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Hydrated lime has been known as an additive for asphalt mixtures from their very beginning. It experienced a strong interest during the 1970s in the USA, when moisture damage and frost became some of the most pressing pavement failure modes of the time.
Given its extensive use in the past 40 years in the USA, hydrated lime has been seen to be more than a moisture damage additive: Hydrated lime reduces chemical ageing of the bitumen and stiffens the mastic more than normal mineral filler above room temperature, which can in turn improve the mechanical properties of the mix.
Given that all the above properties impact the durability of asphalt mixtures, the use of hydrated lime has a strong influence on asphalt mixture durability. This article reviews the corresponding evidence found in the literature.
The field experience from North American State agencies estimate that hydrated lime increases the durability of asphalt mixtures by 2 to 10 years, that is by 20 to 50%.
The European experience is not yet as developed as in the USA, but the beneficial effects of hydrated lime on asphalt mixture durability have also been largely reported. The French experience suggest that hydrated lime modified asphalt mixture have a 20-25% longer durability. Similar observations led the Netherlands to specify hydrated lime in porous asphalt. As a result, hydrated lime is being increasingly used in asphalt mixtures in most European countries, in particular Austria, France, the Netherlands, the United Kingdom and Switzerland.