Long-term mechanical properties of in situ semi-rigid base materials

Abstract

This paper presents a laboratory study on the strength and fatigue properties of semi-rigid base cores taken from expressways in Jiangsu, China. Compressive and semicircle bending (SCB) tests were conducted. The annual pavement deflection basin evaluation results indicated that the stiffness of the cement treated base (CTB) increased slightly after 10 years of service, while that of the lime and fly ash treated base (LFTB) decreased slightly. Strong relationships were observed among the unconfined compressive strength, static modulus, dynamic modulus, and SCB strength of the semi-rigid base cores. The fractured specimens showed that fracturing tends to occur at the interface between the aggregates and cement mortar. The strength of the CTB increased after 15 years of service, while the strength of LFTB in the drive lane showed a decreasing trend from 16 to 18 years of service. The SCB fatigue test results showed that the CTB also had a much greater fatigue life than those of LFTB. The SCB and beam fatigue tests exhibited failure faster than the indirect tensile fatigue tests did and were more sensitive to the stress ratio. The fatigue life of the semi-rigid base increased dramatically with a decrease in the stress ratio; therefore, the semi-rigid base could be considered a potentially long-life structure when the stress is controlled to a lower level. Based on the fatigue test results and mechanic analysis, the fatigue model of semi-rigid base structure is established for the typical semi-rigid base structure in Jiangsu.