LESSON 8

• BITUMINOUS MATERIALS

  
• Pools of Natural Asphalt still exist just like the

  Pitch Lake of the Trinidad Island in L.A, California.
• Rock Asphalts - are asphalt impregnated in porous rocks.
• ASPHALT


  Dark Brown to Black cementitious material.

  Solid to semi-solid in consistency.

  Occurs in nature.

  Soluble in most petroleum products.
• TAR


  Brown or Black bituminous material.

  Liquid or semi-solid in consistency.

  Obtain as condensates in the destructive distillation of coal, petroleum, wood, and other organic materials.

  Resistant to petroleum-based solvents.

  Lower content in bitumen.
• To eliminate the need to heat the asphalt to a liquid state before it can be used in construction, the cement can be modified into:

  Cutback Asphalt

  Emulsified Asphalt
• Asphalt Cutbacks


  are produced by cutting the asphalt cement with a petroleum solvent. These are classified according to the relative speed of evaporation of the solvent.
• ASPHALT CUTBACKS - These are classified according to the relative speed of evaporation of the solvent:

  Rapid-Curing (RC)

  Medium-Curing (MC)

  Slow-Curing (SC)
• Rapid-Curing (RC)


  asphalt cement and a volatile solvent in the gasoline or naphtha boiling point range.
• Medium-Curing (MC)


  asphalt cement and a solvent in the kerosene boiling point range.
• Slow-Curing (SC)


  asphalt cement and an oily solvent which has low volatility.
• Asphalt Emulsions


  are produced by separating the hot asphalt cement into minute globules and dispersing them in water that has been treated with emulsifying agent.
• Anionic (negative charge) - works best with positive charge aggregates such as limestone and dolomite.
• Cationic (positive charge) - works best with siliceous and wet aggregates.
• ASPHALT EMULSIONS - ANIONIC

  Rapid Setting (RS)

  Medium Setting (MS)

  Slow Setting (SS)
• ASPHALT EMULSIONS (CATIONIC)

  Rapid Setting (CRS)

  Medium Setting (CMS)

  Slow Setting (CSS)
• ASPHALT PAVEMENTS


  general term referring to any pavement that has a surface constructed with asphalt. Normally, it consists of a surface course (layer) of mineral aggregate coated and cemented with asphalt and one or more supporting courses.
• Types of supporting courses in Asphalt Pavements:

  Asphalt base (asphalt-aggregate mixture)

  Crushed stone (rock), slag, or gravel

  Portland Cement Concrete

  Old brick or stone block pavements
• Asphalt Wearing Surface


  The upper or top layer of asphalt pavement. It may range from less than 1 inch to several inches in thickness, depending on a variety of design factors.
• 1-inch thickness of asphalt base = 2 to 3-inch thickness of untreated granular base
• Full-depth asphalt pavement - when the entire pavement above the subgrade consists of asphalt mixtures. This is generally considered as the most modern and dependable type of pavement for present-day traffic.
• Preparation of Asphalt Concrete:

  Plant Mix

  Mixed-In-Place (Road Mix)
• Plant Mix


  Asphalt paving mixtures prepared in a central mixing plant. Mostly done for high strength design requirement.
• Mixed-In-Place (Road Mix)


  Mixture is done on-site by rotary mixer or traveling mixing plant under moderate to warm weather temperatures. Emulsified asphalt and cutback asphalt are used in this method of preparation.
• Recycled Asphalt Concrete


  Combined reclaimed pavement materials and new materials to produce asphalt mixture that meet normal specification requirements. Old pavements are crush into desired sizes and added as part of the concrete mix.
• Slurry Seal


  Thin asphalt overlay applied by a continuous process machine to worn pavements to seal them and provide a new wearing surface using emulsified asphalt. Uniformly graded aggregate from a particle size about the thickness of the finished overlay down to No. 200.
• Asphalt Surface Treatment - a sprayed-on application of asphalt to a surface, with or without a thin layer of covering aggregates.
• Seal Coats - surface treatments that have waterproofing or texture improvement, or both as their main purpose.
• Tack Coat - is a sprayed thin coating of asphalt to bind the existing and the new pavement.
• Prime Coat - is sprayed on a granular base so that it will seep into or penetrate the base and serves as a binder for the pavement to be constructed.
• Asphalt Spray Application

  Surface Treatment

  Seal Coat

  Tack Coat

  Prime Coat
• Asphalt Penetration Macadam


  consists of one or more layers of large-sized broken stone and rock chips interlocked by rolling. Fluid asphalt is sprayed onto each layer, and it seeps into or penetrated the layer to bind the stoned together.
• Rolling should start as soon as possible after the material has been spread.
• 3 consecutive phases of Rolling:

  Breakdown/Initial Rolling

  Intermediate Rolling

  Finish Rolling
• Breakdown/Initial Rolling


  compacts the material beyond that imparted by the paver to obtain all of the density it needs.
• Intermediate Rolling


  densifies and seals the surface.
• Finish Rolling


  removes roller marks and other blemishes left from previous rolling.
• DEFICIENCIES ON ASPHALT MIX

  Too hot

  Too cold

  Too much asphalt

  Too little asphalt

  Non-uniform mix

  Excess coarse aggregate

  Excess fine aggregate

  Excess moisture

  Miscellaneous