1. USE O F THE N E W CEMENT COMPOSITION AS A THIK VENEEROVER CONCRETE WALKS FIGURE
For the purpose of providing nonskid surfaces, thin coatings (I/! tp ‘/a inch) were troweled onto the existing smooth concrete walk, The adhesion t o the concrete and its resistance t o damage by abrasion and water are demonstrated by the perfect condition of these walks after 7 months of constant wetting during which time over 250,000 people walked over them. The ridges shown were made intentionally to provide a I ough surface.
A New
Inorganic Cement and
Adhesive
M ;zg;F;
DEAN 5. HUBBELL Mellon Institute of Industrial Research, Pittsburgh, Pa.
their solubility. The cementing constituent, magnesium oxychloride, is rather easily hydroFrench chemist, in 1876 (18). lyzed, producing a magnesium Since then, these cements have chloride solution. When such been the subject of much recements are exposed to weatherThe shortcomings which have restricted search because they possess a ing or, in the case of floors, t o the use of magnesium oxychloride ceunique combination of properexcessive washing or mopping, ties that offers many possibilithe binder is progressively rements are eliminated by the addition of ties to the building arts. Their moved. As a result the cement 10 per cent of finely divided copper powbody becomes weakened and great strength (three to five der. During and for long periods followcrumbles. If the magnesium times that of good Portland ing the hardening of the cement, the chloride resulting from t h e cement concretes), the short inmetal is converted to a new cementing solution of the cement is not terval required to attain this washed away but is allowed strength, their remarkable dematerial that resembles the natural to remain in c o n t a c t with gree of resilience (Figure 2), the mineral, atacamite. fact that they can be produced the latter, its presence accelerThe formation of this new phase in the from plastic mixes, and, most ates the disintegration of the cement composition increases its remaining magnesium oxyimportant of all, their ability to strength and resistance to abrasion, prechloride. bond perfectly to many mateA second serious handicap to rials were soon recognized. They vents its damage by water, eliminates the more general use of these have therefore found extensive harmful expansion, reduces efflorescence, use as adhesives and as binders cements is the excessive volume and imparts sufficient tolerance of lime changes that are sometimes for a great variety of materials to permit of permanent bond t o Portland and have been employed as the encountered. The careful user cements. The new compositions have an cementing constituent in compocan, in general, reduce the amount of volume change by sition floors, stucco, tiles, and unusual combination of properties which selection of the plastic magnesia many other building materials fits them for wide utility. that are either preformed or and bv close attention t o mix proportions , aggregate grading, cast in place. and curing conditions, but he cannot avoid the occasional I n this country, especially during the period 1918-28, appearance of several types of volume change that are fundamagnesium oxychloride cements were used widely for stucco mental to the cement and over which he has no control. and composition floors. Unfortunately, however, these ceThese changes are as follows: (a) the critical effect on t&e ments have certain inherent shortcomings t h a t have given cement of the lime content (6, 94) and calcination temperathem such a bad record of performance that, notwithstanding ture of the plastic magnesia; ( b ) the harm due to excess the useful qualities mentioned, they are employed only to a magnesium chloride or oxide (4, 11,Is),one of which cannot small extent today. be avoided in actual practice; and (c) the severe alterations The greatest limitation upon their use has been imposed by AGNESIUM
oxychlo-
123
12.4
INDUSTRIAL Ah D FNGIUEEIIING CIIEMISTKY
VOL. 29. NO. Z
in volume that occur as the inagnesium oxychloride k hyof w&terproofing. Theinvestigation wastherefore directed toward finding some way to change the cement fundamentally; drolyzed and magnesium chloride is lost from the system. Other sources of trouble are efllorescence (caused by mitwo objectives were pursued: (a) An effort was made to find n fourbh component to the system MgO-MgC12-fIz0 that would gration of excess magnesium chloride to the surface of the fonn a new insoluble phase which, being distributed throughout cement where it is the niagnesium oxychloride gcl, would prevent its hydrolysis. depasited in an inThe second objective was to find some manner to protect the soluble white Hm, magnesium oxychloride cement from itmlf-thatis, todiscover