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Engineering
Procedia Engineering 14 (2011) 2642-2649
www.elsevier.com/locate/procedia
The Twelfth East Asia-Pacific Cvnforonco vn Structural Engineering end Construction
Durability vf Pvlymor and Fly Ash Modified Forrv Cement
Elements
V.BHIKSHMA1a, RAVANDEKISHORE2 and R.SRINIVAS3
1 Department of Civil Engineering, University College of Engineering Osmania University Hyderabad, India
2 Department of Civil Engineering, University College of Engineering Osmania University Hyderabad, India
3 Department of Civil Engineering, University College of Engineering Osmania University Hyderabad, India
Abstract
Ferro cement is a highly versatile form of composite materials made of cement mortar and layers of wire mesh. The scope of this paper is to determine and compare the durability of polymer-modified Ferro cement with fly ash modified ferro cement elements. To study the permeability of cement mortar, 12 cylinders of height 100 mm and diameter 50 mm were cast. Further to study the corrosion performance of mesh reinforcement, 36 prisms of size 300 mm long, 50 mm width and 25 mm thickness were cast by varying the number of layers of mesh. To accelerate corrosion, impressed current voltage test was conducted and the corrosion process was monitored continuously. The corrosion performance in conventional ferro cement is compared with that of polymer Ferro cement and fly ash modified Ferro cement. From the results, the corrosion inhibiting property of fly ash and polymer Ferro cement is remarkably improved with an increase from 0% to 30% of fly ash, 0% to 12.5% of polymer and decrease with specific surface of reinforcement.
© 2011 Published by Elsevier Ltd.
Keywords: Ferro Cement; Wire mesh; Permeability; Accelerate Corrosion; Current Voltage and Polymer Ferro cement.
1. INTRODUCTION
Ferro cement is a kind of composite material where the filler material, usually brittle in nature, called matrix is reinforced with fibers dispersed throughout the composite resulting in better structural performances than that of the individual one. The use of fibers to reinforce a brittle matrix is not really a new idea. The ancient use of straw in bricks and hair in mortar can be said to predate the use of conventional Portland cement concrete. The dispersion of the fibres in the brittle matrix offer not only convenience and practical means of achieving improvement in many of the engineering properties of the
a Cvrrespvnding authvr & presenter: 1. Email: v.bhikshma@yahvv.cv.in
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.07.332
materials such as a fracture, tensile and flexural strength, toughness, fatigue resistance and impact resistance but also provide advantages in terms of fabrication of products and components.
2. OBJECTIVE OF THE WORK
The objective of this investigation is to study experimentally the durability of polymer and fly ash modified Ferro cement elements.
3. SCOPE OF THE WORK
In order to find out the permeability of cement mortar, cast the cement motor specimens of cylinders (100 mmdiax50 mm height) by partial replacement of cement by fly ash (0%, 5%, 10%, 15%, 20%, 25%, and 30%) and polymer (0%, 2.5%, 5%, 7.5%, 10%, and 12.5%) and to study the corrosion performance of mesh reinforcement.
4. LITERATURE REVIEW
Joseph-Louis Lambot's (1) original French patents on wire-reinforced boats were issued in 1847 not long after the development of portland cement recently, the American concrete Institute (ACI) Committee 549 (2) on Ferro cement concluded that the definition of Ferro cement cannot be limited to steel reinforcing even if most of the present applications emphasize this kind of reinforcing material. Accordingly, the Committee defines it as follows:According to M. Neelamegam, Y. Ohama, K. Demura(3) deformational behaviour and durability of polymer-impregnated ferrocement (PIFC) in comparison with ferrocement (FC). It is concluded from the test results that the load cracking composite stresses in flexure and direct tension of PIFC are improved 3 to 4 times over those of FC.
R. N. Swamy and M. W. Hussin (4) found comprehensive test data on the flexural strength, deflection, and cracking behavior of thin sheets of 6 to 13 mm thickness reinforced with a wide range of reinforcing elements. P. Paramasivam (5) stated that the Ferrocement is a type of thin-wall reinforced concrete with high performance characteristics such as high tensile strength to weight ratio, ductility, and impact resistance. K C G Ong, C P Teo, C H Shum, L H J Wong, S T Tan and C T Tam (6) found the use of microwave technology to speed up the production of precast ferrocement secondary roofing slabs. R Sri Ravindrarajah, M. J. Camporeale and C. C. Caraballo (7) found the Flexural Creep of Ferrocement -Polystyrene Concrete Composite. Ashish Dubey (8) also found Textile-reinforced concrete (TRC) is a high-performance composite material in which technical textiles composed of high-performance reinforcement fibers are embedded in a cementations matrix.
