Getting the Most Out of Your Aggregate Base
The aggregate base is one of the most important components of any pavement structure. It provides structural support and creates a stable foundation on which to build the pavement surface layers. Follow these tips to ensure you’re maximizing the potential of your aggregate base:
Choose the Right MaterialsDense-graded crushed stone aggregates usually make the best base materials. They provide strength, stability, and good drainage capabilities. Using recycled concrete or asphalt can also work well. Avoid materials like sands or clay soils that can become unstable.
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Proper Compaction is Critical
The aggregate base needs to be thoroughly compacted to at least 95% of its maximum density, according to specifications. This removes any air voids and creates a tight, interlocked structure. Use the right equipment like rollers and haul only as much material as you can compact in a day.
Pay Attention to GradationA well-graded base with a distribution of particle sizes packs together effectively. The gradation will determine stability, permeability, and workability. Follow local specifications, but a typical base gradation might range from 1.5 inches down to dust/fines.
Don’t Ignore Thickness RequirementsThe thickness of the base is designed to handle expected loads and environmental conditions. Don’t be tempted to skimp on depth to save money. This can lead to premature failures, roughness, and cracked pavement down the road.
Allow Proper Curing TimeIt takes time for the compacted base to cure and harden through natural cementing of the aggregate particles. Follow curing time guidelines before paving over the base course. Rushing this risks weakening the base structure.
Conduct Quality Control Testing
Test for proper compaction and moisture content in the field with density gauges and moisture probes. Also take gradation samples and document with photos. This confirms specs are met and identifies any questionable areas.
In the state of Arizona, aggregate base is widely used for constructing pavements due to the hot, arid climate and regional soil conditions. Silty and clay-type soils that expand and contract with moisture are common in Arizona. A quality aggregate base helps prevent cracking and pavement failure by providing a stable subgrade layer that is less prone to movement. The Arizona Department of Transportation specifies using well-graded crushed stone aggregate for base materials on state highways. The typical base thickness on Arizona roads and parking lots ranges from 6 to 8 inches. Gravel and recycled asphalt are also sometimes utilized. Proper base construction and thickness is critical for pavement durability in Arizona’s desert environment.
Proper base construction and thickness is critical for pavement durability in Arizona’s desert environment. Premature cracking and failures are common when the base is inadequately constructed. The intense sunshine and temperature fluctuations can quickly deteriorate poor bases.
Aggregate base materials meeting Arizona DOT specifications are available from quarries across the state. When installed correctly, the base provides the foundation for long-lasting pavements that can withstand Arizona’s climate and heavy traffic loads.
The City of Scottsdale utilizes minimum 8 inch bases, increasing to 10 inches for arterial streets.
Phoenix and Scottsdale both follow the same Maricopa County transportation department specifications for crushed stone base aggregates. Testing for gradation, abrasion resistance, and moisture is conducted for quality control during base installation.
Following regional best practices for aggregate base construction enables Phoenix and Scottsdale to build stable pavements that can withstand their desert environment. Well-constructed bases are the key to preventing premature cracked and deteriorated pavement surfaces on heavily traveled urban roads.
