Influence of Loading Type, Specimen Size, and Fiber Content on Flexural Toughness of Fiber-Reinforced Concrete

Transcription

1 TRANSPORTATION RESEARCH RECORD Influene of Loading Type, Speimen Size, and Fiber Content on Flexural Toughness of Fiber-Reinfored Conrete V. RAMAKRISHNAN AND SATYA S. YALAMANCHI Results of an experimental investigation to determine the influene of speimen size, fiber type, and fiber. ontent on the flexural behavior of steel fiber-reinfored onrete are presented. Two fiber types and four mixes are investigated. With four series in eah mix, there are sixteen series. The effet of the two ross-setional sizes of 15 X 15 mm and 1 X 1 mm (6 in. X 6 in. and 4 in. X 4 in.) on flexural strength is also studied. Hardened onrete is tested for pulse veloity and flexure. For eah series, two speimens are tested for monotoni, and one speimen for yli, loading. Loading and unloading rates were the same for both monotoni and yli loading. In addition to the load defletion measurements, the rak mouth opening displaements versus load are reorded in the ase of nothed speimens. Load deformation behavior, post rak load drop phenomenon, and toughness for two types of fibers are evaluated and ompared. There is evidene of satter of results related to the diffiulty in ahieving a uniform distribution of randomly oriented fibers. The flexural toughness fator, reommended by the Japan Soiety of Civil Engineers is alulated. A omparison of load defletion urves under monotoni and yli loading indiates that the fibers primarily influene the envelope urve and that yli loading does not have any appreiable influene on the energy absorption harateristis. The load versus rak mouth opening displaement behavior is similar to the load defletion urve for nothed speimens. Researh (1-16) has established that the addition of fibers onsiderably improves the stati flexural strength, impat strength, diret tensile strength, fatigue strength, dutility, and flexural toughness of onrete. However, the degree of improvement in suh parameters depends on many fators, inluding size, type, and aspet ratio of fibers. Beause fiber-reinfored onrete (FRC), in many appliations, is subjeted primarily to bending instead of axial loading, performane in flexure is most important. However, lak of suffiient information on frature toughness and flexural behavior of onretes subjeted to stati and yli loadings with different types and quantities of fibers undersores the need for more researh. Suh information is essential to design engineers who use FRC in airfield and highway pavements, industrial floors, tunnel linings, and earthquake- and impat-resisting strutures. RESEARCH SIGNIFICANCE Toughness, a measure of the energy absorption apaity, is used to haraterize the FRC's ability to resist frature when subjeted to stati, dynami, and impat loads. Energy absorbed by a speimen is omputed using the area under the omplete load defletion urve. However, the load defletion urve is observed to be dependent South Dakota Shool of Mines and Tehnology, 51 E. St. Joseph Street, Rapid City S.D., 5771, upon the speimen size, the loading onfiguration, the type of ontrol, and the loading type. The load defletion urve also an be used for determining the modulus of elastiity, first rak strength, and the flexural strength of the omposite. Governing the level of these influenes are omposition parameters, suh as the type of fiber, volume ontent, and aspet ratio of fibrous reinforement. Currently available test standards for the evaluation of frature toughness indies, ASTM Cl18, Japanese Conrete Institute (JCI) SF4 (17), Japan Soiety of Civil Engineers (JSCE) SF5 (18), and Amerian Conrete Institute (ACI) 544 (J 9,2), reognize these influenes. The researh reported in this paper deals with the systemati