Frequently Asked Soil-Cement Questions
Pavements Home > Soil-Cement > Soil-Cement FAQs > CTB vs GAB

For base material, is there a cost advantage in using a cement-treated base over an unbound graded aggregate base?

A: Obviously, the difference in cost between a cement-treated base (CTB) and an unbound graded aggregate base (GAB) will vary depending upon location, availability and cost of materials, and costs associated with placing the materials. However, in many cases, the cost of CTB is less than GAB. As an example, in the southeastern United States during the past two years, the cost of a 6-inch CTB section has been between 20 and 30 percent less than a 6-inch GAB section (including all associated costs such as materials, hauling, spreading, compacting, finishing, etc.).

But simply looking at the percent savings for a comparable thickness of pavement does not tell the whole story. One of the major engineering benefits of CTB is that because it is a bound material it requires less thickness to provide the same structural capacity as GAB. By using the AASHTO layer coefficients for pavement materials, a commonly accepted “rule of thumb” is that six inches of CTB is equal to eight inches of GAB. This results in even greater cost savings!

Another item to consider is that the extra structural capacity provided by having a cement-stabilized pavement layer can be factored into an overall pavement evaluation. By increasing the CTB thickness and reducing the surface course material (normally hot-mix asphalt) even further savings can be realized, especially considering the spiraling price increase of petroleum products today. For further information on the applications, benefits, design, construction, testing, and performance of CTB, please refer to PCA publication EB236, Guide to Cement-Treated Base (CTB).

 
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