In Situ Thermal Performance of Lightweight Aggregates Expanded Clay and Foam Glass in Road Structures

摘要

Transport infrastructures built on frost-susceptible soils may require insulation layer to minimize frost penetration. In Norway, one of the approaches is the use of lightweight aggregates (LWA) as an insulation layer, especially when there are specific restrictions for pavement thickness. Performance and design thicknesses of LWA are included into the Norwegian Road Design Handbook. The current regulations allow the use of LWA layers with or without an underlying lower frost protection layer (LFPL). The goals of this paper are to a) observe the frost insulation capacity of lightweight aggregates and b) investigate the necessity of lower frost protection layer below the lightweight aggregate layer. A full-scale road test site was built in Roros, Norway, with three sections using LWA for insulation purposes. For these sections, a 0.6 m thick insulation layer of expanded clay (Leca) with particle size of 10/20 and 0/32 mm and foam glass (Glasopor) with particle size of 10/60 mm was constructed. An underlying LFPL with a thickness of 0.7 m was made of crushed rock material with particle size of 0/120 mm. Temperature was monitored for two winters (2016/2017 and 2017/2018). The cumulative surface freezing index (FI_s) for the two winters resulted in 22,630 and 36,683℃h respectively. Field observations show that the performance of all three insulations layers was generally the same. The results showed that for both winters the frost front remained in the LWA layer. The study shows that lightweight aggregates could be placed directly on frost-susceptible soils and the frost front will remain in the 60 cm insulation layer even at FI_s of 36,683℃h.