study of the effets of ommonly used fibers on the flexural properties of omposites, the volume ontent, aspet ratio, speimen size, loading system, and test onfiguration (for nothed and unnothed speimens). EXPERIMENTAL PROGRAM Two fiber types were seleted for the study, the 5.8-mm (2-in.) long hooked-end steel and 5.8-mm (2-in.) long rimped steel fibers. Two volume perentages,.5 and 1. perent, were investigated for both types of fibers. Two speimen onfigurations were seleted, nothed and unnothed. Table 1 provides the mix designations and fresh onrete properties used for different speimens. Four speimens for eah series were made. Speimens were ast as large slabs and sawed to size (for flexure tests) to minimize the edge effet. In the ase of nothed speimens, noth depths for large and small speimens were approximately 18.7 mm (.75 in.) and 12.5 mm (.5 in.), respetively. After asting, the slabs were overed with plasti sheets for 24 hr at room temperature. Speimens were then ured in a uring room before being sawed to size and wrapped. Eah speimen was wrapped individually in a plasti sheet and was labeled. The speimens remained overed until 1 hr before testing. All mixes were designed for an approximate ompressive strength of MPa (5 psi) to MPa (6 psi). All beams were tested for pulse veloity (ASTM C597) at the age of 2 to 3 months. Beams were tested at the age of 2 to 3 months, as per ASTM Cl18, for stati flexural strength under third-point loading. For stati tests, a dial gauge with an auray of.25 mm (.1 in.) was used to measure the midspan defletion. The gauge was loated at the mid-width point of the speimen to minimize the effet of twisting on the defletion measurements. The rate of loading was maintained in the range.5 mm/min to.1 mm/min (.2 in./min to.4 in./min), as per ASTM C118. The loads were reorded for every inrement of.5-mm (.2-in.) defletion until the first rak appeared, and at different intervals thereafter. Speimens

2 4 TRANSPORTATION RESEARCH RECORD 1458 TABLE 1 Mix Designations and Fresh Conrete Properties Mix# Unnothed/ Speimen Size Fiber Type Fiber Slump Unit Air Nothed (mm) Content {mm) Weight Content lka/ml) (%) Al LU Unnothed 15x15x525 Hooked-end A2LU Unnothed 15xl5x525 Hooked-end l 7. Al SU Unnothed 1xlx35 Hooked-end A2SU Unnothed 1xlx35 Hooked-end l 7. Bl LU Unnothed 15xl5x525 Crimped B2LU Unnothed 15xl5x525 Crimped Bl SU Unnothed 1xlx35 Crimped B2SU Unnothed 1x1x35 Crimped AILN Nothed 15x15x525 Hooked-end A2LN Nothed 15xl5x525 Hooked-end Al SN Nothed 1xlx35 Hooked-end A2SN Nothed loox 1x35 Hooked-end BILN Nothed 15xl5x525 Crimped B2LN Nothed 15x15x525 Crimped Bl SN Nothed lxlx35 Crimped B2SN Nothed 1x1x35 Crimped were loaded up to a minimum midpoint defletion of 1/15 of the span, whih allowed for omputation of ACI, ASTM, and JCI and JSCE frature toughness indies. In addition to load defletion measurements, the load versus rak-mouth opening displaement readings were measured for nothed speimens (ASTM E399). Nothed and unnothed speimens were also tested under yli loading. Loading and unloading was done at 2, 3, 5.5 and 15.5 times the first rak defletion, using the same unloading/reloading rate as was used for monotoni loading. TEST RESULTS AND DISCUSSION Stati Flexural Strength Results of a omparison of the stati flexural strengths for unnothed and nothed beams are shown in Figure 1. There was a signifiant frature strength inrease as the fiber ontent inreased from.5 to 1. perent, in the ase of the hooked end fibers, and a muh lower inrease for the onrete with rimped fibers. The u a. :E 5 -E ) 4) J:J (/) 4 a... ~ 3 4) u::: 2 ( UN NOTCHED ] NOTCHED ].5% 1.%.5% 1.% Perentage of Fiber a Hooked-end (Large)~ Crimped (Large) t:<::::j Hooked-end (SmalO ~Crimped (SmalO FIGURE 1 Flexural strength versus perentage of fiber.

