CA1059161A - Concrete security structures and method for making same - Google Patents

Abstract

CONCRETE SECURITY STRUCTURES
AND METHOD FOR MAKING SAME

Abstract of the Disclosure A concrete security structure such as a money safe, vault, or the like, is provided with unique burglar-proof qualities. The security structure includes a hardened concrete composition which possesses torch or high temperature resistance without flaking, spalling or exploding, and superior resistance to attack by means of burglary tools such as hammers, chisels, drills, cutting implements or the like. The security concrete is derived from a moldable uniform mixture which comprises granular temperature resistant aggregates, reinforcing filaments, an expansive cement and water. A method for making safes or vaults is provided by supplying a castable aqueous mixture of ingredients into a metallic shell,casing or mold and permitting the mixture to cure.

Description

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Bac~round of ~he Invention Safes or vaults which employ concrete, heat in-sulating or filler materials in their wall structures are well known. Prior art patents representative of such security structures embodying filler materials include U.S. Pat. Nos.
Re 1S,429; 1,400,10~ 43,087; 2,134,~61 and 2,492,422. ~
: number of problems have ~een associated with concrete structures and methods of making them. For examplc, prior art concrete structures usually have a thick outer metal wall and a lighter inner wall between which a concrete mass has been poured and hardened. Concrete is a mixture of a binding paste and aggre-gate. The paste is mainly composed of cement and water. To make a concrete mass pourable or workahle, there is an excess of water required. The water over and above that required to complete the chemical hydration or setting reaction is called "~ater of convenience" or "free water." This free water usually remains in varying amounts within the cement structure and pre-sents a number of problems peculiar to the manufacture and use of security cement structures. First, such free water subjects the walls of a safe to liability of corrosion. Furthermore, it has been reported that free water sometimes causes sweating which is detrimental to the contents of -the safe. ~lso, un-desirahlc 105s of concrete strength usually accompanies the presence of free water. In the cement curing process, further-more, the free water will bleed within the concrete and emerge , I lOS91~1 from the concrete surfaces. ~leediny water must ~e removed during manufacture and hinders efficiency. In addition, it is nearly impossible to determine the exact percentages of free water in the concrete mass without breaking down the strueture of the safe; and as the free water remains in the concrete mass during a period of years, shrinkage usually takes plaee re-: sulting in the eraeking of the eonerete mass. Therefore, avenues are open for the burglar to penetrate the weakenQd con-crete mass. Shrinkage also oceurs during the euring proeess of ordinary or standard eonerete compositions and this causes the eement to shrink away from the internal walls or easing of the safe structure. Sueh shrinkage prevents a form-fitting eom-posite and faeilitates entry by various burglar means.
Additionally, a major disadvantage associated with known conerete safe llners or walls has been their unsatisfaetory resistanee to attack by acetylene torch or high temperature means. Upon exposure of known conerete masses to an aeetylene toreh, SUCII masses-tend to spall, disintegrate, or even explode.
Spalling or disintegration of the concrete by torch renders the eonerete very susceptible to subsequent penetration by chisel, hammer, drill or other tools. Even without torch penetration, known eoncrete structures are not satisfactorily burglar-proof.
I~ short, i rovements are needud.

