What is Hot Mixed Asphalt?

Road roller at a road construction site

Hot mixed asphalt, also known as HMA, is a mixture of asphalt cement, aggregate (mineral filler), and water. It is used to pave roads and parking lots because it hardens quickly and provides good traction when it’s hot.

There are two designs of Hot Mixed Asphalt depending on size:

● Standard HMA

The Standard HMA has a maximum size of 3/8 inch (9 mm), with a water-to-cementitious material (w/c) ratio of around 0.50 to 0.60. It’s effective for most residential streets, driveways, etc.

● Superpave HMA

Superpave mixes have a maximum size of 1/4 inch (6 mm). They are designed with a specific blend ratio for each specification (i.e., AASHTO M 247). Unlike standard HMAs, Superpave Mixes are more resistant to rutting, cracking, and fatigue, making them ideal for heavy traffic areas.

Types of Hot Mix Asphalt

The Standard and Superpave HMAs come in three types depending on granular density:

Stone Matrix Asphalt (SMA)

SMA is a mix of stone and asphalt binder. It has a relatively high asphalt content and low stone content. These mixes are effective for jobs in construction where the traffic load is high and the pavement life expectancy. SMA can also support rockfall protection systems, such as bridge abutments or retaining walls.

Open Graded Mixes (OGM)

These mixtures comprise low proportions of stones and higher binder proportions than the Stone Matrix Asphalt (SMA). The amount of rock in an open-graded mix varies from 15% to 25%. OGMs apply for new construction and rehabilitation projects where traffic loads are low and pavement life expectancy is high (over 20 years).

Dense Grade Asphalt

Dense grade asphalt is the most common asphalt you’re likely to find on your local roads. This type of asphalt contains stone chips with a high silica content that helps to bind the material together. Dense Grade Asphalt is made by blending various amounts of coarse stone or gravel with liquid asphalt. The stone provides strength through its weight, while the bitumen lends durability to the mixture.

How Hot Mix Asphalt is Used

The first step in applying Hot Mix Asphalt is to prepare the surface. This ensures that the pavement will adhere adequately, making it last longer. The surface must be free of dirt, oil, grease, and any existing coatings, such as sealers, waxes, or other materials.

Once the surface is spotless:

● Pour a layer of aggregate (rocks) into pre-formed bedding.

● Fill the aggregate with sand to create a layer for the asphalt to sit on top of and provide additional drainage capabilities for water coming through your driveway or parking lot.

● Apply a layer of Hot Mix Asphalt onto the aggregate and sand mixture using a hot asphalt paver machine (which looks like an oversized steam roller). This layer should be between 1/8 inch thick to 1/4 inch thick, depending on how much traffic you expect on your driveway or parking lot.

With these steps followed, the engineer will leave the road or pavement for three to seven days before it can be open for use. Check our website on how to use the HMA depending on the type of jobs in construction you need Kilgore to do for you.

How Hot Mixed Asphalt Makes a Difference to Your Paving Project

If you’re planning to upgrade your road or pavement, HMA is worth considering. These mixes have many advantages over conventional pavements for:

Consistent density

Hot mix asphalt produces a more consistent density than cold mix asphalt. This allows for uniform compaction and provides better long-term performance.

Better rut resistance

Hot mix asphalt has better rut resistance than cold mix because it is denser. It doesn’t allow water to penetrate the pavement’s surface, minimizing potholes from forming on various jobs in construction.

Longer life expectancy

Hot mix asphalt lasts longer than cold mix because it has better rut resistance. HMAs also have better compaction properties, which means fewer voids remain after compaction occurs.

Need Quality Hot Mix? Get it from Kilgore!

Kilgore Hot Mix is a leading provider of mixes and materials for commercial, residential, and industrial projects. For over 100 years, we have provided quality hot mix asphalt to customers across Texas.

Our team will help you determine which mix type is best for your specific needs, from residential driveways to large-scale commercial projects. We also work with a team of professional engineers with the right expertise for HMA applications. Contact us today or browse our website to get the full view of services on our list.