Structural health monitoring and damage identification paper
Lim, YY, Majain, N, Kwong, KZ & Hsien Liew, WY 2014, 'On the study of concrete hydration process using piezoelectric based surface wave propagation technique', in ST Smith (ed.), 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23), vol. II, Byron Bay, NSW, 9-12 December, Southern Cross University, Lismore, NSW, pp. 1121-1128. ISBN: 9780994152008.
Concrete is a non-homogenous material with complex microstructure, consisting of cement, fine aggregates and coarse aggregates. In the first few hours after mixing, the fresh concrete will go through the hydration process and gradually reaches solid properties. Study shows that as the concrete changes gradually from liquid to solid, the properties such as stiffness of the concrete changes accordingly. Monitoring of concrete hydration is essential especially in in-situ construction. The concrete shall reach sufficient strength before further loading is possible. In this paper, attempt has been made to study the correlation between the velocity of surface (Rayleigh) waves and the concrete hydration process using the surface wave propagation technique employing smart piezoelectric (Lead Zirconate Titanate, PZT) transducer as collocated actuator and sensor. The PZT transducer is mechanically attached to the concrete through surface bonding. The velocity of surface waves was determined by measuring the distance between the actuator and sensor and also the time of flight (TOF). Preliminary study shows that there is a steady increase in the velocity of surface waves with time, implying that the concrete is going through a hardening process. Signal processing techniques such as cross-correlation analysis and Hilbert transform are adopted for improved accuracy.