Construction Materials (CE-302) - Unit 5 Short Notes

UNIT 5: CONSTRUCTION MATERIALS

I. STONES (ROCKS)

Classification of Stones

• Based on Geological Origin:

  • Igneous Rocks: Formed from cooling magma/lava.

    • Examples: Granite (intrusive), Basalt (extrusive).

    • Uses: Granite for monumental, heavy engineering; Basalt for road metal, concrete aggregate.

  • Sedimentary Rocks: Formed by deposition/cementation of sediments.

    • Examples: Limestone, Sandstone, Shale.

    • Uses: Limestone for cement, lime; Sandstone for masonry, paving.

  • Metamorphic Rocks: Formed by transformation of existing rocks under heat/pressure.

    • Examples: Marble (from limestone), Slate (from shale), Quartzite (from sandstone).

    • Uses: Marble for flooring/decoration; Slate for roofing, flooring; Quartzite for aggregate, flooring.

• Based on Physical Properties/Usage (Common Construction Stones):

  • Granite: Hard, durable, crystalline. Used for bridges, monuments, flooring.

  • Basalt: Fine-grained, dense, tough. Used for road construction, concrete aggregate.

  • Limestone: Sedimentary, calcareous. Used for lime, cement, masonry.

  • Sandstone: Sedimentary, sandy texture. Used for masonry, paving, ornamental work.

  • Slate: Metamorphic, foliated, cleaves easily. Used for roofing, flooring, damp-proof courses.

  • Marble: Metamorphic, crystalline, takes polish. Used for flooring, wall cladding, sculpture.

  • Quartzite: Metamorphic, very hard, resistant. Used for flooring, aggregate, silica brick.

  • Laterite: Porous, iron-rich. Used for rough masonry, road metal after stabilization.

Quarrying and Dressing of Stones

• Quarrying Steps: Site selection → Removal of overburden → Drilling → Blasting/Wedging/Heating → Extraction → Transport.

• Dressing: Process of giving stone a required shape, size, and surface finish.

  • Tools: Chisels, mallets, hammers, axes, saws, planers.

  • Process: Sizing → Shaping → Finishing (coursed, rubble, ashlar).

• Necessity of Dressing:

  • To achieve desired shape and size for proper bonding.

  • To obtain smooth, even surface for aesthetics and reduced mortar.

  • To remove weathered, soft outer layer (weathered skin).

  • To make stones suitable for specific architectural finishes.

[!TIP] Exam Focus: Be prepared to list quarrying methods (blasting, wedging, heating) and dressing types (hammer-dressed, chisel-dressed, machine-dressed). Dressing necessity is a common 2-3 mark question.

Defects, Deterioration, and Preservation of Stones

• Common Defects:

  • Structural: Faults, veins, texture variations.

  • Weathering: Disintegration, exfoliation, cracking due to climate.

• Causes of Deterioration:

  • Atmospheric: Rain, frost, temperature changes.

  • Chemical: Acid rain, atmospheric gases (SO₂, CO₂).

  • Physical: Salt crystallization, wind erosion.

• Preservation Methods:

  • Surface Treatments: Application of water-repellent coatings (silicon, acrylics), consolidants.

  • Coatings: Paints, stucco, thin stone veneers.

  • Design Considerations: Proper drainage, avoiding direct water contact, using dense stones.

II. BRICKS

Classification of Bricks

Manufacturing Process of Bricks

1. Preparation of Clay: Unloading → Removing topsoil → Weathering → Blending → Adding water → Tempering (to achieve plasticity).

2. Moulding:

   • Hand Moulding: Ground moulding (bricks on ground), Table moulding (bricks on stock board).

   • Machine Moulding: Plastic (extrusion), Dry (pressing).

3. Drying: Remove moisture to prevent cracking during burning. Natural (air) or artificial (dryers). 7-14 days.

4. Burning: In clamps (temporary) or kilns (permanent: intermittent, continuous). Key stages: Dehydration (100-400°C), Decomposition (400-900°C), Vitrification (900-1200°C), Annealing (cooling).

   • Well-burnt Bricks: Hard, metallic sound, sharp edges, uniform red colour, low water absorption.

