A relatively new method used to reduce the amount of cement-treated base (CTB) shrinkage cracking is microcracking of the CTB shortly after construction. Three portable instruments used in this study for monitoring the microcracking process include the heavy Clegg impact soil tester (CIST), portable falling-weight deflectometer (PFWD), and soil stiffness gauge (SSG). The specific objectives of this research were 1) to evaluate the sensitivity of each of the three portable instruments to microcracking, and 2) to compare measurements of CTB stiffness reduction obtained using the three devices. The test locations included in this study were Redwood Drive and Dale Avenue in Salt Lake City, Utah; 300 South in Spanish Fork, Utah; and a private access road in Wyoming. Experimental testing in the field consisted of randomized stationing at each site; sampling the CTB immediately after the cement was mixed into the reclaimed base material; compacting specimens for laboratory testing; and testing the CTB immediately after construction, immediately before microcracking, immediately after each pass of the vibratory roller during the microcracking process, and, in some instances, three days after microcracking. Several linear regression analyses were performed after data were collected using the CIST, PFWD, and SSG during the microcracking process to meet the objectives of this research. Results from the statistical analyses designed to evaluate the sensitivity of each of the three portable instruments to microcracking indicate that the PFWD and SSG are sensitive to microcracking, while the CIST is insensitive to microcracking. Results from the statistical analyses designed to compare measurements of CTB stiffness reduction demonstrate that neither of the instrument correlations involving the CIST are statistically significant. Only the correlation between the PFWD and SSG was shown to be statistically significant. Given the results of this research, engineers and contractors should utilize the PFWD or SSG for monitoring microcracking of CTB layers. The heavy CIST is unsuitable for monitoring microcracking and should not be used. For deriving target CTB stiffness reductions measured using either the PFWD or SSG from specified targets measured using the other, engineers and contractors should utilize the correlation chart developed in this research.

Friction is one of the essential aspects of pavement performance and safety. Unfortunately, the rate at which the friction data are being collected exceeds the rate at which the data can be proficiently analyzed. Furthermore, the Utah Department of Transportation (UDOT) lacks long-term trend analysis for the many years of locked-wheel skid trailer (LWST) data collected in Utah. In addition, UDOT is missing a statistically adequate correlation equation between friction-testing devices. Likewise, only one method is used in Utah to prequalify aggregates for use in pavements. Finally, there has not been an investigation of the potential use of lithium silicate solution in Utah as a hardening agent to decrease the rate of friction loss. This research consists of five objectives. The first objective was to investigate pavement friction factors that influence skid resistance; methods of measuring skid resistance in the laboratory and the field, including correlations between test results; methods of evaluating aggregate sources; and methods of enhancing skid resistance of asphalt pavements through a comprehensive literature review on these subjects. The second objective was to investigate temporal trends in skid numbers measured using the LWST on Utah highways with different surface treatment types. The third objective was to develop a three-way correlation between the skid number measured with the LWST in the field, the British pendulum number measured with the British pendulum tester (BPT) in the field, and the polish value measured with the BPT in the laboratory. The fourth objective was to investigate selected performance-related properties of aggregates used to produce surface treatments at several field sites representing Utah conditions. The fifth objective was to examine the potential benefits of lithium silicate treatment for improving the resistance of aggregates to polishing. The scope of the research for the five objectives included statistical analysis, field testing, and laboratory experimentation. The findings include, first, a literature review that identified four critical deficiencies in Utah’s friction-related literature, which formed the basis of the remaining four objectives. Second, a statistical analysis of 9 years of LWST data indicated above-average skid values across Utah’s pavement network. Third, correlations were evaluated for multiple friction-testing devices. Fourth, X-ray diffraction testing methods were found to compare favorably to the accelerated polish test. Fifth and finally, the effects of lithium silicate solution on polish-susceptible aggregates were documented. This research has substantially advanced the body of knowledge on pavement friction testing and improving the resistance of aggregates to polishing in Utah through laboratory and field experimentation

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