CA2076869A1 - Process for producing a hydraulic binder (i) - Google Patents

Abstract

ABSTRACT

In a hydraulic binder based on Portland cement clinker, care is taken that the maximum hemihydrate content does not exceed a certain maximum amount. A carbonate donor and at least one iron-complexing compound are utilized as additives for regulating the properties of the binder. By controlling the hemihydrate content, it is possible to set the properties (workability, setting time, early and long-term strength) in a reproducible fashion. The binders according to the invention are distinguished by low sensitivity of the proper-ties with respect to changes of the parameters (for example, water/cement ratio, processing tempera-ture).

Description

CERTIFIED TRANSLATION

PROCESS FOR PRODUCING A HYDRAULIC BINDER (I) Field of Art The invention relates to a process for the production of a hydraulic binder for use in a mortar or concrete mixture, the properties of which, such as workability, setting time, short-term and/or long-term strength, are to be regulated by additives.
The invention furthermore concerns a hydraulic binder for the production of concrete having a high short- and long-term strength, based on a ground Portland cement clinker with calcium sulfate phases and additives to regulate workability and setting time.

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State of the Art The hydraulic binders encompass diverse standardized cements, Portland cement being the main representative. The latter consists essentially of highly basic compounds of lime with silicic acid (SiO2), aluminum oxide (A12O3) and iron(III) oxide (Fe2O3). This cement contains, as the secondary ingredients, oxide forms of magnesium, alkalis, titanium and manganese. The mineral structure of Portland cement consists of C3S (tricalcium silicate), C2S (dicalcium silicate), C3A (tricalcium aluminate) and C~AF (tetracalcium aluminoferrate).
In accordance with the standard (ASTM
C150, DIN 1164), Portland cement is produced by fine grinding of Portland cement clinker with calcium sulfate (gypsum). The approximate chemical composi-tion of Portland cements is as follows:

SiO218 - 33 % by weight A12O33 - 7 ~ by weight Fe232 ~ 4.5 % by weight CaO 60 - 65 % by weight SO3 2 - 4 % by weight Generally known properties of commercially available ordinary Portland cements are, inter alia, the relatively low short-term strengths as well as the 2~68~
low durability and resistance with respect to environ-mental influences, such as, for example, frost, salt of condensation, and sulfate-containing waters. The unsatisfactory durability is essentially due to the porosity of the mortar and concrete mixtures prepared with the binder, this porosity being high on account of the rather high water/cemen~ values (about 16-18 vol-%).
Another disadvantage in the ordinary Portland cements is the considerable volume contraction (shrinkage) after setting.
In the construction industry and in the building trade, there has been for a long time and for a wide field of special applications a need for a hydraulic cement having high short-term strengths and a low lS porosity.
Increased strengths can be obtained ~o a limited extent in Portland cements even without additives.
This is possible, on the one hand, by increasing the fineness of grain (Blaine 4000-5500 cm2/g), on the other hand, by increasing the C3A content. However, problems reside in that the water requirement of the cements rises undesirably with the grinding fineness and the sulfate stability fades with an increasing C3A content.

2'~ 9 It is known that the durability and, in particular, the attainable strengths increase with a decreasing porosity of the mortar or the concrete mix-ture. For this reason, enormous strength increases can be obtained by reducing the water/cement ratio. In order to yet maintain the flowability of the fresh concrete at a level required for working, so-called liquefiers (sulfonated formaldehyde resins or ligno-sulfates) are utilized. The water requirement of Port-land cements can thus be lowered to 30~ (usually about50%~ and, when furthermore using additives, such as microsilica, down to 20%. Compressive strengths of up to 24 MPa could thereby be obtained 8-12 hours after production of the concrete mixture.
High short-term strengths (15-20 MPa earlier than 6 hours after preparation of the fresh concrete) are obtained with extremely finely ground Portland cements only with the addition of chemical activators, such as calcium chloride, or alkali activators, such as alkali hydroxides, carbonates, aluminates, silicates.
Frequently, the activators are utilized in conjunc~ion with liquefiers and set-retarding agents. The cited additives can also be used with the desired effect in hydraulic binders markedly different from Portland cement in their composition (for example, in calcium fluoroaluminate and calcium sulfoaluminate cements).

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Such binder formulations with high short-term strength are utilized, above all, as spray con-crete or dry mortars for concrete work wherein a saving in time is accompanied by an enormous saving in cost, such as, for example, when repairing roadway, garage, and landing strip surfaces, or molds for metal casting operations.
A hydraulic binder is known from US 4,842,649 which hardens reliably at high as well as low tempera-tures, especially below the freezing point of water.
This binder, known under the trade name of "Pyrament", consists of 50-80% by weight of Portland cement and diverse additives, such as, for example, fly ash from coal-burning power plants, blast furnace slag, meta-kaolin, microsilica, as well as activatlng additives,such as alkali hydroxides or carbonates and, if neces-sary, citric acids and citrates as setting retardexs.
The high short- and long-term final strengths of cor-responding concrete formulations axe apparently due to the activation and acceleration of the puzzolanic reaction between hydroxides and silicate or alumino-silicate materials.
The conventional binders have the drawback of a large number and quantity of, in part, expensive ad-ditives (microsilicate, metakaolin) to the Portlandcement, requiring an expensive mixing procedure.

