Building Roads That Last: Why Cement-Treated Base and Stabilized Subgrade Are Game Changers for Long-Lasting Pavements

Consider the benefits of cement stabilization:

Versus the weaknesses of non-stabilized ordinary compaction:

In 2015, the University of California Pavement Research Center (UCPRC) studied the performance of different Full Depth Reclamation (FDR) Methods.

This study evaluated the rutting depth under accelerated traffic loadings of 4 different pavement strategies:

1. With a rutting depth of .51 inches under 0.49 million ESALs, was a non-stabilized base with a 2.36 inches of hot mix pavement surface.
2. With a rutting depth of .51 inches under 21.4 million ESALs, was a non-stabilized base with 4.72 inches of hot mix asphalt pavement surface.
3. With a rutting depth of .23 inches under 34.0 million ESALs, was a 3 percent foamed asphalt with 1.5 percent cement with 2.36 inches of hot mix asphalt pavement surface. 
4. The strategy with the best performance, with a rutting depth of .08 inches under 43.0 million ESALs, was a 5 percent cement-treated base with 2.36 inches of hot mix asphalt pavement surface. 

The study clearly indicates that cement-treated base outperformed foamed asphalt base and non-stabilized base even when the asphalt surface was doubled. Rutting on a roadway is one of the first indicators of failures which leads to the propagation of more rutting and failures and the ultimate failure of the entire roadway. So my question to the road builder or designer is why not build a longer-lasting roadway in the first place?

In the California Research example, the amount of cement is 5 percent. This is typical for cement use where the range is commonly 3 to 7 percent depending on the results of a cement series test to determine a percentage of cement for the best performance. The minimal cost of cement is insignificant when considering the high performance of a roadway built with a cement-treated base. Whether you are building a new base road or rehabilitating an old base road with full-depth reclamation, Cement Stabilization is the key to longer-lasting roads. Cement-treated base improves the roadway by creating a long-lasting, water-resistant, freeze-resistant permanent modification to the road base aggregates to make a fully bonded pavement layer that is more resistant to fluctuations in temperature under Texas Summer Heat or Artic blasts than asphalt-treated base.

Every good road builder knows that better roads are built from the bottom up. If there is an opportunity to cement and stabilize the road base and the subgrade the result will be longer-lasting roads. Cement stabilization is being used in a higher plasticity index (PI) range of soils. High-speed pulverization now allows better gradation and mixing in the mid-PI range of soil. In the higher PI range of soils, the Cement Council of Texas is recommending the combination of lime and cement for consistent immediate strength, quantity management, and constructability that will allow subsequent pavement layers to be built immediately. 

At the beginning of this article, the diagram I show is a simple chip seal surface on a cement-treated base. A chip seal surface or as we say in Texas, seal coat, will last many years in many applications. In my experience, I’ve found that rapid curing asphalt with a grade 5 rock has worked well to adhere to the tighter base matrix formed by cement-treated base. 

If higher traffic warrants thicker pavement, hot mix asphalt surfacing of varying thickness can be used with a typical 10 to 15-year window for surface rehabilitation. The cement-treated base will be a permanent pavement and will last a lifetime with a good surface. The chip seal surface will help the added hot mix asphalt surface adhere to the strong, durable, and resilient Cement-Treated Base roadway.