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Optimization design and mechanism analysis of bridge concrete in
high cold region based on salt-freezing |
Key Laboratory for Special Area Highway Engineering of Ministry of Education, Chang′an University, Xi′an, Shaanxi 710064, China |
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Abstract To explore the feasible measures for improving the durability of concrete bridges in cold area, the orthogonal test was designed to investigate the damage law of water binder ratio, water content and air entraining agent on the bridge main tower concrete C50, bridge deck concrete C40 and platform concrete C30, and the range of parameters with salt frost resistance of concrete bridge was proposed based on the alpine region. The microscopic mechanism was analyzed by scanning electron microscope and mercury injection test. The results show that the most significant factors affecting the frost resistance of concrete are the dosage of air entraining agent and water consumption. When the water consumption is reduced from 156 kg?m-3 to 144 kg?m-3, the C40 bridge deck concrete erosion amount is decreased by 13.0%. After freeze-thaw cycles for 300 times, the loss rate of flexural tensile strength is only 20%. Controlling the gas content of 4.5% to 5.0% in most specimens, after 300 freeze-thaw cycles of dynamic, the relative elastic modulus of main tower concrete C50 is always above 87%, and the internal microcrack of concrete is low with high transition zone density, optimum pore distribution and increased macro frost resistance.
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