Early-Age Strength Assessment of Cement-Treated Base Material

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To avoid early-age damage to cement-treated base (CTB) materials, the cement must be allowed to cure before the pavement can be opened to traffic. The purpose of this research was to evaluate the utilities of the soil stiffness gauge (SSG), the heavy Clegg impact soil tester (CIST), the dynamic cone penetrometer, and the falling weight deflectometer for assessing early-age strength gain of cement-stabilized materials. Experiments were performed at four sites on a pavement reconstruction project along I-84 in Morgan, Utah, where 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 from 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 used to evaluate the repeatability of these devices and their sensitivity to curing time. The results indicated that although the SSG was more repeatable at one site, the CIST data were markedly more sensitive to curing time than the SSG data at all cement-treated sites during the first 72 h 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.