LDFC stands for Low Density Foamed Concrete, which is just a fancy name for cellular concrete. Cellular concrete is a type of controlled low strength material (CLSM). CLSM generally refers to flowable fill or mix designs specifically formulated for relatively low, but predictable, strengths.  The “foamed” in LDFC refers to the preformed cellular concrete foam used to generate the material.  Instead of sand and stone aggregate, the Low Density Controlled Low Strength Material has uniformly-distributed air bubbles.  This lowers unit weight significantly.  Foaming is done either through truck batching or continuous generation.

placing ldfc to abandon a box culvert

Abandoning a box culvert using LDFC

Types of LDFC

LDFC can be either pervious or non-pervious.  We generate non-pervious material using Aerlite preformed cellular concrete foam.  We use Aquaerix preformed cellular concrete foam to generate pervious material.  Both types start with the same base 0.5 water : cement ratio slurry.

Uses for LDFC

The primary driver of Low Density Foamed Concrete use instead of standard CLSM is load reduction.  Applications range from abandoning pipes to void filling below bridge abutments, reducing loads on underground utilities and reducing settlement without the use of deep foundations.

Typical Mix Designs

Cellular concrete typically ranges from 20lb/cuft wet cast density up to around 70lb/cuft.  These densities provide strengths from around 50psi to greater than 1,000psi.  Density is effectively infinitely variable within that range.  There’s a relatively linear relationship between density and compressive strength.

Relatively common mixes are 20PCF, 30PCF and 70PCF.  20PCF wet cast density is the go-to mix design for maximum load reduction.  Pervious LDFC is used in areas where low unit weights are required and buoyancy can’t be balanced by overburden.  30PCF is a relatively common mix for pipe abandonments, annular space grouting and other utility-related work.  

70PCF material is also used to provide weight reduction compared to traditional CLSM or other fill materials when buoyancy must be absolutely avoided.  Pervious LDFC must be protected from adjacent soils with geotextile fabric.   CJGeo uses 65PCF wet cast density material in cases where pervious cellular concrete can’t be used, and buoyancy is a concern.  1,000psi compressive strength is required for some annular space grouting work.  CJGeo uses 70PCF west cast density material to meet this specification.

LDFC Project Profiles