CA1092388A - Method of incorporating multifilament strands of carbon fibers into cement to produce reinforced structures having improved flexural strengths - Google Patents
Method of incorporating multifilament strands of carbon fibers into cement to produce reinforced structures having improved flexural strengthsInfo
- Publication number
- CA1092388A CA1092388A CA318,790A CA318790A CA1092388A CA 1092388 A CA1092388 A CA 1092388A CA 318790 A CA318790 A CA 318790A CA 1092388 A CA1092388 A CA 1092388A
- Authority
- CA
- Canada
- Prior art keywords
- epoxy resin
- hydrophobic
- cement
- cementitious
- resin system
- 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
- C04B14/386—Carbon
-
- 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
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/10—Coating or impregnating
- C04B20/1018—Coating or impregnating with organic materials
- C04B20/1029—Macromolecular compounds
- C04B20/1037—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
-
- 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
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/0045—Polymers chosen for their physico-chemical characteristics
- C04B2103/0052—Hydrophobic polymers
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Nanotechnology (AREA)
- Civil Engineering (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Reinforced Plastic Materials (AREA)
- Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Method of incorporating multifilament strands of carbon fibers into an aqueous hardenable hydraulic cementi-tious matrix which can be set to produce a reinforced struc-ture having improved flexural strength which comprises treat-ing the fiber strands with a hydrophobic resin system prior to adding them to the cementitious matrix.
Method of incorporating multifilament strands of carbon fibers into an aqueous hardenable hydraulic cementi-tious matrix which can be set to produce a reinforced struc-ture having improved flexural strength which comprises treat-ing the fiber strands with a hydrophobic resin system prior to adding them to the cementitious matrix.
Description
1~9Z3~ 10,571 BACKGROUND OF THE INVENTION
This invention relates to an improved method of incorporating multifilament strands of carbon fibers i~to an aqueous hardenable hydraulic cementltious matrix which can be set to produce a carbon fiber-reinforced cementitious structure having improved flexural strength. More partic-ularly, this invention relates to the preparation of a carbon fiber-reinforced structure having improved flexural strength from an aqueous hardenable hydraulic c~men i~ious matrix containing multifilament strands of carbon fibers whlch have been treated with a hydrophobic resin system prior to being incorporated into the cementitious matrix.
Multifilament strands of carbon fibars have hereto-fore been employed to reinfor~e cement in an efort to increase the ~lexural strength of such cement. However, because of poor bonding between the filaments of the strands, a~d between -~
the filaments of such strands and the cement, little or no improv~ment in the strength of the cement was attained by the addition of these fiber strands.
SUMMARY~ VT~
.'~ ~ ~ ' ';' . .
- In accordance with the~ present invention it has now been discovered that a carbo~ fiber-reinforced cementi-tious structure having improved flexural strength can be prepared from an aqueous hardenable hydraulic cementitious matrix to which have been added multifilament strands of carbon fibers which ha~e been treated with a hydrophobic 10,571 ~()9Z3~8 resin system. The fiber-reinforced structures prepared in this manner have been found to exhibit increases in flexural strength in excess of fifty percent (50/0) over the flexural strength of structures prepared in like manner from fiber strands which have not been treated with a hydrophobic resin system.
BRIEF DESCRIPTION OF, THE DRAWINGS
Figure 1 is an isometric view showing the end portion o~ a cement beam whioh has been reinforced with multifilament strands of carbon fibers arranged in two horizontal rows.
Figure 2 is a top plane view of a mould suitable for the fabrication of the carbon fiber-reinforced cement beams of Figure 1. The view shows the first horizontal row of fiber strands being laid in th~ mould.
Figure 3 is a side schematic view of one of the compartments of the mould depicted in Figure 2 after two :~
horizontal rows of fiber strands have been laid.
DETAILED DESCRIPTION OF THE INVENTION
.. .
Any hydraulic cement can be employed in the c~ment composition employed in the inventionO Aggregate filler mate-rial may be employed together with the hydraulic cement in :~
amounts convent:ionally employed. If a filler is employed, how- -e~er9 it is preferably a fine non-abrasive aggregate material, such as fly ash, and does not exc~ed twenty percent ~ ;
of the total weight of the cement and aggregate material. ~ :
~ .
10,571 ~g2388 H~gh modulus, high strength carb~n fibers suitable for use in the instant invention can be prepared as described in U. S. Patents 3,454,362, 3,41'2~062 and 4,005,133. The term "carbon" as used herein is intended to include graphitlc ant non-graphitic ibers.
The amount of fibers e~ployed is such as to obtain the desired strength characteristics, typically from 1 part by weight to 6 parts by weight of fibers per 100 parts by weight of the "dry components" of the cementitious c~mposi-tion. By "dry components" in this contex~ is meant the cement and other solid aggregate filler material (if present) which together make up the cementitious composition, but not including the carbon fiber itself. Most usually, the fibers are present in an amount of from 2~5 parts by weight to 5 parts by weight per 100 par~s by weight of the dry materials.
The water, o course, must be employed in an æmount suf~icient to hydrate the cement. In order to produce ~
cementitious structures having max~mum strength, however, ~ ~ -the amount of water sho~ld be held to a mi~imum consistent ~`
with this purpose. Typically~ from about 25 parts by weight to about 55 parts by weight, preferably ~rom about 30 parts by weight to 45 parts by weight, of water per 100 parts by weight of the dry components in the mix are employed.
