Freeze-thaw performance of phase change material (PCM) incorporated pavement subgrade soil Masrur Mahedi a , Bora Cetin b,⇑ , Kristen S. Cetin c a 136 Town Engineering Building, Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA b 494 Town Engineering Building, Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA c 428 Town Engineering Building, Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA highlights  Integration of PCMs into frost-susceptible loess soil to reduce freeze-thaw impact.  Liquid and microencapsulated PCM addition in untreated and fly ash treated soil.  Higher normalized unconfined compressive strength of PCM-fused soil in freeze-thaw.  Reduction in volume changes, heave rates and thaw rates for PCM addition.  Supports the use of PCM in controlling freeze-thaw impact on subgrade soil. article info Article history: Received 17 October 2017 Received in revised form 7 December 2018 Accepted 30 December 2018 Keywords: Freeze-thaw Frost susceptibility Heaving Thaw weakening Frozen soil Pavement subgrade abstract Phase Change Materials (PCMs) can store and release large amounts of energy in the form of latent heat during their phase changes, which could be utilized in controlling the freeze-thaw impact on pavement foundation systems. Untreated, and Class C fly ash-treated loess soil amended with three different dosages of paraffin-based liquid, and microencapsulated PCMs were evaluated using unconfined com- pression, volume change, and frost heave tests. The results of this research support the use of PCMs in controlling the freeze-thaw effect on subgrade soil. Further recommendations are provided on PCMs selection, composite type PCMs, incorporation method, and chemical stability. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Frost heaving and thaw weakening causes substantial damage to pavement subgrade soils in cold regions such as northern Eur- ope, Alaska, Canada and the Midwestern portions of the United States [1]. These cold regions can be either seasonal frost areas or permafrost areas where the ground surface remains partially frozen even in the summer [2]. In the United States, 70% of road networks are low-volume roads, and half of these are located in seasonal frost areas [3]. About 68.4% of the land surface in China is covered by permafrost and seasonal frozen ground, causing sub- stantial damage to geotechnical structures due to freeze-thaw action [4]. The permafrost degradation on the Qinghai-Tibet Pla- teau, China is the source of extensive geo-hazards for pavements, including thawing settlement, frost-heave and freeze-thaw induced risks [5–7]. In Russia, 80% of the country is a cold and humid soil forming environment with negative soil temperatures [8]. According to a study conducted by Frauenfeld et al. [9], the active layer depth of the permafrost regions in Russia has increased by 20 cm between 1956 and 1990; this is even greater for season- ally frozen ground. The active layer undergoes freezing and thaw- ing during each warm and cold seasons, which may lead to significant pavement deteriorations. Aho and Saarenketo [10] also identified seasonal changes and freeze-thaw cycles as the major factors affecting pavement conditions in cold, northern Europe. The estimated annual road repair costs in Finland, Norway and Sweden is approximately $10 million per country due to frost- heave damages [11]. In Iowa, where this study was undertaken, this problem is very acute due to its geographic location in wet-freeze zone with widely https://doi.org/10.1016/j.conbuildmat.2018.12.210 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: mmahedi@iastate.edu (M. Mahedi), bcetin@iastate.edu (B. Cetin), kcetin@iastate.edu (K.S. Cetin). Construction and Building Materials 202 (2019) 449–464 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat