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Types & Uses of Asphalt Materials

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1 Types & Uses of Asphalt Materials
HMA Surface Asphalt Binder Types and Uses

2 + HMA (Hot Mix Asphalt) Asphalt Binder Types and Uses
Hot Mix Asphalt (HMA) is made up of graded aggregates and asphalt binder. They are generally mixed in a hot mix plant (either batch type or continuous mix type) to meet the specifications of the using agency for the end-result whether it be for a parking lot, an airfield runway or an interstate highway. Asphalt Binder Types and Uses

3 Bituminous Materials Asphalt Tar Asphalt Cement Cutback Emulsion
(from coal) (from petroleum crude) Asphalt binders and tar are both considered bitumen materials. Quite often these two terms are used interchangeable due to misconceptions resulting from their similarity in appearance and in the parallel applications. However, asphalt binders and tar are two distinctly different materials with different origins and different physical and chemical characteristics. Asphalt binders is a dark brown to black cementitious material that is either naturally occurring or is produced by petroleum distillation. Tar, on the other hand, is primarily manufactured from the destructive distillation of coal and has a very distinctive odor. An asphalt binders at room temperature is a solid. To be able to mix it with an aggregate it must be made into a liquid. This can be done by heating the asphalt binders , adding a petroleum solvent to it to make it a cutback asphalt or by adding water to it to make it an emulsion. Each of these will be discussed in further detail in this module and in the course. Asphalt Cement Cutback Emulsion Asphalt Binder Types and Uses

4 Trinidad Lake Asphalt Asphalt Binder Types and Uses
Probably most people who deal with asphalt know that in the 19th century the major source of asphalt for contractors in the United States was the island of Trinidad in the Caribbean some 2,000 miles south of New York City. There, in the stunted throat of an extinct volcano, a lake of asphalt, bitumen combined with clay, covers about 114 acres. The surface of this unusual lake is strong enough to walk on, permitting workmen with mattock and shovel to dig out chunks, but any heavy object left on the surface will sink out of sight in 48 hours. The remarkable feature of this seemingly bottomless pit of hydrocarbons is that it bubbles up from below to fill in the excavations made by workmen removing chunks from the surface. By 1900, Trinidad was exporting thousands of tons of raw asphalt to the United States where this remarkable material was fast becoming the favored material for paving city streets. But there were many false starts, and it was literally centuries before asphalt caught on. The Bible tells us that Noah used bitumen to caulk the Ark. And sometime before 562 B.C. Nebuchadnezzar, the Babylonian king, used it to pave a short section of a ceremonial roadway. Christopher Columbus, on one of his voyages to the New World in the 1490s, was shown the pitch lake of Trinidad by friendly Carib Indians. But Columbus had his mind set on finding gold, so he gave little thought to the potential of the asphalt lake. A hundred years later another explorer from the Old World, Sir Walter Raleigh, reached Trinidad. When the natives showed him the pitch lake, he promptly recognized the value of the bitumen for caulking his ships. He even went so far as to say the substance was superior to the traditional Norway pine pitch for caulking because it didn''t melt in the sunlight. Neither the observations of Columbus nor those of Sir Walter Raleigh led to any significant interest in Trinidad Asphalt. Not until nearly 150 years after Sir Walter’s voyage did a visitor recognize the commercial potential of Trinidad asphalt. In 1849, Admiral Thomas Cochrane, the Earl of Dundonald, who commanded the Royal Navy’s West Indian squadron, visited the pitch lake and immediately grasped its significance. Admiral Cochrane was an authentic naval hero and a most unusual individual. He was a man with a lively imagination and boundless energy both of which attributes he displayed by the number of inventions credited to his name. One of his earliest inventions was a new kind of street lamp which at least one community actually adopted. Most of his inventions had a nautical application. These included an improved and more efficient steam boiler, a rotary steam engine which offered greater efficiency than the conventional reciprocating piston engine, and a ship’s propeller with blades set at an angle to counteract the centrifugal forces of the screw. His rotary steam engine was developed enough to be subjected to a trial in a Royal Navy vessel. Another of his inventions, a method of using air pressure to tunnel under rivers, was subsequently widely adopted by engineers in England and the United States. At the time the Admiral visited the Trinidad pitch lake, no effort was being made to mine the asphalt for industrial use. Given Cochrane’s lively imagination and inventive turn of mind, he was quick to sense the commercial and military possibilities the great bitumen deposit offered. Access to the bitumen as a source of fuel for steam powered vessels would give the Royal Navy in American waters a marked advantage over potential enemies relying on European coal sources to power their warships. So, he set his sailors to work hacking out quantities of asphalt from the lake and hauling them to the shore. The admiral’s flagship, HMS Wellesley, named after Lord Wellington, the hero of Waterloo, was an old line-of-battle sailing ship, but his squadron included a steam vessel, HMS Scourge. He ordered the crew of this steam warship to take on board twice the amount of asphalt as she had coal. On the voyage home, he conducted an experiment, using the bitumen as fuel. When the winds faltered and becalmed his flagship, the admiral had Scourge tow the Wellesley until suitable winds returned. Quite apart from any benefit Trinidad pitch might confer as fuel for the Royal Navy, the admiral envisioned countless commercial applications. Soon after reaching England he filed various patents covering the use of asphalt in numerous applications such as insulation for wiring, sealing water conduit joints and many other waterproofing uses. But his great hope was that asphalt could be used to pave streets in London and other British cities. To demonstrate his notion of asphalt paving, he arranged to have a section of a street in London paved with the material he had brought from Trinidad. Unfortunately, the experiment ended in failure. The workmen who laid down the pavement had no understanding of this novel material and the resulting surface was so slippery that horses continually fell and injured themselves. The ensuing complaints, not to mention the threat of lawsuits, so discouraged the admiral that he ordered his crew to jettison the Scourge’s remaining cargo of asphalt at sea. The record doesn’t reveal, but presumably the conservative bureaucrats at the admiralty also showed no interest in bitumen as a source of fuel. However, not everyone was blind to the advantages Cochrane envisioned. Within a dozen years, other men, notably in France, experimenting with this remarkable new material found ways to process it successfully, starting it on its long career as the world’s best paving material. (Reprinted with permission of National Asphalt Pavement Association from their HMAT magazine, January/February 2005.) Display On: 2/8/2005 Asphalt Binder Types and Uses

