Forms of Alkalies and Their Effect on Clinker Formation

CEMENT and CONCRETERESEARCH. Vol. 7, pp. 719-730, 1977. Pergamon Press, Inc Printed in the United States.

ALKALIES IN CEMENT: A REVI~V I.

Forms of Alkalies and Their Effect on Clinker Formation Inam Jawed and Jan Skalny N~rtin ~rietta Laboratories Baltimore, Maryland

(Communicated by S. Diamond) (Received September 15, 1977) ABSTRACT Alkalies in portland cement clinker occur as sulfates and, depending on the amount of SO3 available, may also be present in calcitun silicate and aluminate phases. Introduction of alkalies into clinker minerals modifies their crystal structure which, in turn, can change their hydraulic reactivity. Alkalies affect the clinkering process by modifying the physicochemical properties of the melt formed in the kiln, and may have an adverse effect on the phase composition of clinker.

In Portlandzementklinkern vorkommende Alkalien k~nnen Sulfate sein oder auch in den Silikat-oder Aluminatanteilen vorkommen, je nach der vorhandenen Menge yon SO 3. Alkalien in Klinkermineralien modifizieren deren Struktur und kBnnen dadurch deren hydraulische Reaktionen ver~ndern. Alkalien beeinflussen den klinkerformenden Prozess dadurch, (lass sie die physikalisch-chemischen Eigenschaften der in der Kiln geformten Sc~melze beeinflussen. Die Anwesenheit yon Alkalien kann unerw~nschte Folgen for die Phasenkomposition yon Klinkern haben.

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I.

Introduction

Alkalies are unavoidably introduced in minor quantities into portland cement clinker. They aroused particular interest when Stanton (I) reported that alkaline solutions produced in the hardened concrete subsequently reacted with some aggregate ingredients causing disruptive expansion and deterioration of concrete structures. Since then alkalies have come to be regarded as potentially deleterious but unavoidable species in clinker. In fact, the alkali-aggregate reaction has been termed the "cancer of concrete", and the alkalies from the cement compared to viruses (2). Since Stanton's report, a vast literature has accumulated on the alkali-aggregate reactions. An annotated bibliography of alkali-aggregate reactions,covering literature up to 1974, was compiled by Figg (3). A recent review by Diamond (4,5) stmmarizes the knowledge of the mechanism of alkali-silica reactions. There has now been a renewed interest in alkalies in clinker because of changes in pyroprocessing technology, call for energy conservation, the limited availability of low-alkali raw materials, and tightened environmental restrictions. Increase in fuel prices has accentuated the trend from wet to dry processes and to the use of coal as the primary fuel source. All the above factors lead to increases in alkali and sulfate concentrations in the clinker. Any means to remove alkalies is a technically difficult and an expensive proposition. The worldwide trend, therefore, now seems to be towards higher alkali contents in cement. The maximum limit of alkalies expressed as Na20 equivalent (Na20 + 0.658 K20), specifiedwhen the cement is to be used in concrete with reactive aggregates, is 0.6% (ASTM C 150-74). The usual alkali content (Na20 + K$O) of portland cements, however, ranges from 0.3 to 1.3%, and in high alumzna cements from 0.I to 0.6%. II.

Origin of Alkalies in Clinker

Alkalies in clinker originate from the raw materials used for the manufacture of portland cement -- i.e. clay, limestone, chalk, and shale -all of which contain alkalies. Typical analyses are as follows (6): Clay K20 (%) Na)O (%) $2: (%) SO 3 (%)

2.61 0.74 -0.21

Limestone 0.26 0.ii 0.03 0.02

Shale

Chalk

4.56 0.82 0.30 --

0.04 0.09 0.01 0.07

Typical Raw Mix 0.52 0.13 -0.07

Alkalies can also come from coal ash if coal is used as the primary fuel. As will be described later, most of alkalies in clinker exist in some combination with sulfur. Sulfur in clinker may come from oil or coal used as fuel. Additionally, it may originate from raw materials such as clay or shale where it occurs as pyrites, sulfates, or organic compounds. About 50% of alkalies present in the raw feed are volatilized in the kiln between 800°C to 1000°C. These alkalies are later partly condensed in cooler parts of the kiln. Formation of rings and coatings on the kiln lining has been attributed to the condensation of alkalies and their reaction with the refractory material (7-10). The extent of volatilization varies with raw materials, and is higher for clays than for feldspars. Usually

