Structural members

Improved structural members including solid and hollow core beams, poles, columns and enclosure structures formed of a cement-based slurry infiltrated fiber composite material. The improved structural members are produced by first placing a plurality of individual short fibers or fiber mats of organic or inorganic materials into a form to create a bed of fibers substantially filling the form and having a predetermined fiber volume density and then adding a cement-based slurry mixture into the form to completely infiltrate the spaces between the fibers. Existing structural members may be retrofitted with jackets of the cement-based slurry infiltrated fiber composite material. The cement-based slurry mixture includes a composition of Portland cement or blended cement, fly ash, water, a high-range water reducer (superplasticizer), and may also include fine grain sand, ground granulated blast-furnace slag, chemical admixtures, and other additives. Due to its fiber volume density and method of manufacture, the resulting structure has greater strength, less maintenance, and less cracking and deterioration than wood, steel, or conventional reinforced concrete and pre-stressed concrete structures, and a much higher bending capacity approximating that of structural steel.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to structural members, and more 
particularly to improved solid or hollow core structural members formed of 
a cement-based slurry infiltrated fiber composite material wherein the 
walls of the structural member contains a mass of short fibers or fiber 
mats of organic or inorganic materials having a predetermined fiber volume 
density completely infiltrated in a cement-based matrix mixture. 
2. Brief Description of the Prior Art 
Structural beams, columns, and poles, such as; railroad ties for supporting 
steel railroad tracks, telephone and utility poles, bridge or highway 
overpass support beams and columns, pilings for building foundations and 
piers, and culverts, are usually constructed of wood, reinforced concrete, 
pre-stressed concrete, metal, or fiberglass. 
Environmental enclosure structures such as: secondary containment vaults 
for hazardous materials; underground storage vaults; controlled 
environment vaults for housing communication security vaults for storing 
volatile explosives, nuclear weapons, test devices, weapons components, 
and radioactive wastes, are usually fabricated using conventional 
reinforced and pre-stressed concrete. 
Since the early 1800's, railroad ties and telegraph poles have been made 
from wood. In the early 1970's, the precast pre-stressed concrete tie was 
introduced commercially by Costain Concrete Tie Company in Alberta, 
Canada, and shortly thereafter in the United States. In 1986, the company 
relocated to Spokane, Wash. and changed their name to CXT, Inc. Concrete 
ties have been gaining popularity among railroad companies since their 
inception in 1971. Also in the early 1970's, concrete telephone and 
utility poles were commercialized by Centrecon (American Pole Products) of 
Evererett, Wash. 
Demand for wood-alternative structural members has steadily increased due 
to rising timber prices and environmental restructions. With the recent 
(1993) cut-back in federal timber sales in the Northwest, the use of wood 
as a structural material will drop substantially in the nineties. Timber 
prices are projected to rise 35% in 1993 and an additional 10% in 1994. 
Conventional structural members formed of wood or concrete are subject to 
cracking and deterioration because of environmental changes, such as 
freeze-thaw and/or moisture-heat cycles. These same conditions cause steel 
structural members to rust or corrode. In the case of telephone and 
utility poles, wind conditions will adversely affect the wood, concrete or 
steel structures because they are subjected to vibration and bending 
movements (and earthquakes in some areas) which cause cracking, spalling, 
and deterioration. In the case of railroad ties, abrasion occurs on the 
bottom side of the ties due to particles of hard material, such as 
locomotive traction sand, which is 10 times the hardness of hydrated 
cement. This condition prematurely wears out the concrete ties. 
Also, concrete railroad ties and most other concrete structures have an 
alkali-aggregate reaction which results from certain types of silica in 
the aggregate reacting with alkalis in the cement to form a gel. The gel 
absorbs water,from the air or ground and swells, thus causing severe 
crazing, followed by expansion of the concrete and severe cracking. In 
pre-stressed concrete structures, the result is loss of bond and, hence, 
pre-stress, which leads to structural failure. 
Earthquakes can cause failure of pre-stressed concrete support beams and 
columns. For example, in the San Francisco freeway disaster in 1990 the 
bridge and highway overpass support beams and columns collapsed due to 
very low flexural properties, and resulted in the loss of life and 
millions of dollars in damages. 
In the past, materials such as petroleum products, chemicals, and hazardous 
materials have been stored in large metal or fiberglass tanks which are 
buried underground. Most of these "underground fuel storage tanks" (UFST) 
are prone to leakage due to being subjected to the hydrostatic forces of 
ground water, physical stresses associated with ground movement, and the 
corrosive action of soil environments. Great damage to the environment and 
personal injury often results when the leaked materials enter the soil or 
ground water. The United States Environmental Protection Agency. (EPA) has 
recently adopted regulations for Underground Fuel Storage Tanks (UFST) in 
response to the growing awareness of the damage caused by releases from 
the UFST's. 
One method to comply with the EPA regulations is to place the fuel storage 
tank inside a buried "secondary containment vault" which allows the tank 
to be monitored for leakage and, in the event of a leak, will contain the 
leak to prevent the material from entering the soil or ground water. The 
secondary containment vault also isolates the fuel tank from soil and 
hydrostatic pressures and the corrosive action of many soils. Most 
underground secondary containment vaults currently available are 
fabricated using conventional reinforced and pre-stressed concrete. To 
meet the structural design requirements for resisting hydrostatic loads 
and soil pressures, the walls of the vaults are generally from 8 to 10 
inches thick. 
