Asphalt Materials

Asphalt - Definition: “A dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are obtained in petroleum processing.” (ASTM D8 - 02 Standard Terminology Relating to Materials for Roads and Pavements )

Asphalt Types Natural asphalt deposits Natural evaporation of volatile portions of petroleum leaving the asphalt fractions Lake asphalt Trinidad Bermudez Rock asphalt Natural asphalt deposits in porous rock

Asphalt Types Petroleum asphalt Produced through the process of distillation of crude petroleum Accomplished by raising the temperature of the crude in stages Different fractions separate at various temperatures Lighter fractions - Simple distillation Heavy distillates - Vacuum distillation, solvent extraction

T E M P R A U (F) PERCENT DISTILLED 1000 900 800 700 600 500 400 300 200 100 10 20 30 40 50 60 70 80 90 ASPHALT GAS OIL T E M P R A U (F) DIESEL KEROSENE GASOLINE GAS PERCENT DISTILLED

Asphalt Types Refining produces asphalt with specific characteristics for varied uses Paving asphalt Roofing asphalt Other special uses

Asphalt Types Paving asphalt Asphalt cement Cutback asphalt Emulsified asphalt

Cutback Asphalt Precautions Application temperatures are often higher than flash point! Do not load hot AC into tanks which contain cutback asphalt

Emulsified and Cutback Products Slow Curing (SC) Cutbacks Road Oils Rapid Curing (RC) Cutbacks Medium Curing (MC) Cutbacks Asphalt Emulsions WATER AND EMULSIFIER GASOLINE OR NAPHTHA SLOWLY & NON- VOLATILE OILS KEROSENE ASPHALT CEMENT ASPHALT CEMENT ASPHALT CEMENT ASPHALT CEMENT Emulsified and Cutback Products

Asphalt Emulsions A suspension of small globules of one liquid in a second liquid with which the first will not mix: an emulsion of oil in vinegar Major uses Surface treatments Patching Stabilization Slurry sealing Recycling

Asphalt Emulsions Factors which increased usage Energy crisis of 1970’s Petroleum solvents not required Used without additional heating Reduced atmospheric pollution Ability to coat damp aggregates Variety of emulsion types Economical - less fuel consumption

Asphalt Emulsions Emulsion technology Using mechanical and/or chemical processes to combine two or more materials that would not mix under normal conditions Emulsions used today were developed in 1920’s Mayonnaise, paints, hair dyes, ice cream

Asphalt Emulsions Anionic Grades Cationic Grades RS - Rapid Setting MS - Medium Setting SS - Slow Setting Mixing ability RS grades do not mix well with aggregates MS grades mix well with coarse but not fine aggregates SS grades mix well with fine aggregates Cationic Grades CRS - Rapid Setting CMS - Medium Setting CSS - Slow Setting Asphalt Institute Basic Asphalt Emulsion Manual MS-19

Asphalt Emulsions Composition Asphalt cement Water Emulsifying agent May contain a stabilizer

Asphalt Emulsions Breaking - Separation of the water and asphalt globules Asphalt Globules Water and Emulsifying Agent

Typical Emulsion Nomenclature CRS-2P CLASSIFICATION PREFIX MODIFICATION SUFFIX SUB-CLASSIFICATION VISCOSITY SUFFIX

Asphalt Emulsions Emulsion must be stable Asphalt particles remain in suspension Pumping Prolonged storage Mixing Emulsion should break easily Contact with aggregate in mixer Sprayed on road surface After cure, asphalt retains original properties

Asphalt Emulsions Classification Anionic Negatively charged asphalt particles Cationic Positively charged asphalt particles Dependent on type of emulsifying agent used

Asphalt Emulsions Factors affecting breaking and curing Absorption rate of aggregates Aggregate moisture content Aggregate gradation - surface area Weather conditions - temp, humidity, wind Type and amount of emulsifying agent Intensity of aggregate charge Mechanical manipulation and rolling

Asphalt Emulsions Storage and handling Store between 10° and 85° C (50° and 185° F) Use tall, vertical tanks for storage Do not used forced air to agitate Do not mix anionic and cationic grades Do not dilute RS grades with water MS and SS grades can be diluted Add water to emulsion slowly Do not add emulsion to tank of water Do not add hot asphalt cement to emulsion tank

ASPHALT PLANT

Asphalt Plants Stationary plants At a permanent location Often times materials are hauled to the plant from other sources Portable plants Moved from location to location Take advantage of aggregate sources close to the job site

Asphalt Plants Items common to both plant types Site location Aggregate storage and cold feed system Aggregate drying and heating Dust collection system Asphalt storage tank(s) Plant control facility

Cationic emulsions are preferred for acidic aggregates and anionic emulsions for basic aggregates