Reflective crack relief pavement interlayer with improved load bearing capacity and method for designing interlayer
A highly strain tolerant, substantially moisture impermeable, reflective crack relief interlayer is provided. The interlayer includes a polymer modified asphalt binder mixed with a dense fine aggregate mixture containing a substantial amount of manufactured sand. The interlayer mix is designed using a fatigue test and a stability test. Preferably, a hot mix asphalt overlay that is compatible with the interlayer, as well as the demands of local traffic and climate, is placed over the interlayer so that a protected, smooth paved surface is provided. The interlayer may delay the first appearance of cracks and the severity of cracks for several years compared with traditional hot mix overlays and extend pavement service life.
1. An interlayer for placement on a paved surface, comprising a mixture of:
aggregate comprised of no more than about 15% by weight natural sand, wherein said aggregate that is not natural sand is manufactured sand with an angularity of at least 38%, and wherein said aggregate is comprised of about 80% by weight to about 100% by weight aggregate having a sieve size of less than about 4.75 mm; and
an asphalt binder, wherein said interlayer has a Hveem Stability at 60° C. and 50 gyrations of at least about 22 and a Flexural Beam Fatigue of at least about 50,000 cycles at 2000 microstrains, 10 Hz, 3.0±2.0% air voids, at 0-30° C.;
where the mixture is covered with an asphalt overlay.
2. The interlayer of claim 1 , wherein said asphalt binder is a polymer modified asphalt binder.
3. The interlayer of claim 1 , wherein said interlayer is about 0.5 to 2 inches thick on a paved surface.
4. The interlayer of claim 1 , wherein said binder is chosen based on the temperature associated with the regional climate.
5. The interlayer of claim 1 , wherein said binder is chosen from a Type I binder for Northern Type I climates, a Type II Binder for Central Type II climates, and a Type III binder for Southern Type III climates.
6. The interlayer of claim 1 , wherein said interlayer is substantially impermeable.
7. The interlayer of claim 1 , wherein said aggregate is comprised of no more than about 10% by weight natural sand.
8. The interlayer of claim 1 , wherein said aggregate is comprised of no more than about 5% weight natural sand.
9. The interlayer of claim 1 , wherein said aggregate is comprised of about 40% by weight to about 70% by weight aggregate having a sieve size of less than about 1.18 mm.