Other structures, such as controlled environment vaults and high security 
vaults are usually fabricated using conventional reinforced and 
pre-stressed concrete. The controlled environment vault is a box-like 
structure used for housing communication equipment, such as telephone, 
computer, or surveillance equipment, etc., and may contain temperature 
control equipment, dehumidifiers, fresh air blowers, environment monitors 
and alarms, and electrical control panels and outlets, etc. to provide a 
controlled environment. The controlled environment vaults may be partially 
buried with an entry hatch above ground. Controlled environment vaults 
range in size from about 17'-25' in length, 7'-12' in height, and 10'-12' 
in width. A controlled environment vault of conventional steel reinforced 
concrete in the smaller size has a weight of 70,000 lbs, and the larger 
size weighs about 140,000 lbs, with a concrete strength of 5,000 psi. The 
high security vault is a box-like structure used for storing volatile 
explosives, nuclear weapons, test devices, weapons components, and 
radioactive wastes, where high strength and security is a factor. 
Utility Vault Company, Inc., of Chandler, Ariz. manufactures secondary 
containment vaults, and controlled environment vaults which are 
constructed of conventional steel reinforced concrete. 
There are several patents which disclose various fiber reinforced concrete 
structures. 
U.S. Pat. No. 3,429,094 to Romualdi discloses a two-phase concrete and 
steel material comprising closely spaced short wire segments uniformly 
distributed randomly in concrete wherein the average spacing between wire 
segments is not greater than 0.5 inches. 
Fleischer et al, U.S. Pat. No. 4,257,912 discloses a system for fixed 
storage of spent nuclear fuel having activated fission products contained 
within a metallic fuel rod housing which comprises a uniform concrete 
contiguously and completely surrounding the metallic housing which has 
metallic fibers to enhance thermal conductivity and polymers to enhance 
impermeability for convectively cooling the exterior surface of the 
concrete. 
Rotondo et al, U.S. Pat. No. 4,404,786 discloses a method and apparatus for 
making reinforced concrete products including hollow poles wherein arrays 
of reinforcing rods are distributed and embedded automatically during the 
introduction of concrete into a form. 
Lankard et al, U.S. Pat. No. 4,559,881 discloses a burglar resistant 
security vault formed of prefabricated steel fiber reinforced concrete 
modular panels wherein Portland Cement, fly ash, fine aggregate, gravel 
and water are mixed for an extraordinarily long period of time and they 
remain a mass of crumbly, damp, powder and aggregate until the 
superplasticizer admixture is added, at which time the mixture reaches a 
fluid state. Steel fibers are then added to the mixture and mixing 
continues until the mixture including the steel fibers is poured into a 
mold cavity. 
Double et al, U.S. Pat. No. 4,780,141 discloses a cementious composite 
material containing metal fiber which particularly formulated to have high 
strength and a high degree of vacuum integrity at high temperatures. The 
composite comprises a high strength cement matrix and a filler component 
comprising a metal fiber having a length of about 0.05 mm. to about 5 mm. 
(about 0.02" to about 0.20"). The metal fiber filler is mixed with the 
cement matrix at a high vacuum to minimize air bubbles and then the liquid 
mixture (including metal fiber) is poured into the mold. 
Heintzelman et al, U.S. Pat. No. 5,030,033 discloses a conventional 
concrete underground storage vault comprised of a plurality of concrete 
sections sealingly secured together with grout keys and joint wrap. A 
fluid and material resistant (epoxy) coating is applied to the interior 
surfaces and an inert gas atmosphere is maintained within the vault to 
inhibit influx of oxygen and moisture. There is no teaching in Heintzelman 
of the type of concrete used, other than "precast concrete" or "steel 
and/or concrete". 
Riley et al, U.S. Pat. No. 4,133,928 discloses a composite cementious or 
gypsum matrix material having precombined absorbent fibres and reinforcing 
fibre embedded therein. The absorbent fibres are selected from the group 
consisting of cotton, wool, cellulose, viscose rayon, and cuprammonium 
rayon, with the reinforcing fibers being selected from the group 
consisting of glass, steel, carbon, polyethylene and polypropylene. The 
fibre combinations are impregnated with portland cement or gypsum. Riley 
et al teaches a steel wire/cotton yarn reinforced concrete made by loom 
weaving a tape or felt having ten ends per inch for each fibre in both the 
longitudinal (warp) and cross (weft) directions then passing the tapes 
through a portland cement mortar slurry consisting of one part water, two 
parts cement, three parts sand by weight, and then winding the tapes into 
a mold and placing the mold in a curing room for one month. 
As described hereinafter, the present invention utilizes a "cement-based 
slurry infiltrated fiber composite" construction which is significantly 
different from conventional "steel bar reinforced concrete", "steel fiber 
reinforced concrete", and "pre-stressed concrete", in both its fiber 
volume density and in the manner in which it is made. The "cement-based 
slurry infiltrated fiber composite" described hereinafter overcomes the 
disadvantages of conventional concrete structural members and produces a 
structure which has thinner walls and a gross weight significantly less 
than conventional reinforced and pre-stressed concrete structures of the 
same size and has the same or greater strength characteristics, and a much 
higher bending capacity approximating that of structural steel 
The present invention is distinguished over the prior art in general, and 
these patents in ' particular by improved structural members including 
solid and hollow core beams, poles, columns and enclosure structures which 
are formed of a cement-based slurry infiltrated fiber composite material. 
