Why do thermoplastic road markings crack, fade, or peel off? This article explains the causes and solutions.

Thermoplastic road markings are the “language of the pavement,” guiding traffic and ensuring travel safety. With advantages such as rapid installation, excellent wear resistance, and strong reflectivity, they are widely used on highways, urban roads, industrial parks, and parking lots. However, some markings begin to exhibit cracking, fading, and peeling shortly after being put into service, reducing their visibility and creating potential safety hazards. Today, we’ll examine three common types of distresses and explore effective preventive maintenance strategies.

1. Pavement Marking Cracking: Cracks Caused by Thermal Expansion and Contraction

Disease manifestations: The pavement markings develop hairline cracks and network‑like fissures; in severe cases, the cracks become through‑going and material spalls off. Rainwater infiltration further exacerbates the damage. Cracking is not solely a defect of the coating itself but results from the combined effects of multiple factors: poor coating flexibility, excessive heating during hot‑melt application, and prolonged boiling can render the coating brittle; preexisting pavement cracking can lead to reflective cracking, which in turn damages the markings; uneven coating thickness, forced application at low temperatures, and the cyclical temperature variations throughout the year—causing repeated thermal expansion and contraction—can all contribute to cracking.

Countermeasures: Select coatings based on regional climate—prioritize formulations with high flexibility and low‑temperature resistance in northern areas; strictly control the melt temperature to prevent prolonged heating. Before application, address pavement potholes and cracks in advance; ensure uniform coating thickness and avoid working in frosty or cold conditions. Minor cracks can be sanded and repaired, while extensive network‑like cracking should be removed and resurfaced.

II. Line Marking Fading: Aging and wear reduce visibility.

Disease symptoms: White road markings turn yellow, colored lane markings darken, nighttime reflectivity deteriorates, and daytime visibility is significantly reduced. Main causes: Low‑grade coatings have poor weather resistance, with prolonged UV exposure leading to pigment degradation and powdering; excessively high temperatures in the hot‑melt kettle cause premature yellowing; vehicle traffic, combined with oil contamination from exhaust and erosion by de‑icing salts, wears away the surface layer; insufficient application of reflective glass beads or inadequate embedding depth results in failure of the protective layer, accelerating aging.

Countermeasures: Use nationally‑standardized, weather‑resistant thermoplastic coatings; standardize the thermoplastic application process by avoiding prolonged, repeated boiling of the coating and promptly removing any carbonized residue from the kettle. During construction, evenly sprinkle glass microspheres in sync with the coating to enhance reflectivity while protecting the surface layer. For mild fading, sand the surface and recoat directly; for severe chalking and discoloration, thoroughly remove the existing pavement markings before repainting.

3. Pavement marking peeling and flaking: bond failure, complete delamination.

Pavement distress manifestations include edge lifting and small‑scale spalling; in severe cases, entire sections may peel off the pavement surface. These are relatively serious defects, often stemming from inadequate adhesion. Insufficient pavement cleaning—leaving behind dust, oil, and moisture—failure to remove laitance from cement pavements, improper selection of primer, or application before the primer has fully cured, as well as construction conducted on wet pavement with low surface temperatures after rain, and overlapping new and existing markings, can all lead to bond failure, resulting in peeling and delamination.

Countermeasures: Prior to construction, thoroughly clean and grind the pavement surface to remove laitance and oil contamination; the surface must be completely dry. For cement pavements, use a compatible primer; apply the road markings only after the primer has surface‑dry. When resurfacing existing markings, grind away any loose old coating. For localized flaking, sand down the area, apply a primer, and then repair it; for extensive delamination, it is recommended to remove the entire layer and reapply.

Pavement thermoplastic markings often develop defects due to a combination of factors—no single cause can be isolated. Materials, substrate, construction practices, and environmental conditions all play critical roles. Though modest in size, road markings shoulder significant safety responsibilities. By adhering to standardized construction procedures and conducting regular maintenance, we can minimize marking deterioration, ensuring that every road marking remains clear and durable, thereby safeguarding travel.