Design And Performance Study Of Post-cast Concrete Material For Precast Bridge Deck Of ShuiTu Bridge

In this paper,the design and performance of the concrete material of the precast bridge deck cast-in-place laminated belt are carried out,relying on the actual engineering of Shui Tu Brige on Jialing River in Chongqing.Based on the analysis of the current domestic concrete mix design status,a new concrete mix design idea is proposed,which is to build a concrete material stacking structure through gradation theory,The effects of water consumption,water-to-binder ratio,admixture content,expansion agent type and content on the workability,mechanical properties and deformation properties of concrete were also studied,the research conclusions are as follows:(1)Based on the gradation theory,the concrete accumulation structure is constructed,and the Taibo theory is used for gradation design,that is,the experimental index n is changed to make the aggregate gradation reach the maximum density.The study found that when the experimental index n value is less than 0.55,the bulk density of the aggregate increases with the increase of the n value.When the n value is 0.5,the 5 aggregate reaches the maximum packing density and the gradation density reaches the maximum.When the value of n is greater than 0.55,the bulk density starts to decrease and the gradation density decreases.The particle interference theory is used for gradation design,that is,the aggregate density can be maximized by changing the particle size ratio.The study found that the bulk density of aggregates increased with decreasing particle size ratio.The workability of the concrete is optimized by changing the splitting coefficient of the concrete mix ratio of the stacked structure.The study found that when the splitting coefficient is between1.10 and 1.20,the workability of concrete increases with the increase of the splitting coefficient.When the coefficient is 1.20,the workability of concrete is optimal.However,after the removal coefficient exceeds 1.20,the concrete oozes or even segregates and the concrete compressive strength begins to decrease.(2)By changing the amount of expansion agent,the composition of cementitious materials and the design method of concrete,the influence of sulfoaluminate type expansion agent(HEAA)on the workability,mechanical properties and deformation properties of concrete was studied.The test results prove that there is no obvious correlation between the workability of the concrete and the amount of HEAA,but the workability of the concrete designed by the stacking structure is slightly worse than the traditional design method;The compressive strength of concrete decreases with the increase of the amount of HEAA;when the amount of HEAA is less than 11% of the amount of cementitious material,the limited expansion rate of concrete increases with the increase of HEAA.When the amount exceeds 11% of the amount of cementitious material,the limited expansion rate of concrete begins to decrease.(3)By changing the amount of expansion agent,the composition of cementitious materials and the design method of concrete,the influence of calcium oxide expansion agent(SCEA)on the workability,mechanical properties and deformation properties of concrete was studied.The test result proves that although there is no obvious correlation between the workability of concrete and the content of SCEA,the workability of concrete is generally good;The compressive strength of concrete shows a trend of increasing with the increase of SCEA content;the limited expansion rate of concrete increases with the increase of SCEA content.When the content of SCEA is8%,the limited expansion rate of concrete reaches the maximum.(4)Regardless of whether the concrete is designed by stacking structure or by the mix design rules,there is no obvious correlation between the amount of expansion agent and the working performance of concrete;The mechanical properties of concrete mixed with SCEA are better than those with HEAA;in general,concrete with HEAA shows a fast expansion rate and good expansion efficiency,but the volume stability in the later stage is not as good as concrete with SCEA,although the expansion rate of concrete after mixing with SCEA is lower than that of mixing with HEAA,the expansion rate is stable,and the volume stability after the late effluent is excellent.The risk of cracking under constrained conditions is low.(5)According to the progress of the project,verify the construction mix ratio and submit the technical data for the application.