The improved structural members are produced by first placing a plurality 
of individual short fibers or fiber mats of organic or inorganic materials 
into a form to create a bed of fibers substantially filling the form and 
having a predetermined fiber volume density and then adding a cement-based 
slurry mixture into the form to completely infiltrate the spaces between 
the fibers. Existing structural members may be retrofitted with jackets of 
the cement-based slurry infiltrated fiber composite material. The 
cement-based slurry mixture includes a composition of Portland cement or 
blended cement, fly ash, water, a high-range water reducer 
(superplasticizer), and may also include fine grain sand, ground 
granulated blast-furnace slag, chemical admixtures, and other additives. 
Due to its fiber volume density, and method of manufacture, the resulting 
structure has greater strength, less maintenance, and less cracking and 
deterioration than wood, steel, or conventional reinforced concrete and 
pre-stressed concrete structures, and a much higher bending capacity 
approximating that of structural steel. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide improved 
structural members including solid and hollow core beams, poles, columns 
and enclosure structures formed of a cement-based slurry infiltrated fiber 
composite material. 
It is another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which is highly resistant to cracking, spalling, deterioration, 
rust and corrosion because of environmental changes, such as freeze-thaw 
and/or moisture-heat cycles. 
Another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which is highly resistant to strong winds, vibration, and 
earthquakes. 
Another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which is highly resistant to abrasion and wear by particles of 
hard material. 
Another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which is highly resistant to absorbtion of water from the air or 
ground due to alkali-aggregate reaction. 
Another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which has greater strength, less maintenance, and less cracking 
and deterioration than wood, steel, or conventional reinforced concrete 
and pre-stressed concrete structures, and a much higher bending capacity 
approximating that of structural steel. 
Another object of this invention is to provide an improved structural 
member formed of a cement-based slurry infiltrated fiber composite 
material which can be used as an alternative to conventional structural 
beams, columns, and poles which are usually constructed of wood, steel, 
reinforced concrete, pre-stressed concrete, metal, or fiberglass such as; 
railroad ties for supporting railroad tracks, telephone and utility poles, 
culverts, bridge or highway overpass support beams and columns, pilings 
for building foundations and piers. 
Another object of this invention is to provide a structural member which 
can be formed around existing conventional structural members such as; 
structural beams, columns, poles, bridge or highway overpass support beams 
and columns, pilings for building foundations and piers, etc., to repair, 
reinforce, rehabilitate, or upgrade existing structures in a 
"retrofitting" procedure. 
A further object of this invention is to provide an improved environmental 
enclosure structure formed of a cement-based slurry infiltrated fiber 
composite material which has thinner walls, greater strength, and a gross 
weight significantly less than conventional reinforced and pre-stressed 
concrete structures of the same size. 
A still further object of this invention is to provide an improved 
cement-based slurry infiltrated fiber composite material and method of 
manufacturing improved structural members such as; solid and hollow core 
beams, poles, columns, enclosure structures, etc. 
Other objects of the invention will become apparent from time to time 
throughout the specification and claims as hereinafter related. 
The above noted objects and other objects of the invention are accomplished 
by the improved structural members in accordance with the present 
invention including solid and hollow core beams, poles, columns and 
enclosure structures which are formed of a cement-based slurry infiltrated 
fiber composite material. The improved structural members are produced by 
first placing a plurality of individual short fibers or fiber mats of 
organic or inorganic materials into a form to create a bed of fibers 
substantially filling the form and having a predetermined fiber volume 
density and then adding a cement-based slurry mixture into the form to 
completely infiltrate the spaces between the fibers. Existing structural 
members may be retrofitted with jackets of the cement-based slurry 
infiltrated fiber composite material. The cement-based slurry mixture 
includes a composition of Portland cement or blended cement, fly ash, 
water, a high-range water reducer (superplasticizer), and may also include 
fine grain sand, ground granulated blast-furnace slag, chemical 
admixtures, and other additives. Due to its fiber volume density and 
method of manufacture, the resulting structure has greater strength, less 
maintenance, and less cracking and deterioration than wood, steel, or 
conventional reinforced concrete and pre-stressed concrete structures, and 
a much higher bending capacity approximating that of structural steel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings by numerals of reference, there is shown in FIGS. 
1, 2, and 3, a preferred secondary containment vault V. The vault V is a 
box-like structure which may be buried underground or may be used above 
ground. The preferred vault is a monolithic structure having a bottom wall 
10, opposed end walls 11, and opposed side walls 12. A plurality of 
separate panels 13 form the roof slab 14. A vault in accordance with the 
present invention used for protecting fuel tanks may typically be 
approximately 10 feet tall, 12 feet wide, and 32 feet in length. However, 
it should be understood that the vault may be made in various sizes 
depending upon the particular application and a single roof slab may be 
used. 
In the example illustrated, a fuel storage tank T is placed inside the 
vault V and supported above the floor 10 on cradles C. The vault has an 
interior volume greater than the capacity of the tank it contains such 
that in the event a leak should occur, the secondary containment vault V 
will completely contain the leaked materials. 