~ 1059161 Summary o~ e I~vention This invention is directed to novel security concrete structures which have a numbcr of advantageous features. Safes or vaults made in accordance with the principles of this in-; vention are exceedingly resistant to attack by torch, tool or other means often employed by a burglar. This invention also : provides a unique method for making security concrete bodies or composites which overcome many of the deficiencies associated with prior art techniques.
In one of its aspects, this invention pertains to a novel security concrete composition which has been found es-pecially suitable for use in the formation of safe liners or wall structures. The composition of this invention is derived from a moldable mixture of granular temperature resistant aggregates, reinforcing filaments, an expansive cement and water. The expansive cement is preferably shrinkage-compensating and self-stressing. Such moldable aqueous mixtures have been formulated to provide a slump or consistency which permits them to be worked and free flowing in the manufacture of security door and wall structures according to this invention. Furthermore, this invention is predicated in part upon the recognition that free water in known concrete safe bodies contributes to dis-integration, spalling or explosion of the concrete upon exposure to high temperatures of an acetylene torch. I~owever, by the employment of the security concrete compositions and structures `- ~ 10591~i1 of this invention, torch spalling, disintegration and explosion phenomena have been eliminated.
This invention contemplates the use of an expansive ; cement as the hydraulic binder for the security concrete mass.
An expansive cement for use in this invention is preferably shrinkage-compensating as well as self-stressing. It has been . empirically demonstrated that certain concrete compositions com-posed of temperature resistant or refractory aggregates, re-inforcing filaments, expansive shrinkage-compensating cements and water can be formulated to the necessary consistency for making the mixture workable and suitable for use in a manu-facture of strong concrete bodies and composite concrete bodies for security structures. In contrast, when prior art concrete compositions have been made with comparable workable slumps, the cement structure formed is weak, bleeds excessively and has the disadvantages mentioned in the background of this in-vention. In contradistinction, even though moldable mixtures of this invention have high slumps due to the presence of large amounts of water, the security concrete compositions enter into chemical reactions where such water becomes chemically bound in the matrix or exists in such form which does not cause spalling, disintegration or explosion of the set concrete mass. The pre-cise reasoning or theory for such results is not complctcly understood. Nevertheless, the advantages of this invention have been demonstrated. Other unique advantages are also 10~91~1 ' achieved. l;`or examplc, known standard sccurity concrctc will shrink as it dries, as mcntioned above, and this shrinkage is conducive to concrete cracking even in the presence of re-inforcing stecl. Ilowever, the compositions of this invention eliminate such stress crackin~ and, furtllermore, permit the moldable ingredients to be pourcd into a safe steel casing without separation from the walls of the casing. Bleeding water is not only eliminated, which facilitates production techniques for the inventive security structures, but even though a higll slump is used, tlle mixing water is apparently ; consumed at a vcry rapid rate in the early hydration process.
Further, excess mixing water does not deleteriously affect the concrete produced.
In another of its aspects, this invention provides a security concrete having self-strcssed reinforcing filaments.
Self-stressed concrete has been found to produce security struc-tures of considerable compressive strengtll and resistance to attack by burglar mcans. For example, the security concrete is virtually impenetrable to hammer or sledge attack. The self-stressed concrete and fibers are considered to synergistically perform in the cement matrix of this invention to achieve this result. Moreover, workable slumps are achievable even with the reinforcing fibers in the cement pastc-aygrcyate mix~ure.
The granular temperature resistant or refractory ag-regate is an essentinl compone-t of tlle security concrete \-- lVS91~
composition. This aggregate provides several important pro-perties, including impact resistance, hardness to prevent fracturing and abrasion resistance. Furthermore, the aggre-gate should preferably contribute to processing reproducibility.
The presently preferred granular temperature resistant aggregate is silica sand. An example is standard 20-30 Ottawa sand (ASTM C-190) having a U.S. sieve analysis of no more than about 15% remaining on a 20 mesh screen and no more than about 5%
passing a 30 mesh screen. This silica sand has the character-istics required to provide the density, hardness, abrasion resistance, impact strength and is of substantially pure SiO2 which performs in the preferred manner according to the prin-ciples of this invention. Of course, other types of silica sand may be employed. The term "silica sand" is applied to sand composed almost exclusively of grains of the mineral quartz (SiO2). Commonly, such sands contain more than about 95% SiO2 and certain of them more than 99% SiO2. Another sig-nificant reason for the use of the silica sand aggregate in a;
preferred embodiment of this invention is its substantially non-moisture sorptive character. It is preferred that an ag-gregate be selected which has the property of non-moisture sorptivity in order to reduce the likelihood of free water becoming trapped or embodied in the internal structure of the aggregate material and hence the cement. As developed above, moisture trapped in the concrete or in the internal aggregate .. . .
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structure can lead to concrete disintegration upon exposure to torch temperaturcs. Silica sand has been found to neither absorh water from or contribute water to the concrete mix and, therefore, avoids the entrapment of moisture. Ot?ler aggreqates of course would perform this function and, therefore, other sands can be employed alone or in combination with other non-sorptive aggregates such as granite, or, ferrosilicon, quartz, and the lik~, can ~e employed. Furthermore, while the silica sand preferred is a fine aggregate, other coarser materials may be used alone or in combination with the finer aggregates with-out departing from the scope of this invention. Fine aggregate as used herein means (1) agqregate passing the 3/~ in. (9.5 mm) sieve and almost entirely passing the No. 4 (4.76 mm) sieve and predominantly retained on the No. 200 (74 micron) sieve; or

