STUDY OF VAPOUR INHIBITING ABILITY OF CONCRETE AND CHLORIDE ION PENETRATION OF CONCRETE

Transcription

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 6, June 2017, pp , Article ID: IJCIET_08_06_110 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed STUDY OF VAPOUR INHIBITING ABILITY OF CONCRETE AND CHLORIDE ION PENETRATION OF CONCRETE Tanmay. H. Raje Post Graduate student, Department of Civil Engineering, Manipal Institute of Technology, Manipal University, Karnataka, India M. K. Kamat CEO, Krishna Conchem Products Pvt Ltd, Mumbai, India Krishnamoorthy Professor, Department of Civil Engineering Manipal Institute of Technology, Manipal University, Karnataka, India ABSTRACT The effectiveness of anticorrosive cement KRIYA for corrosion resistance property is studied. In depth experimental investigation on vapour inhibiting ability of volatile corrosion inhibiting materials and chloride ion penetration of KRIYA is compared with three different types of conventional cements OPC, PPC and PSC. It is observed that KRIYA is more effective to resist corrosion compared to the conventional cements. Key words: Concrete, Kriya, Vapour Inhibiting Ability (Via), Chloride Ion Penetration, Electrochemical Test. Cite this Article: Tanmay. H. Raje, M. K. Kamat and Krishnamoorthy, Study of Vapour Inhibiting Ability of Concrete and Chloride Ion Penetration of Concrete, International Journal of Civil Engineering and Technology, 8(6), 2017, pp INTRODUCTION Concrete is a hetrogeneous material. In construction industry concrete plays an important role. Concrete is used in construction of major infrastructure projects such as dams, highways, airports, bridges and high-rise structures. Durability parameters are very important for concrete sustainability. In concrete technology cement has utmost significance since reinforcement in concrete is protected by alkaline nature of cementatious matrix. Reinforcements are vulnerable to corrosion due to carbonation and chloride ion attack. Concrete is a permeable material where aggressive agents by diffusion come in contact with reinforcing steel causing its depassivation and corrosion process is accelerated by ingression of water and surrounding oxygen. The editor@iaeme.com

2 Study of Vapour Inhibiting Ability of Concrete and Chloride Ion Penetration of Concrete cement properties can be modified by adding cement additives there by enhancing the durability aspects of concrete. Additives may be in the form of accelerators, retarders, anti-gas migration agents and inhibitors. In this paper, a new anticorrosive cement, KRIYA which is prepared by adding corrosion inhibiting materials to ordinary Portland cement in different proportions. Results of an experimental investigation is presented whereby vapour inhibiting ability (VIA) test and rapid chloride penetration test (RCPT) tests have been carried to study the effectiveness of KRIYA to resist corrosion. The anticorrosive property of KRIYA is compared with the anticorrosive properties of three other different types of conventional cements such as OPC, PPC and PSC. A concrete mix of M25 grade concrete using all the four types of cement is prepared in a cylindrical mould and a steel reinforcement is embedded inorder to measure its corrosion. After curing for 60 days, these moulds are immersed in chloride solution using 3.5% NaCl. The main objective of the present study is to determine the vapour inhibiting ability of KRIYA and determination of its resistance to chloride ion penetration. 2. EXPERIMENTAL INVESTIGATION 2.1. Test variable and material used The major test variables for the present experimental investigation is cement type. Four concrete mixes are used in this investigation using four types of cements. The different types of cements used in experimental work are OPC (Ordinary Portland cement), PPC (Pozzolanic Portland Cement), PSC (Pozzolanic Slag Cement) and KRIYA (Anti-corrosive cement). Thermo Mechanically Treated (TMT) bar of 12 mm diameter confirming to IS is used in the study to measure the corrosion. Anticorrosive cement KRIYA is a blended cement with OPC and anticorrosive additives in different proportions. The three types of cements used to compare the effectiveness of KRIYA are OPC satisfying ASTM Type I and Indian standards IS: ,18, PPC having 20% pozzolana (fly ash) content and satisfying ASTM Type IP and IS: (Part I), and PSC satisfying ASTM Type IS and IS: are used for comparison. The w/c ratio used for all four types mix is The chloride added to concrete is sodium chloride of an analytical reagent grade. The concentrations of admixed sodium chloride used are 3.5% by mass of cement. Coarse aggregates with a size 20 mm maximum size of aggregate and 10 mm to satisfy the overall grading requirement of coarse aggregate as per ASTM C33-92a21 and IS: Land-quarried sand confirming to Zone II classification of British standards is used as fine aggregate. Tap water from the laboratory of a deep ground water source is used for the experiment. The composition of the tap water is given in Table 1. All the concrete mixtures have been designed for similar workability with a slump in the range of 30 mm to 60 mm editor@iaeme.com

