CA1073478A - Method of mixing steel fiber reinforced concrete - Google Patents
Method of mixing steel fiber reinforced concreteInfo
- Publication number
- CA1073478A CA1073478A CA280,718A CA280718A CA1073478A CA 1073478 A CA1073478 A CA 1073478A CA 280718 A CA280718 A CA 280718A CA 1073478 A CA1073478 A CA 1073478A
- Authority
- CA
- Canada
- Prior art keywords
- coarse
- aggregate
- steel
- concrete
- coarse aggregate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/38—Fibrous materials; Whiskers
- C04B14/48—Metal
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/012—Discrete reinforcing elements, e.g. fibres
Abstract
Abstract of the Disclosure A method of mixing steel fiber reinforced concrete wherein the aggregates used have a coarse aggregate-to-fine aggregate ratio (G/S) of greater than 1.0, and the particle diameter of the coarse aggregate is such that more than 50% is retained on a sieve of the ASTM ?-inch mesh, thus causing steel fibers to be intentionally selectively distrib-uted around the larger aggregate particles, wherein, G and S
denote the weight of the coarse and fine aggregates in unit concrete volume (kg/m3), respectively.
denote the weight of the coarse and fine aggregates in unit concrete volume (kg/m3), respectively.
Description
lO'~3't78 .
~ackground of the Invention The present invention relates to a method of mixing steel fiber reinforced concrete.
' ~ -~ he-NIRAND concrete (the trade mark of Battle ~Development CPrporation) according to U.S. Patent No. 3,429,094 to Romualdi et al is typical of the prior art steel fiber re-inforced concretes (hereinafter simply referred to as SFRC).
Romualdi et al advance a fiber spacing concept and state -that on the assumption of steel fibers being randomly orientated and uniformly distributed within concrete, the concrete ~trength increases with decrease in the calculated average fiber spacing s-given by the following equation, and particularly the concrete ~strength increases remarkably when s -~ 0.5 inches. `
s = 13.8d \ ~
P ~ .
-where d = diameter of steel fiber p = percent by volume of steel fiber This constitutes the subject matter of the above--mentioned U.S. patent.
According to the above-mentioned concept, it should be -possible to increase concrete strength by increasing the ~percent by volume of steel fiber p and thereby decreasing the -~alculated spacing s. In the actual practice, however, there is a limit to the amount of steel fibers to be added, and more--~ver -this maximum value is as low as 4% in terms of the value _ . o~ p .
m/i`~
_ ~0~34q~
~ackground of the Invention The present invention relates to a method of mixing steel fiber reinforced concrete.
' ~ -~ he-NIRAND concrete (the trade mark of Battle ~Development CPrporation) according to U.S. Patent No. 3,429,094 to Romualdi et al is typical of the prior art steel fiber re-inforced concretes (hereinafter simply referred to as SFRC).
Romualdi et al advance a fiber spacing concept and state -that on the assumption of steel fibers being randomly orientated and uniformly distributed within concrete, the concrete ~trength increases with decrease in the calculated average fiber spacing s-given by the following equation, and particularly the concrete ~strength increases remarkably when s -~ 0.5 inches. `
s = 13.8d \ ~
P ~ .
-where d = diameter of steel fiber p = percent by volume of steel fiber This constitutes the subject matter of the above--mentioned U.S. patent.
According to the above-mentioned concept, it should be -possible to increase concrete strength by increasing the ~percent by volume of steel fiber p and thereby decreasing the -~alculated spacing s. In the actual practice, however, there is a limit to the amount of steel fibers to be added, and more--~ver -this maximum value is as low as 4% in terms of the value _ . o~ p .
m/i`~
_ ~0~34q~
- 2 -According to the specifieatlon oi U.S. Patent No.
3,429,0~4 and the above-mentioned fiber spaeing eoneept, in the case of steel fiber~ having a fiber diameter of about 0.5 mm, the eorresponding value of p to the proper caleulated spaeing 8 = 0.5 inehes (12.7 mm) 18 in the range of 0.2 to 0.4%. In the aetual praetiee of WIRAND eonerete, the amount of steel fiber used is several to lO times that amount or about 2~, and eonsequently the setting of the eriti-eal value is not of much importance.
