DE2029039C3 - Process for the production of expanding cement additives of calcium sulfoaluminate type - Google Patents

Description

The invention relates to a process for the production of expanding cement additives of the calcium sulfoaluminate type containing CaO and CaSO ₄ in a molar ratio of 0.5 to 1.8 and CaO and AlX) ₃ in a molar ratio of 3 to 9 in a direct current electric resistance heating furnace .

With the usual cements there is a large one Disadvantage in the formation of cracks due to shrinkage during the hydraulic consolidation stage and there have been various expanding cement additives for preventing such from occurring Cracks or for the introduction of positive prestressing for the secondary products made of cement, such as concrete structures and Hume concrete pipes. Examples of this are expanding cement additives using the hydraulic properties of calcium oxide, magnesium oxide, iron oxide, expanding additives that contain more than 7.0 percent by weight of a mixture of calcium sulfoaluminate and iron oxide and more than 21% anhydrous gypsum and by mixing Calcium oxide and gypsum with calcium sulfoaluminate, a part of which is made up of an alkaline earth metal and titanium oxide according to US-PS 33 03 037 was replaced, were made expanding cement additives, the by mixing gypsum with a complex salt of a silicate and a sulfate, and expanding cement additives, which mainly consist of alite, calcium sulfoaluminate and calcium sulfate.

However, the conventional method is the industrial one Manufacture of cement additives containing calcium sulfoaluminate as an expanding component by sintering the raw materials in a rotary furnace or in a radiation furnace (reverberation furnace) the rate of reaction or efficiency of converting the aluminum component to Calcium sulfoaluminate limited to a limited amount. This means that to increase the reaction rate or effectiveness of the reaction it is necessary to heat the raw materials until they come into the molten state and, as a result, the ring growth becomes in the sintering zone deep in the furnace, making it impossible to carry out the reaction continuously. Also in in this case the reaction temperature is higher, and therefore

3 4

half sulfuric anhydride is greatly enhanced using a sample of a fortified one submitted. Concrete, was obtained; it was confirmed that

The object of the invention is to create a mixture with a composition within the process for the production of expand-ien. Cement range EFGH showed the same qualities and additives of the calcium sulfoaluminate type, the 5 that mixtures with compositions within the difficulties described above can also be avoided advantageously within the scope of the ABCD area. method according to the invention can be used

The method according to the invention is thereby able.

This indicates that at least one was used in the furnace when determining the organic expansion. Fluoride melts, the melt all- io coefficient of a mortar sample according to the regulation gradually made a feed mixture consisting of JIS R 5201, wherein a cement with an inorganic fluoride and a CaO, CaSO ₄ content of an expanding cement additive and and ALO ₃ containing raw material added, whereby a standard sand for cement in a weight ratio of the amount of inorganic fluoride, based on the ratio of 1: 2 together with 65 weight percent the weight of the raw material in the range of 0.2-15 water, based on the cement, were mixed to 10 weight percent is then introduced under the conditions of the mortar thus produced in a steel mold frame of a voltage of 20 to 180 volts and 4x4x16 cm and for 24 hours electrode current density of 0.2 to 7 A / cm ² which was left to harden therein. The Expan temperature to 1200-1400 ⁰ C sets and closing sion coefficient at a free expansion amount borrowed the melt in an amount corresponding to the 20 denotes the amount of change of the length of the mortar amount of the supplied feed mixture off test, which was obtained by The specimen cured not and the feeding of the charge mixture was taken out of the mold frame, and the tapping was aged during stationary operation in water at 20 ¹ C and the length was repeated. The passage of time was measured. This method

In the context of the invention, 25 which can be used advantageously is generally used in mortar technology as “comparative inorganic fluorides are CaF 1, NaF, MgF ₂ . KF, verfahren «(comparator method) known. The Ex-AlF AL (SiF _f) ) ₃ NaAlF ₄ , Na ₃ AlF ₀ , AlF ₃ · 3'NaF, expansion coefficient for an expansion under Span-Na-Al ₃ F ₁ , ", CaF ₂ · 5 Al ₂ O ₃ and Ca ₅ F (PO ₄ ),. tion for a concrete (prestressed concrete) is to be determined