2 ~ 6 9 Furthermore, practical experiments showed that the setting times can only be controlled with great difficulties.
JP 59-064 551 discloses a spray concrete formulation wherein a carboxylic acid, especially citric acid or citrate is added as a retarding agent to a mixture of Portland cement, calcium aluminate cement and alkali carbonate. In this way, high early as well as final strengths are to be obtained with good workability.
For many applications, adequate workability time is absolutely necessary. Therefore, the re-producible adjustability of the setting time of concrete mixtures of high early strength is of central importance.
Practical experiments have shown that all binders known thus far for obtaining high-early-strength concrete have the disadvantage that the regulation of the setting times can be only insufficiently reproduced.
Furthermore, many of the known special cements are sensitive, with regard to their properties (workability, setting time, strength development), to changes in the wat~r/binder ratio and the temperature during fresh concrete production.
On account of the aforementioned drawbacks, the use of the conventional high-early-strength hydraulic binders has remained limited to a few applications insignificant in volume.

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Description of the Invention It is, then, an object of the invention to indicate a process for the production of a hydraulic binder avoiding the disadvantages inherent in the state of the art and, in particular, making it possible to regulate, in reproducible fashion, the workability, settlng time, early and/or long-term strength by the controlled admixture of additives.
This object has been attained according to this invention by using, in a process of the type mentioned in the foregoing, a Portland cement having a specific maximum calcium sulfate hemihydrate content.
The basic aspect of the invention resides in the realization that, in activated hydraulic binders based on Portland cement or, respectively, Portland cement clinker, the calcium sulfate phase exerts a decisive influence on the properties of the fresh and of the hardened concrete. The efficiency and, in part, the basic mode of effectiv ness o~ additlves depend to a large extent on the calcium sulfate hemihydrate con-tent.
This is so because the additives ~such as, for example, citric acid and potassium carbonate) do not only affect the reactivity of the clinker phases but also react with the calcium sulfate phases. The reaction products of the last-mentioned reactions play a large 2 ~
part in the evolution of strength. The cause of this appears to be the reactions of the additives occurring before the cement hydration and/or taking place in parallel thereto: Dissolved carbonate or bicarbonate reacts with the calcium sulfate phases ~dihydrate, hemi-hydrate) within a minimum time period (in the relevant concentration ratios within less than 1 minute) to calcium carbonate and potassium sulfate. In concen-trations of less than 1% by weight, this reaction product contributes, as desired, to an increased early strength.
However, in excessively high concentrations ( ~ 2~ by weight~, it primarily reduces the long-term strengths.
The conversion from the dihdyrate into calcium carbonate and potassium sulfate can be controlled by suitable additives (e.g. potassium citrate).
It can clearly be seen from the above that it is necessary, for controlling the aforementioned re-actions, to consider not only the quantities and molar ratios of the additives but also the amounts of the reacting calcium sulfate phases, i.e. especially the calcium sulfate hemihydrateO
During the simultaneous grinding of Portland cement clin~er and gypsum (dihydrate), an uncontrolled amount of hemihydrate is formed in the customary large industrial plants in dependence on the production con-ditions. If then such Portland cements which/ though confirming to the norm, are not defined with regard to 2~7~
their hemihydrate content are mixed for producing hydraulic binders simply with certain amounts of ad-ditives, then the properties of the corresponding concrete formulation are left to coincidence. Thus, being cognizant of the relationships underlying this invention, it is not surprising that the reproducibility of the attained results was unsatisfactory in the prior art.
When mixing, according to the invention, a Portland cement with a known hemihydrate content with activating and/or retarding additives, then the proper-ties of the corresponding concrete formulation are set in a reproducible fashion. The quantities and propor-tions used in adding the various additives depend on the desired early and long-term strengths, the setting period, and the workability.
Experiments have shown that setting times, consistency, and strengths are advantageously insensi-tive to changes in the xelevant parameters in the binder (clinker composi~ion, clinker quality, calcium sulfate content, amount of additive, water/cement value) if (calculated as the dihydrate~ there is less than 50% by weight, especially less than 20% by weight of the calcium sulfate in the form of the hemihydrate.
With a decreasing hemihydrate content, the sensitivity herein is likewise diminished.

