T H E J O U R N A L O F I N D G S T R I A L A S D ENGIL\TEERI_VG C H E M I S T R Y limitations imposed deliberately and consciously b y Ostwald. Once these are broken through, nobody will have a n y cause t o complain of the wave having spent its force.” Stewart further says: “ I t is a n extremely fortunate coincidence t h a t as t h e first movement declined, a second a n d perhaps more powerful one had succeeded it. This second movement rose with even greater rapidity t h a n pure physical chemistry, a n d yet a t t h e present day we appear t o have touched only t h e fringe of t h e subject of radioactivity; so t h a t we may look forward t o a long career of fruitful investigation still before us in this department of chemistry.” The problems of sub-atomic or electronic universe have presented themselves a n d a t once we begin applying these new ideas t o utilitarian purposes. The cryogenic laboratories have accumulated fractions from tons of liquefied air. Collie found t h a t t h e neon. obtained t h u s incidentally, luminesces under t h e influence of t h e Hertzian waves. A tube of neon serves as a detector of t h e nodes a n d loops, glowing brilliantly under t h e influence of t h e latter, as if it were excited b y a n induction coil. Claude’s tubes of neon thus excited, offer a most pleasing light a n d perhaps later on will prove t o be an economical source of artificial illumination. Quantities of argon are now available from liquefied air. There are indications t h a t , on account of i t s inertness, we m a y shortly see tungsten incandescent lamps, as Whitney puts it, with “ t h e vacuum jam-full of argon” instead of nitrogen. Troost a n d Onvrard have stated t h a t they had succeeded in causing argon t o combine with magnesium vapor. Neither Rayleigh, Ramsay, nor Moissan were able t o secure a n y evidence of t h e formation of compounds of argon, however. Many reactions unobserved on t h e laboratory scale are found t o occur when dealing with large quantities of substances, through long periods of time. If this were not true we should have even greater difficulty in accounting for t h e occurrence of such inert gases as helium in malacome, clevkite and thorianite. It is thus barely possible t h a t in time we shall find compounds of argon produced in t h e large scale operations of burning t h e nitrogen of t h e air, as carried on so successfully in Korway
f
Vol. 6 , KO. 3
a t present. h use of compounds of argon may then be found. The development of radioactivity has projected us into an undreamed of realm of thought a n d new interests. The phenomena of radiology are closely allied t o those of radioactivity. The use of Rontgen rays in medicine has been attended b y not a few difficulties. Among them the so-called “hardness” a n d “softness” of the rays. The former are penetrating a n d affect tissues far below t h e surface, sometimes favorably and sometimes unfavorably. The “soft” rays affect t h e epidermis. I n t h e use of “ h a r d ” Xrays tubes for deep treatment, i t is necessary t o screen t h e skin with various thicknesses of aluminum, or lead, etc. For treatment of skin affections only, there have been no satisfactory means for screening out t h e penetrating rays, consequently a problem has been t h e production of “soft” rays with a minimum of “ h a r d ” rays. X-ray tube glass is usually a potash or sodalime silicate. Lindemann found t h a t b y substituting lithium for potassium t h e rays were “softer.” H e then substituted beryllium for calcium, and finally boron for silicon. Lithium-beryllium-boron-glass shows over thirty per cent reduction in t h e empirical molecular ireight. Windows of this glass let into X-ray tubes give t h e “soft” rays desired. It would be interesting t o see the effect with a potassium-barium-zirconium-glass. Application of t h e newer electronic conceptions of valence, especially when associated with residual affinity with the development of methods for changing valence according t o our wishes, will unquestionably cause many of these unused elements a n d many of those now most used t o assume new properties. A t tention m a y be directed t o one qualitative illustration. Pure lead does not plate on iron. When molten lead is caused t o flow t o and fro as a conductor of a lowvoltage high-amperage alternating current for variable periods of time, usually several hours, i t then plates iron, as may be seen from samples very recently so plated under t h e supervision of t h e writer. While t h e process is not perfected, it points a way which m a y serve as a hint in seeking uses for such elements as cadmium, selenium, a n d tellurium. CHARLESBASKERVILLE
ORIGINAL PAPERS PAINT FILMS A S PROTECTIVE COATINGS FOR CONCRETE. By E. E. WARE A K D S. M. S C H O T T ~
Received December 9, 1913
T h e extensive use of concrete as a building material for all types of construction has naturally been accompanied b y numerous failures of greater or less importance. These examples have been seized upon b y manufacturers of competitive material a n d have been brought t o t h e attention of t h e public through wide publicity, causing a doubt t o arise in t h e minds of some as t o t h e permanence of concrete construction. 1 Holder of Paint Fellowship, Acme White Lead and Color Works, 1911-1912.
