Implementation Plan for Design and Use of Flowable Backfills by PennDOT for Highway and Bridge Construction

摘要

The report presents the implementation plan for the design and use of flowable backfills on PennDOT projects. Flowable backfills are controlled low strength materials (CLSM) composed of cement, fly ash, water and sometimes coarse aggregate and/or admixtures. They are used to backfill utility trenches, around culverts, behind bridge abutments and to fill abandoned pipes, mine voids, and around underground structures and other earthwork traditionally constructed by placing and compacting selected soils. Advantages are that flowable backfills require no compaction, they flow into irregular cavities, they provide uniform support to pipes, they cure rapidly, and they are relatively incompressible after curing. The implementation plan presents specifications for use of flowable backfills, a list of potential fly ash suppliers, and recommendations for training, long term evaluations, and additions to the Design Manual. The research reports and field demonstrations that formed the basis for the plan are referenced.