Further, the fiber spacing eoneept does not take into eonsideration those important $aetors oi steel fibers ior reinforeing eoncrete, sueh a~, the bonding between steel fiber and concrete, tensile strength of steel fiber and aspeet ratio of steel fiber (the ratio of diameter d to length 1 or l/d).
The U.S. patent speeification also proposes the use of steel __ fibers having the moduIus of elastieity within the range of about 27 to 32 million p.s.i. However, it is a eommon kno~ledge in the art of fiber reinforeed eomposite materials that it is ~ necessary to use fibers of a greater modulus of elastieity than i that of a mat~ to be reinforced (eonerete in the case of this s invention). Therefore, the disclosure of the above-mentioned U.S. patent and its proposed fiber spacing concept do not differ much from the common-sense knowledge that concrete strength ean be increased by increasing the percentage of the steel fiber content.
, ,~ .
. - - - . , .,- .. ;, ;
With the exis~ing technique of ~FRC accordlng to the fiber spacing concept, the use of large coarse aggregate i8 avoided on the ground that its uee tends to impede the desired random snd uniform distribution of steel fibers, and importance is attached to reducing the calculated spacing. Thus, a mi~-ing method is used in which aggregates having as small particle diameter as possible are used, and the amount of the fine aggregate i9 increased greatly. As a result, the matrix concrete has a composition different from that of the conventionally used plane concrete. For in3tance, in the embodiments di~closed in the specification of U.8. Patent No. 3,429,094, the matris concrete i3 a mixture of sand and coment, and other data which have been published show that only sands sre used as aggregates, and if coarse aggregate is used, its size must usually be smaller than 3/8 incheR (9.5 mm). The data on the WIRAND concrete also show that a coarse aggregate of small diameter is added in a small amount and that the maximum diameter of coarse aggregate is kept small. Thus, it is emphasized that the WIRAND concrete is not prepared by adding steel fibers into conventional plane concrete including a coarse aggregate having a large maximum diameter.
.
In addition to the data on the WIRAND concrete, there are - other data on the ~FRC and these data also show that the maximum diameter of coarse ag Fegates i8 less than 3/8 inches (9.5 mm).
.
. . .
.
However, as mentioned previously, ths use of a small amount of coar~e aggregate o$ small diameter and a large amount of fine aggregate gives rise to the following disadvantages.
(a) As compared in terms of the coarse aggregate of the same weight, decrease in the particle diameter results in an increased surface area, thus requiring a large amount of surface water or moisture and thereby causing an increase in the amount of water content. This tendency will be further promoted by the addition of steel fiber.
(b) To en~ure a fi~ed water-cement ratio, the unit weight of cement must be increa~ed with an increase in the amount of water content, and moreover the resulting increase in the amount of cement paste has a greater danger of causing drying shrinkage crack.
(c) Coarse aggregates having the ma~imum diameter of less than 3/8 inche~ (about 10 mm) are of the special type which generally are not readily available, are d~fficult to prepare and co~t more.
.
'''' ~'''~''' , ~ I .
': ` ' ,, : . ~. ... .
10~3~8 Summary of the Invention It i8 the object of the present invention to provide an economical and readily performable method of mixing steel fiber reinforced concrete having improved toughne~s, shock impact resistance, bending strength and 80 on.
Thu3, the present invention comprises a method of mi~ing steel fiber reinforced concrete featuring in that in contrast to the conventional method intended toward ensuring uniformly distributed and randomly orientated steel fibers, the method of this invention is intended toward selectively distr$buting steel~fibers around the l~rge coarse aggregate particles, and this purpose is attained by selecting the coarse aggregate-to-fine aggregate ratio (G/S) of the aggre B tes to be greater than 1.0, by selecting the particle size or diameter of the coarse aggregate in such a manner that more than 50% by weight is retained on a sieve.of the ASTM ~-inch mesh, and by using steel fibers with a tenæile ~trength of greater than 30 kg/mm2. While : the manner of selective or partial distribution of steel fibers can be more easily explained by indicating in percen~age by volume the content of large-diameter coarse aggregate required to prevent the eteel fibers from freely changing their orientation and position, the coarse aggregate content i8 gi~en in percent by weight for purposes of simplifying the instruction of the pro-portion on the job-site.
.
- , . .
..
