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• The early-age deformation behaviors of CA mortar with AP and/or UEA were studied. • Deformation results from the graduated flask method and the buoyancy method were compared. • Four deformation stages of CA mortar were found and the underlying mechanisms were discussed. Early-age deformation of cement emulsified asphalt mortar (CA mortar) is a key parameter for its application in the CRTS I and CRTS II slab ballastless tracks of China. In this paper, the buoyancy method was used to measure the early-age deformation behaviors of CA mortars with aluminum powder (AP) and/or U-type expansive agent (UEA). The results indicate that the buoyancy method accurately and stably reflects the early-age deformation of CA mortar. The deformations of CA mortars with AP and/or UEA are composed of four stages: slight shrinkage stage, fast expansion stage, gradual shrinkage stage, and stable stage. Further analyses of relative expansions of samples reveal that different mechanisms of AP and UEA take effect at the gradual shrinkage stage of CA mortar deformation. Thermal effect induced by internal heat accumulation increases the air pressure in voids entrained by AP in CA mortar, thereby increasing the peak deformation values. Then the deformation tends to decrease with heat dissipation at the gradual shrinkage stage. Similar shrinkage stage is also observed in field tests. The buoyancy method can reflect the entire early-age deformation process of CA mortar with AP. This method is more suitable for engineering applications than the graduated flask method which is standardized in the specifications of China. [ABSTRACT FROM AUTHOR]

The stress relaxation behavior of cement and asphalt mortar (CA mortar) under different initial strain levels was investigated. Results show that the stress relaxation of CA mortar can be divided into two parts: the attenuation stress relaxation stage and stable stress relaxation stage. With the increasing strain levels, the relaxed stress, stress relaxation rate, stress relaxation modulus and specific stress relaxation of CA mortar increase gradually. Under the same initial strain level, the relaxed stress of type I CA mortar and type II CA mortar are little different, whereas the specific stress relaxation of type I CA mortar is much greater than that of type II CA mortar. In the strain range of 0.32–0.80%, the isochronous stress-strain relation of type I CA mortar is linear. When the strain is greater than 0.80%, the isochronous stress-strain relationship concaves to the strain axis gradually. The isochronous stress-strain relationship of type II CA mortar show linear increase in the strain range of 0.47–1.42%. A stress relaxation model based on thermodynamic theory was established, which agrees very well with the experimental results. [ABSTRACT FROM AUTHOR]