if tho S 0 4" content bo high) into each of a series of flasks, suspend it in H 20 , and add increasing amounts of BaCl2 solution to each successive flask. After shaking and setting aside for 12 hr., each is filtered and tested for excess of Ba with H 2S 0 4. A suitable solution contains 10 g. of BaCl2,2H20 per 1. and 24 gm. of AlClj, which latter hinders adsorption of the
excess of Ba. G. H. C.
P r o p e r tie s of b r ic k s a n d t h e ir m o s t effective u tilis a tio n . H . Hech t (Tonind.-Ztg., 1938, 62, 207—212).—Strength, H 20 absorption, air- and H 20 - permeability, capillary attraction, tendency to show efflorescence, and the therm al conductivity of typical common bricks, light-weight and honeycombed bricks, engineering bricks, and clinkers are tabulated.
G. H . C.
M e a s u re m e n ts in b r ic k d r y in g s h e d s . W . Rot
(Tonind.-Ztg., 1938, 62, 233—234).—1The am ount of H 20 which can bo evaporated depends on the temp, and the am ount and initial H 20 content of the ingoing air. Allowance m ust be made for tho fall of temp, during passage due to latont heat and losses, otherwise deposition of H 20 m ay occur in places. Self-record
ing instrum ents assist in controlling these factors.
G. H . C.
D ry e rs fo r ro o fin g tile s . T. A. Go sk ar (Trans.
Ceram. Soc., 1938, 37, 62—73).—The principles and practical details of operating the dryers on waste heat from cooling kilns are discussed. A. L. R .
R e fra c to ry t r e n d s a n d d e v e lo p m e n ts [in th e U n ite d S ta te s ] in 1937. J . D. Su l l iv a n (Blast Furn. Steel P lant, 1938, 26, 64—67, 98; H eat T reat.
Forg., 1938, 24, 39— 42).—A review. R . B. C.
S in te re d m a g n e s ite . I I I . S in te rin g p r o ce sse s in m a g n e s ite s w ith u n e q u a l d is tr ib u tio n of tb e c o n s titu e n ts . K . Ko n o pic k y (Ber. Deut.
Keram . Ges., 1937, 18, 4 1 9 ^ 1 2 7 ; cf. B., 1937, 1051).
—A series of raw magnesites were coated in the lump form with various fluxing materials (CaO, F e20 3, S i02, slag, etc.) and calcined a t cone 17—18. Only those m aterials rich in 2Ca0,Fe20 3 and poor in S i02 caused a good sintoring throughout the magnesite lumps. This result is in agreement with tho observ
ations th a t raw magnesites sinter well only if their ground-mixturo consists of an isomorphous m ixture o f the carbonatcs of Mg, Fo, and Ca, and th a t the sintering behaviour of a magnesite is affected only slightly by tho presence of macroscopic pockets or soams of S i0 2, M g0,Si02, MgC03,CaC03, etc. which do not themselves sinter. Such unsinterod impurities may be removed from the crushed sinter by suitable (e.g., magnetic) physical treatm ent. J . A. S.
V o lu m e tric a n a ly s is of s ilic a b r ic k a n d q u a r tz - ite s . M. Volinetz (Ukrain. Chem. J ., 1937, 12, 507—515).—Analytical procedures involving known
methods are described. R . T.
A c cep tan c e t e s ts on re f r a c to r ie s . R . Rasch
(Chem.-Ztg., 1938, 62, 193—196).—Firobricks should be tested for size, and a proportion should bo cut to ascertain th a t th e tex ture is suitable and free from foliation, cracks or cavities caused by air, foreign bodies, moisture pockets, or shrinkage in drying or firing. Cracks are sometimes concealed by smearing
with clay or N a silicate. The latter is readily ren d
ered visible by phenolphthalein. The chemical com
position should also be checked, and this should include tests on tho raw materials. G. H. C.
B a s ic r e fra c to rie s , w ith p a r ti c u la r re fe re n c e to t h e i r u s e in tb e lin in g of in d u c tio n fu rn a c e s.
C. Booth and W. J . Ree s (Iron and Steel Inst.
Carnegie Schol. Mem., 1937, 26, 57— 122).—Additions of cordierite (2Mg0,2Al20 3,5Si02), up to 25%, to dead-burnt magnesite . lower, tho firing shrinkage, therm al expansion, and refractoriness-under-load, and increaso tho porosity, but have little effect on spalling. The tern ary diagram for Al20 3-M g 0 -S i0 2 is of little val. in interpreting m icrostructure, as equili
brium conditions are never attained. Tho best bonds for oloctrically fused, magnesite are CaF2 and Ca3(P 0 4)2. Increasing the moulding pressure reduces the firing shrinkage, porosity, permeability, and therm al sensitivity and increases considerably the greon strength and refractoriness-under-load.
