US2364772A

US2364772A - Concrete foem material

Info

Publication number: US2364772A
Authority: US
Publication date: 1944-12-12
Anticipated expiration: 1961-12-12

Description

Dec-.'12, 1944.

R. D. BEI-1Mv CONCRETE FORM MATERIAL Filed Oct. 28, 1941 Patented Dec. 12, 1944 CONCRETE roam Richard D. Behm, Vancouver, Wash., assignor to Maud M Wood Working Company, Greg., a corporation of Oregon Portland,

l Application October 28, 1941, Serial No. 416,854 (ci. :e-431i l 2 Claims.

The present invention relates to concrete forms,

and more particularly to materials to be used in p the construction of such forms.

of the concrete yi'sfree from craters and surface cavities. The globules of water which are the causeof craters andsurface cavities are elim- Concrete usually is poured in a semi-fluid state t into forms in which it sets and hardens, after which the formsa're removed land the concrete allowed to cure. The forms usually are constructed of lumberwhich is secured inplace and braced by an outer framework of timbers. Upon the removal of forms of the usual construction. the surface of the concrete which was'in contact with the inner surface of the form is not smooth.

but is pitted with a great number of small craters or cavities formed by bubbles of air and water which were present in the mix before it set. 1 The problem has been to eliminate these craters and cavities, which commonly occur in all concrete surfaces. In exterior walls water seepsinto the surface cavities and, upon freezing, causes further disruption of thesurface and exposes additional cavities, tending towardv a shortened life of the structure. In-ordinary commercial construction, in order to improve the appearance and also the weathering strength of wall. itis common practice to provide afstucco coating` whiclnhowever, adds appreciablylto the. costl of the finished structure. lOn dams, spillways, and

similar projects. the surface openingspmustbe.

filled, since onv such projects. if tha'concrete is not properly finished, it is sublect'lto considerable wear.

. 4 When the concretemixture is made itisnecessary to add water in sufficient quantityfsojthat the masswill be fluid enough topourand-ow to all parts of the form. The cementi'n vthe concrete combines with only apart'of the Water.`

The remainder of the waterfis present only to give the mass fluidity. This water is necessary only vto facilitate mechanical 4handling of the concrete. Concrete undergoes ian initialsetwaterfrom the layer of inated by absorption intothe absorbent lining. Furthermore, it-has been found that the surface of the concrete is appreciably harder and stronger than when it is poured'against a nonabsorbent surface. This is of great value because it improves tremendously the wearing surface of the concrete structure.

In accordance with one form of the invention, a l

base member such asa sheet of i plywood is provided on one surface with a layer of `highly moisture absorptive material. Concrete forms are built of this material with ther absorptive layer ron the inside of' the form, which layerrapdly withdraws the free water out ofv the Vmixture, filters the cement from the watergand leavesfa remarkably smooth, hard surface after the cement has set. Accordingly,l the surface lof concrete structures made with forms of this material is smooth and of unusual density, vand of` great mechanical strength. c

'It is an object of the present invention, Vtherefore. to provide a newl and improved material `for making concrete forms which will produce a sur- -face on the concrete structure substantially smooth and free of nnfacelrregularities.

More-especially, it` is an` object of the invention-fto providers. `new and improved material for making concrte forms which will absorb free concrete next adjacent thereto, leavin: the concrete surface substam 3 tially smooth and without surface cavities.

1t is a further `obiectof the invention to provide a new and improved laminated material for making concrete 4forms which' will produce4 a ting reaction 'within a reiatlvelysnort .time nur f it is poured-at which time the excess'water, i. e.;

that portion. ofthe water lwhich. does not com- -bine with the cementis givenlv up and 'accumuparticularly at the surface'of' lates as -alcbulesl` the form. When the usual type of woodenfrms is used. this excess water will be observed to-dr'ain out through the cracks b'ctweenfadjacent boards, or eventually be absorbed into the wood itself,

leaving small craters or cavitiesfin the surfaces of the concrete.

Applicant has discovered that if the form is lined with an absorbent material and the concrete is poured against this absorbent surface, then, when the form is stripped away. the surface surface on the concrete which is of hi'ghmechanical strength and extremely .weather resistant. 1 Itis a further object of the invention to irro-l 'vide an ilnprorved-4 material for makina concrete 'forms whichis productive of agconcrete etnic- `mns apprelamy harder and stresser con- -iliv whicnpossesses est,

. face havin! crete" poured in! heretoforefin use, and

a-high degree of strength and' hard- A'Witii other and f advantages inv mind,-

invention resides' in the structure hereinafter described and illustrated in 'thedrawl vins, 'afueras'. understood that various* sinuses` in form. proportion and `detailsy of Iconstruction within the lscope of the appended claims may be resorted to without departing from the spirit or tlyfimprovod wearingsurtion.