The inside corners 15 at the juncture of the bottom wall 10 and the walls 
11 and 12 of the vault V may be angled approximately 45.degree. for a 
distance of about 6" above, the bottom wall. As represented in dotted line 
S in FIG. 1, the top surface of the bottom wall 10 slopes from each end 
wall 11 and one side wall 12 inwardly and toward the opposed side wall to 
facilitate drainage of any leaked material. 
The panels 13 forming the roof 14 are placed on top of the open end of the 
vault V and may be provided with various apertures, such as manhole access 
ports 16 which allow access to the interior by workers to conduct testing 
or other operations inside the vault. The panels 13 may also be provided 
with additional apertures 17 to access various fittings on the primary 
tank, such as monitoring equipment, vapor recovery tubes, drop tubes, 
gauging tubes, and pump manifolds, etc. The apertures are provided with 
cover plates. Suitable seals or gaskets 18 are installed between the top 
surface of the walls 11-12 and the bottom surface of the panels 13. 
Because the vault V is made of a cement-based slurry infiltrated fiber 
composite material (described hereinafter), its total weight is 
substantially less than conventional reinforced or pre-stressed concrete 
structures of the same :size. 
Alternatively, as seen in FIGS. 4 and 5, the enclosure vault V2, or other 
structure, may be formed of individual precast panels of the cement-based 
slurry infiltrated fiber composite material and connected together at the 
installation site. The bottom Wall 10, end walls 11, and side walls 12 are 
formed (described hereinafter) with L-shaped longitudinal metal angles 30 
placed in the form prior to infiltrating the fibers with the cement-based 
slurry, such that the angles 30 form the corners or edges of the panels 
which are to be connected by welding, bolting or other means. The metal 
angles 30 are provided with headed anchor studs 31 which extend inwardly 
to become securely imbedded in the concrete when it cures (FIG. 5). 
Various other enclosure structures may be formed of the cement-based slurry 
infiltrated fiber composite material, such as controlled environment 
vaults used for housing communication equipment, such as telephone, 
computer, or surveillance equipment, etc., which requires a controlled 
environment for proper operation. The controlled environment vaults may be 
partially buried with an entry hatch above ground. 
An added feature of the enclosure structures is that the cement-based 
slurry infiltrated fiber composite material will block radio transmission 
waves, thereby increasing security and perhaps reducing health risks. 
High security utility buildings and explosion resistant vaults may also be 
formed of cement-based slurry infiltrated fiber composite material which 
can be used for storing volatile explosives, weapons, radioactive wastes, 
or other purposes where high-strength and security is a factor. A utility 
building formed of the cement-based slurry infiltrated fiber composite 
material is substantially impenetrable (bullet-proof) and explosion 
resistant, and may be installed above ground and provided With steel doors 
and a steel roof. Explosion resistant vaults are provided with an 
explosion relief roof or lid and may be used for storing fuel tanks, 
volatile explosives, nuclear weapons, test devices, and weapons 
components. 
Although the illustrated examples of the environmental enclosure structure 
is shown as a box-like configuration, it should be understood that the 
structures may be cylindrical or various other shaped configurations. 
Straight or curved panels or combinations thereof can be used for roof 
panels and wall panels in various structures. 
FIGS. 6 and 7 show a railroad tie 32 formed of cement-based slurry 
infiltrated fiber composite material. The railroad tie 32 is approximately 
8'-6" long, 8"-12" wide, and 6"-9" tall and may have fasteners molded in 
the surface which accept a variety of standard fastening systems. 
Conventional concrete and pre-stressed concrete railroad ties are more 
brittle than wood ties. They are also subject to abrasion on the bottom 
side of the ties due to particles of hard material, such as locomotive 
traction sand, which is 10 times the hardness of hydrated cement, creeping 
under the pads during the passage of trains, and hydraulic pressure. The 
component in concrete vunerable to this problem has been attributed to the 
cement matrix. The abrasion prematurely wears out conventional concrete 
ties. Conventional concrete railroad ties also are subject to an 
alkali-aggregate reaction which results from certain types of silica in 
the aggregate reacting with alkalis in the cement to form a gel. The gel 
absorbs water from the air or ground and swells, thus causing severe 
crazing, followed by expansion of the concrete and severe cracking. In 
pre-stressed concrete ties, the result is loss of bond and, hence, 
pre-stress, which leads to structural failure. 
The improved railroad tie 32 formed of cement-based slurry infiltrated 
fiber composite material (described hereinafter) contains a uniform 
continuous mass of individual interlocked fibers or fiber mats of organic 
or inorganic materials completely infiltrated by and embedded in a 
cementious matrix mixture of Portland cement or blended cement, fly ash, 
water, and a water-reducing superplasticizer and has a fiber volume 
density in the range of from about 2% to about 25%,. Due to its fiber 
volume density, such a structure greatly reduces the problems associated 
with conventional concrete ties and provides greater strength, less 
maintenance, less cracking and deterioration, and a much higher bending 
capacity approximating that of structural steel. 