Brief Description oi the Drawing Fig. 1 shows schematic sectional views of steel fiber reinforced concretes, showing in (a) a prior art product and in (b) the product produced by the method of thi 8 invention.
Fig. 2 is a graph show1ng the grading curve of the flne aggregate used in the e~amples of this invention.
..
Fig. 3 is a graph showing the grading curves of the coarse aggregates used in the e~ample A and the comparative e~amples (B and C).
De~ailed Description of the Invention The characteristic features of this invention vill now be described enumeratively.
, (1) The aggregates used have the ratio (G/S) of coarse aggregate to fine aggregate of greater than 1Ø
According to the average fiber spacing concept, the smaller the aggregate size, the more uniformly the steel fibers will be distributed with a greater degree of freedom for changing their orientation. For this reason, the fine aggregate volume percentage S/a in the total aggregate volume in the conventional SFRC is increased .
;. - . `
. , . . ~- .
~34q8 (over about 60~), and the maximum grain size or diameter of the coarse aggregate i8 also kept small. In accordance with the average fiber spacing concept, if the size of the aggregstes is greater than the average flber spacing, the steel fibers cannot penerate into the aggregate particle lumps thus placing limits to the po~ition and orientation of the steel fibers. In accordance with the conception of this invention which is contrary to that of the prior art method, the amount of large-diameter coarse aggregate i8 increa~ed, thus permitting the select-ive distribution of steel fibera and thereby producing the following effects.
The coarse aggregste used has a ~ufficientl~ high strength.
This has the effect of allowing the coarse aggregate to serve as crack arrestor similarly as the steel fibers.
~According to the invention, by selectiDg the ratio (G/S) ~of coarse aggregate to fine aggregate to be greater than 1.0, namely, by selecting the fine aggregate percentage (S/a) to be smaller than about 50%, in cooperation with the particle diameter of the coarse aggregate being selected large as will be described later, the required amount of surface water and hence the unit weight of cement can be reduced. In the case of the conventional SFRC, the ratio of coarse aggreBate to fine sggregate is less than 1Ø
' :.
-, . .
iO~ ~ 78 The particle diameter of the coarse aggregate i~selected 80 that more than 50% is retained on a sieve of the ASTM ~-inch mesh. In the case of the conventional SFRC, less than lO~ of the coarse aggre-gate i8 retained on a ~-inch sieve. .While there are instances where the particle size of coarse aggregate 18 indicated by the size of the ccarse agOEegate (in the case of this invention, the size of the aggregate particle~
is mostly greater than 20 mm) indicated by the size oi opening of the sieve having the smallest size among those which pass 90% of the coarse aggregate, according to the present invention the size of the coarse aggre-gate i9 indicated as mentioned above, since it i8 desired to clearly indicate the ob~ect of comparison between the invention and the prior art method and since the proper particle size of the coarse aggregate can be indicated by .
the maximum size as well as the grain size d1stribution.
The published literatures quite rarely state the use of ;~ i coarse aggregates having the particle diameter of greater - than 3/8", but none of these literatures refer to the determination-of the coarse aggregate percentage for the purposeæ mentioned in connection with the invention, and the fine aggregate percentages stated are also not so small as that of the present invention.
:~ (3) The tensile strength of steel fibers is selected to be greater than ~0 kg/mm2.
- : .
1073~78 In the method of thi~ invention, steel fibers with a tensile strength of ~reater than 30 kg/mm2 and aspect -~
ratîo (l/d) of about 30 to 100 are added up to the maximum of about 3.0% in percent by volume. In the past, the modul w of elasticity of fibers has been treated but the strength of fibers has not been referred to in ang respect. However, the fibers used must possess a sufficient bonding strength with respect to the matri~ or concrete, and moreover the tensile strength of the fiber itself must be greater than 30 kg/mm2 in order to ensure effective utiliæation of this bonding strength. The required strength, shape, size, etc., of this concrete reinforcing steel fiber have been discovered and disclosed in the Japanese ~aid-Open Patent Application Publication Tokukai-Sho No. 51-126218. The invention discloses the concrete reinforcing steel flber featuring the following relationship ~ > _ 2ab ~b where L, a, b, ot and ~b respectively denote the length, cross-sectional area, circumferential length, tensile strength, and bonding strength per unit area of the fiber.
