Floors for Dairies

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Floors for Dairies

Ser THT Nztt2 nr. 169 e . 2 BTDG

NATIONAL RESEARCH COUNCIL

CANADA

DIVISION OF' BUILDING RESEARCH

F'LOORS FOR DAIRIES b y

G. M. Price

A N A L Y Z E D

Technlcal Paper No. 169 of the

Dlvlelon of Bullding Reaearch

OTTAWA M a r c h 1 9 6 4

PREFACE

Over a period of eeveral yeare, a ntmber of inquiries were received by the Division of Building Research on the eelection and maintenance of flooring materials for dairies. From the detailed replies to these inquiries an exteneive collection of inforrnation on the subject gradually accurnulated. Thue, when it wae decided to cornplete the study and publidh a technical PaPer, much of the ground work had already been done.

All of the rdesk researchr required in the preparation of this paper was carried out by Mr. G. M. Price, a graduate in civil engineering frorn the University of New Brunswick and a member of tbe Construction Section of the Division of Building Research.

The Division hopes that this report will provide owners and designers with the detailed inforrnation required in the selection, installation and maintenance of floors in buildings where milk products a r e p r o c e s s e d .

OTTAWA M a r c h 1 9 6 4

R o b e r t F . L e g g e t D i r e c t o r

TABT.E OF CONTENTS

REQUIREMENTS OF DAIRY FLOORS DESIGN OT'SUBF'LOOR

GENERAL

PREPARATION OT' SUBGRADE

CONCRETE SLAB JOINTS

DRAINAGE

T.ACTORS AFT'ECTING THE CHOICE OF FINISH WORKMANSHIP

CLAY TIT,ES AND BRICI$ JOINTING MATERIA],S

LAYING TIT.TS AND BRICI$ EPOXY CONCRETE

PORT LAND CEMENT CONCRETE C O N C R E T E T I I , T S

HIGH -ALUMINA CEMENT CONCRETE SUPERSULPHATE CEMENT CONCRETE METAL PLATES, TII,ES AND GRIDS MA,STIC ASPHALT (HOT PROCESS) PITCH MA.STIC

MASTIC ASPHALT (EMUT.STON OR COLD PROCESS)

LATEX-CEMENT CONCRETE

P LASTIC CHEMICAL-RESISTANT _{MORTARS OTHER}

THAN EPOXY MORTARS

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2

2

z

3

4

5

6

9

t z

1 6

1 9

2 3

z 3

z 4

z 5

26

2 7

2 7

z 8

2 9

MAINTENANCE OF. DAIRY FLOORS REPAIR OT'DAIRY FLOORS

GENERAL

CONCRETE FLOORS

TII,E AND BRICK F'LOORS

OTHER TYPES OF FLOOR FINISHES SUMMARY ACKNOWLEDGEMENT BIBLIOGRAPHY P a g e 3 l 3 l 3 4 3 4 3 5 3 5 3 6 3 0 3 1 ( ii)

FLOORS FOR DAIRIES by

G . M . P r i c e

The deterioration of floors in dairies is the rnost pereistent and often the most serious building problern facing dairy owners. Not only is it difficult to maintain high standards of hygiene when a floor becomes rough or cracked, but the repairs interfere with the operation of the plant and, in severe cases, may require a con:plete shut-down for three or four daye.

Floor problerns often occur because of a lack of inforrnation on the relative performance of the various materials and on methods of construction. _{The selection of flooring materials is too frequently rnade} o n t h e b a s i s o f f i r s t c o s t , a n d t h i s i n v a r i a b l y l e a d s t o e x c e s s i v e main-tenance and a great deal of inconvenience. Materlals are available,

how-everr that will when properly installed provide excellent service under the conditions existing in a dairy.

REQUIREMENTS OF DAIRY FLOORS

Dairy floors are subjected to many destructive agents. In the processing and bottling areas a coneiderable amount of milk is spilled or Ieaks from valves or taps, and consequently the floor is subjected to attack by milk fat, sugar and weak lactic acid which forms as the milk sours. The floor is usually continuously wet from spillage or frorn water which is u s e d i n L a r g e q u a n t i t i e s f o r s a n i t a r y r e a s o n s . T h e d e t e r g e n t s used in cleaning the floor may be acidic, but more often they are alkaline and may contain sulphates. _{In eome cases, the acid and strong alkati solutions} that are used in cleaning the pasteurizing units and other equlprnent are drained on the floor. Hot water and steam are often used both to clean the floor and the milk proceseing equipment. The floor may also be subjected to heavy impacts from cans and other equiprnent, and to heavy abrasion f r o m c a r t s o r t r u c k s .

The eeverity of exposure varies throughout the buildlng. In some areas' the action of lactic acid is the rnaln consideration, while |n othere impact and abrasion give the most trouble. To meet the worst conditions, the floor finish rnust: be resistant to weak acidic, alkaline and sulphate solutions, hot water and greaee action; have adequate

resistance to abrasion, heavy impact, thermal shock and wetttng and drytng; be lrnpermeable and prevent penetratlon of effluents to the subfloor; be easy to clean, present a non-elip surface and have an attractive appearance and a long service life.

avallable for uee in dairy floor of the dlfferent rnaterials will

DESIGN OF SUBFLOOR GENERAL

Dairy floor construction should include a properly constructed subfloor and a properly congtructed flnlsh. Thls two-course congtructlon is eseential because the higher quali.ty materlals required for the surface can be confined to the finleh and renewal if required, ls easy and conven-ient. Subfloors are usually constructed of concrete or relnforced concrete.

The structural design of the eubfloor will not be diecuseed in thie paper, but attention is drawn to the plannlng of openlngs ln the floor and location of equlprnent. It is rnore satiefactory to group pipelines and other services passlng through the floor in a comparatively large opening, which may be surrounded by a curb to prevent the entry of corrosive

Iiquids, than to have a number of smaller holee in the floor. In locating the plant equipment, conslderation should be given to grouping llkely

points of milk spillage so that rnaxlmum protection against corrosion need be prowlded only in llmited areas. The following discussion is concerned rnainly with slab-on-grade construction, but sorne of it aleo applies to slabs above grade particularly ln the caee of drainage slopes.

PREPARATION OF' SUBGRADE

A necessary prerequisite for the construction of a durable concrete subfloor on the ground is a well-compacted drained and level subgrade with a uniform load-carrying capaclty. Weak ePots in the sub-grade rnay result in uneven settlement causing cracking of the floor slab and finish and result in poor drainage of a prewlouely well-sloped floor. Since native subsoil is ueually compact, much tnore than fill soil, it ie good practlce to dlsturb the natural ground ae little ae posslble and thus to

reduce the amount of compacting work needed. In sorne case6, it is suf -ficient to rernove the topsoil or sod and place and compact a layer of granular fill such ae gravel or coaree sand. '\4lhen fill is neceseary elther over the whole area or ln irregularitles ln the grade euch as footlng holes or pipe trenches, it should be placed and compacted in layers no thlcker than 6 in. Each soil has an optlmum moigture content at which rnaximum compaction or density can be achieved, and flll should be placed at thie moisture content. Thls is not necessary with granular material which is relatively easily compacted. The eoll can be cornpacted with trucks, bulldozers or smaller equiprnent such ae vibratory compactors, but in

3

-efflcient and eatlsfactory job. Areas that cannot be reached with this equipment, such as areaa adjacent to wal|a, should be tamped by hand or with a mechanlcal rammer. A 4- to 6-in. layer of coaree granular material placed on the fill will provide drainage and a capillary break to rieing ground moiEture, but a rruch thicker layer could be ueed to help control frost heawlng under unheated areas. If the elte and soil do not offer natural dralnage, draln tlle ghould be uaed and connected to a eewert dltch, or sutnp.