Before the carbon fiber strands are incorporated into the aqueous hardenable hydraulic cementitious matrix they are ~mpregnated with a suitable low viscosity hydro- -~
phobic resin system. Such impregnation may be effected by ~
. .
- . ~ .- .. , ...... - . . . . ;. . . .
: ~ ~ , - ~ .... . . ..
~ 3 ~ 8 10,571 simply immersing the fibers in a liquid resin system for a t~me sufficient to thoroughly wet the fibers of the strandsO
The hydrophobi~ resin ~ystem employed must be one which is both insoluble in water and capable of curing at room temperature simultaneously with the cement. While many resins are not hydrophobic, they may,nevertheless, be employed provided they become hydrophobic when a hardening agent is added thereto. The hydrophobic character of such resin sy~tem causes the expulsion of water present on the surfaces of the discrete cement particles in the vicinity of the resin which might otherwise interfere with the curlng and bonding of the resin to these particles. ~s a result, an improved bond is effected between these particles and the fibers impregnated with the resin system. The resin system also provides improved interfilament bonding and structural integrity within the strands.
An epoxy resin system is preferably employed to treat the carbon fibers before they are incorporated into the cementitious matrix because such system is easy to handle and capable o~ being cured at room temperature.
Such system comprises an epoxy resin together with a reactive epoxy resin hardener in an amount conventionally used in the art to cure epoxy resin.
The ~epoxy resins which are preferably employed to treat the carbon ibers beore they are incorporated into the cementitious matrix are the liquid polyglycidyl ethers of polyhydric phenols, particularly the liquid diglycidyl ethers of bis(4-hydroxyphenyl)methane and 10,571 3"388 bis(4-hydroxylphenyl)dimethylm~tl~an~. Such resins are usually produced by the reaction of epichlorohydr~n with a polyhydric phenol in the presence o a base.
As is well known, by varying the proport~ons of reactants employed in producing ~m epoxy resin it is possible to produce a product varying in vis~osity, molecular weight, and hydroxyl content. The resins employed in the instan~
invention are those low molecular weight, low viscosi~y, liquid epoxies in which, most preferably, the main or pre-dom~n~nt constituent is free of hydroxyl groups, e.g.,those epoxies in which the reaction product of two moles of epichlorohydrin with one mole of dIhydric phenol is the main or predominant constituent. While hydroxyl groups are usually present in most all commercially available epoxy resins, ma~y are available whi~h have a low hydroxyl ~ ;
content, and resins of thi ~ype are most preferred or use .
in this ~n~ention. Especially preferred resins o this type are the diglycidyl ethers of bis(4-hydroxyphenyl)~
methana and the diglycidyl ethers of bls(4-hydroxyphenyl~
dimethylmethane.
The ha~dening agent employed together w~th the epoxy resin must be ona which forms a hydrophobic system with ~he resin and causes it to cure at room temperature.
The room temperature cure is necessary to allow the resin to cure simultaneously with the cement, and the formation of a hydrophob:Lc system is necessary to displace water present on the surfaces of the discrete cement particles ' .. ... . ..
.. . . .~
10~571 ~ ~ Z 3 8 ~
in the vicinity of the resin which might interfere with the curing an~ bondlng of the resin to these particles.
In this manner, an improved bond is effected between these particles and the fibers which have been impregnated with the resin system. The resin system also provides improved interfilament bonding and structural integrity within the strands.
Among the epoxy resin hardeners which can be mployed in the present invention are those hardeners sold as "Ancamine"* R (manufactured by Anchor Chemical Co. U.K.
Ltd.) and "Sur-Wet"** R (manufactured by Pacific Anchor CQ., Inc.). Both of these hardeners are hydrophobic fatty amines having an amine number of from 170 to 180. When admixed with an epoxy resin, the hydrophobic character of these hardeners is imparted to the entire resin system.
In a preferred embodiment of the invention, multi-ilament strands of carbon fiber in the form of roving, yarn or tow are incorporated into the cementitious matrix ~ -in parallel rows. The fibers may be incorporated into tha cYmentitious matrix in ~his man~er by means of a mould haviag two side panels of fixed height and two end panels which are adjustable to various heights up to the height . .
of the side panels. Typically, such a mould can be prepared by slotting the inner surfaces of the side panels near their ends so that they are capable of receiving a number of end - _ *"Ancamine" is a registered trademark of Anchor Chemicals Co.,U.K.
**"Sur-Wet" is a registered trademark of Pacific Anchor Chemicals Co.
.~ .. - . ~
10,571 ~ ~ 9 ~ 3 8 ~
panels of lesser height stacked one upon another. The ~irst of such end panels is placed into position in the slots at one end of the side panels, anld a like end panel is placed into position in the slots at the other end of the side panels. A cementitious mix of cement and water is then poured into the mould to the hleigh~ of the end panels, and a continuous strand of c æbon fiber is strung back ~
and forth along the length of the mould on the surface ~ - -of the cement using a row of upright posts at each end of the mould ~o reverse direction of the strand. To assist in maintain~ng qual spacing between the horizont~l stxands of fiber, two threaded spacing bars can be situated between each set o posts and end panels at an elevation the same `
as or slightly lower than that of the end panelsO Af~er the fibers have been strung completely along the length o the mould, an additional end panel is ~nserted i~to~
the slots at each end of the mould, and the process is repeated using a second set of threaded spacing~bars and a second set of upright posts. The top surface of the 20 spacing bars should, once again, be of the same height or slightly lower than the height of the end panels.
