Experimental Research On The Effect Of Driving Vibration On The Post-Poured PVA-ECC Tensile And Bending Properties Of Bridge Deck

PVA-fiber reinforced cement-based composites(PVA-ECC)as "an up-and-coming concrete",its excellent extension properties make it widely used on the bridge pavement.Usually,the repair of the bridge deck is carried out by using the method of half-pass and half-construction,and the vehicle-bridge coupling vibration is inevitable.This article researched the impact of bridge vibration caused by passing vehicles on the tensile and bending properties of freshly poured PVA-ECC using laboratory vibration equipment,and tested the pore structure parameters under different vibration parameters.The tensile properties,bending properties,and pore structure parameters were analyzed based on the experimental results in the different characteristics of the cement hydration process.The influence mechanism of vibration on the macroscopic mechanical properties of PVA-ECC was analyzed.The main conclusions of this article are:(1)Vibration has a great influence on the mechanical properties of PVA-ECC,and most situations are adverse effects.Vibration mainly affects its macroscopic mechanical properties through two aspects.Firstly,One hand,the vibration affects the pore structure in the course of hydration.And the degree of hydration thus affects the compactness and strength of the matrix,on the other hand,the vibration will destroy the skeleton structure formed by the cement particles during the coagulation process,thereby generating cracks and further affecting the strength of the matrix.Secondly,the vibration will also affects the distribution of the free water at the interface of the matrix and fiber.Thus the distribution affects the bonding strength of interface of the matrix and fiber.According to the cracking strength criteria and steady-state cracking criteria,the above two reasons are the main causes of the macroscopic mechanical properties of PVA-ECC.(2)Before starting the initial setting,the vibration with lower frequency has an adverse effect on the ultimate strength and elongation of the uniaxial tension.The maximum adverse effect is-19.4%.The vibration of the higher frequency has the favorable effect on ultimate strength of the uniaxial tension.The influence of the extension rate is favorable and the maximum impact degree is 18.15%.The degree of impact at this stage is not great.From the initial setting to the final setting stage,the vibration has a very unfavorable effect on the ultimate strength and elongation of the uniaxial tension.The degree of influence is obvious,reaching a maximum of-34.58%.After starting the final condensation,the vibration with lower frequency will have an adverse effect on ultimate strength and elongation.The maximum degree of adverse effect is-13.94%,and the degree of impact is not significant;the effect of vibration with higher frequency on ultimate strength and elongation is advantageous.The advantage is that the maximum impact is 34.60%,which has a significant impact.(3)The effects of different vibration durations on the uniaxial tensile properties from the initial setting to the final settling stage were studied.The results show that the effect of vibration on the strength gradually decreases with the increase of the frequency at this stage.The impact on the elongation is relatively increased.Similarly,the vibration starts at 8h after mixing with water.In the case of low vibration frequency(frequency 2 and 3Hz),the impact on uniaxial tensile properties is the most favorable when the vibration is lasted for 8h,in which the maximum intensity effect is 35.32.%,the maximum extent of influence of the elongation is 17.17%;and in the case of high vibration frequency,the impact on the uniaxial tensile performance is the most favorable when the continuous vibration for 5 hours.(4)The vibration frequency has a certain influence on the uniaxial tensile properties of PVA-ECC.The uniaxial tensile properties at vibration frequencies of 2Hz,3Hz,4Hz and 5Hz were analyzed.The results show that: with the increase of vibration frequency the ultimate tensile strength shows an increasing trend.When the frequency increases from 3 to 4 Hz,the increase of the ultimate tensile strength is fast,and at other frequencies the increase is gentle.In addition,contrast to the non-vibration group,the effects of vibration on the ultimate tensile strength,tensile strain,and volume energy are reduced at frequencies of 2 and 3 Hz.And at frequencies of 4 and 5 Hz,they are all increasing.(5)PVA-ECC apertures are mainly concentrated between 100 nm and 1000 nm,which are close to 1000 nm,and a few are distributed between 10 nm and 100 nm.Among them,the aperture on the intensity from 100 nm to 1000 nm plays a major role.On the other hand,the pores in this region account for most of the total pores.(6)The effects of start-up vibration on PVA-ECC pore structure parameters at different setting and hardening stages were compared and analyzed.The results show that there is an inverse correlation between ultimate tensile strength and porosity,pore volume fractal dimension and mean pore size,respectively.The vibrations at different start-up times affect the macroscopic mechanical properties,such as the ultimate tensile strength by affecting the porosity.From the perspective of the development trend of various parameters of the microscopic voids,the final setting time of PVA-ECC is 36 h.There is an exponentially positive correlation between the total pore area and the ultimate tensile strength.