However, with t h e better understanding of t h e possibilities and t h e limitations of this material, it has been possible t o very nearly eliminate t h e causes of failure t h a t were mainly responsible for t h e difficulties experienced b y t h e pioneers in t h e use of concrete construction. But we are confronted b y a cause of disintegration still little appreciated b y t h e concrete engineer-lack of constancy of volume in concrete after setting. Although t h e tendency t o failure from this cause is more, apparent in stucco and other light construction, where mixtures rich i n cement are used, monolithic work is b y no means free from the effects of this lack
Mar.. 1914
T H E J O C R N A L OF I N D C S T R I A L A S D ENGINEERIlYG C H E M I S T R Y
of constancy of volume, a n d we find failure cracks whose presence can be accounted for only b y t h e assumption of a differential expansion in the different members of t h e structure. White' has shown t h a t t h e changes in volume due t o changes in temperature are small as compared t o the changes due t o t h e alternate wetting a n d drying of t h e concrete, a n d t h a t these latter changes are sufficient t o cause failure in m a n y cases. Figs. I a n d z show representative failure cracks of this type. Another source of trouble in which water plays a part, is t h e electrolytic effect of stray currents on t h e steel reinforcement in concrete. This corrosion of t h e reinforcement could not t a k e place in perfectly dry concreteG2 The elimination of these two causes of disintegration in concrete is strictly a problem in waterproofing. Waterproofing materials for use with concrete are divided into four general classes: membrane, integral, surface washes, a n d oildpaint films.
185
use of t h e somewhat less efficient b u t more suitable paint film. Without doubt paint films can be compounded t h a t will be practically impervious t o water; b u t they must, in t h e case of concrete coaters, be also able t o stand the saponification action of lime leached out from the concrete, as well as be insensitive t o t h e attack of the weather. Manufacturers have made attempts t o solve the problem of putting out a satisfactory concrete coater; b u t there has been a decided tendency t o lose sight of t h e fact t h a t first of all t h e paint must be of such a nature as not t o lose its elasticity or impermeability through the influence of the weather. T h e paint must possess all of t h e weather-resisting qualities of a n y paint designed for outside work, in addition t o being able to meet t h e conditions peculiar t o this particular service. Concrete coaters may be classified in general: ( I ) coaters compounded from materials inert to the action
Courtesy of
Prof. A . H . White
FIG.1
Wig a n d Bates3 have made a n extensive study of waterproofing materials, a n d their work seems t o show t h a t none of t h e integral or wash waterproofings are efficient in preventing t h e absorption of moisture, although they may prevent t h e percolation of water through t h e concrete. Recent work4 seems t o have demonstr&ted t h a t volume changes are caused b y adsorbed water, a n d t h a t t h e presence of waterproofing within the concrete has very little effect upon t h e ultimate percentage change, a n d t h a t its only effect is t o retard t h e rate of absorption. T h e use of a n impermeable membrane on the exposed side of t h e concrete would very efficiently prevent t h e passage of water t o t h e concrete, a n d would, therefore, prevent the resultant disintegration due t o either moisture, volume changes or t o electrolysis. However, in t h e majority of cases it is not feasible to use a n asphalt felt membrane, so we are limited t o t h e Proc. A m . Soc. for Test. M a t . , 1911. Rohland, Wasser u. Abwassrr, 6 , 504. 0. Berndt, Beton u . Eisen, 11, 1st Supplement. C. de Wyrall, Proc. Int. Assn. Test. M a t . , 2, 20. a Bur. Standards, Technologic Papev 3. 4 White, Private Communication. Jesser, Tonind. Ztg., 37, 535-8. 1