probably magnesium hydroxide) some scavenger of niagnesium chloride that would remove and i n c o m p a t i the inevitahle excess as the eeinent herdened and would also be bility (7) with present in the hardened cement to combine with magnesium clrloride set free by subsequent hydrolysis of the magnesium Portland c e m e n t oxycliloride. compositions or other i n a t e r i a l s Experimental that contain lime. Both cements will The search for this fourth component involved the incorhe d a m a g e d if poration of a great many materials in experimental mixtures. they contact each A study of tlie natural minerals that have survived the ceno t h e r w h i 1e turies prompted the trial of many materials which might Froum 2. TEST TO DETERMINE damp. react with the cement to form a synthetic counterpart of MODULUs OF Rl7PTUItE OF THINSLAB Research on the natural mineral. Many metallic powders and salts were magnesium oxyfound that were converted in the cement to insoluble comchloride cements pounds but added no desired property to the cement. has p r o c e e d e d It was observed, however, that cortain copper salts formed a l o n g t w o broad an insoluble colored reaction product in the cenient that appreciably improved its resistance to water. Copper evifronts. Oue group of workers dently answered the first requirement of forming n new insoluble phase throughout the magnesium oxychloride gel. has sought to learn tlie nicchsnism o i their hardening and to establish the A study of all manilem of introducing the copper ion into the constitution of the reaction products (6, If, f&-16,ZZ, $8). cement disclosed that., if finely divided copper powder is During recent years it has been clearly established (If) that added to tlie cement mixture, it is converted during the basic magnesium chloride is a definite chemical compound, hardening of the cement, in air to a new blue-green compound although complete agreement has not yet been readied in (Figure 3). The formation of this new phase throughout the . group usigning the molecular formula in all O E ~ ~ S Another cement proved to answer both objectives because the copper OS workers has attacked the problem from the practical angle compound so produced was not only unaffected by water and of determining proper materials, mix proportions, and curing protected its hoat, the magnesium oxychloride, but it also practice, tu produce t.he desired physical characteristics in removed the excess mngnesium chloride from the cement. the resulting cement. The copper particles did nut a t once react completely, and The Magnesia Cement Laboratories of the Dow Chemical their conversion continued over long periods. Some copper, Company havc contributed greatly in establishing and oomtherefore, remained in the cement to convert to the new phase piling comprehensive data relating to the uses of these any magnesium chloride that became available from suhsecements. Their hiilletins constitute a valuable text on magquent hydrolysis of the magnesium oxychloride, Chemical, nesium oxychloride cements. petrographic, and x-ray examinations indicated tlie mechaNotwithstanding the many hnprovememts that have been nism of the conversion of the copper to the new hlue-green made in these cements during the past sixty-five years, they phase and identified it as cupric oxychloride, identical to the still retain three fundamental weaknesses: solnbilitp, tendnatural mineral atacamite, 3CuO~C~C1~.311~0, whose insoluency toward volume change, and iiicompatihility with lime Iiility i s e m p h a s i d by its occurrence in exposed places. compounds. 'rile copper particles, with their great ratio of surface to The If. €1. Robertson Company, manufacturer of protected volume, had reacted wit11 the magnesium chlorido in the inetal building matepresence OS a i r t o rials, in the course of form the basic cupric an investigation of chloride (1.9). weather-resistant. inFollowing the disorganic coatings, reccovery of the henefit o8nized the possil.dithat results from the ties offered by maguse of copper powder, n e s i u m oxychloride a comprehensive cements arid initiated study was made of all a p r o g r a m oi r e the factors invuived search to correct in the new compositheir faults. It Betions. came evident as the Materials work progressed that these cements could MAONESIA. C o m niereial "plastic" or not be considered fit ' ' B B U S t ic " calcined for severc expoxire, magnesia f r o m the FIGURE 3. PIX~TOXICROQRAPHS OP COPPEE PARTICLES IN CEMENTS I x 1300) even though carefully California deposits of prepared and in spite of all known methods
FEBRUARY,1937
INDUS'CHIAL AND ENGI NEERING CHF:IISTRY
125
drites (Figure 4), the latter ost,inrste must be increa.ied severs1 fold.