In the conventional SFRC, the fibers are uniformly distributed and orientated randomly 80 as to reduce the spacing between the fibers, whereas according to the invention the fibers are added so as to be selectively distributed around the laree-diameter coarse aggregate particles. Fig. 1 sc~ematically shows in (a) the cross - section of the SFRC produced by the prior . .
10~ ~ 78 . ~ .
art method and in (b) the SFRC produced by the method of this invention. In the Figuree, the 8egmental lines indicats fibers, the scattered dots indicate fine sggregate particle8 and the circles indicate coarse aggregate~partlcles.
.
In accordance with the present invention, as compared with the case uhere a small-diameter coarse aggr~gate is used, the interparticle spaces where crack may occur are reduced thus effectively preventing the occurrence of any crack tending to cut thrQugh the fibers, and moreover the coarse aggregate serves as a crack arrestor.
The method of this invention can be performed in the above-mentioned manner, and the following Table l shows the result of an over-all comparison made between the SFRC produced ~y ihe ethod of thi~ invention and the oonventional S~ 0.
, . ~ . .
Table 1 SFRC of this invention Conventional ~FRC
.
Particle diameter More than 50%
of retained on a1 Less than 3/8 inche~
coarse agg~egate ~-inch sieve Ratio of coarse aggregate to fine Greater than 1.0 Less than 1.0 aggregate (G/S) T
_ Strength of Greater than steel fiber 30 kg/mmNot defined .... . .. _ .
Distrubution of Selectively distri- Uniformly distributed steel fiber buted around large I with small fiber ~pacing aggregate particles Cement content About the same as A I conventional ~la~ xtremely large !I concrete PJ~ ~
. I
.
In accordance with the method of this invention, there is no need to use any spec~al aggregates of very small diameter, and therefore the necessary aggregates can be readily obtained cheaply.
Further, since the water content can be decreased with the resulting decrease in the unit weight of cement, it i9 possible to produce cheaply the desired SFRC with improved toughness, shock i~pact resistance,lbending strength, etc.
, . ~
. ` ' : ~ . . . ` -073~78 r Description of the Preferred Embodimente The following Table 2 shows the composition and bending streneth of the SFRC's produced in the e~amples of the method according to the invention. The steel fibers used were steel fibers ofO.5 s 0.5 x ~0 mm size (known by the trade name "TESUSA", developed by NIPPON KOKAN XA~U5HIEI
KAISHA and manufactured by SANGO CO., LTD.1 produced by shredding steel sheet, and the tensile strength of the iibers was 32 kg/mm2. The praticle size distribution of the fine aggregate used was as shown in Fig. 2, and the coarse sggregate used was of the ASTM No. 8 class whose particle size distribution is shown by the line A in Fig. ~. In the Table, the initial and ultimate strengths according to the bending crack measurements show the reRults obtained according to the JISA 1106 concrete bending strength tsst method. Table 2 also shows a~ the comparative examples the values obtained from the experimental reports which have previously been published.
The Comparative Example 1 was stated in the "Pa~ement Applica-tions for Steel Fibrous Concrete", Transportation Engineering Journal, February 1975; the Comparative Example 2 was stated in the Construction Engineering Research Laboratory Technical Report M-147, August 1975; the Comparative Example 3 was stated in the "Different Concrete Offers Reduced ~aintenance Costs", Public Works, August 1972; and the Comparative Example 4 Nas stated in the "Fibrous Concrete Pavement of Tomorro~", American Concrete Paving Association ~ews Letter Vol. 8, No. 10, October 1972. In Fig. 3, the lines B and C show the grading curves of r~
', .. ~ :
... ..
the coarse aggregates used in the Comparative Bxample 1 to 3 and the Comparative E~ample 4, respectively.
Table 2 ~-~xamples of the Comparative invention examples . 1 2 ~ 3 4 1 r 2 ' ' 3 r----Cement 220 220 320 320 446 308 502 504 _ Sand (S) 831 ~17 722 709 890 8021003 93 COhr~e hggreghte (G) 173 ~060 ~156 1143 600 ~
h Steel fiber 79 157 79 157 104 119 157 119 h _ ~ Water 160 160 160 160 223 172 229 168 1----- ~ .. . -'I
Water-cement ratio (~o) 72 72 ¦ 50 50 50 56 46 33 ~Maximum coarse aggre- 25 25 ~ 25 25 9.5 9.5 9 5 12.7 . gate diameter (mm~ I ~ ~ _ ._ Ratio of fine aggregate .
to coarse aggreg(G/S) 1-29 1.30,1.60 1.61 0.67 0 996 0.42 0.58 nitial cracking tre2ngth 42.Q 5~.0 65.9 74.6 ~ ~
ltimate cracking strength L56.165.1j 73.9 127. l ~ .