5. EXPERIMENTAL PROGRAMME
5.1 Materials
Ordinary Portland cement (Ultra tech cement) of 53 grades conforming to IS: 12269(9) were used. Locally available natural sand was used. Specific gravity and fineness modulus were found to be 2.60 and 2.68 respectively. It could be seen that sand confirms to zone II, as per IS 383-1970(10).Potable water was used for mixing and curing. Fly ash was obtained from "Hyderabad Industries private limited", Hyderabad, which was originally obtained from Raichur thermal power plant, Karnataka.
5.2 Physical and Chemical Properties of Materials
Physical properties of cement as per IS 4031 (Part-II)-1988(11), and fly ash as per IS 3812-1999(12), are tested at Indian Institute of Chemical Technology, Hyderabad. Chemical properties of cement (as per
IS 12269) and fly ash (as per IS 3812-1999) are tested at Indian Institute of Chemical Technology, Hyderabad.
5.3 Casting and Curing of Test Specimens
The specimens of prisms (l00 mm x 100 mm x 300 mm) 4 No.s and Standard cylinders (100 mm diameter x 50 mm height) 4 No.s were cast per a day, for 9 days. In out of 72 specimens, half of the specimens cement was replaced by fly ash (0%, 5%, 10%, 15%, 20%, 25% and 30%) with varying layers of 4 layers, 6 layers and 8 layers and half of the specimen's mixes with polymer were cast.
5.4 Tests for permeability
The permeability test was conducted in the 3 cell permeability apparatus. The equipments meet the requirements of IS: 2645 and 1727(13, 14) and is for determining the permeability of water in the mortar prepared and cured under specific conditions.
The coefficient of permeability (K) is found using the formula * =
WATH Where,
Q = quantity of water collected in kg
S = thickness of the specimen in m
W = density of water in kg/m3
A = area of cross section of the specimen in m2
T = time of collection in seconds
H = net pressure head on the specimens in m of water
5.5 Depth of penetration method
In case of specimens where no discharge is found even after 14 days, the coefficient of permeability can be calculated by using the Depth of Penetration Method. These specimens should be drilled in the centre to find the depth of penetration.
The coefficient of permeability can be calculated from the formula given below.
Where,
D = depth of penetration in m P = porosity of concrete T = time taken in sec to penetrate to depth D H = head of water in m
5.6 Impressed voltage test set up
In order to accelerate corrosion in Ferro cement specimens, impressed voltage test was done. On the date of testing i.e., after 28 days of curing, the cube specimens were removed from the water tank and placed on flat surface for 10 minutes to wipe off the surface water and grit and also removes the projecting fines on the surface of the specimens. The specimens are partially immersed in 5% sodium chloride solution. All the details are presented in plates 1-5.
5.7 Determination of pH content of cover motor
To determine the pH content of cover Ferro cement motor, pH digital meter was used. About 3.75 grams of dust was collected from the near the main bar in the cover depth and mixed with 75 ml of distilled water.
5.8 Determination of chloride content of cover motor
To determine the chloride content, volumetric method was used. As per this method, the burette solution was silver nitrate solution and the dust dissolved in distilled water was taken as pipette solution. The indicator used is potassium chromate solution. This was prepared by adding 5 grams of potassium chromate with 100ml of distilled water. The chloride content is calculated as follows:
, „ , Volumeof AgNo3 x Normalityof AgNo3 x 35.5x 1000
Chloride content per gm of dust =-3-3-
Volumeof the sample taken
5.9 Multiple regression non-linear analysis
To understand the possible association between two [or more] explanatory variables X1, X2 [in our problem, Permeability and Volume of reinforcement] and a single response variable Y [Time for first crack], one performs a multiple regression. The result of a multiple regression is a linear equation of the form
Ypred = a + (b1) X1 + (b2) X2
A predicted Y value can be obtained from a particular X1 observation and X2 observation by using the regression equation in the usual way. Excel can help here. Under the Tools -> Data Analysis menu you can choose Regression. This allows you to do a multiple regression. The data for the X1, X2 [etc], and Y variables should already be entered into columns.
5.10 Non-linear scatter plots and multiple regressions
Imagine a scatter plot suggests that the association between two variables X and Y is non-linear. Perhaps the scatter plot looks more like a parabola. This might indicate a quadratic relationship between X and Y [that is, Ypred = a + (b1)X1 + (b2)X2 ]. In this case, you can use multiple regressions to fit a parabola to the data. To do this, you would set up three columns of data: X1, X2, and Y. With these, you would then have Excel carry out a multiple regression for Y on the variables X1 and X2.
