Lime

To stabilize soil and generate long-term strength gain lime is added to reactive soil, to cause a pozzolanic reaction. The reaction between the lime and soil produces stable calcium silicate hydrates and calcium aluminate hydrates. The calcium from the lime reacts with aluminates and silicates solubilized from the clay. The full-term pozzolanic reaction can continue for a very long period of time – even decades—as long as enough lime is present and the pH remains high (above 10). As a result, lime treatment can produce high and long-lasting strength gains. The key to pozzolanic reactivity and stabilization is a reactive soil, a good mix design protocol, and reliable construction practices.

Benefits of soil stabilization include:

  • Substantial increase in resilient modulus values (by a factor of 10 or more in many cases)
  • Substantial improvements in shear strength (by a factor of 20 or more in some cases)
  • Continued strength gain with time, even after periods of environmental or load damage (autogenous healing)

How Does It Work?

Lime stabilization is not a complex process and is easy to carry out. Developing a proper mix design and testing is the first step. In-place mixing is used to add the appropriate amount of lime to the soil, mixing it to an appropriate depth. Pulverization and mixing is used to thoroughly combine the lime and soil. Heavy clay soils will typically require preliminary mixing, followed by 24 to 48 hours (or more) of moist curing and final mixing. For maximum development of strength and durability, proper compaction is necessary. Proper curing is also important. If sulfates are present at levels greater than 0.3 percent, special procedures are required.