Abstract
The influence of sulphoaluminate cement and the dosage of polypropylene fibers on the basic mechanical strengths (compressive and flexural strengths) of reactive powder concrete (RPC) cured for 1 d, 3 d, 7 d, 14 d and 28 d is studied in this research. The content of sulphoaluminate cement ranges from 0% to 100% and the dosages of polypropylene fibers are 0%~3.5%, respectively. Moreover, the mechanical properties (compressive and flexural strengths), the relative dynamic elastic modulus (RDEM) and the chloride permeability of specimens with 50% sulphoaluminate cement and different dosages of polypropylene fibers are determined after the specimens are exposed to different NaCl freeze–thaw cycles. The water–binder ratio in this study is 0.25, and the sand-to-binder ratio is 1.25. Results show that the relationship between the mechanical strengths of RPC at early curing ages (lower than 7 d) and the sulphoaluminate cement content is a linear function with a positive correlation. However, when the curing age reaches 14 d, the compressive and flexural strengths decrease in the form of a linear function with the addition of sulphoaluminate cement. The correlation between the mechanical strengths and polypropylene fiber volume is a positive quadratic function. However, the mass loss rate and flexural strength loss rate increased in the form of a quadratic function, and RDEM shows a negative quadratic function with the freeze–thaw cycles. Moreover, the compressive strength loss rate increases linearly with the freeze–thaw cycle. The addition of polypropylene fibers can effectively improve the freeze–thaw resistance of cement mortar with an assembly unit of ordinary cement and sulphoaluminate cement.
Highlights
Nowadays, large-scale marine concrete constructs have been widely used in China’s civil engineering construction projects
The YAW-300 microcomputer full-automatic universal tester with the maximum testing force of 300 kN manufactured by Henruijin Co., Ltd., Jinan, China was used to measure the mechanical strengths of the reactive powder concrete (RPC) according to the GB/T 17671-1999 Chinese standard [18]
−15 ◦ C to 8 ◦ C was utilized for the NaCl freeze–thaw experiment according to the Chinese
Summary
Large-scale marine concrete constructs (like Hangzhou Bay Bridge, JiaozhouBay Bridge, and Hong Kong-Zhuhai-Macao Bridge etc.) have been widely used in China’s civil engineering construction projects. When the concrete structure has been put to use in a coastal environment over a long period, the concrete materials can be seriously damaged due to the complex chloride corrosion from seawater [1]. In order to solve these problems, the damaged concrete structures need to be repaired routinely. Some important traffic structures in coastal cities, such as sea crossing bridges and highways, are frequently damaged due to the marine environment. The damages to concrete construction should be repaired quickly so as to prevent further deterioration, traffic jams and other problems [2]. In response to these problems, fast-hardening, high-performance, cement-based materials are needed
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