2~76~3 In accordance with an especially preferred process, the Portland cement clinker is first ground free of gypsum and only thereafter there are admixed a calcium-sulfate-containing additive and at least one activating, strength-raising additive, at temperatures of less than 120 C, preferably less than 70 C. By the gypsum-free grinding step, the production of hemihydrate is excluded.
A process for producing a Portland cement suitable for the production of a binder according to this invention is distinguished in that Portland cement clinker is ground up together with a given amount of dihydrate. The process temperature and/or the moisture is set during the grinding step so that the calcium sulfate hemihydrate content of the thus-produced Port land cement does not exceed a predetermined maximum value. The hemihydrate content is determined by measurements conducted at specific time intervals.
This method has the advantage that the conventional large industrial plants can be utilized with low technical expenditure (device for determining the hemi-hydrate content) for the manufacture of the Portland cement according to this invention.
Another possibility of manufacturing a Port-land cement resides in that Portland cement clinker is ground up together with a given quantitative ratio of dihydrate and anhydride so that the calcium sulfate hemihydrate content of the thus-manufactured Portland cement does not exceed a predetermined maximum value.
Also this process can be implemented without any problems with the conventional installations. Both versions share the advantage ~hat the gypsum need not be ground separately.
A hydraulic binder for producing mortar mix-tures or concrete mixtures having a high early and long-term strength, based on a Portland cement clinker, a calcium sulfate phase and additives for regulating workability, setting time, early and/or long-term strength, is distinguished according to the invention by a defined maximum calcium sulfate hemihydrate content of less than 50% by weight, calculated as the dihydrate.
A hemihydrate content of less than 20% by weight is advantageous especially in case the additives include potassium bicarbonate.
A calcium-sulfate-containing additive is suitable for admixture in order to prolong the setting time. This additive preferably has the form of gypsum, anhydrite, or a mixture of both.
The quanti~y of the calcium-sulfate-containing additive is preferably dimensioned so that the calcium content of the binder, calculated as CaSO4, ranges be-tween 0.7% by weight and 8% by weight. Thereby, thesetting times can be regulated between 0 and maximally 2~3~
300 minutes by the amount of CaSO4 added without any significant effect on the strength development.
Preferably, at least one carbonate donor and at least one iron-complexing compound are used for S increasing the strength. Suitable carbonate donors are water-soluble salts of carbonic acid. As the iron-complexing compound, any compound can be used which enters into stable, soluble complex linkages with iron(III) in an aqueous phase in an alkaline medium (pH ~ 10~.
Along these lines, especially preferred are water-soluble salts of polyoxycarboxylic acid or of poly-carboxylic acid, or a diketone~ Quite generally, compounds can be used as the carbonate donor or carbonate generator which release carbonate ions in an alkaline aqueous medium or which react with reactive calcium com-pounds ("Portlandite" Ca(OH)2, C3A, C3S, etc.) to calcium carbonate and/or compounds that contain calcium carbonate.
(carboaluminate 4CaO CaCO3 llH2O, carboalumino-ferrite, taumasite, carboaluminosilicate, etc.).
Potassium bicarbonate is utilized as the carbonate donor preferably in case of a hemihydrate content of less than 20% by weight.
The higher the content of C3A, the lower should be the hemihydrate content. Thus, for example, with a proportion of more than 8~ by weight of C3A and a proportion of more than 0.9% by weight of K2O, the 2~6~9 hemihydrate content should be less than 5% by weight.
With a proportion of more than 9% by weight of C3A and a proportion of more than 1% by weight of K2O, a hemi-hydrate content of less than 1~ by weight is preferred.
In accordance with an especially preferred embodiment, at least one iron-complexing compound is utilized in combination with soluble carbonates or soluble salts and compounds of carbonic acid for shorten-ing the setting times and for increasing the early and long-term strengths. The iron-complexing compound is to be admixed to the binder in the dry state.
This is so because it has been found sur-prisingly that the activation of the ferrite phase, considered to be nonreactive, leads advantageously to a regulation and/or setting of the properties of the binder. Therefore, the use of iron-complexing com-pounds results in shortened setting times and in raised strengths, especially in increased early strengths.
The activation of the ferrite phase according to this invention can be used primarily in case of clinkers having a ferrite proportion of at least 4% by weight, preferably 6% by weight.
A preferred binder is distinguished in that the additives contain a proportion, based on the clinker, of at least 3 mmol-~ of an iron-complexing compound and a carbonate donor in a molar ratio of between 0.3 and 4 based on the iron-complexing compound. A mortar mixture 20~8~
or concrete mixture produced with such a binder is distinguished by a low sensitivity of the properties with respect to changes in the water/cement ratio.
With a suitable choice of the concentration ratio of the activators (carbonate donor/iron-complexing compound), the ferrite clinker phase, generally con-sidered to be nonreactive, is hydrated the fastest (af er 24 hours to an extent of 100%) and thus con-tributes substantially to the evolution of the high early and long-term strengths.
Typically, in a binder according to this in-vention, the molar ratio of sulfate to the iron-complexing compound is within a range of between 1 and 20. A molar ratio of between 3 and 8 is particular-ly preferred.
The above-mentioned low sensitivity of the propertles with respect to changes in the molar ratio is present especially in case this ratio is in a range of between 1 and 3.

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In contrast to the conventional binder formula-tions, the need for water decreases in this invention with rising grain fineness. For this reason, use is advantageously made of Portland cement clinkers and, respectively, Portland cements in a grinding fineness according to Blaine of at least 4000 cm2/g. Good results can be achieved in the range from 4500 cm2/g to 5500 cm2/g. It is thus unnecessary to utilize the Portland cement clinkers and, respectively, Portland cements that are ground with great fineness (8000 cma/g and more) and are thus expensive.
The additives preferably contain as the carbonate donor salts of carbonic acid which are soluble in water as well as those which show low or no solubility therein. Calcium carbonate, magnesium carbonate and/or dolomite are particularly well suit-able. The salts showing low up to no solubility have been preactivated by grinding and/or thermal treat-ment. The amount of the salts of low to no solubility in water is preferahly between 2 and 20~ by weight.
Water-soluble salte of carbonlc acid, in particular aIkali carbonates and/or alkali hydrogen carbonates are preferably used as the carbonate donor, and water-soluble salts of polyoxycarboxylic acid or of polycarboxylic acid, or a diketone, are used as the iron-complexing compounds. Suitable as the carbonate donor is potassium carbonate, potassium carbonate ,.