,_~_ . .. .... _ __ __ ___ __ ..
-, - . . - :.. ~,, . -
Further, the fiber spacing eoneept does not take into eonsideration those important $aetors oi steel fibers ior reinforeing eoncrete, sueh a~, the bonding between steel fiber and concrete, tensile strength of steel fiber and aspeet ratio of steel fiber (the ratio of diameter d to length 1 or l/d).
The U.S. patent speeification also proposes the use of steel __ fibers having the moduIus of elastieity within the range of about 27 to 32 million p.s.i. However, it is a eommon kno~ledge in the art of fiber reinforeed eomposite materials that it is ~ necessary to use fibers of a greater modulus of elastieity than i that of a mat~ to be reinforced (eonerete in the case of this s invention). Therefore, the disclosure of the above-mentioned U.S. patent and its proposed fiber spacing concept do not differ much from the common-sense knowledge that concrete strength ean be increased by increasing the percentage of the steel fiber content.
, ,~ .
. - - - . , .,- .. ;, ;
With the exis~ing technique of ~FRC accordlng to the fiber spacing concept, the use of large coarse aggregate i8 avoided on the ground that its uee tends to impede the desired random snd uniform distribution of steel fibers, and importance is attached to reducing the calculated spacing. Thus, a mi~-ing method is used in which aggregates having as small particle diameter as possible are used, and the amount of the fine aggregate i9 increased greatly. As a result, the matrix concrete has a composition different from that of the conventionally used plane concrete. For in3tance, in the embodiments di~closed in the specification of U.8. Patent No. 3,429,094, the matris concrete i3 a mixture of sand and coment, and other data which have been published show that only sands sre used as aggregates, and if coarse aggregate is used, its size must usually be smaller than 3/8 incheR (9.5 mm). The data on the WIRAND concrete also show that a coarse aggregate of small diameter is added in a small amount and that the maximum diameter of coarse aggregate is kept small. Thus, it is emphasized that the WIRAND concrete is not prepared by adding steel fibers into conventional plane concrete including a coarse aggregate having a large maximum diameter.
.
In addition to the data on the WIRAND concrete, there are - other data on the ~FRC and these data also show that the maximum diameter of coarse ag Fegates i8 less than 3/8 inches (9.5 mm).
.
. . .
.
However, as mentioned previously, ths use of a small amount of coar~e aggregate o$ small diameter and a large amount of fine aggregate gives rise to the following disadvantages.
(a) As compared in terms of the coarse aggregate of the same weight, decrease in the particle diameter results in an increased surface area, thus requiring a large amount of surface water or moisture and thereby causing an increase in the amount of water content. This tendency will be further promoted by the addition of steel fiber.
(b) To en~ure a fi~ed water-cement ratio, the unit weight of cement must be increa~ed with an increase in the amount of water content, and moreover the resulting increase in the amount of cement paste has a greater danger of causing drying shrinkage crack.
(c) Coarse aggregates having the ma~imum diameter of less than 3/8 inche~ (about 10 mm) are of the special type which generally are not readily available, are d~fficult to prepare and co~t more.
.
'''' ~'''~''' , ~ I .
': ` ' ,, : . ~. ... .
10~3~8 Summary of the Invention It i8 the object of the present invention to provide an economical and readily performable method of mixing steel fiber reinforced concrete having improved toughne~s, shock impact resistance, bending strength and 80 on.
