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LD-CLSM stands for Low Density Controlled Low Strength Material, which is just a fancy name for cellular concrete. CLSM, or Controlled Low Strength Material, generally refers to flowable fill or mix designs specifically formulated for relatively low, but predictable, strengths. The preformed foam used to generate cellular concrete facilitates the Low Density characteristics of LD-CLSM. Instead of sand and stone aggregate, the Low Density Controlled Low Strength Material has uniformly-distributed air bubbles. This lowers unit weight significantly.

Types of LD-CLSM

LD-CLSM can be either pervious or non-pervious. We generate non-pervious using Aerlite preformed cellular concrete foam. We use Aquaerix preformed cellular concrete foam to generate pervious material.

Uses for LD-CLSM

The primary driver of Low Density Controlled Strength Material 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, with 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 LD-CLSM 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 LD-CLSM 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.