3 Ramakrishnan and Yalamanhi 41 perentage inreases were 74 and 38 perent, respetively, for small and large speimens for hooked fibers. There was no partiular trend observed with respet to the size of the beams for both types of fibers, beause the distribution of the fibers in the ritial tension zone of the beams varied greatly. Flexural strength was more signifiantly dependent on the atual number of fibers found in the tension blok than on the size of the ross setion. However, when fiber distribution was fairly uniform, the larger sized speimens had lower flexural strengths. Flexural Load Defletion Curves Total area under the load defletion urve is indiative of the energy absorbed by the beam. Load defletion urves were drawn using data from the stati flexure test. Load defletion urves for both types of fibers were ompared by volume, for.5 and 1. perent of fiber ontents, for both speimen sizes (21). Comparison of the stati load-defletion urves for FRC with.5 and 1. perent fiber volumes indiated that the initial elasti part of the urves did not hange appreiably. However, the post-rak plasti behavior improved signifiantly with an inrease in fiber ontent from.5 to 1. perent. Ultimate loads also inreased with an inrease in fiber ontent. An inrease in the frature energy resulted from a greater number of fibers bridging the raks in FRC with higher fiber ontent. However, the inrease in frature energy depended greatly on the type of fiber, partiularly on the bond and anhorage developed by the geometry of the fiber. Hooked-end fibers had better anhorage and bond than the rimped fibers. Hene, the ultimate loads and the total frature energy were onsiderably higher for FRC with hooked-end fibers. Post-Crak Load Drop Phenomenon Post-rak load drop is defined as the differene between maximum load and load reorded at a defletion equal to three times the defletion measured at first rak (2). Post-rak load drop was less with an inrease in fiber ontent. Typial load drops expressed as a perentage of maximum loads are 2, 1, and 18 and 15 perent for small speimens with.5 and 1. perent rimped and hooked-end fibers, :respetively. Similarly, the load drops were 15, 9, and 21 perent and 3 perent for large speimens with.5 and 1. perent hooked-end and rimped fibers. Frature Toughness and Toughness Indexes One major objetive for adding fibers to onrete is to inrease frature toughness. Various fiber effiienies an be evaluated by omparing their ability to inrease the frature toughness of onretes. Frature toughness is a measure of the energy absorption apaity to resist failure when subjeted to a flexural load. Tests for the measurement of frature toughness and toughness indies are reommended by ASTM, JCI (17), and ACI (19,2). The tests are inluded in the speifiations for FRC to ensure a minimum performane standard when used in onstrution. Toughness index, as proposed by ASTM Cl18, is a dimensionless parameter that defines or fingerprints the shape of the loaddefletion urve. Indexes have been defined on the basis of three servie loads, identified as multiples of the first-rak defletion. The index is omputed by dividing the total area under the loaddefletion urve up to the given servie level defletion, by the area under the same urve up to the first-rak defletion. Toughness index / 5 is alulated for a defetion of three times the first rak defletion. Likewise / 1 and / 3 are the indies up to 5.5 and 15.5 times the first-rak defletion, respetively. First-rak toughness is expressed as the energy absorbed by the standard beam, and it is given by the area of the load-defletion urve up to the first-rak load. Calulated toughness indexes / 5, / 1, and / 3 and first-rak toughness values are presented in Table 2. Results of a omparison of the first-rak toughness values for unnothed and nothed beams are provided in Figure 2. Results of a omparison of the toughness indexes / 5, / 1, and / 3 are presented in Figure 3 for unnothed and in Figure 4 for nothed beams. Compared with plain onrete, for whih the toughness index is one, FRC had signifiantly greater toughness, and slightly higher first-rak strength. The inrease depended on the type and quantity of fibers added. Toughness inreased with the number of fibers, both hooked-end and rimped. Hooked-end fiber-reinfored onrete had higher toughness indexes when it was ompared to on- TABLE 2 Frature Toughness (ASTM C118 and JCI SF4) Mix# Flexural First Crak ASTM Cl18 JCI Strength, Toughness, /15 13/11 SF4Fe MP a MP a MP a Al LU A2LU Al SU A2SU BlLU i B2LU Bl SU B2SU AlLN A2LN Al SN A2SN BlLN B2LN BlSN B2SN

4 ( UNNOTCHED J [ NOTCHED J E z u) Q).. ) ::J 1..8 ~ ~ e.6 't; L.. u:.4..5% 1.%.5% 1.% Perentage of Fiber 9 Hooked-end (Large)~ Crimped (Large) t:;:::::j Hooked-end (Small)~ Crimped (SmalO FIGURE 2 First-rak toughness versus perentage of fiber G Q) : 2.E Q).. ) ::J I- 15 G 1 5.5% 1.%.5% 1.%.5% 1.% Perentage of Fiber 9 Hooked-end (Large)~ Crimped (Large) t:::::::j Hooked-end (SmalO ~Crimped (SmalO FIGURE 3 Toughness indexes versus perentage of fiber for unnothed speimens.