A separator should be applied on the eubgrade before the con-crete is placed ln order to prevent any of the fine rnaterial of the wet concrete from flowing into the granular rnaterlal, and to serve as a vapour barrier if the gite is not completely dry. A 4-mtl polyethylene

sheet or 45-lb ro11 roofing may be ueed for this PurPose. In practicet thicker polyethylene, for exarnple l0 mil, is often preferred to reduce the rislsof puncturee which greatly lrnpair the performance of the materlal

as a vapour barrier. CONCRETE SI.AB

In on-grade construction, lnduetrlal floor slabs are ueually not thinner than 6 in. which ie generally adequate for average loadlng

conditions, provided that the concrete and subgrade have reaeonable strength. The elab ehould be deelgned accordlng to accepted englneering practlce particularly in the caee of large jobs or where heavier loads are involved. If the subgrade hae a reasonable and unlforrn bearing value, reinforcement will not add eignificantly to the load-carrying capaclty of the floor. A nominal amount of relnforcing mesh is generally used to help

control shrinkage cracking. For maxlrnum effectlveness it should be located above the mid-depth of the slab.

The quatlty of the concrete should be controlled to rneet accepted etandards. Generally, not more than 4f gafons of water should be used for each sack of cernent. The conventional mlx by volume of l:2:4 cernent: fine aggr egate: coarae aggregate, with rninor adjustments for workability (where neceaaary), will uaually be satigfactory. Integral waterproofing agents ehould not be used since they rnay interfere with bonding of the finlsh, but a standard alr-entralning agent rnay be used to help irnprove the workability of the mlx wlthout a change in the water-cem€nt ratio. The use of a eulphate-resieting portland cernent ls recomrnended where the soil water contains appreclable arnounts of sulphates (uaually there is no concern when the concentration ls below 500 parte per milllon). After it is levelled, the concrete ehould be thoroughly cornpacted by rneane of immereion vibratoro, a vibrating ecreed, or by tarnping and spading. Although the surface should be floated to srnooth lt off, any additlonal finishlng will depend upon the type of floor finish to be applied. The con-crete should be properly cured, but the uee of curing compounds should be avoided if a good bond to the flntsh le requlred.

4

-JOINTS

Control, laolatlon and conetruction jolnte are the three tyltes of jolnts that should be considered ln the conetructlon of concrete aub-floors on the ground. Control joints are installed to allow for ehrinkage caused prirnarily by the initial drylng of the concrete but aleo by

temperature change. 'Wlthout them, uncontrolled cracklng wlll probably occur aince the shrlnkage streases generally excecd the tensile etrength of the concrete. The lnitial ehrinkage or contractlon excGeda euboequent ercpansion due to temperature and moisture changes under normal

conditions; consequently control joints will also provide for e:cpansion. Control jolnts ehould generally be epaced from I5 to 25 ft in both directions tn unreinforced or nominally reinforced elab-on-grade floors, dividing the eurface into approximately square panele. The

spacing is sometlmcs increased in the case of elabg that are more heavlly relnforced since shrlnkage will be restralned by the reinforcement. Atty cracks that form betwecn jointa will be narrowr but the joints themselves will usually open up wider at the greater spaclng and, when carried through the finishr m?y be more dtfficult to malntaln ln trafflc areas. The locatlon of the joints is influenced by the features of the main etructure and it is usual for control joints to follow column llnee. rffhen the pLan is lrregular or where there are abrupt changes in elab thlchresg, it rnay be difflcult to rnaintaln a uniforrn spaclng and some jointe at a spacing shorter than

I5 ft may be required. In special caeee, the spaclng of control joints may be increased to 30 ft, but this ehould be the top limit to avoid exceesive cracking in unreinforced slabe.

Control jointe can be made in eeveral ways, but one of the most economical waye is by eawing a alot, which should not be wider than

Z/t6 tn., in the elab to a depth ot. t/5 to l/4 of the slab thicknees or not less than the maxirnum aggregate Eize. Inetead of a gaw cut, premoulded joint material, guch ae asphalt strlps, may be ingerted level with the tog of the slab and to the above depth, while the concrete is belng placed. Sawed jointa have an advantage ln that they are rnade after the concrete ls flnlshed and do not interfere with concreting operatione. The saw cut should be made ae early as poesible after the concrete hae eet and

preferably durlng the rise of ternperature in order to avaid random

cracking due to drying shrlnkage, but not early enough to cause ravelllng. When the concrete driee, it will crack through ite depth at the planes of weakness created by the eaw cuts or joint etripe, and the configuration of the crack will prowlde an aggregate interlock allowing vertical loade to be t r a n s f e r r e d a c r o s s t h e j o l n t .

Inatead of creating a weakened plane, the eecond method of forrning a control joint is to conetruct lt completely through the elab or subfloor. W'hen such control jolnte are ueed the effecte of ehrinkage can

5

-be rninimlzed by placing the concrete in alternate squares. Followlng this rrcheckerboardtr eequence, partial shrlnkage of half the panels

occurs before the alternate ones are placed, Palnting the edgea of the panele placed flrst with form oil, asphaltic emulalonf or a curing com-pound will prevent bondlng of the new concrete and atlow horlzontal

movement for crack control. Keywaya or bltumen-coated dowels can be ueed to provide vertlcal load transfer acroBB the joint and therefore pre-vent unequal settlement of the panele. A joint that does not requlre

thickenlng of the panel edgee has an advantage ln construction.

Regardlesa of the tlpe of jolnt congtruction, any wire mesh or reinforcement should be reduced or eliminated at control jolnte. Megh may be reduced by cuttlng alternate wires where the jolnt will be. After construction of the eubfloor, a flller material may be used to prevent dirt from enterlng the joints before the finiah ie lald.

Ieolatlon joints are neceaoary to separate or isolate concrete slabs on the ground from walle, footlngs, speclal foundatlone, colurnns, and pipes. _{They should permlt not only horizontal movements of the} eub-floor, as do control jolnte, but aleo vertlcal movementg that occur due to differencee in soil preesures under the constructlon. There should, therefore, _{be no connection acrosB lsolatlon jolnta by meana of} reinforce-ment, bond, keywaye, or dowels. An lsolation joint between the floor slab and walls may be formed with bevelled wood atripe which can easily be removed after the concrete has hardened and a sultable filler put in the ePace. After the flnieh ie laid, a joint sealer can be applied in the top of the joint to make it watertight.

