Abstract
The use of cement emulsified asphalt mortar (CA mortar) in the track structure of high-speed speed railways has been gaining considerations by many researchers due to its coupled merits of the strength of cement as well as the flexibility of asphalt material. The asphalt to cement ratio (A/C) and the compatibility among constituent materials are crucial to the properties of CA mortar. To improve the performance properties and application of CA mortar, it is imperative to have a broad understanding of the composition mechanisms and compatibility between constituent materials. This paper summarizes interesting research outcomes related to the composition and properties of CA mortar. The consumption of water by cement promotes the breakdown of emulsified asphalt, likewise, the adsorption of asphalt droplets on the surface of cement grains retards the hydration process of cement. An appropriate A/C is required for the cement hydration rate to match the speed of demulsification of asphalt emulsion. Depending on the type and properties for which the CA mortar is designed to possess, the A/C ranges from 0.2 to 0.6 for type 1 (CAM I), and 0.6 to 1.2 for type 2 (CAM II). This paper also discusses measures taken to improve performance properties, compatibility, the interaction between constituent materials of CA mortar, and the use of additives as a partial replacement of cement in CA mortar production. The current review also suggests areas of interest for future research studies. This paper is useful to those who aim to understand or study the composition mechanisms and performance properties of CA mortar.
Highlights
With the design of high-speed rail, there has been an increasing demand for a highquality railway system that includes railway tracks, communication, and a signal system, etc
As a result of this technique, it has become necessary to provide a narrow gap between the track slab and trackbed, which is filled up with a grouting material to serve as a cushion layer after hardening. cement emulsified asphalt mortar is used as the cushion material in the construction of CRTS I
When asphalt emulsion and cement are mixed, they interact with each other in such a way that the consumption of water due to the hydration of cement accelerates the breakdown of emulsified asphalt; likewise, the adsorption of asphalt droplets on the surface of cement grains slows down the cement hydration process [1,31,32]
Summary
With the design of high-speed rail, there has been an increasing demand for a highquality railway system that includes railway tracks, communication, and a signal system, etc. With the properties of asphalt being more influenced by temperature as compared to cement, the dynamic mechanical response of CA mortar under varied service temperatures may differ [11] Both CAM I and CAM II have their advantages and preferences. The properties of asphalt material are delicate to climatic conditions such as moisture and temperature, in this technique, the incorporation of cement will mitigate this problem Though this technique receives attention from researchers all over the globe, the life-cycle cost analysis has been limited in this regard. A comprehensive review on the compatibility between constituent materials, the microstructure of cement asphalt binder (CAB), structural development, and the effect of A/C on properties of CA mortar is presented in this study. Possible arrears for future research are suggested based on previous studies reported
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