FIGS. 8 and 9 show a solid cylindrical pillar or column structure 33 formed 
of the cement-based slurry infiltrated fiber composite material. The 
cylindrical structure 33 may be formed in various diameters and lengths, 
and may be tapered, depending upon the particular application. Such 
structures may be used as posts, columns, bridge or highway overpass 
support beams and columns, and pilings for building foundations and piers, 
etc. FIG. 10 is a transverse cross section through a column structure 34 
which has a non-cylindrical transverse cross section. FIG. 11 shows a 
transverse cross section through an I-beam 35 formed of the cement-based 
slurry infiltrated fiber composite material. 
FIG. 12 shows an elongate utility pole 36 formed of the cement-based slurry 
infiltrated fiber composite material. The pole structure may be formed in 
various diameters and lengths, and may be tapered, depending upon the 
particular application. For example, most utility poles may range from 
about 60" to about 100" in length, and some may be as much as 250" in 
length. As shown in FIGS. 13 and 14, the poles 36 may be hollow having a 
side wall 37 which contains a uniform continuous mass of individual 
interlocked fibers or fiber mats of organic or inorganic materials 
completely infiltrated by and embedded in a cementious matrix mixture of 
Portland cement or blended cement, fly ash, water, and a water-reducing 
superplasticizer and has a predetermined fiber volume density in the range 
of from about 2% to about 25%. 
As shown in FIGS. 15 and 16, the side wall 37 of the poles 36 may also 
contain longitudinally extending reinforcing steel wire or re-bar 38 in 
combination with the mass of individual interlocked fibers or fiber mats 
of organic or inorganic materials completely infiltrated by and embedded 
the cementious matrix described above. It should be understood that this 
combination may also be used in posts, columns, bridge or highway overpass 
support beams and columns, culverts, and pilings for building foundations 
and piers, etc., in various shapes. Various fasteners may also be molded 
in the surface which accept a variety of standard fastening systems. Steel 
end plates 39 may also be provided at the ends of the structure which can 
be welded to the ends of re-bar 38 or steel wires and/or cast into the 
material when it is formed (described hereinafter). 
FIG. 17 shows a hollow cylindrical pipe 40 having a side wall 37 which 
contains longitudinally extending reinforcing steel wire or re-bar 38 in 
combination with the mass of individual interlocked fibers or fiber mats 
of organic or inorganic materials completely infiltrated by and embedded 
the cementious matrix described above. 
MATERIALS OF CONSTRUCTION 
The preferred environmental enclosure structures and structural members are 
made of a cement-based slurry infiltrated fiber composite material similar 
to a material known as "SIFCON", a relatively new concrete composite being 
developed by the New Mexico Engineering Research Institute of the 
University of New Mexico in Albuquerque, N.M. (NEMERI). SIFCON utilizes 
short steel fibers in a Portland cement based matrix. It should be noted 
that "SIFCON" and the present invention differ significantly from 
conventional "steel fiber reinforced concrete" (SFRC), as explained below. 
In the conventional "steel fiber reinforced concrete" (SFRC) process, the 
steel fibers are added directly to a typical concrete mix in the ratio of 
0.5% to 1.5% by volume. In contrast, the process in accordance with the 
present invention starts with a bed of pre-placed steel fibers in the 
range of from about 2% to about 25% by volume and then infiltrates the 
dense fiber bed with a low viscosity, cement-based slurry composition. 
The steel fibers used in the present environmental enclosure structures and 
structural members are manufactured from drawn wire or cut from thin steel 
sheets. The steel fibers may be provided in several different lengths and 
diameters, and may have some type of deformation to aid in mechanical 
bonding. The present environmental enclosure structures may utilize a bed 
of pre-placed steel fibers in the range of from about 2% to 25% by volume, 
with the preferred fiber volume density being in the range of about 3% to 
10% by volume, and in some applications, from about 5% to 10%. Each fiber 
is preferably approximately 2.36" long and 0.03" in diameter with a 
deformed end. The preferred cement-based slurry ingredients are Portland 
cement or blended cement, fly ash, and water, and a fine sand may be 
included. Ground granulated blast-furnace slag or a mixture of ground 
blast furnace slag and Portland cement may be used as a blended cement for 
the slurry. In addition, a high-range water reducer or "superplasticizer" 
is used to increase the fluidity of the slurry. The term 
"superplasticizer" as used herein is known in the art as a highly 
efficient admixture which is added to cement compositions to improve the 
workability, strength, and accelerate the set time of a concrete, mortar, 
or grout product, and suitable superplasticizers are commercially 
available under various brand names. Other ingredients, such as 
microsilica (silica fume), latex modifiers, polymers, and other common 
concrete additives may be used in the cement-based mixes. 
The bed of fibers may also be formed of one or more blankets or mats of 
generally continuous strands of fibrous material having a fiber volume 
density in the range of from about 2% to about 25%, with the preferred 
fiber mat having a fiber volume density of from about 3% to 10% or from 
about 5% to 10% and each strand of the fibrous material approximately 
0.008" to 0.030" in diameter. The length of the strands in the mats may 
range from about 4" to 30". 
The resulting "cement-based slurry infiltrated fiber" and "fiber mat" 
composite structure has a much higher compressive strength, toughness, and 
ductibility than conventional concrete. The "cement-based slurry 
infiltrated fiber" and "fiber mat" composite structure has compressive 
strengths in the range of 10,000 to 30,000 psi and it's shear and flexural 
capacity is generally 10 to 20 times higher than conventional concrete. 