S. J . K.
M e c h a n ic a lly s u p p o rte d r e f ra c to rie s fo r in d u s tr ia l h e a tin g fu rn a c e s . An o n. (Indust. H e a t
ing, 1937, 4, 916—922, 1007—1010, 1103—1108).—
Various designs of refractory arches and susponded
walls are described. R . B . C.
B o ile r fu rn a c e s . F lo c c u la tio n .—S e e l. E n a m e llin g F e . B a k in g e n a m e l on a u to m o b ile fr a m e s .—See X. In s u la tio n re s is ta n c e of c e r a m ic m a te r ia ls .—See X I.
See also A., I, 180, S tr u c tu r e of g la s s e s . 218, Id e n tific a tio n of g e m s . P r o d u c tio n of sy n th e tic g e m s .
Pa t e n t s.
K iln s. Sie m e n s- Sc h u o k e r t w e r k e A.-G. (B.P.
478,879, 21.7.36. G er" 10.6.36).—A mufflo or elec
tric furnace with a curtain of protective gas across the opening is provided w ith autom atic valves to tu rn on tho gas and bring tho nozzles in th e operative position only when the door is opened. B. M. V.
R o ta ry k iln s . M. Vogel- Jo r g e n se n (B .P . 479,459, 6.8.36).—Tho kiln is fired by an axial flame from tho lower end, secondary air being ad
m itted through the cylindrical wall through apertures provided with autom atic dampers which reduce or stop admission of air near the surface of the m aterial.
The secondary air is preheated by the clinker in planetary cooling tubes attached to the outlet end.
B. M. V.
T e m p e rin g of g la s s . Soc. An o n, d e s Ma n u f. d e s Glaces et Pr o d. Chem. d e St.-Go b a in, Ch a u n y
& Cir e y (B.P. 479,878, 14.8.36. F r., 5.9.35).—Cas
ings suitable for applying cooling medium a t differont intensity to different parts and shaped to be closer to the glass article a t some parts th an a t others aro described. The objects aro to vary the tem per a t different p arts and to tre a t articles of non-uniform
thickness. B. M. V .
M a n u fa c tu re of te m p e r e d g la s s . C. T. Pugh
and W. As h (B.P. 478,811, 15.11.37).—The sheet is heated to the plastic state and then quenched by air in two stages, the air pressure a t first being < 2 lb./
sq. in. until tho glass is hardoned (0-33 lb./sq. in./4
Cl. v n i . —GLASS; CERAMICS 515 sec. or 1-5 lb./sq. in ./l sec.) and afterwards increased
to any desired extent. B. M. V.
T e m p e re d g la s s a r tic le s . Co r n in g Glass Works, Assees. o f J . T. Little to n, W. W. Sh a v e r, and H. R. Lil l ie (B.P. 479,173, 30.6.36. U.S., 24.9.35).—For cooking utensils and tho like the glass has annealing tem p, (in 3 separate claims) < 540°, 585°, and 630°, and softening temp. < 260°, 240°, and 240°. I t contains < 10 or 15% of A120 3, > 2 % of alkali, and -t 10% of alkaline-earth oxides. Tho coeff. of expansion is <6-5 (or <4-5) X 10'e. The glass is tempered in a bath of molten inorg. salts to ju st short of oxplosive fracture, i.e., to a max. tension
o f 2—3 kg./sq. mm. B. M. V.
S ta b ilis in g a n n e a le d g la s s a r tic le s , p a r t i c u la rly th e r m o m e te r s . Co r n in g Glass Works
(B.P. 479,631, 24.12.36. U.S., 30.12.35).— The glass is held for a relatively short time a t a temp, sub
stantially > the max. temp, of use b u t < the strain temp. In the case of a therm ometer made of two glasses, the softer stem is supported against deform
ation and a temp, hear tho strain point of the hard bulb is maintained for a short time, th en a falling temp, for longer periods; it is then heated for a short time near the strain point of the softer glass, and for still longer periods a t lower temp. B. M. V.
M a n u fa c tu re of e n a m e lle d p ro d u c t. 0 . E.
