Experimental Research On Fly Ash Concrete Strength Monitoring Based On Piezoelectric Sensor

Engineering practice shows that the strength control of concrete structure has an important influence on the construction process.Although the construction progress of the structure is fast,the demolition of the formwork and the climbing of the formwork require the concrete to reach the design strength before proceeding.Otherwise,cracks will occur in the structure,which will increase the cost of maintenance and reinforcement in the later stage,and cause serious safety accidents in severe cases.Therefore,real-time monitoring and evaluation of concrete strength is of great significance to building construction.Aiming at the limitations of traditional strength detection technology,piezoelectric impedance technology provides a new way of thinking for concrete strength detection,and the real-time online monitoring of the strength of concrete curing process also shows satisfactory results.Based on piezoelectric ceramics(PZT-5),a mortar based piezoelectric sensor was made,and its temperature sensitivity was tested.It was embedded in concrete cube specimens,and the admittance monitoring was carried out on 0%,20%,40%,60% fly ash concrete at 0-60 days of age,with the measured compressive strength for comparison.The relationship between strength of fly ash concrete and admittance index was established.The main research achievements of this paper are as follows:(1)The performance of the embedded piezoelectric sensor made of mortar outer cladding is stable,and it is well combined with the target specimen during the strength monitoring process.At the same time,it is significantly affected by temperature,and the quantitative analysis of the influence of the admittance curve resonant peak height difference and frequency shift on temperature is carried out.(2)Using an appropriate amount of fly ash to replace the amount of cement can not only save resources,but also greatly increase the strength of concrete in the later stage.Using the Exp Dec2 exponential function model can accurately fit the concrete strength growth curves of four groups of different fly ash content.(3)The change of the admittance curve has a certain correlation with the strength development law.With the increase of the concrete strength,the piezoelectric sensor is strengthened by the binding effect,and the resonance peak of the curve basically shows a downward and rightward trend.The heat effect is more obvious,and the resonance peak is leftshifted and floating.(4)The concrete admittance data was processed and analyzed with RMSD and CCD indexes,and the conductance RMSD index in the excitation frequency range of 30-200 k Hz was determined to be the most sensitive to the process of concrete strength gain,and the change trend was in line with the development law of concrete strength.At the same time,the Exp3P2 exponential function is used to fit and analyze the error between the temperature-corrected RMSD and strength data.The results prove the effectiveness and feasibility of monitoring the strength of fly ash concrete based on piezoelectric sensors.