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Gap exists in the interface of cement asphalt emulsion mortar and CRTS I track slab universally, which is more severe at four corners than other parts of the track slab. In this work, the temperature and elevation of CRTS I slab track with and without rail were measured continuously to study the influence mechanism of rail on the gap. The results show that the alternating temperature gradient of track slab is the main reason that causes the gap, and laying rail can efficiently decrease the gap size in the slab track without rail. Compared with the slab track without rail, the maximum elevation occurred at the corner, the maximum gap width and the maximum gap depth of the slab track with rail laid were decreased by 0.45 mm (25.7%), 0.75 mm (46.6%) and 9.5 mm (59.4%), respectively; meanwhile, the disqualification ratio at corners was reduced to 5.9%, which is 50% less than that of the track without rail. When elevation mismatch occurs in adjacent track slabs, a gasket should be placed at rail-bearing bed below the track slab in order to avoid the lower slab being dragged up by the higher slab and the further occurrence of new gap. [ABSTRACT FROM AUTHOR]

Abstract: This contribution first presents a fatigue model to elaborate fatigue behavior of materials subjected to thermal mechanical effect. To calibrate the presented model, a valid experiment is then conducted on cement asphalt mortar. The model can be further extended to other materials and valid experimental data from literature is utilized for verification. Results suggested the model is sufficient to describe thermo-mechanical fatigue behavior of cement-based materials, under the condition that no phase or morphological change occurred in the fatigue temperature range. Finally, the developed model is applied to predict fatigue life of one current track. [Copyright &y& Elsevier]

Cement asphalt mortar (CA mortar) is the key component in slab track and serves as the elastic shock absorber. The prominent presence of asphalt renders the mechanical properties of CA mortar susceptible to temperature variation. In this paper, the compressive strength of CA mortar was investigated at different temperatures (0, 20, 40, and 60°C [32, 68, 104, and 140°F]) and a temperature stability coefficient (TSC) was put forward to indicate this temperature dependence. Influences of asphalt emulsioncement ratio (A/C), and addition of the silica fume (SF) and crumb rubber (CR) on the temperature stability of compressive strength of CA mortar were also explored. Results indicate that the compressive strength of CA mortar decreases with higher temperature. The addition of SF and CR mitigates the temperature dependency to some extent. [ABSTRACT FROM AUTHOR]

• The newly developed two-phase model class selection algorithm for void detection is firstly proposed. • The time-domain Bayesian model updating is successfully conducted for the CA void detection of the ballastless slab track by determining the most probable values (MPVs) of mortar stiffness scaling factors. • Not only the void location but also the severity of CA mortar are detected for ballastless slab track. This paper reports the feasibility study on the use of measured vibration of a railway slab track system in detecting void on the cement-emulsified asphalt (CA) mortar layer utilizing the Bayesian approach. By following the specification of the China Railway Track System (CRTS)-I ballastless slab track structure, two scaled models (with and without void in the CA mortar layer) were built and tested in the laboratory to demonstrate and verify the proposed CA void detection methodology. A three-dimensional finite element model was built using ABAQUS to calculate the time-domain data of the ballastless track system for Bayesian model class selection and model updating. A new two-phase model class selection algorithm was developed for identifying the CA void region. The proposed methodology identified the distribution of CA mortar stiffness using impact hammer test data from the scaled CRTS-I ballastless slab panel under laboratory conditions. The model updating results are consistent with the simulated CA mortar stiffness distribution. In addition, the posterior uncertainties of the identified CA mortar stiffness under different sensor configurations were quantitatively investigated. The results from the experimental case studies show that the proposed Bayesian methodology is feasible to detect CA void even with only a single accelerometer with the associated posterior uncertainties being kept at an acceptable level. [ABSTRACT FROM AUTHOR]

Asphalt emulsion is an important component in the preparation of cement asphalt mortar. In the work reported here, different emulsifiers and basic asphalts were used to manufacture emulsions and their properties were investigated. Results indicate that a diamine-based emulsifier renders asphalt emulsion that exhibits better compatibility with cement; lower density and higher ductility basic asphalt; and that styrene-butadiene-styrene modifiers are more appropriate in the manufacturing of emulsion. [ABSTRACT FROM AUTHOR]

• Study the relationship between mechanical properties and composition of CA mortar. • A mechanical model of CA mortar from four different levels was proposed based on experimental results and theoris. • The asphalt has a limited contribution to the static compressive strength f and elastic modulus E CA of the CA mortar. As an organic–inorganic composite material, the mechanical properties of cement asphalt mortar (CA mortar) are closely related to its composition. In order to studying the relationship between mechanical properties and composition of CA mortar, a mechanical model of CA mortar from four different levels (i.e.,cement hydration products, cement gel skeleton, cement-asphalt composite system and CA mortar) was proposed based on the microscopic experimental results, the gel-space ratio theory and the Hashin composite ball model. The mathematical relationships among the elastic modulus of CA mortar, compressive strength f and composition parameters were derived. The results shown: The volume fraction of cement hydrates is an important parameter affecting the CA mortar elastic modulus E CA and the compressive strength f. When the asphalt is regarded as a pore or a low modulus phase, the static elastic modulus of the CA mortar E CA and the volume fraction of cement hydrates V CH , the compressive strength f and gel-space ratio x all have a power function relationship, and R 2 > 0.7. The cement hydrates in the CA mortar are still a continuous phase and constitutes the composite gel skeleton, asphalt interspersing among them, and the contribution of asphalt to the CA mortar strength and elastic modulus is relatively limited. [ABSTRACT FROM AUTHOR]