transporting.

• Dressing Methods:

  • Hammer Dressing: Rough surface for better bonding.

  • Chisel Dressing: For fine surfaces and shapes.

  • Machine Dressing: For uniform size and finish (ganged saws, planers).

  • Polishing: For marble/granite using abrasives.

• Why Dressing is Necessary:

  To achieve desired shape & size, remove weathered layer, ensure proper bonding in masonry, improve aesthetics, and reduce weight.

C. Properties, Defects & Deterioration of Stones

• Properties of Good Building Stone:

  • Strength: High crushing/compressive strength (>100 N/mm² for structural).

  • Durability: Resistance to weathering (temperature, rain, chemicals).

  • Hardness & Toughness: Resist abrasion and impact.

  • Porosity & Absorption: Low porosity (<5%) and water absorption for frost resistance.

  • Workability: Easy to quarry, cut, and dress.

  • Appearance: Uniform colour, fine texture.

• Common Defects:

  • Seams/Veins: Weak planes, reduce strength.

  • Cavities/Flaws: Holes, cracks, cause failure points.

  • Nodules/Concretions: Hard inclusions, hinder dressing.

• Causes of Deterioration:

  • Atmospheric Action: Rain, wind, temperature cycles cause disintegration.

  • Chemical Attack: Acid rain (dissolves limestone), salt crystallization.

  • Vegetation: Root growth causes cracks.

  • Frost Action: Water in pores freezes and expands.

D. Specific Stones & Applications

• Marble:

  • Properties: Metamorphic limestone, crystalline, takes high polish, hard, durable, low porosity, susceptible to acid.

  • Varieties: White (Makrana), coloured (green, black, pink).

  • Uses: Flooring, wall cladding, statues, tabletops.

• Kota Stone:

  • Properties: Fine-grained sandstone from Rajasthan, non-absorbent, hard, durable, naturally slip-resistant.

  • Manufacturing: Quarried in slabs, cut, dressed, polished.

  • Applications: Flooring (industrial/commercial), pathways, sills, dado.

• Granite:

  • Properties: Igneous, very hard, dense, durable, high compressive strength, low absorption, polishable.

  • Uses: Bridge/piers, monumental works, kitchen countertops, flooring in high-traffic areas.

II. BRICKS

A. Manufacturing Process

1. Selection & Preparation of Soil: Clayey soil (Alumina 20-30%, Silica 50-60%, Iron oxide 5-10%). Weathering (3-4 weeks) removes impurities.

2. Molding:

   • Hand Molding: Ground mould, table mould. ** Frog** (indentation) for keying.

   • Machine Molding: Table moulding (pug mill + extruder) or extrusion (wire-cut bricks).

3. Drying: Shade drying (7-10 days) to remove moisture to ~5-7%. Prevents cracking in kiln.

4. Burning (Firing):

   • Clamp (Intermittent): Temporary, uneven burning, low quality.

   • Kilns (Continuous):

     • Bull's Trench Kiln (BTK): Common in India, fuel efficient.

     • Tunnel Kiln: Most efficient, uniform quality, automated.

5. Characteristics of Well-Burnt Bricks:

   • Colour: Golden/reddish-brown (not black/porous).

   • Sound: Metallic ring on striking.

   • Structure: Homogeneous, compact, no efflorescence.

   • Absorption: <20% by weight.

B. Properties of Good Bricks

C. Classification of Bricks

D. Clay-Fly Ash Bricks & Other Variants

• Clay-Fly Ash Bricks:

  • Composition: Clay (30-40%) + Fly Ash (60-70%) + Water.

  • Manufacturing: Similar to clay bricks, often steam cured.

  • Properties: Lightweight, high strength, good insulation, utilizes industrial waste.

  • Advantages: Eco-friendly, uniform, less cracking, good plaster bond.

• Sand-Lime Bricks: Sand + Lime (10%) + Water, autoclaved. Smooth, uniform, used for exposed work.

• Concrete Bricks: Cement + Sand + Aggregate. High strength, can be coloured, used for fences, paving.