(2) that portion of an aggregate passin~ the No. 4 (4.76 mm) sieve and predominantly retained on the No. 200 (7~ micron) sieve.
Coarse aggregate means aggregate predominantly retained on the No. 4 (4.76 mm) sieve; or that portion of an aggregate rctained on the No. 4 (4.76 mm) sieve.
The reinforcing filaments suitable for use according to this invention are the type which provide flexible strength and tensile strengtll to the security concrete mass. Further-more, as mentioned above, the reinforcing filam~nts in combi-nation with the expansive hydraulic bindcr will bring about a self-stressing of the concrete to produce a security structurc ' ''' ~" ' ' ' , :, ,, , , , :
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which is exc~edingly strong and has high compressive strengths on the order of abo~lt 80C0 to 11,000 psi. It is preferred 'o use metallic filaments as the reinforcing elements in the security concrete mass because they provide sufficient internal stressing to achieve the compressive strengths, flexibility and tensile strengths of the concrete mass. Furthermore, it has been found that the use of such metal filaments in the concrete mass upon the action of an acetyiene tnrch will deposit on the tip of the torch and tend to destroy the torch tip. The preferred type of metal reinforcing filamcnts are fully described in U.S. Pat. No. 3,429,094. This patent discloses fine steel wires which are preferred for use in accordance with the principles of this invention. Particularly, the steel wires preferably ` are substantially straight and may vary in length from on the order of about 1/2 inch to about 1-1/2 inch and have diameters of at most about 0.3 inch, preferably from about O.OOG inch to about 0.0625. The ratio of length to diamete- of the wire is from about 40 to about 120 and the wire preferably has a modulus elasticity within the range of about 27 to 32 million psi. These 20 wires may be slightly crimped to enhance their binding effect ~
in the concrete mass. Of course, other metallic filaments as t the reinforcing filament element in the security concrete may be employed. Also, the filaments may be round, flat, or the like.
For example, various types of metals and metal alloy filaments , , , .
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can be substituted, including boron, carbon, steel, coppe~r alloys, and the like. Furthermore, such me~al fibers may be coated to resist corrosion. As mentioned, it has been found that the moldable mixture of temperature resistant aggregate, steel fibers and expansive hydraulic binder permits the inclusion of an amount of water which enables the concrete composition to be mixed and worked in production techniques.
The expansive cement component cooperates with - -the other essential ingredients of the moldable composition to achieve the advantageous concrete of this invention. Such expansive cements are well known. A comprehensive report on such cements was issued by the American Concrete Institute ;
Committee 223, entitled Expansive Cement Concretes~ Publication SP-38, 1973, (Library of Congress Catalog Card No. 73-77948).
An especially preferred expansible shrinkage-compensating binder is known as Type K cement as classified by the ACI Committee 116 ~-on nomenclature, Publication SP-l9, (Library of Congress Catalog Card No. 67-30095). A commèrcial product suitable for use in this invention is sold under the trademark ChemComp by South-western Portland Cement Co. This expansive shrinkage-compensating -binder or cement is fully disclosed in U.S. Pat. Nos. 3,155,526 and 3,2Sl,701. Basically, such an expansive binder contains an ordinary portland cement ~
