Laboratory investigation of using foam grout as micro-trench backfilling material in cold regions

Micro-trenching, an innovative method for fiber optic cables installation, involves creating a narrow trench in the road pavement to place a cable or conduit; the trench is normally narrower than 40 mm wide and shallower than 300 mm deep, depending on the size of the used conduit and trencher. After cutting the pavement, the next step is cleaning the area and placing the cable or conduit inside the trench, followed by backfilling. The quality of the backfilling plays an important role in both the sustainability of the installed cable or conduit and the cut pavement; using unsuitable materials or improperly installing cable or conduit can significantly decrease pavement life. The trench dimensions are very small, so for a successful procedure the backfilling material should be self-compacted and flowable enough to penetrate and completely fill the whole trench depth. As it has been investigated before, using traditional backfilling material such as play sand is not appropriate for Canadian cold regions; hence, it is recommended to stabilize the conduit inside the pavement’s granular layer using a material similar to a cement grout. Alternatively, foam grout is a mixture of cement, water, and pre-formed foam; the foam considerably reduces the density of the blend by adding air, which consists of more than 25% of the mix. As a result, using this foam grout technology reduces the amount of cement required significantly and could be a cost effective solution for backfilling. The objective of this paper is to assess foam grout as a backfilling material for micro-trenching in cold climates. For this purpose, foam grout samples were prepared in a laboratory and their compressive strengths before and after several freeze and thaw cycles were investigated. Different mix-proportioning ratios were also studied in an attempt to create a more reliable method and assess variations in compressive strength and cost along with density.


Rios, V.A.V.
Johnson, T.W.
Hashemian, L.

Session title

Testing and Modelling of Road and Embankment Materials


Soils and Materials Standing Committee







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