Backfilling and Compaction
When all the units comprising a section of wall at a single elevation have been placed, aligned and leveled, fill the gaps between the units with a clean crushed rock material at least ½” – ¾” in size. Use this same material behind the back of the block to a depth of at least 1’ or as otherwise indicated in the final engineered drawings. This material serves as a “French drain” to relieve water build-up and also, because it is self-compacting, it relieves installers from having to operate compaction equipment close to the back of the units.
At times, a filter fabric may be specified behind the drainage aggregate material. This helps keep the drainage zone clean and free from sedimentation. If present, wrap the fabric forward over the drainage aggregate as the other backfill material is placed.
When drain tile is used, it should be located as shown in the plans or drawings. Generally, the drain tile runs along the back of the wall and is at the bottom of the drainage aggregate zone at an elevation at or above the bottom finished grade level. Drain tile should “daylight” at least every 50’ along the length as well as at every low point in the wall.
Place the specified backfill material and thoroughly compact material in 8” lifts. Backfill material should be compacted to 95% of standard proctor. Improper or inadequate compaction is a primary source of contractor-caused wall failures. Close attention should be paid to changes in consistency and moisture content of all backfill material. Use the proper type of compaction equipment. Sandy or gravelly materials respond best to plate compaction equipment and clayey materials usually should be “kneaded” by using a hand-operated “jumping jack” or “sheep’s foot “. Heavy-duty compaction equipment should be kept a minimum of 5’ from the back of the ReCon Wall to avoid wall rotation.
Placing Additional Courses
Prior to placing successive courses, sweep and keep clean any backfill material from the top of the ReCon units and make sure that all voids are filled with the proper drainage material. Place the next course in a running bond pattern or as otherwise shown on the engineer’s detailed wall elevation plan. Set the upper unit and slide it forward until its bottom “groove” is in full contact with the bottom unit’s “tongue”. Check and adjust level at every course elevation. If shimming is required, use a material such as an asphalt shingle and cover as much of the “low” surface area as possible to achieve the desired result.