Asphalt, Bitumen, Tar and Miscellaneous Materials

Asphalt is a mixture of bitumen with mineral matter (sand, filler or aggregate), either natural (rock asphalt, lake asphalt) or artificial. Bitumen is the sticky black hydrocarbon binder, obtained from crude oil refining (residue) or natural deposits, and is the main binding component of asphalt.

In American usage "asphalt" means what is called "bitumen" elsewhere; the above is the IOE textbook difference.

Asphalt is a dark brown to black, sticky, waterproof material made of bitumen mixed with mineral matter (sand, stone chips or filler). It is obtained from natural deposits or made artificially.

Types of asphalt

1. Natural asphalt: Rock asphalt (porous limestone or sandstone soaked in bitumen, e.g. from Switzerland), lake asphalt (Trinidad lake) and asphaltic sand.
2. Artificial (refined) asphalt: Made in plants by mixing refined bitumen with graded aggregates and filler: hot-mix asphalt, mastic asphalt, cut-back and emulsified asphalt.

Properties

• Dark colour, solid or semi-solid at normal temperature.
• Binds well to aggregate and is highly adhesive.
• Waterproof and durable under weather.
• Thermoplastic: softens when heated, hardens on cooling.
• Resists acids, alkalis and weathering; not affected by moisture.
• Elastic and flexible; does not crack easily with small movements.
• Good electrical and sound insulation; low cost.
• Burns slowly with smoke.

Uses

Glass is a hard, brittle, transparent material made by fusing silica sand with soda ash and limestone, then cooling it rapidly. Common types:

Asphalt is a mixture of bitumen and mineral matter, found naturally or made artificially. Tar is a dark viscous liquid obtained by destructive distillation of coal, wood or other organic matter.

Plastics are synthetic organic materials (polymers) that can be moulded under heat and pressure. They are widely used today for these reasons:

1. Light weight: Density is about 900–1500 kg/m³, giving easy handling, transport and lower dead load.
2. Corrosion and chemical resistance: Plastics do not rust or rot and resist water, acids and alkalis, so they last longer in pipes, tanks and fittings.
3. Easy to mould and install: Complex shapes are made quickly by moulding or extrusion; pipes, sheets and fittings are quickly joined.
4. Low cost: Cheaper overall, with low maintenance and mass production.
5. Good insulation: Poor conductors of heat and electricity, used for wire insulation, thermal insulation and switches.
6. Colour and finish: Can be made in any colour or transparency; needs no painting.
7. Strength-to-weight ratio is high when reinforced (e.g. GRP, FRP).
8. Water-tightness: Smooth, non-porous surface gives low friction in pipes and waterproofing in membranes.
9. Recyclable (thermoplastics) and long life.

Uses: pipes (PVC, HDPE), water tanks, doors and windows (uPVC), flooring, damp-proof sheets, paints, adhesives and insulation.

Properties of glass

• Transparent (or translucent), allowing light to pass through, with a smooth, glossy surface.
• Hard but brittle: Strong in compression but weak in tension; it breaks suddenly without warning.
• Chemical resistance: Not attacked by water, air or most acids (except hydrofluoric acid); it does not corrode.
• Non-porous and impervious: Easy to clean and hygienic.
• Poor conductor of heat and electricity: Good insulator.
• Low thermal expansion (for borosilicate), but ordinary glass may crack with sudden temperature change.
• Can be coloured, moulded, blown, drawn, cut and polished when hot.
• Recyclable. Density about 2500 kg/m³.
• Affected by alkalis over a long time.

Uses

• Glazing of windows, doors, ventilators, skylights, curtain walls and partitions.
• Glass blocks and tiles for walls and floors.
• Mirrors, shop fronts, table tops.
• Insulation in glass wool and fibre-glass reinforced plastics.
• Safety applications: toughened and laminated glass for doors, stairs, railings.
• Lighting fixtures, pipes, tanks and laboratory equipment.

Insulating materials are materials that resist the flow of heat, sound or electricity, so that the interior of a building stays comfortable. They have low thermal conductivity and are usually light and porous (trapping air).

