27(5A)-13(5735).fm

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1 27ƒ 5A Á œ pp. 735 ~ 743 gj p ª w š p w { ³ p Flexural Behavior and Cracking Characteristics of High Performance Fiber Reinforced Cementitious Composites according to Fine Aggregate Contents *Á ³x** Shin, Kyung-JoonÁJang, Kyu-Hyoun Abstract Various methods have been used to reinforce the cementitious material such as mortar and concrete that have weak tensile strength. Major reinforcing method is to mix matrix with fibers which have strong tensile strength. Recently, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) has been developed which shows multiple cracking behavior, that is different from conventional FRC. Related studies mainly have focusing on the mechanical behaviors according to fiber types and mixture proportions such as W/C and binder contents. However, study related to fine aggregate type and contents are insufficient. Therefore, this paper examines the fracture characteristics related to fine aggregate and contents, and reports the cracking behavior as well as mechanical behavior for various mixtures which have different fiber type and mixture proportions. From the results, it was useful to use silica sand as a fine aggregate for reducing fracture toughness as maintaining compressive strength and elastic modulus. It is showed that optimal silica-cement ratio was 0.8~1.0 to maximize flexural toughness and number of crack. Keywords : HPFRCC, fiber reinforced mortar, cracking characteristic, flexural behavior w ƒ š p yw k gj p w» w w š, w wƒ w gj p y w gj pƒ ã. w w w w ³ g ƒƒ ³ s y j w x ƒ j š p w (HPFRCC) w ƒ y w š. w wp - p w w w, w p w w., š HPFRCC w» w p ww š, w k HPFRCC ³ p w ww. x, ³ w k w q û w, { ƒ z ³ w w (³ )- p ƒ 0.8~1.0 ù kû. w : š p w, k, ³ p, { 1. p w k gj p», ƒ û» ³ w» p. w gj p ³ ü w ƒ w wƒ» ³ w» w w š. w w gj p y w gj p(frc, Fiber Reinforced Concrete)ƒ ã (Balaguru et al. 1992; Bentur et al. 1990). w gj p(frc) ³ z w j z ù, ³ w» w». wr, FRC w w» w š p w ( w z w y œw z ( kj12@snu.ac.kr) ( ) ( addio0024@hanmail.net) 27ƒ 5A œ 735

2 t 1. e p Fiber ID Diameter Length Tensile Strength Elastic Modulus Remark PVA mm 12 mm 1.6 GPa 40 GPa Resin-bundled type PVA mm 12 mm 1.1 Gpa 25 GPa Resin-bundled type msteel 0.20 mm 12 mm 2.0 Gpa 200 GPa Straight, Brass Coating HPFRCC, High Performance Fiber Reinforced Cementitious Composites) w ƒ y w š (Fischer et al. 2006; Naaman et al. 1995, 2003). HPFRCC š ( 2005) š (½ 2005) w, š t w (Fischer et al. 2006)ƒ ww š. š HPFRCC gj p w w» FRC w w ³ g ƒƒ ³ s y j w x ƒ g, y j ³ (Smeard multiple cracking) ƒ š (Li et al. 1995). w š HPFRCC w ³ w š q û» w w ³ wš j yww p ƒ š (½ w 2005; ½ 2005; 2004). j k, p HPFRCC p p q p w r ³» z w w w w ƒ v. ù, w p y w (½ w 2005) - p ù w w (½ 2005; Song et al. 2004) w ù, p w, w (Guerrero 1999; Wu 2001) š š. Li (Li et al. 1995) ³ w p p w tw ù, y w yw w. w š HPFRCC w» w w p w ww š, w k y HPFRCC { ³ p w ww. ¼ 12 mm 0.2 mm w, sww gj p j p j t»w. 2. x 2.1 x z w š p w w ³ ƒ (Crack Bridging) w»³ q š, w ƒw ³ w, w ƒw ³ w j x ý. w ³ k p (Matrix) q p w, k p q w w x ww. q yw w ³ w w k p q w ù(li et al. 1995) yw w., š HPFRCC w w p w w ³ w x w w p q w x ww. p w p w. x p w x m w HPFRCC w w wš, - p (S/C) x w HPFRCC w p ³ p w x ww. w A 1 m sp p s e š ƒ, 2 PVA 1 ƒ. 0.2 mm ¼ 12 mm š ƒ, PVA ¼ 12 mm š 0.04 mm 0.1 mm ƒ. ƒ p t 1 ùkü. gj p w (F.M.) 2.5 s³ 0.43 mm š 2.65 ( w ) (F.M.) 0.3 š s³ mm 2.65 ³ ( w ³ )ƒ ƒ s 1 ùkü. 2.2 p w p x q (Matrix fracture toughness) w x 1. s x 736