Properties of Good Bricks

• Physical Properties:

  • Colour: Uniform deep red/pink.

  • Shape & Size: Regular, rectangular, sharp edges.

  • Sound: Metallic ring when struck.

  • Hardness: Resistant to finger nail scratch.

  • Structure: Homogeneous, no visible salts.

• Engineering Properties (IS Standards):

  • Compressive Strength: > 75 kg/cm² (First Class).

  • Water Absorption: < 20% by weight (First Class <12%).

  • Efflorescence: Nil to slight (Soda/vanished salts).

  • Thermal Conductivity: Moderate (provides some insulation).

  • Dimensional Tolerance: Within ±3% for length, ±6% for width.

[!TIP] Common Pitfall: Do not confuse efflorescence (white salt deposits) with efflorescence (the process). It's a defect indicating soluble salts.

III. TIMBER AND WOOD PRODUCTS

Engineering Properties of Timber

• Mechanical: Strength (compressive, tensile, bending), stiffness, elasticity (modulus of elasticity).

• Physical: Density (varies with moisture), Moisture Content (MC) (critical: 8-12% for service), Shrinkage & Swelling (anisotropic - tangential > radial > longitudinal).

• Durability: Natural resistance to fungi/insects (e.g., teak high, sal moderate). Durability class (I-V).

• Workability: Ease of cutting, nailing, finishing.

• Aesthetic: Grain pattern, colour, texture.

Defects in Timber

• Natural Defects:

  • Knots: Branch bases. Effect: Reduce strength, cause irregular seasoning.

  • Shakes: Cracks (heart, star, cup, ring). Effect: Reduce durability, allow moisture/insect entry.

  • Warping: Distortion (bow, crook, twist, cup). Effect: Difficult to use, poor joints.

  • Torsion: Twist along length.

  • Burls, Gum pockets.

• Defects due to Fungi/Insects:

  • Fungi: Dry rot, wet rot (require moisture >20%).

  • Insects: Termites, beetles, borers.

  • Effect: Severe loss of section, complete disintegration.

Timber Seasoning

• Need & Importance:

  • Reduce MC to equilibrium with environment (8-12%).

  • Prevent/ minimize defects (warping, splitting, shrinkage).

  • Increase strength & durability (dry timber stronger).

  • Reduce weight, prevent fungal/insect attack.

• Methods:

  • Natural Seasoning (Air Drying): Stacked with separators, shaded, ventilated. Slow (months-years), low cost, limited to 15-20% MC reduction.

  • Artificial Seasoning:

    • Kiln Seasoning: Controlled temp/humidity. Fast (days-weeks), uniform, to 4-8% MC. Common.

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

    • Electrical Seasoning: Passing high-frequency current. Fast, uniform, expensive.

Wood Substitutes and Wood Products

• Need: Scarcity of good timber, cost, uniformity, large sizes, specific properties.

• Products:

  • Plywood: Layers (veneers) bonded at right angles. Strong, stable, resistant to splitting. Used for furniture, doors, partitions.

  • Blockboard/Battenboard/Laminboard: Core of strips (blocks/battens/laminations) with face veneers. Used for panels, partitions, doors.

  • Fibreboard/Hardboard: Made from wood fibres (wet/dry process). Dense, uniform. Used for panels, furniture, insulation.

  • Particle Board: Wood particles + resin. Cheaper, less strong. Used for furniture, underlayment.

  • MDF (Medium Density Fibreboard): Fine fibres, very uniform, smooth. Excellent for machining, painting. Used for furniture, cabinets.

  • Gypsum Boards (Plasterboards):

    • Regular: Core of gypsum plaster between paper. Used for partitions, ceilings.

    • Moisture-Resistant (MR): Water-repellent core. Used in bathrooms, kitchens.

    • Fire-Resistant (FR): Special core/glass fibres. Used for fire-rated assemblies.

IV. GLASS

Nature, Structure, and Composition

• Nature: Amorphous solid (non-crystalline). Atomic/molecular arrangement is disordered like liquid but rigid.

• Structure: Random, three-dimensional network of SiO₄ tetrahedra. Network modifiers (Na₂O, CaO) break network, lower melting point.

