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Static and cyclic fracture properties (Modes I, III, and I/III) of cement emulsified asphalt mortar at three frequencies were investigated in terms of the fracture energy and fatigue life, respectively. For this to achieve, 576 edge notched disk bend specimens with 16 haphazard mix designs including, disparate bitumen‐to‐cement (B/C), water‐to‐cement (W/C) ratios, and cement contents (C) were tested. By developing statistical models (at the 5% significance level, p value < 0.05), the findings revealed that under static loading, the fracture energy got highest in tearing mode and lowest in opening mode. In all fracture modes, the fracture energy decreased with an increase of C and decrease of B/C while the mortar's fatigue life augmented due to a rise in C and B/C. Moreover, the fatigue life gained an increase with the increase in the fracture energy, loading frequency, and Me in the nonlinear trend. The utmost variation of fatigue life was explained with the increase of fracture energy which had the greatest effect in mode‐III loading. Highlight: Predicting CEAM's static and cyclic fracture behavior (I/III) at three frequencies by RSM.Under static loading, the fracture energy is highest in mode III and lowest in mode I.Fatigue life increased with the increase in C, A/C, fracture energy, and loading frequency.Cement content had the greatest nonlinear effect on fatigue life in the mixed‐mode I/III. [ABSTRACT FROM AUTHOR]

• Low temperature fracture behaviors of cement emulsified mortar were investigated. • Fracture behaviors for tensile, shear and mixed tensile-shear were measured. • D-Optimal Mixture Design Method was employed. • Regression models based on the experimental results were developed. • Dependence of fracture mode I, II, and I/II on mix design ratios was demonstrated. • Tensile-shear and shear modes revealed lowest and highest fracture toughness. • Optimum designs for maximizing fracture toughness of all three modes was delimited. Cement emulsified asphalt mortar (CEAM) is a key component of ballastless rail track systems which is tasked with damping the train movement energy and transferring loads to the concrete roadbed. This mortar consists of asphalt emulsion, sand, cement, and water and enjoys better toughness and flexibility properties than cement mortar thanks to the combined effect of cement and asphalt emulsion. One of the primary causes of failure in this mortar is cracking at low temperatures. This study investigated the fracture toughness of CEAM (CRTS- II) with different volume percentages of mortar constituents, namely cement, sand, water, and asphalt emulsion, at low temperature in the linear elastic fracture mechanics (LEFM) framework. The critical stress intensity factors of the mortar for pure tensile (mode I), pure shear (mode II), and mixed tensile-shear (mixed mode I/II) fractures with M e values of respectively 1.0, 0, and 0. 67 were obtained. Considering the necessity of examining the effect of mix design ratios and their interactions and the need to limit these ratios to ensure acceptable rheological and mechanical properties, the experiments were designed using the D-Optimal mixture design method at 5% significance level. By assuming a quadratic model between the critical stress intensity factors of each fracture mode and the volume percentages of mortar constituents, a total of 20 randomized mix designs were obtained. For each mix design, the semi-circular bending (SCB) test was performed with at least 3 replications. The regression models based on the experimental results were developed. The findings demonstrated the dependence of mode I, mode II, and mixed mode I/II critical stress intensity factors on the mix design ratios. The lowest and highest fracture toughness estimates were related to the mixed tensile-shear and pure shear modes, respectively. Finally, the mixture design method was used to delimit the optimum mix design region for maximizing the fracture toughness of all three modes. [ABSTRACT FROM AUTHOR]

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 F E R i . The F E R i 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 F E R i values, freeze and thaw cycles appear to have more damaging effects on the mixed mode I/III fracture properties of CEAM. • Given DOE, mix designs with various C, A/C and W/C were planned. • 720 ENDB specimens underwent 0, 1, 3, 5 and 10 freeze and thaw cycles. • F E R i was estimated by RSM for explaining the link between the experimental values. • A/C had the utmost effect on mode I fracture energy and C did so on III and I/III. • More damages on the initial cycles of mixed mode I/III fracture were evinced. [ABSTRACT FROM AUTHOR]

