This report deals with methods of upgrading low-quality coarse aggregates to acceptable durability and strength levels for use in bituminous and Portland cement concrete pavement mixtures. The findings, based on laboratory testing, will be of interest to engineers concerned with design, construction, and performance of highway pavements. The performance of high-type pavements, of either PCC or bituminous concrete, is influenced by many factors, Some of these are materials, environment, traffic loading, construction practices, and maintenance. One of the most important factors in the satisfactory performance of a pavement is the incorporation of coarse aggregate consisting of sound, durable particles free from objectionable coatings. The rapid depletion or inaccessibility of such high-quality aggregates requires that methods be devised for upgrading of low-quality materials. The objective of this study was to advance methods of upgrading coarse aggregates for use in bituminous and PCC pavement mixtures. The upgrading procedures studied were impregnation, coating, and chemical treatment. The beneficiation addressed recognized problems such as freeze-thaw damage, stripping, degradation, alkali-aggregate reactions, and D-cracking. This study did not address (a) pavement surface characteristics, such as skid properties, texture, and roughness, or (b) mixtures applied as seal coats or thin surface treatments. Several upgrading methods studied in the project have shown significant promise and are recommended by the researchers for further refinement. A preliminary guide for field evaluation of upgrading procedures is included in an appendix. (Author/publisher)
Samenvatting