Furthermore, as raw materials to which: those in a concrete sample, as in the examples of the inorganic fluorides are mixed in, Ma- 30 Use of the expansion additive in the labeling which explains a large amount of aluminum oxide.

constituents, such as bauxite, alunite, aluminum- The molar ratios of the chemical compounds

oblique diaspore and continue the usual raw materials, to which the inorganic materials for expanding additives for cement, which are mixed with niche fluorides and which are used in Lime and gypsum containing gypsum can be used. 35 methods according to the invention are used

The addition of inorganic fluorides, such as 0.5 to 1.8 for CaO / CaSO ₄ and 3 to 9 for CaF ^ u the raw materials for the expanding CaO / ALO, and the preferred melting temperature additives, the flowability of the melt is affected. is 1200 to 1400 ⁰ C.

if the M oil ratio of CaO to CaSO _{4 is} higher

TTbeitscane for the products very easy. 40 is 1.8, the temperature of the melt becomes higher

The composition of the expanding cement- than 1500 ⁰ C, and sulfuric anhydride is violent additives according to the invention is within the released. Therefore, for the continued through area \ ABC and D in the triangular coordinate guidance of the tapping operation, the amount of the previous das'in'F i g. 1 of the drawing illustrates the standing inorganic fluorides over 10 percent by weight, in which the figures in percent by weight are increased by 45 percent, whereby the properties are depressed. In particular, the hatched area of the products will be deteriorated. If other-area EFGH is, for example, 0.2 to 5 percent by weight, the molar ratio of CaO / Cabu ₄ less than, in particular, 0.2 to 0.5 percent by weight, fluorite 0.5, the flowability of the melt can be reduced while in the surface GHDC be as improved more, but the temperature of the 5Gewicht's _P is rcent, in particular 5 50 melt to less than 1200 ⁰ C lowered to 10 by weight, whereby the nrozent F is uorit preferred because if the encryption formation of Calciumsulfoalum. nat is reduced SS is less than 5 percent by weight, the flowability and predominantly 12CaO- 7 Al ₂ O _{3 is} formed ability of the melt is reduced. In the case of the method according to the invention

The application of cryolite can have sufficient efTects, the flowability of the ^ ™ ¹ ™. ™ * ™ * ™ is improved with the application of an amount in the order of 55 three times that in the usual case of the amount required for fluorite, whereby the Working method will be very easy du.chhaten. On the other hand is within the feasible. Also, the reaction rate fm area ABFE, the amount of inorganic calcium sulfoaluminate added, is 1.3 times the amount, the fluorite yield is preferably about 0.2 to 1 percent by weight. in the usual procedure, rl.oht and the flexural strength g-5 ämt ichen ^g cases, the amount of this addition 6o, .it and PreßfestigkcH ones * ™ \ ^ ™ ^ _α ^ύ £ preferably as low as possible within the expanding / ur'c gen,;. «du Lrfindun. to ^ö - ■ · an ordinary Porlland-Zcnicnt nc li.niuii.ui

^ g ^^ ansionskocnizieiuei ^ er SS Ä Ä Ά ^ W dnc is the nominal size of an expanding additive mortar, which is expanded with the use of uDl.chen

for cement, a Vcrglcichsvcrsuch was durchgc- 65 liierenden additives hcrgeslcl I ™ ^e "leads in which the effective Expansionsgeschwindig- Hm considerable -ehlcr occurs at the start of Hc

wedge from the free expansion speed of a position of the expanding /.usatzc 111 cincm Glud Mörtek and from the expansion voltage, determined current resistance. heating furnace using the> or-