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721 ALKALIES, CEMENTCLINKER, HYDRAULICITY

potassium compounds are more volatile than those of sodium but this is not universally the case (ii). A direct linear relationship between the density of the alkali-containing raw materials and the extent of volatilization has been reported (12). The extent of volatilization is also affected by the type of kiln. There is a general tendency for the retention of alkalies to be higher as the energy efficiency of the kiln system increases (6). A larger amount of alkalies is volatilized when gas or oil is used as fuel as compared to coal (13). Sulfur containing compounds from the raw materials and fuel are oxidized in the kiln to SO 3 and a sulfur cycle forms. The first reaction of SO5 is to form alkali sulfates, preferentially with potassium, and later calcium sulfates. At higher temperatures, alkali sulfates are vaporized and calcium sulfate is partly decomposed. More than half of the sulfur originating from raw materials and fuel appears in the clinker; the rest is lost in the flue gases and in the kiln dust. Besides reacting with alkalies, SO3 can also combine with silicates and aluminates to form compounds such as (2 CaO.SiO2)2.Caso4 or 4 CaO.3 Al203-SO3. These may build up in kiln rings but decompose again at clinkering temperature. III. Alkali Compounds in Clinker Compounds containing alkalies and sulfur may be found in almost all parts of the cement plant. These compounds occur in the clinker, on the kiln linings and preheaters, in the kiln dust, in the flue gases, and in the storage silos. Whereas the presence of fluorides and chlorides in the raw feed enhances the volatility of alkalies (14-19), the presence of sulfur leads to reduction of alkali volatility during clinker formation (20-22). Alkali compounds in clinker can be divided into three main groups (25-26): (a) Alkali sulfates; (b) Alkali aluminates and aluminoferrites; (c) Alkali silicates. In some cases, alkali may also occur in the form of carbonates

(2S). Alkalies as Sulfates Based on available evidence, it appears that the clinker SO5 makes prior demand on the alkalies. The resulting quantity of alkali sulfate is determined by the ratio of total clinker sulfate to total alkali. The remaining sulfate forms calcium sulfates, either as the soluble double sulfate or as anhydrite. The alkali sulfates most commonly formed are: Potassium sulfate (arcanite, Sodium potassium sulfate solid solution)

K2SO4)

(aphthitalite, Na2SO4.3~SO4, or a similar

Calcium potassium sulfate (calcium langbeinite, 2Caso4-K2SO4, or a similar solid solution) According to Pollitt and Brown (25),potassium sulfate is likely to occur either alone or in one of the two double sulfate forms depending upon the available quantities of sodium sulfate and calcium sulfate, the preference probably being for the double alkali sulfate. Sodium sulfate may occur alone but, more probably, as the double alkali sulfate. It does not form a double salt with calcium sulfate. Calcium sulfate occurs either alone or as 2 CaSO4-K2SO4 subject to the prior formation of double alkali sulfates.

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Overall, potassium is twice as likely to produce soluble sulfate as sodium. The burning zone atmosphere has been reported to influence alkali compound formation (27,28). Calcit~npotassium sulfate, 2 CaSO4.K2SO4, tends to be produced in an oxidizing flame while sodium potassium sulfate, 3 K2SO 4Na2S04 , is produced under reducing burning conditions. Alkalies in Aluminates and Silicates After allocating alkalies to sulfate, the remainder appears to be distributed between the silicates, aluminates and aluminoferrites. The rules governing the quantitative division of alkalies between silicates, aluminates and ferrites are not yet clear but, it is known, that aluminates and ferrites accomodate about half or more of the available alkalies. The quantity of alkalies in the aluminate and ferrite phases, respectively, is found to be related to the alumina contents of these phases (25). Lea (6) has given the following typical ranges of solid solutions in the four main clinker components:

Na20 (%)

K20 (%)