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com~onent ~an~ an expansivc componcnt. Thc exp~nsive componcnt in ChcmComp consists for the most part of stable calcium sulfo-aluminatc (CaO)~ 03)3~503 in thc orm of a tern~ry systern or complex with cY~tractable associated lime (CaO) ancl extracta}~lc associated anhydrous calcium sulfate (CaS04), the extr~cta~le lime being dctermined ~ty the method of ~STM C11~-5~ and asso-ciatcd anhydrous calcium sulfatc bcing dctcrmincd by the method of Forsen as modificd by Manabe and puhlislled in ~.C.I. Journal, vol. 31, 2~o. 7, January 1960 undcr thc title "Determination o~
O Calcium Sulfoaluminate in Cement Paste hy Traccr Technique".
The more specific details of these compositions are included at Column 1 of U.S. Pat. No. 3,251,701, particularly at lines 19-55, and at Column 3, line 26 through Column 9. Therefore, an es-pecially prcferred expandable shrinkage-compensating hydraulic ; cement in accordance with the principles of this invention in- -cludes a major amount of a portland ccment and a minor amount of an cxpansive component in an amount at least sufficient to compensate for the shrinkage of the portland cement and to im-part expansive properties ~hen the expansive component is hy-drated.
More generally, expansive concretes are usually divided into two categories, shrinkage-compensating and self-strcssing. ~mcrican Concrete Institute dcfincs sllrinkagc-com-pensating concretc as an expansive ccmcnt concretc in which expansion if rcstraincd induces comprcssive strc3ses w~lich ~, . , ' . :
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- 10591~1 1 approximately ofEsct tensile stresses in the concrete induced by drying. Self-stressing conerete is an expansive cement con-crete in which expansion, if restrained, induces compressive stresses of a high enough magnitude to result in significant compression in the concrete after drying shrinkage (and creep) has oeeurred. The eompressive stresses indueed by shrinkage-compensating cements in eoncrete are`a~out 25 to 100 psi (2 to 7 kg/em2), and by self-stressing eements above about 100 to ; about 1000 psi (7 to 70 kg/cm2). ~xpansive cements consist predominantly of portland cements, about 90 to 70 percent, with, however, an expansive component in a minor or remainder amount to provide shrinkage-compensating and self-stressing properties.
The ~meriean Conerete Institute has defined three types of shrinkage-eompensating eements, Type K, S and M-X (or M). The three types oE shrin~age-compensating cements are characterized by different alumina-bearin~ agents, C4~3S in Type K, CA + C12A7 (calcium aluminate cement) in Type M-X, and C3~ in Ty~e S. The sulfate is present as gypsum, hemihydrate, anhyclrite and, in pf part in Type K cement, as C4A3S. There remains little doubt that ettringite formation is the source of expansive energy aeeording to the reaetion, 6C + A + 3S + 32~ C3A3CS1l32.
The above abbreviations for oxides are, CaO=C, SiO2-S, A12O3=A, Fe2O3=F, SO3=S, and 1l2O=II. No one oE the oxicles actually occurs as a reaetant except water in part. Phase rule dictates ex-pression o he reaotants ns oxides in a general reaction. Tho :