In the drawing: A f

l L sacrificing any of the advantages' of the inven Figure 1 is a cross sectional view through a secl tion of a concrete wall being constructed with 5 the aid of forms made of material, according to` the present invention. Y

Figure 2 is a fragmentary view in perspective of concrete form material embodying the invention, portions vthereof be broken -awa'yfvfor l0 greater clarity., l Figure 3 is a perspective view of a portion of a. concrete form making material Vshowing -a modification of the structure illustrated in Figure 1.

Figure 4 is a cross sectionarview of a concrete l wall being constructed in accordance with-aA cus- L and which is explanatory'` l of the objects of the present invention. Figure 5 is a fragmentary 'sectional elevation 2o of a Iconcrete form making materialy according to a modification of the invention.

tomary procedure,

- Inorder to impart a dense lsmooth 'surface tc the concrete, it isnecessary, as'aflrst considera- 1 tion. that the wet mix contain''such an excess 25 of .lwa'ter I that the'mlx, whenpouredr will ow e f l readilyto allapa'rt's-of'the form, 'leaving s'ubstantially no voids :or air pockets therein.l However, this excess wateris somewhat' detrimental to the y l strength of the mass whenit is finally set, and the 30 excess or ,freewater' should be removed from at least the layer of concrete next adjacent the form within the short period of time after the mix is poured andbefore setting takes place. In the 3structurel-embodyingthe invention; the excess 35 Y water iseffectively removed by theprovision Aof extremely-'fine drainage apertures in a readily -wettable material atthe' surface/'of' the form so gthatwater will pass quickly therethrough without l carrying any cement with it.` -l This absorbent 40 material at the surface ofthe form acts as a lter so that no cement is lost from the mix. When the wetconcrete o'wsinto contact with the absorbent v lining of the form, the lining immediately absorbs free 'water into itself, as well as any air bubbles which have. become occluded in the mixture, and leaves a, remarkably smooth and. hard. surface after jthe! cementv has set..4 `By thus absorbing awayzsonie -of thefree water, the absorbent form lining increases the strength of the concrete ad- 50 jacent the'surface; and it is at thesurface of thel structure that increased strength and hard- 'ness .arel most useful, both from the standpoint .of structural strength and of'wearing quality. l l In', accordance with the present invention, I

provide Aconcrete formmakng material comprising a vrelatively rigid base unit Asuch as, for example, a -sheet of plywood having a plurality of pliesof wood veneer adhesively secured interfacially, and inwhich the grain of each ply is ed disposed across' the grains of adjacent plies. To

one side of the base ,member is secured a relatively i thin sheetof moisture absorptive material. Referring to the'drawing,v the form for the concrete wall I0 is formed bya pair of spaced sheets of form making material, each consisting of a base portion l2 which,v in this instance'is a three- `ply plywood panel having suitably secured to one side' thereof layers I3 of moisture absorptive nia- The number of Vplies for the laminated 70 terial. base portion-l2 will, of course, depend upon the .necessary mechanical strength required of the form, taking into considerationjthe spacingof the frameworktimbers, thethickness of .the wallgto bebuilt,l and other factors. Infthe modification 7s occurs.

face of thevabsorptive liningbe of ne texture so 'as to substantially filter'cement from the water f being absorbed thereby. `This lteredlayer of l cement next adjacent the form provides an exl tremely hard,4 layer over the outer surface of the in Figure 3 the base portion I2 lcomprises a vev ply plywood panel, though it will be' obvious that the number of plies and hence the thickness of the base portion may be varied as desired.

The lining yi3 may be of any absorptive material, it being preferred, however, that the outer surface thereof be substantially smooth, that is, having few ifv any fibers extending outwardly therefrom which might become imbedded in the cement and interfere with the clean Aremoval of the form lfrom the structure after the concrete has hardened. One material which has been found suitable foruse as an absorbent lining is `a felted material made of scrap paper and ground wood,-commonly known as chip board. It is preferredfthat the surface of the felt be calendered toproduce a substantially smooth and close textured surface, although it may be desirable to use material having textured finishes on the absorbent lining which would be transferred to the lsurface of the completed structure.

