Using feathers as fiber reinforcement produces a unique concrete mix. It is lighter in weight and stronger in flexure than ordinary portland cement plain concrete.
Feather,Fiber Reinforced Concrete I
mproving concrete properties such as strength and durability by adding fibers to the mix has become a common practice.lm5 Recent advances in research and technology in obtaining optimal mix designs for fiber reinforced concrete (FRC) have increased its use in special construction areas such as nuclear power plants, but its commercial applications are still limited due to FRC’s increased costs. The increased mix cost is due mainly to the high cost of steel and glass fibers. A FRC that uses natural fibers would be cheap and would have a positive environmental impact. Using vegetable and wood fibers was an early attempt at using natural fibers in a concrete mix.6 Problems associated with using natural fibers were addressed,6V7 and a method of preventing deterioration of the fibers was outlined. One type of natural fiber that seemed promising was feathers. Feathers wasted in the process of food production of chickens have increased landfill waste and are adding to our environmental problems. Using these waste feathers in concrete would contribute to cleaning the environment. Using feathers as fiber reinforcement produces a unique concrete mix. It is lighter in weight and stronger in flexure than ordinary portland cement plain concrete. The literature contains advanced research and technology on lightweight concrete.8-‘2 Using lightweight aggregates and some additive materials are the current practice for obtaining lightweight concrete, but this increases the cost of the mixed concrete. Using feathers in the mix design produces cheaper lightweight concrete. The long-term durability of the mix is being investigated to validate the technique.
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Experimental investigation Feathers collected from chicken shops were washed, cleaned, screened, and dried. They were not chemically treated. Three volumetric ratios of 1, 2, and 3 percent of feathers were used in this investigation. The volume of feathers was determined by considering their density, which was determined by dividing the weight of a sample feather by its volume. The volume of the feather was determined by finding the change in water volume when it was submerged. Three sets of six standard 6 x 12 in. (150 x 300 mm) concrete cylinders were tested for each volumetric ratio. The concrete mix was fixed at 1:2:4 with a w/c of 0.6 and Type I portland cement. The aggregates were washed and oven dried before they were used. Each set of cylinders was tested on different dates. The first set was tested at 14 days, the second set was tested at 28 days, and the last set was tested at 56 days. For each set of cylinders, three cylinders were tested under uniaxial compression and another three cylinders were tested in a split tension test. Three control specimens were tested at 14, 28, and 56 days to monitor changes in the compressive strength and another three control cylinders were tested at 14, 28, and 56 days to monitor changes in tensile strength. The compressive strength of the standard cylinders was obtained by using an MTS machine equipped with a moving head that advanced at a rate of 0.078 in. (2 mm) per hour. The force was applied in increments of 25 kN (5.6 kip) At each increment, the deflection of a 6 in. (150 mm) gauge attached to the cylinder’s side was recorded. The ma-
I4 days
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Fig. 1 - The compressive load strain curves for concrete without feathers. June 1994
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Fig. 2 -- Comparison between the compressive strength at 28 days for all ratios tested. 33
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Fig. 3 - The compressive load strain curves for concrete
The same MTS machine was used to perform the split tensile testing. The load was applied to failure at the same rate as that of the compressive test. Only the final failure tensile strength was recorded. The flexural strength of feather FRC was evaluated by performing tests on 6 x 6 x 30 in. (150 x 150 x 750 mm) beam specimens at 14,28, and 56 days. Three specimens were tested for each volumetric ratio. The beams were tested in flexure under two point loading. The spacing between the load points was 6 in. (150 mm). Three control beams were tested to monitor the flexural strength changes for each date. In the mix with 1 percent feathers, 0.0046 in.‘/ft” (2.6 cm3/m”) of type mighty 150 superplasticizer was added to produce a workable mix. The workability of the mix was low compared to ordinary portland cement concrete. The concrete mix with 2 percent feathers was harsher than that of the 1 percent feather mix, so more superplasticizer (0.009 in.3/ft3 [5 cm3/m3]) was added to increase the workability of the mix. The concrete mix that contained 3 percent feathers was very harsh and a lot more superplasticizer was added (0.015 in3/ft3 [9 cm3/m3]). The workability was severe and a lot of attention was focused on casting and vibrating the specimens. The difficulty in the workability of the mixed concrete led to limiting the investigation to the mentioned volumetric ratios.
Results z
. Welght of beariS l Weight of cylinders
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lo00
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Fig. 4 - The reduction in weight of the concrete with the
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Fig. 5 - Modulus of rupture versus the feather ratios.