III. TIMBER AND WOOD PRODUCTS

A. Structure and Properties of Timber

• Macrostructure:

  • Pith: Central core, soft, weak.

  • Annual Rings: Growth rings (spring/summer wood).

  • Heartwood: Inner, dark, durable (extractives).

  • Sapwood: Outer, light, moist, susceptible to fungi.

  • Medullary Rays: Radial strips for storage.

  • Bark: Protective outer layer.

• Engineering Properties:

  • Strength: Highest parallel to grain, low perpendicular.

  • Elasticity & Toughness: Good for shock absorption.

  • Hardness: Varies with density.

  • Durability: Heartwood > Sapwood. Requires seasoning & preservative.

  • Workability: Easy to saw, nail, plane (if seasoned).

  • Thermal/Acoustic: Good insulator.

B. Defects in Timber

C. Timber Seasoning

• Why Important:

  Reduce MC to 8-12% (equilibrium). Prevents shrinkage/warping/cracking, increases strength/durability/workability, reduces weight & fungal/insect attack.

• Methods:

  • Natural:

    • Air Drying: Stacked with stickers, 6-12 months. Low cost, slow.

    • Water Seasoning: Logs in water (prevents checks). Removes sap, but may degrade cellulose.

  • Artificial:

    • Kiln Drying: Controlled T&RH, 1-3 weeks. Fast, uniform, but costly.

    • Electrical Seasoning: High-frequency current heats internally.

    • Chemical Seasoning: Use of hygroscopic salts (e.g., CaCl₂).

D. Wood Substitutes and Wood Products

• Need: Timber scarcity, cost, consistency, specific properties (size, strength, finish).

• Products:

  • Plywood: Thin veneers (3+ plies) bonded at 90°. Properties: High strength, dimensionally stable, no warping. Uses: Furniture, partitions, concrete shuttering.

  • Blockboard/Battenboard/Laminboard: Core of strips (block/batten) or battens with outer veneers. Blockboard: Stiff, for shelves/doors.

  • Fibreboards:

    • Hardboard: Dense, smooth, hard. (Doors, panels).

    • MDF (Medium Density Fibreboard): Uniform, smooth, good for machining. (Furniture, cabinets).

  • Particle Boards (Chipboard): Wood chips + resin. Cheap, but moisture-sensitive. (Furniture, underlay).

  • Veneers: Thin slices (<6mm) for decorative overlays.

  • Hardwoods vs. Softwoods (Commercial): Hardwoods (deciduous, dense, durable: Teak, Sal). Softwoods (coniferous, light, straight: Pine, Deodar).

IV. GLASS

A. Nature, Structure & Manufacturing

• Nature: Amorphous solid (non-crystalline). Supercooled liquid.

• Composition: Silica (SiO₂ 70-75%), Soda ash (Na₂CO₃), Limestone (CaCO₃), Cullet (broken glass).

• Manufacturing - Float Glass Process (Pilkington):

  1. Molten glass (1000°C) poured onto bath of molten tin.

  2. Floats & spreads uniformly (thickness controlled by draw rate).

  3. Cooled in annealing lehr (controlled cooling to relieve stresses).

  Produces flat, defect-free, fire-finished surfaces.

• Molecular Structure: Disordered network of SiO₄ tetrahedra (no long-range order).

B. Properties of Glass

C. Coatings on Glass & Performance Modification

V. PIPES AND PIPE FITTINGS

A. Comparative Study of Pipe Materials

B. Specific Pipe Types

• PVC Pipes:

  • uPVC (unplasticized): Rigid, for pressure (water supply) & non-pressure (drainage).

  • PVC (plasticized): Flexible, for drainage, conduits.

  • Advantages: Light, cheap, corrosion-proof, smooth bore (low friction).

  • Disadvantages: Low temperature/UV resistance, combustible.

• Asbestos Cement (AC) Pipes:

  • Composition: Cement + Asbestos fibres (chrysolite).

  • Properties: Rigid, corrosion-resistant, brittle, asbestos fibres cause lung disease (asbestosis, mesothelioma). Largely banned.

• Stoneware Pipes:

  • Composition: Vitrified clay (high temp firing).

