(Print), ISSN (Online) Volume 3, Issue 2, July- December (2012), IAEME TECHNOLOGY (IJCIET)

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1 INTERNATIONAL International Journal of Civil JOURNAL Engineering and OF Technology CIVIL (IJCIET), ENGINEERING ISSN AND TECHNOLOGY (IJCIET) ISSN (Print) ISSN (Online) Volume 3, Issue 2, July- December (2012), pp IAEME: Journal Impact Factor (2012): (Calculated by GISI) IJCIET I A E M E EXPERIMENTAL STUDY ON WATER PERMEABILITY AND CHLORIDE PERMEABILITY OF CONCRETE WITH GGBS AS A REPLACEMENT MATERIAL FOR CEMENT V.S.TAMILARASAN*, Dr.P.PERUMAL # and Dr.J.Maheswaran $ * Research Scholar & Assistant Professor, Department of Civil Engineering, Dr.Sivanthi Aditanar College of Engineering, Tiruchendur (E mail: vstamil@yahoo.com, vstamil1@gmail.com) # Professor & Head, Department of Civil Engineering, Government College of Engineering, Salem (E mail: perumal2012@yahoo.co.in) $ Principal, Dr.Sivanthi Aditanar College of Engineering, Tiruchendur (E mail: sacoeprincipal@gmail.com) ABSTRACT Over the past decade, global warming and environmental destruction have become manifest problems, resulting in increasing attention to pollution and waste management control. The use of recycled waste cementitious materials is becoming of increasing importance in construction practice. In India, we produce about 7.8 million tonnes of blast furnace slag, which is a by-product of steel. The disposal of GGBS as a landfill is a problem, which leads to serious environmental hazards. GGBS can be incorporated in cementitious materials to modify and improve certain properties for specific uses. An attempt has been made to replace cement using GGBS in concrete of gradesm 20 & M 25 and studying its permeability characteristics. GGBS was used to replace the cement partially from 0 to 100% at increments of 5%. The experimental results showed that, with the partial replacement of cement by GGBS till 60%, the permeability of concrete is decreased and the resistance to chemical attack is increased. Key Words: Admixture, Chloride, Concrete, Hydration, Permeability, Slag. 1. INTRODUCTION In recent years there is an increasing awareness regarding environmental pollution due to domestic and industrial wastes. The development and use of blended 25

2 cement is growing in Asia, mainly due to considerations of cost saving, energy saving, environmental protection and conservation of resources. Mineral Admixtures such as Ground Granulated Blast Furnace Slag (GGBS), Fly ash and Silica fume are commonly used in concrete because they improve durability, reduce Porosity and improve the interface with the aggregate. Ground Granulated Blast furnace Slag is a by-product obtained in the manufacturing of pig iron in the blast furnace. It is a non-metallic product consisting essentially of silicates and aluminates of calcium and other bases. The molten slag is rapidly chilled by quenching in water to form a glassy sand like granulated material. GGBS is recognized as a desirable cementitious ingredient of concrete and as a valuable cement replacement material that imparts some specific qualities to composite cement concrete [1]. The lower cement requirement also leads to a reduction of CO 2 generated by the production of cement. The hydration of the Portland cement results from the production of Portlandite crystal [Ca(0H) 2 ] and amorphous calcium silicate hydrate gel [C3S2H3] (C S H) in large amounts. Hydrated cement paste in volves approximately70% C S H, 20% Ca(0H) 2 ; 7% sulpho-aluminates and 3% secondary phases. The Ca(0H) 2 which appears as the result of the chemical reactions affect the quality of the concrete adversely by forming cavities as it is partly soluble in water and lacks enough strength. The use of ground granulated blast-furnace slag has a positive effect on binding the Ca(0H) 2 compound, which decreases the quality of the concrete. At the end of the reaction of the slag and Ca(0H) 2, hydration products, such as C S H gel, are formed [2]. It is seen that high volume eco-friendly replacement by such slag leads to the development of concrete, which not only utilises the industrial wastes but also saves a lot of natural resources of energy. While using the GGBS in concrete, it reduces heat of hydration, refinement of pore structure, permeability and increase the resistance to chemical attack. 2. WATER PERMEABILITY Permeability of concrete is the relative ease with which water can penetrate into the pores of concrete. The study of permeability in concrete is important when concrete is subjected to hydrostatic pressure in concrete dams, offshore structures, nuclear power plants etc. The penetration of weathering agents into concrete may lead to the corrosion of reinforcement and hence weaken the structures. Penetration of concrete by materials in solution may adversely affect its durability. Therefore a detailed study has been required to find the permeability of concrete. 26

