Study on Acoustic Emission Characteristics of Self-Compacting Concrete under Uniaxial Compression Test

To study the relationship between acoustic emission characteristic parameters of self-compacting concrete(SCC) and its destruction evolution, under uniaxial compression, acoustic emission(AE) tests are performed on C30 selfcompacting concrete test blocks that are preserved for 7 days and 28 days, the corresponding relationship among energy, amplitude, ring count and different failure stages of the specimens are analyzed by AE experiment, and the spatial distribution of AE in each stage is described by introducing location map. The test shows that there are two rules for the failure of SCC specimens cured for 7 days and 28 days: (1) The first failure law is divided into four stages according to the percentage of the stress value reaching the limit stress: Initial stage: above 10%, the compaction time of test block cured for 28 days is relatively low; Elastic failure stage: 30%-35%, the cumulative value of each parameter increases linearly, and the cumulative value of the amplitude is the largest; Crack stable propagation stage: 35%-90%, there is a moment that causes local stress concentration in both test blocks; Active stage: above 90%, the cumulative value of the parameter rises sharply, then continues to load the test block instability and damage. (2) The second failure law is divided into five stages according to the percentage of the stress value reaching the limit stress: Initial stage: 15%-20%, the cumulative value of each parameter increases with time; Elastic failure stage: 20%-40%, the cumulative value of the parameter continues to grow, but the growth curve is approximately parallel; Crack stable propagation stage: 40%-60%, all parameters increased sharply and the increase reached the peak of the whole process; A stable state: 60-80%, the emission characteristic parameter will become zero, and the stable state of the 28 days curing test block is lagging; Active stage: above 90%, the number of signals increased sharply, but the energy and amplitude are low, and the later test block is completely fractured. (3) In the process of failure, the test block of SCC will form an inverted triangle or landslide failure surface, and the part above the failure surface is prone to failure, and there is a tendency to leave the test block. (4) Under uniaxial compression, the penetration of SCC cracks is mostly shear penetration.