|Year : 2014 | Volume
| Issue : 2 | Page : 123-126
Flexural Strengthening of Reinforced Concrete Beams using Ferrocement Laminates with Partial Replacement of Fine Aggregate by Steel Slag
J Sridhar1, R Malathy2, RK Sangeetha1
1 Department of Civil Engineering, K.S. Rangasamy College of Technology, Tiruchengode, Namakkal, Tamil Nadu, India
2 Department of Civil Engineering, Sona College of Technology, Salem, Tamil Nadu, India
|Date of Web Publication||19-Sep-2014|
Department of Civil Engineering, K.S. Rangasamy College of Technology, Tiruchengode, Namakkal, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
This paper presents the investigation report of flexural behavior of reinforced concrete (RC) beams strengthened with ferrocement laminates using steel slag from the steel industry as a partial replacement material for fine aggregate. The parameter varied in this study includes volume fraction of mesh reinforcement 1.88% and 2.35% and percentage replacement of steel slag (0% and 30%) to fine aggregate in ferrocement laminate. For experimental investigation, five RC beams of size 1220 mm × 100 mm × 150 mm and four ferrocement laminates of size 1220 mm × 100 mm × 25 mm with different parameters were cast. Four beams were strengthened with ferrocement laminates using the epoxy resin as a bonding agent. One control specimen and four strengthened beams were subjected to flexural test under two-point loading. The observations were focused on first crack load, ultimate load and mid span deflection. From the investigation result, it was concluded that the beams strengthened with ferrocement having a volume fraction of 2.35% and 30% replacement of steel slag increases the load carrying capacity significantly under flexural load. Furthermore, other mechanical properties such as ductility and energy absorption capacity were found to be increased for specimens with 2.35% of volume fraction of mesh reinforcement and 30% of steel slag replacement.
Keywords: Ferrocement, flexural test, reinforced concrete beams, steel slag, strengthening, volume fraction
|How to cite this article:|
Sridhar J, Malathy R, Sangeetha R K. Flexural Strengthening of Reinforced Concrete Beams using Ferrocement Laminates with Partial Replacement of Fine Aggregate by Steel Slag
. J Eng Technol 2014;4:123-6
|How to cite this URL:|
Sridhar J, Malathy R, Sangeetha R K. Flexural Strengthening of Reinforced Concrete Beams using Ferrocement Laminates with Partial Replacement of Fine Aggregate by Steel Slag
. J Eng Technol [serial online] 2014 [cited 2019 Sep 18];4:123-6. Available from: http://www.onlinejet.net/text.asp?2014/4/2/123/141205
| 1. Introduction|| |
The strengthening of structures has been practiced and accepted as a viable means of improving the serviceability, performance and upgrading the load carrying capacity of structures. Strengthening may be needed to allow the structure to resist loads that are not anticipated in their original design. Additional strength may be needed due to deficiency in the structure's ability to carry the original design loads. Numbers of techniques are available to strengthen different type of structures. The selection of strengthening technique depends on one or more of the following criteria, accessibility, availability of materials, equipment, qualified contractors, construction, maintenance and life cycle costs, magnitude of strength increase, etc.
Ferrocement is one of the recently developing strengthening materials for concrete structures. The following definition of ferrocement was given by ACI Committee 549  in a state of the art report on ferrocement. Ferrocement is a type of thin wall reinforced concrete (RC) commonly constructed by hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small size wire mesh. Naaman , described that, in thin concrete products, ferrocement plays the link between RC and fiber RC. Anwar et al.  presented a design chart, which describes step by step procedure for rehabilitation of RC structural beam elements using ferrocement.
