BITUMINOUS MIXTURES IN THE GENERAL TECHNICAL STANDARDS OF THE "DIRECCION GENERAL DE CARRETERAS". RECOMMENDATIONS FOR SPECIAL STANDARDS

THE NEW GENERAL TECHNICAL STANDARDS PUBLISHED IN 1975 CONTAINED 2 ARTICLES ON BITUMINOUS MIXTURES, ONE ON COLD-COATED MATERIALS AND ONE ON HOT-COATED MATERIALS. THE DEFINITION OF ASPHALTIC CONCRETE IS THAT FOUND IN THE INTERNATIONAL TERMINOLOGY OF ASPHALTIC CONCRETE AND DOES NOT INCLUDE ANY OTHER TYPES OF MIXTURES (GAP GRADED AGGREGATES, MASTIC, MELTED ASPHALT OR MICRO-CONCRETE) AS THEY ARE NOT OFTEN USED. THE TENDENCY IS TO REDUCE USES BASED ON GRADING, ALTHOUGH THIS WAS FOUND TO BE DIFFICULT BECAUSE OF THE TRAFFIC COMPOSITION AND CLIMATE IN SPAIN. THE CRITERIA FOR BITUMINOUS BINDERS IS A REDUCTION IN THEIR NUMBER AND RIGIDITY IN SAMPLING. CHANGES CONCERNING AGGREGATES ARE THE SHAPE OF THE GRAINS AND COEFFICIENT OF ACCELERATED POLISHING. IN LAYERS OF HIGH QUALITY BEARING HEAVY TRAFFIC, FILLER MUST BE ADDED. 4 TYPES OF GRADING ENVELOPES HAVE BEEN DEFINED: DENSE BITUMINOUS MIXTURES, SEMI-DENSE MIXTURES, COARSE, AND OPEN MIXTURES. THERE ARE THREE ENVELOPES IN EACH GROUP AS A FUNCTION OF THE MAXIMUM SIZE OF THE AGGREGATES. SPECIAL SPECIFICATIONS WILL HAVE TO DEFINE WHICH ENVELOPE IS BEST ADAPTED TO A CASE AS A FUNCTION OF LAYER THICKNESS, TRAFFIC AND PAVEMENT STRUCTURE. AS REGARDS MECHANICAL CHARACTERISTICS MARSHALL TEST IS THE ONLY TEST USED. FOR THE COVERING ABSTRACT SEE IRRD ABSTRACT NO 108595.