Types by purpose

1. Thermal insulating materials: Reduce heat gain or loss through walls and roofs.
   • Glass wool and rock (mineral) wool
   • Expanded polystyrene (thermocol) and polyurethane foam
   • Cork, cellular concrete, AAC blocks, vermiculite, perlite
   • Straw and wood fibre boards
2. Sound (acoustic) insulating materials: Absorb or block sound for quiet rooms. Examples: acoustic tiles, perforated boards, mineral wool, cork sheets, heavy curtains, carpets.
3. Electrical insulating materials: Prevent leakage of current: PVC, rubber, porcelain, mica, glass and bakelite.

Requirements

• Low thermal conductivity, light weight and low cost.
• Fire resistance, moisture and vermin resistance.
• Strength enough to be handled, and easy to fix.
• Durable and non-toxic.

Uses: insulating roofs and cold stores, hot water pipes, walls of cold-region buildings, and auditoriums for acoustics.

Gypsum is hydrated calcium sulphate ($CaSO_4 \cdot 2H_2O$). On heating at about 130–160 °C it loses water to form plaster of Paris ($CaSO_4 \cdot \tfrac{1}{2}H_2O$), which sets quickly when mixed with water.

Products available and their applications

Advantages: fire resistance, good thermal and sound insulation, smooth surface, quick setting. It is not suited to damp areas (unless water-resistant board is used).

Bitumen is a black, sticky, hydrocarbon binder obtained from refining petroleum or from natural deposits. Tar is a dark viscous liquid obtained from destructive distillation of coal, wood or similar organic matter.

In short: asphalt is the bound mixture, bitumen is the pure binder from petroleum, and tar is a coal or wood distillate that is more temperature-sensitive and less durable.

Asphalt

A mixture of bitumen with mineral matter (sand, stone dust, aggregate), natural (rock asphalt, lake asphalt) or artificial. Best applications: wearing courses of roads and airport runways (hot-mix asphalt), mastic asphalt for flat roof waterproofing, basement tanking and floors.

Bitumen

A black, sticky, waterproof hydrocarbon substance, obtained as residue in petroleum refining or from natural deposits, soluble in carbon disulphide. Best applications: binder in road construction (penetration grades 60/70, 80/100), tack and prime coats, damp-proof courses, waterproofing membranes, bituminous felts and paints.

Tar

A dark brown to black viscous liquid obtained by destructive distillation of coal, wood or peat. Best applications: surface dressing and priming on roads, coating of timber and pipes as a preservative, roofing felt, and road patching.

Bitumen is a black, sticky hydrocarbon used as a binder and waterproofing material. Types:

1. Natural bitumen: Found in nature as lake asphalt (e.g. Trinidad), rock asphalt, or asphaltic sand mixed with minerals.
2. Petroleum (refined) bitumen: The residue left after distilling crude oil.
   • Penetration grade (paving) bitumen: 30/40, 60/70, 80/100 grades; used in roads.
   • Viscosity grade bitumen: VG-10, 20, 30, 40 as per IS 73.
3. Cutback bitumen: Bitumen dissolved in a volatile solvent (petrol, kerosene, diesel) so it can be applied cold; the solvent evaporates leaving bitumen.
   • Rapid curing (RC), medium curing (MC) and slow curing (SC) types.
   • Used for prime coat, tack coat and surface dressing.
4. Bituminous emulsion: Bitumen droplets suspended in water with an emulsifier. Cationic, anionic types; used for surface dressing, tack coat and patching in wet weather.
5. Blown (oxidised) bitumen: Air is blown through hot bitumen to make it hard, with higher softening point and low temperature susceptibility. Used for roofing, damp-proofing and pipe coating.
6. Modified bitumen: Polymer or rubber added (PMB, CRMB) for better strength in heavy traffic.
7. Bitumen felt: Fibre sheets saturated in bitumen, used for roofing and DPC.