5 Asphalt Binder is Generally Produced in a Refinery
This is a photo of a typical refinery. Asphalt Binder Types and Uses

6 Source of Asphalt Cement
Oil Well (Gasoline) LIGHT DISTILLATE (Kerosene) PUMPING STATION MEDIUM DISTILLATE FIELD STORAGE (Diesel Oil) HEAVY DISTILLATE TOWER DISTILLATION REFINERY RESIDUUM The first step in the processing of all crude petroleum is the straight reduction by distillation. The distillation principle is based on the concept that various crude fractions which have different boiling ranges. Because asphalt binders is made up of the highest boiling fractions, it becomes the residuum from the refinery tower. The crude oil is introduced into a distillation tower where the lightest components vaporize, rise to the top, cool, condense, and are drawn off for further processing. The bottom fraction from this unit is called vacuum processed, steam refined asphalt binders . The grade of asphalt binders is controlled by the amount of heavy gas oil removed. PROCESS UNIT OR STORAGE TUBE HEATER CONDENSERS AND COOLERS ASPHALT CEMENTS GAS AIR BLOWN ASPHALT PETROLEUM FOR PROCESSING INTO EMULSIFIED AND CUTBACK ASPHALTS SAND AND WATER AIR STILL

7 General Asphalt Binder Properties
Adheres well to most rock Waterproof Fairly durable Resistant to reaction with most acids, alkalis, and salts Temperature sensitive Asphalt Binder Types and Uses

8 Asphalt Components Asphaltenes Resins Oils
Asphalt binder is broken down into 3 components: Asphaltenes Dark brown friable solids Control viscosity and adhesive properties Resins Dark solid or semi-solid Greatly affected by temp. Disperse the asphaltenes Oils Colorless or white liquids Oxidize and harden into asphaltenes and resin molecules * These three components are Blended to produce asphalt binder of desired properties In the Rose process, the residuum is mixed with a low-boiling hydrocarbon solvent (such as, normal pentane) under supercritical conditions. The mixture is then fed into a separator to separate the components in an asphalt. These materials can then be blended to provide speciation grade asphalt binders. Asphalt Binder Types and Uses

9 Asphalt Types Used in Pavement
Asphalt cement (asphalt binder) Used for HMA, patching Asphalt emulsion (residue + water + emulsifying agent) Used for cold mix & maintenance applications Asphalt cutback (residue + solvent) Asphalt Cement = binder (like PC is to PCC) Cement is unmodified asphalt Binder is be modified with other ingredients (polymers, rubber) Binder alone is also used for sealing and waterproofing Asphalt Emulsion (30-40%residue % water + fraction of a % of emulsifying agent) Used for cold mix maintenance, patching, chip seals, slurry seals, crack sealing, base and sub-base stabilization, and surfacing low volume roads Asphalt Cutback (residue + solvent) Hazardous, volatile solvents and hydrocarbons are released Same as emulsion but phased out because of environmental reasons and cost Asphalt Binder Types and Uses

