Why Roads Fail Faster Today: The Science of Bitumen, Maltenes, and MRT

Roads built today contain up to 50% less maltene content than older pavements, explaining faster cracks, potholes, and higher repair costs. About 70% of global bitumen is used in road construction, but modern refining removes vital maltenes—making pavements weaker from the start.

Have you ever noticed that roads seem to crack, rut, or develop potholes much sooner than they used to? Decades ago, highways and city streets often stayed in good condition for many years. Today, however, new pavements can start showing damage after just a few seasons.

Most people think this is only because of heavier traffic, bigger trucks, or harsher weather. While those factors play a role, the real reason is hidden much deeper—it’s in the chemistry of asphalt itself. Modern asphalt is not the same as the asphalt used in the past.

Thanks to changes in oil refining, the binding material in asphalt—the part that holds rocks and gravel together—no longer contains the same balance of compounds. This means roads are starting off weaker than they once were, even before the first car drives over them.

What Is Asphalt?

Asphalt is the material you see on most roads, highways, airport runways, and parking lots. It looks like a black, solid surface, but it is actually a carefully engineered mixture. At its core, asphalt is made of two main parts:

• Aggregates – These are crushed stones, sand, and gravel. They make up about 90–95% of the mixture and provide the strength and stability.

• Binder (Bitumen) – This is the black, sticky substance that holds the aggregates together. Bitumen is a product derived from crude oil, and it acts like glue, giving the road surface its flexibility and waterproofing.

When aggregates and bitumen are mixed together, they form asphalt concrete, which is strong enough to handle heavy traffic but flexible enough to resist cracking—at least when its chemistry is balanced.

It’s also worth noting that the word “asphalt” can be confusing:

• In American English, asphalt usually refers to the finished road material (stone + binder).

• In many other parts of the world, “asphalt” refers only to the black binder, which is more often called bitumen.

In short, asphalt is not just “rock and tar.” It is a designed system where chemistry and materials science work together to create the roads we drive on every day.

What is bitumen, and where is it commonly used?

Bitumen is a very thick, sticky part of petroleum that can look like a black liquid or a solid that flows very slowly over time. In American English, it is usually called asphalt.

There are two main types of bitumen:

• Natural bitumen – Found in the ground, often in large deposits. A famous example is Pitch Lake in Trinidad, which holds around 10 million tons. The word pitch is another name for natural bitumen. It refers to its very thick, tar-like appearance.

  • Famous sites like Pitch Lake in Trinidad or the La Brea Tar Pits in California are actually filled with natural bitumen (often called tar by mistake).

  • Pitch has been used since ancient times for sealing boats, waterproofing, and even as a building material. 

• Natural bitumen is also found in huge oil sand deposits, where sand and clay are mixed with bitumen.

  • The largest oil sands reserves are in Alberta, Canada, in an area called the Athabasca oil sands. These cover about 142,000 square kilometers—bigger than England—and are among the world’s largest sources of natural bitumen.

• Artificial (refined) bitumen – Produced during the petroleum refining process. When crude oil is heated and distilled at very high temperatures (around 525 °C or 977 °F), lighter products like gasoline and diesel are removed, leaving behind a heavy residue. This residue is further processed and used as bitumen.

Bitumen’s most common use is in road construction, where it binds gravel and stones together to form asphalt concrete. About 70% of the world’s bitumen production goes into roads. It is also widely used for waterproofing products such as roofing felt and sealants.

What is the chemical composition of Bitumen ?

Bitumen is made up of four main groups of chemicals:

• Naphthene aromatics – ring-shaped compounds that are partly hydrogenated (hydrogen atoms are added to the molecule to make it more stable).

• Polar aromatics – heavy molecules like phenols (a type of acidic compound found in oils) and acids (substances that can react with bases), formed when bitumen partly oxidizes (reacts with oxygen).

• Saturated hydrocarbons – simple compounds that are “saturated” (all bonds are filled with hydrogen atoms). These decide how soft or hard the bitumen is.

• Asphaltenes – very large, complex molecules that include phenols and heteroatomic compounds (molecules that contain elements other than carbon and hydrogen, such as nitrogen, oxygen, or sulfur).