3 Tanmay. H. Raje, M. K. Kamat and Krishnamoorthy Table 1 Test report for water Sl. No Solids Max permissible limits Actual 1 Chlorides 2000 ppm for plain 500ppm for RCC 350 ppm 2 Sulphates 400ppm 0 ppm 3 Acidity 50 ppm 50 ppm 4 Alkinity 250 ppm 230 ppm 5 ph 6 to Preparation of concrete specimen for testing A cylindrical steel mould of 100 mm diameter and 200 mm length is used for preparing the specimen. Wire brushed steel bars of 12 mm diameter and 304 mm in length cleaned by soaking in analytical reagent grade HCL and washed by alkaline agent are placed at the center of the cylinder. C-clamps are used to maintain the verticality of TMT bar. Bottom 10 mm is coated with epoxy coating. This steel specimen preparation is similar to that specified in ASTM G109-99a. Concrete mix of M25 grade with water cement ratio of 0.42 prepared using four types of cements and is poured into the cylinder Test Procedure VIA Test In order to understand the anticorrosive property of concrete, vapour inhibility test is conducted on concrete specimens. Cylindrical samples after curing for 60 days are broken and the concrete samples surrounding the TMT bars are collected. Four bottles of 1000 ml are used for conducting VIA test where, each bottle is given identification mark as OPC, PPC, PSC, KRIYA. 100 gms of concrete samples which are collected as above are poured into the bottle. Four steel samples are polished with emery paper No. 80 to 1200 finest grade in stepwise and finally cleaned with methanol. These polished samples are enclosed in rubber seal. A aluminium pipe is inserted at the center of polished stopper assembly with attachment of aluminium pipe and steel sample exposing polished surface in inverted position at top of the jar. The number of spots on polished surface indicates the amount of corrosion. A solution consisting of 26% of glycerin and ice cooled water which produces vapour with approximately 90% RH is prepared. After 20h the small ice pieces and chilled water is filled into the aluminum tube from top and allowed to form water droplet at the exposed steel surface in all jars. Rubber cork is removed and visual observation are made on the polished surface of steel specimen and number of spots are measured Rapid Chloride Penetration Test Rapid chloride penetration test is conducted to measure the chloride ion penetration in concrete mixes. The instrument used to conduct this test is shown in figure 1. As per ASTM C1202, in the rapid chloride penetration test, a water-saturated, 50-mm thick, 100-mm diameter concrete specimen is subjected to a 60 V applied DC voltage for 6 hours. The permeability cell, which is made of perspex glass consisting of two parts each with a reservoir being capable of holding 250 ml of chemical solution and copper mesh of 100 mm diameter to act as an electrode. 3.0% editor@iaeme.com

4 Study of Vapour Inhibiting Ability of Concrete and Chloride Ion Penetration of Concrete NaCl solution of 2.4N is filled in the reservoir of one part and 0.3M NaOH solution (chloride free) is filled in the reservoir of another part. These concentrations gives the equal electrical conductivity for both the solutions. An external voltage cell is used to apply a voltage difference of 60V between the electrodes. The electrochemical cell, constituted by this assembly, results in the rapid migration of chloride ions from the sodium chloride solution to the sodium hydroxide solution, via the pore network offered by the concrete disc shaped specimen. The total charge passed in coulombs is determined and this is used to rate the quality of the concrete according to the criteria rating mentioned in the ASTM C1202 as shown in Table.2. The total charge passing from one reservoir to another reservoir through centrally placed concrete specimen in 6 hours is measured, at an interval of 60 min, indicating the degree of resistance of the specimen to chloride ion penetration. The following formula, based on the trapezoidal rule can be used to calculate the average current flowing through one cell. Q = (I0 + I1 + I2 + I3 + I4 + I5 + I6) mah I mah = I x 0.001A x 3600 s Where Q = total electrical charge passed through the specimen (in coulombs) ; I0, I6 are the initial and final currents ; I1, I2, I3, I4 and I5 are the intermediate currents at each one hour and I is the total current at the end of the test i.e. after 6 hours. The test determines the electrical conductance of the test specimen, expressed as the total electrical charge passed through the specimen, in coulombs. (Source: Figure 1 Rapid Chloride Permeability Test Setup editor@iaeme.com