The present environmental enclosure structures and structural members may 
also be made of a cement-based slurry infiltrated fiber composite material 
which utilizes short fibers or fibrous mats of other organic or inorganic 
material such as; other metals, glass, plastics, aramids, carbon, and 
boron, or combinations thereof. In some applications, the structures may 
also be made of a cement-based slurry infiltrated fiber composite material 
which utilizes short fibers or fibrous mats of epoxy-coated steel fibers. 
As with the steel fibers, the organic and/or inorganic fibers or fiber mats 
are placed to form a bed of fibers in the range of from about 2% to 25% by 
volume and then infiltrated with a low viscosity, cement-based slurry. The 
cement-based slurry may also include: refractory castables, castable 
plastics and epoxies, or clay based slurries. 
METHOD OF MANUFACTURE 
Referring now to FIGS. 18 through 24, there is shown a typical wood or 
steel mold or form F which is used to form a structure having four side 
walls 42 joined together to form a hollow rectangular or square box 
construction open at the top and bottom ends which is supported on a flat 
surface 43. The side walls 42 are spaced outwardly from a central box-like 
core member 44 and extend above the core to form a cavity 45 surrounding 
the sides and top end of the core. Since the cement-based slurry has a 
relatively low viscosity, all joints and holes should be sealed with 
caulking or other sealing material to insure that the form is watertight. 
It should be understood that the core member 44 may be shaped in any 
suitable configuration to form the interior of the product to be molded. 
However, for purposes of illustration and discussion, the core member 44 
is shown to be a square box-like construction having four opposed side 
walls 46 and a top end wall 47, and the product to be formed by the 
present method will be described as a simple box configuration, such as 
those used forming the vault depicted in FIG. 1. 
Small pneumatic vibrators 48 of the type used on bulk cement hoppers, 
spaced about 6 ft. on centers on one side of the form may optionally be 
used when forming walls up to 8 inches thick. For thicker walls, small 
vibrators on both sides of the wall or larger external form vibrators 
could be used. 
The short fibers of steel, or other organic or inorganic material are 
sprinkled either by hand or mechanical means into the cavity 45 
surrounding the core 44. The form F is completely filled to the top with 
fibers (FIG. 19). A major consideration for placing the fibers in the form 
is that they must be allowed to fall freely as individual fibers into the 
form. This allows the fibers to interlock forming a continuous uniform 
mass. 
Alternatively, as seen in FIG. 22, one or more blankets or mats M of 
generally continuous strands of fibrous steel or other organic or 
inorganic material are placed either by hand or mechanical means into the 
cavity 45 surrounding the core 44 to completely fill the form F. The fiber 
mats are placed in the form to form a continuous uniform mass or fiber 
bed. 
Depending upon the geometric properties of the particular fiber being used, 
and to a lesser degree on the geometry of the form, a specific fiber 
volume density will be achieved. The preferred fiber volume density is in 
the range of 3% to 10%. 
After the fibers or fiber mats have been placed, the low viscosity 
cement-based slurry 49 is mixed and infiltrated into the fiber bed, 
filling the spaces between the fibers (FIG. 19). The cement-based slurry 
ingredients should be thoroughly mixed to insure that there are no lumps 
of cement or fly ash which would block the opening in the fiber bed and 
restrict the infiltration of the cement-based slurry. 
FIG. 19 shows the cement-based slurry being added to the fiber bed by 
pouring or pumping it into the cavity from the top. However, as shown in 
FIG. 23, another preferred method is to pump the cement-based slurry 
mixture under pressure into the lower portion of the cavity to completely 
infiltrate the spaces between the fibers from the bottom of the bed of 
fibers to the top thereof and fill the cavity surrounding the core member 
and above the core member. This method reduces the likelihood of forming 
voids in the material and facilitates complete infiltration of the fiber 
bed. 
As shown in FIG. 24, the railroad ties 32, and other rectangular structural 
members are also formed in a process similar to that described above, 
except that there is no core member inside the form. 
The cement-based slurry mixture proportions can vary, depending upon the 
desired strength or other physical properties of the finished structure. 
In addition, form geometry, fiber type, and the particular method of 
placing the cement-based slurry can also determine certain mixture 
parameters. Preferred cement--fly ash--sand proportions range from 90-10-0 
to 30-20-50, respectively, by weight. The preferred ratio of water to 
cement plus fly ash is from 0.45 to 0.20 and the amount of 
superplasticizer is from 0 to 40 ounces per 100 pounds of cement plus fly 
ash. Due to variations in types of cement, fly ash, and sand in various 
locales, and the various brands of superplasticizers available, it is 
advisable to determine the cement-based slurry mix proportions by trial 
batch methods using the available materials. 
The cement-based slurry should remain in a fluid state for a relatively 
long time sufficient to allow the slurry to flow through and fully 
infiltrate the fiber bed. If a form vibrator is used, the form is vibrated 
sufficiently to insure complete infiltration, eliminate voids, and compact 
the cement-based slurry. 
After the concrete has sufficiently cured, the form walls 42 surrounding 
the core 44 are carefully removed so as not to damage the shape formed 
thereby (FIG. 20). The curing procedures are the same as for conventional 
concrete. Depending upon the application, water spray or fogging, wet 
burlap, waterproof paper, plastic sheeting, or liquid membrane compounds 
can be used. 