• Basic Composition (% by weight):

  • Silica (SiO₂): 70-75% (network former).

  • Soda Ash (Na₂CO₃): 12-15% (flux/modifier).

  • Limestone (CaCO₃): 10-12% (stabilizer, reduces solubility).

  • Other: Alumina (Al₂O₃), magnesia (MgO) for durability.

Properties of Glass

• Optical: Transparency (varies with thickness/composition), refraction, reflection.

• Thermal: Low thermal conductivity, high thermal expansion (risk of thermal shock), softening point.

• Mechanical: Brittle, high compressive strength, low tensile strength, hard, scratch-resistant.

• Chemical: Highly resistant to most chemicals, except hydrofluoric acid and alkalis.

Types of Glass

• Based on Composition:

  • Soda-Lime Glass: 90% of production. Cheap, good for windows, bottles.

  • Borosilicate Glass: Low thermal expansion (Pyrex). Lab ware, cookware.

  • Lead Glass: High refractive index, brilliance. Optical lenses, decorative.

  • Aluminosilicate Glass: High strength, thermal resistance. Touchscreens, high-temp applications.

• Based on Application/Processing:

  • Float Glass: Flat, clear, standard for windows.

  • Tempered/Toughened: Heated then quenched. 4-5x stronger, breaks into granules.

  • Laminated: Two+ layers with PVB interlayer. Safety, security, sound insulation.

  • Insulated (IGU): Two+ panes with air/argon gap. Thermal insulation.

  • Wired: Wire mesh embedded. Fire-resistant, safety.

  • Colored/Tinted: Metal oxides added. Solar control, aesthetics.

Coatings on Glass

• Purpose: Modify energy efficiency, durability, aesthetics, safety.

• Types & Effects:

  • Reflective (Solar Control): Metallic coating (e.g., silver). Reflects solar radiation, reduces heat gain/glare.

  • Low-Emissivity (Low-E): Thin metallic oxide layer. Reflects internal radiant heat back inside (winter), blocks solar heat (summer). Improves U-value.

  • Self-Cleaning: Photocatalytic (TiO₂) coating breaks dirt; hydrophilic causes water to sheet, washing dirt away.

  • Anti-Reflective (AR): Reduces surface reflection, increases light transmission.

[!TIP] Exam Focus: Know the difference between Reflective (solar control) and Low-E (thermal radiation control) coatings. Both improve energy efficiency but via different mechanisms.

V. PIPES AND PLUMBING MATERIALS

Properties and Applications of Specific Pipes

• PVC Pipes (Polyvinyl Chloride):

  • Properties: Lightweight, corrosion-resistant, smooth bore (low friction), easy to join, cheap. Rigid (uPVC) or flexible.

  • Types: uPVC (unplasticized - rigid, pressure pipes), CPVC (chlorinated - higher temp resistance, hot water).

  • Applications: Water supply (uPVC/CPVC), drainage, waste, conduits, chemical handling.

• Asbestos Cement (AC) Pipes:

  • Properties: Strong, rigid, corrosion-resistant, good for underground. Historical use.

  • Health Concern: Asbestos fibres are carcinogenic when inhaled (during cutting/breaking). Now banned/restricted in many countries.

  • Current Status: Largely replaced by PVC, HDPE, ductile iron.

• Stoneware Pipes (Vitrified Clay Pipes):

  • Properties: Highly vitrified (glassy), very hard, excellent chemical resistance, brittle.

  • Applications: Sewerage, drainage, acidic/alkaline waste disposal. Jointed with flexible seals.

• Chloride Pipes (Likely CPVC or HDPE/PP):

  • Interpretation: Term may refer to CPVC (see above) or HDPE/PP pipes for chemical service.

  • HDPE/PP Properties: Excellent chemical resistance (chlorides, acids), flexible, weldable.

  • Applications: Process piping, chemical plants, aggressive water supplies.

VI. FLOORING AND ROOFING MATERIALS

Flooring Materials

Roofing Materials

[!TIP] Key Point: Selection depends on climate (rain, sun, wind), slope, cost, durability, insulation needs, and fire rating.

VII. PAINTS, VARNISHES, AND POLISHES

Characteristics of an Ideal Paint

• Good flow and leveling.