Construction jointa are temporary stopping places in concreting operations and may be necessary becauoe of the difficulty in finlehing large areas in one continuous operation. A true congtruction joint should

constitute neither a plane of weaknesa nor an lnterruption in the homogeneity of the concrete, and every effort must be made to ensure that a etrong bond exists betwecn the new concrete and that prewiously placed. Becauge the necessary bond strength ls generally difficult to achieve, lt ls advisable, wherever poseible, to use control jolnte instead of conetructlon joints at any stopplng places in the concretlng operatione.

DRAINAGE

An lmportant design feature in dairy floors le the provlslon for the drainage of wastes and liqulds from the floor surface and it le good practice to provide the necessary slopee in the conetruction of the sub-floor. _{The eteeper the slope, the more qulckly the liquide will drain and} the Iese chance there ls of serloug attack on the floor finish; the riek of

sllpping becomes greater, however, and more effort wlll be required to move the carte. _{The choice of the elope, therefore, is a cornpromlse.}

5

-It ls usually recommended that the slope be at leaet I in 60 in the Pro-cesaing areas where mllk eplllage le greateet; slopes up to I in 40 rnay be ueed before the floor becomes dangerous and inconvenlent. A slope of I ln 80 may be ueed in areas where there ie Uttle apillage and thls should be adequate to drain wash water. Thlg ghould, however, be regarded as the rnlnimum elope for effective floor drainage becauee any Itight hollowe or depreaeions wlll probably not be drained wtth emaller e l o p e s .

T h r e e m a l n m e t h o d e o f d r a l n a g e m a y b e u e e d : ( l ) t r a n s v e r g e slope - the floor alopea frorn each glde of the building to a central

drainage channel; (21 longltudinal clope - the floor ie laid in a serleg of elopes with channels acroec the wtdth of the bulldlng; (3) Baucer alope -the floor is divided lnto a eerles of rectangular dlehes each with a central dralnage pipe. A mixture of all three tlpee of slopea may be ueed in a dairy, the arrangernent depending upon the best posltlona for the drain.s. The dralns should be as close as posaible to the rnain source of aplllage. They should not paee below any major ltern of equlpment and ahould be constructed so that they can be examlned and repaired without cuttlng the floor. Many of the requirementg are conflictlng, but a good deeign wlll provide the correct welghti.ng of the various factore. Closer epaclng of

drains in areas requiring the eteepeet slopee will decrease the tlme of exposure of the floor to the corroslve liqulds and decrease the differences in surface elevatlons requlred in the subfloor.

The floor should be deeigned to have continuous joints extendlng acrosa rather than down dralnage alopes to mlnimlze the tendency for

drainage channels to forrn in Jolnts. Control and expansion jointe in the finlsh would be ideally located along the top between drainage panels or bays. Any projections in the floor ahould be arranged to offer the leaet resistance to the flow of llquids to drains. The layout should allow efficlent operation but, if poeaible, traffic ahould move acroaB rather than up and down drainage alopes.

FACTORS AF'FECTING THE CHOICE OF. FINISH

The floor finish le the most important component of dalry floors; consequently, the rnaterials used rnust be choeen wlth great care. The requirements of dairy floors have already been listed, and it can be seen that no one flnleh has the properties to rneet fully alltheee reguire-ments. As is alwaye the case with flooring, it ls nece6Bary to select the finish that has the best cornbinatlon of properties for the partlcular uge.

In the case of dalrlee, the suitabillty of a floor finigh ls deterrnlned moetly by lts recletance to the varloue deetructlve agents. In consldering this factor, lt will generally be found that lt is economlcal

7

-to uee more than one type of flnleh in a dalry rlnce exposure conditiona ueually vary throughout the bullding.

Inthe pasteurizingand bottling arelr where corroslve agentr reaulting from milk eplllage and cleaning eolutlona are alwayr present, the beet floorlng materlal ie coneldcred to be denee clay brlck or tile. In order to have a long-laetlng floor, it is neccBBary to uge corrosion-resistant jolntlng materlal wlth the clay or brlck unlts.

Ghemlcal-reaietant reein mortarg have been found to be the most guttable materlals for thie purpote. In addltlon to clay unitr, epoxy reein concrete ls now belng recornmended to reslst corroslon and wear ln dairlee and from reports ln current llterature lt ghould prove to be a very aatlsfactory flnish.

Ordinary concrete made with portland cement haa becn uged extenslvely ae a dairy floor flntah even ln proceerlng areae where it lc attacked by lacttc actd and mllk fat. Becauee of lts relatively low lnltlal coat, lte performance ie eometlmea consl.dered satlsfactory in proceeeing areas. Concrete made with htgh-alumina cement lc more reeletant to milk fat and weak lactic acid and ls uaually recommended in preference to portland cement concrete. Aaphalt mastic, pitch mastic and latex-cement concretes are other types of lnduetrlal floor flnlshea that have been ueed or suggested for dairlea, but they are not generally concidered completely satiefactory becauee of deflcienciea ln one or more reapecta. The properties of these floorlngs can be varied by the use of dlfferent materials and cornpoeitione.

Milk cang and crates are the prlncipal cauaea of poe tible

floor problema in certaln areas of dairieg. If no conveyor syetern is ueed to handle them, impact and abraslon on the floor can be particularly

severe recultlng ln chlpped and worn floorg. In order to enrurc againrt euch damage, metal units such ae eteel tiles, platee, or grida are often recornmended ae floor flnlehes for receivlng and loadlng areaa. Theae areaE are generally only occagionally eubjected to milk splllage and bedding and jolnting material need not be corrogivc-reeletant. A large number of dairleg now receive mllk in truck-mounted tankg wlth the reeult that the floorg are not aubjected to as much impact and abraaion by mllk canlo In these caEeE, materlals auch a! concrete, whlch are not as realetant to lmpact and abraslon as rnetal flooring unlto, may poetlbly be uaed to a greater extent than would otherwiee be advlsable.

Mllk apillage le not usually a factor ln storage areas except for the milk from broken bottlee or cartone, but impact and abraeton from

cratee will need speclal conglderatlon ln chooelng the flnlsh. In bottle-waahing areao, the prlnclpal agente to guard againet are generally severe wear, detergente, and hot water. Wear or abraal.on can also be gevere ln traffic areas euch ag doorways and alsle-\raya, partlcularly when there lr steel-tired trafflc (the uae of rubber or nylon tirea ls advlcable.).

8

-Two important requirements for dairy floore are that they be eaey to clean and have a non-alippery surface. These two requlre-ments conflict, since the srnoothest and densest surface ls norrnally the easiest to clean but le also the most sllppery. In conslderlng safety where more than one finlgh is ueed, one of the mogt lmportant factors le the choice of finishes for adjacent areas. The danger of sllppl.ng is

greatest when a person adapted to a non-sltppery finieh passes from it to a slippery one; adjacent flnlshes, therefore, ehould have approxl,rnately the same characteristics in thle reepect. Good non-elip propertiee

cannot, however, be overlooked becauee of the wet and greaey conditione which exlst in eome areas.

