Research On Monitoring Of Concrete Early-age Strength Based On Piezoelectric Wave Analysis Method

In recent years,concrete structures used as the most common forms are widely applied in the engineering construction.However,during the early-age or whole service,it would be inevitable to generate the issue of decrease of structure bearing capacity due to material quality problem.Therefore,the work of enhancing concrete strength monitoring has become an important topic which was paid an attention to in engineering and academic fields in the world.The structural health monitoring(SHM)technology based on piezoelectric ceramic has advantages of high sensitivity,fast response,sensitivity to damage,and non-destruction to the host structures,and more and more widely used in concrete structure health monitoring.The application of piezoelectric wave analysis technology based on piezoelectric ceramic in the civil structures has reached a more mature stage,but in addition to the structure damage detection,the study results on monitoring the curing process of concrete are less reported.Therefore,this dissertation will combine the PZT-based stress wave technology and concrete early-age theory to establish the relationship between the concrete early-age strength and the energy of the detection signals,and the research goal is to improve the on-line concrete early-age strength monitoring method based on the piezoelectric wave technology.The main research contents are described in the following:(1)Summarize the current research results and application of the SHM based on the piezoelectric ceramic in civil engineering,combining with the advantages and disadvantages of existing concrete strength detection technique,to propose the research purposes,contents,and methodology.(2)Verify the feasibility of the study purposes,focusing on the extraction of the signal parameters reflecting strength changes of concrete,and deduce the relationship between the signal energy and concrete strength values,and establish a monitoring strength physical model based on piezoelectric wave analysis method,to provide a theoretical basis for further research.(3)Use finite element simulation software ABAQUS/Explicit to conduct finite element analysis(FEA).The form of instantaneous displacement time history is applied to simulate the piezoelectric detection wave.The various displacement responses considering the change of the specimen cross-sectional dimension,the signal transmission distance,and frequency of the excitation signal are obtained,to provide a reference for the selection of valid signal frequency and specimen size in the later experimental stage.(4)Conduct the systematic experimental research,determine experiment monitoring index,and quantitatively study the relationship between concrete strength and the signal energy value.The smart aggregates with temperature monitoring function are embedded in the concrete specimens,and the signal energy monitoring test and concrete standard compressive strength test are conducted,respectively.(5)Apply MATLAB Curve Fitting Toolbox to conduct the fitting analysis of the test data,obtaining strength-energy fitting equations.According to the goodness of fit parameters,test data,and the engineering practical situation,the standard monitoring method is defined to obtain the fitting equation of strength percentage-energy ratio for commonly used concrete specimen.The equations can be used to monitor or predict the concrete early-age strength based on the piezoelectric wave analysis method.