Compressive failure in concrete of recycled aggregate by acoustic emission

For recycling concrete, the use of recycled aggregate has been extensively studied in Japan. It is widely recognized that compressive strength in concrete of recycled aggregate is lower than normal concrete with the same water-to-cement ratio, because fracture process in concrete of recycled aggregate is not identical to normal concrete. In order to clarify characteristics of fracture process in aggregate-recycled concrete, acoustic emission (AE) technique is applied to detect micro-cracking in concrete under compression. A method to improve the strength of concrete of recycled aggregate was investigated. The test was performed under both monotonous and cyclic loadings. From AE parameters, it is found that cracking behaviors in concrete of recycled aggregate fairly differ from that of normal concrete. Still it is confirmed that the strength could be recovered by vibratory compaction.