1
of alkali; ( 2 ) coaters whose vehicles carry considerable amounts of free organic acids; (3) coaters compounded with t h e idea of getting a hard a n d perfectly impenetrable surface; (4) those coaters whose virtue lies mainly in t h e elastic a n d only slightly permeable film formed from t h e good drying oil which constitutes t h e major portion of t h e vehicle. T h e first class m a y contain neutral gum varnishes, petroleum products, may be of a casein base, or may be made up from a cementing pigment. Experimental d a t a as well as practical experience with paint films for general service work have established t h e fact t h a t t h e vehicle for a n y paint should be selected with a view t o getting t h e maximum of elastici t y in t h e dried film, recognizing t h a t a n y additions t h a t t e n d t o harden t h e film will, a t the same time, increase t h e brittleness a n d accelerate the disintegration. Paints of t h e second class are quite common and appeal strongly t o the average user, inasmuch as t h e free acid is supposed t o serve the double purpose of neutralizing a n y lime t h a t m a y be present and a t t h e same time sealing t h e pores of t h e concrete with the
T E E J O U R N A L OF I N D U S T R I A L, A N D E N G i N E E R I N G C I I E M i S T R Y
186
precipitated lime soap. The free acid of this type of paints is sometimes an added f a t t y acid, and sometimes the unneutralized resin acid of a varnish mixed with the oil as a constituent of the vehicle. Cathcart' claims t h a t the soaps used in water-
C o w I 6 m of Prof. A . H . While Pili. 2
proofing have a disintegrating influence on iinoxyn. This will apply as well t o the insoluble soaps formed in the neutralization of the lime by t h e free fatty acid of the second type of coater. I n a n attempt t o determine t h e extent to which the reactions take place when a coater of this type ir
Fio. 3-enom
OP 32 PANBLS
1
Conrrrir and Cond. Eng.. 1, 380-7.
No. 2 . The same oil t o which harl been added a small amount of f a t t y acid. No. 3 . The same oil t o which had been added 20 per cent of rosin varnish containing a considerable amount of unneutralized rosin acid. Each of these samples of oil was shaken a t intervals for three weeks, with three different pigments, calcium carbonate, calcium hydrate, and Port,land cement. To each of these was added about I O per cent of water, and the whole was diluted to doublc its volunic with kerosene. A fourth sei was shaken with dry Portland cement. Table I shows t h a t t h e acid constituents act as completely on Portland cement as they do on calcium hydrate, while they act very slowly on calcium carbonate and unhydrated Portland cement. Assuming the same conditions t o hold under actual conditions of service, there will he an action between the acid of t h e coater and the cement a t t h e surface of the concrete, which will give a film of lime soap a t t h e surface, t o which the paint film must cling. This action is all near the surface, for there is present within one-sixty-fourth inch of t h e surface of an ordinary concrete sufficient lime compounds t o neutralize all t h e acid content of the common cement coater. These coaters show themselves t o be inefficient as neutralizers, and the life of the film cannot he long
18" x 18" IN SUPPOXT~NG Fn~ars. R I E HAW ~ 0s
applied to a concrete or stucco surface, some samples of oil were subjected to parallel tests. The oils were as follows: No. I . R a w linseed oil.
