Thickness Design of PCC/FBC Composites for Secondary/County Roads

Abstract

Tests were conducted in the laboratory and field to determine the extent to which fluidized bed combustion (FBC) spent bed and pulverized coal combustion (PCC) fly ash, by products of the coal industry, can be used in low-volume county and secondary roads. Various proportions of prehydrated FBC spent bed (as a secondary aggregate and an agent to activate pozzolan oxides), PCC fly ash (as a primary cementitious binder), natural fine aggregate (as a primary filler), and a low dosage of Portland cement (as a secondary cementitious compound) were blended and compacted at their optimum moisture content to ascertain their suitability as base course materials. These tests and experiments were used to assess the performance of the selected PCC/FBC base course composites. On the basis of the results, thickness-design tables of PCC/FBC base courses were developed. Results indicate that the engineering properties of the PCC/FBC composites exceed those of the conventional mixes used in low-volume roads. The field results verified that the engineering characteristics of the laboratory mixtures can be easily duplicated in field.