3 3. CHLORIDE PERMEABILITY High quality and durable concrete is required to reduce the rapid deterioration of concrete in severe conditions. Among the factors related to declining concrete durability such as carbonation, corrosion, alkali silica reaction, freezing/thawing, and soon, the penetration of chloride-ions into concrete has been regarded as the major deterioration problem. Ingress of chloride-ions destroys the natural passivity of the surface of reinforcing steel, and often leads to the corrosion of steel in concrete structures. Thus, insufficient concrete cover or poor quality concrete accelerates reinforcement corrosion. Particularly, environmental conditions in offshore or coastal region reduce useful service-life of concrete structures due to chloride-ion attacks. Previous studies [4-9] have shown that use of cement replacement materials such as fly ash, silica fume, blast-furnace slag, etc. may reduce greatly the probability of steel corrosion as well as the permeability of concrete. 4. MATERIALS USED 4.1 Cement Ordinary Portland cement of 53 grade was used, which has the fineness modulus 1.5, Specific gravity 3.08, Consistency 37%, Initial setting time 2hrs 30min and Final setting time 3hrs 30min. 4.2 Coarse aggregate Angular shape aggregate of size of 20 mm was used and it has the following properties: Specific gravity 2.94, Fineness modulus 7.72, Flakiness index100%, Abrasion value 20.4%, Crushing value 30.02%, Impact value 23.6%, Bulk density1.42 x 10 3 Kg/m 3 and Water absorption 1.01%. 4.3 Fine aggregate River sand conforming to zone III of IS: was used and its properties are found as follows: Specific gravity 2.68, Moisture content 0.71 and Fineness modulus GGBS Physical properties of GGBS are: Specific gravity 3.44 and Fineness modulus3.36, and the chemical composition of GGBS is Carbon (C) 0.23%, Sulphur (S) 0.05%, Phosphorous (P) 0.05%, Manganese (M n ) 0.58%, Free silica 5.27% and Iron (Fe) 93.82%. 5. METHODOLOGY 27

4 0 to 100% at intervals 5% of cement was replaced by GGBS and the mix grades M 20 (1:1.6:3.559:0.50) and M 25 (1:1.326:3.11:0.44) were used [10 & 11]. For each level of replacement, 3 cubes were cast by thoroughly mixing cement, fine aggregate, coarse aggregate and water in the mixer machine. All the cubes were cured in water for a period of 28 days and cubes were arranged in permeability testing machine and test was carried out for 100 hrs. Afterwards, using formulae, co-efficient of permeability was found out. 6. WATER PERMEABILITY TESTING 6.1 Methods concrete, There are two common methods for the evaluation of the permeability of i) Steady flow method ii) Depth of Penetration method Steady flow method suits concrete with relatively high permeability, while the depth of penetration method is most appropriate for concrete with very low permeability. The co-efficient of permeability was measured using concrete permeability apparatus. Compressed air at 7kg/cm 2 was supplied to the permeability cell assembly using an air compressor. The water reservoir of the apparatus was filled with clean water. With the reservoir completely filled with water, the air pressure was applied to the water reservoir. A clean collection bottle was weighed and placed to collect the permeated water. The quantity of percolate was measured at fixed intervals continuously after a steady state was reached. In steady flow method; the coefficient of permeability can be calculated using the formula, K= QL ATH Where, K Coefficient of permeability in m/sec Q Quantity of percolated water in m 3 L Length of the specimen in m A Area of cross section of the specimen in m 2 T Total duration in sec H Head of water in m 28

5 In certain cases, no discharge was obtained even after a period of 100hrs. In such cases, co efficient of permeability was calculated by using the Depth of penetration method. The specimens were removed from the test cell and were split open to determine the depth up to which water had penetrated. In Depth of penetration method, the co-efficient of permeability can be calculated using the formula, Where, 6.2 Principle D Depth of penetration in m P Porosity of concrete T Total duration in sec H Head of water in m K= D2 2TH Permeability cell consists of a metal cylinder with a ledge at the bottom for retaining the specimen and an integral funnel below to collect the permeated water. It has a flange at the top and removable cover plate, which can be securely bolted to the cell. The flange is provided with a circular groove to fit a sealing ring to render the assembly watertight. A rubber gasket is placed between the cell and the cover plate to render the joint watertight. The water reservoir consists of a metal cube of size 150mm. The reservoir has valves for admitting water, compressed air and for draining. It is fitted with two pressure gauges to show the pressure inside the water cylinder (test pressure 7kg /cm 2 ) and admitted air pressure. It is provided with an adjustable valve to maintain the test pressure at a constant value. The water reservoir is connected to the permeability cell by a shielded pressure hose as shown in fig. 1 and the enlarged section as shown in fig. 2. Clean de-aired water is used in the reservoir. 29