• Effects of freeze–thaw cycles and aging on mixed-mode I/II fracture of CEAM were investigated. • Experiments were performed in three modes of loading; (I), (II), and (I/II). • d -optimal RSM suggested to fracture 864 SCB specimens with 16 mix designs at different C, A/C, and W/C. • Freeze-thaw cycles are more detrimental in reducing mode II fracture energy. • Aging has a more damaging impact on the pure tensile fracture. • Statistical models were developed for the relationship between FER and mix design variables. • A/C for mode I, and C for mode II and the mixed-mode I/II, had the greatest impact on FER of freeze/thaw, and A/C for that of aging. This study has been investigated the effect of freeze–thaw cycles and aging condition on the pure mode I, pure mode II and mixed-mode I/II fracture resistance of Cement Emulsified Asphalt Mortar (CEAM). The experiments were conducted on SCB specimens designed with 16 randomized mix designs with different cement contents (C), asphalt-to-cement ratios (A/C), and water-to-cement ratios (W/C) using the d -optimal response surface methodology. The specimens were divided into three groups: control specimens (n = 144), aged specimens (n = 144), and specimens subjected to 1, 3, 5, and 10 freeze–thaw cycles (n = 576). The experiments were performed in three modes of loading: pure tensile (I), pure shear (II), and mixed-mode tensile-shear (I/II). To assess the impact of freeze–thaw and aging damage on fracture properties, the Fracture Energy Ratio (FER) was defined as the ratio of fracture energy of the damaged/conditioned specimen to that of the corresponding control specimen. Then, a number of statistical models were developed for the relationship between FER and mix design variables (A/C, W/C, and C). The results showed that the application of freeze–thaw cycles reduced the fracture energy of CEAM in all three modes. The independent variable with the greatest impact on fracture energy changes was A/C for the pure tensile mode, and C for the pure shear mode and the mixed-mode tensile-shear. The initial freeze–thaw cycles were found to have a greater impact on fracture energy than later cycles. Also, freeze–thaw cycles are more detrimental in reducing mode II fracture energy than mode I and mixed-mode I/II fracture energies and therefore have a more damaging impact on the pure shear fracture properties of CEAM. Aging also reduced the fracture energy of CEAM in all three modes; an effect that was most greatly influenced by the amount of asphalt in the mortar composition. Aging had a greater impact on mode I fracture energy than mode II and mixed-mode I/II fracture energies. [ABSTRACT FROM AUTHOR]

• Fatigue life of CEAM with different mix designs under mixed-mode I/II loadings at three frequencies were investigated. • Several mix designs with different cement contents, asphalt-to-cement ratios, and water-to-cement ratios were created. • Dynamic tests on the SCB specimens were analyzed using the d -optimal response surface method. • Cement content and asphalt-to-cement ratio have the greatest effect on the fatigue life in all mixed tensile-shear loadings. • CEAM showed a longer fatigue life under dynamic loading in the pure shear mode. • Increasing the loading frequency increased the fatigue life of the mortar in all three modes. This study has investigated fatigue life of Cement Emulsified Asphalt Mortar (CEAM) under mixed-mode I/II loadings at the intermediate temperature. For this investigation, SCB specimens of 16 randomized mixture designs with different cement contents (C), asphalt-to-cement ratios (A/C), and water-to-cement ratios (W/C) were prepared and subjected to the cyclic mixed tensile-shear loading with Me = 0, 0.5, 1.0 at three frequencies of 2, 4 and 8 Hz. The results were analyzed using the d -optimal response surface method and revealed that for all three loading modes, the fatigue life increased with increasing C and A/C. The CEAM also showed a longer fatigue life in the pure shear mode than in the pure tensile mode. The difference between the fatigue life of mode I and II was found to be increasing with the increase in cement content and loading frequency. Increasing the loading frequency increased the fatigue life of the mortar in all three modes. [ABSTRACT FROM AUTHOR]