5 Ramakrishnan and Yalamanhi 43 4) 25 :!: 4).r; O> :J 15 I-.5% 1.%.5% 1.%.5% 1.% Perentage of Fiber ~Hooked-end (large)~ Crimped (large) f:::::::) Hooked-end (Small)~ Crimped (SmalO FIGURE 4 Toughness indexes versus perentage of fiber for nothed speimens. rete with an equal quantity of rimped fibers. Better anhorage and bond provided by the hooked-end fibers ontributed to the inrease in toughness. The influene of the size of the speimens was not learly indiated beause of the inevitable variability in the fiber distribution. The ratios, / 1 // 5 and / 3 // 1 were alulated and are presented in Table 2. The ratios, good indiators of post-rak plasti behavior of the speimens, have values equal to 2 and 3 for and / 3 // 1, respetively, and show perfet plasti behavior. Hooked-end fiber reinfored onrete demonstrated almost perfet plasti behavior after the first rak and up to 15.5 times the first rak defletion, beause the ratios and / 3 //1 are lose to two and three. FRC with rimped fibers showed a deline in the load arrying apaity after a defletion of 5.5 times the first rak defletion. The / 3 // 1 were less than three. The differene in behavior may be attributed to the fiber effiieny. The most important variable governing the toughness index of steel fiber-reinfored onrete SFRC is the fiber effiieny. Other fators that influenge the toughness index are the position of rak, fiber ontent, and distribution of the fibers. Fiber effiieny is ontrolled by the resistane of fibers to pull out from the matrix that is developed as a result of bond strength at the fiber-matrix interfae. Beause the pull out resistane inreases with inreased fiber length, the longer the fiber the more it improves the properties of omposites. Also, beause the pull out resistane is proportional to interfaial surfae area, nonround fiber ross setions and small diameter round fibers offer more pull out resistane per unit volume than do larger diameter round fibers, beause they have more surf ae area per unit volume. Hene, a high ratio of length to diameter is assoiated with fiber effiieny. On that basis, it would appear that fibers should have an aspet ratio high enough to ensure that their tensile strength is approahed as a omposite fails. Unfortunately, that is not pratial. Many investigations indiate that use of fibers with an aspet ratio higher than 1 auses inadequate workability, FRC with nonuniform distribution of fiber, or both (9). In this investigation, the aspet ratio used was 1, and 4 to 65 for type A and B fibers, respetively. Failure of the omposites usually was governed by the fiber pull out. The advantage of the pull out type of failure is that it is gradual and dutile ompared with a more rapid and possibly atastrophi failure, whih an our if fibers are brittle and break under tension, with little or no elongation. Fiber pull out or fiber frature depends on the yield strength of the fibers, and the bond and the anhorage between the matrix and the fiber. Flexural Toughness Fator The JCI (17) and JSCE (18) methods for alulating frature toughness are idential. Toughness is defined in absolute terms as the energy required to deflet the FRC beam at a midspan of 1/15 of the span, '&tb. The flexural toughness fator Fe, whih is taken as the average flexural strength, is given by the following equation: Fe = Tb X l/'&tb X b X h 2 where Fe = flexural toughness fator, Tb = flexural toughness, '&tb = defletion of 1/15 of the span, l ==span, b = width of failed ross setion, and h = height of failed ross setion.