6 Figure 1 - Permeability Testing Apparatus Parts of Permeability Testing Apparatus 1. From air compressor 7. Flexible hose 2. Water reservoir 8. Stand 3. Valve for admitting water 9. Permeability cell 4. Pressure regulator 10. Cover plate 5. Pressure gauges 11. Butterfly nuts 6. Valve for admitting water into permeability cell Figure 2 Enlarged Section of Permeability Cell 30

7 6.3 Procedure A rubber sheet of 8mm thick and 150mm x 150mm size was taken with hole of 100mm x 100mm made in the center. This sheet was placed above and below the cube admitting the water through the surface area only. After that the cover plate was closed and all the bolts were tightened. With the completely filling the water the desired test pressure 7kg /cm 2 was applied to the water reservoir. At the same time a clean collection bottle was weighed and placed in position to collect the water percolating through the specimen. The quantity of percolation was recorded at periodic intervals. In the beginning, the rate of water intake was larger than the rate of outflow. As the steady state of flow is approached, the two rates tend to become equal and the outflow reaches a maximum and stabilizes. With further passage of time, both the inflow and outflow generally register a gradual drop. Permeability test is to be continued for about 100 hours after the steady state of flow has reached and the outflow will be considered as the average of all the outflows measured during this period of 100 hours [12 & 13]. If any permeation of water was there, then the quantity of permeated water measured and value calculated using the steady flow method. And if there was no permeation, the cubes were split and depth of penetration measured and value calculated using the depth of penetration method. The measure of water penetration is achieved by measuring the average depth of discoloration, due to wetting. 6.4 Test Results of Water Permeability No permeation was found. Hence the depth of penetration method was used. The observations and results showing the values of k are presented in table 1 and 2 for M 20 grade and M 25 grade GGBS added concrete without and with Superplasticiser respectively. Graphs were plotted by taking % of replacement of cement using GGBS in X-axis and Coefficient of permeability in Y-axis. Figure 3 and Figure 4 Show the Coefficient of Permeability for M 20 grade and M 25 grade GGBS added Concrete with and without Superplasticiser respectively. Table 1 - Coefficient of Permeability for M 20 grade GGBS added Concrete without and with Superplasticiser 31

8 Co efficient of permeability Id Replacement x (m / sec) mark Level Without Superplasticiser With Superplasticiser Table 2 Coefficient of Permeability for M 25 grade GGBS added Concrete without and with Superplasticiser Id mark Replacement Level Co efficient of permeability x (m / sec) Without Superplasticiser With Superplasticiser 32

9 Co-efficient of Permeability m/sec Without Super Plasticiser With Super Plasticiser Replacement Level Figure 3 Coefficient of Permeability for M 20 grade GGBS added Concrete without and with Superplasticiser Co-efficient of Permeability m/sec Without Super Plasticiser With Super Plasticiser Replacement Level Figure 4: Coefficient of Permeability for M 25 grade GGBS added Concrete with and without Superplasticiser 7 CHLORIDE PERMEABILITY TESTING 7.1 General For reinforced concrete bridges, one of the major forms of environmental attack is chloride ingress, which leads to corrosion of the reinforcing steel and a subsequent reduction in the strength, serviceability and aesthetics the structure. This 33

10 may lead to early repair or premature replacement of the structure. A common method of preventing such deterioration is to prevent chlorides from penetrating in to the structure up to the level of the reinforcing steel bar by using relatively impermeable concrete. The ability of chloride ions to penetrate the concrete must then be known for design as well as quality control purposes. The penetration of the concrete by chloride ions, however, is a slow process. It cannot be determined directly in a time frame that would be useful as a quality control measure. Therefore, in order to assess chloride penetration, a test method that accelerates the process is needed, to allow the determination of diffusion values in a reasonable time [6]. 7.2 Principle This test method consists of measuring the amount of electrical current passed through 2-inches (51-mm) thick slices of 4-inches (102-mm) nominal diameter cores or cylinders during a 6-hours period. A potential difference of 60-voltage dc was maintained across the ends of the specimen. In which one of the surface of specimen was immersed in a sodium chloride solution, the other in a sodium hydroxide solution. The total charge passed, in coulombs were found and related with the resistance of the specimen to chloride ion penetration. 7.3 Significance and use This test method covers the laboratory evaluation of the electrical conductance of concrete samples to provide a rapid indication of their resistance to chloride ion penetration. The test method is suitable for evaluation of materials and material proportions for design purposes and research development. 7.4 Procedure The specimen was cylindrical shape, size of 105mm diameter, 50mm length. Three cylindrical specimens were used for each percentage of replacement of slag for determining chloride ion penetration. The apparatus consists of two cells. The specimen is mounted as shown in figure 7 and fixed between the cells in such a way that the round edge surface should be in touch with the solution. After fixing the specimen, the negative of the cell was filled with 3% NaCl solution. The positive side of the cell was filled with 0.3M NaOH solution till the top surface of the concrete immerses in the solutions. Leakage was checked. Copper rods were used as electrodes. The wires, electrodes, power supply were connected. 34

