NUMERICAL STUDY OF CARBONATION DEPTH DETECTION OF CONCRETE DAMAGED FROM ULTRASONIC AXYSIMMETRIC LOADING USING REFLECTIVE WAVES

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1 Surabaya, 11 Juli 212, ISSN NUMERICAL STUDY OF CARBONATION DEPTH DETECTION OF CONCRETE DAMAGED FROM ULTRASONIC AXYSIMMETRIC LOADING USING REFLECTIVE WAVES IFTA MINKA 1,2, TA-PENG CHANG 2, DATA IRANATA 1 1 Department of Civil Engineering, Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia, Department of Construction Engineering, National Taiwan University of Science and Technology (NTUST), Taipei, Taiwan, 16 ifta.minka@yahoo.co.id, tpchang@mail.ntust.edu.tw, data_iranata@yahoo.com Abstract- Concrete exposed to environment, such as urban and industrial site, were easily attacked by either aggressive agents or reactive agents. One of the major and unavoidable concrete deterioration was carbonation. Generally, carbonation depth detection was measured using chemical phenolphthalein solutions 1%. However, from the previous experiment conducted by Y. Lo and H. M. Lee (21), it was known that phenolphthalein could not give the significant result again. In this investigation, the numerical analysis conducted using the commercial finite element software LS-DYNA 97. It is used to simulate the 2-D plate 1 x 2 mm with difference acoustic impedance (Z) subjected to ultrasonic axysimmetric loading. The signal resulted from numerical simulations were analyzed using reflective waves. Reflective waves as a filter to measure the depth of concrete carbonation damaged. Numerical results show that accuracy of depth detection depends on the impedance (Z) value of material. Measurement of carbonation depth could be detected with accuracy under 3%. Keywords- numerical, carbonation depth, ultrasonic, reflective waves 1. INTRODUCTION Concrete as a widely used material for construction must resist from some aggressive agents or reactive agents. Carbonation of concrete is one type of concrete deteriorations which are able to deliver corrosion of reinforced bars and change the characteristic of concrete material properties. Generally, the Manajemen dan Rekayasa Struktur C-47

Surabaya, 11 Juli 212, ISSN 231-6752 traditional detection method of concrete carbonation was conducted by traditional measurement using phenolphthalein 1% solution.

2 Surabaya, 11 Juli 212, ISSN traditional detection method of concrete carbonation was conducted by traditional measurement using phenolphthalein 1% solution. From the previous research conducted by Y. Lo and H. M. Lee (21) [1], it was known that the phenolphthalein test did not indicate a significant result. Moreover, the carbonation detection using phenolphthalein is not an in-situ carbonation detection method. Ultrasonic wave propagation is one of non-destructive method for concrete damaged detection. Reflection wave method is one of ultrasonic method that usually been used as a tool to identify and detect the thickness/depth of concrete cracks [2, 3]. Therefore, in this study, reflection method will be used to identify the depth/thickness of carbonation damaged of concrete. 2. METHODOLOGY Numerical simulation is conducted using commercial finite element software LS-DYNA 97. Geometry of finite element model is a concrete element of 1 mm height 2 mm length. It is used to simulate the carbonation condition of concrete subjected to ultrasonic loading using 2-D axysimmetric elements. The element mesh size is mm. The material properties including Young s Modulus (E), density (ρ) and Poisson s ratio (ν) of concrete are presented in Table 1. Hence, simulation model is presented in Figure 1. Table 1 Material properties of simulation model No. Material 1 Acoustic Material 2 Acoustic C p1 C p2 Control E 1 P 1 Impedance E 2 P 2 Impedance v (Gpa) (kg/m 3 1 v ) (m/s) (Z 1 ) (GPa) (kg/m 3 2 ) (m/s) (Z 2 ) Z 1 /Z Figure 1 Model of numerical simulation with the thickness of carbonation is 16 mm The basic procedure of this research is determining the depth (thickness) of carbonation damaged from the ultrasonic signals products. The thickness was calculated using reflected wave method based on the value of internal P-wave velocity, C p, as presented in the following expression [4]: (2-1) where T is thickness (m), C p is the P-wave (m/s), t 1 and t 2 are the occurring times correspond to the amplitude A 1 and A 2, respectively. Calculation of estimation time Manajemen dan Rekayasa Struktur C-48

