Flatness warping of CRTS III track slabs during curing phase

At present, there is a problem of excessive flatness warping in high-speed railway CRTS III type ballastless track slabs on certain railway lines. To analyze the evolution of flatness warping in track slabs and propose effective solutions, this study measured the compressive strength of the concrete used in track slabs, and the flatness warping of track slabs during the water curing and wet curing stages. A comparative experiment was also conducted to evaluate six improvement designs of track slabs. A model was developed to calculate the flatness warping of track slabs during the natural curing stage. The primary findings are as follows: (1) After the demoulding of the track slab, central upward arching deformation occurs at all stages due to the combined effects of drying shrinkage, thermal shrinkage, prestressing, and creep. The flatness warping generated during steam curing stage is a prerequisite; (2) During the curing phase, the primary factors causing excessive flatness warping in track slabs are drying shrinkage and thermal shrinkage; (3) The issue of excessive flatness warping of track slabs can be effectively resolved by employing secondary water spraying and setting a 0.5 mm reverse arch. Additionally, when the temperature is below 0degree celsius and the relative humidity is less than 0.55, it is necessary to apply insulation and moisturizing measures to the track slabs during the natural curing stage.