Performance Evaluation of Different Insulating Materials using Field Temperature and Moisture Data

Abstract

Including insulation layers in pavement structures has become a common strategy to minimize frost penetration in cold regions. This study investigated the performance of two different insulation materials, extruded polystyrene board and bottom ash, in a test road in Edmonton, Alberta, Canada, eight years after construction. The two insulation materials were used in a fully instrumented test road, including three insulated sections 20 m in length. The insulated sections are as follows: the first section has 1 m of bottom ash (B. Ash), the second section has a 10 cm polystyrene layer (Poly-10), and the third section has a 5 cm polystyrene layer (Poly-5). Both B. Ash and polystyrene layers were placed on top of the subgrade layer, at a depth of 70 cm from the surface. A conventional section next to these three sections was used as the control section. Volumetric water content data and temperature variation were used to analyze the influence of the insulation materials on the subgrade. It was concluded that both B. Ash and Poly-10 layers protected the subgrade from freezing. The Poly-10 section showed the lowest rate of change in subgrade temperature during the monitoring period. B. Ash and Poly-10 reduced the frost depth by 23% and 70% compared with the control section, respectively. It was concluded that Poly-10 protected the subgrade soil from freezing and excessive moisture more effectively than B. Ash; however, the temperature in the layer above the insulation layers (pavement base layer) was significantly lower during winter for the Poly-10 section.

Structural Capacity of Sections Constructed with Different Waste and Recycled Embankment and Insulation Materials at the Integrated Road Research Facility Test Road after Five Years of Operation

“…There is a high correlation between the D 0 value and the temperature of the HMA layer ( 14 , 21 ). Polystyrene board leads to a higher HMA layer temperature in summer and lower HMA layer temperature in winter ( 5 ), and thus increases the likelihood of pavement damage ( 5 , 15 ). This fits with the higher deflection values observed for the pavements insulated with polystyrene board after five years of operation.…”

“…Previous studies have shown that the physical properties of BA make it a high-quality base material (11,12). BA acts as an insulation layer to protect the subgrade from frost in winter (5,8,13). Haghi et al (8,(14)(15)(16) found that polystyrene and BA protected the subgrade layer from frost.…”

“…Based on air temperature data from 2012–2020, the average air freezing index (the sum of degree-days with a daily air temperature below 0°C during a given time period) during the freeze–thaw period was 1177°C day at the IRRF test road. Similarly, the average air thawing index (sum of degree-days above 0°C for the air temperature during the freeze–thaw period) was 662°C·day over the same time period ( 5 , 6 ).…”

“…Polystyrene board is a traditional insulation material and has been used since 1967 to protect pavement structures against frost damage ( 7 ). Several studies have shown that polystyrene boards can reduce thaw depth and protect the subgrade from frost heave ( 5 , 8 , 9 ). BA is one by-product of coal combustion.…”

“…Furthermore, the section insulated with BA showed similar viscoelastic behavior as the CS; however, the pavement insulated with polystyrene was more prone to damage in summer because of the higher HMA temperature ( 15 ). Huang et al ( 5 ) compared the pavement temperature and moisture content six years after the completion of road construction. The researchers found that the pavement insulated with polystyrene showed less moisture variation than pavement insulated with BA; however, again the polystyrene section was shown to have a much lower base layer temperature than the CS in winter, which may make the polystyrene section more prone to low-temperature damage.…”