the mixed raw materials listed above and sulfuric anhydride hardly freely insofar as when the above mixed raw materials are given. The grain size of the raw materials raw materials directly into the electric furnace is preferably less than 0.5 mm for bauxite to be brought and heated, the plaster of paris and less than 2.5 mm for lime. Grosser RoIiteil is decomposed and sulfuric anhydride violently 5 materials are unfavorable, since the raw materials are released, so that expanding additives with the withdrawn melt not reacted or not obtained in the desired composition remain not melted and can continue to do so by themselves. if the residence time of the same in the furnace is extended. In the context of the invention, it is difficult to remove these unreacted or un-started processes for the production of the expanding io molten materials. When other additives by means of a direct current resistance heating furnace, on the other hand, the particle size of the raw materials is too fine, investigated and thereby the method of the present invention increases the reaction rate that maintains temperature. The temperature in the furnace is rapidly increased, which means that in the case of the production of the suppression of the release of sulfuric acid anhydride, expanding additives in a constant state becomes impossible, and the extraction of the electric resistance heating furnace with carbon electrodes, molten product difficult because of at least one of the above-mentioned reductions in its flowability. Therefore, inorganic fluoride as the starting point, the preferred grain size is one in which more material is placed at the bottom of the furnace so that when sieving with a mesh sieve, the inorganic fluoride fills at least the space, 20 by 44 microns . Conveniently, where the lower ends of the electrodes are located, the amount ratio of CaO / Al ₂ O _{3 is switched on} in the charging electric current. If a solid material in the range of 2 to 8.
permanent melt of the inorganic fluoride.
gradually to the melt while increasing the Vo- 25
lumens of the melt are added and when the volume of the melt is the possible height of the furnace. · , -1
reached, the melt tapped from the furnace. be 1 s ρ 1 e 1 1
When starting up, ie until the point in time at which

the mixed raw material in the above 30 bauxite, quicklime (calcium oxide) and water

Manner is added, the operation of the electroless plaster was mixed so that the molar

In an arc furnace, the ratio of CaO / Al ₂ O ₃ / CaSO _{4 is} 5/1/4

but then continued after the resistance mode of operation, and the mixture was pulverized to obtain the

led, and then the mixed feed mixture are obtained. CaF ₅ was in

Raw materials continuously fed into the furnace 35 in an amount of 1 percent by weight based on the

and the tapping operation in stationary operation weight, added to the feed materials,

repeated. According to the above procedure, a mixture of about 20 kg CaF ₂ and activated charcoal

can drive a completely melted Auf- was on the bottom of a Girod furnace of 450 kW

Flatulence agents are continuously produced. introduced around the carbon electrodes.

If the mixed raw materials directly to 40 and an electric arc was formed so that?

an electric arc of high temperature to a melt with a temperature of 1170 ° C

will be performed, as has already been obtained above. To the melt became gradually

acts, anhydrous gypsum with a decomposition point to the feed mixture prepared above

of about 1400 ⁰ C suddenly decomposed and set in strong and then by analysis with pulsed

Extent of sulfuric anhydride produced as a gas, the waves being detected by means of an oscilloscope, that;

through the expanding additives with the desired- the system of the electric furnace to that of one

th composition cannot be obtained. Resistance heating furnace had passed.

It may be possible to use a mainly CaO ■ As the amount of the feed mixture increases!

Al ₂ O ₃ or 12 CaO.7Al ₂ O ₃ existing melt, the volume of the melt gradually increased

prepare and then gradually the mixed raw 50 and the temperature of the melt reached 1370 ° C

materials to be brought in, but in this case there was neither decomposition nor severe «

the temperature of the melt higher than 1400 ° C, and release of sulfuric anhydride on. On

then the release of sulfuric anhydride was closing the melt in an amount voi

extremely strong. about 70% of the mass is tapped from the furnace, and under "direct current resistance heating furnace" a 55 continuously new charging mixture is used

Understood electric furnace, in which the melt was fed, the tapping operation was continuous

of the raw materials themselves directly as electrical repeated for 148 hours. The flow

DC resistance is used, and it can melt ability was good, and a release egg

Graphite electrodes or Söderberg electrodes as kicked by sulfuric anhydride during the ge Electrodes are used. 60 not all operations, and the expanding effect;

It should be pointed out that in the case of the other, expanding Zu

Turning of such an electric furnace the rates were better than that of materials that ii

A rotary kiln system has been made to reduce the atmosphere inside the furnace,

and a loss of sulfuric anhydride as a result. Table I shows the results of the chemical! could be feared, however, form listed according to the 65 analysis of the feed mixture. Tuesday

present invention CaO and CaSO ₄ a eutek voltage and the average power below

Table mixture in the range of 0.5 to 1.8 CaOCaSO ₄ , the operating conditions were 40 to 122 V µm

as already known, whereby the decomposition under- about 218 kW.