1'01. 6 , No. 3
E~cx PANRLPAINTED GRBEN
when they have nothing better ovith t h a n a skin of insoluble soap. The impenetrable surface of t h e coaters is generally derived from a film, t h e vehicle of this coater being
which to bond third t y p e of gum hardened largely varnish.
Mar., 1 9 1 4
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY TIBLBI
On. IWD ACID
LIN8KBD 011
_-_-. original.. .........................
Calcium carbonate.................. Calciumhydrate .................... Dryeemenf ........................ wet ce.ent ........................
Acid 1.90 1.3 0.1 1.0 0.2
Sapon.
113.0 118.4 114.1 115.6 114.2
Iodine 122.2 123.3 122.6 122.3 122.6
OIL *ND
Acid 9.1 7.9
S~pon.
0.2
m4.7
114.s
4.7 0.3
1ns.n 1os.n
111.6 113.2
1ns.s 109.9
Iodine 111.1 111.9
Acid 6.7 6.1 1.2 2.7 0.4
,
VnanrsH
Sapon. ins.4 iin.8
.
Iodine 118.9 122.8
10s.s
125.8
109.4 103.1
125.4 125.6
The tests on iodine abemption were made as a more or less accurate check on the evapoiation of the thinner during shaking and centrifuging.
T h e paints of this class really possess t h e faults of both the first a n d the second classes, for t h e resins of t h e varnishes are at least in part acid, while as a whole t h e hard film is subject to t h e same accelerated disintegrating influences as affect any nonelastic film. With a n idea of studying t h e efficiency of the different types of coaters, a few of t h e more widely advertised ones were purchased, a n d together with some made up in t h e laboratory, were applied t o surfaces of concrete and stucco, a n d given a n exposure test t h a t has extended over about two years time. The exposure panels were each eighteen inches square a n d two inches thick, reinforced b y expanded metal, and held within a frame built u p from i/4 inch x 2 inch steel hand, t o insure t h e m against breakage. The hacks of t h e panels were covered with galvanized iron in order t h a t there should he no water entering from the hack of t h e panel, and t h a t t h e conditions should he as nearly as possible t h e same as those
.
.
.
.
.
.
.___
x.
-..
existing in a n ordinary structure. The paint films were subject, then, t o t h e saponifying action of only such lime as would leach out with the water t h a t might have passed through t h e film pores, or through cracks t h a t had developed in such films as were unable t o stand the weather. If a paint film be water-tight i t should he free from the action of lime just so long as it remains in perfect condition; b u t when i t begins t o
show cracks, t h e n with t h e access of water t o t h e underlying concrete and its subsequent evaporation from the surface, lime will he brought t o the under surface of t h e
film. In these tests, each paint was assigned t o two panels: one made up from a mix of one part cement t o three parts river sand, and one panel of a rich stucco mix, one part lime, two parts cement and five parts river sand. The panels were made u p indoors and allowed t o set for three weeks before the paints were applied. During t h e first two weeks of this time t h e panels were kept damp; b u t they were allowed to dry a full week in order t h a t there might not he present i n t h e concrete, when t h e paint was applied, moisture t h a t would prevent proper penetration of t h e paint a n d give a n imperfect bond between t h e paint film and the concrete surface. The second coat was applied after the first coat had become thoroughly dry, t h e time intervening varying from three t o seven days.
