1. IN A PROCESS FOR OBTAINING A PARTICULATE MIXTURE ADAPTED FOR USE IN ROAD FOUNDATIONS, THE STEPS OF POURING A FIRST PORTION OF LIQUID SLAG SO AS TO FORM A RELATIVELY THIN LIQUID LAYER OF SLAG; ALLOWING SAID LIQUID LAYER TO COOL AND SOLIDIFY; BREAKING UP THE THUS SOLIDIFIED LAYER; LEVELLING THE THUS BROKEN UP LAYER; APPLYING A FINE SPRAY OF WATER TO SAID BROKEN UP LAYER SO AS TO MOISTEN THE SAME SUBSTANTIALLY WITHOUT FORMING ACCUMULATIONS OF WATER, SAID STEPS OF LEVELLING AND APPLYING A WATER SPRAY BEING CARRIED OUT IN ANY DESIRED SEQUENCE; POURING AN ADDITIONAL PORTION OF LIQUID SLAG ONTO THE LEVELLED AND SPRAYED SOLIDIFIED LAYER, SAID ADDITIONAL LIQUID SLAG PORTION FILLING THE INTERSTICES THEREIN AND FORMING A RELATIVELY THIN LIQUID SURFACE LAYER THEREON; ALLOWING SAID LIQUID SURFACE LAYER TO COOL AND SOLIDIFY, THUS FORMING A SOLID LAYER OF SAID FIRST AND ADDITIONAL PORTION OF LIQUID SLAG; REPEATING SAID STEPS OF BREAKING UP THE ENTIRE SOLID LAYER, LEVELLING THE THUS BROKEN UP LAYER, SPRAYING OF THE SAME, POURING OF ADDITIONAL LIQUID SLAG, AND ALLOWING THE SAME TO COOL, UNTIL A SOLID LAYER OF THE DESIRED FINAL THICKNESS IS OBTAINED; AND BREAKING UP SAID SOLID LAYER OF DESIRED FINAL THICKNESS, WHEREBY A DENSE PARTICULATE MIXTURE SUBSTANTIALLY FREE OF CAVITIES IS OBTAINED.