6 44 TRANSPORTATION RESEARCH RECORD [ UNNOTCHED J ( NOTCHED J.5% 1.%.5% 1.% Perentage of Fiber ~ Hooked-end (Large) ~ Crimped (Large) D Hooked-end (Small) ~ Crimped (SmalO FIGURE 5 Flexural toughness fator versus perentage of fiber. The flexural toughness fator values are provided in Table 2, and Figure 5 presents omparative results for unnothed and nothed beams. The flexural toughness fator had inreased as the perentage of the fibers inreased, in both types of_ fibers, exept for the large speimens with Type A fiber. Flexural toughness values inreased 5 perent for small speimens with Type A fiber, as the perentage of fiber inreased from.5 to 1. perent Similarly, the perentage inreases,, were 2 and 35 perent for small and large speimens with Type B fiber. A detailed analysis presented elsewhere (21) indiated that nothes in the beams do not influene toughness indexes (ASTM) and flexural toughness fators (JCI). Cyli Loading The ability of strutures to resist dynami loading, suh as earthquake loading, depends on the frature toughness of the material. SFRC with higher frature toughness and a very high post-rak energy absorption apaity before ollapse is a suitable material for the onstrution of earthquake-resisting strutures. The behavior of SFRC and its frature toughness when subjeted to yli loading were determined. Load-defletion urves and omplete analysis of results are presented elsewhere (21). A typial load-defletion urve obtained in yli loading test superimposed by a load-defletion urve obtained under monotoni load for the same SFRC with unnothed beams is shown in Figure 6; the same omparison for nothed speimens is shown in Figure 7. Curves under yli loading followed losely the urves for monotoni loading, indiating that the behavior of FRC under yli loading an be predited from the monotoni load urve. Total energy absorbed for ollapse appeared to be nearly the same for both loading ases. However, growth of permanent strain and deay in elasti modulus were observed after every yle, when the loading was higher than the first-rak load. There was not any disernible differene in the behavior of beams with and without nothes when subjeted to either yli loading or monotoni loading. Crak Mouth Opening Displaement In addition to the load deformation harateristis, rak mouth opening displaement (CMOD) versus load was reorded under monotoni and as well yli loading for nothed speimens. A typial load versus CMOD urve is shown in Figure 8. A similar type of behavior was observed for the load versus CMOD urves under both monotoni and yli loading. The CMOD was linear, until a rak appeared, then it beame nonlinear. The load-cmod urves and the load-defletion urves were similar for monotoni and yli loading. CONCLUSIONS Frature toughness, as measured by ASTM- and JCIreommended test proedures, inreases signifiantly with the addition of steel fibers in onrete. With an inrease in fiber ontent, the frature toughness inreases. The degree of inrease depends on the type and quantity of fibers added. The hooked-end SFRC had greater toughness than the SFRC with rimped fiber, with an equal quantity of fibers in both. The higher the FRC's fiber ontent, the lower its orresponding post-rak load drop.

7 -'*- Cyll Loading -I- Monotoni Loading i z (I) : -g Defletion, mm FIGURE 6 Load defletion urves for yli and monotoni loading for unnothed speimens. -'*- Cyli Loading -I- Monotoni Loading i z (I) : -g Defletion, mm FIGURE 7 Load defletion urves for yli and monotoni loading for nothed speimens.

