Abstract
Post-tensioning (PT) system is widely used not only in bridge construction, but also used as a replacement of reinforced concrete (RC) structure for slab, beam, and wall. Nowadays, many countries around the world are focusing on sustainable development in the construction industry. PT system is one of a system which able to meet the standard of sustainable building construction. Its advantages are able to save more materials, construction time and maintenance cost. To ensure the safety of PT systems during construction, some methods are implemented to evaluate the concrete condition. In this study, the Rayleigh wave (R-wave) method is used to evaluate the grouting condition of the post-tensioned concrete structure. Useful parameters of R-wave such as amplitude, time, frequency and wave velocity are identified and obtained through a series of numerical simulations and experimental tests. Different frequencies are excited to examine the behavior of R-wave propagated through a concrete medium with different grouting conditions in the simulation. In experimental testing, different diameters of steel balls are used as an impactor to generate waveform and the generated waveforms were recorded by the data logger. Three equidistance receivers are placed on top of the tested concrete specimen with different duct materials of aluminium duct and PVC duct embedded in it. As a conclusion, when voids are present in the concrete specimen, high readings of amplitude and dominant frequency are recorded and the travelling wave velocity is slow.
Highlights
The post-tensioning (PT) system is a pre-stressing method that has been widely applied by many countries around the world to replace normal reinforced concrete (RC) structures
Post-tensioning concrete was cast with concrete first and the steel tendon wires will be entered through the ducts and stretched when the concrete had developed sufficient strength to stress resistance [2]
Grout will be used in post tensioned concrete structures as it is injected into a duct and bonds with the steel tendons to the surrounding concrete, forming an integral as a unit [3]
Summary
The post-tensioning (PT) system is a pre-stressing method that has been widely applied by many countries around the world to replace normal reinforced concrete (RC) structures. Post-tensioning concrete was cast with concrete first and the steel tendon wires will be entered through the ducts and stretched when the concrete had developed sufficient strength to stress resistance [2]. Grout will be used in post tensioned concrete structures as it is injected into a duct and bonds with the steel tendons to the surrounding concrete, forming an integral as a unit [3]. Steel tendons are critical reinforcing elements of post-tensioned structures, which will susceptible to corrosion, proper treatment and protection are needed on the grouting condition. Common failures of post-tension bridges are corrosion of steel tendons due to deficient grout including voids, moisture in ducts, porous grout, grout segregation, soft grout, carbonated grout and high chloride content grout [5]. Formation of voids will occur in the duct due to incomplete grouting, trapped air pocket, poor grouting procedure or bleeding of grout, corrosion will happen in the steel tendons and eventually, the steel tendons will fail to sustain the extreme loading, causing catastrophic of concrete member failure [6]
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