After the structure has cured, it is lifted off the core 44 (FIG. 21). A 
coating of a penetrating concrete sealer is then applied to all surfaces 
of the structure. This will also minimize the staining and rusting of the 
fibers exposed on the surface of embodiments using steel fibers. 
Referring now to FIGS. 25 through 28, there is shown a typical mold or form 
F2 which is used to form a modular panel structure. The form F2 has four 
side walls 42A made of elongate metal angles 50 having an L-shaped cross 
section joined together to form a rectangular or square box frame open at 
the top and bottom ends which is supported on a flat surface 43A. The 
angles 50 have headed anchor studs 51 extending inwardly toward the frame 
interior. 
The short fibers of steel, or other organic or inorganic material are 
sprinkled either by hand or mechanical means into the center of the frame 
form F2. The form F2 is completely filled to the top with fibers (FIG. 
26). A major consideration for placing the fibers in the form is that they 
must be allowed to fall freely as individual fibers into the form. This 
allows the fibers to interlock forming a continuous uniform mass. 
Alternatively, as seen in FIG. 27, one or more blankets or mats M of 
generally continuous strands of fibrous steel or other organic or 
inorganic material are placed either by hand or mechanical means into the 
center of the frame form F2 to completely fill the form F. The fiber mats 
M are placed in the form to form a continuous uniform mass or fiber bed. 
Depending upon the geometric properties of the particular fiber being used, 
and to a lesser degree on the geometry of the form, a specific fiber 
volume density will be achieved. The preferred fiber volume density is in 
the range of 3% to 10%, and in some applications, from 5% to 10%. 
After the fibers or fiber mats have been placed, the low viscosity 
cement-based slurry 49 is mixed and infiltrated into the fiber bed, 
filling the spaces between the fibers. The slurry ingredients should be 
thoroughly mixed to insure that there are no lumps of cement or fly ash 
which would block the opening in the fiber bed and re-strict the 
infiltration of the slurry. The fiber density and slurry mixture 
proportions are the same for the individual panels as for the monolithic 
structure described previously, but may be varied depending upon the 
desired strength or other physical properties of the finished structure. 
In addition, form geometry, fiber type, and the particular method of 
placing the cement-based slurry can also determine certain mixture 
parameters. The preferred general fiber orientation for the bottom, side, 
and top panels is in a generally horizontal direction, to resist loadings 
normal to the plane of the panel. 
The cement-based slurry should remain in a fluid state for a relatively 
long time sufficient to allow the slurry to flow through and fully 
infiltrate the fiber bed. If a form vibrator is used, the form is vibrated 
sufficiently to insure complete infiltration, eliminate voids, and compact 
the cement-based slurry. 
After the concrete has sufficiently cured, the angles 50 defining the frame 
become secured to the concrete and form a metal perimeter surrounding the 
hard panel P (FIG. 28). The curing procedures are the same as for 
conventional concrete. Depending upon the application, water spray or 
fogging., wet burlap, waterproof paper, plastic sheeting, or liquid 
membrane compounds can be used. 
After the panel P has cured, it is lifted off the horizontal surface 43A. A 
coating of a penetrating concrete sealer is then applied to all surfaces 
of the structure. This will also minimize the staining and rusting of the 
fibers exposed on the surface of embodiments using steel fibers. The 
panels can be easily transported to the installation site where they are 
placed end-to-end or edge-to-edge with the metal angles on each panel 
engaged with the angle on the abutting panel and then field welded 
together to form the enclosure walls. 
Referring now to FIG. 29, there is shown a typical wood or steel mold or 
form F3 which is used to form a hollow core structure having a continuous 
side wall 37, such as a hollow column, pole, or pipe construction. The 
form F3 has an inner cylindrical core member 55 and an outer outer 
cylindrical wall member 56 open at the top and bottom ends which are 
supported on a flat surface 43B. The side wall of the outer member 56 is 
spaced outwardly from the core member 55 to form a cavity or annulus 57 
therebetween. Longitudinal reinforcing wires or re-bar may be placed into 
the cavity and/or steel plates placed at the top or bottom ends of the 
form. It should be understood that the inner and outer members may be 
shaped other than cylindrical in cross section and they may be made in 
sections to facilitate removal of the product after it is formed. 
The short fibers of steel, or other organic or inorganic material are 
sprinkled either by hand or mechanical means into the annulus 57 
surrounding the core member 55. The form F3 is completely filled to the 
top with fibers. A major consideration for placing the fibers in the form 
is that they must be allowed to fall freely as individual fibers into the 
form. This allows the fibers to interlock forming a continuous uniform 
mass. 
Alternatively, as described previously, one or more blankets or mats of 
generally continuous strands of fibrous steel or other organic or 
inorganic material may be placed either by hand or mechanical means into 
the annulus 57 surrounding the core member 55 to completely fill the form 
F3. 
After the fibers or fiber mats have been placed, the low viscosity 
cement-based slurry 49 is mixed and infiltrated into the fiber bed, 
filling the spaces between the fibers. The cement-based slurry ingredients 
should be thoroughly mixed to insure that there are no lumps of cement or 
fly ash which would block the opening in the fiber bed and re-strict the 
infiltration of the cement-based slurry. The cement-based slurry is added 
to the fiber bed by pouring or pumping it into the cavity from the top, or 
by pumping it under pressure into the lower portion of the cavity to 
completely infiltrate the spaces between the fibers from the bottom of the 
bed of fibers to the top thereof and fill the cavity surrounding the core 
member. After the concrete has sufficiently cured, the inner core member 
55 and surrounding outer wall 56 are removed. 
