Foundation, Concrete and Earthquake Engineering

Controlled Low-Strength Material to Support Foundation (IBC)

Dear reader this is relatively new term in this blog, controlled low-strength material; this are used to establish structural fill/backfill of trench. In United States there have widespread use of it as foundation backfill. The special attention is for backfilling for utility and storm drainage on highway projects.

Dear reader our concern is here foundation backfill, we will have just introductory idea about controlled low-strength material. This will be expressed as CSLM for convenient of discussion.
Foundation backfilling by Controlled low strength material
This is produced by mixing cement, aggregate, fly ash and essentially water. So we can take it as concrete; the difference is very low strength which is at best 1200 psi and mostly less than that value. We know ordinary concrete have strength around 3000 psi.

Due to very low strength, we will not choose it as supporting material for building, bridges etc. rather we will go for backfilling as discussed earlier. The important parameter is it has greater flowability than normal concrete.

International building code provides us some geotechnical investigation required for using this materials as foundation backfilling material. Dear reader, yes, we are talking about shallow foundation and following are the requirements:

  1. Specification to prepare site before placing controlled low strength material should be provided in geotechnical investigation.

  2. Specification for CLSM

  3. Field or laboratory test methods for determining bearing capacity, in other word compressive strength of CLSM

  4. Test methods to approve CLSM in field

  5. Frequency and number of in-situ tests, to determine acceptance according to Item 4 (above).

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