Application of crushed pebble concrete in simply supported girder bridges
1. The use of crushed pebbles on the physical properties of concrete
River pebbles in the formation process, in the process of carrying water constantly extrusion, friction, lost the angles, the surface is smoother, so it is less friction on the concrete sand and ash, we use the river pebble crushing production of crushed pebbles through sieving and the stone obtained by good grade, and the angles are less than artificial crushed stone, so the use of crushed pebbles mixed with concrete and better ease. Compared with crushed concrete, crushed pebble concrete has high coarse aggregate content and reduced sand rate, which not only ensures the workability of concrete, easy to construct on site, but also reduces production costs and improves economic efficiency. Judging from the perspective of physical properties, crushed pebbles are suitable for use in concrete mixes.
2. The effect of using crushed pebbles on the mechanical properties of concrete
The compressive strength of C50 concrete mixed with crushed pebbles is higher than that of pebble concrete by 8.4% and lower than that of crushed concrete by 2.4% at 28d age and under the same conditions of curing, and the 28d compressive strength of concrete prepared with all three materials is greater than 50MPa, which meets the design requirements. The sand rate of crushed pebble concrete is 3% lower than that of crushed concrete, and the former has a high coarse aggregate content, coupled with the use of crushed pebbles with good particle gradation and small needle-like content, the aggregate filling in the mixed concrete is better and evenly distributed, which can effectively reduce the shrinkage cracks in the concrete, so the crack resistance of concrete can also be effectively controlled, and the durability has been improved, which has a high value of use. Therefore, it is said that whether from the physical properties or from the mechanical properties of crushed pebble concrete to analyze, it is suitable for use in the conditions of the region.
3. Application of crushed pebble concrete in simple-supported girder bridge
The superstructure of Kapsilang River Bridge adopts assembled post-tensioned prestressed reinforced concrete box girders, and the precast box girders as well as the post-continuous construction and the cast-in-place layer of the bridge deck are C50 concrete. Taking the box girder precast concrete as an example, the use of crushed pebbles to mix C50 concrete has certain superiority in the casting process. The sequence of box girder concrete pouring is generally as follows: the bottom plate of box girder is poured first, then the webs on both sides are poured, and finally the top plate and wing plate are poured. As the construction process of box girder concrete is complicated, the construction time is long, and the requirement of concrete compatibility is high, the concrete needs to maintain the slump, to prevent the slump is too small to cause concrete lifting difficulties, so that the concrete lacks cement mortar filling and not dense, at the same time, the concrete should have a certain viscosity, so that the concrete in the process of unloading will not flow and produce segregation phenomenon, and can be in the process of vibrating Keep the concrete particles uniform. We use crushed pebbles to mix concrete, can improve the proportion of stone, reduce the sand rate, not only to meet the construction and ease of concrete, but also to improve the quality of concrete, in addition, the use of high-efficiency water-reducing agent can reduce the water-cement ratio, improve the mortar coating on the surface of concrete rubble, increase the viscosity of concrete, so as to be able to reduce the sinking of aggregates caused by pounding.
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