The process, of course, may be repeated as many t~mes as necessary to bring the cement to the desired height.
Aflter the desired amount of fibers have been introduced Lnto the cement, it is allowed to set under . :~
suitable conditions to produce the carbon fiber-reinforcet cementitious structures of the invention.
. :
0,57~.
~L09Z3~
Referring now to the dr,awings, F~gure 1 illustrates a cement beam lO which has been r,einforced with strands of carbon fiber 11. The strands are disposed in the beam in two horizontal rows.
Cement beam 10 of Figurle 1 is manufactured in one of the compartments of mould 12 of Figures 2 and 3.
The mould has side panels 13 and two divider panels 14 and 15 spaced equidistant between the side panels which divide the mould into three compartments. Side panels 13 contain slots 16 near each of their ends, and dlvider panels 14 and 15 contain slots 17 and 18 near each of their ends, to receive end panels 19. Side panels 13 and divider panels 14 and 15 are of equal height while end panels 19 are of a height which is only a fraction of that of the side panels and divider panels. Spacing bars ~
20 are positioned between end panels 19 and stands 21 ~ -containing upright posts 22 which are positioned equidistant fr~m each other in the stands. Spacing bars 20 are threaded -;
across their lengths and their top surface is slightly lower than the height of end paneIs 19.
The mould is filled with cement to the level of end panels 19. A continuous strand of carbon fiber 23 is ~;
~ .
then drawn from spool 24 through bath 25 containing hydro-phobic resin system Z6. The bath also contains a bar 27 under which the carbon fiber strand 23 is passed to ensure complete immersion in hydrophobic resin system 26. After passing through the bath, carbon fiber strand 23 is tied to the first post at one end of one of the stands 21 and _ 9 _ 10,571 ~Og~3~8 then strung back and forth along the length of the mould on the surfac2 of the cement using posts 22 at each end of the mould to reverse direction of the! strand and the threads of spacing bars 20 to assist in maintaining equal spacing between horizontal strands, in the manner shown in Figure 2.
After the fiber has been st~ung completely across ~
the width of the mould, it is secured to the last remaining - `
post in stands 21, an additional end panel is inserted into the slots at each end of the mould, and the process is re~
peated using a second set of spacing bars 28 and a second `
set of upright posts 30 contained in stands 2g. Spacing -bars 28, like spacing bars 207 are threaded across their lengths and their top surface is the same height or slightly lower than that of the second set of end panels. me process, of course, may be repeated as many times as necessary to bring the cement level to the desired height.
After the desired amount of fibers have been intro~
duced into the cement, it is allowed to set under suitable conditions to produce the carbon ibe~-reinforced cementitious struc~ures of ~he invention.
The following example is set forth for purposes o illustration ~o that those skilled in the art may better understand this invention. It should be understood~that it ;~
is exemplary only, and should not be construed as limiting this invention in any manne=. ~ ~;
~D?LE 1 A three compartment collapsible wooden mould was employed to produce three cement beams reinforced with strands 10,571 ~ ~ 9 2 3 ~ ~
of carbon fiber. The mould had t:wo side panels and two divider panels spaced equidistant between the side panels which divided the mould into three compartments. The side panels and divider -panels were 2 inches high and slotted near their ends so as to be capable of receiving a number o end panels of le~ser height stacked one upon another. One end panel 1.4 inches high was placed into position in the slots at one end of the side panels and divider panels, and a like end panel was placed into position in the slots at the other end of the side panels and divider panels. The mould was now ready for use.
Each compartment of the assembled mould was then filled with a cementitious mix to a level equal to the height of the end panels. A small brush was employed dur~ng the early stages of filling to compact the mix into the edges and corners o~ each compartment. After the cementiti~us mix had reached the desired level, a straight edge was used to level and smooth the top surface. Finally, the mould was vibrated for five minutes on a vibration table.
The cementitious mix ~mployed contained lOO parts by weigh~ of cement and 30 parts by weight of water which had been thoroughly mixed in a power-operated mixer using a dough hook attachment. The cement ~mployed was a Portland cement con~onming to British Standard 12.
A slngle ply carbon fiber yarn* which had been passed *The yarn employed was "Thorneli' 300, a single ply, 1717 denier, carbon fiber yarn containing 3000 filaments -~`
wherein the filaments are characterized by an average Young's mod~lus of 34 x 10~ pSL and an a~erage ~ensile streng~h of 360 x 103 psi. "Thornel" is a registered trademark of Union Carbide Corpora~ion.
.. .. . .. .
10,571 through a liquid hydrophobic epo:Ky resin system** was then tied to the end nail of a row of upright nails positioned parallel to and just beyond one end panel of ~he mould. A like row ~ .
of upright nails was positioned ;parallel to and just beyond the other end of the mould. Fxom the fir~t end nail .the carbon ~ ~-fiber yarn was then strung on thle surface of the cement along the length of the mould and around the end nail of thQ row o upright nails at the oth~r end of the mould, a~d then back and forth around each of the nails at opposite ends o~ ~he mould until the yarn had been strung completely across the ~:
entire width of each compartment. The yarn wa~ at all times stretched jus~ tight enough to take up any slack. The ree end of the yarn was then secured to the last remaining nail.
