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Stem Wall Backfilling With Cellular Concrete

The Job

This work was associated with the construction of a new academic building at a school in Lynchburg, Virginia.

The Challenge

Due to a sloped site, there was up to an 8′ difference in elevation between the existing ground and the desired finish floor elevation. Various options for filling the CMU stem walls included soil, aggregates and EPS foam blocks. EPS foam blocks were chosen to reduce loads on the footings, which would have required deep foundations in the case of soil or aggregate backfilling.

Due to the extensive sub-slab plumbing, the design called for EPS blocks cut to fit the curved walls & uneven ground profile, and then backfilled with 18″ of stone dust, to allow for the plumbers to dig and install the plumbing.

The Solution

CJGeo proposed installing 23lb/cuft cellular concrete to speed up the installation, reduce supply chain risks, and reduce the loads applied to the foundations and underlying soil.

CJGeo placed 1914CY of cellular concrete over three days onsite. All material was walkable within 12 hours, and the project saved approximately 3 weeks relative to the original design’s timeframe.

The cellular concrete was brought all the way to the bottom of the 6″ stone layer below the slab, and the plumbers were then able to excavate through the cellular concrete with a mini excavator and hand tools to install the plumbing, and the trenches were backfilled with 57 stone.

The total load using cellular concrete was reduced by approximately 120lbs/sqft relative to the EPS/stone dust backfill design.

Precast Lagging Wall Lateral Load Reduction

The Job

This work as associated with the replacement of Scaife Hall, at Carnegie Mellon University, in Pittsuburgh, Pennsylvania.

The Challenge

The H-pile and precast lagging wall was situated at the top of a steep slope, which had a Class I railroad at the base. Because of site constraints, an HDPE stormwater detention structure was situated within the fill area, along with extensive stormwater pipes and manholes.

In order to optimize the drilled shafts for the H-piles by reducing the lateral loads, the designer sought a lightweight, permeable backfill material that would not apply lateral loads once in place.

The Solution

CJGeo proposed 20lb/cuft permeable cellular concrete to minimize lateral loading on the wall during construction, buoyancy of of the stormwater system components, and ensure a free draining material.

Because the material is permeable (modified ASTM D-2434 2.0cm/sec), it is freely draining and reduces hydrostatic loads on adjacent structures.

620 cubic yards of lightweight backfill were placed over two mobilizations.