Research on the Abrasion Erosion and Impact Resistance of Fiber Concrete Wu, C. Department of Civil Engineering, National Chung-Hsing University (email: hubert.woo@yahoo.com.tw) Liu, Y. Department of Civil and Water Resources Engineering, National Chiayi University (email: yuwen@mail.ncyu.edu.tw) Huang, C. Department of Civil Engineering, Dahan Institute of Technology (email: cdewsx.hch@gmail.com) Yen, T. Department of Civil Engineering, National Chung-Hsing University (email: tyen@dragon.nchu.edu.tw) Hsu, t. Department of Construction, Taipower Company (email: u7872@taipower.com.tw) Abstract The damage mode of the concrete surface of hydraulic structures mainly depends on the structure configuration formations and the environmental conditions. It is impossible to prevent the hydraulic concrete structures from damaging by abrasion erosion and impact of waterborne particles. The research aims to investigate adequate repair materials which could be applied in the repair for the surface layer of hydraulic structures. A new developed flow abrasion test apparatus was developed for test to simulate the abrasion erosion of concrete that takes place in site. Besides, Standard Test Method for Abrasion Resistance of Concrete (ASTM C1138) and Measurement of Properties of Fiber Reinforced Concrete (ACI committee 544) were also adopted in the test. Three kinds of fibers, carbon fiber, glass fiber and steel fiber, were added respectively in the concrete to prepare the specimens. Test results show that the steel fiber concrete performed better abrasion erosion resistance than that of the carbon fiber concrete and glass fiber concrete when the fiber content keeps 1. %. It was found from the underwater abrasion test that the carbon and the glass fiber concrete demonstrate quite similar abrasion erosion resistance, while the steel fiber concrete exhibits the best abrasion resistance, its average abrasion volume is 2 % lower than that of the other two fiber concretes. It was also found from the crack impact test that for the concrete containing 1. % fiber the glass fiber concrete can present the best impact resistance, subsequent by the carbon fiber concrete, and the steel fiber concrete is the worst. Keywords: hydraulic structure, fiber concrete, abrasion erosion, impact resistance 333
1. Introduction Yen (2), Hsu (26) and Webster (1987) pointed that it is impossible to prevent the hydraulic concrete structures from damaging by abrasion erosion and impact of waterborne particles. Using the best quality of concrete surface can merely extend the service life or reduce the repair frequency of hydraulic structures. Hence, the research intends to investigate a technique of using fiber concrete in hydraulic structures to extend their service life. ACI 21R-93 (Erosion of Concrete in Hydraulic Structures) defined the damage molds of the concrete surface of hydraulic structures as erosion by cavitation, erosion by abrasion and erosion by chemical attack. The abrasion erosion is caused mainly by erosion, abrasion and impact actions. Erosion appears in places where rushing stream could reach, the range of erosion is wide but the damage of erosion is less. Abrasion only appears in an active bed-load area, the damage of abrasion appears generally in spillway aprons, stilling basins, sluiceways, drainage conduits and tunnel linings. Impact appears mainly in the concrete surface of the bend of the watercourse due to striking by rock. Papenfus (23), Liu (1981) and Laplante (1991) assessed that the compressive strength of concrete has a high relation to abrasion erosion resistance, namely, the abrasion erosion resistance of concrete increases by increasing the compressive strength of concrete. Besides, Liu (1981), Laplante (1991) and Liu (26) reported that the water-to-cement ratio is an important factor to evaluate the abrasion erosion resistance of concrete. The quality, type and properties of coarse aggregate have an obvious influence on the abrasion erosion resistance. Liu (1981) investigated