1.93 9.54 2.20 2.77 82.82 0.68 1.25 2.18 0.72 80.66
sieve snslyds: Pnasina 80 mesh Passing 100 mesh Peesing 150 meah PBwing 200 mesh P-ing 270 mesh
Designation
NO.
1.7%
1.31 0.72 2.62 93.25 0.83
0.93 2.32 0.95 91.87
89.5 97.6 P2.i 82.1 71.8
Apparent Partiole Diam. at Point ssmpie of Separation. No. Micron8 Eieotrolvtia Pnwderx
96.6 92.8 85.3 72.1 64.0
% bX
We$htt
Finer t sn o m
where Separution Was Made
2
3
4 5
6
76.8 66.0 81.4
81.4 97.2
M~.QNESIUM CmoaxDE. Solutions were made up to the desired concentration (expressed as degrees BaumC) from the readily soluble Aakes of the hexahydrate supplied by the now Chemical Company. A 22' 8 6 . solution contains 41.5 per cent by weight of the hexahydrate or 19.4 per cent of anhydrous magnesium chloride. For 24" M.the corresponding percentages &re45.8 and 21.5, respect,ively. COPPERPOWDER. The metal obtained from a number of m m e s was of two general types, "electrolytic" and '%rment." The Erst is the product of a special electrolytic cell from which copper of high purity is removed as a fine powder, which is then dried in 8 reducing atmosphere and screened. The so-called cement eoppor is formQdby cementation of the copper content of leach liquors upon scrap iron (S, $1). The crude precipitate eontains some impurities as well as coarse particles of copper. The large copper particles are readily removed by sett.ling, and the impurities are removed by a dilute sulfuric acid wash, yielding copper powder of the followingpercentage composition (dry basis): Copper Iron
94.81 0.1
SUiiUi
Insoluble
.
I
63.0 80.0 80.0 86.6 29.0 91.0 49.2 85.0 57.2
1
Aggregates The same philosophy of aggregate grading applies for oxychloride cements as for other cements. I n the case of oxycliloride cements, however, the grading of the aggregate particles must be extended to extreme fines because the magnesium oxide, left porous by the escaped carbon dioxide, apparently reacts completely instead of leaving unreacted cores that serve as fine aggregate in the case of Portland cement compositions. The c o m p o s i tions reported in t h i s article were confined mostly t o all-silica aggregate m i x t u r e s . Commercial sands and p u l v e r i z e d sand w e r e blended to produce p a r t i c l e size gradings that c o n f o r m e d as closely as possible to t.he theoretical best from the standpoint of comc o w t e s y , -' .. n a c t n e s s . work.___ , _...~
0.06 0.35
Inasmuch as the reaction of the copper powder with its environm'ent is a surface phenomenon, its r5t.e ail1 depend upon the ratio of surface to vohme. Alt,tmugh t h i s ratio depends upon the siae of the particles, it does not bear the relationship that might be cxpeeted. Thls is robably because of the fact that the particlos obtained by eleetro&ic precipitation 011cementation are irregular dendrites whose surface does not increase, upon division, as rapidly as it would in the case of spheres. Classification of the copper powders as to particle size was accomplished in a rnodificd P a r s o n elutriator @la). Data for seseral powders are given in Table 11. Tho enormous suriaec represented by suoh fine powders is better understood from calculations ihat show that one pound of powder (which, for convenience, is assumed to consist of solid spherical particles 8 microns in diameter) coutains 1%) billion psrticles with a total surface of 410 square feet. As the part,ioles R R not solid spheres but are extremely irregular den-
%
-Le.,
a continuo'usly graded system in which "the ratio of the fraction retained on any one sieve to that retained on the next smaller, differing in mesh dimension by the square root of 2, is 1.1 ( 2 ) . The size of the coarsest sand was determined by the use to which the composition w &put. ~ Two gradings were employed; that used in sprayable compositions all passed 48 mesh, that in troweling compositions passed 14 mesh (Table 111). T.&BLE 111.
