Experimental Research On Freeze-thaw Cycle And Mechanical Performances Of PZT-based Smart Aggregates

The piezoelectric ceramics (such as PZT) sensors have been widely used in the recent yearsin structural health monitoring (SHM) because of their advantages such as small size, fastresponse, low cost and easy construction, et al. For good serviceability, the PZT transducer wasusually embedded into a small volume of concrete named a smart aggregate (the SmartAggregate is referred to SA) to prevent it from environmental influence. The methods forpackaging and protection of the smart aggregates were discussed by scholars in the field, and alot of research fruits were successfully got. However, the research on the durability was less andrare research fruits were published at the preliminary stage. The freeze-thaw cycle performanceand compression and shear properties for the smart aggregate were experimentally developed inthe paper to validate its durability and serviceability at a cerytain of stress level.In this paper, an experimental research method was used and the main contents were asfollows:(1) The research background, purpose and significance, and paper review were firstlyintroduced, and the basic knowledge of smart materials and their wide application of the smartaggregates were also briefly introduced.(2) The freeze-thaw cycle tests for the smart aggregate were performed. By referring to thenational standards of concrete freeze-thaw cycle test, a test method of freeze-thaw cycle researchfor the PZT-based smart aggregates were developed. The maximum and minimum temperaturesfor the test were20℃and-20℃, respectively. After20cycles of the test, the waveform of thesmart aggregate was measured and analyzed by using a sine wave of diagnosis signal todetermine the change due to the freeze-thaw cycle. The results showed that this new type ofpiezoelectric ceramic sensors named smart aggregate can still accept and launch signals normallyin a certain number of freeze-thaw cycles.(3) The compression and shear tests for the smart aggregates were performed, respectively.The test was performed in a test machine with100kN of force stroke to examine the mechanicalperformance of the smart aggregates. The failure process of the samrt aggregate was monitoredon line by the acoustic emission technology during the compression and shear process. Theresults showed that the demension of the PZT size in the smart aggregates was the primary factorwhich can affect its compressive and shear capacity.(4) The main work was summarized at the end and some conclusions were made, and thefuture research contents were also recommended.