Ha r d er and J . D. Su l l iv a n, Assrs. to Battelle Memorial In s t. (U.S.P. 2,070,272, 9.2.37. Appl., 8.8.34).—A pptn.-hardenable alloy is coated with enamel a t a temp. > tho m.p. o f the enamel and high enough to keep the constituents of tho alloy in com
plete solid solution. Tho coated article is cooled rapidly to room temp, and then reheated to produce hardening of the alloy. When max. hardness is not necessary the m aturing temp, of tho enamel may be matched to tho pptn.-hardening temp, of the alloy and one heating will suffice. B . M. V.
M e th o d fo r e n a m e llin g ta n k s . W. G. Ma r t in, Assr. to A. 0 . Smith Co rp. (U .S .P . 2,070,368, 9.2.37.
Appl., 8.6.35).—Vitreous enamel is applied to the interior of a tan k after it has been heated to produce a coating of oxido; prior to raising the temp, to the m.p. of the enamel tho air is forced out by introduction of solid C 0 2 and tho internal pressuro is maintained a t
> 1 atm . during tho fusing and setting. B. M. V.
P u rific a tio n of n a t u r a l d e p o sits [sa n d s o r c lay s], R . W. Fl i n n (U.S.P. 2,070,161, 9.2.37.
Appl., 21.1.35).—Tho m aterial, e.g., S i02 sand for glass-making purposes, is passed continuously through, and agitated in, an oven in presence of a continuous stream o f Cl2 gas. A hoat gradient is m aintained and the exhaust gases from different zones of temp, are
removed separately. B. M. V.
D e -a irin g a n d d e g a s s in g c e ra m ic b o d ies.
Gew erkschaft Keram chem ie-Berggarten (B.P.
479,157, 2.12.36. Ger., 7.12.35).—After shaping, the plastic mass is subjected to vac. and afterwards to rapidly increased pressuro (< 1 atm.). B . M. V.
C e ra m ic b o d ie s, in p a r ti c u la r fo r u s e a s in s u la to r s fo r s p a r k -p lu g s . Ge n. Motors Co r p. (B.P. 479,124, 27.6.36. U.S., 27.6.35 and 22.5.•36).—
The m aterial is free from quartz and contains > a trace of alkali; it comprises a mixturo of finely- ground materials, containing A120 3 85—99 and S i02 15—1% (corundum 46—96, mullite 53—3%), sin
tered to a dense (apparent d ~ 3-75) non-porous mass a t Soger cone 30—35. No bond or void filler is in corporated, b u t the m aterial may be highly com
pressed before fritting. B. M. V.
C onnexion b e tw e e n c e ra m ic b o d ies a n d m e ta ls . R. Scharfnagel (B.P. 479,084, 27.7.36. Ger., 25.7.35, 2.4. and 8.7.36).—The two bodies aro ar- rangod in their final relative position and a connecting m etal is molted in tho joint, the whole being pre
heated to near tho m.p. o f the connecting metal and tho latter alono, or it and tho metallic body, being further heated by high-frequency induction. E x amples of connecting alloys claimed aro : Ag 65, Cu 25, Fe 10% ; Ag 75—80, Cu 25—20% ; Ag 15, Cu 80, Be 5 % ; Ag with 2—25% Cd and optionally Cu and/or Fe. The alloy is preferably formed by melting
in vac. B. M. V.
M a n u fa c tu re of a b ra s iv e a r tic le s . Norton Gr in d in g Wh ee l Co., Lt d. From Norton Co.
(B.P. 479,703 and 479,789—90, 15.12.36).—D ia
mond, BC, or other grains of hardness > 1 3 Moh aro bonded with : (a) powdered m etal (Al 40, Si 60%) of m.p. > 1400°, the whole being subjected to heat and pressure; (b) an alloy selected to have d 4-0—3-0, which may be used molten, e.g., Cu 38, Al 62%, Mg, Si, and Zn also being claimed as suitable con
stituents; (c) a brittle alloy comprising Cu with Sn,
N i, Al, Mn, and/or Be. B. M. V.
M a n u fa c tu re of [flexible] a b ra s iv e a rtic le s . Carborundum Co. (B.P. 479,767, 10.8.36. U.S., 5.9.35).—A single layer of grains is p artly embedded in a solf-supporting or roinforced sheet of bonding m aterial of thickness < the m ajor diam eter of tho grains. Tho bond is preferably applied as a solution to a tem porary support, grains are added, and com
bination is sot by heat and removed from tho support.