Thu3, the present invention comprises a method of mi~ing steel fiber reinforced concrete featuring in that in contrast to the conventional method intended toward ensuring uniformly distributed and randomly orientated steel fibers, the method of this invention is intended toward selectively distr$buting steel~fibers around the l~rge coarse aggregate particles, and this purpose is attained by selecting the coarse aggregate-to-fine aggregate ratio (G/S) of the aggre B tes to be greater than 1.0, by selecting the particle size or diameter of the coarse aggregate in such a manner that more than 50% by weight is retained on a sieve.of the ASTM ~-inch mesh, and by using steel fibers with a tenæile ~trength of greater than 30 kg/mm2. While : the manner of selective or partial distribution of steel fibers can be more easily explained by indicating in percen~age by volume the content of large-diameter coarse aggregate required to prevent the eteel fibers from freely changing their orientation and position, the coarse aggregate content i8 gi~en in percent by weight for purposes of simplifying the instruction of the pro-portion on the job-site.
.
- , . .
..
Brief Description oi the Drawing Fig. 1 shows schematic sectional views of steel fiber reinforced concretes, showing in (a) a prior art product and in (b) the product produced by the method of thi 8 invention.
Fig. 2 is a graph show1ng the grading curve of the flne aggregate used in the e~amples of this invention.
..
Fig. 3 is a graph showing the grading curves of the coarse aggregates used in the e~ample A and the comparative e~amples (B and C).
De~ailed Description of the Invention The characteristic features of this invention vill now be described enumeratively.
, (1) The aggregates used have the ratio (G/S) of coarse aggregate to fine aggregate of greater than 1Ø
According to the average fiber spacing concept, the smaller the aggregate size, the more uniformly the steel fibers will be distributed with a greater degree of freedom for changing their orientation. For this reason, the fine aggregate volume percentage S/a in the total aggregate volume in the conventional SFRC is increased .
;. - . `
. , . . ~- .
~34q8 (over about 60~), and the maximum grain size or diameter of the coarse aggregate i8 also kept small. In accordance with the average fiber spacing concept, if the size of the aggregstes is greater than the average flber spacing, the steel fibers cannot penerate into the aggregate particle lumps thus placing limits to the po~ition and orientation of the steel fibers. In accordance with the conception of this invention which is contrary to that of the prior art method, the amount of large-diameter coarse aggregate i8 increa~ed, thus permitting the select-ive distribution of steel fibera and thereby producing the following effects.
The coarse aggregste used has a ~ufficientl~ high strength.
This has the effect of allowing the coarse aggregate to serve as crack arrestor similarly as the steel fibers.
~According to the invention, by selectiDg the ratio (G/S) ~of coarse aggregate to fine aggregate to be greater than 1.0, namely, by selecting the fine aggregate percentage (S/a) to be smaller than about 50%, in cooperation with the particle diameter of the coarse aggregate being selected large as will be described later, the required amount of surface water and hence the unit weight of cement can be reduced. In the case of the conventional SFRC, the ratio of coarse aggreBate to fine sggregate is less than 1Ø
' :.
-, . .
iO~ ~ 78 The particle diameter of the coarse aggregate i~selected 80 that more than 50% is retained on a sieve of the ASTM ~-inch mesh. In the case of the conventional SFRC, less than lO~ of the coarse aggre-gate i8 retained on a ~-inch sieve. .While there are instances where the particle size of coarse aggregate 18 indicated by the size of the ccarse agOEegate (in the case of this invention, the size of the aggregate particle~
is mostly greater than 20 mm) indicated by the size oi opening of the sieve having the smallest size among those which pass 90% of the coarse aggregate, according to the present invention the size of the coarse aggre-gate i9 indicated as mentioned above, since it i8 desired to clearly indicate the ob~ect of comparison between the invention and the prior art method and since the proper particle size of the coarse aggregate can be indicated by .
the maximum size as well as the grain size d1stribution.
The published literatures quite rarely state the use of ;~ i coarse aggregates having the particle diameter of greater - than 3/8", but none of these literatures refer to the determination-of the coarse aggregate percentage for the purposeæ mentioned in connection with the invention, and the fine aggregate percentages stated are also not so small as that of the present invention.
:~ (3) The tensile strength of steel fibers is selected to be greater than ~0 kg/mm2.
- : .
