Mixed mode (I&III) fracture behavior of cement emulsified asphalt mortar under freeze and thaw cycles

Abstract

The present study was designed to evaluate the impact of freeze and thaw cycles on pure tensile (I), pure shear (III), and mixed tensile–shear (I/III) fracture of Cement Emulsified Asphalt Mortar (CEAM) with diverse mix designs. For this purpose, a large number of Edge Notched Disk Bend (ENDB) specimens were fabricated with 16 different random mixture designs with various amounts of cement content (C) and different proportions asphalt-to-cement (A/C) and water-to-cement (W/C) proportions. The specimens of each mix design were divided into five groups: one control group (no freeze and thaw) and four test groups where the specimens underwent 1, 3, 5 and, 10 cycles of freezing and thawing. All of the specimens were then fractured in pure opening mode (I), pure tearing mode (III), and mixed opening–tearing modes (I/III). The results evinced that applying the cycles of freezing and thawing diminished the mortar’s fracture energy in each of the three modes. This drop was more intense after the initial cycles and became less so with an addition in cycles. The freeze and thaw-induced change in the fracture properties was measured in terms of the ratio of the fracture energy of the conditioned specimen in the specified mode to that of the control specimen, denoted by FERi. The FERi of mortars with different mix designs was estimated by developing multiple regression models to explain the relationship between this index’s experimental values and mix design variables (A/C, W/C, C) at the 0.05 significance level. Among the independent variables, A/C had the greatest effect on mode-I fracture energy changes, and C had the greatest effect on mode III and mixed-mode I/III fracture energy changes due to the freeze and thaw damage. Considering the predicted FERi values, freeze and thaw cycles appear to have more damaging effects on the mixed mode I/III fracture properties of CEAM.