The effect of different aggregate gradations on permeability of open-graded asphalt concrete

What is it about?

Three gradation types A, B, and C were selected in line with ASTM D 7064. Each gradation was divided into fine, intermediate, and coarse gradations to find the extent to which permeability is affected by the difference in the gradation of aggregates within a single gradation. Marshall design method was used to prepare the specimens. An optimum asphalt content of 5.4% was found and used based on the results of air voids content, abrasion loss value, drain down, and permeability. The total number of the prepared specimens are (72) for all gradations. The results indicated that the permeability decreased from coarse to fine gradation for each type of (Mix A, Mix B, and Mix C). It was noted that the upper and lower values of permeability of Mix A of coarse gradation are 677.87 and 612.45. while the upper and lower permeability values for Mix A of intermediate gradation are 380.17 and 332.78 and for Mix A of fine gradation are 235.79 and 174.56 respectively. For Mix B the upper and lower values of permeability of coarse gradation are 628.3 and 544.86. While the upper and lower permeability values for Mix B of intermediate gradation are 290.1 and 265.72 and for Mix B of fine gradation are 245.81 and 193.76 respectively. Regarding Mix C, the upper and lower values of permeability of coarse gradation are 535 and 388.97. While the upper and lower permeability values for Mix C of intermediate gradation are 327.7 and 275.22 and for Mix C of fine gradation are 231.8 and 248.3 respectively.

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Why is it important?

The research specifically aims to study the effect of air voids content on OGFC permeability due to the use of different aggregate gradations and to identify the graphical relationship between permeability and air voids to facilitate the process of estimating the permeability of each air content during the design of open-graded mixtures.

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