The cost of the floor ls also of prime importance. In calculating it, maintenance and repair costs ehould be added to the interest on initial or conetruction cost. In addltionr any inconvenience, inefficient plant operation, or loea of productlon reeulting from a poor floor flnish is significant but sometimes dlfflcult to agseeg. In many cases, it will be economical to ingtall a durable finleh havlng a high initial cost and thereby reduce subaeguent costs and inconvenience. orx the other hand, in areae whlch can be convenlently lcolated for repair, the periodic renewal of a lesa costly and durable fi.nish may be consldered. One problern in comparing the economics of dlfferent floorlnge ie the difficulty of predictlng thelr durability or llfe in dalries. It ls not posslble to give figures because of the varying factors, but erqperience has shown that the serviceable life of flooringe in dairies under the worst conditions is roughly proportional to its initial cost.

WORKMANSHIP

In discusalng the performance of dlfferent flooring materiale, it is presumed that the workmanship and methodg of appllcatlon are such that the inherent properties of the material iteelf will deterrnine lte

suitabillty as a finish. In actual practice it is often neceBsary to conaider further the methodg and workmanshlp ueed slnce they can contribute as much to the failure of the floor finleh as the \prong choice of materials. This is particularly applicable wlth concrete. Because lt can be eo eaeily made, it is eeldom appreciated that, in order to obtain the hlghest quality of concrete, very special attention must be glven to its manufacture,

compaction, flnishing, and curing. In all cases lt ls advisable that floo1 finishes be laid by people skilled in the laying of the particular material.

CI.AY TIT.ES AND BRICI(S Clay

c o r r o s i v e a g e n t s

floor tiles and brlcks acting on dalry floors

of low poroelty are resistant to all and to abraslon and wear. Their

9

-ease of cleaning and good appearance are other propertiee which make them very suitable for dairy floors, especially in the processing areas. Suitable units are manufactured ae chernical-resiatant or acld-reeictant tlle or brick, but pavers and quarry tilee can also meet the requlrementg. The units should be vitrlfLed and unglazed to engure adequate resistance to corrosion and wear. Better wearlng and chemtcal resistance, lower absorption, porosity and permeability are aggociated with higher burnlng temperatureE for a given clay and method of manufacture, but units fired at highest temperatures are normally characterlzed by very ltmited

r e s i s t a n c e t o t h e r m a l s h o c k o r l m p a c t , a n d i t l s n e c e s s a r y t o i n c r e a s e t h e thickness of the tile where theae factors must be coneidered. For example, brick or tlle I in. or more in thlcknegg ls sultable for light-wheeled

traffic where there i.e no thermal ghock or irnpact. Units Z ln. or more ln thlckness are suitable for moderate traffic wlth impact, while unlts at

least 3 in. thick are required for areas where heavy trafflc and irnpact are important factors.

Larger units are preferred to the smaller ones in order to rninimize the number of joints. r'er*'er and rnore narrow jolnts not only improve the durability of the floor brtt may also offer an appreciable saving in cost when the moet e:q>ensive and corrosive-resietant jointlng materlal is used. The use of the best grade of tile whlch is more accurate in shape is recommended and may save money since jolnts can be made more narrow and rnore uniform in width.

Floors in dairiee are frequently wet and may be greasy and complaints that clay tile is alippery are not uncommon. Apart frorn the srnooth surface finish, which should be satlsfactory for dry, clean

conditions, clay units can be obtalned wlth grooved or roughened surfacee or with abrasives in the surface thereby improving their non-ellp properties. Units containing abrasivee such ae aluminum oxide or eilicon carbide are p r e f e r r e d s i n c e t h e y r e q u i r e l e s s e f f o r t i n c l e a n l n g .

JOINT ING Nd,q,TFR.IAI.S

Although good quallty clay tilee or bricks have outstanding corrosive-resistant propertlee, they frequently fail or need repalr in a relatively short tlrne due to the deterioratlon of the jointlng and bedding rnaterials which leavee crevicee between the units or under the edgee. The mortar joints are therefore considered the most vulnerable part of the floor constructlon. They should be as narrour aa good workmanahlp will perrnit.

Mortars made with chemical-reeistant regin cernents are by far the most useful materials for jotnting tile and brlck dairy floors ln areae

l 0

-epoxy, phenolic, and polyeeter reslns. Regardless of the t1rye of reeln used, these rnortara are ln general reelstant to all the corrosive

liquids acting on dairy floors and to cleanlng with hot water or gteam. I'uran cement ls reslstant to most acida, alkalia, oils and solvents; polyester cement haa a high reslstance to a emaller number of theee corroslve agents. The over-all chernical resistance of epoxy and phenollc resln cements falls eomewhere between furan and polyeeter.

Furan resin mortar has been the most extenelvely uaed in the construction of tile and brick floors. The uee of epoxy and polyester cemente in this field is relatlvely new and the rnanufacturer should be consulted on the sultabllity of any epeclfic product for partlcular conditions. It is unwige to be guided by any general claseification since wlde variations may exlst in the formulation of resins; for example, it is reported that one poly-ester resin cement on the market in England ls recommended only for concentrations of NaOH up to 2 pet cent while another brand is gaid to withsLand 40 per cent concentratlon. The flllere ueed with the resin binders are ueually of a carbonaceous or slllceoug nature, are specified by the manufacturer, and must be inert to corrosive agents.

Mechanical reeistance, bondlng propertles, and sensitivtty to local conditions durlng ml:d.ng and curlng may be elgnlficant factors ln choosing a reeln mortar. In general, the mechanlcal strength of epoxy and polyester reein cements and thelr bond to rnetals and clay units are greater than for the other two, epoxy resin being sltghtly cuperior to polyester. All the resin mortars, however, form a bond to clay rlnlts which is considerably stronger than that formed by hydraulic cement

rnortars and the joints are reasonably ltquid-tight. Furan cement is more eusceptible to variations in temperature and humldity during appllcatlon and curtng than are epoxy and polyeeter resins. In repair or rush work, polyester resin hae an advantage because it hardena more rapidly than o t h e r t l p e s o f r e s i n m o r t a r s .

Mortar conslsting of portland cement and sand is the least costly of the jointing materiale ueed in tiled dairy floors, but it is algo the Ieast reeistant to corrogive agente, guch as lactic acid and milk fat, with the result that joints may become qulckly eroded in areas where mllk

splllage occurs. Ordinary mortar or grout, while it has good reeistance to alkaline solutlona, has little resletance even to weak acids or sulphate

solutlons although sulphate-reeistant portland cements can be used to improve the resletance of the mortar to sulphatee. The use of any of the various types of portland cernents or portland blaet-furnace slag cernent instead of normal cement in mortars does not appreciably improve the r e s i s t a n c e t o a c i d s . A d h e s i o n o f t h e m o r t a r t o t h e b r i c k s o r t i l e s i s adequate, but the joints are not liquid-tight.

