BEHIND THE SHIFT TO PERMEABLE BASES

A different design approach to pavement bases is emerging. Several states are now using open-graded permeable bases which allow moisture to rapidly drain through the base and out from beneath the pavement structure. Permeable bases normally consist of open-graded crushed aggregate with little or no fines. A longitudinal edge-drain system removes the moisture that collects in the permeable base. Typical permeable base designs and their construction methods are presented in this article. This year, 10 states will build permeable bases. Seven of them generally use untreated, or unbound permeable base, but three use a treated or bound open-graded aggregate base.