Issue 46

J. Liu et alii, Frattura ed Integrità Strutturale, 46 (2018) 352-360; DOI: 10.3221/IGF-ESIS.46.32 359 (3) The damage variable is less than 1 indicating that the damage is very small randomly distributed before 30% of the peak load. The loading-damage curve increases steadily between 30% and 80% of the peak load, indicating that the damage is orderly changed. When the load reaches 80% of the peak load, the damage variable increases sharply, and the test specimen fails at this stage. The load-damage curve shows the whole failure process consistent with the load-pore volume curve. (4) The rapid increment of the pore volume, porosity and damage variable can be regarded as the destroy of concrete test specimens, therefore, the phenomenon can be a sign of the destroy in concrete. A CKNOWLEDGEMENTS his paper is supported by the Key Fund Project program sponsored by the Education Department of Hebei Province (ZD2014073). Tremendous thanks to several colleagues and graduate students for their support during the various stages of the work summarized here. R EFERENCES [1] Dang, F.N., Lei, G.y. and Ding, W.H. (2015). Study on the CT meso-test experiment of static and dynamic failure processes of concrete, Journal of Hydroelectric Engineering, 34(1), pp. 189-196. [2] Liu, M.J., Zhao, J. and Wang, G.W. (2014). Microscopic study of damage in carbonated concrete based on computerized tomography, Journal of Guangxi University: Nat Sci Ed., 39(1), pp. 187-193. [3] Liu, J.H., Jiang, Y.D. and Zhao, Y.X. (2012). Fractal Description of Coal Damage Process Based on CT Image, Journal of Beijing Institute of Technology, 32(12), pp. 1219-1222. [4] Bossa, N., Chaurand, P. and Vicente, J. (2015). Micro-and nano-X-ray computed-tomography: A step forward in the characterization of the pore network of a leached cement paste, Journal of Cement and Concrete Research, 67, pp. 138- 147. [5] Kocur, G.K., Saenger, E.H. and Vogel, T. (2010). Elastic wave propagation in a segmented X -ray computed tomography model of a concrete specimen, Construction and Building Materials, 24(12), 2393 -2400. [6] Mao, L.T., Sun, Q.W. and Yuan, Z.X. (2016). Crack and strain field analysis in the concrete under uniaxial compression based on CT images, Journal of Building Materials, 19(3), pp. 449-4555. [7] Tekin, I., Birgul, R. and Yaman, I.O. (2015). Monitoring macro voids in mortars by computerized tomography method, Journal of Measurement, 63, pp. 299-308. [8] Lockner, D. (1993). The role of acoustic emission in the study of rock fracture, Int. J. Rock Mech. Min. Sci., 30(7), pp. 883-899. [9] Lai, Y.S., Xiong, Y. and Cheng, L.F. (2015). Study of Chatacteris of Acoustic Emission During Entire Loading Tests of Concrete and Its Application, Journal of Building Materials, 18(3), pp.380-386. [10] Wang, J.Y., Dewanckele, J. and Cnudde, V. (2014). X-ray computed tomography proof of bacterial-based self-healing in concrete, Journal of Cement & Concrete Composites, 53, pp. 289-304. [11] Morgan, I.L., Ellinger, H. and Klinksiek, R. (1980). Examination of concrete by computerized tomography, ACI Journal, 77(1), pp. 23-27. [12] Chotard, T.J., Boncoeur-Martel, M.P. and Smith, A. (2003). Application of X-ray computed tomography to characterize the early hydration of calcium aluminates cement, Cement & Concrete Composites, 25(1), pp. 145-152. [13] Lawer, J.S., Keane, D.T. and Shah, S.P. (2001). Measuring three-dimensional damage in concrete under compression, ACI Materials Journal, 98(6), p. 465-475. [14] Wong, R.C.K. and Chau, K.T. (2004). Estimation of air void and aggregate spatial distributions in concrete under uniaxial compression using computer tomography scanning, Cement and Concrete Research, 35, pp.1566-1576. [15] Ding, W.H., Chen, H.Q. and Zhang, J.J. (2006). X Ray CT observation on the fracture process under high strain rate, Journal of architectural structure, (S2), pp. 758-762. [16] Wu, L.Q. (2006). The meso scale test research on concrete under uniaxial compression, Nan Ning: Guang Xi University. [17] Liu, H.K. and Li, J. (2014). Nonlocal meso damage model in concrete under uniaxial tension, Journal of Tongji University (Natural Science Edition), (2), pp. 203-209. [18] Mao, L.T., Lian, X.Y. and Hao, L.N. (2014). Fractal calculation of 3D cracks based on digital volumetric images and its application, Journal of China University of Mining & Technology, 43(6), pp. 1134-1139. T