B. M. V.
P r e p a r a tio n of g r in d in g o r p o lis h in g to o ls . E . Ethel and 0 . Susse n g u t h, Assrs. to Ba k e lit e Corp. (U.S.P. 2,070,158, 9.2.37. Appl., 4.6.31. Gor., 17.6.30).—Abrasive grains aro formed into a mould- able composition with a solution of resin in tho In
state, tho resin being of tho uroa-aldehydo or poly- basic acid-polyhydric alcohol type, a phonol-aldehyde resin being also present if desired. B . M. V.
M e th o d of b a la n c in g a g rin d in g w h e e l. C. J . Hu d s o n, Assr. to Norton Co. (U.S.P. 2,070,360, 9.2.37. Appl., 9.12.36).—An aq. suspension of finely- pulverised mineral with a wetting agent is introduced into the pores on the light side of the wheel.
B. M. V.
C h e q u e r-b ric k a s s e m b lie s fo r fu rn a c e r e g e n e ra to rs . Op e n He a r t h Co m bustio n Co. (B .P . 479,125, 29.6.36. U.S., 2.3.36).
P ro d u c tio n of [g la ss e tc .] th r e a d s . Th er m o lux Glass Co., Lt d. (B.P. 482,021,25.3.37. It., 23.12.36).
F u rn a c e fo r e n a m e lle d F e .—See I.
5 1 6 BRITISH CHEMICAL AND PHYSIOLOGICAL ABSTRACTS.—B.
IX.—BUILDING MATERIALS.
C o a l-d u st s p r a y e r fo r r o ta r y [c em en t] k iln s . E. 0 . Ch o d o b o v (Bull. Union Res. Inst. Cement, U.S.S.R., 1937, No. 2, 10—40).—Laboratory tests and experimental work on the design of a suitable coal-dust sprayer are discussed. Various designs aro illustrated and a sprayer which is to be tested under large-scale conditions is described. D. G.
P ro d u c tio n of p u z z u o la n a P o r tla n d c e m e n t a t th e K o m so m o le tz fa c to ry . P . P. Gorski (Bull.
Union Res. Inst. Cement, U.S.S.R., 1937, No. 2, 41—52).—Particulars of the m anufacture of puzzuo
lana cement from clinker and trepel (a local puzzuo- lanic m aterial available in enormous quantity on the banks of the Volga) are given. M ethods of quarrying and grinding trepel are described and the properties
of the cement are given. D. G.
M a g n e sia in P o r tla n d c e m e n t. V II. E ffe c t of m a g n e s ia on p r e p a r a tio n of c a lc iu m silic a te s . Y. Sa n a d a (J. Soc. Chem. Ind. Jap an , 1 9 3 8 ,-4 1 , 10b ; cf. B., 1938, 377).—Synthetic cements con
taining CaO, S i0 2, and MgO were prepared. Accord
ing to the composition, the reactions in burning were : CaCO, + S i0 2 + 2MgO -> C a0,S i02,Mg0 + M gO;
2CaC0s + S i0 2 + MgO -> 2CaO,SiO,> + M gO;
3CaC03 + SiO, + 2MgO -> 2CaO,Si0a + CaO + 2MgO. I n cements, when the ratio CaO : SiO, is > 2 ,
the MgO is uncombined. T. W. P.
M a g n e s ia in P o r tla n d c e m e n t. V III. R a w m ix tu r e s of h ig h -m a g n e s ia c e m e n t. Y. Sa n a d a
(J. Soc. Chem. Ind. Japan, 1938, 41, 36b; cf. preced
ing abstract).—Mixtures of S i02, A1,03, Fe20 3, CaO, and MgO were calcined a t 800—1400° for 2 hr. The clinkers contained free MgO, b u t no free CaO, after
calcination a t 1400°. J. A. S.
A p p ro x im a te g la s s c o n te n t of c o m m e rc ia l P o r tla n d c e m e n t c lin k e r. W. Le e c h (J. Res. N at.
Bur. Stand., 1938, 20, 77—81).—The glass content of 21 samples of clinker, determ ined by the heat of dissolution method (Concrete, 1937, 45, 199), varied from 2 to 21%. Laboratory heat-treatm ent of the clinker shows th a t tho highest glass content is obtained from the rapidly cooled m aterial, which also has the highest content of sol. MgO. J . W. S.
E ffe c t of c e rta in m in e r a lis in g s u b s ta n c e s on s y n th e s is of c a lc iu m a lu m in a te s a n d a lu m in o - f e r r ite s . N. A. To e o po v and T. M. D iu k o (Bull.
