TESTING TECHNIQUES FOR DETERMINING THE SUITABILITY OF GUSSASPHALT MIXTURES FOR USE IN HIGHWAY CONSTRUCTION

GUSSASPHALT HAS BEEN PROVED TO BE AN EXTREMELY DURABLE MATERIAL FOR THE CONSTRUCTION OF ROAD PAVEMENTS. THE MINERAL AGGREGATE CONSISTS OF CHIPPINGS, NATURAL AND/OR CRUSHER SAND AND ALSO FILLER, THE PROPORTION OF WHICH VARIES AROUND 25% BY WT. THE BINDER, WHICH SHOULD COMPLETELY FILL OR SLIGHTLY EXCEED THE VOLUME OF VOIDS OF THE WELL COMPACTED MINERAL MIXTURE, GENERALLY CONSISTS OF ROAD CONSTRUCTION BITUMEN B45, WITH ADDITIVES OF TRINIDAD-EPURE OR LUCOBIT TO INCREASE VISCOSITY. THE FILLER ALSO HAS A STIFFENING EFFECT WHICH MAY BE ASSESSED BY THE RISE OF THE SOFTENING POINT IN THE RING AND BALL TEST. A PARTICULAR PROBLEM WITH GUSSASPHALT IS THE CONDUCT OF ACCEPTANCE TESTS IN THE LABORATORY, BECAUSE THE BOILING EFFECT CAN IN PRACTICE ONLY BE PARTIALLY SIMULATED. THE LABORATORY TESTS SHOULD THEREFORE ALWAYS BE CONFIRMED BY MEANS OF SITE TESTS. AS A MECHANICAL TEST, THE INDENTATION TEST WITH FLAT ENDED PLUNGER IS AVAILABLE, ADDITIONAL INFORMATION BEING DERIVED FROM THE VARIATION OF PENETRATION WITH TIME. IN THE FUTURE LIMITS WILL BE PLACED ON NOT ONLY THE PENETRATION AFTER 30 MINUTES BUT ALSO THE INCREASE BETWEEN 30 AND 60 MINUTES. WORK IS IN PROGRESS ON THE IMPROVEMENT OF THE PENETRATION TEST. ASPHALT BINDERS UNDER GUSSASPHALT MUST IN FUTURE HAVE VOID CONTENTS AS MEASURED IN THE MARSHALL TEST OF LESS THAN 2, OR BETWEEN 6 AND 10% BY VOL. DEPTHS OF PENETRATION ON STANDARD CUBES ARE FIXED IN THE TV BIT 6/75 AT 1 TO 5 MM, WHERE PARKING IS ALLOWED AT A MAXIMUM OF 2,5 MM. MORE STRINGENT REQUIREMENTS ARE SET DOWN FOR THE SOFTENING POINT OF THE EXTRUDED BINDER, WHICH IN FUTURE MUST NOT EXCEED 70 DEG C. MODERN LAYING TECHNIQUES HAVE CONTRIBUTED TO MAKE CONSTRUCTION USING GUSSASPHALT MORE INDEPENDENT OF WEATHER CONDITIONS.