A high degree of absorptivenessis required to produce the best -v results.; However,r the surface. against which the concrete ispoured should not be verygreatly compressible for the reason that the y concrete is `pouredaga'instthis surface",with considerable forcev and dents might otherwise be made by rocks con'tainedin the concrete which y would' destroyA the smoothness of the lconcrete.

after it has set.AV For'this reason the"thickness y of the absorptive lining shouldbe 'of thev order of 4one-eighth to one-fourth inch, it having been determined that a llining of this thickness mounted upon a rigid base portion is only slightly compressible even-though water soaked. An aby sorptive liningof such material and of such thickness will rapidly absorb free water from the layer of wetconcrete next adjacent thereto to V'avdepth l `of about one-half-'inchl'k This absorptiontalles l place within thev first few 'seconds afterthe'vconcrete-has been poured', -and thev water which' has been absorbed intoithe Vlining will rapidly be 'replaced by-Iiuid concrete before the setting action `It-is important that the'outermost surnished wall. -Tests vshowv that -the concrete 1 hardened with an absorbent lining sulchA as herel in-disclosed is appreciablystronger than concrete poured into forms of ordinary construction; and is more resistant to deterioration by freezing.

The absorptive lining I 3 is preferably adhesively secured to the plywood vbase panel I2,v and the adhesive employed .to secure the lining should permit the transfer of Water from the absorptive llining to the v base member. The adhesive coating betweentheplywood base l2' and the absorptive lining i3 is indicated at. I4 in AFigure 2, and prefierably may consist -of a solution of silicate of soda, commonly knownas water glass. Afterl the original absorption of mo' ture from the wet-mix 5, by the absorptive liningl, the moisture from the lining is `gradually transferredthrough the glue line to the wooden'base member I2,v and the absorptive lining is renderedA capablev of absorbing additional water liberated during the second stage of the chemical change lin the concrete.

It will be appreciated that in the structure embodying the present invention, eachfof 'the'laminations is coextensive with each' of the other laminations inthe structure, and that,v duel tothe relativelylarge sizeof the panelsused in makmay to some extent escape from'such forms at the joints between adjacent pieces of shiplap, but none of the cement is ltered from the water, and it is not uncommon to find the lapped edges of such form material filled with cement after the concrete has hardened. Also illustrated in Figure 4 is 'the manner in which Water pockets are formed in the surface of the concrete wall. There is illustrated globules of water I5 lying in contact with the wooden forms I6. yEventually this water is absorbed into the wood, but not until after the initial setting action has taken place. The escape of the water globules I5 leaves cavities and craters in the surface of the concrete wall and beneath these exposed cavities are additional cellular cavities I1 formed by water globules formed at the time the concrete was poured and from which the water has since evaporated from the wall. During the winter seasons the outer cavities becomes filled with Water, which, upon freezing, disrupts the surface and exposes cavities lying therebeneath, thus materially shortening the life of the structure.

In Figure 5 is illustrated a laminated concrete form material comprising a relatively rigid basel unit of corrugated iron I8, to one side of which is secured a sheet of moisture absorptive material I9. This lmodification is particularly useful when it is desired to impart a fiuted surface to the finished wall structure.

, After the concrete has hardened to the desired degree, the forms may readily be stripped therefrom, the absorptive lining being substantially non-adherent to the concrete surface. By the use of the concrete form material herein described, the finished wall will be substantially free of surface depressions or cavities such as heretofore have been caused by water pockets. The

entire surface of the nished Wall will be covered with an extremely dense layer of cement which was filtered from the water absorbed by the absorptive lining, and the wall structure to a depth of the order of one-halfinch or more will be substantially free of voids, thus producing exceptionally high mechanical strength resulting from a condition analogous to case hardening. Moreover, the surface of the wall produced by forms constructed in the manner described possesses a smoothness equivalent to that of a trowelled plaster surface and may be tinted or painted as desired.

Having now described my invention and., in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. A concrete form member consisting of a plywood base member having an absorptive plurality of plies of wood veneer adhesively secured interfacially, and a single lamination of relatively thin highly absorptive material secured to one surface of said plywood base member, a layer of moisture permeable, Water insoluble adhesive securing said absorptive material to said base member throughout the areas of the contacting faces thereof each of said laminations of said material being coextensive with eachV of the other of said laminations, said absorptive material being placed to engage the surface of concrete poured into said form for absorbing water directly therefrom.

2. A concrete form member consisting of an absorptive plywood base member having a. plurality of plies of wood veneer adhesively secured interfacially, and a single lamination of relatively thin, highly absorptive material secured to one surface of said plywood base member and placed to engage the surface of concrete poured into the form for absorbing moisture directly therefrom, said base and lamination of absorptive material being secured together by a layer 4of moisture permeable, Water insoluble adhesive which secures said absorptive material to said base membervthroughout the area of the contacting faces thereof, said thin layer of material and the base being coextensive with each other and the thin layer being provided with a calendered surface having extremely ne apertures therethrough for filtering cement from water absorbed by said material.

RICHARD D. BEHM.