ASPHALT CONCRETE PAVING IN'S AND OUT'S
Ismaels provides commercial (roads, parking lots, etc) asphalt paving as well as private (driveways, walkways, private roads, etc) asphalt paving. We are dedicated to quality service backed up by Ismael, personally.
What is asphalt
Asphalt, also known as bitumen is a sticky black highly viscous liquid form of petroleum. In other words asphalt is oil. Asphalt is combined with sand and gravel to form a material known as asphalt concrete, that is used for road building.
Over 85% of asphalt is used to make asphalt concrete
Over 85% of asphalt is used in asphalt concrete. This article focuses on asphalt concrete for road surfaces.
Characteristics of Asphalt Durability
Asphalt has a number of characteristics that lend it to road construction and are important in transporting vehicles safely. Aspects of asphalt important to roads include durability under load, tire wear, braking efficiency both wet and dry, and road noise.
Asphalt Concrete is a elastic based material. The modulus of elasticity dictates the flex of the surface under axle load and ultimately the life of the road surface. Ultimately micro strains result in tears in the material that result in failure over time. These micro strains are related to the elasticity of the asphalt and vary based on asphalt temperature, duration of load, amount of load and frequency.
Optimal operation of asphalt is above 40 degrees F
The optimal operating temperature of asphalt is where it is in the elastic phase. Above elastic phase is the viscous phase and below the elastic phase is the brittle phase. The elastic phase runs approximately from 40 degrees F to 150 degrees F. Below this temperature, asphalt becomes brittle and is more susceptible to micro tears. That said, even though the air and ground temperature may be well below 40 degrees, repeated vehicle use warms the pavement significantly pushing it back into the elastic range. Less frequently used highways will experience more deterioration due to micro tears that brittle conditions although the less frequent use will at the same time reduce the incidence of micro tearing.
Another key factor in the durability of asphalt concrete is its impermeability. This is impermeability to air and water. Impermeability is less a measure of the number of voids in the asphalt than it is the characteristics of the voids. Are the voids exposed to the surface? Are they interconnected? Are the voids large or small? Permeability impacts asphalt in two ways and is unavoidable in asphalt mixing.
Water permeability results in fracturing of the asphalt
Water permeability results in water intrusion into the asphalt body. Water intrusion that is then allowed to freeze, expands inside the asphalt splitting open the asphalt causing fissure that then lead to additional intrusion.
Air permeability results in the volatile oils in the asphalt evaporating to the atmosphere. It is the volatiles in the asphalt that provide heavily to the elastic nature of the road surface. As these volatiles escape over time the asphalt becomes more brittle with an increase in micro tears, leading to failure.