Method of quantification of hydrated lime in asphalt mixtures

Hydrated lime has been known as an additive for asphalt mixtures for a long time and is now considered as an additive that increases asphalt mixture durability. It has been extensively used in the past 40 years in the USA, and is being increasingly used in most European countries, in particular Austria, France, the Netherlands, the United Kingdom and Switzerland. Given this context, it is necessary to have a fast and reliable quantification method of the hydrated lime content in an asphalt mixture. an method was used in order to do so. The test method consisted first in recovering the filler from the asphalt mixture using the usual solvent extraction method (EN 12697-1). Then, 1 g of the recovered filler was titrated with a 0.5 M HCl solution using a method adapted from EN 459-2. The test method was validated on an AC 10 mixture manufactured in the laboratory. The nominal content was 2.0% hydrated lime based on the dry aggregate. The measured content was found to be 1.7%, in reasonable agreement with expected results. esult, the hydrated lime content in an asphalt mixture can be evaluated. An estimate of the precision of the method is also given thanks to an international round robin test, showing that the repeatability of the method is close to 0.7% and its reproducibility 4.5% in terms of Ca(OH)2 content in the recovered filler.