During t h e time of exposure, the panels were carried on a frame inclined about 20' from the vertical, with the painted surface of the panel facing south. Fig. 3 shows the complete group of panels with their supporting frame. T h e frame occupied such a position on the roof of the laboratory as would insure t h e tests being free from the influence of laboratory fumes. After having been exposed t o the weather for a
T H E J O U R , V A L OF I S D U S T R I A L A I V D E . V G I N E E R I N G C H E M I S T R Y
I88
period of one year, each panel was coated over one-half of its surface with a green paint whose pigment was a mixture of chrome ycllow and prussian hlue. This paint scrved 3s a very good indicator of t h e extent t o which lime Icached out t o the surface. the presence of lime being indicat.ed by a ycllow spot. I n order not t o influence the porosity of the underlying film too much, only one coat of t h e green was applied. In cases where the paint on the panel was disintegrated badly, an a t tempt was made t o prepare thc surface for the coat of green paint by brushing off the loosely adhering scales. Even thcn, in some cases the condition io'r painting was decidedly unsatisfactory. This emphasizes t h e importance of using in the first place, a paint which, upon disintcgration. r i l l prcsent a proper surface for
Val. 6, No. 3
closely enough characteristic t o warrant a classification according t o the type of disintegration. The paints for Panels Nos. 3 and I I carried, in addition t o the f a t t y acid, a small amount of cement as a constituent of the pigment. While tlie colloidal silica formed in this way may have been efficient in sealing the pores of the concrete, the fatty acid evidently affected t.he film, whose early disintegration would not permit. these films t o be classed as efficie,nt protection for concrete surfaces. T h e paints on panels Nos. 6, 14, 1 7 , 18, 19, 2 0 , 21, 2 2 , 3 1 and 3 2 depend for their efficiency on the presence of a neutral gum varnish. These panels all exhibited very carly disintcg-ration of tlie coater. This disintegration w a s . for the most part, characterized by
Frc. S-TYPICAL ILLOSTKAT~OS on SURFACI C o n o i r i a ~ . ABOUT 3 / r Sizs
repainting, for i t is a well recognized fact t h a t no paint coat can last indefinitely any more on concrete than on wood or metal. Ladd's' work has shown this t o be an important consideration in the permanent protection of wooden structures, and the Same conditions apply t o the protection of concrete. Table I gives a summary of the condition of t h e various panels a t the end of two years. Panels Nos. 3 , 1 1 , 4, 12, 1 5 and 2 6 were painted with coaters currying considerable amounts of f a t t y acid or unneutralized resin acid. The disintegration of these films was early and complete, and was not i
Bulletins of North Dnkotn Agricultural Experiment Station.
heavy scaling and flaking, which in some cases left parts of the panel entirely free from paint within a short time. Coater No. 5, on panels Xos. j and 13, was very heavy bodied a n d did not spread s i t all freely. The small amount of vehicle present was neutral in character, the material acting more like a cemcnt than a paint, there being littlc tendency t o form a true paint film. These panels retained their coats fairly well, although they a t all times showed a high degree of porosity as indicatcd by the tendency t o absorb any water applied to t h e surface. This coater might serve well as a decorative paint; b u t i t is probably of com-
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Mar., 1914
paratively little value as a protection t o the concrete surface upon which it may be applied. T h e coaters o n panels Nos. 2 7 a n d 28 help t o prove t h e contention t h a t non-drying oils do not make good substitutes for linseed oil in paints, for they were among the first to show a tendency t o disintegrate. The vehicles of the paints applied t o panels Nos. I , 2 , 7 a n d I j were made up very largely of drying oil, t h e content of varnish being small, a n d the mineral oils being confined t o t h e thinners. These panels were, t o all appearances, t h e most efficiently protected of a n y in t h e t e s t . This is true particularly of panels S o s . I a n d 2 , which were prime coated with mild TABLEI1
:i t:} i 1i z i iz} i: ti} z i :} ;i ;:} 1:
1:
6 6
7
7 9 9 10 10 11 11 12 12 13 13 14 14
15 15
4
Good
Good
3 yrs.
General bleaching
3
Gone
Very poor
4 mos.
Spotted
2
Very poor
Poor
8 mos.
Spotted
2
Very poor
Poor
8 mos.
Large spots
1
Fair
Good
2 yrs.
Spotted
Gone
Very poor
6 mos.
Not many spots
Good
2 yrs.
Free from spots
Very poor
4 mos.
Few spots
Gone
3 mos.
Disintegrated
Gone
3 mos.
Disintegrated
Gone
3 mos.
Disintegrated
Gone
3 mos.
