Changes

Hot Mix Asphalts are defined by the gradation of the aggregate. This includes the maximum size of crushed stone present in the mix. Most asphalt specifications state what mix type to use for various projects and give the range of particle size that the aggregate gradation must fall within.

Hot Mix Asphalts are defined by the gradation of the aggregate. This includes the maximum size of crushed stone present in the mix. Most asphalt specifications state what mix type to use for various projects and give the range of particle size that the aggregate gradation must fall within.

Asphalt mix types are referred to by the gradation limits. Each state, city or municipality has their own designation for asphalt mixes suitable for use in their jurisdiction. For example Florida DOT refers to S1 mixes while Texas DOT uses Type A, B C or D mixes.

Asphalt mix types are referred to by the gradation limits. Each state, city or municipality has their own designation for asphalt mixes suitable for use in their jurisdiction. For example, Florida DOT refers to S1 mixes while Texas DOT uses Type A, B C or D mixes.

To adopt a national standard for HMA all States are moving to the SuperPave method of describing asphalt mixes.

To adopt a national standard for HMA all States are moving to the SuperPave method of describing asphalt mixes.

There have been many minor changes to the types of asphalt mixes since the turn of the millennium. These changes were needed to ensure that the performance of HMA meets today's traffic counts and loads. All of these changes, described different mix criteria, aggregate types and sizes, and asphalt binder (liquid asphalt), but all these changes continued to use the outdated Marshall method of mix design.

There have been many minor changes to the types of asphalt mixes since the turn of the millennium. These changes were needed to ensure that the performance of HMA meets today's traffic counts and loads. All of these changes, described different mix criteria, aggregate types and sizes, and asphalt binder (liquid asphalt), but all these changes continued to use the outdated Marshall method of mix design.

SuperPave is a new design method was developed to adopt a national standard for HMA pavements. This standards allows our industry to measure HMA performance on a national level. Therefore a new design method was needed that better simulated the traffic loads expected; one that would perform better under those loads.

SuperPave is a new design method was developed to adopt a national standard for HMA pavements. This standards allows our industry to measure HMA performance on a national level. Therefore, a new design method was needed that better simulated the traffic loads expected; one that would perform better under those loads.

It was also decided that the asphalt binder used needed to do a better job of fitting to the climate in which the mix was to be laid. This resulted in the development of the "performance graded" (PG) asphalt binder.

It was also decided that the asphalt binder used needed to do a better job of fitting to the climate in which the mix was to be laid. This resulted in the development of the "performance graded" (PG) asphalt binder.

Even with a properly designed mix, compaction of the mat is possible only if correct mix temperature exists.

Even with a properly designed mix, compaction of the mat is possible only if correct mix temperature exists.

At temperatures between 85°C (185°F) and 150°C (300°F), the asphalt binder is fluid enough to act as a lubricant in the compaction process aiding movement of the mix aggregates into a dense configuration. As it cools below this temperature range, asphalt becomes very stiff and sticky making further mix densification extremely difficult. Therefore, compaction must be completed before the mix cools to 85°C (185°F).

At temperatures between 85 °C (185 °F) and 150 °C (300 °F), the asphalt binder is fluid enough to act as a lubricant in the compaction process aiding movement of the mix aggregates into a dense configuration. As it cools below this temperature range, asphalt becomes very stiff and sticky making further mix densification extremely difficult. Therefore, compaction must be completed before the mix cools to 85 °C (185 °F).

==Definitions==

==Definitions==

'''Compaction''' this is the process of densifying the HMA while it is in a hot, pliable state, to pack the aggregate particles together and to remove as much of the air voids as possible. Compaction gives the mix strength, resistance to rutting (the additional densification under the action of vehicular traffic), it seals the surface from the ingress of water and gives a smooth riding surface.

'''Compaction''' this is the process of densifying the HMA while it is in a hot, pliable state, to pack the aggregate particles together and to remove as much of the air voids as possible. Compaction gives the mix strength, resistance to rutting (the additional densification under the action of vehicular traffic), it seals the surface from the ingress of water and gives a smooth riding surface.

'''SuperPave''' is a method of [[design|designing]] Hot Mix Asphalt.

'''SuperPave''' is a method of [[design]]ing Hot Mix Asphalt.

 

 

==References==

==References==