• Aging effect on the mixed-mode fracture behavior of CEAM was studied using ENDB sample. • Mix designs and fracture behavior were produced and predicted by Response Surface Method. • Aged and unaged sample showed the highest and lowest toughness in mode I and III, respectively. • A/C and A/C*W/C showed significant effect on stress intensity factor of all mode mixities. • Aging decreases critical stress intensity factor in all mode mixities but in different amounts. Aging can affect the fracture behavior of bitumen-containing composites due to an increase in the total stiffness of the material. In this study, the effect of aging on the behavior of Cement Emulsified Asphalt Mortar (CEAM) under the mixed-mode I/III fractures was investigated at an intermediate temperature, and its fracture behavior was modeled with the aid of Response Surface Methodology (RSM). To collect the experiential data, several mix designs with different cement contents (C: [460, 500] kg/m3), bitumen-to-cement ratios (A/C : [0.3, 0.5]), and water-to-cement ratios (W/C: [0.4, 0.6]) were generated by Central Composite Circumscribed (CCC) method. Then, a series of fracture tests were performed on aged and unaged Edge Notched Disc Bend (ENDB) specimens. The results showed that for both aged and unaged (control) specimens, the highest fracture toughness is obtained under pure tensile mode and by increasing the contribution of mode III the corresponding value of fracture toughness decreases. The developed statistical models revealed that for unaged specimens, the increase in the A/C ratio has a significant effect on the stress intensity factors of mode I, mode III and mixed-mode I/III. However, for aged specimens, the effect of A/C is significantly observed in its interaction with W/C. The effect of aging on the fracture toughness of mortar was also measured with an index called the ratio of Aged to Unaged Fracture Toughness (FTRi Aged/Unaged). The results showed that aging decreases the critical stress intensity factor of the mortar in the mode mixities, with the highest decrease of 15% under pure mode I. [ABSTRACT FROM AUTHOR]

• Intermediate temperature fracture behaviors of cement emulsified mortar were investigated. • Fracture behaviors for tensile, shear and mixed tensile-shear were measured. • D-Optimal Mixture Design Method was employed. • Regression models based on the experimental results were developed. • Dependence of fracture mode I, II and I/II on mix desgin ratios was demonstrated. • Highest fracture energy belonged to the pure shear mode and the lowest was related to the pure tensile mode. • Optimum designs for maximizing fracture toughness of all three modes was delimited. Being a combination of sand, cement, water, and asphalt emulsion, Cement Emulsified Asphalt Mortar (CEAM) has better toughness and flexibility properties than cement mortar. Given the multiphase nature of CEAM, it is susceptible to micro-cracking during the setting process and also due to other factors such as traffic loads, undesirable atmospheric conditions. Given the typical direction of loading and cracking in these mortars, they are likely to experience mixed-mode fractures. Therefore, this study investigated the fracture properties of CEAM at service temperature in mixed mode I&II fractures. For this investigation, the mixed-mode fracture energy was determined through experiments on Semi-Circular Bending (SCB) specimens with the volume fractions of mortar treated as independent variables and the material behavior assumed to be viscoelastic at ambient temperature. Considering the need to investigate the effect of mix design ratios and their interactions, to reduce the number of experiments, and to limit these ratios to the ranges that produce acceptable rheological and mechanical properties, the D-Optimal mixture design method at 5% significance level was used to optimize the design of experiments and related analyses. Next, a regression model was developed for the relationship between fracture energy in each mode (I, II, I&II) and the mortar constituents. Also, the optimum mix design range to reach maximum fracture energy in all three modes was determined by graphical optimization. Analysis of the results with ternary contour plots showed the dependence of fracture energy and the optimum mix design range in the studied modes on the mix ratios of the CEAM constituents. The Cement and asphalt were identified as the independent variables with greatest effects on fracture energy variations and the optimum mix design. The results also revealed that as the asphalt emulsion-to-cement ratio increased, the maximum carried force decreased and the deformation corresponding to this force increased. [ABSTRACT FROM AUTHOR]