10 Hot Mix Asphalt (HMA) Asphalt concrete Bituminous concrete
HMA = Asphalt concrete = binder + aggregate Used mainly for hot mix pavement surfacing Asphalt concrete Asphalt paving mix Asphalt mix Asphalt Bituminous concrete Bituminous paving mix Bituminous mix Asphalt binders plus aggregates will produce hot mix asphalt. Over the years, a number of terms have been used to describe the material. This slide shows the many names you will find either in state and federal specifications or the technical literature. The AASHTO Subcommittee on Materials is establishing HMA as the industry standard. Asphalt Binder Types and Uses

11 Asphalt Binder Types and Uses
Asphalt binders are generally used to produce hot mix asphalt Asphalt Binder Types and Uses

12 Asphalt Binder Types and Uses
It is used by both civil and military aviation to construct airfield pavements. The specifications for these facilities are usually written by the FAA or the military service that owns the airfield. Asphalt Binder Types and Uses

13 Asphalt Binder Types and Uses
A major use of HMA is for parking lots for residential buildings as shown in this photo or for industrial facilities. In some areas this represents 30 to 40 % of the market for hot mix asphalt (HMA). Asphalt Binder Types and Uses

14 Asphalt Binder Types and Uses
Most of the automobile race tracks use HMA for the surface. The construction of these tracks presents some unique construction problems. This slide shows the problem associated with trying to pave on the steep slope associated with the curve on one of those tracks. Asphalt Binder Types and Uses

15 Cutback Asphalts Rapid Curing (RC) Asphalt + Naphtha Surface Treatment
Medium Curing (MC) Asphalt + Kerosene Stockpile Patch Prime Coat MC - 30 MC - 70 MC - 250 MC - 800 Slow Curing (SC) Asphalt + Oil SC - 70 SC - 250 SC - 800 SC To be able to use an asphalt binder, it must be made into a liquid. One of the ways to do that is to dissolve it in a light petroleum to make different grades of material. The different curing rates, rapid, medium, slow are the result of using different solvents. These materials are used less now than they were 20 to 30 years ago because of environmental concerns. The asphalt binder hardens around the rock by the evaporation of the distillate. This distillate puts hydrocarbons into the air stream which add to the air pollution problem. In many urban areas they have been totally outlawed. 30 is more fluid than 3000 Asphalt Binder Types and Uses

16 CUTBACKS - USES Rapid Curing Tack coats Surface treatments
Medium curing Prime coats Stockpile patching materials Road Mixing Operations Slow curing Prime Coats Stockpiling Road mixing This slide outlines the different uses for cutback asphalts. Asphalt Binder Types and Uses

17 EMULSIONS - USES Slow Setting (SS) Medium Setting (MS) Rapid Setting
Tack coats, fog seals, dense-graded cold mixes Medium Setting (MS) Open graded cold asphalt-aggregate mixtures Rapid Setting Surface treatments The third way asphalt binders are made into a liquid is by emulsification with water. The heated asphalt cement is feed into a colloid mill with water and an emulsifying agent (generally a soap-like material). It is then feed into storage tanks. The resultant product is similar to the cutback asphalts but without the distillate and the resulting air pollution problems. As with cutback asphalts there are different grades of asphalt emulsions. The different grades are determined by the different emulsifiers used. Asphalt Binder Types and Uses

18 Asphalt Binder Types and Uses
Asphalt emulsions can be manufactured with different particle charges. Aggregates also have different surface charges that are dependent on their geological nature. The concept is that unlike charges attract and thus the bond between the asphalt binders and the aggregate will be better. Asphalt Binder Types and Uses

19 Asphalt Binder Types and Uses
Emulsions can be used as a fog seal for maintenance purposes. In this picture the asphalt emulsion is sprayed and followed immediately with a sand to improve the skid resistance. Asphalt Binder Types and Uses

20 Asphalt Binder Types and Uses
Another use for asphalt emulsions is in the construction of a aggregate surface treatment where about 0.25 gypsy of asphalt emulsion is spray applied to the surface and (continued next slide) Asphalt Binder Types and Uses

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