• High hiding power (opacity).

• Good coverage (area per litre).

• Durability (weathering, abrasion, chemical resistance).

• Strong adhesion to substrate.

• Excellent color retention.

• Easy application (brush, roller, spray).

• Cost-effective.

• Drying in reasonable time.

Composition of Oil Paints

1. Vehicle/Oil: Binder (linseed, soybean, tung oil). Dries to hard film.

2. Pigment: Provides colour, opacity, protection (e.g., TiO₂ white, ochres, carbon black).

3. Solvent/Thinner: Adjusts viscosity (turpentine, mineral spirits, water for emulsions).

4. Fillers/Extenders: Inexpensive materials (talc, whiting, barytes) to bulk, improve texture.

5. Driers: Metallic soaps (cobalt, manganese) that catalyse oil oxidation/drying.

Types of Paints and Finishes

• Enamels: Oil-based, hard, glossy, durable film. Used on metal (railings), wood trim, exterior.

• Distempers: Water-based, chalk/glue binder, matte finish. Cheap, for interior walls (plastered). Poor durability, washable.

• Water Wash / Whitewash: Slaked lime + water (+ glue/sugar). Cheap, temporary, disinfectant. For exterior walls, farms.

• Varnish: Resin (natural: shellac, copal; synthetic: polyurethane) + solvent + oil. Transparent, hard, glossy protective film. Used on wood, metal.

• French Polish: Shellac dissolved in alcohol applied in many thin layers with pad. High gloss, traditional, shows grain. Used on fine furniture.

• Wax Polish: Beeswax/carnauba wax in solvent. Soft sheen, protective, easy repair. Used on floors, furniture.

Painting Process for Wooden Surfaces

1. Surface Preparation: Clean, sand (to smooth, remove gloss), remove dust. Fill holes/cracks (wood filler). Knotting: Apply knotting solution (shellac/alcohol) over knots to prevent resin bleed-through.

2. Priming: Apply primer/sealer. Purpose: seal pores, provide adhesion, block stains, uniform surface.

3. Undercoating: 1-2 coats of undercoat (often pigmented). Builds film, provides base for topcoat.

4. Finishing: Apply 2+ coats of final paint/enamel/varnish. Sand lightly between coats.

5. Specific Considerations:

   • Moisture Content: Wood should be at service MC (8-12%).

   • Environment: Avoid painting in high humidity/damp.

   • Number of Coats: Follow manufacturer, ensure full coverage.

   • Sanding: Essential between coats for smooth finish.

   • Topcoat Choice: Based on exposure (exterior vs interior), desired finish (gloss/matte).

VIII. BITUMINOUS AND POLYMER MATERIALS

Tar and Bitumen

• Tar: By-product of coal/carbonization. Viscous, black, waterproof, adhesive, thermoplastic. Disadvantages: Strong odour, volatile components, less stable to weathering/UV than bitumen. Uses: Road surfacing (older), waterproofing, preservative.

• Bitumen: Petroleum residue or natural. Grades: Penetration Grade (hardness), Viscosity Grade, Performance Grade (PG). Properties: Waterproof, adhesive, thermoplastic, durable. Uses: Road construction (binder), roofing felt, waterproofing, damp-proof courses.

Polyvinyl Chloride (PVC) and Ultra Poly Vinyl (uPVC)

• PVC: Rigid or flexible (with plasticizers). Good chemical resistance, weatherability, flame retardant.

• uPVC (Unplasticized PVC): Rigid, high strength, UV resistant, low thermal conductivity.

• Applications in Construction:

  • Pipes: Water supply, drainage, conduits (see Section V).

  • Window/Door Frames: Low maintenance, good insulation, weather resistant.

  • Siding/Cladding: Weatherboards, panels.

  • Flooring: Vinyl composition tiles (VCT).

IX. SPECIALIZED FUNCTIONAL MATERIALS

Thermal Insulating Materials

• Importance: Reduce heat transfer → energy savings, thermal comfort, prevent condensation.

• Types & Characteristics:

  • Fibrous: Glass wool, rock wool (mineral wool). Trapped air in fibres. Good thermal resistance, fire-resistant (mineral wool), sound absorbent.