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practical a~lication of expansive ccment is ~ase~ on controllin~
the kinetics and extent of thc ettringitc formation reaction.
Ettringite starts forming the instant water comes into contact with the cement grains.
The Type ~C cement is presently preferred in this in-vention because the expansive agent of anhydrous calcium sulfo-aluminate uniformly controls the ettringite formation in the cement composition. It is theorized that the precipitation of ettringite is forced into the voids of tlle cement paste and contributes to reducing permeàbility and moisture sorptivity.
Formation of this compound is accompanied by a large increase in volume and is the basic mechanism of expansive cements.
These cements consist essentially of portland cements containing from about 10 to 30 percent of expansive constituents. The expansive ingredient is usually proportioned by the producer to provide enough CaO, SO3, and A12O3 needed for the desired amount of ettringite formation. Ettringite starts to form as soon as water is added to the cement during mixing and continues to form during the subsequent curing period until the SO3 or A12O3 is exhausted. It is essential that the major part of ettringite formation take place after the cement has gained some strength, other~tise the expansion would only deform the still plastic concrete without developing thc desircd com~ressive stress in the restraincd concrete. In expansive ccments, two hydration reactions are involved, namely, the formation of the strength-giving calcium silicate hydrates and the formation of the - ',.

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10591ti1 expansion-causing compound ettringite which requires additional ! water of hydration. The results of this lnvention are con-! sidered surprisinc3 since it is believed that the colloidal nature of ettringite has a tendency to hold large amounts of water. Such water has been found undesirable in prior art eements. ~lso, water has been discovered according to this invention to contribute to spalling and disintegration. ~rher fore, quite unexpectedly, the security concrete structures of this invention do not spall, disintegrate or explode in spite of this tendency of ettringite. Therefore, a large amount of ~l water may be added to the moldable mixture which facilitates : processing and production of the security safe structures of this invention. Slumps on the order of about 5.5 to about 6.5 inches are capable of being used, well above the permissible slumps with ordinary portland cement without weakening the concrete structure in a curecl state. The llydratable expansive cements take up the excess water of the mix by reacting there-with to form a hydrated binder system. Unlike ordinary cement which has been used heretofore in security compositions which ' 20 require an excess of water which remains in the concrete to ~`I provide the disadvantageous effects discussed above, the ,j additional water necessary for the expansible component is ! either used up or contained in the settinc3 process. Further-more, by tlle use of such expansible cement bin~er, compressive strengths on the order of about 9000 to about 11,000 psi are ,, .

!l l '' ,- ~ 1~591~1 achievable in the security compositions of this invention and such strengths provide a virtually impenetrable barrier for hammers and impact tools of a burglar. ~s the security con-crete sets, the expansible cement binder bonds to the steel fibers and at the same time the expansive reaction causes a volumetric expansion of the concrete. Since the concrete is bonded to the steel fibers, in this respect expansion will put the fibcrs in tension and concrete in compression. The concrete is precompressed, but at a level of magnitude much less than that of conventional pre-stressing. The expansive t reaction is complete in the first fcw days of concrete curing.
Later, when the concrete is exposed to drying conditions, it will shrink just as standard portland cement concrete. But unlike standard portland cement concrete, the shrinkage simply relieves the slight precompression and does not build up ten-: sile stresses.
The proportions of the components in the security concrete compositions of this invention will vary. Ilowever, the following broad range of tolerances on a parts by weiqht basis are suitable:
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Sand about 120 to 190 parts Expansible Cement about 80 to 175 parts Steel Fibcrs about 40 to 65 parts ter ab~ut 30 to 75 parts " ~
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10591~1 The above components are used in the examples which follow by mixing in a barrel type mixer with paddles. The dry materials may be added in succession to the mixer as the mixer operates. The dry materials are mixed for several minutes and then water is added incrementally in 20~ steps, with a ' few minutes of running in the mixer between each addition.
~fter all the materials have been added, the mixer is operated for an additional several minutes. ~t this point the slump is measured by the ASTM technique (ASTM C 143-39). When the slump is within tlle range of about 5.5 - 6.5 inches, the moldable mixture of ingredients is cast into place witll sufficient vibration to assure filling to the safe cavity, i.e., door, wall or the like.
Thesc and other objectives of this invention will be further understood by reference to the drawing and the following examples in which:
Fig. 1 is a front view of a safe; and Fig. 2 is a vertical cross section of the safe door filled with the security concrete composition of this invention.
The door 3 of Fig. 1 is mounted in the opening of the safe 4 by suitable means not shown. The front face 5 oflthe door is made of 12 gauge stainless steel and the rear face 6 in this illustration is exposed security concrete 7. Thc cross section in Fig. 2 does not illustrate the other internal com-ponents of t safe door, ho~ever, ie i S to bo undcr 9 tood that ' , ,11 ' ,, 1~)59161 the mclda~lc aclueo~ls mix~ures havc a slump WhiC]I facilitatcs their vibration into cavities and inters~ices forme~ by sucl componcnts to provide a form-fittincl compositc mass therewith.
The stainless steel face 5~ after bendin~ in the suitable shape, I ;
forms a container or cavity for the security concrete. The safe has rcmainin~ walls not shown in detail which may also be formcd by thc security composition of this invention or in com-posite form with steel casings or other supporting materials.
Of course, it is to be appreciated that the sae shown in the 0 drawing is merely illustrative of the principles of this in-vention and other security structures may be constructed to achieve the results afforded by this invention.