8 46 TRANSPORTATION RESEARCH RECORD CYCLIC LORDING 356 (hooked nd - O~SZJ 3115!/) 267 l 2225 z "'- m 178 -I FIGURE e 9 1 Load versus CMOD urve for Beam AlLN-3. Crak Mouth Opening Displaement, mm Signifiant satter in the toughness and flexural properties alulated for SFRC is unavoidable beause of the inevitable nonuniform distribution of the randomly oriented fibers, partiularly in the ritial tension zone, both in the laboratory-ast speimens and in onrete in the field. In omparing the load-defletion behavior and the flexural properties of FRC speimens subjeted to monotoni or yli loading, the noth in the speimen did not have any influene on the toughness, other flexural properties, or the behavior of FRC. For the noth-depth/beam-depth ratio used (1:8), the FRC was not nothsensitive. In general, speimen size had an influene on the frature toughness and the mehanial parameters monitored. The stress at first rak and the ultimate strength were less for the larger speimen size. However, the ultimate strength was more size-dependent than the stress at first rak. Energy absorbed per unit net rosssetional area, and the initial elasti modulus alulated from the load defletion urves, were both independent of size. For SFRC with hooked-end fibers, the variability of the fiber distribution at the ritial setion had a muh greater influene than speimen size. Therefore, for hooked-end SFRC, the results should be interpreted with aution. There was no hange in the elasti wave transmission properties of the onrete due to the addition of fibers, as indiated by measured pulse veloities. Frature toughness indexes (/ 5, / 1, and / 3 ), alulated using ASTM Cl18, are not very sensitive to the fiber type, fiber ontent, or speimen size. The test reommended by the JCI (SF4) is relatively more sensitive to the fiber type and ontent, and it ould be used more effetively to ompare frature toughness of FRC with different fiber types and ontents. Variability of fiber distribution notied in the ritial setions of the failed speimens ut from a large slab (field onrete), and in those setions of orresponding unut speimens made in the laboratory in the required sizes, was almost the same. No differene was notied in performane or mehanial parameters monitored using the speimens ut from the field onrete and the speimens ast in the laboratory. Behavior of SFRC under monotoni and yli loading indiates that fibers primarily influene the envelope urve; yli loading did not have any adverse effet on SFRC's energy absorption apaity or flexural strength. Compared with plain onrete, FRC has higher frature toughness, first-rak strength, stati flexural strength, dutility, and postrak energy absorption apaity. For the nothed beams, the load versus CMOD urve was very similar to that of the load defletion urve. Hooked-end fibers provide greater onsisteny in terms of toughness index testing. Use of the ASTM Cl18 toughness index proedure to derive / 5, / 1, and / 3 is a poor method of determining the end produt of the toughness. ACKNOWLEDGMENT The authors thank the National Siene Foundation's Strutures and Building Systems Program Diretor, Ken P. Chong, for providing finanial support for this investigation. REFERENCES 1. Ramakrishnan, V. Steel Fiber Reinfored Shotrete; A-State-of-the-Art Report. Pro., Steel Fiber Reinfored Conrete, U.S. and Sweden Joint Seminar, Stokholm, June 3-5, 1985, Elsevier, London, England, pp Ramakrishnan, V., G. Y. Wu, and G. Hosalli. Flexural Behavior and Toughness of Fiber Reinfored Conretes. In Transportation Researh

