After 40 years in this industry, including more than 26 years with TxDOT and a decade as a consulting engineer, I’ve investigated a lot of pavement failures. Almost every one of them traced back to the same root causes: design, materials, and construction.
I like to call it the three-legged stool. A stool only works when all three legs are the same length. Shorten one, and the whole thing goes unstable. I’ve found the same holds true on every subgrade project I’ve ever worked on — and really, on any type of roadway construction.
Phase 1: Design
Design is the first and most critical phase. Without a sound design, nothing else compensates.
For subgrade stabilization, that starts with a geotechnical investigation to understand what native materials you’re working with before you decide on a stabilizer type, a percentage, or a placement depth. The investigation tells you whether stabilization is even needed — and if it is, exactly what’s required.
Drainage is equally important and often overlooked. Even a well-specified lime treatment at the correct depth and percentage can fail if the pavement system doesn’t manage water properly. Water getting beneath a stabilized subgrade undermines the foundation regardless of how well the other two phases were executed.
Phase 2: Materials
Once the design is established, the materials phase is about making sure what goes into the ground matches what was specified.
In Texas, TxDOT’s Materials Producer List (MPL) is a reliable starting point for lime. Sourcing from an approved supplier gives you reasonable confidence the material meets specification. But the MPL doesn’t guarantee the lime was applied at the right percentage or to the right depth — those decisions come from the design. No approved supplier list compensates for a design that didn’t define them correctly.
This applies across stabilizer types. Whether the project calls for lime, cement, or something else, material quality is only one variable. It has to be the right material, at the right rate, placed correctly.
Phase 3: Construction
Construction is where designs and materials either get realized or get undermined. I’ve seen projects with sound designs and proper materials still fail because the construction phase wasn’t executed correctly. Common problems include mixing too deep or not deep enough, insufficient water during the mellowing process, and failure to follow established procedures.
Two principles I come back to constantly on the construction side:
- What gets measured gets done. In-place density, mixing depth, lime percentage — if these are critical to the project’s success, they need to be in the specifications and actively measured during construction.
- If you expect it, inspect it. If a requirement matters enough to specify, it matters enough to verify in the field.
Mixing It All Together…
Whether you’re planning a new project or conducting a forensic investigation on a failed one, this framework gives you a structured place to start. In my experience, virtually every failure traces back to at least one of these three phases.
For a deeper look at how these principles apply specifically to lime stabilization — including how to determine the right lime percentage, mixing depth, and water content — click here. To learn more about lime stabilization or to reach me directly, email dalerand@limetexas.org.
About the Author
Dale Rand, Executive Director
Dale Rand, P.E. is the Executive Director of the Lime Association of Texas. With more than 40 years in the industry — including over 25 years with TxDOT and a decade at Atlas Technical Consultants — Dale has designed more than 300 hot mix asphalt mixtures and has seen firsthand what lime can do when it’s used correctly, and what happens when it isn’t. He joined Lime Association of Texas in 2023 with a simple vision: make this a practical, trustworthy resource for engineers, contractors, and anyone working with lime in Texas.