Plastics are polymers that can be moulded under heat and pressure. They are of two main types:

Thermoplastics

Soften on heating and harden on cooling, and the process is repeatable. They can be remoulded and recycled. Examples:

• Polyvinyl chloride (PVC): pipes, conduits, floor tiles
• Polyethylene (PE/HDPE): water tanks, DPC sheet, pipes
• Polystyrene: insulation boards (thermocol)
• Acrylic (PMMA): sheets, skylights, glazing
• Polypropylene, nylon

Thermosetting plastics

Set permanently on first heating and cannot be softened again; they have cross-linked molecules, are harder and heat-resistant. Examples:

• Bakelite (phenol formaldehyde): switches, handles
• Urea formaldehyde: adhesives, laminates
• Melamine formaldehyde: laminates (Formica), tableware
• Epoxy resin: adhesives, floor coatings
• Polyester resin: fibre-glass reinforced plastics (GRP)

A polymer is a large molecule (macromolecule) formed by joining many small repeating units called monomers by chemical bonds. Its relative molecular mass is usually very high, in thousands to millions. Examples: polyethylene from ethylene, PVC from vinyl chloride, and natural polymers like rubber, cellulose and protein.

• Polymerization is the chemical process of joining monomers into the polymer, by addition (e.g. ethylene to polyethylene) or condensation (e.g. phenol and formaldehyde to Bakelite, with water released).
• Polymers can be natural (rubber, wood, cellulose) or synthetic (plastics, synthetic fibres, resins).
• Based on structure they may be linear, branched or cross-linked, which decides whether they are thermoplastic or thermosetting.

 n [CH2=CH2]  --heat,pressure,catalyst-->  [-CH2-CH2-]n
   ethylene                                  polyethylene

Polymers (plastics, rubbers, resins) are very widely used in building.

Properties

• Light weight and high strength-to-weight ratio.
• Good resistance to water, chemicals, corrosion and rot.
• Good electrical and thermal insulation.
• Easily moulded and can be made in many shapes and colours.
• Low cost and low maintenance.
• Low stiffness and softening with heat; thermoplastics creep and lose strength at high temperatures.
• Poor fire resistance (they burn and give toxic smoke) and weathering by UV rays unless stabilised.
• Thermal expansion is larger than for metals.

Uses in building

Definition

Sound insulating materials are materials used in walls, floors, ceilings and partitions to absorb sound energy or stop its transmission, so that noise from outside or between rooms is reduced and a room has good acoustics.

Requirements

1. Porous and light (for absorption): Sound enters the pores and is changed to heat.
2. Heavy and dense (for blocking): Mass stops transmission through walls.
3. High absorption coefficient over a wide range of frequencies.
4. Fire resistant and non-combustible.
5. Resistant to moisture, termites and fungus.
6. Durable, easy to fix and clean, and low in cost.
7. Good appearance so that it can be used on exposed surfaces.

Examples

Autoclaved Aerated Concrete (AAC) blocks are lightweight, precast, cellular blocks made from fly ash (or sand), cement, lime, gypsum and water, with a small amount of aluminium powder as the foaming agent. The aluminium reacts with lime to give hydrogen gas, which forms millions of tiny air cells. The mix is cut into blocks and cured in an autoclave (steam at about 180 °C and 12 bar pressure) for 8–12 hours.

Properties

• Density 500–800 kg/m³ (about one-third of clay brick), so dead load is reduced.
• Compressive strength about 3–4.5 N/mm² (IS 2185 Part 3).
• Good thermal insulation, sound absorption and fire resistance (2–4 hours).
• Accurate sizes (e.g. 600 × 200 × 100–300 mm), so thin joints and less plaster are needed.
• Easily cut, nailed, drilled and chased; quick construction.

Uses and limits

Used for non-load-bearing partitions and infill walls in framed buildings, and in load-bearing low rise buildings. Water absorption is higher than brick, so plastering and waterproofing are needed on outer walls, and special mortar (adhesive) is used.

A composite material is made by combining two or more different materials (a matrix and a reinforcement) so that the product has better properties than any of the components. Examples: reinforced concrete, FRP, GRP, plywood, fibre cement, steel-concrete composite.

Reasons for their predominant use

1. High strength-to-weight ratio: Fibres (glass, carbon) in resin give strength like steel at a fraction of the weight.
2. Tailor-made properties: Fibres, matrix and layout can be chosen to give the needed strength, stiffness or insulation.
3. Durability: They do not rust or rot, and resist chemicals and weather better than steel and timber.
4. Combines advantages: Concrete resists compression and steel resists tension in RCC.
5. Easily moulded: Complex shapes and large components are made by moulding and cast-in-place.
6. Low maintenance and long life.
7. Natural materials are scarce: Good timber and stone are limited, expensive and uneven in quality, whereas composites are uniform and consistent.
8. Better thermal, acoustic and fire performance in several kinds (e.g. sandwich panels).