Fahmy et al.  described the method for repairing RC beams by ferrocement. Paramasivam et al.  showed that the flexural strength was increased for RC beams strengthened with ferrocement laminates. Ganesan and Thadahil  have carried out the experimental investigation to study the effect of ferrocement jacketing on strength and behavior of distressed RC beams. Ong et al.  have reported the flexural behavior of RC beams strengthened and repaired with ferrocement laminates attached onto the tension face of the beams. Masood et al.  investigated the performance of RC and fiber reinforced concrete beams rehabilitated by ferrocement. Bansal et al.  have focused on the behavior of joints between ferrocement and RC beams. Rajkumar and Vidivelli  studied the performance of SBR latex modified ferrocement for repairing RC beams. Seshu  assessed the flexural strength of ferrocement confined RC beams. Vidivelli and Jeyasehar  studied the behavior of corrosion damaged RC beams rehabilitated with ferrocement laminates. Reddy  showed that the load carrying capacity was increased with the increase in number of layers of mesh reinforcement. In this current investigation, steel slag obtained from the steel industry was used as a replacement material for fine aggregate in ferrocement laminates and the laminates were attached to the tension face of the RC beams to increase its flexural load carrying capacity. The parameter varied are volume fraction of mesh reinforcement and replacement of fine aggregate by steel slag in ferrocement laminates, which were optimized based on the results obtained by Sridhar and Malathy  .
| 2. Experimental Program|| |
To carry out the investigation, five prototype beams of size 1220 mm × 100 mm × 150 mm were casted. Out of this, one beam was used as a perfect beam and remaining four beams were used for strengthening purpose. For the strengthening of beams, four ferrocement laminates of size 1220 mm × 100 mm × 25 mm with two different parameters were cast. The control beam and strengthened beams were tested under two-point loading over an effective span of 1100 mm. Details of test specimens are shown in [Table 1].
2.1.1 RC beams
The concrete mix proportion of 1:1.5:3 with water cement ratio 0.5 was used. Two 10 mm dia bars were used as tension reinforcement and as hanger bars. For shear reinforcement, 6 mm dia two legged stirrups were used.
2.1.2 Ferrocement laminates
The mortar mix proportion was 1:2 with water cement ratio of 0.4. The mortar was prepared with and without replacement of fine aggregate by steel slag. For replacement of fine aggregate, steel slag was obtained in fine form from base oxygen furnace of Agni Steels Private Ltd., Ingur, Tamil Nadu, India. Galvanized Square Weld Mesh was used. Commercially available CERA BOND EP Epoxy resin was used for bonding purpose.
2.2 Process of strengthening
The beams and laminates were cured for 28 days. After curing, all the specimens were allowed to surface dry for 24 h at room temperature. The tension side of the beams and bonding face of the ferrocement laminates were roughened using a wire brush to remove the surface laitance and to expose the rough surface. After surface preparation, the adhesive component, i.e., epoxy resin were mixed thoroughly and applied to the prepared surface of beams and ferrocement laminates using trowel. Then, ferrocement laminates were placed in position. The beams strengthened with ferrocement laminates were allowed to cure in the air for 7 days.
2.3 Testing of specimens
After 7 days of air curing, the control beam and strengthened beams were subject to flexural test under two-point loading with flexural span of 366.70 mm in Universal Testing Machine of 100 ton capacity. All the beams were simply supported with an effective span of 1100 mm. Hydraulic jack with 100 ton capacity was used to apply load. The load cell having a capacity of 5 ton was used to measure the applied load. The load was applied in increments of 2 kN and at each stage mid span deflection was noted using a dial gauge having a least count of 0.01 mm. The initializations of flexural crack were carefully observed and corresponding load and deflection were noted. The ultimate load and the mode of failure of the specimen were noted. The detail of test setup is shown in [Figure 1].
| 3. Results and Discussion|| |
The results obtained from the experimental investigation are tabulated in [Table 2]. The results are discussed as follows.
3.1 First crack load and ultimate load
From [Table 2], it is clear that first crack load and ultimate load were found to be a maximum for higher volume fraction (Vr) and 30% replacement of steel slag by weight of fine aggregate. In the case of RC beams strengthened with ferrocement laminates the first crack load was found to be increased by 26.94% for FB01, 28.57% for FB02, 39.18% for FB03 and 83.67% for FB04 with reference to control beam. Similarly, the ultimate load was found to be enhanced by 10.96% for FB01, 15.34% for FB02, 21.23% for FB03 and 33.97% for FB04 with reference to control beam.