PARTICLE SIZE f)tJTlllBUl'IoN OF
MIXTURP~
Retained OB: 20 mesh
No. 1"
No.2b
..
14.1
..
9Y" ", . . .a.s,>
AoGREoa.rE
36 E"& .. 48 mesh 65 nicnh @I6 100 meah 24.0 150 mesh 21.8 200 mesh 16.8 Passing 200 mesh 27.0 Smaller than 24 miorana idetd. by elutristioa) . * 2 parts hsndiog sand. I part pdverimd sand. b 1 pmt ioek ahnd, 1 part river ssnd, 1 part pulverized sand, 0.5
.
U R
5.5
9.2
14.1 16.6
1.5
10.4 18.3 13.0
part talc.
Methods Experiniental compositions were carefully proportioned by weight and mixed in a 10-quart laboratory mixer. Plastic magnesium oxide, copper powder, and any other admixture were first mixed dry with the aggregate, which had been p r e mixed and kept on hand in large quantities to mure constancy of grading. The dry mixture was then gaged with magnesium cliloride solution, mixed one minute, and used for the several purposes described in the following paragraphs. Test specimens were stored during the first 24 hours in a room where the temperature vasmaintained betmen 75" and 80"F., and the relative humidity wns between 65 and 75 per cent. The following paragraphs describe the methods of testing and record the data on the effect of added copper upon the cement with respect to physical properties.
126
INDLSTHIAL AND ENGINEERlhG CHEMISTRk
VOL. 29, N O . 2
Strength
humidity, the briquets were stored over calcium chloride for 24 hours immediately prior to breaking. When the tensile strength of wet cement was determined, the briquets were immersed in water for 24 hours prior to the test. I n all tests the values in the following tables represent an average of two or more specimens. Owing to the plastic and homogeneous nature of the cements, the specimens were quite uniform and checks were close. The increase in 30-day tensile strengths (measured dry) due to copper powder was determined by adding copper powder NO. 1 in various amounts to a base mixture consistiiig of 20 per cent plastic magnesia X o . 1 and 80 per cent aggregate mix No. 1, then gaging to standard consistency with 22' BB. THE SMALL NUMERAL5 magnesium chloride solution. The results are shown graphiREFER T O THE NUMBER cally in Figure5 . OF COMPO3ITION3 For the purpose of tracing the progress of the development of strength in compositions that contain increasing amounts of copper powder, the latter (No. 6 represented by sample 3) was added in the indicated proportions to a base mix which FIGURE 5. EFFECT OF COPPER Poncontained 15 per cent plastic magnesia No. 1 and 85 per cent DER ON TENSILE STRENGTH .(DRY) a g g r e g a t e No. 2. The data (Figure 6) include the tensile strength determined both dry and wet. Although the data f o r t h i s series are a v a i l a b l e only for the initial 3 0 - d a y period, the results for other series (Figure 7) illustrate the long-time c h a r a c teristics typical of compositions both w i t h and without copper powder. No increase i n wet s t r e n g t h of ordiL I I I I I I I I I I I n I I I nary magnesium 10 20 40 10 20 30 LO 20 30 LO 20 30 LO 20 X, oxychloride cements AGE I N DAYS occurs after 30 days, F I G U R E 6. P R O Q R E S S OF STRENGTH DEVELOPMEN'P I N COMPOBITIONS CONl'hINING V A R I O U S PERCENTAGES whereas in the case OF COPPER POWDER
Standard Wets for s t r e n g t h determ i n a t i o n s were made in brass and stacked On the laboratory in a mallner t h a t air had to sides* They were broken after the indicated interval in an Amsler testing To a v o i d any effect due t o e x t r e m e differences in
OF STRENGTH DEVELOPM~NT IN COMPOSITIONS WITH AND FIGURE 7. PROQRESS
WITHOUT
COPPER
FEBRUARY, 1937
1NDUSTRIAL AND ENGINEERING CHEMISTRY
of the copper-bearing compositions i t steadily increases over long periods. The effect of copper in various amounts upon the performance of the resulting cement with respect to loss in weight and strength due to immersion in boiling water was determined as follows: Copper powder No. 1 was added to a base mixture consisting of 20 per cent plastic magnesia No. 1 and 80 per cent aggregate No. 1. The resulting cement was cast into slabs measuring 0.25 X 4 X 6 inches, which, at 30 days of age, were dried overnight a t 110" C., weighed, and immersed in large volumes of frequently changed boiling water for the indicated intervals. They were then removed, dried again a t 110' C., weighed to determine loss, and again immersed. As indicated by the data presented graphically in Figure 8, the loss in weight upon continued boiling became negligible after 100 hours, whereas the slabs which contained no copper powder had disintegrated. After 270 hours the slabs were broken to determine modulus of rupture with the results shown.