No spots
Very poor
6 mos.
Few spots
6 6 1 , 14 52 , 7 66 57 15 43 3 6 )
:}
1: 17 18 19 20 21 22 23 24 25
26 27 28 29 30
:i z?}
51 70 55 48 63 48 58 49 30 25 27
.. 48 37
Fair
3
Gone
60
Gone
46}
66 59} 64 56} 50 45)
Gone Gone Gone
.. } , ,
,. , .
.. ..
}
Gone 1
Gone Gone
Poor
6 mas.
h-o spots
Fair
12 mos.
Iio spots
Very poor
6 mos.
Few spots
process white lead a n d oil a n d finished with a special outside white made up of a composite pigment, with t h e linseed oil vehicle carrying a small amount of varnish as a hardener. These t w o panels were subjected t o a n especially severe test, in t h a t t h e y were exposed a t t h e back during t h e greater part of t h e test, t h e protecting galvanized iron covers having been removed from these particular panels a t the end of three months exposure. This permitted water t o get in from t h e back of t h e panel, which, had t h e pores of t h e concrete not been perfectly sealed, would have caused a decided saponification of t h e linoxyn film, for the water would naturally have evaporated from t h e side of t h e panel exposed t o t h e sun, a n d in this evaporation would have deposited considerable lime within t h e film. H a d t h e lime come t o t h e surface in a n y quantities it must have saponified t h e film, as linoxyn is extremely
189
sensitive t o alkali,’ both sodium hydroxide, and calcium hydroxide attacking it in the cold. S U Mbf A R Y
Assuming water t o be a n important agent in the disintegration of concrete a n d stucco, there is a necessity for a system of waterproofing t h a t will prevent absorption. T h e film coaters most nearly fill such a specification, where the surfaces are to be a t all ornamental. N o coating compound can be successful t h a t will disintegrate under t h e influence of the weather. This eliminates from consideration a n y material t h a t would not be classed as a good coater when applied t o other materials t h a n concrete. Although linoxyn is readily saponifiable in t h e cold, there is not, under ordinary conditions, enough lime carried out b y the small amount of water t h a t may penetrate a paint film in good condition, t o cause disintegration of the film. This is emphasized by t h e fact t h a t the disintegration of t h e paint film under observation in this work is no more pronounced on a rich lime stucco t h a n on a cement sand concrete. T h e absence of stains on t h e green paint tests in the cases of some of the panels whose coaters showed disintegration a t the time of application of t h e green, would indicate t h a t the lime a t t h e surface of the panels had become pretty well carbonated during the first year. Any stucco exposed t o t h e weather for a year’s time can be coated satisfactorily with a good outside paint. A successful concrete coater should be compounded on t h e same basis as is used for a satisfactory outside paint for wood, with only such adjustments in composition as tend t o make i t more nearly impervious, a n d these must not be made a t t h e expense of t h e elasticity a n d general durability of t h e film. T h e panels of these tests are t o be repainted with the original materials, a n d a further set of experiments are in progress in which measurements of the expansion a n d contraction of the individual panels will be made. UXIVERSITYOF MICHICAK A N N ARBOR
THE COMPARATIVE VALUE OF A CALCIUM LIME AND A MAGNESIUM-CALCIUM LIME FOR WATER SOFTENING By EDWARD BARTOWA N D CLARENCE SCHOLL Received December 4, 1913
On the market there are limes made from calcium limestones a n d limes made from magnesium-calcium limestones. T h e latter is favored by masons because they think it has a smoother plasticity. T h e claim has been t h a t magnesium-calcium lime is as good as calcium lime for water softening. While we believed t h a t t h e claim for magnesium-calcium lime was unwarranted, we were glad t o make some laboratory experiments t o definitely settle t h e question for ourselves. We could find b u t little data concerning t h e effect of a magnesium-calcium lime for water softening. 1
Andes, “Drying Oil and Boiled Oil,” p. 33.
