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Asphalt

Asphalt Additive

The Texas Department of Transportation (TxDOT) recently approved a mineral filler for use in asphalt, in the Austin, TX District.

Dr. Md Nazmus Sakib, Assistant Professor at The University of Texas at Arlington (UTA) and Dr. Amit Bhasin, Professor, University of Texas at Austin (UT), discovered that graphite mine tailings, could improve the rutting resistance of pavement by as much as sixty percent.

Rutting resistance is measured in a laboratory by passing a heavily weighted wheel over an asphalt sample. Asphalt must endure 100,000 passes of the wheel to meet minimum standards.  The graphite tailings added at only 8 percent of the mix, achieved up to 160,000 passes.

Other TxDOT, innovations illustrate the savings that can be achieved through testing.

Asphalt Example:

  • Situation
    • In the past, TxDOT’s roadway maintenance preservation procedures involved applying a standard 2-inch thick overlay. A thin overlay is a new surface placed on the top of an existing surface in order to improve the ride and friction.
  • Solution
    • In partnership with the Texas A&M Transportation Institute, TxDOT conducted extensive research on the design and construction of thin overlays in order to identify the right mix to improve pavement performance. Specifically, a reduction of rutting and cracking. During the course of this research, TxDOT found that a 1-inch thick overlay provided equitable end-result pavement life while completing maintenance and preservation activities. Notably, this comes at a reduced cost.

By adding only 8% of tailings to the asphalt mix and significantly extending the life of the roads is a win for Texas, as a whole. Clearly, adding graphite mine tailings to the mixture for asphalt leads to a significant savings for TxDOT and thus, Texas tax payers.

To read this report in its entirety, simply Click Here to Download a copy.

Graphite Sand in Asphalt

Using graphite mine tailings like crushed limestone in asphalt mixes.

Graphite, due to its electrical conductivity and refractory properties, is widely used. Examples of its use include new energy lithium batteries, electronics, electrical industries, and in aerospace. According to the “Mineral Commodity Summaries 2024″ published by the United States Geological Survey (USGS), the global production of graphite in 2023 was approximately 1,680,000 tons. New studies to apply it to asphalt, concrete, and other building materials such as tile, roof materials like smog-reducing roof shingles, etc.

Photocatalytic surfaces are also considered self-cleaning due to their ability to degrade organic pollutants, such as adsorbed greases and oils. The ability to degrade organic compounds adsorbed on paved surfaces can prevent problems related to vehicles skidding, and thus, reduce road accidents. Photocatalysis applied to asphalt mixtures is quite innovative. There is a constant increase in the numbers of manufacturers operating in the construction industry that produce photocatalytic building materials with anti-pollution properties. We recommend it for further research. Utilizing photocatalytic asphalt pavement is an excellent method to reduce vehicle pollutants. ScienceDirect discusses this at length in the article, “A Review on Photocatalytic Asphalt Pavement Designed for Degradation of Vehicle Exhausts“.

Asphalt

The product generated by the oxidation of the pollutants by photocatalytic materials are harmless substances, and mainly salts. Photocatalysis happens through ultraviolet rays. Natural solar light (sun rays) or artificial lighting, transforms pollution such as, monoxide and nitrogen dioxide into nitrate ions and harmless eco-friendly salts. This happens through the production of active oxygen. Carbon dioxide (CO2) is also turned into harmless salts. We have gathered a collection of articles that discuss this process and method at length.

Asphalt Articles on Tailings

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