In additlon to portland cernents, high alumina cernent (calciurn alurninate cernent) la another type of hydraulic cernent that rnay be used in

t l

-mortars to grout the jolnts of clay tile floors. It has fair to good r e s i s t a n c e t o d i l u t e o r g a n l c a c i d s a n d h a s g o o d r e s i s t a n c e t o s u l p h a t e solutions, but it has little resistance to alkaline solutions and will therefore be subject to attack by alkallne detergents. Although by virtue of its better acid resistance, high alumina cernent mortar should Iast longer than that rnade with portland cement, it cannot be regarded as a p e r m a n e n t j o i n t i n g m a t e r i a l f o r t i l e d f l o o r s i n t h e p r o c e s s i n g a r e a s o f d a i r i e s .

A type of hydraulic cernent which is available in Europe is supersulphated cernent (gypsurn-s1ag cernent). It is reported that rnortar made with thls cernent has good resistance to dilute organlc acids, alkall, and sulphate solutlons. It should therefore provide a fairly satisfactory jointing rnaterial for tiled dairy floors although the joints are no rnore liquid-tight than those made with the hydraulic cernents already rnentioned.

Normal hydraulic cernent mortars often shrink leaving hairline cracks that often lead to leakage and subsequent fallure.

Shrinkage-r e s i s t a n t o Shrinkage-r Shrinkage-r Shrinkage-r n o n - s h Shrinkage-r i n k i n g t t h y d Shrinkage-r a u l i c c e r n e n t r n o r t a r s , t h e r e f o r e , o f f e r a distinct advantage over other rnortars.

T h e a d h e s i o n , r e s i s t a n c e t o d i l u t e a c l d s , a n d w a t e r p r o o f n e s s of a hydraulic cement mortar may be considerably lncreased by the additlon of rubber latex (natural or synthetic) or synthetic resin latex in amounts of about I0 to 20 lb of latex solids to 100 lb of cernent. There are dlfferences of opinion, however, on the capablllties of these rnixtures, terrned latex cements or latex-rnodified cement rnortars" The cement rnay be portland or high-alurnina cernent; the type used will influence the acld resistance of the mortar. When used as a jointing rnaterial in contact with corrosive conditions, it is claimed that the top surface of the mortar often softens due to slight attack on the hydraullc cernent, leaving the latex in a swollen condition; this helps to fill the joint and prevent any further attack.

Natural rubber in latex cement is attacked by fats which makes the mortar unsuitable for dairy floor constructlon, but resistance to fats and greases can be increased by using synthetic rubber or slmthetic resln ernulsions in the mortar. In the case of synthetic resins, polyvinyl acetate ls often used but since this resin has poor resistance to water, rnortars containing lt a r e n o t c o n s i d e r e d s u i t a b l e f o r d a i r y f l o o r s "

In general, all types of latex cernent have a lirnlted reslstance to high temperature washings. Joints filled with latex cement are more liquid-tight and resilient than those filled wlth unrnodlfied rnortars. Latex cernent rnay not requlre the application of water for curing and can be put into service after 3 or 4 days. Before specifying latex cernent ln tlled dairy floors, inforrnation should be obtained frorn the manufacturer to show that the rnaterial has satisfactory properties for the particular case.

Undoubtedly irnprovernents will be made in these rnortars as new cornpositions a r e t e s t e d a n d t r i e d .

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-Sillcate and eulphur cements are used to make acid-resistant mortars for bedding and jolnting acid-resistant clay tile and brick. Neither one ls suitable for uee in dairy floor construction. Sillcate mortars are reslstant to most acfde of any concentratlon, but are not resistant to alkalis or to hot water and ateam. They are ln fact slowly eroded even by cold waterr and therefore are lrnpractical for joints in brick or tile floore ln dairlea. Sulphur mortar, unllke thoee already mentioned, is poured into the jointa in a molten state. It is reslstant to most acidic solutione, but lt hae poor reslstance to alkallne solutions and milk fat and ie not sultable for applications where eteam or boiling water is used in cleaning.

LAYING TII.ES AND BRICI(s

Methods of laylng tlle or brick vary eomewhat, one factor being the use of an imperwlous membrane on the eubfloor in corrogion-resistant floor construction. In such construction, the reasong for installing a mernbrane lnclude protectlon of the concrete eubfloor from aitack by corroslve liqulds and prevention of leakage through the floor structure. Although the clay units therneelves are impervious, the joints will probably not be lmpervioue when grouted with hydraulic cement mortars and there wiU still be the possibill.ty of leaks or cracks at joints due to thermal or moisture movementg even when resin-tpe mortars are used. If the jolnts are cracked, it is probable that the beddlng material is also cracked, permitting corroslve liqulds to reach and attack the con-crete subfloor. Thls can be most serioug since such an attack cannot be observed at first sight.

A membrane also prevents bondlng of the beddlng and tiles to the subfloor and thus preventa any damage due to differential movements between the subfloor and the finlsh. These movements may be caused by moisture changeE, ternperature changes, and structural movement. The rnost extreme differential movements probably occur when new concrete subfloors are covered with clay tiles or bricks before most of the drying shrinkage has taken place. The shrlnkage of the subfloor continuee long after the finish le laid, and, lf the tiles are set in beddtng dtrectly on the subfloor, the result frequently ie the development of compression forces in the finish which may break down the bond springing the finish away from the floor. E>cpanslon of practtcally all clay unlts occura under moiet

conditions (thic molsture ercpaneion should be very low with vitrtfied units) and can add to the stresses produced by shrlnkage of the subfloor. Long-delayed fallures can occur because of these movements especially in the case of thick well-jolnted finiehes whlch may resiet buckling due to

compresslve _{streeges indefinttely even though adheslon has broken down.} To take care of the rnovernents, a membrane is particurarly

recommended for floore lald on new concrete slabe and for large floor areas above grade where deflections occur ln floor slabs.

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-The mernbrane should have adeguate reslstance to ihe corrosive liqulds spilled on the floor, and it ehould be flexible but able to support applied loads. It ls important that the membrane be continuous and laid on the sloped subfloor so that any liquids that

penetrate the flnlsh will flow to the drains. It is neceEsary that machlne bases and services be in position flrst, since the mernbrane shollid be

carried up or over projectlons as well aE up the walle a short dirt,ance so that the floor is vlrtually tanked. Most tlpes of membranes are laid unbonded on a smooth subfloor to allow movementa w'ithout tearing.