Table I.

SiOn

Al ₂ O,

IcX) ₃

CaO

Other

All in all

Charge Mix,% 0.9 Melted Product, ";, 1.7

12.50 0.7 51.5 33.4 1.0 100.0 12.00 0.7 52.1 32.0 1.5 100.0

The conditions listed in Table I above were calculated as follows: Raw material (total weight 100 g)

crowd

MolecuKirgew I

Mole number

Al ₂ O ₃

CaO

SO ₃

12.5
51.5
33.4

102 56 80

0.123
0.920
0.418

Al ₂ O,

CaO

CaSO ₄

MoI-A η number

*) Annotation:

SO, is given as CaSO ₄ in the description. The calculation shows that CaSO ₁ - ^ 0.41.8 mol and CaO - (0.920 - 0.418) ■ - 0.502 mol.

0.123

0.502 *)

0.418 *)

It can be seen that the following ratios therefore exist in Table I above:

CaOZCaSO ₄ = 0.502 / 0.418 = 1.20 CaO / Al ₂ O ₃ = 0.502 / 0.123 = 4.08

product

Amount of moles

Mole number

Al ₂ O ₃ 12.0 0.118 A ₂ IO ₃ 0.118 CaO 52.1 0.930 CaO 0.530 SO ₃ 32.0 . 0.400 CaSO ₄ 0.400 From this it follows in turn CaO / CaSO ₄ = 1.33 CaO / ALO, = 4.49

These calculations show that all mole ratios fall within the scope of the invention.

Since F i g. 1 illustrates the composition of the feed material in percent by weight, the molar ratios determined above of Al ₂ O ₃ = 0.123; CaO = 0.502 and CaSO ₄ = 0.418 converted into percent by weight as follows:

Al ₂ O ₃ 0.123 x 102 = 12.5 g
CaO 0.502 x 56 = 28.1 g
CaSO ₄ 0.418 x 136 = 56.8 g

(Percent by weight) 12.5 / 97.4 = 12.8 28.1 / 97.4 = 28.9 56.8 / 97.4 = 58.3

together 97.4 g together 100%

The composition point obtained above lies approximately in the central part of the area EFGH in FIG. 1.

Example 2

A mixture of 3 parts by weight of BaF ₂ , 4 parts by weight of CaF ₂ and 3 parts by weight of Na _{3 AlF 6} was placed together with coke particles at the bottom of an electric furnace in the same manner as in Example 1 and around the electrodes.

The formation of an electric arc caused a melt of around 10 ° C. to be formed.

Powdered, mixed feed mixtures that by mixing bauxite, calcium oxide, gypsum and cryolite in mixing ratios of 1.3 for

Ca * O / CaSO ₄ and 5.7 for CaOAl ₂ O ₃ in terms of molar ratio and 1% by weight of cryolite based on the weight of the raw materials were gradually added to the melt, and then the melt was tapped from the furnace . With the raw material continuously supplied to the furnace, the melt tapping out of the furnace was repeated, whereby the expanding additives were continuously formed. The temperature of the melt reached 132o ⁰ C. There was only a small release of sulfuric anhydride, and there was obtained an expanding cement additive with excellent properties. The composition of the feed mixtures and the composition of the expanding additives formed are given in Table 11 below.

