Field study on thermal behavior of lightweight cellular concrete as pavement subgrade protection in cold regions

Extremely low temperatures and freeze-thaw cycles cause premature cracking and low pavement bearing capacity. However, insulation layers could influence the extent of the temperature on pavements. This study focused on understanding the thermal behavior of lightweight cellular concrete (LCC) as an insulating subbase layer to protect the subgrade in pavements. The thermal performance was compared to a Control with Canada's conventional unbound subbase pavement structure. Empirical statistical temperature prediction models were developed based on two years of field data obtained from an instrumented test road in Waterloo, Ontario, Canada. The regression models were based on the most important factor, ambient temperature. This was determined by using a Generalized Addictive Model assessment process. Hourly pavement temperature data across the four seasons in Canada were studied. The effect of daily cooling and heating on pavement layer temperature was also evaluated. Results revealed that a 200 mm thick LCC subbase layer with a density of 400 to 475 kg/m3 could prevent the subgrade directly beneath it from freezing during harsh winters. Thicknesses equal to or >350 mm could be even more beneficial in alleviating the possibility of a frozen subbase and subgrade. There were 70 freeze-thaw cycles recorded in the subgrade of the conventional pavement, but none in the >250 mm LCC pavement portion. When the temperature models were validated using 13 months of data, satisfactory results were obtained. This study enables the prediction of the thermal behavior of LCC subbase pavements for future applications.