Flowable fill

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University of New Brunswick


Soil compaction is a very time consuming and expensive operation. Traditionally, the area is backfilled in approximately three equal layers of about 200 millimetre thickness using granular fill with each layer being compacted. Sometimes it is difficult to meet the specified compaction levels so the work is accepted at an inferior standard which leads to eventual repairs. Therefore, engineers attempted to find an alternative to this procedure and it has become known as flowable fill or controlled low-strength concrete. Flowable fill is a self-levelling cementitious material which is normally supplied by a ready-mix company and in its hardened state provides a volumetrically stable and uniform material. This material can be placed using a ready-mix truck, pump or concrete bucket. Originally flowable fill was a mixture of Portland cement, fly ash, fine aggregates and an excess amount of water. Today, other products have been introduced to reduce the amount of water added to the mixture. One product is Darafill and is manufactured by W.R. Grace and the other is Rheofill produced by Master Builders. These products may either be added in the field or at the ready-mix plant. The mixtures are all pretested to meet the requirements of the site. Flowable fill is currently being used throughout Europe and in some parts of United States. They have used the material to backfill bridge abutments, culverts and trenches; as fill for embankments, bases and sub-bases; bedding for slabs and pipes; fill for caissons and piles and as fill for abandoned storage tanks, shafts and tunnels. Therefore, the objective of this report was to focus on the benefits of using flowable fill in Atlantic Canada.