COMPARATIVE ANALYSIS OF PHENOLPHTHALEIN INDICATOR, XRDA AND FTIR METHODS FOR MEASUREMENT OF CARBONATION DEPTH OF CONCRETE

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International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 5, May 2018, pp. 315 320, Article ID: IJCIET_09_05_035 Available online at http://www.iaeme.com/ijciet/issues.asp?

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 5, May 2018, pp , Article ID: IJCIET_09_05_035 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed COMPARATIVE ANALYSIS OF PHENOLPHTHALEIN INDICATOR, XRDA AND FTIR METHODS FOR MEASUREMENT OF CARBONATION DEPTH OF CONCRETE Alok Ranjan Research Scholar, Department of Civil Engineering, IIT (BHU), Varanasi, India Rajesh Kumar Professor, Department of Civil Engineering, IIT (BHU), Varanasi, India Devendra Mohan Professor, Department of Civil Engineering, IIT (BHU), Varanasi, India ABSTRACT Carbonation in concrete demands prime concern as it is a major deteriorating factor in concrete structures in our surroundings. The accurate determination of impact of carbonation in concrete is still a challenge. The naturally occurring carbonation process in our environment is extremely slow. Hence in order to analyze the effect of carbonation in concrete in concise duration, an accelerated carbonation chamber is required to increase the rate of carbonation under given parameters for experimental purpose. Phenolphthalein indicator methods by far the most conventional method of determination of depth of carbonation in concrete, being most economic and quick. However, it does not provide accurate results with respect to carbonation depth. This paper presents an experimental study of carbonation effect of concrete by advanced methods such as XRDA and FTIR methods. The process of carbonation has been carried out in an accelerated carbonation chamber under controlled environmental conditions using ordinary Portland cement (OPC) concrete at Water/cement (W/C) ratio 0.4, 0.45 and 0.5. Study shows that carbonation depth obtained from advanced methods is greater than that obtained from conventional method and that the carbonation depth increases with the increase of W/C. Keywords: Carbonation, Phenolphthalein, FTIR and XRD method and OPC Cite this Article: Alok Ranjan, Rajesh Kumar and Devendra Mohan, Comparative Analysis of Phenolphthalein Indicator, Xrda and Ftir Methods for Measurement of Carbonation Depth of Concrete, International Journal of Civil Engineering and Technology, 9(5), 2018, pp editor@iaeme.com

2 Alok Ranjan, Rajesh Kumar and Devendra Mohan 1. INTRODUCTION Most researchers [1] use phenolphthalein indicator to assess the carbonation depth. However, other methods of experiment such as X-ray diffraction analysis (XRDA) and Fourier transformation infrared spectroscopy (FTIR) method have been successfully used by many other researchers. In this paper results of experiment by each of the above three experimental procedures have been documented. Also, a comparative study between the different methodologies has been drawn to establish the effectiveness of advanced methods over the conventional method. Lo and Lee [2] concluded that carbonation rate constants obtained from Infrared spectrum analysis was 23.9% higher than that determined by phenolphthalein indicator. Similar study was done by Chang et al. [3] and he concluded that carbonation front from TGA, XRDA and FTIR methods was on an average twice that determined with the phenolphthalein indicator. 2. MATERIALS AND METHODS 2.1. Materials Ordinary Portland cement (OPC), conforming to Indian Standard (IS) have been used in this experiment for research. Aggregates conforming to IS consisting of coarse aggregate of 10 mm and 20 mm nominal size and fine aggregate (sand) have been used Methodology Concrete blocks of 100 mm x 100 mm x 100 mm were taken for experimental purpose. 3 numbers of cubes were taken for each type of test. Each cubic sample was placed in the carbonation chamber after 3 days curing. Table 1 Mix design for OPC concrete OPC Concrete W/C Water (kg/m 3 ) Cement (kg/m 3 ) Sand (kg/m 3 CA-10 mm CA-20 mm ) (kg/m 3 ) (kg/m 3 ) Measurement of Carbonation Depth Using Phenolphthalein Indicator Phenolphthalein (Hph) is prepared by the reaction of phallic anhydride and phenol in presence of concentrated H 2 SO 4. Phenolphthalein is a weak acid and is used as an acid base indicator. Hph dissociates to H + + Ph - and remains in equilibrium condition. The un-dissociated form of Phenolphthalein (Hph) is colourless whereas the colour of Ph - is pink. In acidic medium Phenolphthalein remains un-dissociated, hence appears colourless while in basic medium, the H + is consumed to increase the concentration of Ph -, thereby indicating the colour pink. The ph range of Phenolphthalein indicator is 8.2 to 10. The ph of concrete medium ranges between12 to 13 (basic); hence the colour of Phenolphthalein is pink in concrete. When the ph drops below 9.5 upon carbonation in concrete the indicator turns colourless. On completion of carbonation in chamber, the cubes were drawn off from the chamber & sliced into pieces. The sliced parts were cleaned and phenolphthalein ph indicator, prepared by diluting 1 gram phenolphthalein with 90 ml ethanol in water up to 100 ml, was sprayed on their surface. Carbonated parts were identified to be colourless whereas the non-carbonated editor@iaeme.com

