Cold mix, cold laid semi-flexible Grouted Macadams, mix design and properties

摘要

Grouted Macadams consist of a single sized porous asphalt layer laid with a traditional asphalt paver typically to a thickness of up to 60mm. The porous asphalt skeleton is designed to achieve a high void content (28―32%) whilst maintaining a thick bitumen coating on the aggregate particles. The hot asphalt is rolled using a steel wheeled compactor without vibration. As soon as the bituminous mixture has cooled, the voids in the porous asphalt mixture can be filled with the selected fluid grout (cementitious slurry). The Grouted Macadam sections can normally be opened to vehicular traffic 24 h after the voids have been filled with the cementitious grout. Grouted Macadams thus combine the best qualities of concrete and asphalt pavements, namely the flexibility and freedom from joints that characterize asphalt and the high static bearing capacity and wear resistance of concrete. The aim of this investigation was to establish techniques that would reduce the initial cost of Grouted Macadams whilst maintaining their excellent mechanical and performance properties. Two techniques were established; the first was to redesign the conventional hot mix, hot laid porous asphalt skeleton using bituminous emulsions, thus creating a cold mixed, cold laid porous asphalt skeleton suitable for filling with a cementitious grout. A range of tests including: compressive strength, drying shrinkage, indirect tensile stiffness and dynamic creep tests were carried out on these cold mixes and the results compared with a conventional limestone Grouted Macadam. The second technique progresses even further by investigating the potential for utilizing substandard dolomitic aggregates as an alternative to the conventional limestone aggregates in Grouted Macadams, as a cold mixed, cold laid porous asphalt.