Surabaya, 11 Juli 212, ISSN 231-6752 travels was obtained using similar equation as (2-1), presented in the following equation: (2-2) 8E-6 6E-6 4E-6 2E-6-2E-6-4E-6 (b) Results of numerical simulation

3 Surabaya, 11 Juli 212, ISSN travels was obtained using similar equation as (2-1), presented in the following equation: (2-2) 8E-6 6E-6 4E-6 2E-6-2E-6-4E-6 (b) Results of numerical simulation with Z 1 /Z 2 =.2 6E-6 Figure 2 Time travels from first layer and second layer of carbonated concrete Figure 2 above shows that t 1 and t 2 are time traveling at first layer, while t 3 is time traveling at second layer. 4E-6 2E-6-2E-6-4E-6 3. RESULTS Numerical simulations using ultrasonic loading were conducted on carbonated and un-carbonated concrete model to obtain signals and carbonation damage (i.e. thickness) of concrete. Figure 3 shows the signals output from LS DYNA. Detection of carbonation thickness was shown in Table 2. 6E-6 (c) Results of numerical simulation with Z 1 /Z 2 =.3 4E-6 2E-6-2E-6-4E-6 (d) Results of numerical simulation with Z 1 /Z 2 =.4 3E-6 4E-6 2E-6 2E-6 1E-6-2E-6-1E-6-4E-6-2E-6 (a) Results of numerical simulation with Z 1 /Z 2 =.1 (e) Results of numerical simulation with Z 1 /Z 2 =.5 Manajemen dan Rekayasa Struktur C-49

4 Surabaya, 11 Juli 212, ISSN E-6 8E-7 1E-6-1E-6 4E-7-4E-7-2E-6-8E-7 (f) Results of numerical simulation with Z 1 /Z 2 =.6 2E-6 (j) Results of numerical simulation with Z 1 /Z 2 = 1. 8E-7 1E-6-1E-6 4E-7-4E-7-2E-6 (g) Results of numerical simulation with Z 1 /Z 2 =.7-8E-7 1.5E-6 1E-6 (k) Results of numerical simulation with Z 1 /Z 2 = 1.1 8E-7 5E-7-5E-7-1E-6-1.5E-6 (h) Results of numerical simulation with Z 1 /Z 2 =.8 4E-7-4E-7-8E-7 1.2E-6 8E-7 (l) Results of numerical simulation with Z 1 /Z 2 = 1.2 6E-7 4E-7-4E-7-8E-7 4E-7 2E-7-2E-7-1.2E-6 (i) Results of numerical simulation with Z 1 /Z 2 =.9-4E-7-6E-7 (m) Results of numerical simulation with Z 1 /Z 2 = 1.3 Manajemen dan Rekayasa Struktur C-5

5 Surabaya, 11 Juli 212, ISSN E-7 3E-7 2E-7 2E-7-2E-7 1E-7-1E-7-4E-7-2E-7-6E-7 (n) Results of numerical simulation with Z 1 /Z 2 = 1.4 4E-7-3E-7 (r) Results of numerical simulation with Z 1 /Z 2 = 1.8 3E-7 2E-7-2E-7 2E-7 1E-7-1E-7-2E-7-4E-7 (o) Results of numerical simulation with Z 1 /Z 2 = 1.5 4E-7-3E-7 (s) Results of numerical simulation with Z 1 /Z 2 = 1.9 3E-7 2E-7 2E-7-2E-7 1E-7-1E-7-2E-7-4E-7 (p) Results of numerical simulation with Z 1 /Z 2 = 1.6 4E-7-3E-7 (t) Results of numerical simulation with Z 1 /Z 2 = 2. 1E-7 2E-7-2E-7 5E-8-5E-8-1E-7-4E-7 (q) Results of numerical simulation with Z 1 /Z 2 = E-7 (u) Results of numerical simulation with Z 1 /Z 2 = 3. Manajemen dan Rekayasa Struktur C-51

