RECYCLED ASPHALT MIXED WITH NEW PERFORMS BETTER THAN NEW

This report describes the results of a study on the Osaka-Uchikanjyosen Road where an old asphalt mixture was mixed with new material at a rate of 20, 30 and 40 per cent. Details are given of the construction and condition of the old pavement and of the design and construction of the repaved sections. Extensive tests for quality control were carried out at the plant and on site. Details are given of the aggregate grading and extraction tests results. The temperature control appeared to be the most important factor in the laying of the material. Heating of the aggregate was proportional to the ratio of old to new asphalt in the mixture so that it was always at 180 deg C when leaving the plant. The density of asphalt mixture specimens was found to be similar to that of new asphalt. Marshall tests, wheel tracking tests, and dynamic bending tests showed that the mixture was supeior to the new asphalt. The number of load cycles to failure increased with an increased proportion of old asphalt in the mixture. (TRRL)