127
5
8
E
g4
Ei2 iz
5
b
B
K
w
3
6
5 i4.
0
2
Linear Change Linear changes, taken as convenient indications of the changes in volume in cement compositions, were measured with the apparatus shown in Figure 9 for more than eight hundred experimental mixes that have involved 28,800 measurements of 4800 specimens : The eyepiece of one microscope is equipped with cross hairs and that of the other microscope with a Filar micrometer. Polished brass tabs, bent at the corners, are pressed into the fresh cement and at initial set are scribed lightly with two razor blades spaced in a holder. The device is stored in a constant-temperature room and checked by a reference bar of Invar. One division of the Filar micrometer represents 0.0024 mm. or 0.00095 per cent of the length between the reference marks. This device makes it possible to study changes in linear dimensions of thin coatings as well as of inch prisms and to take the first measurements at initial set. The data indicate that the addition of copper powder to cement compositions that normally expand prevents their expansion and instead produces a slight contraction (0.01 to 0.04 per cent). Its use in compositions that would normally produce shrinkage has no effect upon the amount of that shrinkage.
Z U I
;
~
~
~
;
~
COPPER(PER CENT a/ WEIGHT)
~
$
~
FIGURE 8. EFFECTOF COPPERPOWDER ON Loss IS WEIGHT AND ON RESIDUAL STRENGTH OF THINSLABE
had been added the indicated percentages of copper powder No. 1. The first series employed a plastic magnesia which produced expansion while the second produced shrinkage. These data are regarded as typical.
Tolerance of Lime
Lime produces severe damage to ordinary magnesium oxychloride cements, both through excessive expansion and reduction in strength (6, 24). To determine the extent to which copper powder prevents this damage, lime was added in several percentages to magnesium oxychloride compositions which consisted of 20 per cent of plastic magnesia No. 1 and 80 per cent aggregate KO. 1, and also to similar TABLE Iv. EFFECT OB" COPPER POWDER UPON LINEAR CHANGES compositions to which had been added 10 per cent of copper IN CEMENT powder No. 1. All were gaged to standard consistency with Per Cent Co er Storage '-- Linear Change, Per Cent of Length-22' BB. magnesium chloride. The effect of the copper in A$&d Condition 1 day 3 days 10 days 30days 90 days restraining the expansion normally produced by lime is shown Expanding MgO in Table V. The strengths developed by these compositions 0 Lab. 0.064 0.066 0.061 0.035 70% R . H . " 0:072 0.089 0.088 0.087 0.114 are given in Figure 10. From these data it appears that 1.58 Lab. 0.044 0.048 0.044 b 10 per cent of copper powder offsets the damage to strength 70% R . H. 0:050 0.039 0.048 0.047 0,053 produced by 2 per cent of lime, and that excessive expansion 2.35 Lab. 0.025 0.028 0.023 6 7 0 % R . H. 0:034 0.024 0.028 0.022 0.028 is eliminated. A further indication of the increased tolerance 3.0 Lab. 0.037 0.052 0.032 b of lime due to the use of copper powder is the effect of the 70% R. H . 