What Is Hot Mix Asphalt?
Historically hot mix asphalt has been a combination of two major components: liquid asphalt binder and aggregates. The asphalt binder coats the various aggregates in the mix and acts as the adhesive which holds the asphalt mix together. The aggregates in the mix help to provide the structure in the asphalt mixture which gives it stability and strength. Today due to the development of warm mix asphalt (WMA) the term hot mix asphalt is being replaced by the simple term asphalt. Today asphalt can be a combination of not only liquid asphalt binder (now known as just simply asphalt binder) and aggregates, but asphalt can include recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), rubber from used tires and glass.
How Is Asphalt Made?
Asphalt is produced by combining heated asphalt binder and aggregate. For hot mix asphalt the mixing is generally performed with the aggregate at temperatures between 300 °F and 350 °F. Delivery, placement and compaction must be performed while the asphalt is sufficiently hot. Minimum placement temperatures for hot mix asphalt can range between 260-290 °F. Due to these requirements it is not uncommon to have paving seasons which correspond to the hot or warm months of the spring, summer and fall in order to place the asphalt mixture before becomes too cool. Due to the development of warm mix asphalt (WMA) paving seasons are being extended to cooler and even colder months.
What Is The Most Common Pavement Type In The United States?
94% of our nations paved roads of are surfaced with asphalt. About 85 percent of the parking lots in the U.S. are asphalt. Busy commercial airports such as Baltimore-Washington International, Oakland International, San Francisco International, McCarran (Las Vegas), Pearson International (Toronto), and Logan International (Boston) have main runways surfaced with asphalt. Asphalt is also used on 85 percent of the runways at general aviation airports. Of the 33 NASCAR race tracks across the country, 31 are paved with asphalt. Of the 88 race tracks listed for the NASCAR Short Track series, 64 are asphalt, 21 are dirt or clay, and only three are concrete. Asphalt tends to be the pavement of choice by most designers and specifiers because of its lower construction cost, reduced time of construction, ease of maintenance, and benefits related to improved smoothness, reduced pavement noise, and ability to resist deformation in colder climates and higher elevations.