C3S C2S C3A

0.I - 0.3 0.2 ~ 1.0 0.3 ~ 1.7

0.i - 0.3 0.3 - 1.0 0.4 - I.I

C4AF

0.0 - 0,5

0.0 - 0 . I

The characteristic sodi~n containing compound is NC8A3 and has been the subject of extensive investigations (24,25,29-41). The exact stoichiometry of NCsA 3 and its potassium containing analog is, however, very difficult to confirm. Free alkali reacts with C3A to form NCsA 3 and free lime; this CaO could theoretically react with C2S to form C3S but the reaction is sluggish and often incomplete. Alkali contents may, therefore, influence the degree of lime saturation and cause latent unsoundness. According to Suzukawa (33), NC8A 3 is a dark prismatic interstitial phase with slight silica content, having refractive indices of 1.702 and 1.711, birefringence of 0.010, and negative elongation. The x-ray pattern is similar to that of C3A but with the following difference: the strong C3A lines are split - the 23045 ' 28 lSne with d = 1.91 N i~to 1.89 and 1.92 ~i and the 29°36 ' 2@-line with d = 1.56 ~ into 1.55 and 1.56 ~ C39]. If clinker contains anhydrite (CaS04), it can react with NC8A 3 to give thenardite (Na2SO 4) and C3A. A value of 2576 kcal/mole for the heat of formation of NC8A 3 and 4850 kcal/mole for its heat of reaction with CaSO 4 to form Na2S04 and C3Ahas been reported (42). The existence of compound KC23S12, as discussed by Taylor (43-4~), is difficult to identify by optical microscopy. Nurse (46,47) and Suzukawa (48,49) have concluded that this product is not a distinct compound but a potassium stabilized form of e'-C2S. Petrographic examination shows that KC23S12 consists mainly of irregular or rounded particles with relatively low blrefringence (59). Its refractive indices are 1.702 and 1.695, and the x-ray pattern differs from the 8-C2S pattern only in the intensity of some lines (46). It reacts easily wit~ anhydrite (CaSO4) to give arcanite (K2SO4) and C2S. If NC8A 3 is present simultaneously, formation of solid solutions of the type (Na,K)zSO 4 is observed. The composition of these mixed sulfates as a function of clLnker composition has been discussed by Newkirk (23,24), who also developed equations to indicate the effect of alkalies on

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723 ALKALIES, CEMENTCLINKER, HYDRAULICITY

the potential phase composition of clinkers. Very small changes in sodi~n, potassium, and SO 3 contents may cause relatively large changes in the amount of C3S and C3A. The heat of formation of KC23S12 from elements has been calculated as 6420 kcal/mole (50), this; however, cannot be used to decide whether a real compound or a crystalline solution exists. The heat of reaction of KC23S]2 with anhydrite to form 8-C2S and orthorhombic K2SO 4 has been given as 36.3 kcal/mole. Heats of solution of 8-C2S preparations containing increasing amounts of K20 show a maximum near the composition of KC23S12. Besides NC8A3 and KC $IS 2, the existence, of sodium, substituted, belite, NC23S12, and an orthorhom~Ic phase of potasslum substituted alumznate, KCsA3, has been suggested [26,49). Suzukawa (49) noted that KC8A3 formed only in the presence of SiO 2 which indicated that Si ions replaced A1 ions in this product. The formation of K20-4SiO 2 and Na20.2SiO 2 at 600°C, and Na2Ca(C03) 2 and K3Na(SO4) 2 at 700°C, is also reported (51,52). Other Alkali Compounds in Cement ~nufacturing The kiln dust contains alkali halides in addition to sulfates, the most common being sylvite (KCl) (26,53). The most common sulfates in kiln dust are arcanite [K2SO4) , aphthitalite [Na2SO4-3K2SO4) , and calcium langbeinite (2CaSO4.K2SO4). Formation of lumps in cement during storage has been attributed to another alkali calcium sulfate, syngenite (K2SO4.CaSO4.H2 O) [54-56). Increased syngenite formation was noticed when cement contained more than 12% by weight of C3A and had a total potassium content of about 1% (57-59). Syngenite is also formed during grinding of clinker in the mill if the temperature is lowered by water (60). Compounds of alkali and sulfur with or without silicates are major contributors to the formation of rings and coatings in the inner wall of kiln, suspension preheater, Lepol grate chambers, etc. These coatings result from the molten matter and contain alkali sulfates and chlorides,often together with spurrite (2C2S.CAC03) , sulfo-spurrite (2C2S.CASO4) , calcium sulfoaluminate (C3A.CaSO4) and calcium langbeinite [2CaSO~.K2SO4) (61-67). The formation of spurrite is known to be promoted by such fluxes as CaF 2 . Gutt and Smith (68) found that Na2SO 4 and K2SO 4 acted similarly to CaF 2. Simultaneous presence of alumina and K2SO4, however, discouraged spurrite formation. IV.