To assist in mainta ming equal spacing between the horizontal ~ , strands of fiber, two threaded spacing bars con~aining 20 threads per inch were positioned between each se~:of nails . .
and end panels so that ~heir ~op surfaces were a~ an eleva-tion slightly lower than that of the end panels. The carbon fiber yarn was passed over the e spacing bars, and betwee~
every other t~r.ead ~hereof, before being turned around the nails situated at the ends of the mould. In this manner, -~
the entire widt~ of each compartment was traversed with a .. . ~
**The epoxy resin syst~m employed was composed of o~e hundred (100) parts by weight of a commercially available ~:
liquid epoxy resi~ produced by the reaction o epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane (Epikote 828, manufactured ~ .
by Shell ChPmicals U.K. Ltd.) and one hundred (100) parts by weight of '~Ancamine" R, a hydrophobic fatty amine epoxy resin hardening agent having an amine number of frnm 170 to 180.
The system was both insoluble in water and capable of curing at ro~m temperature simultaneously with the cemen~
.,"", -~0 9 ~ 3 ~ ~
layer of fiber yarn running along its length and spaced 0.1 inch apart.
A second end panel 0.5 inch high was then inserted into the slots at each end of the mould and each compQrtment of the mould was filled with a sec:ond layer of cement to the height of the second end panels. To ensure good contact with the fibers, and to provide a good bond to the previous cement layer~ the first portion of the cement was brushed onto the top of the fibers. The second cement layer was then consol-idat~d by tamplng with a straight edge rather than by vibrationso as not to distort the fibers or the first layer of cement which might have started to set.
The resin bath was then emptied and refilled with a freshly mixed resin system, and a seeond layer of fibers were laid in place in the same manner as the first using a second set of spacing bars and a second set of nails. The second set of spacing bars, li~e the first, were threaded ~;
across their 10ngths t20 threads per inch) and their top surfaces were at an elevation slightly lower than that of ~ the second set of end panels.
Final]y, a third end panel 0.1 inch high was installed into the slots at each end of tha mould and each ~`
compartment was again filled with a third and final layer of cement to the height of the end panels in the same manner . .
as before. The three spec~mens, which were 25" x 3" x 2" `~
in size, were allowed to set in the mould for 18-20 hours, after which they were removed from the mould and further ~-~
cured for 28 days in water at room tempexature. At the :`
10,571 :10923~8 end of the 28-day cure period~ the specimens were removed from the water and tested for flexural strength by subjecting them to three-point bending over a 1011 span in a 12,000 lb.
A~ery universal test machine. The test beams were supported at both ends by support rollers 0.75 inch in diameter with the fibers on the tension side (supported by the rollers), and pressure was applied at the center of the sample by means of a loading roller 1 inch in diameter. Loading pressure was increased at the rate of approximately 1000 psi./
min. until the beam foiled. Each beam was tested wit~in 30 minutes of removal from the water in which it was cured.
The beams had a mean flexural strength of 2210 psi.
The mean flexural strength of three beams prepared ~ -in like manner but without carbon fiber reinforcement was 1390 psi. Beams prepared in like manner with carbon fIber ~ .
: .
reinforcement, but without pre-treating the fibers with a :.~
hydrophobic resin, likewise had a mean flexural strength of only 1390 psi. ~
, ~ - .. -- ' ~: .
This invention relates to an improved method of incorporating multifilament strands of carbon fibers i~to an aqueous hardenable hydraulic cementltious matrix which can be set to produce a carbon fiber-reinforced cementitious structure having improved flexural strength. More partic-ularly, this invention relates to the preparation of a carbon fiber-reinforced structure having improved flexural strength from an aqueous hardenable hydraulic c~men i~ious matrix containing multifilament strands of carbon fibers whlch have been treated with a hydrophobic resin system prior to being incorporated into the cementitious matrix.
Multifilament strands of carbon fibars have hereto-fore been employed to reinfor~e cement in an efort to increase the ~lexural strength of such cement. However, because of poor bonding between the filaments of the strands, a~d between -~
the filaments of such strands and the cement, little or no improv~ment in the strength of the cement was attained by the addition of these fiber strands.
SUMMARY~ VT~
.'~ ~ ~ ' ';' . .
- In accordance with the~ present invention it has now been discovered that a carbo~ fiber-reinforced cementi-tious structure having improved flexural strength can be prepared from an aqueous hardenable hydraulic cementitious matrix to which have been added multifilament strands of carbon fibers which ha~e been treated with a hydrophobic 10,571 ~()9Z3~8 resin system. The fiber-reinforced structures prepared in this manner have been found to exhibit increases in flexural strength in excess of fifty percent (50/0) over the flexural strength of structures prepared in like manner from fiber strands which have not been treated with a hydrophobic resin system.
BRIEF DESCRIPTION OF, THE DRAWINGS
Figure 1 is an isometric view showing the end portion o~ a cement beam whioh has been reinforced with multifilament strands of carbon fibers arranged in two horizontal rows.
Figure 2 is a top plane view of a mould suitable for the fabrication of the carbon fiber-reinforced cement beams of Figure 1. The view shows the first horizontal row of fiber strands being laid in th~ mould.
Figure 3 is a side schematic view of one of the compartments of the mould depicted in Figure 2 after two :~
horizontal rows of fiber strands have been laid.
