Monitoring Of Early Strength And Elastic Modulus Of Concrete Based On Piezoelectric Smart Aggregate

In this paper,the wave propagation analysis technology of embedded piezoelectric smart aggregate is used to measure the early signal response of concrete cube test block under different excitation signals,and it is compared with the compressive strength and static elastic modulus measured by pressure loading test.A method for monitoring the early strength and dynamic elastic modulus of concrete is proposed,and the calculation formula of static elastic modulus of concrete at different ages is derived.The research work of this paper mainly includes the following aspects :(1)A new type of piezoelectric smart aggregate was made with PPR tube as the protective shell and steel sheet as the upper and lower cover plate to monitor the impact load of concrete structure.The production process and process of piezoelectric smart aggregate were introduced in detail,and the sensitivity calibration was carried out by force hammer impact test.The test results show that the output voltage of piezoelectric smart aggregate under different impact pressures has good stability and linear response characteristics,which can effectively reflect the impact load of concrete structure.(2)Four groups of concrete test blocks with different mix ratios were prepared,some of which were embedded with piezoelectric smart aggregates.On the one hand,the early compressive strength of ordinary concrete blocks was measured by pressure loading test.On the other hand,the early response signal of the piezoelectric smart aggregate test block was monitored by the wave propagation analysis test.Then the correlation between the compressive strength and the response signal was analyzed.The results show that there is a good linear relationship between the compressive strength ratio and the energy ratio of the response signal for concrete with different strength.(3)By collecting the research data in many literatures,the prediction models between compressive strength and static elastic modulus of concrete proposed in different literatures are compared and analyzed,and the most suitable prediction model for this study is selected.According to the model,the static elastic modulus of concrete test blocks under different mix ratios and ages is calculated.The optimal excitation method of using piezoelectric smart aggregate to monitor the early dynamic elastic modulus of concrete specimens was determined by numerical simulation.Based on this method,a detailed experimental study was carried out,and the amplitude,wave velocity and energy signal of concrete under different state characteristics were discussed(4)The dynamic elastic modulus of concrete is measured by piezoelectric smart aggregate,and compared with the static elastic modulus obtained by uniaxial compression test.The influence of water cement ratio,aggregate size and age on the correlation between them is studied.The conversion relationship between dynamic elastic modulus and static elastic modulus of concrete based on piezoelectric smart aggregate monitoring is established.The effective monitoring of early dynamic elastic modulus of concrete block by piezoelectric smart aggregate is realized,which provides a new method for health monitoring of concrete structure.