The most commonly ueed mernbrane ls asphalt rnastic, either unfllled or fllled acid-resletant maetic, which ie applled hot in several layers to a thicknees of at leaet t/+tn. The aephalt may be reinforced in corners and over edgee with flbreglasa and, ln aorne casesr re!.nforce-ment is epecified over the whole area. It ls common practlce to apply the mastic asphalt dlrectly to the prlmed subfloor relying upon tl-re cold flow of the asphalt membrane to allow for differentlal movements between the subfloor and finish. An alternative method ie to laythe aspLalt mern-brane on a felt or biturnlnized paper placed on a Bmooth eteel-trowelled subfloor, isolating the membrane from the subfloor. Other tyryes of membranes that may be used are saturated roofing felts sealed at the overlaps with a bitumen compound, polyethylene eheeting, po!.yvlnyl

chloride sheetlng, several layers of tar paper well overlapped and several coats of bitumlnous paint. (The last two methods rnentioned are the leaet efficient). Polyethylene, whlch is the most cornmonly used synthetic sheeting, should be heat-sealed at the edges of the sheete and applied to a subfloor that has been finished with a steel trowel to r emove any sharp spots that might puncture the sheet. To lessen the risk of puncturing,

thick sheets (even sheets of l0 to 20 mil thlcknesa are subject to puncturing) or alternatively a double layer of rnaterial can be used. In laylng the sheet, care must be taken to ensure that alr is not trapped under the polyethylene.

The mortar setting bed applied to the mernbrane before the tiles and brlcks are lald can be one of the several compositlons that have been discussed under the heading rrJointlng Materialsrr. The main purposes of the bedding are to achieve flrm and uniform support and to bond the tiles in place avoiding unevenness at the jointe. In caaea where thicker tiles are used, it is poseible to lay the unlts directly on the membrane without a bedding and achieve satisfactory reaults. A mortar bedding of portland cement mortar or other type of hydraullc cement mortar, should be between l/+ and l] in. thlck, and may be reinforced wlth wire rnesh at its approximate centre. A rnlx of I part cement and 3 to 4 parte eand is norrnally recommended with only enough water added to achieve workability. The mortar should be placed uniformly on the sloped eubfloor and a layer of neat cernent paste applied on it before the tiles or bricks are lald. The tiles must be laid before the mortar has dried or eet and forced lnto

complete contact with it, leaving narrow joints which are grouted after the initial eet of the mortar has taken place. Since the tiles recomrrrended are

1 4

-alrnosr. cornpletely imperwious, lt is not neceBsary to eoak them in water to rr:drrce their suction.

The exact width of the jointe wlll depend upon the properties of the jointing materlal, but a width of approxirnately t/a fn. lc frequently specifred. The jointe rnay be grouted with hydraullc mortar consisting of I part cement to 2 parts sand by volume, but for more narrow joints and v"here fine sand is ueed a mix of I cernent to I eand rnay be ueed. The rnortar should be finished flush wlth the top of the unlte, which should be cleaned as work progresres, and after the jointlng ls cured the floor may be opened to traffic. In some caseB, there are economlc advantages in using resin-cement mortar jointing wlth hydraulic mortar bedding but the resirr manufacturer should be consulted since the curlng of certain resin mortare is affected by contact with moisture.

Resin-cement mortarB are often recommended for bedding ag well as jointing. A layer of reein mortar ueually t/e fn. thick is spread on the membrane and a t/+-in. layer of the same mortar or another resin type is applied to two adjacent eidee of the clay unlt which ie then pressed into the beddlng and against the adJacent unit so that the joint le not more than I /A ir,. wide. Excess mortar ie trirnmed off and returned to the mortar board and the joint is finiehed flush with the units. Thls method is preferred to grouting whlch preeents dlfficulties in filltng narrow jointe. Resin

n r o r t a r s a r e g e n e r a l l y f o r m u l a t e d t o c u r e r e a d y f o r u e e i n 2 4 t o 4 8 h o u r s at norrnal ternperatures above 60'F although certaln reglns can be used satlsfactorily at lower temperatures. It is lrnportant that the mlx

proportions of the mortar be that specifted by the manufacturer since the use of the exact amount of hardener or catalyet, which ia uaually premixed with the fi.ller or powder, ie lmportant to enaure proPer curlng. The rnanu-facturerls instructions regarding handling of the reein cemente rnust also be followed since there rnay be sorne danger due to the toxiclty of some of t h e s e c o m p o u n d s .

Most of the procedures already outllned for laying the finieh also apply where a mernbrane ig not used. Speclal attentlon, however,

should be glven to the preparatlon of the gubfloor !o that a good bond between it and the bedding is obtained. The eubfloor ehould be allowed to dry out as long as possible before the ftnieh ls laid. At thtt tlrne, ltg surface ehould be absolutely clean and eound and ehould have a gultable roughneee. A bondlng coat of hydraullc cernent or a suitable primer, depending upon the rnaterials being used, ie applled before the mortar setting bed is laid. A bedding of relatively flexible resin mortar should be considerably better than a hydraulic cement mortar bedding in preventlng corroslve liquids reachlng the subfloor.

Tile patterns may be varled but are generally related to the slope of the floor. The ueual method of laying le with a aimple broken joint

1 5

-and with the continuous joint across the slope eo that no channels are formed down which liquldo can flow. Herringbone pattern is one of the rnost suitable since there are no continuous joints, but lt requlres very accurate tilee and good workmanehip to obtain the necessary uniform j oint s.

An important feature in the design and constructlon of clay tile or brick floors ie the installatlon of ercpaneion joints in the finish to allow for rnovements due to rnolsture and temperature changee. The term rre:<pansion jointrt ia generally ueed even though it is not entirely correct in sorne ca6es. The spacing of expansion joints will depend upon the kind of mortar used for bedding and jointing and upon the method of construction. Where an analysis of a particular case is made, lt may be found that a s p a c i n g o f l 0 f t i n e a c h d i r e c t i o n e h o u l d b e u s e d t o r e l i e v e s t r e s s e s i n t h e tiled fi.nish, while in other caaes a spacing of. 25 ft will be satisfactory.

The closer spacing is advlsable if using rigid mortar and the floor finrsh is bonded to the subfloor. Greater epacing may be used with the more flexible mortars or when a membrane is placed on the subfloor. The joints should be placed along the ridge between floor slopes. E>cpansion joints should be instalLed in the tlled finish wherever it abuts restraining

s u r f a c e s , s u c h a s w a l l s a n d c u r b s , a n d w h e r e v e r j o i n t s a r e l o c a t e d i n t h e subfloor.

When a membrane is ueed, e>qpansion joints should ."xtend cornpletely down through the finlsh and bedding, but not through the rrr€tn-brane. Joint forms, which should be inatalled before the bedding, should coincide accurately with any joints ln the subfloor. The joints should only be wide enough to accornmodate the extremes of movement expected in the finish or floor structure, but ehould not be more narro'w than the normal joints between the tlles. A width up to l/A in. would seerrr to be

sabis-f a c t o r y i n m o s t c a a e s .

Little specific guldance can be offered on the actual choice of joint sealere. It may be that when extrerne movemente are expected in narrow joints, the uee of the beet elastomeric sealants is advisable. One joint sealer which has been uaed recentlv and which has received favourable repcrts is one baeed on a mlxture of epoxy resin and polysulphide rubber. In general, in order to provide a llquld-tight joint the material should be resilient, adhesive, able to withstand any corrosive liquids and norrnal traffic, and not be tacky. The complete filllng of the jolnt with a preformerl type of filler is not the moet satiefactory rnethod, but the joint rnay be partially filled with it and then sealed on top wtth a suitable jolnt sealer.