6 Surabaya, 11 Juli 212, ISSN E-8 4E-8-4E-8 depth detection, the highest first peak of each resulting signal could be neglected, if necessary. This condition is caused by that peak did not contain any information of reflected wave from surface that could be used -8E-8 to detect the depth of carbonation damaged. In reality, this peak comes from sensor that was (v) Results of numerical simulation with Z 1 /Z 2 = 4. Figure 3 Results of numerical simulation from LS-DYNA Table 2 Results of carbonation depth detection using reflected wave theory Original Calculated Arrival time No Z 1 /Z 2 depth depth error t 1 t 2 (m) (m) (%) E E E-5 3.4E E E E-6 2.4E E E E E E E E E E E E E E E E E E E E-6 1.8E E-6 1.4E E E E-6 9.7E E E E-6 1.3E E-6 1.1E E E E E used along detection. Even in the geophysics science, this highest first peak is a direct wave which is come from geophone [5]. Therefore, this peak could be neglected also in this detection. According to Table 2, it was known that accurate detection could be obtained at material with ratio of acoustic impedance (Z 1 /Z 2 ) higher than 1.1. Accurate detection in this study is detection which has an error of detection less than 3%. From Table 2, it was shown that double layer of carbonation model could be detected in the range of acoustic impedance ratio (Z 1 /Z 2 ) of This condition occurred because of acoustic impedance has big influence on the reflection and refraction/transmission of waveform. In the acoustic impedance theory, if Z 2 becomes very smaller than Z 1, A reflection approaches and 4. DISCUSSIONS Results of signal from numerical simulation using ultrasonic loading could be seen in Figure 4 and calculation of depth could be seen in Table 2. Figure 4 showed the resulting A refraction/transmission approaches zero. It means that the compressive wave and refraction will not occur [4]. In other words, attenuation from another signals occurred before the real reflected wave reaches the concrete surface. signal from different variations ratio of acoustic impedance (Z). In the analysis of Manajemen dan Rekayasa Struktur C-52

7 Surabaya, 11 Juli 212, ISSN CONCLUSIONS 1. Reflected wave theory could be applied to identify the thickness/depth of concrete damaged from ultrasonic testing with an error of detection under 3%. 2. Detection of carbonation damaged using reflected wave is accurate in material with ratio of acoustic impedance (Z) higher than 1.1. REFERENCES [1] Lo, Y., H. M. Lee (21), Curing Effects on Carbonation of Concrete Using a Phenolphthalein Indicator and Fourier-Transform Infrared Spectroscopy, Journal of Building and Environment, Pergamon. [2] Morishige, H. and Tanaka, S (24), Non-Destructive Inspection of Concrete Structures Using Ultrasonic Sensor, SICE Annual Conference in Sapporo, Hokkaido Institute of Technology, Japan. [3] Islam, Muhammed Mazharul. Yamamoto, Hiroya. Tanaka, Shogo, (26), Non-Destructive Inspection of Multiple Concrete Cracks Using Ultrasonic Sensor, SICE-ICASE International Joint Conference, Bexco, Busan, Korea, Oct [4] Boggess, Albert, (21), A First Course in Wavelets with Fourier Analysis, New Jersey, Prentice-Hall. [5] Sansalone, M. J and Streett, W. B., (1997), Impact Echo: Nondestructive Evaluation of Concrete and Masonry, Ithaca, New York, U.S.A, Bulbrier Press. Manajemen dan Rekayasa Struktur C-53

8 Surabaya, 11 Juli 212, ISSN Manajemen dan Rekayasa Struktur C-54

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