Gradation variability assessment of thick-layer cement-stabilised full-depth reclamation

Abstract

The relatively high strength and stiffness of cement-stabilised pavement base layers have been utilised to facilitate construction and minimise pavement deflections for many years. Transverse cracking and overall durability concerns have also been associated with cement-stabilised layers, at least in part because balancing strength with durability and cracking resistance is a performance aspect often overlooked in design. This paper describes a laboratory investigation of full-depth reclamation materials from a project on US Highway 49 where recycling depths targeted 38 cm but varied considerably and, likely related to some degree, gradation also varied considerably from almost no particles passing 0·075 mm (P0·075) to around 30% P0·075 passing. This level of gradation variability (GV) was deemed worthy of a laboratory investigation into gradation effects on strength and durability. GV effects on wheel tracking, compressive strength under typical mix design conditions (i.e. 7 d moist curing) and compressive strength after durability-oriented conditioning (i.e. wetting and drying, freezing and thawing) were investigated. Insignificant practical effects on strength and durability were observed despite the tremendous GV. Overall, wheel tracking and 7 d moist-cured compressive strengths were reasonable for all gradations tested, and compressive strengths after durability-oriented conditioning indicated that durability was not a first-order concern.