Table II Gluhvcrlust

CaO

SiO ₃

Fe ₂ O ₃

Other

All in all

lime 0.5 95.7 0.2 0.4 1.9 0.8 99.5 bauxite 0.3 86.2 0.3 - 3.9 5.5 3.4 99.6 plaster 1.7 0.3 39.4 57.8 0.3 0.1 0.3 99.9 ExDandicrender 0.2 9.5 51.8 36.0 1.5 0.8 0.9 100.7

Comparative example 1

The comparative experiment was carried out using the the same electric furnace and the same Betchickungsmatcrialien as in Example 1 carried out. Without the initial melt being formed as in the previous examples, the charging materials became placed directly in the furnace and around the graphite electrodes, and an electrical one Bocen was trained, whereby the

Melt was formed from the charge maierialien. In this case the temperature rose Melt to about 1600 ° C and a remarkable one occurred Release of sulfuric anhydride. The batch mixtures that were added later were subsequently used not mixed in smoothly or uniformly, the eutectic mixture did not become readily and as a result, continuous operation was not possible. The composition ίο the melt is listed in the following table III.

Table III

SiO ₂

Al ₂ O ₃

Fc ₂ O ₃ CaO

SO ₃

Other

lnsaesLimt

Melt,%

1.4

18.4

1.1 77.2

0.6

1.3

100

As can be seen from Table III, the was used as the feed material The plaster of paris used is largely decomposed.

Examples of uses of the expanding additives

In these examples, the excellent effectiveness of the process according to the invention shown expanding additives obtained.

A clinker of the expanding additive produced according to Example 1 and a clinker of an expanding additive produced by the customary process were pulverized to a specific surface area of 2800 cm ² / g, determined by the Blainc method, and 12 parts by weight of the pulverized clinker were also pulverized 88 parts by weight of ordinary Portland cement mixed to obtain the expanding cement. Using the expanding cements thus obtained, test pieces of reinforced concrete were prepared. The test pieces were obtained in the following way: The expanding cement was mixed with sand with maximum aggregates of 20 mm and a fineness modulus of 3.8 and gravel with a fineness modulus of 6.9 and a water / cement ratio of 40% was used. A steel rod for prestressed concrete was placed in the center of a mold with a total length of 250 cm and a height of 15 cm, and the mixture was poured into the mold. After 6 hours, the mold was removed and a test pin was inserted into the concrete to determine the extent of expansion. After standing in a room for 18 hours, the stress or tension caused by the test pin was measured by means of a tension meter (Hargen-Bagar type), and the value thus obtained was used as the standard value α . Subsequently, the concrete sample was cured under a relative humidity of more than 90 ° _o (in water) and the stress of the concrete was measured with the lapse of time (aging) as the value b. The amount of expansion is then determined according to the following equation:

In Fig. Fig. 2 shows curve α the amount of expansion in the case where an expanding cement additive obtained by the method according to the invention was mixed with cement, and curve /) shows an amount of expansion in the case.

in which an expanding cement additive, de: was obtained by a conventional method (calcination in a rotary kiln), with cement mixture! would. Course c shows the extent of expansion for the case in which no expanding additive was used. From Fig. 2 it can be seen that curve a. which illustrates the results of the sample with the expanding cement additive according to the invention indicates a greater degree of expansion than curves / and c. The results of the strength test after 100 days (with three-sided storage) are shown in Table IV.

Table IV

Expanding Effective Strength Test Be-Additional Expansion initial load

by virtue of load

metric tons

Expansion of the concrete (%) = -

away

The results obtained are shown in FIG. 2 shown.

metric tons

metric tons

a) He 1.35 0.42 2.75 finding according to b) Common 0.50 0.37 2.32 c) Without 0.0 0.23 1.5

As can be seen from the table above

if the expanding additives according to de

Invention for a chemical toughening or express

Prestressing methods are used. Whose

Properties obtained from the usual products The above effective expansion force was obtained

according to the method of Muguroma and Mit

workers in Fifth International Cement Chemica

Symposium. Part IV, Session 4 using voi

243,000 kg'cm ² concrete elasticity and 1,980,000 kg'cm

Elasticity of the pc steel bar (pe = prestress <

Concrete).