chine’s capability of shutting down at failure of the cylinder allowed a reading of deflection at failure. 0%”
The relationship of the compressive load versus the strain is shown in Fig. 1 to 3. Fig. 1 shows the change in the compressive strength over time of the concrete without feathers. Fig. 2 shows the 28 day compressive strength of the concretes with different feather ratios. The addition of 1 percent of feathers resulted in a 13 percent reduction in the failure strength. Fig. 3 shows the change in the concrete compressive strength with age for concrete containing 1 percent feathers. The 56 day maximum load was 3 15 kN (7 1 kip) at 0.00325 strain, and the 28 day maximum load was 270 kN (61 kip) at 0.00320 strain. The 14 day strength was 165 kN (37 kip) at 0.0018 strain. The weight of each tested specimen was recorded to check the reduction in weight of the concrete mix (Fig. 4). At each date, the average of three specimens was used. Fig. 5 shows the increase in the flexural strength of the cylinders with the addition of 1 percent of feathers. The increase in strength was noted at all ages of concrete tested (14, 28, and 56 days). The concrete mix with 2 percent of feathers revealed an increase in the flexural strength at 56 days. However, the flexural strength of the 2 percent mix was lower at ages 14 and 28 days than that of the plain concrete. By increasing the feather volume ratios, the modulus of rupture decreased. Fig. 6 shows the reduction in split tensile strength for all ratios tested. The reduction was noted at all ages of the tested concrete. The reduction in split tensile strength may be explained by the decaying of the feathers and reduction in the feather strength. Feather decay was noted by inspecting the failure surfaces of the tested specimen. Where small sized feathers (less than l/2 in. [ 13 mm]) were completely dissolved in the concrete, feathers that remained hanging out of the failure surfaces exhibited no resistance to pullout. The same behavior was noted for the compressive strength where the strength was reduced with higher amounts of feathers. The behavior of the compressive strength versus the ratios of feathers added is shown in Fig. 7. Concrete International
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I 56 days
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Fig. 6 - Split strength versus the ratio of feathers.
Fio. 7 - Compressive strenath versus feather ratios.
The failure surfaces of the concrete cylinders were evaluated and inspected. The feathers had lost most of their strength and decay was severe. Decaying of the feathers is the focus of a new research project. The authors are in the process of developing a technique to treat the feathers and the concrete mix to prevent such decaying. If they are successful, feather FRC may become an answer to certain environmental and construction problems.
4. Chapman, Ralph A., and Shah, Surendra P., “Early-Age Bond Strength in Reinforced Concrete,” ACI Materials Journal, V. 84, No. 6, Nov.-Dec. 1987 pp. 501-510.
Conclusions The results of the testing indicated that the new mixes had lower values in compressive and tensile strengths than those of plain concrete. The flexural strength was higher in the concrete with 1 percent feathers, and the flexural strength was higher in the concrete with 2 percent feathers at age 56 days. However, the flexural strength reduced when the feather percentage was increased to higher than 2 percent. The increases in the flexural strength provides promise for the technique to be used in concrete structures under impact loading. If the feathers were treated chemically to prevent the short and long term decaying, both compressive and tensile strength could be improved. The proposed new concrete has some promise in obtaining a concrete mix with a higher flexural strength and a lighter weight. The long term problems associated with the new technique are: the durability of the concrete, the decay and reduction in fiber strength, the chemical reaction between the ftber and concrete, and the water absorbed by the feathers due to pipe action. These problems are being studied by the authors. Acknowledgements The work presented in this paper was supported by Kuwait University grant EV 06 1.
References
1. Shah, S., and Batson, F., editors, Fiber Reinforced Concrete Properties and Applications, SP-105, American Concrete Institute, Detroit, 1987. 2. Swamy, R.; Jones, R.; and Chiam, T., “Shear Transfer in Steel Fiber Reinforced Concrete,” Fiber Reinforced Concreie Properties and Applications. SP-105, American Concrete Institute, Detroit, 1987, pp. 565-592. 3. Fanella, David A., and Naaman, Antoine E., “Stress-Strain Properties of Fiber Reinforced Mortar in Compression,” Proceedings, AC1 Journal, V. 82, No. 4, Jul.-Aug. 1985, pp. 474-483.
June 1994
5. Hishioka, K.; Yamakawa, S.; Kirakawa, K.; and Akihama, Zntemational Symposium on Testing an Test Methods of Fiber Cement Composites, Sheffield, 1978. 6. Proceedings of the Second International RILEM Symposium, Vegetable Plants and Their Fibres as Building Materialsi Chapman and Hall, First Edition, 1990. 7. Swamy, R. N., “Natural Fibre Reinforced Cement and Concrete,” Concrete Technology and Design, V. 5, Blackie and Son, Ltd., London, 1988. 8. AC1 Committee 2 I 1, “Standard Practice for Selecting Proportions for Structural Lightweight Concrete,” AC1 211.1-g I, American Concrete Institute, Detroit, 1981, pp. 18-27. 9. Slate, Floyd 0.; Nilson, Arthur H.; and Mardinez, Salvador, “Mechanical Properties of High-Strength and Lightweight Concrete,” Proceedings, AC1 Journal, V. 83, no. 4, Jul.-Aug. 1986, pp. 606-613. 10. Wang, P. J.; Shah, S. P.; and Naaman, A. E., “Stress-Strain Chrves of Normal and Lightweight Concrete in Compression,” Proceedings, AC1 Journal, V. 75, No. 11, 1978, pp. 603-611. 11. Hansen, J. A., “Strength of Structural Lightweight Concrete Under Combined Stress,” Journal of the Research and Development Laboratories, Portland Cement association, V. 5, No. 1, Jan. 1963, pp. 39-46. 12. Bresler, Boris, “Lightweight Aggregate Reinforced Concrete Columns,” Lightweight Concrete, AC1 SP-29, American Concrete Institute, Detroit, 1971, pp. 81-130. Received and reviewed under Institute publication policies.
Sameer A. Hamoush is an assistant professor of Civil Engineering at Kuwait University, Kuwait. He obtained his bachelor’s degree in civil engineering from the University of Damascus, Syria, and his Ph.D. from North Carolina State University. Moetar M. El-Hawary is an assistant professor of Civil Engineering at Kuwait University, Kuwait. He obtained his bachelor’s degree in civil engineering from King Saud University, Riyadh, Saudi Arabia, and his master’s and Ph.D. from the University of California at Davis. 35