: - Examples 1-8 '" ~
Employing the general mixing procedure referred to above, silica sand, expansive cement Type K (ChemComp referred to above), 3/4 inch steel fibers having about 0.016 inch diam-eter, water with or without other materials were mixed and cast into place with sufficient vibration to insure the filling of a mold cavity. The metal door 3 of Fig. 1 may form the cavity.
.0 Table I demonstrates the amounts and kinds of various materials included in the Examples. ~ -. j ,.

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., l i lOS91f~1 1 The amounts of materials are indicated in pounds and, in certain Examples, expanded metal, granite chips, reinforcing bars (Re-Bars) and latex binder-glass fibers were used. The use of latex binder and glass fibers were employed to increase impact resistance. The concrete Examples were cured at ambient conditions and no evidence of bleeding water was observed. After passage of time, the com~ressive strengths of Examples 1-8 were measured at 7 days, 14 days and 28 days after casting.

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10591~;1 T ~ B L E II

COMPRESSIVE STRENGTEIS

I~xample 7 Days 14 Days28 Da~s 69~0 7355 9085

3 6960 8062 8301 ~ -

4 5970 6506 8203 .`i i i~

-~ ~:)59161 As demonstrated by Table II, the compressive strengths of all compositions after 28 days, with the exception of Example 6 which contained glass fibers and latex ~inder, were between 6000 and 9200 psi. Example 6 had a compression strength less than 2000 psi. Table II thus demonstrates that compression strengths mainly on an order of magnitude of 8000 - 10,000 psi are obtainable with security concrete compositions of this inven-tion employing steel fibers. The ~nount of glass fibers and latex in Ex~nple 6 did not provide such high compression strengths in this instance and, therefore, such specific mixtures would not be preferred where high compressive strengths are desired.
The concrete specimens of the Examples 1-8 were then tested with an acetylene torch at temperatures on the order of ! 3400F. Diamond core drill and hammer tests were also per-formed. Table III reports the results of these tests with the ; figures under the flame removal column being attributable to the volume of material removed with the acetylene torch in milli- ¦
liters per minute removed from the specimen. Thc diamond core drill was applied under 50 pounds constant weight with a 2 inch ~' 20 diameter drill. The fiqures reported in the drill test column ¦ are the depth in inches per minute. The hammer test involved a 160 pound drop from 4 feet with a 1 inch bull-nosed chisel, ; 5 blows at the same location. The figures reportcd in thc hammcr test column arc the depth of pcnctration in inclles aftcr test.
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10591~1 T A B L E III

Flame Removal Drill Test ~lammer Test Example(ml./min.)(in./min.) (depth/in.) 1 21 0.49 1-7/8 2 31 0.55 1-3/4 3 27 0.42 1-7/8 4 8 0.16 2-3/4 S 17 0.30 Chisel point broke after 3 blows.
Blow #2 was 6 5 2.33 3-1/2 7 19 0.32 2 a 7 0.30 ~-3/a s ;

