Internal Defects Detection And The Strength Evaluation Methods Of Fresh Concrete After Earthaquake

5.12 WenChuan Earthquake has caused different damages on the civil engineering structures in disaster area. When the earthquake shocked, a lot of the constructions in progress were at different stages. So to test and appraise the damaged condition of the concrete structures has become very important. The treatments are not only too conservative to cause unnecessary waste, but also able to guarantee the safety of the people's life and property. To the existed concrete of structures,it can be tested and appraised by the indexs of deformation,crack,strength to decide how to deal with the structures.However,especially to the short-term concrete, whether the strength influenced by the earthquake is still up to the standard and whether the existed undestroyed evaluation methods of concrete compressive strength are also applicable, there is no forthcoming experiences to follow. It is a new subject at home and abroad.Based on the related research achievements of undestroyed testing method, this paper aims at finding a undestroyed evaluation method to evaluate the compressive strength of the fresh concrete suffered by the earthquake vibration. Experiments on the large-scale seismic simulation table and a series of tests were held to investigate the internal defects condition, the compressive break mechanism and the effects to the sound wave parameters of the fresh concrete. The main conclusions are as follows:1. The results of the large-scale seismic simulation experiment demonstrate that there is no obvious internal defects in the fresh concrete suffered 6-9 seismic degree vibration. And the differences of sound wave parameters between the shaken fresh concrete and unshaken ones are tiny. Besides, the compressive broken process are similar following the same rules.2. The application of two undestroyed evaluation methods make differences in the accurancy.For the two kinds of concrete strength degree C30 and C50,the inaccuracy of the rebound method can meet the requirements, So this evaluation method are still applicable to the fresh concrete suffered by simulation earthquake.However, compared to former method the ultrasonic-rebound combined method surpass the error index standard seriously.Therefore,some modification must be made to this kind of method.3. Suggestions on improving the accuracy of the evaluation methods are also given in this paper. Utilizing one-dimensional linear and dualistic regression means to establish special strength curves according to different concrete degree can improve the evaluation accuracy in some contents. Furthermore, some referenced advices are provided on how to handle the fresh concrete suffered by earthquake, and to some extent can also be used as the theoretical basis for the subsequent study on relevant subjects.4. According the results of this paper, the problems that need to lucubrate in the further research on this subject are raised at the end.