DETAILED DESCRIPTION OF THE INVENTION
.. .
Any hydraulic cement can be employed in the c~ment composition employed in the inventionO Aggregate filler mate-rial may be employed together with the hydraulic cement in :~
amounts convent:ionally employed. If a filler is employed, how- -e~er9 it is preferably a fine non-abrasive aggregate material, such as fly ash, and does not exc~ed twenty percent ~ ;
of the total weight of the cement and aggregate material. ~ :
~ .
10,571 ~g2388 H~gh modulus, high strength carb~n fibers suitable for use in the instant invention can be prepared as described in U. S. Patents 3,454,362, 3,41'2~062 and 4,005,133. The term "carbon" as used herein is intended to include graphitlc ant non-graphitic ibers.
The amount of fibers e~ployed is such as to obtain the desired strength characteristics, typically from 1 part by weight to 6 parts by weight of fibers per 100 parts by weight of the "dry components" of the cementitious c~mposi-tion. By "dry components" in this contex~ is meant the cement and other solid aggregate filler material (if present) which together make up the cementitious composition, but not including the carbon fiber itself. Most usually, the fibers are present in an amount of from 2~5 parts by weight to 5 parts by weight per 100 par~s by weight of the dry materials.
The water, o course, must be employed in an æmount suf~icient to hydrate the cement. In order to produce ~
cementitious structures having max~mum strength, however, ~ ~ -the amount of water sho~ld be held to a mi~imum consistent ~`
with this purpose. Typically~ from about 25 parts by weight to about 55 parts by weight, preferably ~rom about 30 parts by weight to 45 parts by weight, of water per 100 parts by weight of the dry components in the mix are employed.
Before the carbon fiber strands are incorporated into the aqueous hardenable hydraulic cementitious matrix they are ~mpregnated with a suitable low viscosity hydro- -~
phobic resin system. Such impregnation may be effected by ~
. .
- . ~ .- .. , ...... - . . . . ;. . . .
: ~ ~ , - ~ .... . . ..
~ 3 ~ 8 10,571 simply immersing the fibers in a liquid resin system for a t~me sufficient to thoroughly wet the fibers of the strandsO
The hydrophobi~ resin ~ystem employed must be one which is both insoluble in water and capable of curing at room temperature simultaneously with the cement. While many resins are not hydrophobic, they may,nevertheless, be employed provided they become hydrophobic when a hardening agent is added thereto. The hydrophobic character of such resin sy~tem causes the expulsion of water present on the surfaces of the discrete cement particles in the vicinity of the resin which might otherwise interfere with the curlng and bonding of the resin to these particles. ~s a result, an improved bond is effected between these particles and the fibers impregnated with the resin system. The resin system also provides improved interfilament bonding and structural integrity within the strands.
An epoxy resin system is preferably employed to treat the carbon fibers before they are incorporated into the cementitious matrix because such system is easy to handle and capable o~ being cured at room temperature.
Such system comprises an epoxy resin together with a reactive epoxy resin hardener in an amount conventionally used in the art to cure epoxy resin.
The ~epoxy resins which are preferably employed to treat the carbon ibers beore they are incorporated into the cementitious matrix are the liquid polyglycidyl ethers of polyhydric phenols, particularly the liquid diglycidyl ethers of bis(4-hydroxyphenyl)methane and 10,571 3"388 bis(4-hydroxylphenyl)dimethylm~tl~an~. Such resins are usually produced by the reaction of epichlorohydr~n with a polyhydric phenol in the presence o a base.
As is well known, by varying the proport~ons of reactants employed in producing ~m epoxy resin it is possible to produce a product varying in vis~osity, molecular weight, and hydroxyl content. The resins employed in the instan~
invention are those low molecular weight, low viscosi~y, liquid epoxies in which, most preferably, the main or pre-dom~n~nt constituent is free of hydroxyl groups, e.g.,those epoxies in which the reaction product of two moles of epichlorohydrin with one mole of dIhydric phenol is the main or predominant constituent. While hydroxyl groups are usually present in most all commercially available epoxy resins, ma~y are available whi~h have a low hydroxyl ~ ;
content, and resins of thi ~ype are most preferred or use .
in this ~n~ention. Especially preferred resins o this type are the diglycidyl ethers of bis(4-hydroxyphenyl)~
methana and the diglycidyl ethers of bls(4-hydroxyphenyl~
dimethylmethane.
The ha~dening agent employed together w~th the epoxy resin must be ona which forms a hydrophobic system with ~he resin and causes it to cure at room temperature.
The room temperature cure is necessary to allow the resin to cure simultaneously with the cement, and the formation of a hydrophob:Lc system is necessary to displace water present on the surfaces of the discrete cement particles ' .. ... . ..
.. . . .~
10~571 ~ ~ Z 3 8 ~
in the vicinity of the resin which might interfere with the curing an~ bondlng of the resin to these particles.
In this manner, an improved bond is effected between these particles and the fibers which have been impregnated with the resin system. The resin system also provides improved interfilament bonding and structural integrity within the strands.
Among the epoxy resin hardeners which can be mployed in the present invention are those hardeners sold as "Ancamine"* R (manufactured by Anchor Chemical Co. U.K.
Ltd.) and "Sur-Wet"** R (manufactured by Pacific Anchor CQ., Inc.). Both of these hardeners are hydrophobic fatty amines having an amine number of from 170 to 180. When admixed with an epoxy resin, the hydrophobic character of these hardeners is imparted to the entire resin system.
