EuLA (2012): Hydrated lime is a multi-functional asphalt modifier (Slides Eurobitumen).

ROAD AGENCIES ESTIMATE THAT ITS BENEFITS LEAD TO AN INCREASED DURABILITY OF 25%.

This presentation highlights the benefits of using hydrated lime in asphalt, as a multi-functional modifier:

• Road agencies estimate that its benefits lead to an increased durability of 25%.
• Adding hydrated lime to asphalt improves resistance to:

Moisture and frost: Lime neutralises the carboxylic acids in the asphalt, replacing them with stronger nitrogen bonds between the aggregate and the bitumen. These will remain in the presence of water, thus preventing stripping.

Chemical ageing: Hydrated lime has an anti-ageing effect on bituminous materials. Hydrated lime reduces the oxidation of bitumen, notably by reacting with asphaltenes, allowing a slower increase of viscosity.

Rutting: Unlike most mineral fillers, hydrated lime is porous. When it is dispersed throughout the mix, its porosity is filled with bitumen, making the overall asphalt mixture stiffer at high temperature.

Fatigue cracking: Cracking can result from traffic-induced fatigue as the pavement weakens and becomes more brittle over time. Hydrated lime particles act as crack arresters and are able to intercept and deflect micro-cracks as they begin to form.