0:060 0.050 0,037 0.045 0.044 5.0 Lab. 0.032 0.036 latter upon cement compositions which contained 20 per cent 0.025 b 7 0 % R . H. 01058 0.043 0.035 0,033 0.035 of selectively calcined dolomite and 80 per cent of aggregate 10.7 Lab. -0,026 -0.048 -0,043 b 70% R. H. o:oio -0.014 -0.037 -0.035 -0.036 S o . 1. The dolomite had been calcined a t a temperature Shrinking Oxide that theoretically produced magnesia but no lime (13, 35, 26). 0 Lab. -0.048 -0.038 -0.058 -0.071 Actually some lime was formed, however, and the composi-o:oia -0.017 0,004 0.005 -0.006 70% R. H. tions containing no copper powder expanded to such an ex7.0 Lab. -0.053 -0,070 - 0 , 0 7 0 ,. 70% R. H. 0:ois -0,017 -0 011 - 0 . 0 0 7 .. tent that the briquets disintegrated within a month (on the Relative humidity. shelf). Identical compositions to which had been added 10 Removed for use in another experiment. per cent copper powder gave a tensile strength a t 30 days (dry) of 707 pounds per square inch. The linear changes in these compositions are shown in Figure 11. The data in Table I V show the effect of additions of copper powder on cement compositions. Linear changes were measAdhesion to Other Hydraulic Cements ured of magnesium oxychloride compositions which consisted of 20 per cent plastic magnesia ?So. 1 and 80 per cent Indications of the effect of copper powder upon the physical aggregate N o . 1 and also of similar compositions to which characteristics of magnesium oxychloride cements, particularly , ,
O
~
INDUSTRIAL AND ENGINEERING CHEMISTKY
128
VOL. 29. NO. 2
magnesium oxychloride cements which contained 20 per cent plastic magnesia No. 1 and 80 per cent aggregate No. I, and had been gaged to standard consistency with 22" B& magnesium chloride, and also with the same composition to which had been added 10 per cent copper powder No. 1. After 30 days (under damp towels) two briquets of each of the combinations were tested. The remainder was stored alternately wet and dry for 7 months before testing. During that time the bond between the hydraulic cements and the ordinary magnesium oxychloride cements wm destroyed. The cements to which copper powder had been added gave t.he results shown in Table VI. 'rnrLE
VI.
EFFECT OF COPPER POWDER UPON PERXANENCT OP
BONDTo HYDRAULIC CEMENT MORTARS
Age of Mortar When Mag?wiurn Onycl~londe cement was Cast Dora
1 2
Flounr: 9. DEVICEEOR MEASUHIN~ LINEAR CHANQE
7
upon their tolerance of linie, suggested the possibility that the new cements would form a bond to Portland and other hydraulic cements that would not he destroyed by water. Accordingly three series of composite briquets were prepared as Follows: An ordinary Portland cement, a high-early-strength Portland cement, and a high-alumina cement were mnde into mortar with three parti; of sand and cast into one end of a briquet mold. When these mortars had reached 1, 2, and 7 days nf age, the other half of the briquet mold WBS filled with TABLEv
-
EFFECT OF
-. Tensile Os OH), Strength Storage Aided (Dry) Condition 70 Lb./sq. in.