3 x p x HPFRCC { x W/C t 2. e x S/C C (kg/m 3 ) W (kg/m 3 ) S (kg/m 3 ) sp (kg/m 3 ) a f ---- W a a W W a 2 W a W a 3 a W W = », a= e ¼, P Q = d w, B= r s, W= r ¾ (2) 2. CT(Compact Tension)xk q x r x w w k p (Matrix) q p sƒw» w k p q w w w q x ww. - p (W/C) 0.46 w - p (S/C) 0.5, 1.0, 1.5 y g ³ w r w t 2 x w ùkü. r 2 ASTM E 399 ³ šw CT(Compact Tension) x w xk w x ww. LEFM(Linear Elastic Fracture Mechanics; xk q w) w d q zw» w q w (fracture process zone) j»ƒ r j» w w, gj p FRC x ³ r LEFM w w, w size effect w r j» d q w š (Bazant and Planas 1998). ù, 1 mm w w k pt LEFM zw (Li et al. 1995)š š, x q q š., sww š ³ w x LEFM w q zw. Closed Loop System ƒ ƒ w MTS 810»» w x ww. w w 0.1 mm/min w, w q (K Q ) w (Sanford 2003). P K Q a Q = f ---- BW 1 2 W (1) k w x k d w» w 100 mm š 200 mm mx œ w, KS F 2405 KS F 2438 w w w. 2.3 HPFRCC { w x q w x mw HPFRCC w w q y k w w, w j p w { r w x ww. x w Ì 25 mm, s 60 mm, ¼ 250 mm r w. - p (W/C) 0.46 y 2% w š w, p p x w mw - p (S/C) 0.4~1.0 y g r w t 2 x wt ùkü. r kxz w 28 ù z x ww. r ̃» JCI-SF4(1983) wš r ü d» w»ƒ» 3 r d» š» w w 3. 4 w w k { x 27ƒ 5A œ 737

4 d w. ³ w ³ j» w { 4 w w { x w. x Closed Loop System ƒ ƒ w MTS 810»» w, w w mm/sec w. 3. x 3.1 p p w x x 4 t 3 w ùkü. ³ w ƒ ƒw w ù, w S/Cƒ 1.5 w. S/Cƒ 0.5 w r ƒ ³ w r 15%j ùkû ù, S/Cƒ ³ w r ƒ 5% 20% j ùkû. Guerrero(1999) W/C 0.5 š S/C 1.0 w ³ (silica sand) w ƒ w 8~47% j š ew w š k x 5 t 3 w k ùkü. k (S/C)ƒ ƒw f, S/Cƒ 0.5 k ƒ j ùkû ù S/Cƒ 1.0 ƒ w. 5. w k 6. w q q x S/C q (fracture toughness) x w 6 t 3 ùkü. ³ w S/C q (K) 0.167~0.284 MPaÁm 1/2, w 0.428~0.724 MPaÁm 1/2. x S/C ƒ q f ùkû, w r ³ w r 2.55~3.45 q y w. w, w r ƒ û q ³ w r ƒ q ùkû x 4. w w p y w» w t 3. w p w p S/C ratio Elastic modulus(gpa) Compressive strength(mpa) Fracture toughness(mpam 1/2 ) SilicaSand PlainSand E plain /E silica SilicaSand PlainSand f ck,plain /f ck,silica SilicaSand PlainSand K Plain /K Silica

5 f w. w š HPFRCC ³ w t wš, ³ w» w w ƒ q û w. p q 0.3 MPaÁm 1/2 w û» w ³ kwš y w w. ³ - p 7. ³ w» w w e ³ w w e w w e y w 7 ùkü. x ³ w w w 40% w q ù, w k ù 74%., q yƒ ù k y j ùkû, ³ w k w q j k ùkû. š p w ³ p ƒ j k»³ z ³ s ƒw ³ ƒ w» e ³ w x p, w ùkù» w w. w ƒ»³»³ z w w ƒ x ww w.,»³ ûš ƒ w. w,»³ z w» e ³ w w w p q w, ƒ w»¾ ƒ ƒ w ³ s, ƒ w w ³ ³ w w j ƒ w. j w w (½ 2005; Li et al. 1995) ³ ƒ j š, ù k ³ j» w w w ³ ³ (Complementary energy, J b )ƒ p ³ q (J tip ) f w š š. ƒ j» w y ƒ j y w ñ ü» w w š, j» w p q û w, j» w ƒ ³ s 8. yw { x w s³ w - š 27ƒ 5A œ 739