the abrasion erosion resistance of eight kinds of coarse aggregates by ASTM C1138 method (underwater method). The test results indicated that the abrasion erosion resistance of concrete enhances by increasing the hardness of coarse aggregates when the water-to-cement ratio and compressive strength keep constants. Liu (26) reported that the concrete containing silica fume has better abrasion erosion resistance. Adding fibers in concrete can enhance the toughness and brittleness of concrete. Bayasi (1993) indicated that the cracks in the fiber concrete are blocked and prevented the crack from further development because that the fibers could absorb the deformation energy of concrete and thus benefit the concrete s ductility. Such that, this research aims to investigate the abrasion erosion and impact resistance of fiber concretes using a new developed flow abrasion test apparatus. 334
2. Test Program 2.1 Material 1. Cement (C): Type I portland cement (ASTM C 15). 2. Silica Fume (SF): meets the requirements of ASTM C 124. 3. Blast furnace slag (BFS): the property meets the requirements of ASTM C 989. 4. Fine Aggregate (FA): the specific gravity is 2.62, fineness modulus is 3.1. 5. Coarse Aggregate (CA): the specific gravity is 2.63, maximum size is 2 mm. 6. Carbon Fiber (CF): the specific gravity is 1.8, the physical properties as showed in Table 1. 7. Glass Fiber (GF): the specific gravity is 2.78, the physical properties as showed in Table 2. 8. Steel Fiber (SF): the diameter is.25 mm, the length is 13 mm, the tension strength is 2 kgf/cm 3, the ratio of length-to-diameter is 52. 9. Superplasticizer (SP): meets the requirements of ASTM G-Type1. PH = 2.5, specific gravity = 1.7, solid component = 4.22 % Table 1: Physical Property of Carbon Fiber Carbon Fiber Number of Each Filament 12, Unit Weight Diameter.82 g/m 7 μ Specific Gravity 1.8 Strength 352 kg/mm 2 Elastic Modulus 23, kg/mm 2 Table 2: Physical Property of Glass Fiber ZrO 2 14.5 % Elongation Ratio of Strain At Break Point 3. % Young s Modulus Specific Gravity 2.78 6958 MPa Absorption <.2 % Melting Point 8 C Diameter 16 μm Lose Weight Ratio in the liquid of NaOH for 1 after 1 hour < 5 % Residual Strength in the liquid of NaOH for 1 after 4 hour >82 % 335
2.2 Experiment variables and mixture proportion Test variables as shown in Tables 3 and 4 include the content of carbon fiber (1. %), glass fiber (.5 %, 1. %, 1.5 %) and steel fiber (.5 %, 1. %, 1.5 %). The water-binders ratio is.28. Table 5 gives the mixture proportions of concrete sample, in which the proportion of binder materials, Cement: Blast Furnace Slag: Silica Fume (C: SL: SF), is 7: 1: 2. Table 3: Test plan W/B Concrete types Test item Test age (day) Carbon fiber concrete Flow abrasion tes t.28 Glass fiber concrete Abrasion underwater test (ASTM C1138) 28, 56 Steel fiber concrete Cracking impact test (ACI committee 544) Table 4: Test variables a) W/B.28 Mix number Water Cement C:SL:SF Fiber SP Sand ratio Aggregate kg/m 3 % CF1 14 35 7:1:2 1. 1.5 4 39 GF5 14 35 7:1:2.5 1.5 4 39 GF1 14 35 7:1:2 1. 1.5 4 39 CF15 14 35 7:1:2 1.5 1.5 4 39 SF5 14 35 7:1:2.5 1.5 4 39 SF1 14 35 7:1:2 1. 1.5 4 39 SF15 14 35 7:1:2 1.5 1.5 4 39 a): CF = Carbon Fiber; GF = Glass Fiber; SF = Steel Fiber; SL = Blast Furnace Slag; SF = Silica Fume; SP = Superplasticizer Table 5: Mixture proportion of fiber concrete (kg/m 3 ) Mix number W/B Water Cement BFS SF Fiber Sand FA CA SP Air CF1.28 14 35 5 1 18 711 516 518 7.5 1% GF5.28 14 35 5 1 14 717 52 522 6. 1% GF1.28 14 35 5 1 28 711 516 518 7.5 1% GF15.28 14 35 5 1 42 76 511 513 8.5 1% SF5.28 14 35 5 1 39 718 52 522 5. 1% SF1.28 14 35 5 1 78 712 516 518 6.5 1% SF15.28 14 35 5 1 117 76 512 514 7.5 1% 336