COPPER POWDER UPON
1 2
7 1 2
Megnasium Oxychloride cemeut
% --Pounds/spuoia inchPortlarrd Cement blartar 1n.o ?70 440 0 212 0 10.0 260 328 0 298 n 10.0 412 398 n 350 0 Itigh-Early-StienXtli Portland f:enient Mortar 10.0 468 340 0 511 0 10 0 363 n n 376 n 10.0 585 343 0
IIiEh-dl",niila Ceiliellt 10.0 0 10.0 0
7
LIME 'I(0LERANCE
Tensile Stre"@ of Composite Briquet After 7 mo. alterAt 30 dsys n ~ t e l ywet snd dry
10.0
n
446
n
MMOiLSi
78
215 0
0 448
645
490
n n
0 220
n
Effect of Other Factors
8u-UF.Y
After establishing the optimum amount of c o p per powder and tlir physical properties of the cement that result from its addition to the basic Cotiipositions containinz N O copper mag.nesiurn oxychloride compositions, it seemed 3.3s zoo Lab. 0,049 0.172 0.182 Diecontinuad pertinent to redetermine the effect of variations 70% R. €1. 0:UiG (LOG4 0.136 0.097 Disaontinued in the arnorints of the three oomponents-mag9.0 U Lsb. --0.012 0.089 0,127 Dieoontinmd 70% R. €1. 0:OiZ 0.009 0.012 0.001 Discontinued nesia, magnesium chloride, water. Accordingly 10% Copper Powder Added t u Componition several series of cement compositions were tested 3.00 185 Lab. 0.0% n.nwa 0.006 -0.002 70%R. H. 0:0& 0.028 0.0iB 0.019 0.036 in which only the component to he studied was 4.38" 398 Lab. 0.018 -0.044 -0.028 -n.n32 varied. o:oi7 n~mz 0.040 0.038 0.061 70% R. 11. The effect of variations in the amount of plasThese poraeatages are lower t h a n thore nhove on ncouimt of the weight of the admired DPPPC'. tic maenesia is shown in Tables VI1 and VI11 For se&d series that involved several basic st0 mixtures and copper powders. Variation in t h o ainount of magnesium chloride introduced into the cement can be made by changes in the concentration and also in the amount of the solution used. Obviously the effect upon the cement is not the same because of the different amounts of water introduced. Accordingly, series of conipositions involving variations both in the concentration arid the amount of the magnesium chloride solutions were studied. The findings are given in Tables 1X and X. I day
Lina&rChange. Per Cent of Length3 days 10 days 30 d w a 90 dam
Oi
"e\lc]...~~! j.. 1 -m.,I-m:m]
Effect of Oxidized Films on Copper Particles C,opper particles sI:low-lylose their brightness upon exposure to air, partienlarly to damp air, and develop a mahogany color. Thi3 dark film has been sliown (9,$7) to consist of a mixture of copper arid cuproiis oxide. Further change takes place slowly, but eventually the copper particles become blackcncd hy the formation of a surface film oi cnpric oxide. The effect of thrse staR(;r:sof oxidntion upon the usefulness of
FEBRUARY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLEVII. EFFECTOF PERCENTAGE PLASTICMAGNESIA ON CEMENT COMPOSITION Aggregate Plastic Mixture Magnesia Per cent by weight 10% Copper Powder 90 10 85 15 82.5 17.5 80 20 10% Copper Powder 15 85 17 83 20 80 a
Mol. Ratio, Tensile Strength NgO/MgClz (Dry) at 30 Day8 Lb./sq. in. No. 1 AddedQ 2.72 1350 3.68 1622 4.53 1182 5.75 1320 No. 6 Addeda 4.62 1232 4.45 1730 5.73 1188
129
Adhesion of the cement to another material is remarkably improved by rubbing the surface of that material with a slurry that contains a high percentage of cement. This procedure ensures complete wetting of the surface and provides a strong layer of cement in contact with it. The cement compositions are colored blue green by the formation of the artificial atacamite; 0.12 per cent iron oxide red, complementary to this shade, changes it to stone gray. Blues, greens, reds, browns, and blacks may be obtained with the proper pigment simply by obscuring the blue green.
The whole was gaged to standard consistency with 22' BB. MgC12.
TABLEVIII. EFFECTOF PERCENTAGE PLASTIC MAGNESIA ON STRENGTH OF CEMENT' Age Dags
1 3 5 8 10 14 30 90
C--Tensile --Compn. AbDry Wet
445 727 785 1063 1155 1158 1460 1165
...
390 485 498 640 593 628 967
Strength--Compn. Dry
BOWet
568 733 750 1045 915 1315 1405 1550
415 453 653 537 610 590 985
...
a Ten per cent of copper powder No 6 added and the whole gaged to standard aonsistenoy with 22' BB MgCh 6 A . 15% plastic magnesia No. 2, 62.75% aggregate No. 2, 1225% talc: mol. ratio MgO/MgCle, ,4.40. C B. 20% plastic magnesia No. 2, 68% aggregate No. 2, 12% talc: mol. ratio MgO/MgClz, 5.35.
the copper powder was next studied. To a basic mix consisting of 20 per cent plastic magnesia No. 1 and 80 per cent aggregate No. 1 were added copper powders that were in various states of surface oxidation. Other copper powders were added to a second basic mix that contained 20 per cent plastic magnesia No. 2 and 80 per cent aggregate ?To. 1. The strengths and linear change characteristics of the resulting compositions are shown in Table XI.
