buildings in Sichuan with poor quality concrete [2] were seriously damage and collapse under the earthquake. After the Kobe Earthquake in 1995, seismic evaluations in Japan have found many existing RC buildings to have very low concrete strength (less than 13.5MPa) [3]. The poor quality concrete due to using very small size of poor quality aggregate was found as shown in Figures 1(b). The problem may be aggravated when reinforcement detailing is also poor in beam and column. Under an earthquake these main structures may seriously damage as shown in Figures 1(a).