11 International Journal of Civil Engineering and Technology (IJCIET), ISSN Figure 5 Chloride Permeability Test Setup A D.C supplier was used to give electrical potential of 12v. The ve terminal of D.C.S is connected with electrode of NaCl solution. The +ve terminal of D.C.S is connected with electrode of NaOH solution. As per electro - chemistry principle, due to the applied voltage, the negative ion i.e. the chloride ion is attracted towards positive terminal i.e. NaOH reservoir. Therefore the chloride ion moves through the concrete specimen. Also the positive ion passes towards the negative terminal i.e. NaCl reservoir through the concrete specimen Due to the movement of positive and negative ions current is produced. This current is shown in D.C supplier. Reading is taken immediately after voltage supplied at every 30 minutes. This procedure is done for 6 hours duration. Decrease in charge passed values indicates that the concrete has more resistance to chloride ion penetration [9]. The total charge passed is a measure of the electrical conductance of the concrete during the period of the test. If the current is recorded at 30 min interval, the following formula, based on the trapezoidal rule, can be used with an electronic calculator to perform the integration: Q=900(I 0 +2I 30 +2I I I 330 +I 360 ) Where, Q = charge passed (Coulombs) I 0 = current (Amperes) immediately after voltage is applied, and I t = Current (Amperes) at t min after voltage is applied. Correction:

12 If the specimen diameter is other than 3.75 inch (95 mm) the value for total charge passed must be adjusted. The adjustment is made by multiplying the value by the ratio of the cross-sectional areas of the standard and the actual specimens. That is: Where, Q s = Q x x (3.75/X) 2 Q s = charge passed (coulombs) through a 3.75-inch (95-mm) diameter Specimen. Q x = charge passed (coulombs) through X in diameter specimen and X = Diameter (inch) of the nonstandard specimen. 7.5 Test results of Chloride Permeability The experiment was conducted on various types of mix containing partial replacement of cement by GGBS. The values of charge passed are tabulated as shown in table 3 & 4. Graphs are plotted by taking % of replacement of GGBS in X-axis and charge passed in Y-axis. Fig 6 and Fig 7 show the Values of charge passed through M 20 grade without and with Superplasticiser added GGBS concrete and Values of charge passed through M 25 grade without and with Superplasticiser added GGBS concrete respectively. Table 3 -Values of charge passed through M 20 grade GGBS added concrete without and with Superplasticiser Id mark Replacement Charge Passed (Coulombs) Level Without Superplasticiser With Superplasticiser

13 Charge Passed (Coulombs) Without Super Plasticiser With Super Plasticiser Replacement Level Figure 6: Values of charge passed through M 20 grade GGBS added concrete without and with Superplasticiser Table 4 - Values of charge passed through M 25 grade GGBS added concrete without and with Superplasticiser Id Replacement Charge Passed (Coulombs) mark Level Without Superplasticiser With Superplasticiser

14 Charge Passed (Coulombs) Without Super Plasticiser With Super Plasticiser Replacement Level Figure 7: Values of charge passed through M 25 grade GGBS added concrete without and with Superplasticiser 8 TEST RESULTS & DISCUSSION Water Permeability: The permeability tests in M 20 & M 25 grades of GGBS added concrete without and with Superplasticiser were conducted by depth of penetration method. For conventional concrete, the Co-efficient of permeability for M 20 and M 25 grade concrete are x m/sec and x m/sec respectively. For M 20 grade GGBS added concrete, the Co-efficient of permeability varies decreases from x m/sec to 1.90 x m/sec for the replacement of cement by 5% to 60% at interval of 5% and then the value increases upto 100%. And for M 25 grade GGBS added concrete, the Co-efficient of permeability varies from x to 1.25 x m/sec for the replacement of cement by 5% to 60% at interval of 5% and the value increases upto 100%. For Superplasticiser added GGBS concrete, the Co-efficient of permeability of conventional concrete for M 20 and M 25 grade are 14.18x10-13 m/sec and 10.41x10-13 m/sec respectively. For Superplasticiser added GGBS concrete, the Co-efficient of permeability for M 20 grade values decreases from x m/sec to 1.04 x m/sec for the replacement of cement by 5% to 60% at interval of 5% and then the value increases up to 100%. And the Co-efficient of permeability for M 25 grade varies from 9.45 x to 0.68 x m/sec upto 60% at interval of 5% and the value increases upto 100%. 38