6 (S/C)ƒ 1.5 w w, š y ƒ v w», S/ C=0.4~1.0 w { x w S/C HPFRCC { ³ p w. š w p w š w w, k w ww w. 3.2 HPFRCC { w x { p p w x w ³ w - p (S/C) 0.4, 0.6, 0.8, 1.0 w PVA04, PVA10, msteel 3 y w { x ww š, 8 ùkü. x 3 r xw s³ t»w. PVA04, PVA10 r ³» x ³ y w ùkû, ³ z»³ z { ƒw - y(displacement hardening effect) x. ù ³ z ƒ PVA04 ƒ j ùkû. msteel r PVA r w 1.2~2.7 { k ƒ PVA w j». w ³ s ƒw ƒ q x w» z w w w w. p w ³ w» p ƒ y ( k ) k, r ³ k w. ù, ³ w z ³ w w ƒ w p š ƒ ³ z w, w w w w w ³ ƒ (crack bridging relation) ùkü (Lin et al. 1999). yw w š ƒ w, w ƒ ƒ j w» w ¼ x k, ƒ w w» w j» w w. ƒ w z (Snubbing effect) w ƒ w w w ƒ w j» q. ³ ƒ 9(a) ùkü. q» ƒw ³ ww j» f. 8 x r ƒ ƒw ƒ ƒw w ùkü.»³ z ƒ w. msteel r p ƒ ƒwš, ³ ƒ (Crack Bridging-Stress) ƒw, q w» r { ƒ f. 9(b) PVA w r ³ ƒ ù kü. PVA ƒ ƒw ƒ ƒ.» (Redon et al. 2001) PVA ƒ û š yw j ƒw x - y(slip-hardening)x» q» p. ƒ ƒw ƒ f, q» ƒ ƒ w ùk P = σa = τs (3)», τ σ w š, L d ¼, A S t πd 2 /4 πd L/2 tx.» (Li and Stang 1997) w 2.35~7.0MPa x ƒ w w» w τ=(σd)/ (2L)=15.38 MPa 1/2., w w, 9. PVA w ³ ƒ (Crack bridging relation) š 740

7 ù. 8 PVA w r ƒ ƒw ƒ ƒw, ƒ { y w j ùkû. 9(a) ³ ƒ y w ƒ ƒw ƒ f, q» { w w ùkù.» (Li et al. 1997) w w p (S/ C,,, s ) p ùkù š wš, x (Balaguru et al. 1992) ùkû. Guerrero(1999) x w j w ƒ w w 80% ƒw š šwš. w p š j» ³ w w w (interlocking) ƒw j»ƒ ƒw ù, y w x ƒ w, mw w v w.» k ƒ j» r ƒ w q, PVA ƒz x- y(slip-hardening)x ³ ƒ ƒw w ww p. msteel r 2mm w w š PVA w r 3~4 mm w w. PVA w r ³ ƒ r w», PVA w w x w w ww ƒ k q { { (Flexural toughness) gj p p ùkü t w - š ùkü. w» x ³ (JCI-SF4; ASTM C 1018) š ù, JCI-SF4 w { 1/150 w w ¾ { w š, ƒ { t 4. yw { { Fiber Type PVA04 PVA10 msteel S/C Flexural Strength (kn) Flexural Toughness(kN-mm) 1.33 mm (L/150) 2.67 mm (2L/150) Post-Peak yw { 27ƒ 5A œ 741