In a preferred embodiment of the invention, multi-ilament strands of carbon fiber in the form of roving, yarn or tow are incorporated into the cementitious matrix ~ -in parallel rows. The fibers may be incorporated into tha cYmentitious matrix in ~his man~er by means of a mould haviag two side panels of fixed height and two end panels which are adjustable to various heights up to the height . .
of the side panels. Typically, such a mould can be prepared by slotting the inner surfaces of the side panels near their ends so that they are capable of receiving a number of end - _ *"Ancamine" is a registered trademark of Anchor Chemicals Co.,U.K.
**"Sur-Wet" is a registered trademark of Pacific Anchor Chemicals Co.
.~ .. - . ~
10,571 ~ ~ 9 ~ 3 8 ~
panels of lesser height stacked one upon another. The ~irst of such end panels is placed into position in the slots at one end of the side panels, anld a like end panel is placed into position in the slots at the other end of the side panels. A cementitious mix of cement and water is then poured into the mould to the hleigh~ of the end panels, and a continuous strand of c æbon fiber is strung back ~
and forth along the length of the mould on the surface ~ - -of the cement using a row of upright posts at each end of the mould ~o reverse direction of the strand. To assist in maintain~ng qual spacing between the horizont~l stxands of fiber, two threaded spacing bars can be situated between each set o posts and end panels at an elevation the same `
as or slightly lower than that of the end panelsO Af~er the fibers have been strung completely along the length o the mould, an additional end panel is ~nserted i~to~
the slots at each end of the mould, and the process is repeated using a second set of threaded spacing~bars and a second set of upright posts. The top surface of the 20 spacing bars should, once again, be of the same height or slightly lower than the height of the end panels.
The process, of course, may be repeated as many t~mes as necessary to bring the cement to the desired height.
Aflter the desired amount of fibers have been introduced Lnto the cement, it is allowed to set under . :~
suitable conditions to produce the carbon fiber-reinforcet cementitious structures of the invention.
. :
0,57~.
~L09Z3~
Referring now to the dr,awings, F~gure 1 illustrates a cement beam lO which has been r,einforced with strands of carbon fiber 11. The strands are disposed in the beam in two horizontal rows.
Cement beam 10 of Figurle 1 is manufactured in one of the compartments of mould 12 of Figures 2 and 3.
The mould has side panels 13 and two divider panels 14 and 15 spaced equidistant between the side panels which divide the mould into three compartments. Side panels 13 contain slots 16 near each of their ends, and dlvider panels 14 and 15 contain slots 17 and 18 near each of their ends, to receive end panels 19. Side panels 13 and divider panels 14 and 15 are of equal height while end panels 19 are of a height which is only a fraction of that of the side panels and divider panels. Spacing bars ~
20 are positioned between end panels 19 and stands 21 ~ -containing upright posts 22 which are positioned equidistant fr~m each other in the stands. Spacing bars 20 are threaded -;
across their lengths and their top surface is slightly lower than the height of end paneIs 19.
The mould is filled with cement to the level of end panels 19. A continuous strand of carbon fiber 23 is ~;
~ .
then drawn from spool 24 through bath 25 containing hydro-phobic resin system Z6. The bath also contains a bar 27 under which the carbon fiber strand 23 is passed to ensure complete immersion in hydrophobic resin system 26. After passing through the bath, carbon fiber strand 23 is tied to the first post at one end of one of the stands 21 and _ 9 _ 10,571 ~Og~3~8 then strung back and forth along the length of the mould on the surfac2 of the cement using posts 22 at each end of the mould to reverse direction of the! strand and the threads of spacing bars 20 to assist in maintaining equal spacing between horizontal strands, in the manner shown in Figure 2.
After the fiber has been st~ung completely across ~
the width of the mould, it is secured to the last remaining - `
post in stands 21, an additional end panel is inserted into the slots at each end of the mould, and the process is re~
peated using a second set of spacing bars 28 and a second `
set of upright posts 30 contained in stands 2g. Spacing -bars 28, like spacing bars 207 are threaded across their lengths and their top surface is the same height or slightly lower than that of the second set of end panels. me process, of course, may be repeated as many times as necessary to bring the cement level to the desired height.
After the desired amount of fibers have been intro~
duced into the cement, it is allowed to set under suitable conditions to produce the carbon ibe~-reinforced cementitious struc~ures of ~he invention.
The following example is set forth for purposes o illustration ~o that those skilled in the art may better understand this invention. It should be understood~that it ;~
is exemplary only, and should not be construed as limiting this invention in any manne=. ~ ~;
~D?LE 1 A three compartment collapsible wooden mould was employed to produce three cement beams reinforced with strands 10,571 ~ ~ 9 2 3 ~ ~
of carbon fiber. The mould had t:wo side panels and two divider panels spaced equidistant between the side panels which divided the mould into three compartments. The side panels and divider -panels were 2 inches high and slotted near their ends so as to be capable of receiving a number o end panels of le~ser height stacked one upon another. One end panel 1.4 inches high was placed into position in the slots at one end of the side panels and divider panels, and a like end panel was placed into position in the slots at the other end of the side panels and divider panels. The mould was now ready for use.
