EDUCATION > Flowable Fills
 
 
Flowable Fill, aka ... CLSM, Controlled Low Strength Material

Aka…Soil Replacement, K-Crete, Lean Mix Backfill, Flowable Mortar, Liquid Dirt, Controlled Density Fill etc…

Controlled Low Strength Material is a mixture of Portland Cement and/or fly ash, aggregates, water, and possibly chemical admixtures that, as the cement hydrates, forms a soil replacement material. CLSM is a self-compacting, flowable, cementitious material that is primarily used as a backfill or structural fill in lieu of compacted fill or as unsuitable native soil. Depending on the amount of water used in the CLSM mixture, it can also be placed as a non-flowable compacted material or as a mortar. (Defined in by American Society for Testing and Materials ASTM)

CLSM/Flowable Fill is not concrete. It is delivered in a ready mix truck just as concrete is, and has some of the same ingredients concrete has, but it is very different.

 
USES BENEFITS
Backfill   Fast
Utitlity Trenches   Economical
Retaining Walls   Eliminates Settlement
Mud Jacking   Shrink Resistant
Float/Footing Support   Non-Corrosive
Pavement   Easily excavatable with proper mix design
Bases   Year round availability & placment
Bridge Conversion   Self-leveling & self-compacting
Erosion Control   Increased worker safety
Pipe Bedding   Can be color coded easily for utility identicication
Sub Base Stabilization   Can vary psi expectatations with mix design
Abandoned Tank Fills   Reduce in place costs-less labor, equipment & time
Sink Hole Fills    
 

Important Questions ....The Right Mix for the Right Project!

  • What is the application?
  • Job location? Where will it be used?
  • What are the surrounding soil conditions?
  • Does it need to be excavated in the future? If so, by hand or by machine?
  • Are there multiple locations to pour from?
  • What is your desired time frame for a workable surface?
  • What is your psi requirement?
  • Is the site accessible for a ready mix truck to drive to it easily?
  • Will it need to be pumped at the site?
  • How do you plan on testing the CLSM?
  • What are the climate conditions?
  • Are there any other requirements?
  • Are you working with in a specification design?

Testing CLSM:

Since CLSM is not concrete, the typical cylinder testing methods for concrete are not appropriate for testing CLSM.  The American Society for Testing and Materials has identified the following as appropriate for CLSM.

ASTM Designation: PS 31-95
Provisional Standard Test Method for Ball Drop on Controlled Low Strength Material to Determine Suitability for Load Application.

ASTM Designation:  PS 30-95
Provisional Standard Practice for Sampling Freshly Mixed Controlled Low Strength Material.

ASTM Designation:  PS 28-95
Provisional Standard Test Method for Flow Consistency of Controlled Low Strength Material.

ASTM Designation:  PS 29-95
Provisional Standard Test Method for Unit Weight, Yield, and Air Content (Gravimetric) of Controlled Low Strength Material

 

Flowable Fill a Self-Leveling Soil Replacement, Provides an Economical & Safe Choice to Filling Trenches
   

Excavatable and Non-excavatable Flowable Fill
 

Flowable Fill “Liquid Dirt” flows into place
 
Two Trial Mix Designs: #1 is more permanent, #2 is excavatable