Performance of a Trial Section Reconstructed Using Cellular Concrete in the City of Edmonton

Over the past two decades, roadways in several residential neighborhoods within northeast
Edmonton have experienced significant early structural failures. Failures were so severe in
some cases that heavy vehicles (i.e. garbage and fire trucks) were not able to access some
affected streets. These failures occurred as a result of the presence of subgrade soils that are
susceptible to water softening, poor subgrade drainage, and additional water drainage from
private sump pumps. As a consequence, The City of Edmonton has established an extensive
roads program that conducts annual replacement of roadways in northeast Edmonton.

As part of the above-noted roads replacement program, two trial sections were selected by The
City of Edmonton to be reconstructed in 2009. These sections were located in adjacent cul-desacs
to provide for comparison of performance between two constructions methods. One
section was constructed using a traditional granular section, and the other used lightweight
cellular concrete (LCC) as a subbase material. LCC is a construction material formed by mixing a
cement and water slurry with a pre-formed foam, similar in consistency to shaving cream. The
material is produced onsite and pumped into place using proprietary pumping equipment that
may be setup several hundred meters from the pour area. The LCC supplied for the abovenoted
projects had a wet (cast) density of 475 kg/m3, which is approximately one-fifth the
density of typical granular subbase. As a result of the high percentage of air bubbles
(approximately 72% by volume), the material also has insulating qualities that, depending on
the applied thickness, can reduce or prevent frost heave and subsequent thaw weakening of
subgrade soils.

Load-deflection data was gathered on the trial sections for both pre and post construction
conditions using The City of Edmonton’s Dynaflect system. The City performed additional
testing in 2016 using both its Dynaflect and Falling Weight Deflectometer systems. The results
of this testing are presented in this paper. Since reconstruction, no maintenance activities have
been required for either the granular or cellular concrete trial sections.