Effect of Alkalies on Clinker

The formation of clinker grains and their macro-and microstructure depend on the amount and the physico-chemical properties of the melt formed in the clinkering process. These properties of the melt are, in turn, dependent on the variation in the chemical composition of the raw mix, on introduction of ki.lndust and various additives into the raw mix, and on other factors influencing the composition of the liquid phase of the clinker. Changes in the melt composition affect the surface tension and viscosity of the melt (69). The surface tension leads to aggregation while the forces of gravity and viscosity offer resistance. Timashev et al. (70) noted that the size of the clinker grains increased with increasing surface tension of the melt. Single oxides or oxide mixtures ~ O , Na$O, MgO + Na20 , MgO + K20), which have little influence on the surface tenszon but do lower the viscosity of the melts, favored aggregation~dth formation of uniform grain size clinkers Introduction of SO jointly with K~O or Na20 into the melt modified the surface tension and led to phase separation. The less dense melt with lower surface tension is displaced onto particle surfaces. This slows down the aggregation and dust-like clinker grains are formed. The density of

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Na2SO 4 melt (3.0 g/co) is very close to that of clinker liquid phase (3702 g/cc) whereas that of K2SO 4 is lower (2.8 g/cc). Hence, Na2SO 4 droplets are dispersed into the parent melt whereas K2SO 4 droplets rise to the surface and phase separation occurs. The high surface activity of K20 in comparison with Na20 is also important; it facilitates separation of K2SO 4 as an independent liquid phase. The rate of formation of C3S has been found to be proportional to the amount of liquid phase in the kiln at a given temperature (71). Because alkalies decrease the temperature of melt formation, an effect on C35 formation is expected. However, the results of Johansen (72) showed that clinkers with or without alkalies had the same amount of free CaO after burning at 1400-1500°C. Vulkov et al. (73) showed that optim~n raw feed grain size led to an increase of liquid phase resulting in dissolution of greater amount of alkali oxides. This had an adverse effect on the crystallization conditions of C3S and decreased its content. Luginina et al. (74) also noted formation of highly fluid liquid phase at about 800°C due to presence of alkalies which affected the clinker formation. Results of Azelitskaya et al. (75) showed that a significant amount of free CaO appeared sooner than normal in alkali containing raw mixes. Increased amount of liquid phase formed but its alkali content prevented CaO from dissolving. The amount of C3 S decreased and formation of NC8A 3 type solid solution was observed. Kr~mer and zur Strassen (76) have shown that, whereas K2SO 4 does not influence the formation of clinker minerals, Na2SO 4 has a significant effect. In the presence of Na2SO 4, the XRD intensities of alite peaks decreased whereas peaks of CaO appeared. This is the same effect as shown by K20. They conclude that Na.2S04 is taken up by C2S in solid solution, which prevents the formatzon of alite in the same way as KC23S12 does. Woermann (77) observed the decomposition of alite by high concentrations of K20. He concluded that K+ may be contained in alite crystals at high temperatures but, at lower temperatures, the equilibrium alite ~ belite + CaO is shifted to the right causing decomposition of alite. Hive~ (78) also noted that K20 promoted decomposition of C3S to C2S plus CaO, and that it resulted in the formation of solid solution KC23S12. Yamaguchi and Uchikawa (79) showed the influence of Na~O on the formation of alite. Their high temperature .XPd9 studies revealed a strong tendency towards disintegration of alite and appearance of free CaO. C3S changes from triclinic to monoclinic symmetry as soon as 0.33% Na20 is taken up. The structure of this monoclinic phase is identical with that reported by Yamaguchi and Miyabe (80) with two Na + ions replacing one Ca 2+. Volatilization of Na20 brings about a retrograde conversion of the monoclinic symmetry of the crystals to triclinic. Ono et al. (81,82) found that with increasing alkali and decreasing MgO contents the free CaO first increased and then decreased considerably with increase in K20. ~-C2S increased with increasing Na20 + K20. The decrease of specific gravity of clinkers is attributed to the occurrence of ~-C2S , which has low specific gravity. ~-C2S is stabilized by Na20 or K20 whereas ~'-C2S is stabilized by K20 or K20 + MgO. However, on increasing K20 content, ~'-phase transforms into s-phase. Luginina et al. (83) have discussed the microstructure of clinkers containing alkalies and MgO. Presence of K2SO 4 imparted an equigranular texture to clinker with high porosity and contributed to development of coarse crystals of belite. Presence of MgO prevented the low temperature interaction of alkali with CaCO 3 (i.e., spurrite etc., are not formed). Clinkers containing alkalies