15 Chloride Permeability: The Chloride diffusion tests in M 20 & M 25 grade concrete were conducted using RCPT testing machine. For conventional concrete, the Charge passed for M 20 and M 25 grade concrete are 553 Coulombs and 378 Coulombs respectively. For M 20 grade GGBS concrete, the Charge passed values varies from 545 Coulombs to 346 Coulombs for 5% to 60% at interval of 5% and the value increases up to 100% and for M 25 grade GGBS concrete, the Charge passed values varies from 368 Coulombs to 185 Coulombs for 5% to 60% at interval of 5% and the value increases upto 100%. For M 20 grade Superplasticiser added GGBS concrete, the Charge passed values varies from 388 Coulombs to 287 Coulombs for 5% to 65% at interval of 5% and the value increases up to 100%. And for M 25 grade Superplasticiser added GGBS concrete, the Charge passed values varies from 308 Coulombs to 171 Coulombs for 5% to 60% at interval of 5% and the value increases up to 100%. 9 CONCLUSION For both the grades of GGBS concrete and Superplasticiser added GGBS concrete, as the replacement level increases, the chloride permeability value decreases which improves the chloride penetration resistance of the concrete and durability of concrete. By using GGBS as a replacement material for cement, the cost of construction will be reduced. Use of GGBS in concrete also prevents the environment from degradation. 10 REFERENCE 1. Rajamane N.P., et.al (2003) Improvement in Properties of High Performance Concrete with Partial Replacement of Cement by Ground Granulated Blast Furnace Slag, IE (I) Journal-CV, 84pp Oner A, & Akyuz S. (2007) An experimental study on optimum usage of GGBS for the compressive strength of concrete, Cement & Concrete Composites 29pp Adakhar (2001) Compatibility of super plasticizer slag added concrete in sulphate resistance and chloride penetration, Advances in Civil Engineering Materials and construction technology, 33pp. 4. Alexander M.G & Milne T.I., Influence of cement Blend and aggregate type of stress strain behaviour and elastic modulus of concrete, AC1 Materials Journal, 92, no.3, pp

16 5. Annie peter & Rajamane N.P. (1997) Bond strength of reinforcement in High performance concrete: The role of GGBS, casting position and super plasticizer dosage, Indian concrete Journal, August pp. 6. Kyong Yun Yeau & EunyumKi (2005) An experimental study on corrosion resistance of concrete with ground granulate blast - furnace slag, Cement and Concrete Research 35pp Balamurugan P & Perumal P. (2003) Behaviour of High Performance Concrete under elevated temperature and chloride penetration, Proceedings of the National seminar on Futuristic in concrete and construction Engineering, SRM Engineering College, Kattankulathur, pp Manoj K Jain and Pal S.C. (1998) Utilisation of Industrial slag in Making High Performance Concrete Composites, The Indian Concrete Journal, pp Zeghichi L. (2006) The Effect of Replacement of Naturals Aggregates by slag products on the strength of concrete, Asian Journal of Civil Engineering (Building and Housing), Vol 7, pp Shariq M. et.al (2008) Strength Development of Cement Mortar and Concrete incorporating GGBFS, Asian Journal of Civil Engineering (Building and Housing), Vol 9, No 1, pp Report by ACI committee 226, IR 87 GGBF Slag as cementitious constituent in concrete. 12. M.S. Shetty (2011) A Text Book of Concrete Technology Theory and Practice, S.Chand& Co, New Delhi. 13. Gambhir (2003) A Text Book of Concrete Technology, Tata McGraw Hill, New Delhi. 14. A.M. Neville (2004) A Text Book of Concrete Technology, Tata McGraw Hill, New Delhi. 15. IS: , Code of practice for plain and reinforced concrete, Bureau of Indian Standards, New Delhi. 16. IS: , Code of Practice for Concrete Mix Design, Bureau of Indian Standards, New Delhi. 17. IS: , Indian Standard Method of Test for Permeability of cement Mortar and concrete, Bureau of Indian Standards, New Delhi. 18. IS: , Specification for 53 grade ordinary Portland cement, Bureau of Indian Standard, New Delhi. 40