Each compartment of the assembled mould was then filled with a cementitious mix to a level equal to the height of the end panels. A small brush was employed dur~ng the early stages of filling to compact the mix into the edges and corners o~ each compartment. After the cementiti~us mix had reached the desired level, a straight edge was used to level and smooth the top surface. Finally, the mould was vibrated for five minutes on a vibration table.
The cementitious mix ~mployed contained lOO parts by weigh~ of cement and 30 parts by weight of water which had been thoroughly mixed in a power-operated mixer using a dough hook attachment. The cement ~mployed was a Portland cement con~onming to British Standard 12.
A slngle ply carbon fiber yarn* which had been passed *The yarn employed was "Thorneli' 300, a single ply, 1717 denier, carbon fiber yarn containing 3000 filaments -~`
wherein the filaments are characterized by an average Young's mod~lus of 34 x 10~ pSL and an a~erage ~ensile streng~h of 360 x 103 psi. "Thornel" is a registered trademark of Union Carbide Corpora~ion.
.. .. . .. .
10,571 through a liquid hydrophobic epo:Ky resin system** was then tied to the end nail of a row of upright nails positioned parallel to and just beyond one end panel of ~he mould. A like row ~ .
of upright nails was positioned ;parallel to and just beyond the other end of the mould. Fxom the fir~t end nail .the carbon ~ ~-fiber yarn was then strung on thle surface of the cement along the length of the mould and around the end nail of thQ row o upright nails at the oth~r end of the mould, a~d then back and forth around each of the nails at opposite ends o~ ~he mould until the yarn had been strung completely across the ~:
entire width of each compartment. The yarn wa~ at all times stretched jus~ tight enough to take up any slack. The ree end of the yarn was then secured to the last remaining nail.
To assist in mainta ming equal spacing between the horizontal ~ , strands of fiber, two threaded spacing bars con~aining 20 threads per inch were positioned between each se~:of nails . .
and end panels so that ~heir ~op surfaces were a~ an eleva-tion slightly lower than that of the end panels. The carbon fiber yarn was passed over the e spacing bars, and betwee~
every other t~r.ead ~hereof, before being turned around the nails situated at the ends of the mould. In this manner, -~
the entire widt~ of each compartment was traversed with a .. . ~
**The epoxy resin syst~m employed was composed of o~e hundred (100) parts by weight of a commercially available ~:
liquid epoxy resi~ produced by the reaction o epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane (Epikote 828, manufactured ~ .
by Shell ChPmicals U.K. Ltd.) and one hundred (100) parts by weight of '~Ancamine" R, a hydrophobic fatty amine epoxy resin hardening agent having an amine number of frnm 170 to 180.
The system was both insoluble in water and capable of curing at ro~m temperature simultaneously with the cemen~
.,"", -~0 9 ~ 3 ~ ~
layer of fiber yarn running along its length and spaced 0.1 inch apart.
A second end panel 0.5 inch high was then inserted into the slots at each end of the mould and each compQrtment of the mould was filled with a sec:ond layer of cement to the height of the second end panels. To ensure good contact with the fibers, and to provide a good bond to the previous cement layer~ the first portion of the cement was brushed onto the top of the fibers. The second cement layer was then consol-idat~d by tamplng with a straight edge rather than by vibrationso as not to distort the fibers or the first layer of cement which might have started to set.
The resin bath was then emptied and refilled with a freshly mixed resin system, and a seeond layer of fibers were laid in place in the same manner as the first using a second set of spacing bars and a second set of nails. The second set of spacing bars, li~e the first, were threaded ~;
across their 10ngths t20 threads per inch) and their top surfaces were at an elevation slightly lower than that of ~ the second set of end panels.
Final]y, a third end panel 0.1 inch high was installed into the slots at each end of tha mould and each ~`
compartment was again filled with a third and final layer of cement to the height of the end panels in the same manner . .
as before. The three spec~mens, which were 25" x 3" x 2" `~
in size, were allowed to set in the mould for 18-20 hours, after which they were removed from the mould and further ~-~
cured for 28 days in water at room tempexature. At the :`
10,571 :10923~8 end of the 28-day cure period~ the specimens were removed from the water and tested for flexural strength by subjecting them to three-point bending over a 1011 span in a 12,000 lb.
A~ery universal test machine. The test beams were supported at both ends by support rollers 0.75 inch in diameter with the fibers on the tension side (supported by the rollers), and pressure was applied at the center of the sample by means of a loading roller 1 inch in diameter. Loading pressure was increased at the rate of approximately 1000 psi./
min. until the beam foiled. Each beam was tested wit~in 30 minutes of removal from the water in which it was cured.
The beams had a mean flexural strength of 2210 psi.
The mean flexural strength of three beams prepared ~ -in like manner but without carbon fiber reinforcement was 1390 psi. Beams prepared in like manner with carbon fIber ~ .
: .
reinforcement, but without pre-treating the fibers with a :.~
hydrophobic resin, likewise had a mean flexural strength of only 1390 psi. ~
, ~ - .. -- ' ~: .
Claims (12)
1. A reinforced structure having improved flexural strength comprising a cementitious structure reinforced with multifilament strands of carbon fibers which have been impreg-nated with a liquid hydrophobic resin system prior to being incorporated into the cementitious matrix, which hydrophobic resin system has been cured simultaneously with the cementi-tious matrix and which serves to bond the fibers to each other and to the cement particles.
