Lute and Rake Use
Using a lute.
Lute with a smooth edge (left side) and a rake edge (right side).
Bumping a transverse joint
Sequence (from top to bottom) for bumping a HMA joint.
Once HMA is placed by hand it should be prepared for compaction by spreading out and smoothing the surface either by rake or lute (see Image). A rake has individual tongs (like a garden rake) and is generally used to move HMA on the coarser or bottom layers. A lute has a smooth surface and is often used with finer mixes or on the final lift surface. Sometimes one tool can serve both functions (see Image). Rakes and lutes can also be used to push the edge of an HMA lift off an already finished surface; called “bumping”. Bumping is often used on longitudinal joints to build up a small ridge of mix for the roller to compact (see Image). On some jobs, where joints are cut back after paving, handwork is not needed on the joint because it will later be removed. Other lute and rake precautions are:
- Check the handworked surface with a straightedge or template before rolling to ensure uniformity.
- Minimize working time with the lute and/or rake. Excessive surface working can separate coarse and fine aggregate (segregation) leading to a rougher surface texture.
- Coarse segregated materials resulting from handwork should be removed from the HMA mat entirely along with any other excess material.
- Account for compaction when placing HMA in its loose state. As a general rule-of-thumb HMA compacts about ¼ to ⅜-inch for every inch of mat thickness. Therefore, if the final mat thickness of 1 inch is desired, place about 1¼ – 1⅜ inches of loose HMA. Sometimes this is referred to as “fluffing up” the mix.
