A black or dark brown viscous material
composed principally of high molecular weight hydrocarbons
having adhesive properties
derived from petroleum either by natural or refinery processes
substantially soluble in carbon disulphide
what is asphalt?
A mixture of bitumen and mineral filler.
adhesives, waterproofing agents
is simply the residue left over from petroleum refining
what is binder?
A material used to hold solid particles together, i.e. bitumen or tar
what is the binder properties?
Adhesion - Bituminous materials adhere to clean dry surfaces.
Viscosity All bituminous materials are viscous, i.e. when subject to a long term load they deform continuously.
Softening point This is the temperature at which the binder softens to a pre-determined point
what are the general effect after adding aggregate to a binder ?
The cost is reduced
The strength is generally increased
If the mix has to be laid hot the aggregate must also be heated (at considerable cost)
May fail due to loss of adhesion between aggregate and binder
what are the test carry out for testing of bituminous mixture?
• Penetration test This test is similar in principle to the penetration test for binders but on a larger scale. The steel pin is 6.35mm (0.25") diameter and the load is 10 N/mm2
• Marshall test In this test asphalt mixes are made at several different binder contents. Cylindrical specimens are loaded in compression on their curved surfaces. The maximum load (stability) and the deformation (flow) is recorded.
• Dissolution of binder There are a number of BS tests which involve dissolution of the binder in solvents. The mix proportions and the nature of the binder may be determined.
• Percentage refusal density This test is used to measure compaction in road construction. The density of a core from the road is compared with the maximum density achievable using heat and heavy compaction (the refusal density)
what are the road construction types?
Wearing course
↓
Base course
↓
Roadbase
↓
Sub-base
↓
Subgrade (limestone)
↓
Base course
↓
Roadbase
↓
Sub-base
↓
Subgrade (limestone)
Wearing course
↓
Roadbase
↓
Lower base (crack resistant)
↓
Sub-base
↓
Subgrade (limestone)
what are the surfacing materials?
Hot rolled asphalt: Coarse aggregate dispersed in a mortar composed of sand, filler and bitumen. This is gap graded.
Asphaltic concrete: Asphalt in which the aggregate particles are continuously graded to form an interlocking structure.
Surface dressing: Sprayed bitumen binder with stone chippings rolled on. This is used for repair work.
Slurry surfacings and micro asphalts: Bitumen emulsions with selected aggregate combinations. Also used for repair.
Stone mastic asphalt: gap graded asphalt composed of a coarse crushed aggregate skeleton with mastic mortar.
what are the common failure mechanisms?
• Wearing course: Rutting (shear failure) Potholes (bond failure) loss of skid resistance (viscous flow) • Lower courses: Cracking (Fatigue failure) Breakdown due to failure of lower courses (e.g. reflected cracking from dry-lean concrete)
what are the application for the surface material?
Roads
Tanking - tanking a basement, asphalt troweled onto walls after casting
Roofing - bitumen roofing,
Hot rolled asphalt: Coarse aggregate dispersed in a mortar composed of sand, filler and bitumen. This is gap graded.
Asphaltic concrete: Asphalt in which the aggregate particles are continuously graded to form an interlocking structure.
Surface dressing: Sprayed bitumen binder with stone chippings rolled on. This is used for repair work.
Slurry surfacings and micro asphalts: Bitumen emulsions with selected aggregate combinations. Also used for repair.
Stone mastic asphalt: gap graded asphalt composed of a coarse crushed aggregate skeleton with mastic mortar.
what are the common failure mechanisms?
• Wearing course: Rutting (shear failure) Potholes (bond failure) loss of skid resistance (viscous flow) • Lower courses: Cracking (Fatigue failure) Breakdown due to failure of lower courses (e.g. reflected cracking from dry-lean concrete)
what are the application for the surface material?
Roads
Tanking - tanking a basement, asphalt troweled onto walls after casting
Roofing - bitumen roofing,