Union Res. Inst. Cement, U.S.S.R., 1937, No. 2, 3—9).—The possibility of adding small quantities of substances which strongly prom ote the form ation of compounds required in clinkers is investigated. Tests showing the favourable effects of additions of mineral borate, obtained from the newly discovered deposits in the Inder region, on the form ation of Ca0,Al20 3, 4Ca0,Al20 3,Fe20 3, and 5Ca0,3Al20 3 are described.
Graphs and tables are given. D. G.
Q u ic k -s e ttin g a n d b e a t-e v o lv in g c e m e n ts . IV.
K . Ak iy a m a (J. Soc. Chem. Ind. Jap an, 1938, 41, 5—6b; cf. B., 1938, 378).—F our series of cements having CaO contents of 40, 50, 60, and 70%, respect
ively, were prepared. In each series cements were m ade having S i0 2 : A120 3 ratios varying from 0 to
1-0. Cements of the first series gave progressively shorter setting times as S i0 2 : A120 3 was reduced, and also higher strength vals. in the region S i0 2 : A120 3
= 0-33—0. D ata on th e other series are given.
T. W. P.
S e ttin g of h y d ra u lic c e m e n ts . V. Ro dt
(Tonind.-Ztg., 1938, 62, 188—190).—A CaO m ortar does not set if loss of H 20 is prevented. W hen moist Ca(OH)2 is dried i t retains a considerable am ount of H aO even in an atm . of low hum idity, whilst a t high hum idity the excess is > 1 mol. Truly hydraulic cements, which set even in presence of excess of H 20 , do not show this behaviour. G. H . C.
A u to m a tic c a lo r im e te r fo r d e te r m in in g th e b e a t of h a r d e n in g of c e m e n ts . D. C. Av d a l ia n
(Bull. Union Res. In st. Cement, U.S.S.R., 1937, No. 2, 89—92).—The apparatus is described and illustrated.
D. G.
C em en ts fo r o il w e lls. A. Ra in u (Ciment si Beton, 1937, 5, 1; Zement, 1938, 27, 49).;—High- A120 3 cements are desirable owing to their greater tolerance of excess of gauging H 20 . A special product for the purpose has an A120 3 modulus of 2-82 and a
S i02 modulus of 2-53. G. H. C.
C elite. V I, V II. P r e p a r a tio n , a n d te s tin g , of c e m e n ts w ith ir o n m o d u lu s 0-5—0-3. Y. Sa n a d a
(J. Soc. Chem. Ind. Japan , 1938, 41, 8—9b; cf. B., 1938, 377).—VI. Synthetic cements were prepared in which the ratio A120 3 : F e20 3 was decreased from 0-5 to 0-3. The form ation of clinker became easier w ith the decrease and the celite content increased.
V II. The properties of th e resulting cements showed th a t th e resistance to chemical attack by S 0 4" was better th a n th a t of ordinary Portlands. W ith decrease in the A120 3 : F e20 3 ratio the setting time was accelerated and the strength reduced; T. W. P.
U se of c e m e n ts , m o r t a r s , a n d c o n c re te s fo r m a r in e w o rk s . I I , I I I . P. Du m e sn il (Rev.
Mat. Constr., 1937, 221—229, 241—247; cf. B., 1937, 442).—II . Various factors affecting the suitability of concretes for marine structures, including th e use of fresh or sea-H20 for mixing, fineness of the cement and compactness of th e concrete, th e effects of the addition of trass on tensile and compressional strengths, axid th e problem of producing better resistance by the incorporation of H 20-repellent substances, are discussed. Theories on th e internal physical nature of freshly prepared concrete and accelerated hardening b y application of pressure aro considered.
I I I . The construction of new harbour works a t La Rochelle-Pallice (France) is described.
R. J . W. R.
R e c e n t w o rk in th e U .S .S .R . on c o rro s io n a n d p ro te c tio n of c e m e n t a n d c o n c re te . M. v o n Pohl
(Korros. u. Metallschutz, 1937, 13, 417—424).—A colloquium of th e Russian Academy of Sciences.
Action of aggressive, waters on concrete and the evalu
ation of aggressiveness. I. E . Orlov. C 02 is tho m ost active a g e n t; rate of attack cc [C02]2. During the construction of th e Moscow underground railway it was observed th a t aggressiveness was cc salinity.
Corrosion research. V. M. Mo sk v in. The reaction of CaSO.j with Ca alum inates ceases in presence of Ca
Cl. IX.—BUILDING MATERIALS. 517
or Mg salts (> 6 0 0 'm g ./litr e ) ev en w ith high [ S 0 4].
