Abstract

The objective of this research was to analyze the strength and deformation characteristics of a cement-treated base (CTB) constructed using full-depth reclamation, microcracked, and then surfaced with a single chip seal. In this field study, strength characteristics of the CTB layer were determined at the time of construction, and then both strength and deformation characteristics were evaluated after 9 months of low-volume, heavy truck traffic. After 9 months, observed distresses included transverse cracking, rutting, and chip seal joint failure. The loss of the chip seal was caused by poor chip seal construction practices and not a deficiency in the CTB layer. The importance of the role of the chip seal as a wearing course was made evident by these failures since the exposed CTB often exhibited material loss. The average ride qualities in and out of the wheel path were in the fair ride category; the roughness was not likely caused by trafficking but probably resulted from construction or climatic factors. Structural testing performed after 9 months of service indicated that the CTB stiffness and modulus were greater than the values measured after microcracking at the time of construction, indicating continued strength gain. However, trafficking over the 9-month period had caused significantly lower stiffnesses measured in the wheel paths than between the wheel paths. The average unconfined compressive strength (UCS) of the cores tested at 9 months was not significantly different than the average UCS of the field-compacted specimens tested at 6 weeks. Based on the observed performance of the CTB and chip seal evaluated in this research, recommendations for improved CTB performance include the use of a thicker and/or stiffer CTB layer, ensuring a smooth CTB surface during construction, and application of a double chip seal or equivalent.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

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