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725 ALKALIES, CEMENTCLINKER, HYDRAULICITY

in the presence of MgO form CaO.ZAI2Os.FeO 5 as a stable compound. In high alkali raw mixes, addition of MgCO 5 impeded the formation of spurrite. Suzukawa and Sasaki (84,85) noted that increase in Na20 content decreased the amount of FeO required to cause dusting of clinkers; they attributed this to the lowering of 8-~y inversion temperature of C2S (86) and to the change in the chemical composition of clinkers (45). Chin et al. (87) have found that a decreasing FeO/CaO ratio in the raw mix significantly decreases the alkali content in the clinker. Pollitt and Brown (25) have shown that introduction of alkalies into C3Amodifies its normal cubic fol~n to orthorhombic. This orthorhombic form of CSA is formed with a minimum alkali content of 2.8% equivalent Na20 or 1.8% equivalent K20. Works of Moore (88,89), Day (90), and Fletcher et al. (34) have also shown that small amounts of Na20 or K20 could replace CaO in the cubic C3A and that greater replacement of CaO gave rise to orthorhombic structures of NCsA 5. Boikova et al. (91) have also sho~n that presence of Na20 results in four polymorphic modifications of C~. The hydraulic activity of these modifications is a function of their Na20 content and is lower than that of pure C3A. Maki (37,92), on the other hand, claims that orthorhombic CsA exists in two forms, the low form containing 3.7% and the high form 5.9% Na20. These forms also take small amounts of SiO 2 into solid solution. From microscopic study of synthetic clinkers with varied contents of Na20 , Suzukawa (49) noted that NCsA 3 causes shirtings in the aluminoferr[te phase composition towards the higher ferrite contents, i.e., from C4AF to C6AF 2. Data of Butt et al. (95) show that the presence of alkalies in the raw material decreases the rate of the clinkering reactions. Similar effects of alkalies on clinker formation have also been reported by Benyei (94), Volkonskii and Shteiert [95), and Lokot et al. (96). V.

Effect of SO 5 on Clinker in Presence of Alkalies

At this point, a brief discussion of the effect of SO 3 on clinkers seems very relevant. Gutt and Smith (97) studied the role of SO 3 on clinker minerals and showed tha~, in the absence of alkalies and ~ O , the combined presence of A15+ and SO~-ions prevents the formation of C3S and favors solid solution of C2S with these ions. The presence of MgO counteracts this effect. In a later study, they noted a very complex effect of combined presence of alkalies and CaSO 4 (68). Whe D CaSO 4 w~s present in excess, neither Na20 nor K20 modified the effect of A1 ~+ and SO~-ions on C3S formation noted previously. Whereas in the absence of alumina both-sodium and potassium have mineralizing effects, in the presence of alumina their effects differ. At low concentrations of K2SO4, CxS is formed rather easily but, at higher concentrations of K2SO4, substantial liquid formation occurs at 1400°C and quenching results in pr.oduct containing only glass and 8-C2S with traces of K2SO 4. In contrast, in mLxes containing Na2SO 4 and alumina, the liquid formation Is not so great and C3S is formed easily. Examination of portland cement clinkers showed that K2SO 4 in no way modified the effect of A13+ and SO~-ions in forming C3S. However, Na2SO 4 proved to be deleterious and prevented the formation of C5S. This contrasted with the behavior of Na2SO 4 in C3S mixes where no adverse effects were found. Tsuboi et al. (98-100) found that the addition of SO X made burning and sintering very difficult as a result of increased viscosity of the melt. The alite crystals became larger and assumed "amoeba-like" shapes, whereas belite crystals did not have lamellae. The C3A content of clinkers decreased

