Method Statement for using Controlled low strength material (CLSM)

Dec 31, 2018
4
4
BANGALORE
Providing and laying CLSM (Concrete Low Strength Material) for filling the voids in the strata below the excavated formation. The composition of the CLSM shall be 5% OPC Cement; 15% flyash, 70% excavated good soil passing 4.75mm sieve, 10% Sand and about 350 ltrs of water so as to achieve a free-flowing mixture which gives a compressive strength of 3 to 5 N /mm2. The mix of CLSM thus obtained shall be poured over the formation level such that the flowing CLSM permeates into the voids augmenting the densification of the soil strata. As the CLSM is poured, the surface shall also be rodded with a sharp pointed tool for facilitating the flow into the interstices. The CLSM shall be poured in sufficient quantity until the pores/voids cease to take any further pour and there shall be a standing layer of CLSM of about 75 -100mm thick above indicating the job is completed . After the work is over, the formation level shall be left intact for three to four days for facilitating the CLSM to gain sufficient strength for taking up further substructure works. Curing with water on the surface as done for regular concrete shall be carried out.
 

HockeyPuck

Active Member
Feb 3, 2019
119
90
Chicago, Illinois (USA)
Hi
Can any share the Method Statement for using Controlled low strength material (CLSM) to be used as back fill.
I say it often on my posts here at Civil4M - It's interesting to see how engineers in other countries apply engineering principles, materials, etc.

In Mr. maheshsavandappa post, he indicates that he has used excavated soil as a component of a CLSM: I must say, I've never heard of that. In the US, CLSM mixtures I've used have followed a mix design formula somewhere along these lines:

Portland Cement - 50 lbs
Fly Ash (Class C or F) - 125 lbs
Fine Aggregate/Sand (SSD) - 2900 lbs
Water - 50-65 gallons

We primarily use these mixes for gravity void filling of open trenches or excavations where compacting aggregate may be challenging. We have used them for filling abandoned sewers, but you have to make sure that the sewer you are filling has enough slope for the CLSM to flow by gravity. CLSM mixes are not pumpable, like a grout, due to the amount of line friction that the fine aggregate causes - I've seen a Contractor blow the lines off of a grout pump because of this.

A mix of this type will have a compressive strength range between 30 - 150 psi and a Dynamic Cone Penetration rate at 3 days of around 1.5 inches/blow.
Hope this helps - Cheers!!
 
  • Like
Reactions: ambrishnitk

ambrishnitk

Newbie
Dec 25, 2019
5
2
Bangalore
I say it often on my posts here at Civil4M - It's interesting to see how engineers in other countries apply engineering principles, materials, etc.

In Mr. maheshsavandappa post, he indicates that he has used excavated soil as a component of a CLSM: I must say, I've never heard of that. In the US, CLSM mixtures I've used have followed a mix design formula somewhere along these lines:

Portland Cement - 50 lbs
Fly Ash (Class C or F) - 125 lbs
Fine Aggregate/Sand (SSD) - 2900 lbs
Water - 50-65 gallons

We primarily use these mixes for gravity void filling of open trenches or excavations where compacting aggregate may be challenging. We have used them for filling abandoned sewers, but you have to make sure that the sewer you are filling has enough slope for the CLSM to flow by gravity. CLSM mixes are not pumpable, like a grout, due to the amount of line friction that the fine aggregate causes - I've seen a Contractor blow the lines off of a grout pump because of this.

A mix of this type will have a compressive strength range between 30 - 150 psi and a Dynamic Cone Penetration rate at 3 days of around 1.5 inches/blow.
Hope this helps - Cheers!!
Thank you so much for the inputs