Degradation mechanism of CA mortar in CRTS I slab ballastless railway track in the Southwest acid rain region of China – Materials analysis

Abstract

Cement-emulsified asphalt mortar (CA mortar) is a key component of ballastless high-speed rail systems. Previous research illustrates acidic substances can provoke an intense deterioration on CA mortar. In order to investigate the relationship between acid rain environment and degradation mechanism of CA mortar in practical engineering, microstructure and organic-inorganic compositions of CA mortar collected from Chongqing and Chengdu were observed respectively. The degree of acid rain corrosion and thaumasite sulfate attack (TSA) were identified by analyzing the quantity and distribution of hydration products with XRD, SEM-EDAX, FTIR. The data of Ca(OH)2 X-ray diffraction intensity and weight loss of CA mortar in specific temperature range was used to calculate asphalt content. The asphalt components were examined using TG-DTA. Results showed that the loss of asphalt and asphaltenes under the coupling effects of loads and rain was one of the main reasons for the material degradation, instead of salt crystallization erosion or TSA caused by acid rain, neither the oxidation aging of asphalt. The results of this research will promote the microstructure optimization of CA mortar, and the development of the repairing material or technology to improve the maintenance system for high speed railways in different regions.