PRELIMINARY STUDY TO DETERMINE THE RELATIONS BETWEEN STRENGTH VALUES AND BREAKING UP DURING THE LAYING OF BITUMINOUS MATERIALS

VORSTUDIE ZUR ERMITTLUNG VON ZUSAMMENHAENGEN ZWISCHEN FESTIGKEITSKENNWERTEN UND ZERTRUEMMERUNGEN BEIM EINBAU BITUMINOESER MASSEN

THE AIM OF THE WORK WAS TO INDICATE PARTICLE REFINEMENT AND BREAKING UP DURING THE LAYING OF BITUMINOUS MIXTURE. LABORATORY AND SURFACING SAMPLES OF LIMESTONE AND BASALT WERE EXAMINED. BY COMPARING THE COMPACTION COEFFICIENTS (BULK DENSITY AND VOIDS CONTENT) RELATIONS WERE OBTAINED BETWEEN THE MARSHALL SAMPLES AND THE SAMPLES FROM THE SURFACING WHICH HAD BEEN COMPACTED WITH FINISHERS AND TANDEM VIBRATING ROLLERS. TO EVALUATE THE CHANGES IN THE BITUMINOUS MIXTURE CAUSED BY THE COMPACTION EQUIPMENT, THE TOTALS OF THE RESIDUES ON THE TEST SIEVE WERE DETERMINED BEFORE AND AFTER COMPACTION. THE TESTS SHOWED THAT PARTICLE BREAKING UP IS AN UNDESIRED RESULT OF AN INCREASE IN BULK DENSITY BROUGHT ABOUT BY THE COMPACTION EQUIPMENT, AND THAT THIS BREAKING UP INCREASED AS LAYER THICKNESS DECREASED. IT WAS ALSO ESTABLISHED THAT THE DIFFERENCE IN THE DEGREES OF BREAKING UP OF VARIOUS ROCKS DECREASES MARKEDLY WHEN THERE IS A LOWER VOIDS CONTENT IN THE INITIAL MIXTURES. IN ALL THE TESTS THE HARDER BASALT ROCK BROKE UP LESS THAN THE LIMESTONE, SHOWING THAT THE STRENGTH CONDITIONS OF THE MINERAL ARE REFLECTED WHEN THE ROCKS ARE USED IN BITUMINOUS MIXTURES.