Although a completely corrosive-resistant floor finish of clay tile with rnembrane and corroaive-resistant bedding and jolnting is

elaborate and expensive it is recomrnended for processing areas when a dairy is expected to stay in operation for a long tirne and if there will be

1 6

-few alterations to the plant. The initial cost can be lowered, however, by the use of cheaper and lees reeietant bedding, although the quality of the floor will be lowered resulting poesibly in lncreaeed rnalntenance coet.

EPOXY CONCRETE

The epoxy concrete which is used as a floor flnish la cornposed of basically the same rnaterials ac the mortar used for bedding and

jointing tile and brlck floors. As are the other resins dlecuseed in the previoue section, epoxy resin is clasgified as a thermo-eetting plastic, that ie a plastic which when cured by heat and/or chemical rneans is traneformed into a golld which cannot be reshaped by heatlng. The curing or hardening of epoxies is inltlated or activated by the addltion of an agent known by several terms - catalyst, curing agent, hardener, or actlvator.

Since epoxy concrete or mortar is a relatively new material with many formulations and aince lts main use in recent years has been in the repair of concrete gtructures, available information on the reeigtance of epoxy concrete flooring to wearr chemicale, and other agents pertalns _, t o s h o r t p e r i o d s o f t i m e o r i e b a s e d o n l a b o r a t o r y t e s t s . I t i s n o t p o s s l b l e , therefore, to write with certainty about the performance of epoxy flooring. Indications arer however, that it ie reslstant to heavy wear and to most corrogive agente eircountered on floors. It ls coming into lncreaslng use in areas where previously a chemical-reaistant clay tile or brick finish was considered the only durable flooring, although the over -all chemical resietance of clay units is etlll greater than that of epoxy concrete.

In dairies, properly prepared and applled epoxy concrete flooring has more than ample resietance to the weak organic acids, weak alkaline solutions, fata, and sulphatee. It ie impervious to these eolutions and to water and will therefore offer good protectlon to the subfloor.

Because of its impervlous and relatively emooth eurfacen lt ls easy to maintain. Epoxy concrete sete without volurne shrinkage and can be formulated to be flexible enough to permit gorne differeniial rnovements wlth the subfloor and to have adequate reslatance to therrnal ehock and mechanical impact. It has very etrong adheslon to properly prepared con-crete and other materlals and can be readily formed around corners.

Although epoxy resins themaelves are sllppery, fillera or aggregates can be chosen to provide a slip-resletant surface.

Epoxy concrete flooring consiets essentlally of an epoxy resin, curing agent, and aggregate. The propertlee of the floorlng can vary not only because of a change ln the proportlona of th€ lngredlents, but also because of changee in their propertiee. Epoxy reeing may be manufactured in pure form in consistencieg ranging from a eolld to a viecous liquid

although they are eeldorn used ln this unmodifled forrn slnce certain desir-able properties can be imparted bythe addition of diluents, fillers and rnodifier e.

1 7

-As the vlscosity of the uncured resln cernent ie decreaeed so is the chemical and abraaive reaistance of the cured product; it is therefore recommended that a hlgh-vlscoeity reein be used ln the

production of a chernical-regiatant and wear-resistant epoxy floor topping. The cholce of the curing agent or hardener determineg the tpott life (the time available to apply the concrete before lt becomee too viscoue to use) and the tlme required for the concrete to cure fully. The curing agent may provide a room temperature cure (referred to as cold settlng), while others may requlre that heat be applied to the mixture. In general, systema that cure at room ternperature (about 70'tr") have the lowest heat reeletance; heat-cured aystems are reelgtant to temperature6 above 200"F. Heat-cured concretc is not requlred for dairy floore nor for most other floor work, although gentle or moderate heat may be uted to promote a faeter cure. Beeldes the pot llfe and curing tlrne, hardeners rnay have an effect on the vlacoelty of the uncured system, rnay act as flexibillzers and to gome extent rnay effect the chemlcal reaigtance of the cured product. The moat commonly uaed t1ryes of curing agents are baeed on amines and amldea. It is reported that amines are better for induetrial floor finishes because they produce a higher chemlcal resistance.

Sllica sand or crushed rock, such as granite, quartz, or trap rock, ie generally uaed for aggregate. Wtth these hard aggregatee the epoxy concrete should be relatlvely non-sllp, but when lmprovement ln thls property is dealred aluminum oxide, silicon carbide, or emery

aggregate may be ueed in the mix. To eneure a good bond with the resin cernent it ia important that the aggregate be dry and that it be carefully g r a d e d f r o m c o a r a e t o f i n e .

The arnount of aggregate that can be completely mixed in and wetted not only depends upon the grading of the aggregate but also upon the vlscosity of the cernent (epoxy resin and curing agent). Mlxee hawing

I8 parts of aggregate to I part of epoxy cement have been reported for a low wiecosity cernent. For durable flooring, however, a high vlscosity cement which rnay require only 3 to 7 parts of aggregate to I part of epoxy cement is ueually recommended. The rrranufacturer rnay eupply the ingredlents already proportloned. Ore property of the resin cement that should be coneldered in proportioning the rnix lg lts high coefflcient

of thermal e:cpansion aE compared to ordinary concrete. It ls of con-siderable advantage to use a mix with the hlghest poeaible volume of aggregate so that the coefflcient of e:cpanalon of the epoxy concrete wlll rnore closely approach that of the concrete eubfloor in thoee areas sub-jected to thermal shock. Thls problem is more acute wlth the etronger and brittle cured epoxiea.

An epoxy flooring applled ln a I /+-tn. thl.cknees ia uaually thick enough to provlde the required wear reslstanee, strength, chemlcal

1 8

-resisiance, and irnpervloueness. A thickness down to l/8 in. may be considered aCequate or the most economlcal ln some caseer while a flnish thicker than I /+tr.. rnay be excesslve In cost without appreciably Improving the quallty of the flo::.

S!n.e a bond fallure with these thin topphga greatly irnpairs their perforrnance, every .ffort rnust be rnade to achieve a strong bond between the epoxy finlsh and the concrete subfloor. The subfloor should be sound, clean, dry, and sllgl^t!.y rough. It should be cured and let dry as long as poseibl- before rhe epoxy is applied, the minimum time

required deperrding upon the resln rnanufacturerls instructions. Before the epoxy is applied, it may be necegsary to clean the concrete by

scrubbino wiLh a detergent or eteam cleaning or to clean and roughen the surface by the use of hydrochLoric acid, dty sand blastlng, mechanlcally wire brushing, or poselbly other rneans. In additlon, the rnanufacturer wil-l probably recommend the appLlcation of a prlrner just before the epoxy is appliec' Although it ls claimed that sorne prlmers are suitable for applicatioii on moist surfaces, it is always best to have a dry surface.