2~76~69 trihydrate and potassium bicarbonate. Such carbonate donors are preferably combined with iron-complexing compounds, such as tripotassium citrate monohydrate or a mixture of dipotassium oxalate monohydrate and tripotassium citrate monohydrate, the proportion of dipotassium oxalate monohydrate amounting to less than 50 mmol-%.
The iron complexes according to this invention of polyoxycarboxylic acids, polycarboxylic acids and diketones have the advantage that they are relatively strong, especially in comparison with iron-amine com-plexes.
Citric acid, a polyoxycarboxylic acid, is an especially effective complexing agent for iron. The advantage of the citrate resides in that the activating effect is multiplied by the alkali activators, especial-ly by potassium carbonate and potassium bicarbonate.
The activalion of ferrite can lead, in the drying of mortar and concrete, to the formation of undesirable brown spots on the surface. This spot for-mation can be prevented according to this invention by adding 0.1 - 1% by weight of oxalic acid or, respect-ively, its alkali salts.
The additives contain a proportion, based on the clinker, of at least 4.5 mmol-%, preferably at least 7.5 mmol-% of potassium citrate (K3C6H5O7 H2O) .

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The additives can contain, based on the clinker, a proportion of at least 11 mmol-% of citric acid.
The carbonate proportion according to this in-vention ranges between at least 5 mmol-% and at most 25 mmol-%. This makes it possible to attain high early strengths. In order to obtain long-term strength, the additives contain a proportion, based on the clinker, of at least 9 mmol-% and at most 30 mmol-% of potassium bicarbonate.
In order for a mortar or concrete mixture pro-duced with the binder according to this invention to set extensively independently of the ambient temperature, in particular also at temperaiures below the freezing point, it is possible to admix as the additives also puzzolan earths, clay minerals, fly ashes and/or most finely divided reactive silica.
A mortar or fresh concrete according to this invention is distinguished by a hydraulic binder of the above-mentioned type and a water/cement value in a range of 0.25 - 0.4, especially 0.3 - 0.37.
The invention provides the following advantages important under practical conditions:
(a~ high early strengths accompanied by high long-term s~rengths ( ~ 28 d);
(b~ low sensitivity of the strength develop-ment, especially the early strengths, with respect to the Portland cement clinker composition;

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(c) insensitivity of strength evolution with respect to the composition of the customary concrete aggregates;
(d) low sensitivity of the strength evolution, the setting times, and the consistency (workability) with respect to changes in the water/cement ratio (comparable to ordinary Portland cements);
(e) Iow sensitivity of the strength evolution, especially the early strengths and the setting times, with respect to the processing temperature;
(f) low porosity and high durability.

The following can be noted in detail with regard to the advantages:
As for ~a): The evolution of the strength of a mortar or unset concrete mixture according to this in-vention is characterized in that it is possible, with the usual workability (extent of flow 45-50 cm, slump 15 20 cm), to obtain about 30 minutes after the end o the setting process streng~hs of typically 19 MPa, but at least 15 MPa; this corresponds to about 80% of the 6-hour strength values. ~fter 28 days, the strengths are typically around 75 MPa. When using bicarbonate, analogous early strength values can be obtalned 90 minutes after termination of set~ing, but a lower generation of heat occurs during hardening, and ~7~
comparatively higher long-term strengths of about 90 MPa are attained after 28 days.
Thus, according to the invention, the evolu-tion of the early strength and the heat generation during the early hardening phase are regulated by way of a simple change of the initial pH value of the binder mixture.
In contrast to ~he invention, in known actlvated high-early-strength binders (as described, for example, in US 4,842,649), comparable strengths could only be attained with far stiffer concrete mix-tures. At the same time, the high production of heat (especially when using calcium sulfoaluminate and calcium fluoroaluminate cement~ could be affected to an only minor extent, or not at all.

As for Ib): Basically, adequate early strengths can be attained with all Portland cement clinkers of the norm by using a minimum C4AF content of 4% by weight, preferably 6% by weight. Optimum early strengths result with clinkers having at least 9.5% C4AF, wherein the clinker reactivity affects the setting times, but not the strengths.
Differently from the invention, in the binders known from the state of the art, the binder composltion has a substantial influence on the strength evolution, especially on the early strengths.

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As for (c): The grading curve and the compo-sition of the concrete aggregates does affect the need for water, as in the ordinary concrete mixtures, but, at the same consistency, the strength evolution is in-dependent of the type of aggregates. This is in con-trast to the experiences with the heretofore known, activated, high-early-strength Portland cements, especially when using organic liquefying agents.

As for (d): In the invention, the early strengths (2-4 hours) react to changes in the water/ce-ment value approximately with the same sensitivity as the 24-48 hour strengths of ordinary Portland cements.
The same holds true analogously for the consistency and the setting times of fresh concrete. This affords the great advantage in comparison with conventional high-early-strength binders that it is possible to process very liquid (extent of flow ~ 50 cm) and, respectively, liquid (extent of flow 45-50 cm) concrete mixtures in the same way as concrete of ordinary Portland cement without having to forego the high early strengths ac-cording to this invention. The aforementioned proper-ties can be realized with the invention using water/ce-ment ratios of 0.33 - 0.36, without any problems.