5 Tanmay. H. Raje, M. K. Kamat and Krishnamoorthy Table 2 RCPT Criteria Ratings Electric Charge Passed Permeability Class as per ASTM C1202 (Coulombs) High > 4,000 Moderate Low Very Low Negligible < RESULTS AND DISCUSSIONS In order to study the effectiveness of KRIYA cement for anticorrosive properties RCPT test is conducted to measure the chloride ion penetration. A concrete sample of 100mm diameter and 200 mm with w/c ratio 0.42 is prepared using KRIYA cement. The samples are cured for 60 days and then samples are cut into four pieces each of height 50mm. RCPT test is then conducted on each of these samples. In order to compare the results, RCPT test on concrete samples prepared using OPC, PPC and PSC cement at the similar w/c ratio of 0.42 is also conducted. The RCPT readings recorded for the four concrete samples are tabulated as shown in table 3. When these readings are compared with standard values as shown in table 2, the chloride ion penetration of KRIYA and PSC cement is low whereas, the chloride ion penetration of OPC and PPC is moderate. When the RCPT values of specimen prepared with KRIYA cement is compared with RCPT values of specimens prepared with other cements, it can be observed that the RCPT readings for the concrete sample prepared with KRIYA cement is lesser compared to the concrete specimens prepared using other three types of cement. This indicates that chloride penetration in KRIYA cement is less because of its special additives which restrict the chloride penetration in concrete. This shows the effectiveness of KRIYA to resist chloride penetration. Table 3 RCPT readings for different cement types SR.NO CEMENT COLUMBS PASSED 1 KRIYA PSC PPC OPC 2089 In order to study the effectiveness of KRIYA cement for vapor inhibility property, vapor inhibility test is conducted on concrete specimen prepared using KRIYA cement as explained in 2.2. The vapor inhibility tests are also conducted on concrete specimens prepared using the other three cements OPC, PPC and PSC. Fig. 2 shows the experimental set up conducted on four samples at the end of the test. From these pictures it can be observed that the number of corrosion spots on the specimen prepared using KRIYA cement is considerably lesser than that of the specimens prepared using other three types of cements. This shows the effectiveness of volatile corrosion inhibiting material present in KRIAY cement editor@iaeme.com

6 Study of Vapour Inhibiting Ability of Concrete and Chloride Ion Penetration of Concrete Figure 2 Picture showing the test specimen and the corrosion spots on polished surface 4. SUMMARY AND CONCLUSIONS Anti-corrosive property of KRIYA cement is evaluated by comparing the anticorrosive properties of KRIYA cement with the ant corrosive property of ordinary three types of cement PPC, OPC and PSC. The anticorrosive property considered for the study are vapor inhibility and chloride penetration. From the study it is concluded that the rapid chloride penetration test values for specimens prepared using KRIYA cement are lesser compared to the rapid chloride penetration test values for specimens prepared using other three types of cements. In addition, it is observed from the vapor inhibiting test that the concrete mix prepared using KRIYA cement is more effective compared to concrete specimens prepared using other three types of cements. Thus it can be concluded that KRIYA cement is more effective to resist corrosion compared to other cements. REFERENCES [1] Mehta, P. K., and Monteiro, P. J. M. Concrete: Microstructure, Properties, and Materials, Tata McGraw-Hill, Third edition, [2] Neville, A. M., and Brooks, J. J. Concrete Technology, Pearson Education, Fourth Indian reprint, [3] IS (Reaffirmed 2005), 43 grade ordinary Portland cement- Specification, Bureau of Indian Standards, New Delhi. [4] IS (Reaffirmed 2004), Specification for 53 grade ordinary Portland cement, Bureau of Indian Standards, New Delhi. [5] IS 1489 (Part 1) 1991 (Reaffirmed 2005), Portland-pozzolana cement Specification, Bureau of Indian Standards, New Delhi. [6] IS (Reaffirmed 2005), Portland slag cement Specification, Bureau of Indian Standards, New Delhi. [7] IS (Reaffirmed 2005), Rapid hardening Portland cement Specification, Bureau of Indian Standards, New Delhi editor@iaeme.com

7 Tanmay. H. Raje, M. K. Kamat and Krishnamoorthy [8] IS (Reaffirmed 2002). Specification for coarse and fine aggregates from natural sources for concrete, Bureau of Indian Standards, New Delhi [9] ASTM G a. Standard test method for determining the effects of chemical admixtures on the corrosion of embedded steel reinforcement in concrete exposed to chloride environments. West Conshohocken, PA: ASTM G 109; [10] Anand V R, Dr. A. V. Pradeep Kumar and Aneesh V Bhat, An Experimental Investigation on the Performance of High Volume Ground Granulated Blast Furnace Slag Concrete. International Journal of Civil Engineering and Technology, 8(2), 2017, pp [11] J. Anne Mary, An Experimental Investigation on Copper Slag as Replacement of Fine Aggregate in Concrete. International Journal of Civil Engineering and Technology, 7(6), 2016, pp NACE TM-208 Laboratory Test to Evaluate the Vapor-hibiting Ability of Volatile Corrosion Inhibitor Materials for Temporary Protection of Ferrous Metal Surfaces;2008 [12] JIS Z 1519 (Japanese Industrial Standard) test method evaluates the vapor-inhibiting ability of VCI materials for corrosion protection of Ferrous / Steel metal editor@iaeme.com