• Fracture resistance (Mode I/III) of cement emulsified asphalt mortar was examined. • ENDB specimens at different A/C, W/C ratios and three low temperatures were tested. • ANOVA test and regression modeling were conducted at 5% significance level. • Fracture toughness is highest in the mode I and lowest value in the mode III. • A/C and Temperature have significant impact on K C in all and pure tensile modes. Having asphalt in Cement Emulsified Asphalt Mortar (CEAM), this composition has higher toughness and ductility but also higher thermal sensitivity than conventional cement mortar. This study was aimed at investigating the fracture behavior of CEAM under out-of-plane shear and tensile loadings (Mode I, I/III, III) at low temperature. This investigation was performed by testing Edge Notched Disc Bending (ENDB) specimens with different asphalt-to-cement and water-to-cement ratios at three temperatures. Scanning Electron Microscopy technique (SEM was also employed to evaluate the effect of asphalt-to-cement and water-to-cement ratios on the structure of CEAMs. The findings revealed that for CEAM, the fracture toughness attains its highest value at pure tensile mode I, decreases as the share of out-of-plane shear in the mixed-mode I/III loading increases, and reaches its lowest value in the pure out-of-plane shear mode III. Furthermore, a multiple regression model was extracted for the relationship between each critical stress intensity factor (K C) and asphalt-to-cement ratio (A/C), water-to-cement (W/C), and temperature (T). The analyses showed -at the 95% confidence level- that A/C have a significant impact on K C in all examined modes and also the fracture toughness of CEAM decreases with increasing A/C. Changes in W/C also had a significant impact on the pure shear mode and mixed tensile-shear mode (I/III) stress intensity factors. Temperature changes in the studied range only affected the pure tensile mode stress intensity factor. [ABSTRACT FROM AUTHOR]

• Design of experiment (DOE) and the Mixture Design Method were applied. • Mechanical and rheological properties of CA mortars were investigated. • Micro-structure of CA mortars was also explored by SEM technique. • Experimental results were used to develop models, trace and ternary contour plots. • Main and interactive effects of mixture components were inspected. • Optimal volumetric mix designs were determined based on the Mixture Design Method. This study investigated the effect of mixture components including cement, asphalt emulsion, sand, and water on mechanical and rheological properties of Cement Emulsified Asphalt (CA) mortars (type I and II). For this investigation, compressive strength, elastic modulus, segregation, fluidity (J funnel), and spread diameter and time (specific to type II mortar) tests were performed on fresh and hardened specimens. SEM technique was also employed to inspect the micro-structure of CA mortars. To study the effect of mix design factors and their interactions in the domain where rheological and mechanical requirements are met, the Mixture Design method was used in conjunction with the D-Optimal algorithm to design the experiments and analyze the results. After assuming a quadratic model for the relationships between response variables (mechanical and rheological properties) and independent variables (mixture components) including the main effects and two-way effects, 15 randomized mix designs were obtained for each type of mortar (30 mix designs in total). The test of compressive strength was performed on cubic 50 × 50 × 50 mm specimens at the age of 7 and 28 days. The Elastic modulus of the mortars was determined from the strain-strain diagram pertaining to the 28-day compressive strength specimens. Segregation was evaluated by the use of cylindrical 50 × 50ϕ specimens. Tests of fluidity, spread diameter, and spread time were performed according to the standards of the Ministry of Railways of China. The experimental results were used to develop the estimation models of the responses, and the effect of factors and their interactions on mechanical and rheological properties were studied at 95% confidence level. The estimated statistical models could accurately predict the performance of the mortars and were therefore employed to find the optimum combinations of mixture components. Trace and ternary contour plots were drawn to analyze and discuss the effects of mixture components and their interactions on the behavior of type I and type II mortars in each experiment. Finally, the superposition principle was used to combine the responses collected from the experiments, and a series of optimum mix designs based on low, moderate, and high cement contents were devised for both types of mortar. [ABSTRACT FROM AUTHOR]