It should be understood that solid columns, beams, etc. are formed in a 
process similar to that described above, except that there is no core 
member inside the form. 
RETROFITTING STRUCTURES 
Existing conventional structural members such as; structural beams, 
columns, poles, bridge or highway overpass support beams and columns, 
pilings for building foundations and piers, etc., may be repaired, 
reinforced, rehabilitated, or upgraded for siesmic resistance utilizing 
the present cement-based slurry infiltrated fiber composite material, in a 
"retrofitting" procedure. 
As shown in FIG. 30, in the retrofitting procedure, a jacket or collar of 
the cement-based slurry infiltrated fiber composite material is formed 
around the exterior of the existing beam, column, pole, piling, or pier. 
This is accomplished by placing an outer member 60"around the structure to 
be retrofitted such that the side wall of the outer member 60 is spaced 
outwardly from the structural member to be retrofitted to form a cavity or 
annulus 61 therebetween. Longitudinal reinforcing wires or re-bar may be 
placed into the annulus and/or steel plates placed at the top or bottom 
ends of the form. 
The short fibers of steel, or other organic or inorganic material are 
sprinkled either by hand or mechanical means into the cavity or annulus 61 
surrounding the structural member to be retrofitted. The cavity or annulus 
61 is completely filled to the top with the fibers which forming a 
continuous uniform mass. Alternatively, one or more blankets or mats of 
generally continuous strands of fibrous steel or other organic or 
inorganic material may be placed either by hand or mechanical means into 
the cavity or annulus 61 surrounding the structural member to be retrofit 
to completely fill the annulus. 
After the fibers or fiber mats have been placed, the low viscosity 
cement-based slurry 49 is mixed and infiltrated into the fiber bed, 
filling the spaces between the fibers. The cement-based slurry ingredients 
should be thoroughly mixed to insure that there are no lumps of cement or 
fly ash which would block the opening in the fiber bed and re-strict the 
infiltration of the cement-based slurry. The cement-based slurry is added 
to the fiber bed by pouring or pumping it into the cavity from the top, or 
by pumping it under pressure into the lower portion of the cavity to 
completely infiltrate the spaces between the fibers from the bottom of the 
bed of fibers to the top thereof and fill the cavity or annulus 61 
surrounding the existing structure. After the concrete has sufficiently 
cured, the surrounding outer member 60 may be removed, or in some 
installations, left in place. 
The fiber density and slurry mixture proportions are the same for the 
retrofit structures as for the enclosure structures and structural members 
described previously, but may be varied depending upon the desired 
strength or other physical properties of the structure which is 
retrofitted. In addition, form geometry, fiber type, and the particular 
method of placing the cement-based slurry can also determine certain 
mixture parameters. 
Preliminary design studies on a cement-based slurry infiltrated fiber 
composite underground vault system in accordance with the present 
invention have been conducted by the New Mexico Engineering Research 
Institute of the University of New Mexico in Albuquerque, N.M. (NMERI). A 
monolithic vault structure was analyzed as an underground rigid frame 
using a soil load equivalent to a fluid density of 95 pcf. Because the 
vault was to be cast as a monolithic unit, special consideration was given 
to the direction of load application as compared to the orientation of the 
structural element. The fiber used in this design study was a "Dramix ZL 
60/80" fiber, made by Bekaert Wire Company, which was found to produce a 
SIFCON with the highest ratio of flexural capacities in the two orthogonal 
directions. The following properties were used in the design: 
For vertical elements (load perpendicular to gravity axis): 
Unconfined axial compression: 10,000 psi 
Modulus of rupture: 1,800 psi 
Shear: 3,000 psi 
For horizontal elements (load parallel to gravity axis): 
Unconfined axial compression: 15,000 psi 
Modulus of rupture: 5,800 psi 
Shear: 4,500 psi 
It was found that for a cement-based fiber composite structure having the 
recited material properties, the side wall thickness need only be 4.5" at 
the bottom and, for economy and as an aid in fabricating the vault, the 
wall could be tapered to a thickness of 4" at the top of the wall. The 
required minimum thickness for the bottom wall was calculated to be 
slightly larger than 4". To allow for any spilled fuel to flow to a low 
point in the floor, the bottom wall surface can be sloped forward to the 
sides for a thickness of 4.5" at the corner fillet. 
On the other hand, a vault fabricated using conventional pre-stressed 
concrete would require a wall thickness of 8" to 10" to meet the 
structural design requirements for resisting these same soil loading 
conditions. 
It can be seen from the foregoing that enclosure structures and structural 
members formed of the cement-based slurry infiltrated fiber composite 
material allows the structure to have thinner walls and a gross weight 
significantly less than conventional reinforced and pre-stressed concrete 
structures of the same size, and has greater compressive strength, 
toughness, and ductibility, and a much higher bending capacity 
approximating that of structural steel. 
While this invention has been described fully and completely with special 
emphasis upon several preferred embodiments, it should be understood that 
within the scope of the appended claims the invention may be practiced 
otherwise than as specifically described herein.