3.2 Ductility factor
Ductility is the ratio between deflections at ultimate load to that at the onset of yielding. The ductility ratio of strengthened beams varies between 1.83 and 2.93. The ductility factor was found to be increased by 32.24%, 57.92%, 52.45% and 60.10% for FB01, FB02, FB03 and FB04 respectively as that of control specimen. The values are presented in [Table 2].
3.3 Energy absorption
Energy absorption is the area under the load deflection diagram. The strengthened beams exhibit an increase in energy absorption capacity with reference to control specimen. The energy absorption capacity was found to be increased by 18.58% for FB01, 22.12% for FB02, 22.35% for FB03 and 23.89% for FB04 as that of control specimen. The values are presented in [Table 2].
3.4 Load versus deflection comparison
From the load versus deflection curves, shown graphically in [Figure 2]. It is seen that when the steel slag content increases, the deflection tends to reduce after first crack load for all specimens irrespective of volume fraction of mesh reinforcement. From an overall assessment, i.e., considering maximum load carried, deflection best results was obtained when steel slag content in the mortar matrix was about 30%.
3.5 Mid span deflection
In the case of RC beams strengthened with ferrocement laminates, the deflection was found to be reduced by 24.50%, 25.64%, 34.22% and 46.43% for FB01, FB02, FB03, FB04 respectively with reference to control beam.
3.6 Mode of failure
Flexural failure was observed for all specimens. In perfect beams, cracks were wide and few in numbers. In ferrocement encased beams, the cracks were more in numbers and the crack width was also small which is shown in [Figure 3] and [Figure 4].
3.7 Overall performance
The overall performance of the beams has been evaluated by considering the equivalent forces by using the energy and deflection approaches as predicted by Rajkumar and Vidivelli  , which is given in [Table 2] (in terms of effectiveness factor).
where Ae is the equivalent area under load deflection curve, Py the load at yield point, Pu the load at ultimate stage, Δy the deflection at yield point, Δu the deflection at ultimate stage, Pe1 the equivalent elastic force using energy approach, Pe2 the equivalent elastic force using deflection approach, F1 the effectiveness factor using energy approach and F2 is the effectiveness factor using deflection approach.
The effectiveness factor F1 for beams strengthened with ferrocement laminates varies between 1.56 and 2.83 and F2 varies between 1.70 and 2.98.
| 4. Conclusion|| |
Within the scope of the flexural test of this research, the following conclusions are drawn:
- Incorporation of steel slag in ferrocement laminates with volume fraction 2.35% and steel slag replacement 30% have highly reduced the deflection when compared to other specimens. The addition of ferrocement laminate to the tension face of the RC beams substantially delays the first crack load.
- All the strengthened beams behaves elastically up to 90% of ultimate moment and this indicates ductile nature of the strengthened beam
- The epoxy resin used for bonding the ferrocement laminates to the tension face of the RC beams ensures that the bond line does not break before failure of beam.
- The failure of the composite beam is characterized by development of flexural cracks over the tension zone. The spacing of the cracks is also reduced for strengthened beam. This indicates the better stress distribution.
- Overall all performance of RC beams strengthened with volume fraction of mesh reinforcement 2.35% and replacement of fine aggregate with steel slag by 30% are found to be high
- For beams strengthened with volume fraction of mesh reinforcement 2.35% and 30% replacement of fine aggregate by steel slag, ultimate load is increased by 83.67% than that of control specimen. Similarly, deflection is reduced up to 46.43% than that of control specimen.
