In the united states, approximately 93% of hard-surfaced roads are surfaced with asphaltic concrete mixtures. These mixtures are a combination of high-quality aggregates and an asphalt cement. The aggregates must be able to resist abrasion and degradation during manufacturing, placing, and compacting. For decades, researchers studied the resistance of aggregates to abrasion and impact. The most commontest used to measure this resistance is the los angeles (la) abrasion test. The la test has been used for many years throughout the united states and has a local history. From this history, acceptance specifications have been written. The objectives were to determine (a)the extent of the use of la values in the united states; (b) any discernible difference in the level of performance (i.E., Strengths) between laboratory-prepared marshall specimens using different aggregate sources; and (c) the level of degradation of extracted aggregates. In general, the majority of states use the la abrasion test for writing specifications. In some cases, there were not significant differences between the dry and wet indirect tensile strength and resilient modulus values of specimens prepared with aggregates with low la values versus specimens prepared with aggregates with high la values. The gradation analysis of the recovered aggregates indicated that no major degradation of aggregates occurred with various compactive efforts. This paper appears in transportation research record no. 1301, Factors affecting properties and performance of pavements and bridges 1991.
Samenvatting