An asphalt surface is typically called blacktop because of the color, but not all asphalt is black in color. This color of roads is determined by the input materials that consist of bitumen, an asphalt cement, and aggregate rock. Bitumen is naturally black, but there are some surfaces that use dies and even different colored rock to pave with.
Aggregate rock is the main input material for asphalt surfaces and comes from quarries. Rock quarries are placed in areas that have high bedrock deposits and supply local construction projects. The common aggregate that is used in paving consists of shale, limestone, gravel, and other input materials like recycled asphalt concrete.
Some input materials do change depending on what a local supply of resources are.
There are a wide array of mined resources in Texas that are used in industrial manufacturing, oil production and paving. Texas is also home to precious metal deposits like gold, silver, and titanium, but some of the most abundant materials are asphalt bitumen, caliche, sand, gravel, and crushed stone.
Asphalt bitumen is the binder or cement that is used in blacktop paving. The material has a moderate melting point which makes it great for hot mix concrete. Asphalt is found in limestone deposits and is extracted as an ore.
Caliche is a hard mineral deposit that consists of mineral deposits like nitrates, calcium, and aggregates like sand and gravel. In some cases, caliche is used as an input material for asphalt paving, but local city and county paving laws regulate its use. Some quarries refine the caliche bedrock to remove the limestone and other minerals leaving the useful aggregate.
Sand and Gravel
Sand and gravel deposits in Texas are typically found along rivers, near lakes, and in the mountain regions of Texas. A common source for many quarries in Texas is the Colorado River. Sand and gravel deposits are used in the construction industry for foundation construction, concrete paving, and in asphalt.
Roads in Arizona are sometimes red in color, this is not because of any dyes that are used, but because of the rock used as aggregate. Because it is not cost effective to ship stone and crushed rock long distances to be used in paving projects local quarries are often the supplier to local roads. Bedrock in Arizona is high in copper and iron deposits, which is why the rock is a dark red.
When the red rock is used as a paving material the road will not appear red at first. The top layer of asphalt cement will still give the road a black color, but over time the top layer will wear away turning the road red.
Some colored dyes are added to the asphalt cement to make different colors. This asphalt paving form is not commonly used because it tends to be more expensive and not feasible for large roads. Colored asphalt can be used to accent different roadway and surface features like an apex or finish line of a racetrack or a bike path.
Do you have a special paving project in mind? We at Lone Star Paving Company would love to hear what you have planned. Contact us today!