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In contrast to the invention, the stxengths, setting times and consistency of the known high-early-strength binders which are based on Portland cement, I liquefiers and activators as well as optionally addi-tives such as fly ash, metakaolin and microsilica react in a very sensitive way to changes in the water/cement ratio. The low watertcement ratio of 0.20 - 0.26 necessary for attaining the known char-acteristic early strengths results in a strongly thixotropic behavior of the fresh concrete and thus greatly restricts its workability and range of usage.

As for (e): In the temperature range (tempera-ture of cement, aggregates and water) of 5 C to 30 C, the early strengths of a concrete mixture according to this invention change merely by about 20%, and the setting times by about 50%. The 24-hour strengths ex-hibit the same temperature sensitivity as ar. ordinary Portland cement of the PS0 type.
In contrast thereto, the conventional ordinary Portland cements are far more sensitive with respect to temperature variations, namely as regards setting times as well as evolution of strength.
Normally, a lowering of the temperature from 20 C to 7 C brings about a slowing down of the strength evolution and setting by a factor of 3. Under the same conditions, in a binder of this lnvention, the setting times increase by a factor of about 1.3.

2~7~8~9 As for (f): Due to the low water/cement values (preferably 0.33 - 0.36), the porosity values in the concrete, as measured after 7 days, lie, in this invention, markedly below those attainable with Port-land cement without additives after 28 days (accordingto the invention, 6 vol-%/g as contrasted to 8-18 vol-~/g in Portland cements without additives). Thereby the durability (shrinkage, creep, frost/dew, frost/salt resistance, sulfate resistance) of the hardened con-crete is clearly better than that of previous concreteswith similar water/cement values.

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Brief Description of the Drawinqs and Tables The invention shall be described in greater detail below with reference to embodiments and in conjunction with the drawings and tables wherein:

Figure 1 illustrates the effect of the hemi-hydrate content on the early strength of a hydraulic binder with potassium carbonate as the additive;
Figure 2 illustrates the effect of the hemi-hydrate content on the setting time of a hydraulic binder;
Figure 3 shows tha influence of the tempera-ture on the dehydration of dihydrate;
Figure 4 shows the effect of the humidity on the dehydration of dihydrate;
Figure 5 illustrates the sensitivity of the properties of the binder in dependence on the carbonate/citrate ratio;
Figure 6 shows the influence of water, carbonate donor and potassium itrate on the compres-sive strength in dependence on the type of clinker and on the carbonate donor;
Figure 7 illustrates the dependency of the 6-hour compressive strength on the C4AF content when using potassium bicarbonate as the carbonate donor;
Figure 8 shows the dependency of the 6~hour compressive strength on the C4AF content when using potassium carbonate as the carbonate donor;

- 24 - 2~ 9 Figure 9 shows the correlation between the gypsum content (in % by weight) and setting time (in minutes);
Figure 10 shows the strength evolution (compressive strength in MPa, time after setting in hours) for various dihydrate contents;
Figure 11 illustrates the dependency of the 4-hour strength of a binder according to this invention on the water/cement ratio in comparison with the 24-hour strength of a conventional Portland cement freeof additive;
Figure 12 illustrates the dependency of the 4-hour and 24-hour strength on the water/cement value, as compared with a conventional high-early-strength binder, in case of a binder of this invention;
Figure 13 shows the temperature dependency of the early strength of a binder according to this inven-tion as compared with the 48-hour strength of a known high-early-strength cement;
Figure 14 illustrates the dependency of the flowability (FLOW) on the water/cement value with a binder according to the invention in comparison with a conventional high-early-strength binder.

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Tables 1.1 - 1.3 show a compilation of the clinkers and Portland cements utilized in the examples;
Table 2 shows the effect of the gypsum phase and the advantageous acti.on provided by the admixture of calcium-sulfate-containing additives to clinkers ground devoid of gypsum;
Table 3 shows the influence of the addition of gypsum when using potassium carbonate as the additive;
Table ~ illustrates the effect of the addition of gypsum when using potassium bicarbonate as the additive:
Table 5 shows the effect of various calcium sulfate phases on the properties of the binder;
Table 6 shows the effect of potassium citrate on the hardening characteristic of Portland cement in ISO mortar;
Table 7 shows the effect of potasslum bi-carbonate and potassium citrate on the cement hardening process;
Table 8 shows the effect of alkali carbonate and potassium citrate on cement hardening;
Table 9 shows an example with the addltives citric acid and potassium carbonate;
Table 10 shows hydration of the clinker phases in dependence on the time, - 26 - 2~7~

Tables 11 and 12 show the effect of tne hemihydrate in the presence of dihydrate on the properties of the binder at various formulations of the activating additive;
S Table 13 shows properties of formulations with various proportions of citrate and, respectively, citric acid;
Table 14 shows a comparison of potassium carbonate and potassium bicarbonate at various water/cement ratios;
Table 15 shows clinker ground without gypsum with varying amounts of dihydrate and hemihydrate wherein the additives contain, on the one hand, citrate and, on the other hand, citric acid, each in combination with potassium carbonate;
Table 16 shows several especially preferred embodiments;
Table 17 shows examples having particularly high early strengths;
Table 18 shows the influence of the addition of dipotas~ium oxalate, on ~he one hand, in conjunction with potassium carbonate and, on ~he other hand, with potassium bicarbonate;
Table 19 shows variance and confidence ranges of the 4-hour strength of binders according to this invention.

