Field observations and test results show that common construction operations to place and compact unbound granular base materials contribute to spatial variation in the in-situ permeability and fines content. These variations may undermine pavement thickness design assumptions and lead to poor pavement performance. To assure the effectiveness of unbound granular base materials after they have been spread and compacted, simple, rapid, in-situ permeability testing and end-result specifications are needed. This paper describes a newly developed Air Permeameter Test (APT) device for rapid measurement of in-situ permeability. Testing at several project sites revealed a strong spatial correlation between fines content (passing No. 200 sieve) and in-situ permeability for the final compacted base layer. Further, statistical distribution analysis of test results and its significance in pavement thickness design are presented. Finally, an example calculation is provided which demonstrated how rapid measurement of permeability using the APT can provide better insights into what level of design assumptions are being achieved in field.
Samenvatting