MODERN CONCEPT OF BITUMINOUS MIXTURES FOR ROAD CONSTRUCTION

IN THE STUDY OF BITUMINOUS MIXTURES, RESEARCH WORKERS FROM THE ESSO STANDARD SAF LABORATORY IN MONT-SAINT-AIGNAN REFER TO SOME BASIC CHARACTERISTICS SUCH AS THE COMPLEX MODULUS, RESISTANCE TO TRACKING AND FATIGUE, AND DIRECT TENSILE STRENGTH. STANDARD TESTS ARE CARRIED OUT ON VERY DIFFERENT SAMPLES WHEN STUDYING COMPACTION, DISPOSITION OF THE AGGREGATES DUE TO THE EDGE EFFECT, AND THE PRODUCTS OBTAINED ON THE SITE BY MEANS OF INDUSTRIAL COMPACTION. THE ESSO RESEARCH WORKERS PREPARED IN THE LABORATORY SAMPLES VERY SIMILAR TO THOSE WHICH COULD HAVE BEEN OBTAINED ON A FULL-SCALE SITE. BASED ON THE RESULTS THEY COMPARED, THE AUTHORS PROPOSE MATHEMATICAL MODELS FOR DECIDING ON THE DESIGN OR MODIFICATION OF BITUMINOUS MIXTURES USED FOR SURFACINGS AND ROAD BASES. ATTENTION IS DRAWN TO THE FACT THAT IT IS NECESSARY TO ALWAYS REMEMBER THAT A BITUMINOUS MIXTURE IS A COMPROMISE AND THAT BY MODIFYING A CERTAIN PARAMETER THE EQUILIBRIUM OF THE WHOLE MIXTURE COULD BE ALTERED FOR THE WORSE. TABLES ILLUSTRATE THE LATTER POINT.