1073~78 In the method of thi~ invention, steel fibers with a tensile strength of ~reater than 30 kg/mm2 and aspect -~
ratîo (l/d) of about 30 to 100 are added up to the maximum of about 3.0% in percent by volume. In the past, the modul w of elasticity of fibers has been treated but the strength of fibers has not been referred to in ang respect. However, the fibers used must possess a sufficient bonding strength with respect to the matri~ or concrete, and moreover the tensile strength of the fiber itself must be greater than 30 kg/mm2 in order to ensure effective utiliæation of this bonding strength. The required strength, shape, size, etc., of this concrete reinforcing steel fiber have been discovered and disclosed in the Japanese ~aid-Open Patent Application Publication Tokukai-Sho No. 51-126218. The invention discloses the concrete reinforcing steel flber featuring the following relationship ~ > _ 2ab ~b where L, a, b, ot and ~b respectively denote the length, cross-sectional area, circumferential length, tensile strength, and bonding strength per unit area of the fiber.
In the conventional SFRC, the fibers are uniformly distributed and orientated randomly 80 as to reduce the spacing between the fibers, whereas according to the invention the fibers are added so as to be selectively distributed around the laree-diameter coarse aggregate particles. Fig. 1 sc~ematically shows in (a) the cross - section of the SFRC produced by the prior . .
10~ ~ 78 . ~ .
art method and in (b) the SFRC produced by the method of this invention. In the Figuree, the 8egmental lines indicats fibers, the scattered dots indicate fine sggregate particle8 and the circles indicate coarse aggregate~partlcles.
.
In accordance with the present invention, as compared with the case uhere a small-diameter coarse aggr~gate is used, the interparticle spaces where crack may occur are reduced thus effectively preventing the occurrence of any crack tending to cut thrQugh the fibers, and moreover the coarse aggregate serves as a crack arrestor.
The method of this invention can be performed in the above-mentioned manner, and the following Table l shows the result of an over-all comparison made between the SFRC produced ~y ihe ethod of thi~ invention and the oonventional S~ 0.
, . ~ . .
Table 1 SFRC of this invention Conventional ~FRC
.
Particle diameter More than 50%
of retained on a1 Less than 3/8 inche~
coarse agg~egate ~-inch sieve Ratio of coarse aggregate to fine Greater than 1.0 Less than 1.0 aggregate (G/S) T
_ Strength of Greater than steel fiber 30 kg/mmNot defined .... . .. _ .
Distrubution of Selectively distri- Uniformly distributed steel fiber buted around large I with small fiber ~pacing aggregate particles Cement content About the same as A I conventional ~la~ xtremely large !I concrete PJ~ ~
. I
.
In accordance with the method of this invention, there is no need to use any spec~al aggregates of very small diameter, and therefore the necessary aggregates can be readily obtained cheaply.
Further, since the water content can be decreased with the resulting decrease in the unit weight of cement, it i9 possible to produce cheaply the desired SFRC with improved toughness, shock i~pact resistance,lbending strength, etc.
, . ~
. ` ' : ~ . . . ` -073~78 r Description of the Preferred Embodimente The following Table 2 shows the composition and bending streneth of the SFRC's produced in the e~amples of the method according to the invention. The steel fibers used were steel fibers ofO.5 s 0.5 x ~0 mm size (known by the trade name "TESUSA", developed by NIPPON KOKAN XA~U5HIEI
KAISHA and manufactured by SANGO CO., LTD.1 produced by shredding steel sheet, and the tensile strength of the iibers was 32 kg/mm2. The praticle size distribution of the fine aggregate used was as shown in Fig. 2, and the coarse sggregate used was of the ASTM No. 8 class whose particle size distribution is shown by the line A in Fig. ~. In the Table, the initial and ultimate strengths according to the bending crack measurements show the reRults obtained according to the JISA 1106 concrete bending strength tsst method. Table 2 also shows a~ the comparative examples the values obtained from the experimental reports which have previously been published.
The Comparative Example 1 was stated in the "Pa~ement Applica-tions for Steel Fibrous Concrete", Transportation Engineering Journal, February 1975; the Comparative Example 2 was stated in the Construction Engineering Research Laboratory Technical Report M-147, August 1975; the Comparative Example 3 was stated in the "Different Concrete Offers Reduced ~aintenance Costs", Public Works, August 1972; and the Comparative Example 4 Nas stated in the "Fibrous Concrete Pavement of Tomorro~", American Concrete Paving Association ~ews Letter Vol. 8, No. 10, October 1972. In Fig. 3, the lines B and C show the grading curves of r~
', .. ~ :
... ..
the coarse aggregates used in the Comparative Bxample 1 to 3 and the Comparative E~ample 4, respectively.