6. Test Results and Discussions
The permeability test indicates a decreasing trend of coefficient of permeability when the percentage of polymer cement ratio and Fly ash is increased. Table 3 and Table 4 show the coefficient of permeability recorded during the test.
According to the result, the highest coefficient of permeability obtained was 15.93x10-13 m/sec and the lowest coefficient of permeability was 0.377x10-13 m/sec.
6.1 Impressed Voltage Test Results and Analysis
The impressed voltage indicates the time taken for cracking of polymer and flyash modified Ferro cement elements. If an increasing Volume fraction reinforcement, the trend of the time taken for cracking
is decreased. It shows that the time taken for cracking is increasing as the percentage of polymer and fly ash is increased. The time taken for maximum cracking is 119 hours and minimum was 73 hours for the fly ash modified specimens.
The time taken for cracking of specimen is 92 hours, and the lowest is 61 hours for the polymer modified specimens. The graphical representations of the variation of time taken for crack occurrence are presented. The graphs show an increasing trend when the percentage of polymer in the cement of polymer modified specimens is increasing for different layers of chicken mesh. Each curve represent the increasing amount of polymer from 0% to 12.5% in cement of polymer modified Ferro cement elements for the 4 layers, 6 layers and 8 layers of chicken mesh. From the results obtained; we can say that the following equation was derived for the time taken for first crack by doing the multiple regression non linear analysis.
T = 165 - 300P - 20Vf
Where,
T = Time for first crack in hrs
P = Coefficient of permeability of cement mortar in 10-11 m/sec and Vf= Volume fraction of reinforcement
6.2 pH Content of Cover Cement Motor Test Result and Analysis
It shows that the pH content of cover is decreasing as the percentage of Polymer and fly ash is increased. The highest pH content of cover cement motor is 12.88 and the lowest is 12.42. From the results obtained, we can say that the pH content of cover cement motor is getting higher due to the increasing of polymer and fly ash used. All the test result values are presented in table 1-6.
7. CONCLUSIONS
1. The coefficient of permeability of modified ferrocement decreases with the increase in polymer cement ratio upto 12.5% and flyash replacement levels upto 30%.
2. The time taken for initiation of crack for ordinary ferrocement specimens is less compared to that of polymer and flyash specimens.
3. The time taken for initiation of crack in flyash modified ferrocement is more in case the replacement of cement by flyash by 0% to 30%, when compared to the addition of polymer by 0% to 12.5% in polymer modified ferrocement.
4. As the percentages of polymer (0% to 12.5%) and flyash (0% to 30%) increased, the resistance to current of ferrocement elements increased.
5. The pH value of cement motor at top surface of specimen in flyash modified ferrocement is more compared to polymer modified ferrocement.
6. The chloride content of cement motor at top surface of specimen in the beams cast with flyash modified ferrocement is less than that of beams cast with polymer modified ferro cement and ordinary ferrocement.
References
[1] Joseph-Louis Lambot's., "Ferrocement Applications in Developing Countries," National Academy of Sciences, Vol. 4, No. 89, January 2007.
[2] 549R-97, "State of the Art Report on Ferrocement", Reported by ACI Committee, 1997.
[3] Neelamegam. M., Ohama.Y., Demura.K., Suzuki.S., and Shirai.S., "Deformation and Durability of Polymer-Impregnated Ferrocement", Journal Proceedings, Vol.81, No.6, November 1984, pp. 551-559.
[4] 4 .Swamy. R. N., and Hussin. M. W., "Flexural Behavior of Thin Fiber Reinforced and Ferrocement Sheets", Special Publication, Vol. 124, September 1990, pp. 323-356.
[5] Paramasivam. P "Applications for Urban Environment", Special Publication, Vol.159, February 1996, pp 95-104.
[6] Ong. K. C. G., Teo. C. P., Shum. C. H.., Wong. L. H. J., Tan. S.T.,. and Tam. C. T., "Temperature Controlled Microwave Accelerated Curing of Precast Ferrocement Secondary Roofing Slabs", Special Publication, Vol.224, December 2004, pp 127-144.
[7] Ravindrarajah. R., Camporeale. M. J., and Caraballo. C. C., "Flexural Creep of Ferrocement - Polystyrene Concrete Composite", ADCOMP'96,Second International Conference on Advances in Composites, Bangalore, India, 18th -20th December 1996.