- 27 - 2~7~69 The following expressions and abbreviations are utilized, inter alia, in the figures and tables:

DF compressive strength W/C water/cement ratio CSTR compressive strength (in English) SET setting time FLOW flowability DH dihydrate HH hemihydrate content A anhydrite A nat. natural anhydrite A sol. soluble anhydrite CITR.AC citric acid K3C tripotassium citrate monohydrate PZ Portland cement ~ PK Portland cement clinker :: .

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Ways of Executinq the Invention As mentioned above, the basic aspect of the invention resides in the realization that the calcium sulfate hemihydrate content, called briefly HH content hereinbelow, exerts an essential and, in the manner manifested, unexpected influence on the various proper-ties, such as water requirement, workability, setting time, and early strength of a hydraulic binder and, re-spectively, the mortar mixture or concrete mixture produced thereby.
Furthermore especially significant for the practical application is the realization that the sensi-tivity of the properties of the binder to changes of the parameters, such as, for example, clinker quality and processing temperature, is determined to a substan-tial extent by the HH c~ntent. Thus, it has been found, for example, that the setting times in the presence of relatively large amounts of hemihydrate react in a very sensitive fashion to parameter changes. Thus, if a binder based on commercially obtainable Portland cements unspecified or unspecifiable(!)intheir HH
content is provided with additives for regulating the relevant parameters, such as setting time, early strength, etc., then this leads to more or less coincidental results.

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In other words: If the HH content is not considered during the production of the binder, especially during the selection and dimensioning of the additives, then this will lead, in principl~, to accidental properties of the product. In contras-t thereto, if the HH content is taken into account in -correspondence with this invention, then binders can be produced having reproducible properties. In a certain sense, by controlling the HH content, the "hit probability" and the "variance" of the properties regulated by additives are considerably improved and, respectively, reduced as compared with the state of the art.
Figure l illustrates the above remarks with the use o~ an example. In the illustration, the HH
content is plotted on the abscissa in percent (cal-culated as the dihydrate) and on the ordinate, on the one hand (on the left),the 6-hour early strength and, on the other hand (on the right), the water/cement ratio at constant flowability (FLOW~ are plotted.
The binder, based on a Portland cement clinker, contained 6~ by weight of gypsum and was activated with 1.85% by weight of K2CO3 and 2.7~ by weight of K3C.
It can be seen from the illustration that (with constant flowability~, on the one hand, the water/cement ratio rises strongly and, on the other - 30 - 2~ 9 hand, the early strength is greatly reduced as soon as the HH content is more than 50~. If, conversely, the water/cement ratio were to be maintained constant, then the flowability would decrease correspondingly with S an HH content of more than 50%.
Figure 2 shows an illustration of the effect of the hemihydrate content on the setting time of a hydraulic binder. The HH content is plotted on the abscissa in % by weight (calculated as the dihydrate) and the ordinate shows the setting time in minutes.
The measured values relate to a Portland cement clinker ~type PK1/5) ground without gypsum to a fine-ness of Blaine 5000 cm2/g; as the calcium-sulfate-containing additive, 5% by weight of a mixture o~
varying propor~ions of dihydrate and hemihydrate had been added to the clinker. The activating additive (4.6% by weight) contained 41~ of potassium carbonate ~K2CO3) and 59% of potassium citrate monoh~drate.
The illustration demonstrates that, with the binder mixture activated in the aforementioned way, the setting time is greatly reduced wi~h a high HH
content; in the worst case, setting takes place during the mixing of the mortar mass (FLASH SET) .
It can clearly be seen that with a hemi-hydrate content of more than 50% (calculated as thedihydra~e) in the aforementioned mixture (K~CO3), the setting time is undesirably strongly reduced. With the _ 31 - 2~7~

same clinker and an activating additive containing 43% by weight of potassium bicarbonate (KHCO3) and 57% by weight of potassium citrate monohydrate, the excessively strong reduction occurs with a hemihydrate content of more than 20%.
The examinations explained by way of example with the aid of Figures 1 and 2 thus make it clear that the properties of a hydraulic binder can be reliably regulated with the aid of activating additives only if the HH content of the binder is known or, respectively, specified. The additives are to be selected and dimen-sioned in dependence on the (maximum) HH content.
It is normally sufficient for the maximum HH
content in the binder not to exceed a predetermined value. As can be derived from Figures 1-3, this value in case of the potassium carbonate is preferably about 50% and in case of the potassium bicarhonate preferably about 20%. In most instances, a low HH content will have a positive effect on the reproducibility and will enhance the low sensitivity (with respect to changes in parameters).
Therefore, it can be stated in general that the hydraulic binder should preferably exhibit a maximally low HH content. Thus, the question arises 2S how the HH content can be controlled.

