Texas Transportation Institute
Improving Long-Term Flexible Pavement Performance
"While the use of excessive cement frequently results in very stiff bases that shrink and crack, insufficient amounts of stabilizer may not provide adequate durability under imposed traffic loads and environmental conditions."
W. Spencer Guthrie, Stephen Sebesta, and Tom Scullion, P.E.
Project Summary Report 7-4920-S
Recent research projects at the Texas Transportation Institute (TTI) have focused on methods of improving the long-term performance of cement-treated bases. These methods primarily address proper selection of optimum cement contents through laboratory testing and innovative construction techniques in the field.
Most problems with cement-stabilized base layers in pavements stem from the fact that current design practices are based only on strength, without consideration of long-term durability or performance. For example, many state departments of transportation require sufficient cement to achieve a minimum unconfined compressive strength as high as 750 psi after seven days. While this level of cement results in a very stiff aggregate layer characterized by a high resilient modulus, it does not necessarily guarantee acceptable long-term pavement performance.
In many roadways, for instance, shrinkage cracks within heavily cement-stabilized base layers reflect into the surface treatments and appear as transverse cracks spaced between 3 ft and 60 ft, as shown in Figure 1. Although the cracks themselves may not present a structural problem, they often accelerate deterioration of the pavement by allowing water to enter lower pavement layers. Several documented cases demonstrate the ability of moisture to disintegrate underlying base materials, causing a reduction in pavement support and a corresponding increase in pavement roughness that often leads to unacceptable ride quality.