Material Matters - Fall 2012 - (Page 23)

AROUND THE HOT MIX INDUSTRY By Jim Murphy NYMaterials Technical Consultant Giving HMA Driveway Advice IT’S A SAFE bet that probably everyone involved with hot mix asphalt (HMA) pavements has been asked for advice on residential driveways. Whether you’re a producer, contractor, engineer or owner, people outside the business look at you as a “blacktop expert” and often ask for information on building a new driveway or repairing or sealing an old one. There is general consensus on how to answer these inquiries. First, you can assure homeowners that a properly designed, constructed and maintained HMA driveway will provide years of excellent service and will add appeal and value to the property. A well designed driveway will give trouble free service for up to 20 years. NEW INSTALLATION CONSIDERATIONS: • Good design • Good materials • Good construction Design - Before giving advice, it’s wise to look at the actual site conditions and understand the subgrade soil type, drainage, presence of utilities, type of loads, etc. The subgrade should be graded smooth, made free of organic materials and weak spots undercut and replaced with suitable material. Proper drainage provisions along with the final crown and slopes need to be addressed. A base course of 6 to 8 inches of crushed aggregate is usually adequate. For best results the ordinary residential HMA driveway pavement should consist of a 2-inch binder course covered with a 1.5-inch surface course. Materials - In regard to HMA, conventional mixes will provide satisfactory service. Dense binder surfaced with armor coat or similar driveway mix works well. It’s important that the mix be provided by an established reputable producer that services the location in question. New York Construction Materials Association members can provide specific mix recommendations for driveway applications. Construction - Good construction practice is critical in providing a satisfactory, durable end result. Work on the subgrade is important. Often backfill or fill areas around new homes are prone to future settlement. In some instances it’s wise to wait a few months before driveway installation. Base course aggregate should be spread evenly to the proper thickness, line and grade, and compacted with suitable rollers and compactors. Weed killer is sometimes applied to help prevent weeds from propagating through the section. Paving should be done only when weather conditions are good. Avoid cold rainy days. HMA should be delivered and used at the proper temperature. HMA should be machine placed — avoid hand work to the Material Matters • Fall 2012 23

Table of Contents for the Digital Edition of Material Matters - Fall 2012

Breaking the Bottlenecks
Glacial Materials Goes Emerald Green
The System Works
Giving HMA Driveway Advice
Promotion Doesn’t Cost – It Pays
Exposed Aggregate Pervious Concrete
Stuyvesant Falls Hydroelectric Plant: Steel Fiber Reinforcement in Action By Dan Casale

Material Matters - Fall 2012