  • Properties: Hard, dense, impervious, excellent chemical resistance, brittle.

  • Uses: Underground sewerage, drainage, industrial waste.

• Chlorinated Polyvinyl Chloride (CPVC):

  • Properties: Chlorination improves heat resistance (up to 90°C), pressure rating, flame retardancy vs. PVC.

  • Applications: Hot water plumbing, industrial liquid transfer.

VI. PAINTS, VARNISHES, POLISHES & COATINGS

A. Ideal Paint Characteristics

Good hiding power, easy application, uniform flow, durability (weather/corrosion), strong adhesion, colour retention, reasonable cost, non-toxic, quick drying.

B. Paint Composition & Types

• Composition of Oil Paints:

  1. Base/Pigment: Provides colour & opacity (White lead, Zinc oxide, TiO₂).

  2. Vehicle/Oil: Binder, dries to film (Linseed, Tung, Soybean oil).

  3. Solvent/Thinner: Adjusts viscosity (Turpentine, Naphtha).

  4. Additives: Driers (Co, Pb naphthenates), fillers (talc), anti-settling agents.

• Comparative Study:

C. Painting Process & Special Finishes

• Steps for Painting Wooden Surfaces:

  1. Surface Preparation: Clean, sand, remove old paint/grease.

  2. Knotting: Apply knotting compound (shellac/aluminium) over knots to prevent resin bleed.

  3. Priming/Undercoating: Seal pores, ensure adhesion.

  4. Filling (if needed): Grain filler for open-grain woods (oak).

  5. Sanding: Between coats (fine abrasive).

  6. Finishing Coats: 2-3 coats of paint/enamel.

  Considerations: Wood MC <12%, proper drying time, temperature/humidity.

• French Polish:

  • Composition: Shellac dissolved in spirit (ethanol).

  • Process: Applied with pad (muller) in circular motions, built in thin layers, finally rubbed with fine abrasive & oil.

  • Characteristics: High gloss, spirit-mendable, not durable (heat/water sensitive). Traditional for fine furniture.

• Wax Polish:

  • Composition: Beeswax/ Carnauba wax + solvent (turpentine) + oil.

  • Process: Applied thinly, buffed to soft sheen.

  • Characteristics: Protective, low sheen, easy maintenance. For furniture/flooring.

VII. ROOFING AND FLOORING MATERIALS

A. Roofing Materials

B. Flooring Materials

VIII. SPECIALIZED MATERIALS

A. Thermal Insulating Materials

• Why Important: Reduce heat transfer → energy conservation, thermal comfort, prevent condensation.

• Types:

  • Fibrous: Glass wool, Rock wool (mineral). Light, porous, low λ (~0.03-0.04 W/mK).

  • Cellular: EPS (expanded polystyrene), XPS (extruded, denser, less water absorb), Polyurethane foam, Cork.

  • Reflective: Aluminium foil laminates (reflect radiant heat, require air gap).

B. Sound Proofing (Acoustic) Materials

• Principle:

  • Absorption: Porous materials (glass wool) convert sound energy to heat.

  • Barrier/Isolation: Massive, dense materials (concrete, lead) block transmission; resilient mounts decouple.

• Types: Fibrous insulation (glass/rock wool), Acoustic panels, Plasterboard, Resilient channels, Heavy barriers (concrete, lead sheets).

C. Waterproofing Materials

• Purpose: Prevent water ingress (basements, tanks, roofs).

• Types:

  • Liquid Membranes: Bituminous coatings, polymer-modified cementitious, polyurethane, epoxy (applied as liquid, form film).

  • Sheet Membranes: Bitumen felt, PVC/HDPE sheets, EPDM rubber (laid as sheets).

  • Integral Waterproofing: Water-repellent admixtures mixed in concrete.

  • Traditional: Mud plaster (clay), Lime concrete (with surkhi).

D. Bituminous Materials (Tar & Bitumen)

• Properties: Viscous, adhesive, waterproof, durable, thermoplastic (softens on heat, hardens on cooling).

• Advantages: Waterproof, cheap, durable, good adhesion.

