Asphalt is a composite material that forms the surface layer of most modern roads, driveways, and parking lots. It is a mixture of mineral aggregates, such as crushed stone, sand, and gravel, bound together by bitumen. Bitumen is a dark, sticky, petroleum-derived substance that acts as the adhesive. This engineered mixture, known as asphalt concrete, provides a durable, flexible, and weather-resistant paving solution that is standard for infrastructure globally.
Ancient Uses of Bitumen
The use of the binder material, bitumen, predates modern road construction by thousands of years, primarily relying on naturally occurring deposits. Early civilizations used this natural asphalt for its adhesive and waterproofing properties rather than for engineered road surfaces. The Sumerians in ancient Mesopotamia, dating back to the third millennium BC, utilized natural bitumen as mortar to bind bricks and stones in construction projects.
This substance was also employed for ship caulking and waterproofing temple baths and storage pits. One notable early application was in Babylon around 625 BC, where the Procession Street was paved with burnt bricks set in a mortar of natural asphalt. While these applications demonstrated early use of the material in construction and paving, they did not involve the scientific mixing of bitumen and aggregates to create a modern, load-bearing road surface.
The First Engineered Asphalt Road
The development of the first modern, engineered asphalt road surface occurred in the 19th century, marking a significant transition to a scientifically formulated paving material. The achievement is attributed to Belgian-American chemist Edward de Smedt, who developed a new type of asphalt mixture in 1870 while working at Columbia University. This process involved creating “sheet asphalt” by combining sand and a bituminous binder in a precise, heated ratio.
De Smedt’s patented material was an attempt to create a smoother, more durable surface than the existing macadam or cobblestone roads. The first application of this new sheet asphalt pavement was laid on William Street in Newark, New Jersey, on July 29, 1870. This initial experimental section used a natural bitumen sourced from West Virginia. A more successful and enduring application followed in 1876 when de Smedt engineered a new mix using bitumen from the natural Pitch Lake in Trinidad. This improved mixture was used to pave a portion of Pennsylvania Avenue in Washington, D.C., establishing the first large-scale installation of modern asphalt paving in the United States.
Standardization and Mass Adoption
Following the successful trial in Washington, D.C., the engineered asphalt mixture quickly moved toward standardization and widespread use. De Smedt’s sheet asphalt replaced the initial use of natural rock asphalt, allowing engineers to tailor the pavement’s performance characteristics by adjusting the ratio of aggregates and the bituminous binder.
The need for better roads grew exponentially with the rise of the automobile, pushing the industry to improve production methods. In 1901, the Warren brothers established the first modern asphalt facility in Cambridge, Massachusetts, enabling the mass production of consistent asphalt mixes. Earlier road improvements, like the Tarmacadam process, which involved coating crushed stone with coal tar, paved the way for the later development of Hot-Mix Asphalt (HMA). HMA involves heating the aggregates and bitumen to high temperatures before mixing, which lowers the binder’s viscosity and allows for better coating and compaction. This production method became the industry standard, facilitating the rapid construction of highways and urban roads throughout the 20th century.