3 mm 44 mm 115 mm 46 mm 2.3 Experimental program and apparatus 1. Flow abrasion test: The apparatus as shown in Figure 1 is designed specially to evaluate the abrasion erosion resistance of concrete surface subjected to impact of waterborne sand. There are four motors, a motor revolves a blade, fixed in four corners of the apparatus. Using a water pump to circulate the waterborne sand, then the blades mixes well the waterborne sand, and the speed of the flow is kept at 12m/s. A designed fabricated 1 x 2 mm rectangular nozzle is large enough to cover the maximum size of waterborne sand. The dimension of fiber concrete specimens is 2 x 2 x 5 mm and the total test period is two hours. The relative abrasion erosion resistance is evaluated by weight loss of concrete specimen. 2. Abrasion resistance test of concrete underwater method: The test apparatus as shown in Figure 2 is formulated according to ASTM C1138. A steel pipe with a chuck capable of holding and rotating the agitation paddle with steel balls under test conditions at a speed of 12 ± 1 rpm is used. The apparatus was used to measure the abrasion resistance underwater of concrete specimens. The dimension of specimen is Φ3 x 1 mm and the test specimens are weighed at 12 hours intervals during the 48 hours test period. The abrasion erosion resistance is also evaluated by weight loss of concrete specimens. 3. Crack impact test: Figure 3 shows the conformation of the apparatus. It is designed according to ACI committee 544. A disc specimen rests on the base plate within four positioning lugs. By testing, a hammer consecutively falls from a height onto a steel ball standing at the center of the disc, subjecting the disc to repeated impact blows. The specimen size is Φ15 x 63.5 mm in dimension and the test time ends until the destroyed stage (finial-cracking) of specimens appears. Shotcrete Nozzle Mixing Pump Agitation Paddle 3 mm Specimen Direction of Water Flow 13mm Steel Tank Steel Grinding Balls Screw W/Wing Nut 2 mm 4 mm 1 mm Concrete Specimen 6 mm Mixture Water Pump 1295 mm Water Drainage Valve Specimen Seating Blocks Figure 1: Schematic of flow abrasion test apparatus Figure 2: Schematic of abrasion underwater apparatus 337
457 mm Hammer (4.5kg) Concrete Specimen (64mm thick) Steel Ball (63.5mm diameter) Figure 3: Schematic of cracking impact apparatus 3. Results and discussion 3.1 Abrasion Erosion Resistance of Fiber Concrete 3.1.1 Results obtained from flow abrasion test Table 6 summarizes the test results of fiber concrete subjected to flow abrasion erosion test with water containing 23 kg/m 3 sand. Figures 4 and 5 show the relationship between abrasion erosion resistance of the glass and steel fiber concretes. It may be found that the fiber concrete containing various fiber amount of.5 % to 1.5 %, at age of 28 days and 56 days, exhibit almost the similar abrasion loss of mass. This implies that the fiber contents have insignificant effects on the abrasion erosion resistance of fiber concrete. Figure 6 shows the abrasion volume after 48 hours abrasion test of three fiber concretes with 1. % fiber content. It may be seen that the abrasion volume of the three fiber concretes with carbon fiber, glass fiber and steel fiber at 28 days age are 19.9 cm 3 /hr, 21.2 cm 3 /hr and 18.4 cm 3 /hr, respectively, and at 56 days age are 14. cm 3 /hr, 12.5 cm 3 /hr and 7.5 cm 3 /hr, respectively. It reveals that when the age of fiber concretes increase from 28 days to 56 days, the abrasion volume decrements of the three fiber concretes reduce approximately 3 %, 42 % and 6 %, respectively. Consequently, the steel fiber concrete exhibits better abrasion erosion resistance in relation to the other fiber concretes. 338
48h Total Abrasion Volume (cm 3 ) Abrasion loss of mass (cm 3 /h) Abrasion loss of mass (cm 3 /h) Table 6: Abrasion loss of mass of fiber concrete from flow abrasion test (cm 3 /h) Mix number 28 day 56 day CF1 19.9 14. GF5 21.6 12.4 GF1 21.2 12.5 GF15 21.1 11.8 SF5 18.2 7.6 SF1 18.4 7.5 SF15 16.9 7.2 25 25 2 2 15 15 1 1 5 Glass Fiber 28 day 56 day.4.8 1.2 1.6 Content (%) Figure 4: Relationships between abrasion loss of mass and glass fiber content 25 2 5 Steel Fiber 28 day 56 day.4.8 1.2 1.6 Content (%) Figure 5: Relationships between abrasion loss of mass and steel fiber content 28 day 56 day 15 1 5 CF1 GF1 SF1 Figure 6: Abrasion volume of fiber concrete from flow abrasion test 339
