Recent developments in hot mix asphalt (HMA) have increased production, reduced cost and environmental impacts, and improved performance. This article covers some new developments in HMA materials, mixtures, and road construction. The types of materials used include aggregates, asphalt cement, adhesives such as fibres and anti-strip agents, and various types of polymers. The types of aggregates used can have a large effect on performance, and good aggregates are usually hard, angular, essentially cube-shaped, and clean. Tests are needed for accurate assessment of aggregate quality; one new test is the fine aggregate angularity test. HMA mixture types, which have been used to construct pavements for various traffic levels, include: (1) stone mastic asphalt (SMA), whose greater durability can more than justify its higher cost on roads with heavy lorry traffic; (2) large stone mixtures, which could carry greater loads; (3) porous asphalt mixtures of various types, to drain surface water and minimise hydroplaning; and (4) Superpave. A test method is still needed for the adequate prediction of HMA performance. More work is needed to develop plants that can make asphalt of more consistent quality. Recently, advances have been made in quality control and quality assurance for constructing asphalt pavements.
Samenvatting