Influence of spatial and thermal factors on the in-situ elastic modulus of cold-in-place recycling layer using light weight deflectometer

Cold in-place recycling (CIR) is a sustainable technique for pavement rehabilitation, offering environmental and economic benefits. However, the mechanical behaviour of CIR mixtures, particularly the evolution of in-situ elastic modulus during early curing, remains critical for performance assessment and quality control. This study investigates the influence of thermal effects, spatial heterogeneity and curing time on the in-situ elastic modulus of CIR layer. Field measurements were conducted on national roads 170 in Rivière-Éternité and 167 in La Doré, located in the north of Québec province, in Canada, using light weight deflectometer (LWD). Tests were performed at 0, 1 and 24 h following compaction. To minimise bias due to temperature differences, elastic modulus values were normalised to a reference temperature of 20 °C. The results confirmed the importance of temperature correction for capturing the in-situ elastic modulus of CIR materials. Significant spatial heterogeneity was observed both longitudinally and transversely, with consistently higher stiffness where traffic circulated during construction. Moreover, stiffness gains during the first 24 h of curing highlighted the need for early-stage monitoring. These findings support the implementation of systematic and randomised LWD testing, thermal normalisation and statistical analysis to improve construction practices and ensure the long-term performance and uniformity of CIR pavements.