"Cheaper" Stabilization: Cement or Lime?

By: Matthew W. Singel, PE
​An often-asked question when discussing soil stabilizing additives is whether cement or lime is the cheaper option.  This answer goes much deeper than the current price-per-ton comparison.  When asked, this question, I often answer, “that depends”, followed by a series of questions that might include:

• Do you know the soil conditions on your project site?
• Is your goal to achieve a stiff working platform during construction or a long-term contributor to the pavement structure?
• Where is the project located?
• Does speed of construction affect cost?
• What are the acceptance criteria for cement and lime in the construction specifications?

Simply stated, there are many variables that exist from one project site to another and from one contract to another.  The cost for the stabilizing additive, its transport (distance from the project), water availability (yes, they have different water requirements to hydrate), need to quickly open the pavement to traffic, etc., can vary from one project to another.  In fact, cement and lime often require different concentrations to meet the specified criteria.  And cement is placed and compacted in a single day's operation, while lime must mellow, usually for 72 hours before compaction. Also, lime is less effective in low-plasticity soils and is inappropriate in non-plastic soils.  Cement is less effective in high-plasticity soils (where PI is over 40) but at these high-plasticity levels, a combined lime/cement stabilization can produce a superior subgrade compared to a single stabilizer. However, both stabilizers can produce desired results over a wide range of plasticities (approximately between PI of 15 to 40). 
Ultimately, the in-place cost per square yard or cubic yard is where the actual determination lies.  The project specification acceptance criteria might include target density, 7-day unconfined compressive strengths, PI reduction, application rates of additives as determined from a mix design, and stiffness readings to name a few.  Overall project requirements may have time or re-trafficing constraints.
​Hopefully, you now see that the initial question of “…which is cheaper…” does not have a simple answer.  The better question might be, "Which stabilizer--or combination thereof--can minimize the entire project cost, and ensure appropriate performance?"
"This blog was previously posted in the Cement Council of Texas' "Texas Cement and Concrete Blog" (now inactive) and was carried forward to the current blog ("Cementx Pavement Blog") as it contains content that may be of interest to the reader".