Comparative Analysis of Phenolphthalein Indicator, Xrda and Ftir Methods for Measurement of Carbonation Depth of Concrete parts of the samples turned pink on spraying the indicator.

Figure 1 Carbonation depth XP 2.4. FTIR Method The Fourier Transform Infrared Spectroscopy (FTIR) method is a technique to determine the functional group present in a molecule.

3 Comparative Analysis of Phenolphthalein Indicator, Xrda and Ftir Methods for Measurement of Carbonation Depth of Concrete parts of the samples turned pink on spraying the indicator. Carbonation depth (XP) as indicated in Fig.1was averaged for multiple readings of colourless zones (A1, A2, A3, A4, A5, A6, A7 & A8) from the edge taken after five minutes of spraying. Figure 1 Carbonation depth XP 2.4. FTIR Method The Fourier Transform Infrared Spectroscopy (FTIR) method is a technique to determine the functional group present in a molecule. Every functional group vibrates in two directions, one along the bond (stretching frequency) while the other in the direction perpendicular to the bond (wagging frequency). Further, every atom possesses a unique stretching and wagging frequency. This helps to identify the specific atom/functional group present in a molecule. When the Infrared rays pass through the molecule, the functional group present in the molecule absorbs the IR rays of matching frequency. The FTIR spectrum is graphically represented as percentage transmittance (%T) or percentage absorbance (%A) versus wavenumber. The type of bond/functional group is indicated by the wave number of the peak. The graph falls in the transmittance curve while it peaks in the absorbance curve at specific wave number or frequency which is indicative of carbonation depth. The process of carbonation includes the conversion of C=O bonds of carbon dioxide into C O bonds in the calcium carbonate having wave number in range of cm-1. Hence, the wave number of the C-O bond indicates the carbonation in concrete. FTIR apparatus has been shown in Fig X-Ray Diffraction Analysis In the single and double slit experiments, visible light is used to create diffraction pattern since the wavelength of visible light (10-6 m) is of the order of the width of the slit. The same experiment cannot be used in crustal lattice structures since the atomic spacing is much smaller i.e. of the order m. Hence X-rays having wavelength of the same order are used for diffraction. The X-Ray Diffraction method operates on the principle of phase identification of a crystalline material, providing data on unit cell dimension. X-ray diffraction method is used for recognizing the atomic and molecular structure of a crystal. A cathode ray tube is used to throw Monochromatic X-rays on a crystalline sample resulting in constructive interference to produce diffraction pattern in accordance with Bragg s law (nλ = 2d sin θ). Where n, λ, d and θ are a positive integer, wavelength of the incident wave, scattering and interplanar distance respectively all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material editor@iaeme.com

Alok Ranjan, Rajesh Kumar and Devendra Mohan The XRD analysis was conducted on model MiniFlex 600(Fig.

CaCO 3 and Ca (OH) 2 respectively are used to determine the extent of carbonation in concrete.

specimen is non-carbonated. The existence of both the peaks denotes that the specimen is partially carbonated. Figure 2 FTIR apparatus Figure 3 XRD apparatus 3.

