Key Construction Technology for Steel-concrete Composite Beam Bridge Decking Prepared with PF-UHPC
In order to investigate the influence of different technical indicators on the performance of UHPC bridge decking in steel-concrete composite beams,to improve the preparation technology of premix for UHPC(PF-UHPC),and to produce steel-concrete composite beams with stable performance and meeting construction requirements,the influences of different technical indicators on the working performance and mechanical properties of PF-UHPC are compared and analyzed through experiments.The optimal technical indicators are determined,and a set of key technologies is developed for the construction of prefabricated and cast-in-place steel-concrete composite beam bridge decking with PF-UHPC.The result shows that the strength and working performance of the PF-UHPC base mix proportion meet the requirements,and increasing 0.3％dosage of water reducer can significantly improve the material's working performance without affecting its mechanical properties.When using a large mixer with a mixing time of 8 min,the best performance of the mixture is achieved.The setting time of materials is greatly influenced by indoor and outdoor environmental factors.The feeding sequence of steel fibers has a relatively small influence on the working performance and mechanical properties of the material,but the mixture with added steel fibers has a significant deviation in the uniformity of steel fibers.The flexural strength of the specimen is influenced by the orientation of steel fibers,which mainly depends on the direction of fabric.The greater the angle between the fabric direction and the flow direction of UHPC,the lower the flexural strength of the test decking.The vibration frequency has a significant influence on the flexural strength of UHPC,but has a smaller influence on the deviation of compressive strength and steel fiber content,and the 80 Hz vibration frequency is the most favorable.The hydration heat temperature of UHPC after wet curing is basically between 40 ℃ and 50 ℃,and the initial internal temperature increases with the increase of plate thickness.During the steam curing process,the temperature rise in the center of the UHPC plate is slower than that of the outside,and the temperature difference between the inside and outside is larger.The constant temperature inside the steam curing shed should be controlled above 90 ℃,and the natural cooling time should be appropriately extended.The bottom of a 25 cm thick decking should be kept at a constant temperature above 70 ℃ for 30 h,and its strength should meet the design requirements.
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