3.1.2 Results obtained from underwater abrasion test (ASTM C1138) Table 7 and 8 summarize the average accumulating abrasion volume of fiber concrete at various test times for the concrete age of 28 and 56 days. Figures 7 to 1 plot the average abrasion volume of glass and steel fiber concretes against the time. It may be found that the abrasion volumes increase by the increase of test time, the increment of abrasion volume for both of glass and steel fiber concretes appear a linear increasing. It means that the abrasion volume of glass and steel fiber concretes is similar at every 12 hours test interval. Hence, both the fiber concretes demonstrate a stable abrasion resistance when the abrasion energy keeps constant. Figures 11 and 12 present the abrasion volume of the three fiber concretes in relation to the test times. It could be seen that the carbon and glass fiber concretes exhibit quite similar abrasion erosion resistance, while the steel fiber concrete shows the best abrasion erosion resistance, its average abrasion volume is 2 % lower than that of the other two fiber concretes. It is due to the reason that, by underwater abrasion test, the greater steel fiber could be perform as hardened aggregate in concrete, resulting in advantageous to the abrasion resistance. Table 7: Abrasion volume of fiber concrete from underwater abrasion test (28 day) Average of accumulating abrasion volume (cm 3 ) Mix number Test time (h) 12 24 36 48 CF1 8.3 18.8 28.6 39.4 GF5 8.9 19.8 29.7 41. GF1 7.6 17.3 26.3 37.1 GF15 11.2 22.3 32.1 43.2 SF5 7.3 14.1 22.7 3.9 SF1 6.6 13.2 21.6 3.6 SF15 5.9 12.3 2.7 29.7 Table 8: Abrasion volume of fiber concrete from underwater abrasion test (56 day) Average of accumulating abrasion volume (cm 3 ) Test time (h) Mix number 12 24 36 48 CF1 8.3 16.6 25.6 34.8 GF5 8.2 17.3 27.8 39.1 GF1 8.7 17.2 25.3 34.5 GF15 9.5 17.7 26.8 35.8 SF5 6.2 13 2.7 28.2 SF1 6.2 12.6 19.7 26.8 SF15 5.2 11.7 18.6 25.2 34
48h Abrasion Erosion Volume (cm 3 ) 48h Abrasion Erosion Volume (cm 3 ) 48h Abrasion Erosion Volume (cm 3 ) 48h Abrasion Erosion Volume (cm 3 ) 48h Abrasion Erosion Volume (cm 3 ) 48h Abrasion Erosion Volume (cm 3 ) 5 5 4 3 Glass Fiber.5% 1.% 1.5% 4 3 Steel Fiber.5% 1.% 1.5% 2 2 1 1 1 2 3 4 5 Age (hour) Figure 7: Abrasion volume of glass fiber concrete vs. test time (28 day) 5 1 2 3 4 5 Age (hour) Figure 8: Abrasion volume of steel fiber concrete vs. test time (28 day) 5 4 3 Glass Fiber.5% 1.% 1.5% 4 3 Steel Fiber.5% 1.% 1.5% 2 2 1 1 1 2 3 4 5 Age (hour) Figure 9: Abrasion volume of glass fiber concrete vs. test time (56 day) 5 1 2 3 4 5 Age (hour) Figure 1: Abrasion volume of steel fiber concrete vs. test time (56 day) 5 4 3 Fiber Content = 1.% Carbon Fiber Glass Fiber Steel Fiber 4 3 Fiber Content = 1.% Carbon Fiber Glass Fiber Steel Fiber 2 2 1 1 1 2 3 4 5 Age (hour) Figure 11: Abrasion volume of fiber concretes vs. test time (28 day) 1 2 3 4 5 Age (hour) Figure 12: Abrasion volume of fiber concretes vs. test time (56 day) 341
3.2 Impact Resistance of Fiber Concrete Table 9 summarizes the results of impact resistance test of fiber contcrete. It may be found that the impact numbers at final cracking failure of glass fiber concrete is in the range of 213 to 48, in which the fiber concrete with 1. % glass fiber resist the most number of blows of 48, subsequent by 1.5 % fiber of 36 and.5 % fiber of 213 is the least. The result shows that the concrete containing 1. % glass fiber presents the best impact resistance and the addition of glass fiber has evident effect on the impact resistance of concrete. In addition, it is also found that the concrete containing 1. % steel fiber resists the most number of blows of 271 and the concrete containing 1.5 % steel fiber exhibits the least number of blows of 246. Table 9: Impact resistance of fiber concrete (56 days) Mix number Crack Number of Blows Mix number Crack Number of Blows CF1 GF5 GF1 GF15 Initial 382 Initial 18 SF5 Final 382 Final 261 Initial 213 Initial 