Implications of Swelling Clays on Asphalt Pavement Performance in Colorado

Asphalt pavements constructed directly over high plasticity clays appear to be more susceptible to premature cracking parallel to the gutter on curb and gutter pavement cross sections than pavements with crushed stone bases. This paper describes five factors common to two sites studied that may be contributors to this early distress. These factors are: cracking is top-down; moisture content of the subgrade soils beneath the cracks is higher than optimum; density of the subgrade soils beneath the cracks is lower than optimum; subgrade soils are highly plastic; full-depth construction; and all pavements had curb and gutter typical sections. In addition, similar pavements constructed on crushed stone bases in the vicinity of the full-depth pavements with the same construction and materials characteristics do not display this cracking. Results of this work warrant study of construction techniques with regard to optimum moisture and density requirements when paving full-depth asphalt over plastic clays