VALORIZATION OF SAND WITH HIGH METHYLEN BLUE VALUE INTO BITUMINOUS MIXTURES FOR WEARING COURSES

摘要

Most European nations use washed sand to design their bituminous mixtures for wearingcourse, primarily to prevent excessive water sensitivity of asphalt due to the presence of clays insand natural fines. The lack of fines is then offset by an addition of limestone filler. Thesepractices lead to high water and energy consumption. France, Belgium and Denmark areexceptions: they use quarry sands with their natural fines, without washing, but after checkingthe harmfulness of fines (clay content) according to French specifications described in the XP P18-545 standard section 8, a maximum methylene blue value of 2 g/kg is permitted.In order to save natural resources and improve the valorization of unwashed quarry sands,investigations have been carried out since 2007 on two quarry sands with methylene bluevalues in the range of 2 to 4 g/kg to study the behavior of bituminous mixtures for wearingcourse incorporating these unwashed sands.These two sands coming from eruptive quarries of Burgundy (rhyodacite and rhyolite) werehence characterized by numerous tests, including cationic exchange capacity (CEC)measurements and mineralogical analysis by X-ray diffraction, showing the presence of illitemuscoviteand montmorillonite. These sands were subsequently tested in the laboratory todesign asphalt wearing course (0/10 Asphalt Concrete). Finally, these mixes were laidrespectively in 2007 and 2009 on two experimental sites located on the French secondary roadnetwork. After 1 and 3 years of monitoring, no abnormal behavior induced by the presence ofclay could be observed. This initial assessment allows us to consider valorizing these materials,particularly through the development of a regional technical manual regarding the sands ofthese two studied quarries, then by the writing of a user regional guide.