Corrosion of concrete by aggressive water or impure gauging-water. B . A . K u v ik in and P . N . L e v to n o v . The am ounts o f CaO lo st b y p uzzuolana cem ent and b y Portland cem ent + 10% o f trip oli on exposure to solutions o f M g S 0 4, M g S 0 4 + C 0 2, an d MgCl2 + N a 2S 0 4 were appreciably < th a t lo st b y pure P ortland cem ent a t an age o f 18 d ays, an d considerably less a t 90 days. P resen ce o f C 0 2 slow s th e in itial rate o f loss o f CaO, but accelerates it later. Concrete m ade w ith d istilled H 20 w as less resistan t th a n th a t m ade w ith an artificially im pure H 20 containing S", S 0 4", N H / , N 0 3', an d Cl'. Corrosion of concrete in water.
V . A. K in d . CaO can b e d issolved from concrete b y H 20 w hich is free from aggressive salts. Presence o f puzzuolana hinders th is. Activity of puzzuolanas.
P . P. B u d n ik o v . A ctiv ities were m easured colori- m etrically and from electrical, con d uctivities. T he m o st efficient contained a high proportion o f colloidal m atter. Additions to cement for dam construction.
V . P. N e k r a s s o v . Cem ent is n ot deem ed ready for u se i f a n y special m aterials h ave to b e added w hen it is gauged. Use of a protective shell of reinforced pre
cast slabs for dams. V. P . N e k r a s s o v . R einforced w atertigh t slabs w ith a slag aggregate are used.
Sait-resistance of cement. L . S. K o g a n . A n ew te s t
in g procedure in dicates th a t puzzuolana cem ents are m ore resistan t th a n is Portland cem en t. Oas- permeability of concrete in relation to coirosion. S. I.
I d a s c h k in . E a sily perm eable concrete is moro read ily attack ed , e.g., b y S 0 3 in th e air. H ardeners, e.g., CaCl2, or a surface coatin g o f acidproof cem ent p revents th is. Corrosion of reinforced concrete. I. A.
A le x a n d r o v . T he steel should be free from rust and scale, and th e p n o f th e concrete should be k ep t high.
T he aggregate should be dense and excess o f cem ent m u st be avoided. A ll aggregate should b e washed w ith clean H 20 . Concrete m u st bo placed m echanic
ally, n o t poured, and th e H 20 con ten t m ust be w atched during settin g. Effect of biological factors on the resistance of concrete to sea-water. A . A . S a d o v sk i.
P la n t grow ths cause form ation o f p rotective carbonate films, w h ilst anim al grow ths destroy th em . B io logical processes m ay cause ex te n siv e and d estru ctive p B changes. Resistance of concrete to surface cracking.
J . A . N i e l a n d e r . Cracking m a y be due to bad p lacing, incorrect tem p , or m oisture conditions, or incorrect proportioning. I t is rare in p lastic concrete.
Use of puzzuolana cements on the Svir hydroelectric plant. N . P . C h o z a lo v . V ery dense concrete was used. Concreting in winter. I. A. K ir j e n k o . The H ,0 -c e m e n t ratio m u st be w atched. Draft limits fo r impurity of water. B . G. Sk ram taev. Tables g iv en in d icate th a t H aO m a y be considered dangerous in con tact w ith concrete w hen th e C 0 2 content exceed s specified lim its for g iv en hardness and S 0 4" + Cl' con ten t. F or m ixin g or dam ping con
crete it is su ggested th a t th e p a should b e > 4 and th e [ S 0 4] < 1 5 0 0 m g ./litre, excep tin g for u se indoors, in h o t clim ates, or w ith h igh-A l„03 cem en ts. Attack of concrete by C 02. M. I. Su b b o t k in. T h e a tta c k is due to H ions, and th e term “ aggressive C 0 2 ” is applied to th a t present as H 2C 0 3, as d istin ct from free C 0 2 or C 0 3". P rotection m a y b e ob tain ed b y : in terp osition o f a carbonate layer to regulate th e
p a of the H ,0 reaching the concrete; use of special cements, e.g., slag cement etc., or by concrete of high density, e.g., vibrated, or containing hardeners or waterproofers. Building materials and their applic
ability to concrete under water. P. Filosofov. The strength of various cements was tested after varying periods of immersion in 16% MgCl2 and N a2S 0 4 solu
tions. Most Portland cement m ortars and concretes lost strength under these conditions, but when 10% of
tions. Most Portland cement m ortars and concretes lost strength under these conditions, but when 10% of