In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fib...
In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fiber, PP and PVA, and these were mixed in at 0.1, 0.5 and 1.0 vol.%, respectively. Impact resistance is evaluated with an apparatus for testing impact resistance performance by high-speed projectile crash by gas-pressure. For the experimental conditions, Specimen size was $100{\times}100{\times}20$, 30mm ($width{\times}height{\times}thickness$). Projectile diameter was 7 and 10 mm and impact speed is 350m/s. After impact test, destruction grade, penetration depth, spalling thickness and crater area were evaluated. Through this evaluation, it was found that as compressive strength is increased, penetration is suppressed. In addition, as the mixing ratio of fiber is increased, the spalling thickness and crater area are suppressed. Organic fibers have lower density than the steel fiber, and population number per unit area is bigger. As a result, the improvement of impact resistance is more significant thanks to dispersion and degraded attachment performance.
In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fiber, PP and PVA, and these were mixed in at 0.1, 0.5 and 1.0 vol.%, respectively. Impact resistance is evaluated with an apparatus for testing impact resistance performance by high-speed projectile crash by gas-pressure. For the experimental conditions, Specimen size was $100{\times}100{\times}20$, 30mm ($width{\times}height{\times}thickness$). Projectile diameter was 7 and 10 mm and impact speed is 350m/s. After impact test, destruction grade, penetration depth, spalling thickness and crater area were evaluated. Through this evaluation, it was found that as compressive strength is increased, penetration is suppressed. In addition, as the mixing ratio of fiber is increased, the spalling thickness and crater area are suppressed. Organic fibers have lower density than the steel fiber, and population number per unit area is bigger. As a result, the improvement of impact resistance is more significant thanks to dispersion and degraded attachment performance.
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가설 설정
1) In terms of penetration depth, the higher the compressive pressure, the deeper the depth, but the influence of the fiber mix was not significant.
제안 방법
Hence, this study aims to review the effect of the compressive strength of and fiber mix proportion in mortar and concrete on impact resistance performance under a high-speed crash condition, using an apparatus for testing impact resistance performance by high-speed projectile crash. In addition, considering the thickness of concrete and the crash energy of the high-speed projectile, data on the evaluation of impact resistance performance is collected to be utilized in the future as fundamental data for impact resistance performance design of fiber reinforced cement composite.
Three plain specimens were made at W/B 57, 38 and 29%, respectively, to evaluate the impact of compressive strength on penetration depth. In addition, to evaluate the influence of fiber mix on spalling thickness and crater area, the concrete specimens were made at W/B 57% by adding steel fiber, PP and PVA to be 0.1, 0.5 and 1.0 vol%, respectively. Mortar specimens were made under the same condition as the fiber-reinforced concrete specimens, and specimens were also made by adding the same proportion of steel fiber+PP and steel fiber+PVA, respectively, as the single mix condition.
The compressive strength was evaluated as the mechanical property, and the impact resistance performance was evaluated by inspecting the surface of the specimens including destruction grade, penetration depth, spalling thickness and crater area.
Table 1 shows the experiment plan for this study. Three plain specimens were made at W/B 57, 38 and 29%, respectively, to evaluate the impact of compressive strength on penetration depth. In addition, to evaluate the influence of fiber mix on spalling thickness and crater area, the concrete specimens were made at W/B 57% by adding steel fiber, PP and PVA to be 0.
대상 데이터
As shown in Table 2, the materials used in this study are Portland cement manufactured by S company (density of 3.15g/cm3), and fly ash (density of 2.30g/cm3) used as an admixture. Sea sand was used as fine aggregate and broken gravel (maximum size of 20mm) was used as coarse aggregate.
Mortar specimens were made under the same condition as the fiber-reinforced concrete specimens, and specimens were also made by adding the same proportion of steel fiber+PP and steel fiber+PVA, respectively, as the single mix condition. The projectile crash test was performed under the test condition of specimen 30 mm thickness, projectile 10 mm diameter, and crash speed 350m/s. Another test was conducted under the condition of specimen 20 mm thickness, projectile 7 mm diameter and crash speed 350 m/s, in consideration of the effect of aggregate.
이론/모형
The compressive strength was measured using a UTM after grinding the specimen at a certain age in compliance with the Test Method of Concrete Compressive Strength stipulated in KS F 2405.
성능/효과
2) Fiber mix improved toughness, and spalling thickness and crater area caused by the high velocity projectile were decreased.
3) It is believed that under a mix proportion, the population number of organic fibers per unit area was more than that of steel fibers due to its low density, improving the attachment performance and decreasing the spalling thickness and the crater area by high velocity crash.
참고문헌 (9)
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Jeon YS, Kim GY, Nam JS, Kim HS, Miyauchi H. A study of the destruction condition of high strength concrete impacted by high speed projectile. Journal of the Korea institute for structural maintenance inspection. 2011 May;15(1):253-6.
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Masuhiro BEPPU, Koji MIWA, Tomonori OHNO, Masanori SHIOMI. An experimental study on the local damage of concrete plate due to high velocity impact of steel projectile. Journal of Japan society of civil engineers. 2007 March;63(1):178-91.
Nam JS, Kim GY, Jeon JG, Jeon YS, Kim HS, Hwang HK, Miyauchi H, Kim MH. Impact resistance performance of mortar by mixing condition of fiber. Summaries of Technical Papers of Annual Meeting; 2010 September 09-11; University of Toyama. Toyama (Japan); Architecture Institute of Japan; 2010. p. 539-40.
Kim GY, Nam JS, Miyauchi H. Evaluation on impact resistance performance of fiber reinforced mortar under high-velocity impact of projectile. Journal of the Architecture Institute of Korea. 2011 September;27(9):101-8.
Jeon YS, Kim GY, Nam JS, Kim HS, Lee TG, Kim MH. Evaluation on blast resistance performance of concrete using fiber reinforced mortar panel and air space. Proceedings of the Korea Institute of Building Construction; 2010 Nov 12; Chungnam National Unversity. Seoul (Korea); the Korea Institute of Building Construction; 2010. p. 31-4.
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