Solid Antistrip for Roads: Amine Impregnated Zeolite (AIZ)

Background

Moisture damage in bituminous composites used in roads, roofs, and other asphalt applications can reduce the service life of these infrastructures. Antistripping agents are chemical additives added to asphalt mixture in order to improve the durability of asphalt by reducing its susceptibility to moisture. The use of hydrated lime (solid antistripping agent) and amine-based additives (liquid antistripping agents) to mitigate the damage is an effective and commonly used method in the industry. However, lime production is a source of anthropogenic CO2 emissions, and amine-based additives lose their effectiveness over time when exposed to weathering and UV radiation.

Zeolites are porous materials that are compatible with asphalt components and are commonly used materials in the asphalt industry. Zeolites have inherent thermal insulation capabilities that can protect amine molecules from degradation when exposed to weathering, UV radiation, and high temperatures during asphalt production, placement, and service life.

Invention Description

Researchers at Arizona State University have developed a novel solid antistrip agent, amine impregnated zeolite (AIMZ), that protects bituminous composites against premature aging, weathering, and UV radiation. The liquid amine agent is loaded into the zeolite pores within AIMZ, and slowly releases over time and on demand to protect against moisture damage and counter the effects of weathering, UV radiation, and high temperatures on pavements and help extend its service life.

Initial tests on AIMZ showed that samples containing excess amines initially (before aging) had higher resistance to moisture damage compared to the amine-impregnated zeolite, but superior performance of AIMZ is revealed after aging occurs. AIMZ made from zeolite as the solid agent and ethylenediamine as the liquid amine agent continuously showed higher resistance to moisture damage as aging progresses, due to the slow release of retained amines under an external stimulus induced by aging. Latter slow release extends the effectiveness of amines when protected from early aging by being retained within zeolite pores.

Potential Applications

• Asphalt applications (e.g., roads, roofs, bridges, airports, parking lots)
• Replacement of lime as antistrip agent

Benefits & Advantages

• Enhanced thermal insulation
• Improves resistance of asphalt mixtures against moisture damage, aging, weathering, and UV radiation
• Retains volatiles and small molecules of asphalt to reduce odors and emission
• Facilitates CO2 sequestration and reduces carbon footprint of asphalt-surfaced areas

Related Publication: Exploratory Synthesis of Low-Silica Nanozeolites through Geopolymer Chemistry