8 11. s³ ³ d t 5. yw { s³ ³ S/C Fiber Type 2/150 w w {»³ z Post- Peak { w w, t 4 10 ùkü. PVA w PVA04 r PVA10 r 8 w - š y w 2L/150 ¾ w, 2L/150 j w z w. L/150 2L/150 { x ƒƒ w ùkü y w., msteel r w { yƒ yw ùkù, ƒ ƒw L/150 2L/150 { ƒw y w ³ p j y w p w w w ³ w p» w, w š HPFRCC w. p w ³ z w» w, w wƒ óù r w ³ d w. ³ ³ w sw, 11 d» wš,» m w ³ s³ w. PVA04 r 5 ³ w, PVA10 r S/Cƒ 0.4 w s³ 5 { ³ ùkû. msteel r S/ Cƒ 0.4 ³ w, S/Cƒ ƒw ³ ƒ ƒw ùkû. 4. PVA04 PVA10 msteel š p w { ³ p š w w x ww, w. 1. HPFRCC w» p w x ww. ³ w w x mw p w p w. x k q j w, ³ w k w q û. p q û w š HPFRCC w ³ w w ù kû. 2. w š HPFRCC { x ww. PVA w ³ ƒ w ³ - p ƒ 0.8~1.0 ùk û. PVA w { r r w ³ z ƒz ³ - y x w ƒ ƒw w ww ùkû. 3. w r { x ³ y w { { ƒw š, PVA w r 2.7 {. k ƒ ³ ƒ (Crack Bridging Stress) w». 4. k ³ z p w. PVA x- yx (sliphardening) p w (Pull-out) q p, ƒ { ƒ w ù, p ƒ ƒ w w» { ƒ j. š x ½ w, ½ y, ½, ½ (2005) j j w š p w w p w x, w gj pwz, w gj pwz, 17«, 2y, pp ½, ½, ½, w», ½ (2005) j w w ECC(Enginerred Comentitious Composite) w p, w gj pwz, w gj pwz, 17«, 5y, pp , š k, k, ½ (2005) š p w ƒ e w, w gj pwz, w gj pwz, 17«, 1y, pp , x, z(2005) š w g j p { p, w gj pwz, w g j pwz, 17«, 4y, pp ASTM C 1018 (1998) Standard Test Method for Flexural Toughness and First Crack Strength of Fiber Reinforced Concrete, American Society of Testing and Materials, Philadelphia. Balaguru, P. and Surendra, P. (1992) Fiber-reinforced cement composites, Elsevier. Bazant, Z.P. and Planas J.S. (1998) Fracture and Size Effect in Concrete and Other Quasibrittle Materials, CRC Press. Bentur, A. and Mindess, S. (1990) Fiber reinforced cementitious composites, McGraw-Hill. 742

9 Fischer, G. and Li, V.C. (2006) International RILEM Workshop on High Performance Fiber Reinforced Cementitoius Composites(HPFRCC) in Structural Applications, E&Fn Spon. Guerrero, A.P. (1999) Bond Stress-Slip Mechanisms in High Performance Fiber Reinforced Cement Composites, PhD Thesis, The University of Michigan. JCI SF4, Method of Test for Flexural Strength and Flexural Toughness of Fiber Reinforced Concrete, Japan Concrete Institute. Kim, Y.Y., Kong, H.J., and Li, V.C. (2003) Design of engineered cementitious composite(ecc) Suitable for Wet-mix Shotcreting, ACI Materials Journal, Vol. 100, No. 6, pp Li, V.C. and H. Stang (1997) Interface property characterization and strengthening mechanisms in fiber reinforced cement based composites, J. Advanced Cement Based Materials, Vol. 6, No. 1, pp Li, V.C., Mishra, D.K., and Wu, H.C. (1995) Matrix design for pseudo strain-hardening fibre reinforced cementitious composites, Materials and Structures, 28, pp Lin, Z., Kanda, T., and Li, V.C. (1999) On interface property characterization and performance of fiber reinforced cementitious composites, J. Concrete Science and Engineering, RILEM, Vol. 1, pp Naaman, A.E. and Reinhardt, H.W (1995) High Performance Fiber Reinforced Cement Composites 2 (HPFRCC2), E&Fn Spon. Naaman, A.E. and Reinhardt, H.W (2003) High Performance Fiber Reinforced Cement Composites 4 (HPFRCC4), E&Fn Spon. Oh, B.H. and Shin, K.J. (2005) Cracking, Ductility and Durability Characteristics of HPFRCC with Various Mixture Proportions and Fibers, Proceedings of Int'l workshop on HPFRCC in structural applications, pp Redon, C., Li, V.C., Wu, C., Hoshiro, H., Saito, T., and Ogawa, A. (2001) Measuring and modifying interface properties of PVA Fibers in ECC Matrix, ASCE J. Materials in Civil Engineering, Vol. 13, No. 6, Nov./Dec., pp Sanford, R.J. (2003) Principle of Fracture Mechanics, Prentice Hall. Song, Gao and Zijl, G.V. (2004) Tailoring ECC for Commercial Application, 6th RILEM Symposium on Fiber-Reinforced Concretes(FRC) - BEFIB, pp Wu, C. (2001) Micromechanical Tailoring of PVA-ECC for Structural Applications, PhD Thesis, The University of Michigan. ( : / : / : ) 27ƒ 5A œ 743