Keywords: cement asphalt mortar, high speed rails, rapid hardening, ballastless track, expansive cements, asphalt emulsion.

Cement asphalt mortar is a cushion layer performing the role of vibration absorption in the ballast-less tracks under high-speed rail infrastructure. The compressive strength of hardened CAM, satisfying the 1, 7 and 28-day strength requirement stands as a crucial performance parameter. Strength development is governed by the asphalt content and the choice of cementitious component and hydration aiding agents added during production. The present study relates to the development of rapid-hardening CAM for repair applications where achieving the strength in the short duration is crucial considering the seamless operation. It examines the influence of cementitious component choice, its chemical composition, and blending proportion on CAM compressive strength. Seven CAM combinations were evaluated, and results identifying ordinary Portland cement and calcium aluminate cement in a 90:10 ratio as superior to ordinary Portland cement with calcium sulphoaluminate. Significant impacts of CAC grade and sulphate proportion on CAM strength are noted, correlated with strength development. Mass percentages of oxides demonstrate positive Al2O3 dependence and negative SO3 dependence on strength development. Optimized cementitious component for CAM formulation includes 10% CAC with 50-75% Al2O3 content blended with 90% OPC and hardening admixture, for rapid-hardening repair mortar, ensuring strength within short durations.

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