- 32 - 2~ 6 g ~9 First of all, it is to be noted that the calcium sulfate hemlhydrate (CaSO4 0.5H2O) is formed during the production of cement by dehydration of the gypsum (= dihydrate = CaSO4 2H2O) during grinding of the clinker with the gypsum. In ordinary Portland cements manufactured according to standard procedure, the calcium sulfate phase is present, in dependence on the grinding conditions (temperature, humidity), in varying amounts as the hemihydrate. The HH content is high, in partlcular, if the grinding step is continued to high grain fineness (which is definitely desirable in case of ordinary, i.e. nonactivated cements).
Figure 3 shows the influence (known per se) of the temperature on the dehydration of gypsum. On the abscissa, the time is plotted during which the gypsum has been exposed to a certain temperature, in minutes, and the dehydration is plotted in percent on the ordinate. It can be seen from the graphic il-lu~tration that gypsum exposed to a temperature of 130 C for 30 minutes has been converted al~ost to an extent of 100% into calcium sulfate hemihydrate. At 110 C, however, only just about 50% are dehydrated within the same time period.
Figure 4 illustrates the influence (likewise known per se) of the humidity on the dehydration of dihydrate. As in Figure 4, the dehydration is plotted 2 ~
in percent with respect to the effective time (in min-utes). It can be seen from the illustration that it varies between 60% and 90%, at a temperature of, for ex-ample, 120 C and an effective time of about 30 min-utes, depending on the moisture content (defined by thedew point) of the air.
In the generally known processes for the manufacture of Portland cement, the grinding temperature fluctuates typically between 100 and 160 C. In this process, the temperature will be lower when the mill is switched on than in continuous operation. Also the residence time in the mill will vary. ~inally, the temperature and humidity of the air will likewise have an effect; this air is utilized for blowing the fine grain proportion out in the screening device. All of this leads to the fact that the HH content is entirely undefined in the commercial Portland cement.
It is to be noted, in this connection, that in case of additive-free Portland cements a high hemi-hydrate content is definitely desirable. In accordance with a generally recognized teaching, there is a direct correlation between a high hemihydrate content and high strength (compare, for example, "Materials Science of Concrete I", Jan P. S~alny, The American Ceramic Society, Inc., Westerville, 1990, pages 32, 33; or "Cement Chemistry", H.F.W. Taylor, Academic Pres , London, 1990, Section 7.6.2).

2 ~
In order, now, to produce according to this invention a Portland cement having a specified HH
content, Portland cement clinker is ground together with a given amount of dihydrate wherein the process temperature and/or the moisture ls set so that the calcium sulfate hemihydrate content of the thus-produced Portland cement does not exceed a predetermined value.
Preferably, the HH content is measured at certain (regular or irregular) time intervals and, in case of too high an HH content, the temperature is reduced (be it by cooling the mill by means of injection of water or by injecting cold air into the screening device).
Selectively, it is also possible to exploit the effect of atomspheric humidity on the dehydration in order to set the HH content.
Preferably, the parameters of the grinding step are adjusted so that the HH content directly after the grinding operation lies at most at 50%, especially at most at 20%.
Another possibility for controlling the max-imum HH content which likewise is within the scope of this invention resides in grinding Portland cement clinker together with a given quantitative ratio of dihydrate and anhydrite so that the calcium sulfate hemihydrate content of the thus-produced Portland cement does not exceed a predetermined value.

2~6~
A maximum HH content of, for exmaple, 50~ in the Portland cement can thus be ensured by grinding the Portland cement clinker with a mixture of 50% dihydrate and 50~ anhydrite. Since hemihydrate can be formed only from the dihydrate, the maximum proportion of hemihydrate cannot be larger than the maximum proportion of dihydrate (in the present example 50%).
For lowering the HH content of the Portland cement or, respectively, of the hydraulic binder, it is also possible to admix subsequently separately ground gypsum and/or anhydrite.
It has been found that binders containing ex-clusively dihydrate are comparatively insensitive with respect to changes in the parameters characteristic for the binder. This also holds true, to a somewhat lesser degree, for anhydrite.
Therefore, an especially preferred embodiment of the invention provides to use, for the binder, Portland cement clinker ground without gypsum and to subsequently admix gypsum and/or anhydrite. The formation of hemihydrate (and be it merely to a controlled extent) is precluded from the beginning.
The advantages at~ainable by the absenGe of hemi-hydrate have been impressively proven by Figures 1 and 2.

~ - 36 - 2~

Various methods have been described for the production of Portland cements having a specified hemi-hydrate content. In this connection, it is to be noted that the hemihydrate content is not a constant magnitude.
This value can change during the course of time owing to the type of storage of the product. Therefore, logically, the hemihydrate content is to be related to a specific point in time. In case the manufacture of a Portland cement usable in accordance with this inven-tion is involved, then the hemihydrate content is basedon the instant directly after production of the cement.
In case the production of the binder proper is involved, then the relevant point in time is determined by the conclusion of the mixing process.
The HH content can be measured by means of conventional methods (compare, for example, V.
Schlichenmaier, Thermochimica Akta 11, 197S, pp. 334 to 338). Corresponding devices are commercially available.
During the course of time, the hemihydrate content of the binder will normally change. On the one hand, the dihydrate as well as the hemihydrate will change into anhydrite. On the other hand, the hemi-hydrate will also react with calcium sulfate to syngenite.
Also the additives (activators) enter, with time, into undesirable reactions. Seen from ~his viewpoint, no advantages are o~tained by storing a binder under "suitable" conditions until the hemihydrate content has become negligibly low. Rather, the binders of this invention should be utilized in maximally fresh condition.
S The following description addresses the diverse, preferred additives. The basis for a binder according to this invention is constituted by a ground clinker having a ferrite proportion of at least 4% by weight, preferably a ground Portland cement clinker, and a calcium-sulfate-containing additive that has been ground up either together with the clinker or separately.
The cement or the gypsum mixed with the clinker ground in gypsum-free condition constitutes80-95% by weight of the binder. The remaining weight proportions are provided by the activators according to this inven-tion.
According to the invention, it is advantageous not to exceed 120 C, especially 70 C, during the intermixing of the activators. Depending on the binder composition, it is possible for excess temperatures to result in undesirable secondary effects (such as, for example, uncontrolled variation of the setting times~.

