Long-Term Modulus Values of Microcracked Cement-Treated Base Layers in Utah

The objectives of this research were to determine long-term modulus values of cement-treated base (CTB) layers constructed in Utah using microcracking and analyze the correlation between the backcalculated modulus values and 7-day unconfined compressive strength (UCS) values. Testing was performed at five sites in northern Utah, where reconstruction with full-depth reclamation was performed from August 2008 to October 2020. UCS data for the CTB material were collected during each reconstruction project and compiled in this research. Modulus values were determined from the portable falling-weight deflectometer test in December 2022 using backcalculation software. The average 7-day UCS values ranged from 2.52 MPa (366 psi) to 3.85 MPa (559 psi), and the CTB modulus values ranged from 290 MPa (42 ksi) to 2,989 MPa (433 ksi). A correlation between the backcalculated modulus values and 7-day UCS values was developed for estimating the long-term modulus values of microcracked CTB layers constructed in a seasonally cold climate, such as northern Utah.