As part of the LINK Transport Infrastructure and Operations Programme, research was carried out to enable the use of secondary aggregates and binders in pavement foundations. This report describes laboratory testing of mixtures including secondary aggregates and binders, and a full-scale trial of six sub-bases constructed with these mixtures, carried out in TRL's Pavement Test Facility (PTF). The secondary materials investigated were confined to those of immediate interest to the industrial sponsors and were china clay sand, blastfurnace slags, basic oxygen steel (BOS) slags, pulverised fuel ash, gypsum and cement kiln dust. Initially thirteen mixtures of secondary materials, sometimes combined with conventional aggregates and binders, were selected for testing in the laboratory. The mixtures divided into three families, according to whether the major component was fine, medium or coarse aggregate. The fine aggregate was either pulverised fuel ash or gypsum, the medium was china clay sand and the coarse was either crushed granite or air-cooled blastfurnace slag. Each mixture was tested for compactibility, compressive strength, indirect tensile strength and stiffness and durability. Six of the mixtures also underwent further testing, to examine the effect, on the structural properties, of small changes in both moisture content and the proportions of constituents. The effects of curing temperature and the workability time were also investigated. The components of these mixtures were: Pulverised fuel ash, gypsum and quicklime; Pulverised fuel ash, cement kiln dust and granulated blastfurnace slag; China clay sand, cement kiln dust and ordinary Portland cement; China clay sand, pulverised fuel ash, quicklime and sodium carbonate; Crushed granite, pulverised fuel ash, quicklime and gypsum; Air cooled blastfurnace slag, granulated blastfurnace slag and basic oxygen steel (BOS) slag. The mixtures were then laid as sub-base in full scale trials together with control sub-bases of unbound granular, Type 1 and CBM1 material. Each sub-base was laid as a wedge, on pre-shaped subgrade, the thickness varying along the direction of trafficking. The performance of the resulting foundations, under wheel loads representative of construction traffic, was assessed by measuring deformation in the wheelpath, ruts and the surface modulus of the foundation obtained from Falling Weight Deflectometer (FWD) testing. The results of the laboratory and full-scale trials are presented and demonstrate the potential for the use of secondary aggregates and binders in road pavement foundations. Based on these results, a procedure for the mix and thickness design of sub-bases comprising secondary material is proposed. The benefits of constructing foundations incorporating secondary materials are discussed. (A)

Want to know more about this project?