Accelerated Weathering Tests and Trial Installations
AGE IN DAYS
FIGURE11. EFFECT OF COPPER POWDER IN ELIMINATING THE EXCESSIVE EXPANSION OF AN UNSOUND CEMENT
The conversion of the copper cannot take place in the absence of either water vapor or oxygen in the atmosphere, and its rate is influenced by their concentration. Strong sunlight retards its formation, while exposure to ultraviolet light appears to prevent it during the interval it is exposed. In general, high humidity and darkness produce bluer, and low humidity and sunlight produce greener shades. The effects upon rate of formation and shade of the cupric oxychloride are only temporary, and exposure to similar conditions soon erases differences due to early history.
Many accelerated tests have been devised to show the performance of the copper-bearing magnesium oxychloride cements under severe conditions and to compare them with compositions which contained no copper. A few (Figures 1, 12, 13, and 14) were selected because they reveal the weakness of the original compositions and demonstrate how it was corrected. The most significant proof of the extraordinary TABLEIX. EFFECT CONCENTRATION OF MAGNESIUM CHLORIDE SOLUTION ON CEMENT COMPOSITION^ changes in the cement is the performance of acConcn. Tensile tual floors, coatings, paints, and stucco that of Strength Aging at 30 Days Storage -Linear Change, Per Cent of Length-have been made from the various compositions Soln. (Dry) Condition 1 day 3 days 10 days 30 days 90 days intended for the uses described later in this B1. Lb./sq. in. paper. More than 200 tons of these compositions 18 1053 Lab. -0.064 -0.081 -0.080 -0.038 70% R. H. -0:630 -0.049 -0.078 -0.064 -0.044 have been installed.
Supplemental Observations The copper powder has no appreciable effect upon setting times and introduces no changes in the practice ordinarily employed in handling, placing, and curing magnesium oxychloride compositions. Its particles are so small that settling does not occur. Workability is usually improved. No particular advantage results from using copper powder in compositions that contain a high percentage of wood fiber or other material that is affected by water, for obviously both binder and aggregate must be waterproof.
20
1200
22
1152
Lab. -0.039 -0.053 -0.064 -0.052 70% R. H. -0:620 -0.022 -0.052 -0.040 -0.016 Lab. -0.029 -0:032 --O 048 -0.044 70% R . H. 0:003 -0.010 -0.009 -0:004 -0,014 24 1383 . Lab. -0.019 -0.039 -0.045 -0,036 70% R. H. o:ois -0.003 -0.031. -0.024 -0,004 26 1272 Lab. 0.000 -0,024 -0.034 -0,026 70% R.H. 0:636 0.011 -0.020 -0.008 -0.009 28 Lab. 0.014 -0.010 -0.031 -0,015 1357 70% R. H. 0:637 0.048 0.045 0.035 0.052 30 Lab. 0.022 0.009 -0.00'2 -0.006 897 70%R. H. 0:637 0.048 0..048 0.045 0,045 36 462 Lab. -0.012 -0.034 -0.032 -0.034 70% R. H, 0:007 0.008 0.012 0.017 -0,006 a To a series of identical compositions consisting of 20% plastic magnesia No. 1 and 80% aggregate No. 1 was added 10% copper powder No. 1, and the resulting dry mixtures were gaged to stindard consistency with volumes of MgClz solution of the indicated concentrations.
FiovnE 12 ( T o p ) . RENEFITR E ~ U L T IFROM N ~ COPPERPowom 'The oxychloride aeinent cylinder8 were made from identical oompogitions except that the cyIinder on the left containg 5 per rent copper powder. Both orimdera were filled wrth rater at 14 days 01 w e . The cylinder containing no o o ~ p e pqwdar i ahown the type 01 falluic tyDiod of these cementr due to their solubility and the dwuntive V O I changes U ~ that oocui when r e t . FIaliHE 13 (C"snle7). W.