Table 2 ~-~xamples of the Comparative invention examples . 1 2 ~ 3 4 1 r 2 ' ' 3 r----Cement 220 220 320 320 446 308 502 504 _ Sand (S) 831 ~17 722 709 890 8021003 93 COhr~e hggreghte (G) 173 ~060 ~156 1143 600 ~
h Steel fiber 79 157 79 157 104 119 157 119 h _ ~ Water 160 160 160 160 223 172 229 168 1----- ~ .. . -'I
Water-cement ratio (~o) 72 72 ¦ 50 50 50 56 46 33 ~Maximum coarse aggre- 25 25 ~ 25 25 9.5 9.5 9 5 12.7 . gate diameter (mm~ I ~ ~ _ ._ Ratio of fine aggregate .
to coarse aggreg(G/S) 1-29 1.30,1.60 1.61 0.67 0 996 0.42 0.58 nitial cracking tre2ngth 42.Q 5~.0 65.9 74.6 ~ ~
ltimate cracking strength L56.165.1j 73.9 127. l ~ .
,_~_ . .. .... _ __ __ ___ __ ..
-, - . . - :.. ~,, . -
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of mixing steel fiber reinforced concrete using cement, coarse and fine aggregates and steel fibers characterized in that, the weight ratio (G/S) of said coarse aggregate to said fine aggregate is greater than 1.0, said coarse aggregate having a particle diameter selected in a manner that more than 50% is retained on a sieve of the ASTM 1/2 - inch mesh and having particles with a maximum diameter of about 1 inch, said steel fibers having a tensile strength of greater than 30 kg/mm and an aspect ratio of about 30 to 100, and the maximum total volume of said steel fibers in said concrete not exceeding about 3.0%.
2. A steel fiber reinforced concrete comprising cement, coarse and fine aggregates and steel fibers characterized in that, the weight ratio (G/S) of said coarse aggregate to said fine aggregate is greater than 1.0, said coarse aggregate having a particle diameter selected in a manner that more than 50% is retained on a sieve of the ASTM 1/2 - inch mesh, said steel fibers having a tensile strength of greater than 30 kg/mm2 and an aspect ratio of about 30 to 100, the maximum total volume of said steel fibers in said concrete not exceeding about 3.0% and said steel fibers being selectively distributed around the large coarse aggregate particles having a maximum diameter of about 1 inch.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9126976A JPS5317635A (en) | 1976-08-02 | 1976-08-02 | Blending method of steel fiber reinforced concrete |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073478A true CA1073478A (en) | 1980-03-11 |
Family
ID=14021711
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,718A Expired CA1073478A (en) | 1976-08-02 | 1977-06-16 | Method of mixing steel fiber reinforced concrete |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5317635A (en) |
| CA (1) | CA1073478A (en) |
| DE (1) | DE2733593A1 (en) |
| GB (1) | GB1532190A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6147703A (en) * | 1984-08-10 | 1986-03-08 | Matsushita Electric Works Ltd | Resin composition for coating electronic part |
| CN113636817A (en) * | 2021-08-30 | 2021-11-12 | 西京学院 | Concrete containing recycled PVC aggregate and preparation method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4890323A (en) * | 1972-03-06 | 1973-11-26 | ||
| JPS50139122A (en) * | 1974-04-25 | 1975-11-06 | ||
| JPS5140368A (en) * | 1974-09-20 | 1976-04-05 | Sumitomo Metal Ind | Ikeisuchiirufuaibaa no seizohoho |
| JPS5153526A (en) * | 1974-11-06 | 1976-05-12 | Nippon Steel Corp | KYOKAKONKURIITOSEIKOZOZAIRYO |
-
1976
- 1976-08-02 JP JP9126976A patent/JPS5317635A/en active Pending
-
1977
- 1977-06-16 CA CA280,718A patent/CA1073478A/en not_active Expired
- 1977-06-17 GB GB2536577A patent/GB1532190A/en not_active Expired
- 1977-07-26 DE DE19772733593 patent/DE2733593A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB1532190A (en) | 1978-11-15 |
| JPS5317635A (en) | 1978-02-17 |
| DE2733593A1 (en) | 1978-02-09 |
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