| Slip form construction technology has gradually attracted extensive attention and research because of its convenient,fast and economic advantages.At present,slip form construction technology is becoming mature so much and widely used,and some of them have strict requirements for the flatness of concrete surface;In the 2022 Beijing Winter Olympic Games,the skiing project will be carried out in Chongli,Zhangjiakou.It is required that the linear construction and surface flatness of the ski path should reach millimeter accuracy.Under the above two backgrounds,the mix proportion design of slip form concrete is carried out by means of physical test,which provides a reference for the sliding time of formwork in slip form construction and a basis for the workability of concrete in the later test of this subject;The relationship between vibration acceleration,vibration viscosity coefficient and vibration liquefaction of concrete under vibration,and the influence of vibration liquefaction of concrete on density and formwork flatness of concrete are studied.The main research contents of this subject are as follows:(1)Through the orthogonal experimental study with the water binder ratio,fly ash,early strength agent and water reducer as the parameters,it is found that the growth rate of concrete strength changes from fast to slow,and the change is most obvious at about 7 days.The influencing factors of concrete 7d strength are as follows:early strength agent > water binder ratio > water reducing agent > fly ash;The influencing factors of 28 d strength are as follows: fly ash > water binder ratio > early strength agent > water reducer.(2)Under the action of the vibrating rod,it is found by changing the distance between the vibration acceleration sensor and the vibrating rod in the concrete and the measured acceleration value of the slump of the concrete.At a certain distance,the maximum value of concrete vibration acceleration increases from zero,and it appears stable after vibration for a period of time,does not continue to increase with the increase of time,and the concrete reaches a stable vibration liquefaction state;When the distance increases,the maximum value of concrete vibration acceleration decreases with the increase of distance;According to the minimum vibration acceleration of concrete reaching vibration compaction,it is calculated that when the slump of concrete with the same mix proportion is 0 ～ 20 mm,20mm～ 40 mm and40mm ～ 66 mm respectively,the spacing of vibrating rods is 22.2cm,25.8cm and27.6cm respectively.(3)The vibration viscosity coefficient of concrete is measured by balloon method(instead of table tennis).By changing the water binder ratio,cement content,fly ash content,slump and the distance between the measuring point and the vibrating rod,it is found that,The vibration viscosity coefficient of concrete decreases with the increase of water binder ratio and cement content,and there is an obvious linear relationship between them;When the maximum content of fly ash is 30%,the vibration viscosity coefficient of concrete decreases;The influence degree of the first three factors on the vibration viscosity coefficient from high to low is: water binder ratio,cement dosage,fly ash dosage;The effective radius of the vibrating rod has a greater influence on the vibration viscosity coefficient than the water glue ratio.The smaller the slump of concrete,the longer the time required for vibration and compaction.(4)By measuring the flatness and alignment of the auxiliary slideway model of the Winter Olympic Games poured with the slip form construction technology,it is found that the average value of the difference between the measured elevation and the design elevation is less than or equal to 3.6mm,and the measured alignment of the auxiliary slideway model coincides with the design thread,It shows that by improving the vibration liquefaction performance of concrete,the linear construction of auxiliary slideway and the accuracy of surface flatness of MM can be achieved. |
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