Cold-climate-resilient sustainable concrete with microencapsulated PCM and industrial slags for pavement infrastructure: Mechanical, thermal, and durability evaluation

Concrete pavements in cold regions are highly vulnerable to damage from freeze–thaw cycles, icing, and rapid temperature fluctuations, which promote cracking, moisture ingress, and surface deterioration, reducing service life and increasing maintenance needs. This study develops a sustainable, thermo-adaptive concrete incorporating microencapsulated PEG-400 phase change materials (PCM) and industrial slag aggregates, designed to stabilize temperature fluctuations while maintaining mechanical and durability performance. An interaction-based predictive model is also proposed to quantify the combined effects of PCM content, steel slag (SS), and slag cement (SC) on the thermal conductivity of concrete. Experimental results confirmed the trade-off between thermal and mechanical performance: at 10% PCM, compressive, tensile, and flexural strengths decreased moderately, whereas thermal conductivity increased by 45%; at 20% PCM, thermal conductivity increased by up to 60% with acceptable strength retention, particularly in slag-containing mixtures. The results highlight that optimal performance is achieved with 10–20% PCM and 50–100% slag, providing a robust balance among thermal efficiency, moisture resistance, and structural integrity. The proposed model offers a reliable tool for predicting and optimizing the thermal performance of PCM-modified concrete. The model was also calibrated and validated on multiple independent datasets from the literature, demonstrating excellent predictive performance, with a mean predicted-to-experimental ratio (MV) of 1.01 and a coefficient of variation (COV) of 15%.