4 Alok Ranjan, Rajesh Kumar and Devendra Mohan The XRD analysis was conducted on model MiniFlex 600(Fig.3) An operating condition with radiation (40 kv, 15 ma) and scan rate: 10 degree/min; 2θ: degree was maintained. The peaks for. CaCO 3 and Ca (OH) 2 respectively are used to determine the extent of carbonation in concrete. For example, the existence of a peak for CaCO 3 exists and no peak for Ca (OH) 2 indicates that the sample is fully carbonated, while a peak for Ca(OH) 2 and no peak for CaCO 3 indicates that the specimen is non-carbonated. The existence of both the peaks denotes that the specimen is partially carbonated. Figure 2 FTIR apparatus Figure 3 XRD apparatus 3. EXPERIMENTAL SET-UP The carbonation chamber is set up at a CO 2 concentration of 4% maintained with the help of a CO 2 cylinder attached to the chamber, a humidity of 65%, temperature of 25 5 and pressure of 1atm. 4. RESULTS AND DISCUSSIONS 4.1. Carbonation Depth Measurement of carbonation depth of OPC concrete at various W/C ratios was done by phenolphthalein indicator, XRDA and FTIR methods, results of which are presented in Table.1 and Fig.4 below. A Comparative study of the conventional method and advanced method are discussed under the following heads: Phenolphthalein indicator It was observed that Carbonation depth (XP) as indicated in fig.1 in OPC concrete was 4.3mm, 7.4mm and 9.9mm at W/C 0.4, 0.45 and 0.5 respectively. Table 1 Carbonation depth vs water/cement ratio of OPC concrete at 3 days curing W/C Carbonation Depth (mm) Phenolpt halein method FTIR method XRD method editor@iaeme.com

5 Comparative Analysis of Phenolphthalein Indicator, Xrda and Ftir Methods for Measurement of Carbonation Depth of Concrete Figure 4 Carbonation depth vs water/cement ratio of OPC concrete at 3 days curing FTIR- method Graphs were obtained between percentage transmittance and wave number for OPC concrete cubes at various water/cement ratios and it was observed that the peaks for Calcium Carbonate occurred at wavenumber in the range of Carbonation depths in OPC concrete were observed as 8.6mm, 14.8mm and 19.8mm respectively for W/C 0.4, 0.45 and XRDA Method Carbonated concrete powder from OPC concrete cubes were taken from 8.6mm, 14.8mm and 19.8mm depth at various W/C ratios. Upon XRDA examination, the samples showed the peaks of concrete at 2θ values. These indicate the crystalline structure of CaCO 3. Hence, depth of carbonation was concluded as 8.6mm, 14.8mm and 19.8mm respectively for OPC concrete cubes at W/C ratios of 0.4, 0.45 and CONCLUSION On basis of the results and discussions, following significant conclusions can be drawn from this study: 1. Carbonation depth determined from XRDA and FTIR method was found to be about twice of that determined by phenolphthalein indicator method. 2. XRDA and FTIR test methods are exact methods to determine the true depth of carbonation in concrete. 3. Carbonation depth increases with the increase of W/C. It may be noted that the XRDA and FTIR test methods compute the existence of CaCO 3 at a ph level ranging from 8.3 to 11.5, whereas the Phenolphthalein indicator method detects the level of carbonation only upto ph value of 9.5. Hence, areas of partial carbonation where the ph ranges from 9.5 to 11.5 cannot be detected by the latter as a result of which carbonation depth detected by the Phenolphthalein indicator method is relatively less editor@iaeme.com

6 Alok Ranjan, Rajesh Kumar and Devendra Mohan REFRENCES [1] RILEM. CPC-18 measurement of hardened concrete carbonation depth. Mater Struct 1988;21(6):453 5 [2] Y. Lo, H.M. Lee. Curing effects on carbonation of concrete using a phenolphthalein indicator and Fourier-transform infrared spectroscopy. Building and Environment 2003; [3] Cheng Feng Chang, Jing Wen Chen. (2006). The experimental investigation of concrete carbonation depth. Cement and Concrete Research, 36, [4] IS: Plain and Reinforced concrete- code of Practice, Bureau of Indian Standards. [5] IS: Concrete mix proportioning guidelines Bureau of Indian Standards. [6] IS: Specification for coarse and fine aggregates from natural sources for concrete, Bureau of Indian Standards. [7] IS: Grade Ordinary Portland Cement-Specifications. Bureau of Indian Standards. [8] M.S. Shetty Concrete Technology S. Chand (Book) editor@iaeme.com

ANALYSIS OF MICROSTRUCTURE OF FUMED SILICA REINFORCED POLYESTER COMPOSITES

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