9 Ramakrishnan and Yalamanhi 47 Reord 1226, TRB, National Researh Counil, Washington, D.C., 1989, pp Ramakrishnan, V. Superplastiized Fiber-Reinfored Conretes for the Rehabilitation of Bridges and Pavements. In Transportation Researh Reord 13, TRB, National Researh Counil, Washington, D. C., 1985, pp Ramakrishnan, V., W. V. Coyle, P.A. Kopa, and T. J. Pasko. Performane Charateristis of Steel Fiber Reinfored Superplas.tiized Con- rete. ACI SP-68, Amerian Conrete Institute, Detroit, Mih., 1981, pp Ramakrishnan, V., W. V. Coyle, V. Kulandaiswamy, and E. K. Shrader. Performane Charateristis of Fiber Reinfored Conrete With Low Fiber Contents. Amerian Conrete Institute Journal, Vol. 78, No. 5, Sept-Ot. 1981, pp Ramakrishnan, V., T. Brandshaug, W. V. Coyle, and E. K. Shrader. A Comparative Evaluation of Conrete Reinfored With Straight Steel Fibers and Fibers With Deformed Ends Glued Together Into Bundles. Amerian Conrete Institute Journal, Vol. 77, No. 3, May-June 198, pp Ramakrishilan, V., and W. V. Coyle. Steel Fiber Reinfored Superplastiized Conrete for Rehabilitation of Bridge Deks and Highway Pavements. Report DOT/RSPNDMA-5/84-2, Offie of University Researh, U.S. Department of Transportation, Ramakrishnan, V. Performane Charateristis of Steel Fiber Reinfored Superplastiized Conrete. Presented at Symposium L, Advanes in Cement-Matrix Composites. Materials Researh Soiety, University Park, Pa., Nov Balaguru, P., and V. Ramakrishnan. Mehanial Properties of Superplastiized Fiber Reinfored Conrete Developed for Bridge Deks and Highway Pavements. Report SP-93, Conrete in Transportation, Amerian Conrete Institute, Detroit, Mih., 1986, pp Ramakrishnan, V. Materials and Properties of Fiber Reinfored Conrete. Pro., International Symposium on Fiber Reinfored Conrete, Madras, India, De. 1987, pp Balaguru, P., and V. Ramakrishnan. Comparison of Slump Cone and V-B Tests as Measures of Workability for Fiber Reinfored and Plain Conrete. Cement, Conrete, and Aggregates, Vol. 9, No. 1, CCAGDP, Summer Balaguru, P., and V. Ramakrishnan. Properties of Fiber Reinfored Conrete: Workability, Behavior Under Long-Term Loading and Air Void Charateristis. Amerian Conrete Institute Materials Journal, No. 85-M23, May-June 1988, pp State-of-the-Report on Fiber Reinfored Conrete. InReport 544 IR-82: Conrete International Design and Constrution, May Report SP-81: Fiber Reinfored Conrete-International Symposium. Amerian Conrete Institute, Detroit, Mih., 1986, pp Report SP-15: Fiber Reinfored Conrete Properties and Appliations. Amerian Conrete Institute, Detroit, Mih., Fiber Reinfored Cements and Conretes; Reent Developments. (R. N. Swamy and B. Barr, eds.) Elsevier, London, England, Method of Test for Flexural Strength and Flexural Toughness of Fiber Reinfored Conrete. JCI Standards for Test Methods of Fiber Reinfored Conrete (Standard SF4), Japan Conrete Institute, 1983, pp Method of Tests for Steel Fiber Reinfored Conrete. (Standard JSCE-SF4 for Flexural Strength and Flexural Toughness of SFRC, and Standard JSCE~SF5 for Compressive Strength and Compressive Toughness of SFRC) Conrete Library, Japan Soiety of Civil Engineers, June 1984, pp Measurement of Properties of Fiber Reinfored Conrete. AC/ Journal, Proeedings, Vol. 75, No. 7, Amerian Cement Institute, Detroit, Mil;i., July 1978, pp Measurement of Properties of Fiber Reinfored Conrete, AC/ Materials Journal, Vol. 85, No. 6, Amerian Cement Institute, Detroit, Mih., Nov.-De. 1988, pp Yalamanhi, Y. S. Influene of Speimen Size, Loading Configuration, Fiber Type, and Fiber Content on Flexural Behavior of Steel Fiber Reinfored Conrete. M.S. thesis. South Dakota Shool of Mines and Tehnology, May Publiation of this paper sponsored by Committee on Mehanial Properties of Conrete.