• Disadvantages: Temperature sensitive (soft in summer, brittle in winter), flammable, ages (oxidizes).

• Applications: Road construction (tarmacadam, asphalt), waterproofing (roofs, basements), roofing felts, pipe coating.

IX. METALS AND CONCRETE

A. Aluminium

• Key Properties:

  • Lightweight (ρ ~2.7 g/cm³, 1/3 steel).

  • Corrosion-resistant (forms protective Al₂O₃ film).

  • Good conductor (heat & electricity).

  • Ductile, malleable, reflective.

  • Low strength (but high strength-to-weight ratio in alloys).

• Uses in Construction:

  • Window/door frames, curtain walls, roofing, cladding.

  • Structural members (alloys like 6061, 6063).

  • Ladders, handrails, solar panel frames.

B. Concrete

• Ingredients:

  • Cement, Fine Aggregate (sand), Coarse Aggregate (gravel/crush), Water, Admixtures.

• Chemical Composition of Cement (Bogue's Compounds):

  • C₃S (Tricalcium Silicate): Early strength.

  • C₂S (Dicalcium Silicate): Long-term strength.

  • C₃A (Tricalcium Aluminate): Early setting, generates heat, sulfate resistance low.

  • C₄AF (Tetracalcium Aluminoferrite): Colour, minor strength.

• Grades of Concrete (M5 to M80):

  M stands for Mix. M20 means characteristic compressive strength f_ck = 20 N/mm² (MPa) at 28 days.

• Types of Concrete (Any Three Special Concretes):

  1. High-Strength Concrete (HSC): f_ck > 60 MPa. Low w/c ratio, silica fume, superplasticizers. Use: High-rise columns, bridges.

  2. Self-Compacting Concrete (SCC): Flows under its own weight, no vibration. High workability, no segregation. Use: Congested reinforcement, complex shapes.

  3. Lightweight Concrete: Density < 2000 kg/m³. Lightweight aggregates (expanded clay, sintered fly ash). Use: Precast panels, thermal insulation, reduces dead load.

  4. High-Density Concrete: Density > 3000 kg/m³ (Barytes, magnetite aggregate). Use: Radiation shielding (nuclear plants, hospitals).

  5. Ready-Mix Concrete (RMC): Batched & mixed centrally, delivered in transit mixers. Use: Large projects, quality control.

X. MISCELLANEOUS MATERIALS

A. Gypsum Boards (Plasterboards)

• Core: Gypsum (CaSO₄·½H₂O) plaster sandwiched between paper liners.

• Types & Uses:

  • Regular: General internal partitions, ceilings.

  • Fire-Resistant: With glass fibres/vermiculite. Use: Fire-rated walls/ceilings.

  • Moisture-Resistant: With water-repellent additives. Use: Bathrooms, kitchens.

  • Insulating: With perlite/vermiculite core. Use: Thermal/acoustic insulation.

  • Sound-Resistant: Dense core, special jointing. Use: Recording studios, conference rooms.

B. Ultra Poly Vinyl (UPVC)

• Properties: Unplasticized PVC → rigid, strong, UV-stabilized (with additives), low maintenance, excellent weatherability, chemical resistant.

• Uses: Window/door profiles (main application), pipes (uPVC), cladding, siding.

> [!TIP] EXAM STRATEGY

• High-Frequency Focus: Stones, Bricks, Timber, Glass, Paints appear in almost every paper. Master classification, properties, defects, and manufacturing.

• Comparative Questions: Be ready to compare (e.g., paints, pipes, roofing). Use tables in your answers.

• Definitions are Key: "Why is seasoning important?", "Define efflorescence.", "What is Low-E coating?".

• Specific Short Notes: Marble, Kota Stone, Stoneware Pipes, French Polish, Distempers are repeated 5m/4m questions. Have 5-6 bullet points ready.

• Diagrams: For Float Glass Process, Quarrying/Dressing tools, Timber structure, Paint composition – simple labelled sketches can fetch extra marks.

• Units & Standards: Remember compressive strength units (kg/cm² or MPa), absorption %, thermal conductivity (W/mK).