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Asphalt Guidelines Per The NSSGA
The National Stone, Sand and Gravel Association designed the NSSGA INSTA-GUIDES to provide the industry salespeople with a simple, basic and instant overview of sales issues within the industry. The NSSGA INSTA- GUIDES will show you where to find detailed and expanded background information highlighting a particular selling topic.
Topic #5 Selling Aggregate for Use in Hot Mix Asphalt Pavements This INSTA-GUIDE will: 1. Define hot mix asphalt pavements. 2. Discuss aggregate quality. 3. Highlight liquid asphalt. 4. Discuss customer requirements. 5. Provide more detailed hot mix asphalt pavement references.
In its simplest form, the hot mix asphalt pavement is a proportioned combination of aggregate and asphalt that’s been heated in a central mixing plant. It is then transported to a project and spread and compacted on a road surface before cooling. Typically, aggregate comprises 93 – 96% of the paving mixture and the “liquid” asphalt comprises the remaining 4 – 7% (depending on the size and grading of the aggregate).
Liquid asphalt is derived from distilling crude oil and is the heavy residue remaining after other petroleum products have been removed.
Feature Advantage Benefit Size and consistency Less problems attaining compaction Lower rolling cost better quality pavement Cubicle particle shape-coarse aggregate Better stability Lower cost higher quality pavement Improved skid resistance Cubicle particle& shape-fine Aggregate Higher strength Lower cost higher quality pavement putting resistance Low moisture Less moisture to dry Lower drying costs & stripping resistance Absorption Lower absorption Less asphalt used in the mix Lower cost mix if lower absorption Specific Gravity Lower specific gravity, more volume per ton More cubic foot of hot mix per ton
The hot mix asphalt pavement buyers usually know just what they want. So, here are a few things you should know: A. Products must be consistent from load to load. Gradation changes can often be accommodated if they’re acknowledged before the asphalt mix is produced. B. Low moisture is desirable to reduce drying costs. C. Excessive dust (-200 sieve) can be a problem in an asphalt mix. If the surface of the coarse aggregate is coated, it will interfere with the bond between asphalt and the coarse aggregate. D. Absorption of the aggregate will affect the hot mix asphalt producer’s cost. A higher absorption will require more asphalt liquid. E. Specific gravity of the aggregate will give different results. A lower specific gravity will result in a higher volume of final mix. This would be a lower cost mix to the customer due to larger area surfaced per ton.
Numerous articles have been published on this subject. A. NSSGA’s Aggregate Handbook B. NSSGA’s Aggregate Library C. Publications From i. NSSGA ii. International Center for Aggregates Research iii. National Asphalt Pavement Association iv. National Center for Asphalt Technology v. Asphalt Institute
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1. The Hot Mix Asphalt Pavement
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