  • Cellular: Expanded polystyrene (EPS), extruded polystyrene (XPS), polyurethane (PUR) foam, cork. Trapped air in cells. Low thermal conductivity, moisture resistance (XPS), rigid.

  • Reflective: Aluminum foil, metallized films. Reflect radiant heat. Used in attics, as part of assemblies.

  • Mineral Loose Fill: Vermiculite, perlite (exfoliated). Lightweight, fire-resistant, used in loose-fill or plaster.

Sound Proofing (Acoustic) Materials

• Principles:

  1. Mass Law: Increase surface mass (dense materials like concrete, brick) to block sound.

  2. Absorption: Use porous materials (fibreglass, foam) to absorb sound energy within room.

  3. Decoupling: Break mechanical connection (resilient channels, double walls) to stop structure-borne sound.

• Types & Applications:

  • Dense Barriers: Concrete, brick, lead sheets (mass).

  • Porous Absorbers: Fibreglass, acoustic foam, mineral wool (absorption).

  • Resonant Absorbers: Tuned panels for specific frequencies.

  • Specialized Panels: Acoustic ceiling tiles, perforated metal with backing.

Waterproofing Materials

• Types & Mechanisms:

  • Integral Waterproofing: Admixtures (hydrophobic, crystalline) added to concrete. Make concrete matrix water-repellent.

  • Surface-Applied Membranes:

    • Bituminous: Sheets or hot-applied. Flexible, adhesive.

    • Polymeric: PVC, EPDM, TPO sheets. Welded, flexible.

    • Cementitious: Slurry coatings (with acrylic/polymer modification). Bonded to substrate.

  • Coatings: Epoxy, polyurethane, acrylic coatings. Form seamless, adherent film.

  • Injection Grouts: Polyurethane, acrylic gels. Injected into cracks to seal.

• Selection: Based on structure (basement, roof, tank), water head (pressure), substrate (concrete, masonry), movement, chemical exposure.

X. METALS AND ALLOYS

Aluminium

• Key Properties:

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

  • Excellent corrosion resistance (forms protective oxide film).

  • Good conductor of heat/electricity.

  • Ductile, malleable.

  • Non-magnetic, non-sparking.

  • Reflective.

• Forms in Market: Ingots, billets, sheets, extrusions, castings, foils.

• Uses in Construction:

  • Window/door frames (powder-coated).

  • Curtain wall systems (panels, mullions).

  • Roofing, cladding (composite panels).

  • Structural members (trusses, bridges - alloyed).

  • Ladders, railings, solar panel frames.

Steel

• Structural Properties:

  • High strength-to-weight ratio.

  • Ductility: Can deform significantly before failure (energy absorption).

  • Toughness: Ability to absorb energy and resist fracture.

  • Uniformity: Consistent properties.

  • High tensile and compressive strength.

• Types in Construction:

  • Mild Steel (MS): Low carbon (0.15-0.25%). Ductile, weldable. Used for general structural, reinforcement (older).

  • HYSD (High-Yield Strength Deformed): Reinforcing bars with ribs. Higher yield strength than MS.

  • TMT Bars (Thermo-Mechanically Treated): High strength, ductility, earthquake resistant. Modern reinforcement standard.

  • Structural Steel Sections: I-beams, channels, angles, tubes (H, I, C, RHS). Used in frames, trusses.

XI. CONCRETE

Ingredients and Chemical Composition

1. Cement (Portland):

   • Main compounds: Tricalcium Silicate (C₃S), Dicalcium Silicate (C₂S), Tricalcium Aluminate (C₃A), Tetracalcium Aluminoferrite (C₄AF).

   • Hydration: C₃S → early strength; C₂S → later strength.

2. Aggregates: Inert filler (sand - fine, gravel/crush - coarse). 60-75% volume.

3. Water: For hydration (chemical reaction with cement). Water-cement ratio (w/c) crucial for strength/durability.

4. Admixtures: Chemical additives (plasticizers, superplasticizers, retarders, accelerators, air-entrainers).

Types of Concrete

• Based on Strength:

  • Ordinary (M5-M20)

  • Standard (M25-M55)

  • High Strength (>M60)

• Based on Density:

  • Heavyweight: High-density aggregates (barite, magnetite). For radiation shielding.

