Evaluation of pavement load bearing capacity comprised of insulation layers during thaw season

One of the strategies for minimizing the negative effects of freezing on frost-susceptible subgrade is placing insulation layers on top of the subgrade. This technique helps to mitigate the formation of ice lenses and frost heave in the subgrade and subsequently reduces the associated damage. Using insulation layers prevents subgrade strength reduction that results from the existence of excess water formed from melted ice lenses during thaw season. This paper evaluates the effect of using bottom ash, a recently introduced by-product of power generation, as an insulation layer, as well as the effect of commonly used polystyrene boards on subgrade resilient modulus variations during thaw season at the University of Alberta’s IRRF test road facility in Edmonton, Canada. To evaluate the subgrade strength, Falling-Weight Deflectometer (FWD) testing was conducted at 10-m intervals along the test road during thaw season. The back-calculated moduli from deflection basins were used to determine the resilient modulus of the insulated sections and the control section. The study results revealed that using polystyrene boards as insulation layers protected the subgrade soil from freezing and thawing effect; however, it also reduced the pavement bearing capacity. The bottom ash layer was affected by freeze-thaw, but it could properly protect the subgrade soil without having an adverse effect on pavement bearing capacity.