If we look at the elements inside bitumen, it is mostly carbon (the main element in fuels, plastics, and living things, about 80%), hydrogen (a light gas element, about 10%), and sulfur (a yellow non-metal element that gives off a strong smell, up to 6%).

On a molecular level, bitumen is a mix of:

• Asphaltenes (5–25%) – these give structure and strength.

• Maltenes (65–90%) – these act like glue, keeping the bitumen soft and flexible.

Natural bitumen also contains very tiny amounts of organosulfur compounds (organic molecules that include sulfur) and trace metals such as nickel (a metal used in coins and steel) and vanadium (a metal used in alloys), usually less than 10 parts per million (a very small amount).

Bitumen dissolves in a liquid called carbon disulfide (a chemical solvent used in laboratories). Scientists describe it as a colloid (a mixture where small particles are spread throughout a liquid but don’t settle down). Here, asphaltenes are the particles and maltenes are the liquid around them.

Because bitumen has so many different molecules, it is almost impossible to separate and identify each one.

Why are maltenes important for road durability, and how do they work together with asphaltenes?

Maltenes are the “flexible” part of bitumen. They act like the glue that keeps asphalt soft and workable. Thanks to maltenes, roads can bend slightly under the weight of vehicles or expand and contract with temperature changes—without breaking apart.

When maltenes are present in the right amount, asphalt stays pliable (able to bend without cracking). This helps the pavement resist common problems such as:

• Cracks from cold weather or heavy loads.

• Potholes caused when water gets into small cracks and breaks the road surface.

• Weather damage from sunlight, heat, and rain.

But maltenes cannot do this job alone. They need to stay in balance with asphaltenes, the heavier molecules that provide strength and structure. Think of it like building with bricks and mortar:

• Asphaltenes are the bricks (they give the road its hardness and shape).

• Maltenes are the mortar (they keep everything held together and slightly flexible).

If there are too many asphaltenes and not enough maltenes, the road becomes brittle and cracks easily. If there are too many maltenes, the surface can become too soft and weak. A proper balance between the two is what gives roads both strength and durability.

How has modern refining changed asphalt, and why does this make today’s roads weaker?

Modern oil refineries are designed to be extremely efficient. They extract as many valuable products as possible from crude oil, such as gasoline, diesel, and jet fuel. While this makes fuel production more profitable, it also means that many of the maltenes that once naturally ended up in asphalt are now being removed during refining.

This has created a hidden problem for our roads. Older roads, built decades ago, had asphalt with a higher natural content of maltenes. These roads stayed flexible for longer and could resist cracking and weather damage better. That’s why they often lasted longer before major repairs were needed.

In contrast, modern roads are often built with asphalt that starts out maltene-deficient. With fewer maltenes, the asphalt is less flexible from day one. Over time, it becomes brittle, leading to faster cracking, potholes, and higher maintenance costs. In other words, our roads are structurally weaker right from the start—not because of poor construction, but because of changes in asphalt chemistry.

What  Is Maltene Replacement Technology (MRT)?

Maltene Replacement Technology (MRT) is a road-preservation method that restores the lost maltenes in asphalt binder. Instead of just softening or coating the surface, MRT works at the chemical level to bring back the flexible, oily fractions (maltenes) that give asphalt its durability.

When maltenes are put back into the asphalt:

• The binder regains its flexibility.

• The balance between asphaltenes (hard structure) and maltenes (soft glue) is restored.

• Roads resist cracking, raveling, and water damage for years longer.

• These maltenes are derived from crude oil refining, but unlike fuels (gasoline, diesel, jet fuel), they are taken from special refinery streams that preserve the heavy, oily fractions.

• MRT doesn’t use agricultural or citrus-based solvents (like soy oil or d-limonene). Those bio-based products may soften asphalt temporarily, but they don’t restore missing maltenes. In fact, they can dilute the binder and speed up aging.

• Instead, MRT relies on petroleum maltene fractions because asphalt itself is petroleum-based, so the chemistry matches naturally.

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