Lightweight Fill
Been There. Grouted That.™
Permeation grouting is the use of low viscosity grouts to uniformly saturate soil and fill materials to reduce its permeability, increase its stability and/or increase its bearing capacity. This is in contrast with low mobility grouting, which is primarily focused on increasing the density of soils by displacing treated materials.
CJGeo performs most permeation grouting through TAM tubing installed with sonic drilling. Most permeation grouting is done with acrylic grouts, though occasionally colloidal silica or polyurethanes are best suited to the soils being treated.
Uses for Lightweight fill
Axial load reduction
Axial load reduction applications for lightweight fill allow for reducing dead loads over compressible soils and underlying structures. This includes building walls & sites over compressible soils, or over structures such as pipes, tunnels, and basements.
lateral load reduction
Lateral load reduction applications for lightweight fill allow reduce loads on walls and structures to facilitate building more economically. For example, filling between a permanent slope and a wall with 25lb/cuft CJFill-Ultra Lightweight cellular concrete effectively eliminates passive earth pressure after the CJFill has set, which takes just a few hours.
Low density fills are an economical way to reduce or compensate for the loads of a structure. This allows for smaller foundation footprints, reductions in anticipated settlements, and avoidance of expensive deep foundations.
Cellular concrete is a lightweight backfill frequently used for MSE wall backfill to reduce settlement of bridge approaches. Pervious cellular concrete is used for reducing the load on retaining walls. It allows water to freely drain to avoid building up hydrostatic pressure.
Types of lightweight fills
low density cellular concrete
Cellular concrete consists of Portland, water & air bubbles. Occasionally, sand or fly ash is added to cellular concrete mixes to achieve higher densities. However, this also the strength of the material. Densities of cellular concrete start around 16 pounds per cubic foot and increase to around 50 pounds per cubic foot. Bearing capacities start at 50psi and increase to around 950psi for neat mixes. Autoclaved Aerated Concrete is similar to cellular concrete, but isn’t appropriate for mass lightweight fills.
Geotechnical Polyurethane
Geotechnical polyurethanes are rigid cellular plastics, placed as liquids which then expand and cure. Depending on the application, densities are as low as 2.0 pounds per cubic foot, and increase to around 10 pounds per cubic foot. Bearing capacities start at 3,000PSF and increase with density. High density polyurethanes can either be sprayed or poured, depending on the application. Vertical applications are generally sprayed, horizontal applications are typically poured, but may also be sprayed.
Other lightweight fills
Aggregates
There are two broad types of lightweight aggregate; foamed glass, and expanded shale (or clay). Both of these materials are generated in factories or at quarries and shipped to a project site, where they are installed and compacted similarly to traditional unit weight aggregate.
Foamed glass is manufactured from recycled glass burned in furnaces with a foaming agent, and weighs around 25lb/cuft in place. Expanded shale is made by burning shale that then expands, with target densities generally around 65-70lb/cuft.
styrofoam
Styrofoam, or expanded polystyrene (EPS) is a petroleum based foam product that is very lightweight, but manufactured in large blocks and then shipped to sites. On site, it is stacked to build embankments or fill in areas.
While very lightweight, a particular challenge with the use of EPS is that if it comes into contact with gasoline will melt into napalm.
The Advantages
Load reduction
Using lightweight fill materials is one of the surest ways to reduce loads on sensitive structures and soils. Many times, the use of lightweight fill materials can allow net zero load structures to be built.
Reduced costs
Lighter fills often mean faster placements, and optimized (or even avoidance of) deep foundations and wall designs. Lightweight embankments that remove the need to purchasing additional right-of-way on transportation projects can be exceptionally cost effective.
Increase Speed
Both lightweight fill materials that CJGeo installs are self-consolidating. This means that they’re pumped or sprayed into place, at up to 200cy/hour, without the need for compaction, and the time it takes.