Saint John’s 18th-century Loyalist grid was never intended to carry port-container traffic along Water Street, and the original glacially scoured bedrock outcrops that made early construction easy now complicate uniform pavement behavior. The interaction between the thin, stiff marine clay veneer overlying the Precambrian basement and the region’s frequent freeze-thaw cycling—averaging over 85 cycles per year according to Environment Canada data—creates a subgrade support condition that oscillates between fully frozen and partially saturated within a single week. A rigid pavement design that ignores this rapid stiffness fluctuation will exhibit corner cracking within the first two winters, regardless of the slab thickness specified. Our team addresses this by incorporating dowel bar retrofit analysis and tied concrete shoulders into the structural model, referencing the National Building Code of Canada (NBCC) and CSA A23.3 for jointed plain concrete pavement (JPCP) systems. A CPT test across the site provides the continuous tip resistance and sleeve friction profile needed to delineate the marine clay thickness, while in-situ permeability measurements confirm whether the granular subbase can actually drain meltwater before it refreezes beneath the slab.
A rigid pavement slab in Saint John must survive 85 freeze-thaw cycles a year while transferring 90th-percentile container axle loads across joints that are actively moving.
