Preliminary Feasibility Evaluation of Groove-Filling Thermochromic Polyurea Composites for Low-Temperature Visual Warning in Black Ice-Prone Pavements.

Black ice poses a serious winter road-safety hazard because its transparent appearance and localized formation make dangerous pavement conditions difficult to detect before vehicles enter affected areas. Converting this hidden low-temperature risk into visible surface information is therefore important for intuitive driver warning and road management. In this study, groove-filling thermochromic polyurea-based composites were fabricated using aliphatic polyurea resin, reversible thermochromic pigment (R.T.P.), and silica sand, and their colorimetric response, mechanical properties, and groove-filling applicability were investigated. Considering visual response and mechanical performance, the mixture containing 10 wt.% binder and 20 phr R.T.P. was selected as the most balanced candidate. For this mixture, the CIE L*a*b* values changed from 58.36, 3.85, and 13.32 for the control specimen to 47.82, 22.95, and 8.52, respectively, indicating a darker and more reddish appearance. The maximum compressive and flexural strengths were 10.13 MPa and 6.20 MPa, respectively. In addition, the selected mixture retained its low-temperature color response in the groove-filled state, confirming its preliminary groove-filling applicability. These results suggest the potential of thermochromic polyurea-based composites as visual-warning pavement materials for winter road safety.