PART 8 BITUMINOUS MATERIALS

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PART 8 BITUMINOUS MATERIALS

• 8.1 Introduction
• Definitions
• Safety
• Production
• 8.2 Binders
• 8.3 Bituminous mixtures
• 8.4 Applications

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Definitions

• Binder A material used to hold solid particles
  together, i.e. bitumen or tar.
•  Bitumen A heavy fraction from oil distillation
  (also occurs as part of natural asphalt).
•  Tar A viscous liquid obtained from
  distillation of coal or wood. Rarely used in
  construction currently in the UK.
• Asphalt A mixture of bitumen and mineral
  filler. Note that Hot Rolled Asphalt is a road
  surfacing material.
• Mastic An adhering asphalt which is placed
  with trowelling.
• Macadam A road construction material with
  binder and coarse aggregate. Tarmacadam was the
  first road surfacing material.

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SAFETY

• The flash point is the temperature at which
  vapour given off from the surface will burn.
• The fire point is the temperature at which the
  binder will burn.
• Water will spread a bitumen fire.
• The materials are generally used at temperatures
  high enough to cause severe burns.
• Both the materials and the vapours are
  potentially carcinogenic.

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Melted Bitumen
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Bitumen Preparation
Crude oil
Fractional Distillation
Kerosene (parafin)
Lubricating oil
Base Bitumen
Diesel oil
Petroleum
Light oil
Blending
Penetration Grade Bitumen
Fluxing
Emulsification in water
Oxidation
Cut-back bitumen
Bitumen Emulsion
Blown Bitumen
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Tar Preparation
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PART 8 BITUMINOUS MATERIALS

• 8.1 Introduction
• 8.2 Binders
• Properties
• Testing
• Binder Mixtures
• 8.3 Bituminous mixtures
• 8.4 Applications

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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.

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 Durability .Bitumens are

• Intrinsically durable, they oxidise, polymerise
  and lose light oil components when exposed to air
  and heat but all of these processes just make
  then harder
• Virtually impermeable if well compacted
• Intrinsically resistant to plant growth
• Softened by high temperature and solvents (often
  by fuel spills)

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Cracking of thin surface
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TESTING Binders

• Sliding plate viscometer In this apparatus a
  thin film of binder is sheared between two glass
  plates and the shearing force is measured. 
• Standard tar viscometer In this test the time
  taken for a set volume of tar to flow through an
  opening at a given temperature is measured.
• Penetration test For straight bitumens viscosity
  is normally measured with a penetration test. A
  1mm diameter needle is loaded with a weight of
  100g and the distance it drops into a bitumen
  sample in 5 seconds is measured (at 25oC). A
  bitumen is referred to as 70 pen if the
  penetration is 7mm.
•  Softening point test To measure the softening
  point a small sample is melted, cast in brass
  ring and cooled and then progressively re-heated
  until it deforms (i.e. "flows") by a given amount.

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BINDER MIXTURES

• Cutbacks This term is used to describe a mixture
  of a binder and a light volatile oil. They are
  liquid at low temperatures until the volatile oil
  evaporates.. Due to the release of solvents into
  the atmosphere they are now rarely used.
• Emulsions When mixed with water binders will
  generally settle out. An emulsifier must be added
  to give a stable solution. Bitumen paints are
  made this way. The water evaporates and the
  bitumen remains on the surface. The current
  types of cold rolled materials are based on
  emulsions.

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Rubberised bitumens

• The viscosity and softening point are increased
  and penetration is decreased.
• The elasticity is increased.
• The sensitivity to temperature changes is
  decreased.
• The beneficial properties are lost with prolonged
  heating. 
• The increased elasticity and penetration
  resistance makes this material ideal for
  expansion joints and repairs in roads.

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PART 8 BITUMINOUS MATERIALS

• 8.1 Introduction
• 8.2 Binders
• 8.3 Bituminous mixtures
• Components
• Properties
• Testing
• 8.4 Applications

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The four components of a typical mix are

• Coarse aggregate (retained on 2.36mm sieve)
• Fine aggregate (passing 2.36mm sieve but retained
  on 75?)
• Filler (passing 75?), may be cement.
• Binder Bitumen etc.

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Asphalt Mixing Plant
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Adding aggregate to a binder has the following
general effects

• 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

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TESTING Bituminous Mixtures

• 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).

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Marshall Test
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TESTING Bituminous Mixtures

•  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).

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PART 8 BITUMINOUS MATERIALS

• 8.1 Introduction
• 8.2 Binders
• 8.3 Bituminous mixtures
• 8.4 Applications

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Applications

• Roads
• Tanking
• Roofing

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Road construction types
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Paving machine
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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.

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Hot Rolled Asphalt Surface
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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.

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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)

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Applications

• Roads
• Tanking
• Roofing

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Tanking a basement(modern systems use sheet
materials)
Asphalt trowelled onto walls after casting
Base slab cast on layer of mastic asphalt
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Applications

• Roads
• Tanking
• Roofing