Concrete is the most widely used building material for civil structures. During the pouring process, the formation of secondary pouring interface in concrete is one of the most common problems, which may cause future structural damage and reduce the structural service life. It is desirable to develop a monitoring system that can detect the formation of secondary pouring interface in concrete structures. In this paper, an active sensing approach using piezoceramic based smart aggregates was developed detect the secondary pouring interface. Two smart aggregates function as the stress wave transmitter and receiver, respectively. Secondary pouring interface in concrete structure induces wave impedance mismatch, which attenuates the stress wave propagating through the interface. In this research, two concrete specimens, including one intact and other one with an artificial secondary pouring interface, were investigated. Compared to the intact concrete specimen, the energy of the signal received by the smart aggregate in the one associated with the secondary interface is much lower. A wavelet packet based energy analysis was used to compute the signal energy values to assist the detection. Experimental results demonstrated that the proposed approach can detect the formation of secondary pouring interface in concrete structures.
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