Limit: They may cost more at first, and some (FRP) cannot be easily recycled or repaired.

Bitumen is a black or dark brown, sticky, waterproof mixture of hydrocarbons, obtained as the residue after distillation of crude petroleum or found as natural deposits. It is soluble in carbon disulphide and is used as a binder and waterproofing material in roads and roofs.

Tar is a dark brown to black viscous liquid obtained by destructive distillation of coal, wood or peat in the absence of air. It is used for road surface dressing, priming, and as a preservative for timber and pipes. It is more temperature-sensitive and less durable than bitumen.

Asphalt

• Wearing course (hot-mix asphalt) of roads, airport runways and parking areas.
• Mastic asphalt for flat roofs, basements, bridge decks and tanking.
• Floors of warehouses and factories, and footpaths.

Bitumen

• Binder for bituminous roads (macadam, concrete), and for tack and prime coats.
• Waterproofing and damp-proof courses, bituminous felts and membranes.
• Paints for steel and pipes, joint filler and sealant.

Tar

• Surface dressing and priming coat on roads.
• Preservative coating on timber (fence posts, sleepers) and underground pipes.
• Tarred felt for roofing, and patching of potholes.

Bitumen is a black, sticky, viscous hydrocarbon material obtained from crude petroleum distillation residue or natural deposits. It is a good binder and waterproofing agent.

Properties

• Black to dark brown, solid to semi-solid at normal temperature and softens on heating (thermoplastic).
• Highly adhesive: sticks well to stone aggregate.
• Waterproof, and resists acids, alkalis and salts.
• Soluble in carbon disulphide, carbon tetrachloride and petrol.
• Specific gravity about 1.01–1.06.
• Ductile and flexible, so it can resist small movements without cracking.
• Hardness is measured by the penetration test, consistency by viscosity, heat resistance by softening point (ring and ball), ductility test, flash and fire point.
• Ageing and oxidation slowly harden it.
• Electrical insulator and low cost.

Uses

• Binder for bituminous road surfaces (paving grades 30/40 to 80/100 and VG grades).
• Prime coat, tack coat, surface dressing and patching.
• Waterproofing of roofs, foundations, basements and bridge decks.
• Damp-proof courses and bituminous felt.
• Protective paints for steel, pipes and tanks.
• Joint sealant and filler in concrete pavements.

Tar is a dark, viscous liquid obtained by destructive distillation of coal, wood or peat.

Properties

• Black to dark brown, thin and viscous, with a strong odour.
• Good adhesion to aggregate and quickly penetrates surfaces.
• Waterproof, and resists decay by insects and fungi (preservative).
• Highly temperature-sensitive: soft in heat and brittle in cold.
• Weathers and ages faster than bitumen; toxic and harmful if inhaled or touched.
• Cheap.

Uses

• Priming and surface dressing on roads, and road patching.
• Preservative on timber poles, sleepers and fence posts.
• Coating on iron pipes and tanks to prevent rust.
• Tarred felt and waterproof coating for roofs.

Tar is preferred in parking lots (and similar low-speed areas) mainly because:

• It resists petrol, oil and diesel spills, which dissolve bitumen and asphalt, so the surface does not soften or break up.
• It gives a hard, waterproof surface at low cost and sets quickly.
• It adheres well to the aggregate, and low traffic speeds avoid its temperature problems.

Adhesive

An adhesive is a substance that joins two surfaces together by sticking and holding them by surface attachment and internal strength. Examples: animal glue, starch paste, gum, synthetic resin glues, cement-based adhesive and epoxy. They are used for fixing tiles, laminates, wood joints, flooring and for repair work.

Epoxy

Epoxy is a thermosetting synthetic resin supplied as two parts, resin and hardener. When they are mixed, a chemical reaction forms a very strong, hard, cross-linked solid.

