Experimental Investigation On Coarse Aggregate Size And Specimen Size Effect Of Nano-concrete Based On Acoustic Emission Technique

Compared with other NDT methods, acoustic emission detection technique has the advantages of real-time, dynamic and easy, these features make the acoustic emission technique has been widely applied in the evaluation of materials performance and structure or component damage detection. Acoustic emission technique is applied to study plain cement concrete has a history of decades, and has gotten some encouraging research results, but the acoustic emission technique is applied to study nano-concrete is rarely reported. This paper based on acoustic emission detection technique, studied the compression strength and acoustic emission characteristics of concrete specimens with1.5%content of nano-SiO2under uniaxial compression, and verified the Ohtsu model and Dai model. The main contents are as fellows:(1) Based on acoustic emission detection technique, the uniaxial compression test of five groups nano-concrete cubic specimens with maximum coarse aggregate size are9.5mm,13.2mm,16mm,19.5mm and26.5mm, studied the compressive strength and acoustic emission characteristics of nano-concrete specimens with different maximum coarse aggregate size. The results shown that the incorporation of nano-SiO2can improve the compressive strength of the concrete, and the compressive strength increased with the increase of the maximum coarse aggregate size, when the maximum coarse aggregate size is16mm, the compressive strength is the highest, then the compressive strength tends to a stable value with the increase of the maximum coarse aggregate size; the acoustic emission activity of nano-concrete decreased with the increase of the maximum coarse aggregate size; acoustic emission source can be divided into three types, which are caused by the destruction of interfacial transition zone, hardened cement paste and coarse aggregate.(2) Based on acoustic emission detection technique, the uniaxial compression test of three groups nano-concrete cubic specimens with size are100mm,150mm and200mm, studied the compressive strength and acoustic emission characteristics of nano-concrete specimens with different size. The results shown that the compressive strength of nano-concrete decreased with the increase in the size, and the size effect of compressive strength of nano-concrete is weaker than plain cement concrete, the acoustic emission activity of nano-concrete decreased with the increase in the size. (3) Used the test data to verify Ohtsu model and Dai model which are about mechanical parameter and acoustic emission parameter of concrete with Matlab software, and pointed out that, to the nano-concrete, Dai model is more suitable.