Evaluation of Grouting Condition of Post-Tensioned Concrete using R-wave MethodKah Kian Cheong, Foo Wei Lee, Kah Hon Leong, Ming Kun Yew and Yee Ling LeeE3S Web Conf., 65 (2018) 02004DOI: https://doi.org/10.1051/e3sconf/20186502004