A Field and Laboratory Examination of Weathering Effects on Petroleum and Blended Petroleum-Natural Asphalts in Paving Mixtures

The relative merits of various asphalts and asphaltic materials have been the subject of considerable controversy almost from the beginning of flexible pavement construction in this country. In this early period petroleum asphalt had not yet entered the picture and controversy centered about naturally occurring products such as Trinidad natural asphalt and impregnated stones. In 1876 Congress directed that comparative service tests be made on a rock asphalt* and a sheet asphalt containing Trinidad natural asphalt. The sheet asphalt was considered the more successful of these and thus Trinidad natural asphalt became firmly established as a paving material in this country. Its position remained unchallenged until a rapidly enlarging oil industry made available cheaper asphalt. Since then considerable effort has gone into both laboratory studies and comparative field installations to examine the relative merits of the two materials. These studies have produced interesting but not conclusive results and the trend has constantly been toward the cheaper and more readily available petroleum asphalts