Laboratory Study of Factors Affecting the Shrinkage Characteristics of Cement Treated Base.

摘要

For many years California has used cement treated base materials under asphalt concrete because of its strength and economy. However, any shrinkage cracking in the base tends to reflect through the paving. Surface water may then intrude and cause failures of the highway due to loss of stability in the supporting material. The most common remedial action taken is to seal these cracks with an asphalt compound. This sealing operation not only is costly but also results in some reduction in the riding quality as well as appearance of the roadway (Photo 1). Thus, the reduction or elimination of shrinkage cracking of cement treated base (CTB) is desirable. A review of data gathered in a prior field investigation of CTB shrinkage cracking (1) indicated that certain aggregates had a consistent tendency toward high, moderate, or low cracking. These aggregates were studied with respect to mineral content, surface area, and absorption. A laboratory test to measure the shrinkage of cement treated specimens was developed. When these same aggregates were tested, a positive correlation was found between laboratory and field shrinkage. This made it possible to conduct studies in the laboratory on the primary design and construction variables such as the amount type of cement, moisture, density, etc. The shrinkage test was also used to evaluate several potential additives for use to reduce pavement cracking due to shrinkage in the cement treated base.