How to determine the cement content required to stabilize a given soil

Tests required in materials proposed for soil-cement stabilization include:

1. Liquid limit test (for classification)
2. Plasticity test (for classification)
3. Grading tests (for classification)
4. Density/moisture content compaction test (to determine suitable Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) for the California Bearing Ration (CBR) test)
5. Laboratory CBR test
6. Unconfined Compressive Strength (UCS) test

Procedure to determine the cement content (According to Clause 6229 of General Specifications for Roads and Bridges-Volume II-Revised 1997)

1. Classify the soil based on AASHTO classification (using tests a – c above).
2. Perform British Standard (B.S.) compaction on the soil to obtain MDD and OMC using the middle cement content applicable to the soil (see Table below).
3. Mould the CBR and UCS specimens to this MDD and OMC.
4. Establish relationship between cement content versus CBR and UCS for soaked and unsoaked specimens.
5. Mould 3 CBR and 6 UCS specimens at each cement content, with a minimum of 3 cement contents eg (A-2 soil: 3%, 5% and 6%).
6. Wax and cure all specimen for 6 days (except 3 UCS) specimens at each cement content which should be cured for 7 days and tested without soaking.
7. Test all CBR specimen and the UCS specimens at each cement content after 24 hours soaking by complete immersion in water and allowed to drain for 15 minutes.
8. Plot graphs of cement content versus CBR (soaked) and cement contents versus UCS (soaked and unsoaked)
9. Establish the required cement content at 180% CBR for site mix or 160% CBR for plant mix and the corresponding values of UCS (soaked and unsoaked) for quality control in the field.

Note: Heavy clay soils ranging from A – 5 to A – 7 should be avoided where practicable.

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