64 SF1 Final 213 Final 271 Initial 48 Initial 1 SF15 Final 48 Final 246 Initial 36 Final 36 Figure 13 illustrates the comparison of the impact resistance of three fiber concretes containing same fiber amount of 1. %. From the figure it is found that the blow numbers at final-cracking of glass, carbon and steel fiber concretes are 48, 382 and 271, respectively. It reveals that the glass fiber concrete has the best impact resistance, subsequent by the carbon fiber concrete, and the steel fiber concrete is the worst. In addition, it is also found that the carbon and glass fiber concretes have equivalent blow numbers at initial-cracking and finial-cracking, while the steel fiber concrete exhibits a difference of 21 blows. This result may be explained as that the three kinds of fibers appear different reinforcing effects in concrete due to different conformations themselves. When an impact load acts on the concrete, cracks may be occurred inside the specimen. But the fibers could prevent immediately the cracks from developing further and the damage time of concrete could be also delayed because of the effect of tensile force of fibers. Compare to the steel fiber, the carbon and glass fibers are much smaller in size, more numbers of fibers will be distributed in concrete. This could prevent effectively the microcracks from further developing. However, it also means that if the microcracks break through the restrained forces of fibers, the microcracks will develop quickly and lead to visible crack, such that the concrete is fractured. The diameter of steel fiber is 16 to 35 times larger than those of carbon and glass fibers, every steel fiber may confine greater volume of concrete. This provides a bigger space for the visible crack to develop before the concrete fails (finial-cracking). Consequently, the steel fiber concrete may not be 342
Number of Blows fractured by the occurrence of visible cracks but will be failed until the steel fiber is broken or pulled out. 5 4 Initial Cracking Final Cracking 3 2 1 CF1 GF1 SF1 Figure 13: Comparison of impact resistance of fiber concrete 4. Conclusion Based on the test results, the following conclusions can be drawn: 1. When the fiber content keeps 1. %, the steel fiber concrete exhibits better abrasion erosion resistance in flow abrasion test than that of the carbon and glass fiber concretes. 2. It was found from the underwater abrasion test that the carbon and glass fiber concretes present quite similar abrasion erosion resistance, while the steel fiber concrete exhibits the best abrasion resistance, its average abrasion volume is 2 % lower than that of the other two fiber concretes. 3. When the fiber content keeps at 1. %, the glass fiber concrete has the best impact resistance, subsequent by the carbon fiber concrete, and the steel fiber concrete is the worst. References Yen T., Liu Y. W. (2) etc., Research on the Resistant Properties of High Strength Concrete, Taiwan Power Company Report. (in Chinese) Hsu T. H. (26), Influence of Fly Ash on the Abrasion-Erosion Resistance and Cracking Controlled of High-Strength Concrete, a doctoral dissertation. (in Chinese) 343
Webster, C.T.L. and Havelock, F. (1987), Alternative coatings for the protection of hydraulic turbines from cavitation erosion, British Columbia Hydro and Power Authority report 136G274. ACI 21R-93 Erosion of Concrete in Hydraulic Structures. Papenfus N. (23), Applying Concrete Technology to Abrasion Resistance, Proceedings of the 7th International Conference on Concrete Block Paving (PAVE AFRICA 23). Liu T. C. (1981), Abrasion Resistance of Concrete, ACI Journal, 78(5), 341-35. Laplante P., Aitcin P. C., and Vexina D. (1991), Abrasion Resistance of Concrete, Journal of Material in Civil Engineering, Vol.3, No.1. Liu Y. W., Yen T., Hsu T.H. (26), Abrasion Erosion of Concrete by Waterborne Sand, Cement and Concrete Research vol.36, 1814-182. Bayasi Z. and Zeng J. (1993), Properties of Polypropylene Fibre Reinforced Concrete, ACI Material Journal, 9, No.6, 65-61. 344