Experimental On Monitoring Early-age Strength Of Slag Concrete Based On A New Dual Piezoelectric Transducer

The electro-mechanical impedance(EMI)technique provides a new alternative for monitoring the compressive strength gain of concrete since the conventional nondestructive detection techniques have many limitations.In recent years,research on monitoring the concrete strength based on EMI has become more and more in-depth and the results of monitoring within concrete curing process show satisfactory.Based on dual piezoelectric transducer,this paper designed a new piezoelectric transducer that could be embedded in the structure,and then embedded it in standard cubic of C25 slag concrete under standard curing conditions to monitor admittance data in 0-14 day,including the earlier age(the first 48 hour).The curvilinear relationship between the strength of the standard concrete cubic of C25 slag concrete and the admittance index(impedance phase angle amplitude)was established.Focus on the purpose,following works were carried on:Firstly,a new copper-based embedded piezoelectric sensor was designed and fabricated based on the dual piezoelectric transducer,and its admittance was continuously measured to determine its stability before being embedded.Secondly,the new piezoelectric sensor was embedded in standard cubic of C25 slag concrete under standard curing conditions,and its temperature and compressive strength were measured regularly.Then the strength value in earlier age(the first 48 hour)and the unmeasured time point in 2-14 day is calculated based on the maturity method,combined with the measured strength data in 2-14 day,a curvilinear relationship between the cubic strength and the age was established.Finally,the admittance of the embedded piezoelectric sensor was measured in target ages,including the earlier age(the first 48 hour).Then the change of the admittance curve with age was analyzed and the impedance phase angle amplitude index was calculated.combining the strength data at the earlier age(the first 48 hour)calculated by the maturity method and the measured strength in 2-14 day,fitting analysis was carried out.A curvilinear relationship between the strength and the admittance index was established.This thesis establishes a curvilinear relationship between the C25 slag concrete strength and impedance phase angle amplitude index in early age,which provides the possibility to accurately predict concrete strength in early age,especially the extremely early age(0-48 hour).