Early-Age Strength Assessment of Cement-Treated Base Material (05-2524)**
W. Spencer Guthrie, Brigham Young University
Tyler B. Young, Brigham Young University
Brandon James Blankenagel, City of Spokane
Dane A. Cooley, Kimley-Horn & Associates, Inc.
In order to avoid early-age damage to cement-treated base (CTB) materials, the cement must be allowed to cure for a period of time before the pavement can be opened to traffic. The purpose of this research was to evaluate the utility of the soil stiffness gauge (SSG), heavy Clegg impact soil tester (CIST), dynamic cone penetrometer, and falling-weight deflectometer for assessing early-age strength gain of cement-stabilized materials. Experimentation was performed at four sites on a pavement reconstruction project along Interstate 84 in Morgan, Utah, in which cement stabilization was used in conjunction with full-depth recycling. Each site was stationed to facilitate repeated measurements at the same locations with different devices and at different curing times. Because of the considerable attention they have received in the pavement construction industry for routine quality control and quality assurance programs, the SSG and CIST were the primary focus of the research. Statistical techniques were utilized to evaluate the repeatability of these devices and their sensitivity to curing time. The results indicated that while the SSG was more repeatable at one site, the CIST data were markedly more sensitive to curing time than the SSG data at all of the cement-treated sites during the first 72 hours after construction. For this reason, the data suggest that the CIST offers greater overall utility than the SSG for monitoring early-age strength gain of CTB. Further research is needed to investigate appropriate thresholds and protocols for these testing methods that ensure adequate reliability of the collected data.