• Excellent adhesion to concrete, metal, glass, wood and stone.
• High strength, small shrinkage, and resistance to water, chemicals and abrasion.
• Used for bonding old and new concrete, crack injection, grouting of anchors, floor coatings, tile adhesives and fibre-reinforced polymers.

Epoxy is therefore a special, high-performance structural adhesive.

A thermosetting plastic is a plastic that becomes hard and permanently rigid on the first heating and moulding because of cross-linking of its polymer chains. It cannot be softened or reshaped by heating again and burns or chars if overheated. Examples: Bakelite, melamine formaldehyde, urea formaldehyde, epoxy resin and polyester resin.

Borosilicate glass

Borosilicate glass is a glass containing silica (about 80%) and boron trioxide (about 13%), with some soda and alumina. It has a very low coefficient of thermal expansion, high chemical resistance and can withstand sudden temperature changes. Example: Pyrex. It is used for laboratory glassware, pipes, ovenware and lighting.

Thermoplastic

A thermoplastic is a plastic that softens on heating and hardens on cooling, and this can be repeated many times without chemical change because the polymer chains are linear and not cross-linked. They can be remoulded and recycled. Examples: PVC, polyethylene, polystyrene, acrylic (PMMA), nylon.

Polymer and polymerization

A polymer is a large molecule made of many repeating small units (monomers) joined by chemical bonds. Polymerization is the chemical process by which monomers combine to form the polymer, by addition polymerization (no by-product, e.g. ethylene to polyethylene) or condensation polymerization (water or another small molecule is released, e.g. Bakelite).

Difference between thermoplastics and thermosetting plastics

In short, the polymer is what is formed and polymerization is how it is formed.

Thermoplastics soften on heating and can be remoulded. Three important ones for civil engineering:

1. Polyvinyl chloride (PVC)

Properties: Strong, rigid (unplasticised uPVC) or flexible (plasticised), chemically resistant, does not rust or rot, low cost, good electrical insulator, self-extinguishing, but softens above about 60–70 °C. Uses: Water supply and drainage pipes, conduits and cable insulation, window and door frames, floor tiles, roofing sheets, water stops and rain-water pipes.

2. Polyethylene (PE: LDPE and HDPE)

Properties: Light, tough and flexible, waterproof, excellent chemical resistance, low water absorption, easy to weld; poor UV resistance unless stabilised. Uses: Water storage tanks, water and gas pipes (HDPE), damp-proof membrane and sheeting, geomembranes for ponds and landfills, and cable covers.

3. Polystyrene (PS, expanded polystyrene or thermocol)

Properties: Light, rigid, transparent in solid form, very good thermal insulation in expanded form, low water absorption, but brittle and burns easily. Uses: Thermal insulation panels for walls, roofs and cold stores, formwork infill, ceiling tiles, lighting diffusers.

Others: acrylic (PMMA) for skylights and glazing, and polypropylene for pipes and fibres.

Plastics are classified into two major groups based on how they behave on heating: thermoplastics and thermosetting plastics.

Popular plastics and uses

Thermoplastics

• PVC: pipes, conduits, flooring, window frames.
• Polyethylene: water tanks, DPC sheets, geomembranes.

Thermosetting plastics

• Bakelite (phenol formaldehyde): electrical switches, sockets, handles, laminates.
• Epoxy resin: adhesives, floor coatings, concrete repair, FRP.

Plastic is a synthetic or semi-synthetic organic material made of long-chain polymers, which can be moulded into a desired shape by heat and pressure and then retains the shape on cooling or setting. They are made from petroleum, natural gas or coal products with additives (fillers, plasticisers, stabilisers and pigments). Plastics are light, corrosion resistant and cheap, and are used for pipes, sheets, tanks, flooring, insulation and fittings. They are of two types: thermoplastic and thermosetting.

Plate glass is flat glass with a ground and polished surface on both sides, giving clear, distortion-free vision. Uses:

• Large windows and shop fronts (show windows) of buildings.
• Glass doors, partitions and curtain walls of offices and malls.
• Mirrors (silvered plate glass) and furniture glass tops.
• Glazing of high quality in vehicles, display cabinets and counters.
• Glass shelves, table tops and interior decorative work.
• Toughened or laminated plate glass for railings, stair treads and safety glazing.