Paving test equipment and methods of the hottest R

2022-08-22
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Roller compacted concrete (RCC) is a kind of super dry cement concrete without slump with low water content and less cement consumption, which can achieve high density and high strength through vibratory rolling construction technology. Due to the remarkable economic and social benefits of RCC pavement, many countries in the world are studying RCC pavement technology. Looking at the research results at home and abroad, it can be found that the problem of pavement flatness and compactness is still a recognized problem, and the lack of pavement flatness restricts the application of RCC pavement in high-grade highways. In order to solve this problem, it is necessary to develop an indoor roller compacted concrete pavement paving and forming test equipment, and use this equipment to carry out repeated and a large number of actual paving tests of roller compacted concrete pavement indoors, so as to study: (1) the influence of the vibration frequency of the screed of the RCC pavement paver, human amplitude A, the working frequency of the double tamping beam, FH, and the static pressure of the screed, Q, on the initial compactness, flatness and liquefaction slurry extraction effect of RCC pavement

(2) the influence of paving speed V on the initial compactness, flatness and liquefaction slurry extraction effect of RCC pavement; (3) The influence of mix proportion parameters of RCC mixture on the initial compactness, flatness and liquefaction slurry extraction effect of RCC pavement. 2 working principle of RCC pavement paving test equipment this topic has developed an indoor RCC pavement paving molding test equipment. The test equipment simulates the high-efficiency and strong compaction screed, adopts double tamping beams and fixed excitation system, and the vibration frequency, amplitude, static pressure, working frequency of tamping beam and paving speed of RCC pavement can be adjusted steplessly or step by step in a large range. The test equipment is installed in the Central Laboratory of engineering machinery, Department of road construction engineering machinery, Xi'an Highway and Jiaotong University. In order to facilitate the simulation of the working process of RCC pavement paver and RCC pavement in the laboratory, the first suction is direct acting coal, and the multi-month layer connected textile base platform moves horizontally, while the working device of the paver does not move. The basic structure diagram of the test equipment is shown in Figure 1

1. movable subgrade platform 2. Winch 3. Material retaining plates on both sides 4. Forced mixer 5. Metering ram 6. Virtual paving height control inclined plate

7. Guide plate 8. Tamping beam 9. Screed box 10. Eccentric vibration exciter 11. Elevation adjusting screw 12. Traction boom

13. Lifting hydraulic cylinder 14. Hydraulic system 15. Tension sensor 16. Control cabinet 17. The hydraulic company has recently formulated and released 2018 major short board equipment project guidelines with Zhuhai Development Zone The plastic drag friction and wear experimental machine is mainly composed of the experimental server and the intelligent automatic control system. The South Management Committee signed a cooperation framework agreement. Considering that there are too many materials used for RCC pavement, the RCC pavement forming width on the test equipment is set at 1.5m and the length can reach 5m. The test can be repeated many times. The working principle of the test equipment is: ① calculate the amount of each component in the RCC mixture according to the mix proportion, weigh each component with a scale and pour it into the hopper of the mixer (in which the water is directly poured into the mixing tank during mixing); ② After being stirred by the concrete mixer for 3 minutes, it is unloaded on the movable subgrade platform. With the forward and backward movement of the subgrade platform (under the traction of the winch), the concrete is scraped by the metering RAM (supplemented by manual scraping). After passing through the virtual paving height control inclined plate, the virtual paving height of loose concrete meets the requirements; ③ The movable subgrade platform advances forward (i.e. to the right) at the given paving speed V, and the concrete first enters under the double tamping beam after passing through the guide plate. The tamping beam tamps the concrete Z with the given working frequency and fixed amplitude ④ the concrete enters under the screed box, and the screed box vibrates on the concrete surface with the given vibration frequency f and amplitude A under the action of the vibrator, and the concrete is vibrated; ⑤ After the screed, the RCC pavement is compacted and formed; ⑥ The area of the two pieces is 140cm × The 55cm compacted RCC pavement plate together with the steel plate at the bottom is lifted and moved to another place for sampling; ⑦ Clean the movable subgrade platform and prepare for the next test. 3 performance parameters and measurement methods of the test equipment (1) adjustment and measurement of paving speed V the movable subgrade platform is pulled by the winch, which is driven by the hydraulic immediately selected drilling plastic speed generator, and the calculation is controlled by the electronic speed regulating valve in the hydraulic system, The moving speed (i.e. paving speed V) of Huaibei City's efforts to build and cultivate an aluminum based new material industry platform can be changed steplessly within the range of 0.3-10.0m/min. During the test, the average paving speed can be measured with a stopwatch. (2) Adjustment and measurement of screed vibration frequency/and amplitude A in order to make the screed box vibrate on the surface of RCC mixture according to the required vibration frequency and nominal amplitude A, an eccentric exciter is installed on the upper plane of the screed box. The exciter adopts a directional excitation mode, that is, the two excitation shafts with eccentric blocks of the exciter rotate synchronously in reverse, the lateral components of the centrifugal force offset each other, and the vertical components are twice that of a single shaft, Therefore, the screed box only vibrates in the vertical direction. The exciting shaft of the eccentric vibration exciter is driven to rotate by the hydraulic motor. Through the control of the speed of the hydraulic motor by the electronic speed regulating valve in the hydraulic system, the vibration frequency f of the screed can be steplessly adjustable in the range of 10-60hz. By changing the eccentric mass moment of the eccentric exciter, the nominal amplitude A of the screed can be changed, and the amplitude A is adjustable in the range of 0.1 ~ 12mm. During the test, an acceleration sensor is installed in the center of the upper plane of the screed to measure the actual vibration frequency f and vibration acceleration a of the screed. (3) The adjustment and measurement of the working frequency name of the double tamping beam. The double tamping beam is installed on the screed box wall, and the eccentric shaft of the tamping beam is driven to rotate by the hydraulic motor. The speed of the hydraulic motor is controlled by the electronic speed regulating valve in the hydraulic system, so that the working frequency FH of the tamping beam can be steplessly adjusted within the range of 10-40hz. Installing an acceleration sensor above the tamping beam can easily measure the actual working frequency FH of the tamping beam

(4) measurement of paving resistance f a blr-l type tension sensor (see Figure 1) is connected in series between the movable road panel and the steel wire rope of the winch, which can measure the working device of the paver

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