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and the clinker pores became larger. Fukuda (i01) noted that an addition of 3.5% CaSO 4 to raw materials decreased sharply the C3A formation; at the same time formation of C3A.C~was observed. Above a certain CaSO 4 level (5.3%), the C3S formation decreased and a significant increase in free CaO was noticed. Formation of C3A.Cg , when gTpsum is present in the raw meal, has also been reported by Li (102). ~rtynstev et al. (103) found that the addition of 0.5% SO 3 imparted a coarse cD'stalline structure to clinkers with well defined alzte c©~stals. An increase to 1% SO 3 resulted in fine grained structure. SO~ also decreased the clinkering temperature by about 200°C. A decrease of clinkering temperature with increase in SO~. (added as gypsum to raw meal) has also been reported by ~hrakami et al. (I0~). Overburned clinkers with high sulfur showed large alite crystals. Clinkers burned at 1300°C, however, had badly formed alite crystals. Butt et al. (105) have found that increase of SO 3 (1.2 to 4.7%) in the raw feed decreased the K20 content in the clinker from " 7 2.4 to 2.03%. Clinkers containing 2.1% SO 3 't~,rere characten_ed by heterogeneous structures and indistinct crystallization of minerals. :in increase in SO 3 from 1.55 to 7.7% significantly changed the specific surface. Increase in SO 3 from 3.97 to 4.24% increased the amount of belite and decreased that of alite. A positive effect of g~/psum addition to alkali containing raw materials on the formation of clinker minerals has been reported by Azelitskaya et al. (106,107). The clinkering temperature decreased. The amount of C-S increased and a positive effect on the binding of CaO was noted. Presence of alkali sulfates resulted in well developed alite and belite crystals. Different alkali containing rm¢ materials required different amounts of gypsum. It is claimed that use of proper amolmt of gypsum resulted in higher kiln output and reduction of fuel consumption. VI.

References

(i)

T.E. Stanton, Proc. Am. Soc. Civ. Engr., 66, 1781 (1940).

(2)

G.M. Idorn, Proc. Symp. Effect of Alkalies on the Properties of Concrete, Sept. 1976 C & CA. London, p. 3 (1977).

(3)

J.W. Figg, Alkali-Aggregate (Alkali-Silica and Alkali Silicate% Reactivity, C ~ U R E A U , Paris (19/7).

(4)

S. Diamond, Cem. Concr. Res., 5, 329 (1975).

(5)

S. Diamond, ibid., 6, 549 (1976).

(6)

F.M. Lea, The Chemistry of Cement and Concrete, Chem. Publ. Co., 2nd Ed. N.Y. (1971).

(7)

E. Vogel, Silikattech., 9, 361, 449, 502 (1958).

(8)

H.E. Schwiete, Zement-Kalk-Gips, 9, 351 (1956).

(9)

R. Al~gre and P. Terrier, Rev. N~teriaux Constr. et. tray. publ. 523, 89 (1959).

(I0) H.M. Garrett, Pit & Quarry, (3), 84 (1976). (ii)

M. Rustom, Schweizer. Arch. Angew. Wiss. Tech., 22, 197 (1956).

(12)

I.P. Yanev et al., Trans. Mosk. Khim, Technol. Inst., 76, 125 (1973) C. A. no. 82:14424IV.