[8] Ashish Dubey., "Textile Reinforced Concrete", Special Publication, Vol. 250, March 2008.
[9] IS: 12269-1987, "Code of Specification for 53 Grade Ordinary Portland Cement", 1999.
[10] IS: 383-1970, "Code of Specification for Coarse and Fine Aggregates from Natural Sources for Concrete", 1997.
[11] IS: 4031(part 2), "Code of Practice for Methods of Physical Tests for Hydraulic Cement", 1999.
[12] IS: 3812-1981, "Code of Specification for Fly Ash for use as Pozzolana and Admixture", 1999.
[13] 13. IS: 2645, "Code of Practice for Integral Waterproofing Compounds for Cement Motor and Concrete-Specification", 2003.
[14] 14.IS: 1727-1967, "Code of Practice for Methods of Test for Pozzolanic Materials",1999.
Table 1 Time for First Crack of Polymer Modified Specimens
Time for Cracking in Hours
Used 4 Layers of Chicken mesh 6 Layers of Chicken mesh 8 Layers of Chicken mesh
0.0 69 65 61
2.5 75 68 67
5.0 79 72 69
7.5 85 78 74
10.0 89 81 76
12.5 92 82 80
Table 2 Time for First Crack of Flyash Modified Specimens
Time for Cracking in Hours
% ot Flyash used 4 Layers of Chicken mesh 6 Layers of Chicken mesh 8 Layers of Chicken mesh
5 84 78 69
10 91 84 73
15 101 90 81
20 109 105 87
25 114 108 92
30 119 112 109
Table 3 Coefficient of Permeability of Polymer Modified Cement Mortar
% of Polymer added Quantity of water collected in kg Time Taken in Sec Coefficient of permeability In m/sec
0.0 0.126 25200 15.93x10-13
Vi BHIKSHMA et al. /Procedia Engineering 14 (2011) 2642-2649
2.5 0.0822 25200 10.38x10-13
5.0 0.0539 25200 6.812x10-13
7.5 0.0419 25200 5.303x10-13
10.0 0.0225 25200 2.846x10-13
12.5 0.0151 25200 1.908x10-13
Table 4 Coefficient of Permeability of Fly Ash Modified Cement Mortar
% of Fly Ash added Quantity of water collected in Kg Time Taken in Sec Cvefficient vf Permeability In mSsec
5 0.0419 25200 5.303x10-13
10 0.0268 25200 3.394x10-13
15 0.0186 25200 2.354x10-13
20 0.0119 25200 1.508x10-13
25 0.0047 25200 0.594x10-13
30 0.003 25200 0.377x10-13
Table 5 pH value and Chlvride Cvntent vf Flyash Mv^f^ Ferro cement Specimens
pH value Chloride content in mg/gm
% of Flyash 4 Layers of 6 Layers of 8 Layers of 4 Layers of 6 Layers of 8 Layers of
Chicken mesh Chicken mesh Chicken mesh Chicken mesh Chicken mesh Chicken mesh
5.0 12.67 12.59 12.42 16.47 17.61 18.18
10.0 12.74 12.72 12.49 14.77 15.90 17.04
15.0 12.78 12.75 12.55 13.63 14.77 15.34
20.0 12.81 12.79 12.69 11.93 13.06 14.20
25.0 12.83 12.82 12.74 10.79 12.50 13.06
Table 6 pH Value and Chlvride Ccntent vf Pvlymer McdiAed Ferrv cement specimens
pH value_Chloride content in mg/gm
% vf Pvlymer used 4 Layers of 6 Layers of 8 Layers of 4 Layers of 6 Layers of 8 Layers of
Chicken mesh Chicken mesh Chicken mesh Chicken mesh Chicken mesh Chicken mesh
0.0 11.87 11.85 11.81 21.01 22.72 23.86
2.5 12.11 12.08 12.01 19.88 21.58 22.15
5.0 12.17 12.15 12.12 17.61 21.02 20.45
7.5 12.22 12.19 12.14 16.47 19.31 19.88
10.0 12.38 12.33 12.30 15.34 18.18 18.74
12.5 12.42 12.39 12.34 14.20 17.04 17.61
Fig. 1: Plate 1 Ferro cement Specimens
Fig.2: Plate 2 Specimen for Permeability of Cement Motor
Fig. 3: Plate 3 Test for Permeability of Cement Motor
Fig. 4: Plate 4 Test for Impressed Voltage Test of Ferro Cement Specimens
Fig. 5: Plate 5 Test for Chloride Contents of Cover Motor