2. A reinforced structure as in claim 1 wherein the hydrophobic resin system is an epoxy resin system comprised of an epoxy resin and a reactive epoxy resin hardener.
3. A reinforced structure as in claim 2 wherein the epoxy resin hardener is a hydrophobic fatty amine.
4. A reinforced structure as in claim 3 wherein the hydrophobic fatty amine has an amine number of 170 to 180.
5. A reinforced structure as in claim 1 wherein the strands of carbon fibers are arranged in parallel rows.
6. A reinforced structure as in claim 5 wherein the hydrophobic resin system is an epoxy resin system comprised of an epoxy resin and a reactive epoxy resin hardener.
7. A reinforced structure as in claim 6 wherein the epoxy resin hardener is a hydrophobic fatty amine.
8. A reinforced structure as in claim 7 wherein the hydrophobic fatty amine has an amine number of 170 to 180.
9. A process for producing a carbon fiber-rein-forced cementitious structure having improved flexural strength which comprises filling a mould with a cementitious mix to a desired level, impregnating a continuous strand of carbon fiber with a liquid hydrophobic resin system and stringing the strand back and forth along a length of the mould on the surface of the cement, adding a second layer of the cementitious mix to the first layer, and simultaneously curing the hydrophobic resin and cementitious mix to produce said carbon fiber-reinforced cementitious structure.
10. A process as in claim 9 wherein the hydrophobic resin system is an epoxy resin system comprised of an epoxy resin and a reactive epoxy resin hardener.
11. A process as in claim 10 wherein the epoxy resin hardener is a hydrophobic fatty amine.
12. A process as in claim 11 wherein the hydrophobic fatty amine has an amine number of 170 to 180.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86562777A | 1977-12-29 | 1977-12-29 | |
| US865,627 | 1977-12-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1092388A true CA1092388A (en) | 1980-12-30 |
Family
ID=25345916
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA318,790A Expired CA1092388A (en) | 1977-12-29 | 1978-12-28 | Method of incorporating multifilament strands of carbon fibers into cement to produce reinforced structures having improved flexural strengths |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5819620B2 (en) |
| CA (1) | CA1092388A (en) |
| DE (1) | DE2856079C2 (en) |
| GB (1) | GB2011520B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5419965A (en) * | 1990-06-01 | 1995-05-30 | Domecrete Ltd. | Reinforcing element with slot and optional anchoring means and reinforced material incorporating same |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5945979A (en) * | 1982-09-03 | 1984-03-15 | 鹿島建設株式会社 | Tile mounted concrete panel |
| JPH0610096B2 (en) * | 1983-04-23 | 1994-02-09 | 株式会社ノリタケカンパニーリミテド | Method for producing gypsum powder containing carbon fiber for ceramics molding |
| EP0242793B1 (en) * | 1986-04-23 | 1993-03-03 | Mitsubishi Kasei Corporation | Cement reinforcing fiber |
| JPS62260755A (en) * | 1986-05-07 | 1987-11-13 | 三菱石油株式会社 | Manufacture of carbon fiber reinforced cement product |
| US7455727B2 (en) | 2001-04-09 | 2008-11-25 | James Hardie International Finance B.V. | Integral water resistant fibre-cement |
| USD792829S1 (en) | 2014-07-23 | 2017-07-25 | Dzinesquare Inc. | Vehicle wheel |
| EP3091135A1 (en) * | 2015-05-04 | 2016-11-09 | Evonik Degussa GmbH | Reinforcing rod, method for production and use |
| CN107966343B (en) * | 2017-11-30 | 2023-11-07 | 沈阳工业大学 | Detachable die for PVA fiber bundle and cement-based material adhesion test |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1244984A (en) * | 1968-05-07 | 1971-09-02 | Mini Of Aviat Supply | Improvements in or relating to flexible composite materials and a process for their manufacture |
| US3806489A (en) * | 1973-06-04 | 1974-04-23 | Rhone Progil | Composite materials having an improved resilience |
| US3993707A (en) * | 1973-10-23 | 1976-11-23 | Pacific Vegetable Oil Corporation | Composition for coating wet surfaces or surfaces immersed in water |
| JPS5177620A (en) * | 1974-12-27 | 1976-07-06 | Kogyo Gijutsuin | SETSUKO FUKUGOZ AIRYO |
| JPS5247019A (en) * | 1975-10-11 | 1977-04-14 | Denki Kagaku Kogyo Kk | Reinforcing method of inorganic molded form |
| JPS5249235A (en) * | 1975-10-18 | 1977-04-20 | Kubota Ltd | Production method of fiber reinforced cement product |
-
1978
- 1978-12-23 DE DE19782856079 patent/DE2856079C2/en not_active Expired
- 1978-12-28 JP JP53161293A patent/JPS5819620B2/en not_active Expired
- 1978-12-28 GB GB7850158A patent/GB2011520B/en not_active Expired
- 1978-12-28 CA CA318,790A patent/CA1092388A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5419965A (en) * | 1990-06-01 | 1995-05-30 | Domecrete Ltd. | Reinforcing element with slot and optional anchoring means and reinforced material incorporating same |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2856079C2 (en) | 1982-12-30 |
| GB2011520B (en) | 1982-03-31 |
| JPS5496527A (en) | 1979-07-31 |
| JPS5819620B2 (en) | 1983-04-19 |
| GB2011520A (en) | 1979-07-11 |
| DE2856079A1 (en) | 1979-07-05 |
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