E p o x y r e s i n s y s t e m s h a v e a l i m i t e d p o t l i f e a n d l a r g e m a s s e s will harden more quickly than srnall ones because of the exothermic

rcaction which cornplicates the rnixing and handllng procedures. To counteraci these factors, small batches are mechanically rnixed at the job :ite and applied prornptly. The floor finish is screeded and trowelled

srnooth in rnuch the sarne rnanner as concrete except that the working tirne is rnuch shorter anC the flntehing is completed ln a matter of minutes. For rnaximurn wear and chemical reslstance, the epoxy concrete should be c o n s o l i d a t e d a s m u c h a s P o 6 8 1 b l e . I n g e n e r a l , e p o x y c e m e n t s u s e d i n concrete floor finishes are forrnulated to cure at a rnlnimum ternperature of about 60'I. and will be ready for light trafflc in one to two days and for full service in about slx days. The manufacturer can be consulted on the appllcati.on of heat by such means as larnps to cure the floor finish rnore rapidly and perrnit eartler use. Flash setting of the rnaterial rnight occur above 100"F, rnaking lt neceeeary to limit the worklng ternperature.

B e c a u s e t h e b o n d o f e p o x y c o n c r e t e t o l t s e l f i s v e r y s t r o n g , the floor fintsh can be one continuoua sheet even though lt may be applied in several sections, and lf flexible enough, it can be jolnt-free. It is recornmended, however, that any jolnts in the concrete subfloor be carried through the epoxy finlsh and filled with a rnaterlal such ae a flexible ePoxy jolnt filler. Jolnt forrns may be rernoved before the epoxy concrete has fully hardened.

Epoxy resin formulations can be applied as coatings to protect concrete floors frorn corrosi.on and wear and when used with abrasi.-es will provide a non-sllp surface. The abraslve whlch rnay be alurrrinutn oxide, silicon carbide, elrreryf slllca, or sirnilar hard grit, should be

1 9

-applied in a uniform layer while the epoxy regln la stlll tacky; surplus grit should be swept up after the resin hae hardened. A fine grltr Bay 60-mesh screcn, would be moat appropriate for dairles where a smooth surface is desirable for sanitary reasons. As an alternative, prior to applicatlon, the abraeive can be incorporated Into the resin in sufflcient q,rantityto give a elip-resietant coating to the surface. Ag a matter of interest, mlxtures of epoxy reeln and coal tar have been uged wlth abragive in the applicatlon of non-slip surfaces. Although not ag tough and wear-reelstant aa straight epoxiesr epoxy-coal tar materials are less costly.

When ueing epoxy resin materials, a few important precautions should be taken since aome of the lngredients may be ekin irritants.

Information on ventilation and the uee of coveralls and rubber gloves should be obtained from the manufacturer. In eummary, the limited e4perience to date with epoxy concrete flooring indlcatee that lt wlll pro-vide a durable floor flnish in dalries. There is a lvide range of poesible composltions, however, and the manufacturer should be coneulted about the selectlon and use of hia producta.

PORTLAND CEMENT CONCRETE

Portland cement concrete toppinge are the most comrnon industrial floor finlshes in use today, and have been ueed extensively in dairies. The primary advantages of a hlgh quallty topplng are very good abrasion and lndentation resistance and good lmpact reslstance at a relatively low inltial cost. Other properties lnclude good resistance to alkalis, water, mineral olle and solvents. Concrete ie, however, vulner-able to attack by organlc acids and fats which are found in rnilk wastes, by vegetable olle and, when rnade with normal cement, by sulphate

solutions. Although it cannot be said that concrete ie reslgtant to even weak aclds, the rate of penetratlon and attack by the weak acldlc dairy wastes can be conslderably decreaeed when a dense and irnpermeable con-crete is used. Such a concon-crete can have a reasonable life even in the proceeeing areas. On the other hand, if the concrete ls not good quality and the floor ie poorly drained and rnalntained, the concrete finish will deteriorate rapidly and may need repair in less than two years.

The methode of constructing concrete floor finishes have been described rnany timee and will not be glven in detatl ln thls report. Some of the eigniflcant points, however, will be rnentloned. Any of the portland cemente can be chogen depending upon the deeired properties and avail-ability. For example, sulphate-resleting cement can be used if the wash water used ln cleanlng operations contains appreclable arnounte of dlssolved sulphates. The uee of low-heat portland cement allghtly decreases the vulnerablllty of the concrete to chemlcal attack. It muat be emphaaized,

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-however, that the choice of cement is not the controlllng factor in achieving chemical r esistance.

The aggregate should be clean and durable, conform to recognized standards, and should be properly graded. The flne aggregate should be contlnuously graded frorn coarae to flne and have tnore than 95 per cent passlng the No. 4 sleve and less than 5 per cent paeslng the No. I00 eievei the coarse aggregate should pass the 3/8-in. sieve and be retained on the No. 4 sleve. The cholce of eand or crushed stone for fine aggregate ls the aubject of some controversy. Recent research, _{however, indicates a sLrong preference for natural eand which,} because of ite partlcle shape, permlts a lower water content to be ueed in the rnix for adequate workabillty, thereby lncreaging strength and reducing shrinkage and poroelty. _{Coarse aggregate should be crushed hard igneoue} rock such as granlte or traprock rather than gravel which produces a more slippery surface when the floor is exposed to wear. Emery aggregate has been recornmended as being very euitable for use ln concrete dairy floor finishes.

The recomrnended rnix for a concrete floor finish is usually I : l : 2 , _{c e m e n t : f t n e a g g r e g a t e : c o a r s c a g g r e g a t e b y w e i g h t and there appears} to be no advantage ln departing from these conventlonal values. Any small variations in the proportions _{necessary to achieve rnaxirnum density and} the desired consistency should be determlned by trial or by laboratory tests. _{It is always better to meaeure the conetituents of the mix by welght} rather than by volurne. _{The lowest possible water content that will permit} good compaction should be ueed. The water content including any surface moisture carrled by the aggregate ehould not be more than 3) gallons per sack of cement. _{The consistency of the mix having the low water /cernent} ratio necessary for the moet dense and durable concrete will be auch as to produce a dry no-slurnp concrete and will regulre the use of povrer equlp-rnent, such as floats, to obtaln rnaxlmum cornpaction. Hand rnethods of finishlng wlll necessltate the use of a higher water/cement ratlo, which will reduce the durability of the concrete and increase ehrinkage. Thls may result ln cracklng or ltfting of the topping.

The uee of admixtures ls not generally advantageous although some admixtures may irnprove the workability so that the water content, particularly _{of the hlgher slump concretesr may be reduced. This will} decrease the porooity, thereby lncreasing the durabillty of the concrete. It has been reported that the use of fly aeh increasee to some ext'ent the resistance of concrete to the attack of mild acids.

The concrete finish may be placed while the subfloor is etlll plastic or after the subfloor hae hardened. In the flrst caee, the flnieh, which is described as a rtmonolithlc finish, rr iB usually about l/+ tr.. thick; in the second case the Itbonded ftnlshtt ls usually about t] in. thick.