| References|| |
|1.||ACI 549, "Guide for the Design, Construction and Repair of Ferrocement," Michigan: American Concrete Institute; 1988. |
|2.||A. E. Naaman, "Ferrocement and Laminate Cementitious Composites," USA: Techno Press 3000; 2000. |
|3.||A. E. Naaman, "Ferrocement and thin fibre reinforced cement composites: Looking back, looking ahead," Proceedings, FERRO-7, Seventh International Symposium on 'Ferrocement and Thin Reinforced Cement Composites', Singapore: National University of Singapore; 2001. |
|4.||A. W. Anwar, P. Nimityongskul, R. P. Pama, and L. Robles-Austriaco, "Method of rehabilitation of structural beam elements using ferrocement," Journal of Ferrocement, Vol. 21, pp. 229-234, 1991. |
|5.||E. H. Fahmy, Y. B. Shaheen, and Y. S. Korany, "Repairing reinforced concrete beams by ferrocement," Journal of Ferrocement, Vol. 27, pp. 19-32, 1997. |
|6.||P. Paramasivam, K. C. Ong, and C. T. Lim, "Ferrocement laminates for strengthening RC T-Beams," Cement and Concrete Composites, Vol. 16, pp. 143-152, 1994. |
|7.||N. Ganesan, and S. P. Thadahil, "Rehabilitation of reinforced concrete flexural elements using ferrocement jacketing," Journal of Structural Engineering, Vol. 31, pp. 275-280, 2005. |
|8.||K. C. Ong, P. Paramasivam, and C. T. Lim, "Flexural strengthening of reinforced concrete beams using ferrocement laminates," Journal of Ferrocement, Vol. 22, pp. 331-342, 1992. |
|9.||A. Masood, M. Arif, S. Akhtar, and M. Haquie, "Rehabilitation of RC and FRC beams by ferrocement - An experimental investigation," Journal of Structural Engineering, Vol. 31, pp. 321-326, 2005. |
|10.||P. P. Bansal, M. Kumar, M. Kaur, and S. K. Kaushik, "Effect of different bonding agent on strength of retrofitted beams using ferrocement laminates," The Indian Concrete Journal, pp. 36-41, 2006. |
|11.||D. Rajkumar, and B. Vidivelli, "Performance of SBR latex modified ferrocement for repairing reinforced concrete beams," Australian Journal of Basic and Applied Sciences, Vol. 4, pp. 520-531, 2010. |
|12.||D. R. Seshu, "Flexural strength assessment of ferrocement confined reinforced concrete (FCRC) beams," Journal of Ferrocement, Vol. 31, pp. 53-63, 2011. |
|13.||B. Vidivelli, and C. A. Jeyasehar, "Rehabilitation of corrosion damaged RC beams with ferrocement laminates," The Indian Concrete Journal, Vol. 41, pp. 51-55, 2005. |
|14.||M. V. Reddy, "Retrofitting of shear deficient rc beams using ferrocement jacketing," IE(I) Journal - CV, Vol. 92, pp. 42-48, 2011. |
|15.||J. Sridhar, and R. Malathy, "Study on compressive strength of cement mortar with partial replacement of fine aggregate by steel slag for ferrocement laminates," International Journal of Earth Sciences and Engineering, Vol. 4, pp. 1139-1153, 2011. |
| Authors|| |
Mr. J. Sridhar obtained his B.E and M.E degree courses in Civil and Structural Engineering from Kongu Engineering College and Thiagarajar College of Engineering, India repectively.He has a teaching experience of five years and currently working as Assistant Professor, Department of Civil Engineering, K.S.Ranagasamy College of Technology, Tiruchengode, India. His area of interest in research is "Strengthening of Reinforced concrete elements using Ferrocement laminates" and has published papers in national and international journals and conferences.
Dr. R. Malathy obtained PhD in 2005 from Bharathiyar University, India. She has a teaching experience of 19 years in engineering colleges and is presently Professor & Dean (R&D), Department of Civil Engineering, Sona College of Technology, Salem, India.She has authored three books and she is a life member of various professional bodies. She has been actively engaged in R&D in the areas of High performance concrete, repair and rehabilitation of Reinforced concrete structures. The outcome of the research carried out has been published in journals and conferences.
Ms. R. K. Sangeetha has completed her B.E in Civil Engineering from Kongu Engineering College and doing her M. E degree course from K.S.Rangasamy College of Technology, India. Her area of interest is "strengthening of Concrete Structures using ferrocement laminates". She has presented paper in international conferences.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]