1~59161 ~ s demonstrated by Table III thc security concrete com-posi~ions of tl-is invention demonstrated superior torch re-sistance within the range of about 5 ml./min. to about 31 ml./min. In comparison, known security concrete mixtures using ordinary portland cement binder and aggregates are not capable of comparably withstanding such acetylene torch. Rather, known security concretes spall, disintegrate and tend to be explo-sively removed there~y facilitating penetration into the con-crete. For example, an acetylene torch under similar conditions would act on a standard portland cement concrete on an order of magnitude o about 3 to about 8 times as fast. Table III
also indicates that whereas the flame removal of Example 6 was on a lower order of magnitude, the diamond core drill in the absence of steel fibers facilitated the removal of a larger amount of material from the concrete specimen. Furthermore, Example 6 without the steel fibers did not perform as well as examples with steel fibers in a hammer test. ~ccordingly, in order to achieve the full spectrum of advantages according to the principlcs of this invention, the concrete structure should include a temperature resistant aggregate, expansive cement, and reinforcing filaments, desirably metal reinforcing filaments.
~hen steel or metal fibers are used, the expansive cement Type K
will provide shrinkage-compensation and self-stressing of the concrete mass; thus, very advantageous compressive strengtlls are achieve Also, tle shrinka~e-compeDsation provides a '"'' ,;
",. , ' ' ' ' ~ , : j 105~1 form-fitting composite of cement and steel casing or other sup-porting materials.
For the purpose of demonstrating the preferred selec-tion of a non-moisture sorptive refractory aggregate in the con-erete of this invention, several conerete test specimens were pre-`~ pared employing mixtures similar to Examples 1-~, but utilizing two different types of sand~ In one set of specimens, the sand was the preferred siliea sand of the Ottawa type mentioned above, and in other specimens, river or natural sand was used. The speeimens were about 12 inehes by 12 inches by 6 inches in thick-ness. An acetylene toreh test was then condueted. The speeimens eontaining the river sand tended to spall and disintegrate, but yet at a slow rate compared to known standard concrete. In con-trast, no spalling or disintegration was observed with the silica sand. Therefore, a silica sand of a non-moisture sorp-tive character is especially critical to completely avoid spalling or disintegration. It was found that the moisture in the river sand caused the specimen to flake. This was concluded after a second specimen containing river sand was dried for three days at 150F-prior to torch testing. The specimen did ¦ not explode and there was very little flaking. Accordingly, the residual moisture may become trapped in the sorptive, porous river sand particles in the concrete mix which may then cause or tend to cause flaking and disintegration of the concrete mass upon high temperature exposure. Therefore, in accordance with 'l !

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the most prcfcrred principlcs of tl-is invcntion, non-moisturc sorptive aggregate is employed in order to completely avoid dis-integration of the concrete.
It will be understood that modifications of this in-vention in view of the above description and examples may be made without departing from the spirit and scope thereof.

Claims (27)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A safe or vault structure including a cured concrete having enhanced resistance to attack by burglar means derived from a moldable uniform mixture comprising temperature resistant granular aggregates, reinforcing filaments, an expansive cement, and water.

2. The structure of claim 1 wherein said granular aggregates consist essentially of silica sand.

3. The structure of claim 1 wherein said filaments are metallic.

4. The structure of claim 3 wherein said filaments are steel fibers.

5. The structure of claim 1 wherein the expansive cement comprises a major amount of portland cement and an expansive component in an amount at least sufficient to compensate for the shrinkage of said portland cement and to impart expansive properties to said portland cement when said component is hydrated upon curing.

6. The structure of claim 5 wherein said expansive component is present in an amount of from about 10 to about 30 percent.

7. The structure of claim 1 wherein said expansive cement is selected from the group consisting of Type K, Type M and Type S expansive cements.