The advantages of the present method can be summarized as follows:

(1) When forming the melt of the fluoride ink the electrodes in the manufacture of the expan

The additives according to the invention in the electric furnace are those added below Charge mixtures melted smoothly.

(2) Since the charge materials can be melted in a reducing atmosphere at a higher temperature than when using a rotary kiln, with the decomposition of gypsum with the release of SO _; , is reduced, uniform expanding additives 10 (5) can be obtained, with the reaction efficiency for calcium sulfoaluminate being increased by about 30 ",".

(3) Production can be carried out continuously for a long period of time, what previously when using a rotary kiln

was not possible because of the tendency to cake.

(4) The flexural strength and compressive strength of the additives which expand by mixing in of the invention in a cement mortar are about 30 ", increased compared to mortar samples, those using additives that have been manufactured according to conventional processes were received.

The expansion properties were remarkably increased as compared with sintered products. This allows an effective amount of expansion using a smaller amount of the expanding additives than in the case the use of common products.

For this purpose 2 sheets of drawings

Claims (8)

Patent claims: 1. A process for the production of expanding cement additives of the calcium sulfoaluminate type, which contain CaO and CaSO ₄ in a molar ratio of 0.5 to 1.8 and CaO and Al ₂ O ₃ in a molar ratio of 3 to 9, in an electric direct current resistance heating furnace, thereby ge -io indicates that at least one inorganic fluoride is melted in the furnace, a charge mixture consisting of an inorganic fluoride and a _{raw material containing CaO, CaSO 4} and AUO _{3 is} gradually added to the melt, the amount of inorganic. Fluoride, based on the weight of the raw material, is in the range of 0.2 to 10 percent by weight, thereupon the temperature of 1200 to 1400 ^{under the conditions of a voltage of 20 to 180 volts and an electrode current density of 0.2 to 7 A / cm 2} ° C and finally tapping the melt in an amount corresponding to the amount of the charging mixture fed and the feeding of the charging mixture and tapping repeated during stationary operation. 2. The method according to claim 1, characterized in that at least one of the compounds CaF ₂ , MgF ₂ , AlF ₃ , CaF ₂ ■ 5 Al ₂ O ₃ , Ca ₅ F (PO ₄ ) ₃ as the inorganic fluoride. Na ₃ AlF ₆ or BaF ₂ is used. 3. The method according to claim 1 or 2, characterized in that the composition of the charge mixture in the area of the area ABEF in the triangular coordinate system of the F i g. 1 and CaF _{2 is added} to the feed mixture in an amount of 0.2 to 1 percent by weight based on the feed mixture. 4. The method according to claim 1 or 2, characterized in that the composition of the charge mixture in the area of the area EFGH in the triangular coordinate system of the F i g. 1 and CaF _{2 is added} to the feed mixture in an amount of 0.2 to 5 percent by weight based on the feed mixture. 5. The method according to claim 1 or 2, characterized in that the composition of the charge mixture in the area of the area GHDC in the triangular coordinate system of the F i g. 1 and CaF _{2 is added} to the feed mixture in an amount of 5 to 10 percent by weight based on the feed mixture. 6. The method according to 'Xnspruch 1 or 2, characterized in that the composition of the Bcschickungsgcmisches in the area of the area ABEF in the triangular coordinate system of FIG. 1 sets and Na ₁ AIFi; to the feed mixture in an amount of 0.2 to 5 percent by weight, halogen on the feed mixture. is added. 7. The method according to claim 1 or 2, characterized in that the composition of the charge 11 ngsgcmisches in the area of the area IiFGiI in the triangular coordinate system of FIG .] And Na ₃ AlF ₀ to the charge mixture in an amount of 0.2 to 0, 5 percent by weight. based on the feed mixture, is added. 8. The method according to claim 1 or 2, characterized in that the composition of the feed mixture in the area of the area GHDC in the triangular cocrdinate system of FIG.] And Na ₃ AlF ₆ to the feed mixture in an amount of 2.5 to 5 percent by weight, based on Feed mixture, is added.