Practical recommendations are made for recycling asphalt pavements by (a) use of selected reclaiming agents to restore durability and consistency to the aged asphalt, and (b) application of a rational mix design. Satisfactory reclaiming agents are characterized as (a) being fully compatible with the broadest range of aged asphalts, (b) providing durability to the aged asphalts, (c) being capable of producing a reclaimed asphalt within paving-grade consistency, and (d) assuring good wetting and thorough mixing. Interim specifications are proposed for reclaiming agents fulfilling these requirements. The basic information needed for a rational design is discussed and identified as follows: (a) gradation of the aggregate in the salvaged pavement, (b) asphalt content of the old pavement, (c) consistency of the extracted asphalt, (d) asphalt demand of the aggregate, and (e) desired consistency of the asphalt in the recycled pavement. A simple formula and two nomographs are presented as aids for the design engineer.

No abstract

No abstract

No abstract

Rubble-mound breakwaters are used extensively throughout the world to provide protection from the destructive forces of storm waves for harbor and port facilities. In some locations, a proposed rubble-mound breakwater may be subject to attack by waves of such magnitude that quarrystone of adequate size to provide economic construction of a stable breakwater is not available. Under these circumstances, it is required that the protective cover layer consist of specially shaped concrete armor units. In 1966, Merrifield and Zwamborn (1) introduced a new shape of armor unit, the dolos (Figure 1) which was acclaimed to have much higher stability characteristics than any existing armor unit. Site-specific model tests conducted at the U. S. Army Engineer Waterways Experiment Station (WES) by Davidson (2); Carver (3); Bottin, Chatham, and Carver (4): and Carver and Davidson (5) have shown dolos to exhibit an excellent stability response when exposed to breaking wave conditions. Comprehensive stability tests of dolos also have been conducted at WES by Carver and Davidson (6) for a wide range of nonbreaking wave conditions. These tests used randomly placed dolosse with a first underlayer stone weight of W /5 and a density of units per given area (N/A) equal to 0.83 V~2'3, i!e., n=2, k =0.94, and P=56 percent. It was concluded from this study that the stability response of dolos can be adequately predicted by the Hudson Stability Equation for the range of wave conditions investigated. Their data indicated an average stability coefficient (K) of 33 for dolosse use in a nonbreaking nonovertopping wave environment. Based on the lower limit scatter of their data, a K of 31 was approved for design.