Water erosion is one of the major factors for performance degradation of cement asphalt mortar (abbreviated to CA mortar, or CAM). In this paper, the influence of gap depth, coupling effect of water and pressure on the fatigue behavior of CA mortar was investigated. Results indicated that the damage of bonding surface became more seriously with the increase of gap depth, and when the gap depth was 19 to 38% of the structure size, the destruction exacerbated. Results also indicated that CA mortar was damaged more seriously under the coupling effect of water and pressure; the destruction first occurred on the surface between slab track and CA mortar rather than that between concrete roadbed and CA mortar. Timely repair with epoxy resin prevented the further water erosion well, and improved the service life of CA mortar.

Cement asphalt mortar (CA mortar, or CAM) is a composite material with equal presence of cement and asphalt emulsion and acts as a cushion layer in the structure of slab track. In the hardened matrix, asphalt accounts for about 30 vol. %, rendering the properties of CA mortar susceptible to temperature variation. In the paper, different kinds of emulsified asphalts (A70 emulsified asphalt, A90 emulsified asphalt, SBS modified emulsified asphalt and SBR modified emulsified asphalt) for CA mortar and the compressive strengths of CA mortar under different temperatures (-18°C, 10°C, 25°C, 40°C and 60°C) were studied to reflect its thermal dependence. Results indicate that temperature susceptibility of CA mortar prepared with modified emulsified asphalt is better than which prepared with unmodified emulsified asphalt. SBS modified emulsified asphalt -CAM (viz. CA mortar prepared by SBS modified emulsified asphalt) is alleviated at the whole temperature range, while that of SBR modified emulsified asphalt -CAM is improved primarily at the lower temperature region. As for types of unmodified asphalts, A90 emulsified asphalt -CAM outperforms A70 emulsified asphalt -CAM at lower temperature range.

In this paper, freezing and thawing resistance of CA mortar was investigated and some influential factors such as the ratio between asphalt emulsion and cement (A/C), cement types, various additives were also explored. Results indicated that a gain of mass was observed for every mixture after the test; mixtures with a higher A/C performed better in terms of higher relative elastic moduli. Mixtures proportioned by partially replacing ordinary Portland cement (OPC) with sulfoalumninate cement (SAC) underperformed in freezing and thawing property. Addition of crumb rubber powder (CRP), redispersible polymer powder (RPP) and organic fiber (FR) improved the resistance of CA mortar to freezing and thawing while that of silica fume (SF) undermined it.

Porous cementitious mixtures were prepared with two different spherical particles: expanded polystyrene (EPS) and superabsorbent polymer (SAP). The effect of EPS and SAP on the compressive strength, ultrasonic transmission, internal relative humidity and hydration degree under different volume fraction were studied. Results indicated that SAP matrix possessed much higher compressive strength (30-60%, 28d), ultrasonic transmission velocity, internal humidity (11-13%RH, 28d) and hydration degree (13-21%, 28d) than EPS matrix, which indicated that the desorption of SAP accelerated the hydration and increased the compactness of the surrounding cement paste. The internal cured pores left by SAP might have been strengthened which was different from ordinary pores produced by EPS.

Cement asphalt mortar (CA mortar) is a highly flowable grouting material used in the slab track structure. Temperature significantly influences the workable time of CA mortar. The workable time of CA mortar is controlled by the adsorption of asphalt droplets in the emulsion on cement grains. In the present study, the absorption behaviours under different temperatures were investigated to reveal the influences of temperature on workable properties of CA mortar. A laser particle size analyzer was employed to characterize the particle size variation in the cement and asphalt emulsion (CAE) system. The results indicated that the particle size increased more prominently at elevated temperature; The viscosity of the CAE system was measured by a rotational viscometer, results indicated that variation pattern of viscosity correlated well with that of the particle size in the CAE system and the increase of particle size was partially accountable for the increase of viscosity and impairing the flowability of CA mortar; the workable properties of CA mortar were also investigated, results showed that the slump flow increased and the workable time decreased with the increase of temperature. The addition of non-ionic emulsifier could retard the adsorption behaviour between cement and asphalt and prolong the workable time of CA mortar.