8. The structure of claim 5 wherein said expansive component contains anhydrous calcium sulfoaluminate.

9. The structure of claim 1 wherein said aggregate is substantially non-moisture sorptive.

10. A safe or vault structure including a self-stressed cured concrete, having enhanced resistance to attack by burglar means, derived from a moldable uniform mixture comprising granular temperature resistant aggregates, metal fibers, an expansive cement containing a portland cement and an expansive component in an amount at least sufficient to compensate for the shrinkage of said portland cement and to impart expansive and self-stressed properties to the port-land cement when said component is hydrated upon curing, and an amount of water to provide a workable moldable mixture.

11. The structure of claim 10 wherein said concrete has compressive strengths on the order of about 8000 to about 11,000 psi.

12. The structure of claim 10 wherein said aggregates consist essentially of silica sand, said expansive cement is Type K expansive cement and said fibers are steel fibers on the order of about 1/2 to about 1-1/2 inches in length and having diameter of at most about 0.3 inches.

13. The structure of claim 10 wherein said expansive component is anhydrous calcium sulfoaluminate.

14. The structure of claim 12 wherein said ingredients are proportioned in amounts on the order of about 120 to 190 parts aggregates, above 40 to 65 parts metal fibers, about 80 to 175 parts Type K expansive cement and about 30 to 75 parts water.

15. The structure of claim 10 wherein said structure comprises a pre-formed wall having a cavity and said concrete contained in said cavity to form a composite structure with said wall.

16. The structure of claim 15 wherein said wall comprises a metal casing.

17. A method of making a safe or vault concrete structure having enhanced resistance to attack by burglar means which comprises mixing temperature resistant granular aggregates, reinforcing filaments, an expansive cement and water, casting said mixture into a container, and curing said mixture in said container to form said concrete structure.

18. The method of claim 17 wherein said aggregates are temperature resistant and substantially non-moisture sorptive.

19. The method of claim 17 wherein said mixture has a slump on the order of about 5.5 to about 6.5 inches.

20. The method of claim 17 wherein said container is a metal casing and the cured concrete is self-stressed in said casing to form a composite therewith.

21. The method of claim 17 wherein said ingredients are proportioned in amounts on the order of about 120 to 190 parts aggregates, about 40 to 65 parts metal fibers, about 80 to 175 parts Type K expansive cement and about 40 to 75 parts water.

22. The method of claim 17 wherein said mixture com-prises silica sand, metal fibers, a Type K expansive cement, and an amount of water to provide a slump of about 5.5 to about 6.5 inches.

23. The method of claim 22 wherein said concrete has compressive strengths on the order of about 8000 to about 11,000 psi.

24. A vault or safe door comprising a metal casing and a liner for said casing comprising a cured concrete resistant to attack by heat and implements derived from a moldable aqueous composition containing silica sand aggregates, metal fibers and an expansive cement component.

25. The door of claim 24 wherein said sand has a sieve analysis of no more than about 15% remaining on a 20 mesh screen and no more than about 5% passing a 30 mesh screen, said metal fibers are steel fibers on the order of about 1/2 to about 1-1/2 inches in length and having a diameter at the most about 0.3 inches, and said expansive cement component is a Type K expansive cement component.

26. The door of claim 25 wherein said ingredients are proportioned in amounts on the order of about 120 to about 190 parts sand, about 40 to about 65 parts metal fibers, about 80 to about 175 parts Type K expansive cement and about 30 to about 75 parts water.

27. A door or wall for a vault or safe comprising a body of cured concrete resistant to attack by heat and implements derived from a moldable aqueous composition con-taining silica sand aggregate having a sieve analysis of no more than about 15% remaining on a 20 mesh screen and no more than 5% passing a 30 mesh screen, steel fibers on the order of about 1/2 to about 1-1/2 inches in length and having a diameter at the most about 0.3 inches and a Type K expansive cement component, said ingredients proportioned in amounts on the order of about 120 to about 190 parts sand, about 40 to about 65 parts metal fibers, about 80 to about 175 parts Type K expansive cement and about 30 to about 75 parts water.