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727 ALKALIES, CEMENTCLINKER, HYDRAULICITY

(13) R.A. Loveland, quoted by W.J. ~ C o y and O.L. Eshenour, Proc. 5th Intl. Syrup. Chemistry of Cement, Tokyo, I/ol. II, p. 437 C1968). (14) H. Wood, Rock Prod., 45, 66 (1942). (15) E.R. Holden, Ind. Engg. Chem., 42, 337 (1950). (16) A.D. Azelitskaya, Silikattech) 5, 120 (1954). (17) A.D. Azelitskaya, Tsement (3), 13 (1954). (18) V.L. Pankratov and L.Y. Lopotnikova, Tsement, (S), 19 (1970). (19) V.M. Blonakaya and V.M. Stepanov, Tsement, (4), 12 (1969). (20) W.C. Taylor, J. Res. NBS, 29, 142 (1942). (21) T.F. Newkirk, ibid, 46, (1950). (22) J.P. Draper, quoted in The Chemistry of Portland Cement by R.H. Bogue, p. 129, Reinhold Publ. Corp. N.Y. (1955). (23) T.F. Newkirk, J. Res. NBS, 47, 349 (1951). {24) T.F. Newkirk, Proc. 4th Int'l Symp. Chemistry of Cement, London, p. 151 (1952). (25) H.W. Pollitt and A. Brown, Proc. 5th Int'l. Symp. Chemistry of Cement Tokyo, Vol. I, p. 322 (1968). (26) L.D. Adams, Paper presented at 75th Annual Ceramic Society Meeting at Cincinnati, April 1975. (27) J.E. Mander, Proc. Symp. Effect of Alkalies on Properties of Concrete Sept. 1976 C & CA. London, p. 27 (1977). (28) J.E. Mander and J. Skalny, Ceram. Bull., 56, (1977) (to be published). (29) L.T. Brownmiller and R.H. Bogue, Am, J. Sci., 23, 501 C1932). (30) (31) (32) (33)

K.T. Greene and R.H. Bogue, J. Res. NBS, 36, 187 (1946). D.L. Heath, J. Amer. Ceram. Soc. 40, 50 (1957). J.A. Conwick and D.E. Day, J. Am. Ceram. Soc. 47, 654 (1964). Y. Suzukawa, Zement-Kalk-Gips, 9, 345 (1956).

(34) K.F. Fletcher et al., Mag. Concr. Res., 17, 171 (1965). (35) A. Guinier and M. Regourd, Proc. 5th Int'l. Symp. Chemistry of Cement, Tokyo, Vol. I, p. 1 C1968). (36) S. Chromy and M. Gregor, Zement-Kalk-Gips, 21, 451 (1968). (37) I. Maki, Rev. 24th Gen. Mtg. Cem. Asscn. Japan, Tokyo, p. 5 (1970). (38) L.A. Dobronravova et al., Tr. ~bsk. Khim-Technol. Inst., 87, 44 (1975) C. A. no. 86:160080E. (39) I.A. Kryzhanovskaya et a l . , Cem. and Lime Mfg. 65), 45 (1966). (40) I. Maki, Cem. Concr. Res., 3, 295 (1973). (41) M. Regourd et al., J. Appl. Cryst., 6, 355 (1973). (42) E.S. Newman, J. Res. NBS, 61, 75 (1958). (43) W.C. Taylor, ibid, 21, 315 (1938). (44) W.C. Taylor, ibid, 27, 211 (1941).

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(45) W.C. Taylor, ibid, 29, 437 (1942). (46) R.W. Nurse, Proc. 3rd Int'l. S ~ . Chemist~" of Cement, London, p. 56, 169 (1952). (47) R.W. N~rse, Proc. 4th I n t ' l . Symp. Chemist~" of Cement, Washington Vol. I, p. 9 (1960).

(48) (49) (50) (51) (52) (53) (54) (55) (56) (57) (58) (59) (60)

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729 ALKALIES, CEMENTCLINKER, HYDRAULICITY

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E. Woermann, ibid, p. 119 (1960).

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•

(80) G. Yamaguchi and H. Miyabe, J. Amer. Ceram. Soc., 43, 219 (1960). (81) Y. Ono et al., Rev. 23rd Gen. Mtg. Cem. Asscn. Japan, p. 61 (1969). (82)

K. Takemoto and Y. Ono, ibid, p. 45 (1962).

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(93) Yu. M. Butt et al., Tsement, (5), 9 (1957). (94)

K. Benyei, Epitoanyag, 24, 71 (1972).

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T. Tsuboi et al., Zement-Kalk-Gips, 25, 292 (1972).

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