  • Lightweight: Lightweight aggregates (expanded clay, shale, slate) or cellular (foamed). For insulation, reduced dead load.

• Based on Use:

  • Reinforced Concrete (RC)

  • Prestressed Concrete (PSC)

  • Precast Concrete

  • Shotcrete/Gunite

  • Vacuum Concrete, Roller-Compacted Concrete (RCC)

Grades of Concrete (IS 456)

• Denoted by M followed by characteristic compressive strength in N/mm² (MPa) at 28 days.

• Examples:

  • M5 → 5 MPa (≈50 kg/cm²)

  • M10 → 10 MPa

  • M15 → 15 MPa

  • M20 → 20 MPa (common for RCC)

  • M25, M30, M35, M40, M45, M50, M55, M60, M65, M70, M75, M80.

• Characteristic Strength: Strength below which not more than 5% of test results are expected to fall.

Special Concretes (Any Three)

1. High-Performance Concrete (HPC):

   • Specifications: w/c ≤ 0.35, high cement content, silica fume, superplasticizer, low permeability.

   • Uses: Bridges, high-rise columns, marine structures.

2. Self-Compacting Concrete (SCC):

   • Specifications: High flowability (slump flow 650-800 mm), no segregation, no vibration needed.

   • Uses: Congested reinforcement, complex shapes, architectural concrete.

3. Fibre Reinforced Concrete (FRC):

   • Specifications: Discrete fibres (steel, glass, synthetic, natural) added (0.5-2% by vol.).

   • Uses: Industrial floors, pavements, shotcrete, tunnel linings (improves toughness, crack control).

4. Polymer Concrete:

   • Specifications: Binder is polymer resin (epoxy, polyester, furan). No cement.

   • Uses: Chemical-resistant floors, bridge decks, rapid repair, decorative.

XII. SPECIFIC MATERIALS (SHORT NOTES)

• Marble: Metamorphic (recrystallized limestone). Takes excellent polish, durable, porous (stains), expensive. Used for flooring, wall cladding, sculpture, vanity tops.

• Kota Stone: Fine-grained, siliceous limestone from Rajasthan. Hard, durable, slip-resistant when polished, affordable. Used for flooring (commercial, public buildings), pathways, coping.

• Asbestos: Fibrous silicate mineral. Heat-resistant, insulating, strong. Historical uses: Asbestos cement sheets/pipes, insulation, brake linings. Health Hazard: Inhaled fibres cause asbestosis, lung cancer, mesothelioma. Phase-out: Banned/restricted globally. Use only with extreme precautions/abatement.

• Ultra Poly Vinyl (uPVC): Rigid PVC. High strength, UV stable, low thermal conductivity, corrosion-resistant. Uses: Window/door profiles, pipes (pressure), siding, decking.

• Chloride Pipes (CPVC/HDPE): CPVC: Chlorinated PVC, higher temp resistance (up to 90°C). For hot water. HDPE: High-density polyethylene. Flexible, chemical-resistant, joined by welding. For chemical/water supply, gas.

• Bitumen: Viscous, black, thermoplastic binder. Grades: Penetration (80/100, 60/70), Viscosity (VG-10, VG-30). Uses: Road construction (asphalt), roofing felt, waterproofing, DPC.

• Sound Proofing Materials: (See Section IX). Principles: Mass, absorption, decoupling. Materials: Dense (concrete), porous (fibreglass), resonant panels, double walls with insulation.

• Water Proofing Materials: (See Section IX). Types: Integral admixtures, surface membranes (bituminous, polymeric, cementitious), coatings (epoxy), injection grouts.

• Thermal Insulating Materials: (See Section IX). Types: Fibrous (glass wool), Cellular (polystyrene foam), Reflective (aluminum foil), Mineral (vermiculite). R-value/thermal conductivity key.

[!TIP] Final Exam Strategy: For short notes (4-5 marks), state definition, key properties, and 1-2 main applications. For 7-mark questions, provide classification, detailed properties/process, advantages/disadvantages, and applications. Always relate properties to construction use.