2 ~
In accordance with an especially preferred embodiment of the invention, additives are utilized as activators which contain, on the one hand, soluble salts of carbonic acid and, on the other hand, iron-S complexing, preferably pH neutral to basic compounds.These agents are used to regulate, on the one hand, the strengths, particularly the early strengths, and, on the other hand, the setting times. The iron-complexing compound (for example, potassium citrate monohydrate) here acts surprisingly as an acti~ator rather than as a retarding agent, i.e. it accelerates the setting process and increases the strength.
Advantageously, the iron-complexing compound is added in an amount of at least 3 mmol-% (based on the clinker). The soluble salts of carbonic acid (e.g.
potassium carbonate) acting as the carbonate donor are added in a molar ratio, based on the iron-complexing compound, of between 0.3 and 4. Advanta-geous properties result from the selection of the molar ratio according to this invention; these will be explained hereinbelow with reference to an example.

- 39 ~ 2~76~9 Figure 5 depicts the sensitivity of various parameters with respect to changes in the water/cement value (by 9%) in dependence on the ratio of carbonate to citrate. While the flowability (FLOW), the 6-hour and the 24-hour strengths are only slightly sensitive in the range between 1.5 and 4.5 (molar ratio), the sensitivity of ~he 4-hour strength and the setting time (SET) greatly increases with the molar ratio, with carbonate/citrate values of larger than 3 to 3.5.
In other words: if, in the example on which the il-lustration is based, the carbonate/citrate ratio is selected to be smaller than 3, then the aforedescribed properties are extensively insensitive to changes in the water/cement ratio.
The qualitative information provided by Figure 5, namely the existence of a molar ratio range wherein the pxoperties are insensitive to parameter changes, holds true ~or all activators according to this invention. In a quantitative respect, i.e. as to exact locations of the limits, there may be differences among the various activator combinations. Thus, it can be that, for certain activator combinations, the desired effect will occur already at molar ratios of smaller than 4 whereas this will be the case for others only below 3.

- 40 - 2~7~

The most advantageous results as regards strength development, workability and sensitivity are achieved with a binder according to this invention by mixing 80-95 parts of Portland cement clinker with a calcium-sulfate-containing additive and an effectively strength-raising additive in the dry condition. In this connection, the Portland cement clinker is ground, without addition of gypsum, to a fineness of 4000-6000 cm2tg, preferably to about 5000 cm2/g ac-cording to Blaine.
The calcium-sulfate-containing additive contains gypsum (CaSO4 2H2O) and/or anhydrite (CaSO4). It is produced by grinding gypsum and/or anhydrite, optionally with limestone and/or other inert additives to grain sizes of smaller than 120 um, preferably smaller than 60 um and 90% larger than 2 um.
Grinding of the calcium-sulfate-containing additive can be performed in a customary open ball mill, in a dish-type roll mill, in a micro turbulence mill, or in some other way. The grinding temperatures and the storage temperature should lie below the formation temperature of hemihydrate (lower than 70-80 C~.
It is also possible to use, as the calcium-sulfate-containing additives, for example, residual materials from the chemical industry (citro-gypsum, phosphogypsum, gypsum from titanium dioxide processing, etc.) or residual substances from the flue gas - 41 - ~7~

desulfuriæation. If these additives are available in the required fineness, they can be added directly.
Otherwise they are to be ground up as described above.
The calcium-sulfate-containing additive is S admixed in an amount so that the binder contains 0.7 - 8% by weight of gypsum and/or anhydrite (cal-culated as CaSO4). With this additive, the settiny time is set to a certain basic value of between 0 and 300 minutes. The development of the strength is not significantly affected thereby.
The effectively strength-increasing additive contains at least one iron-complexing compound and at least one carbonate donor or, respectively, carbonate generator.
As the iron-complexing compound, any compound can be employed which enters, in an aqueous solution in an alkaline medium (pH ~ 10) with iron(III) into stable, soluble complex compounds. Among the latter are the representatives of the polyoxycarboxylic acids, such as citric acid, tartaric acid, lactic acid, gluconic acid, malic acid, etc., and their salts;
also representatives of the polycarboxylic acids, such as oxalic acid, maleic acid, malonic acid, succinic acid, etc., and ~heir salts. Finally, also suitable are representatives of diketones, such as pyruvic acid, acetylacetoacetate, dimethylethylsuccinate, etc., and their salts. In principle, i~ is also possible to use - 42 - 2 ~7 68 g9 hydxoquinoline, amine, pyridine, glyoxime and similar compounds. The latter are less preferred because of certain drawbacks, such as toxicity, odor, or cost.
Especially preferred properties are attained, for example, with the salts of citric acid, particularly with tripotassium citrate monohydrate (K3C) wherein the latter can be partially substituted by a polycarboxylic acid, such as, for example, oxalic acid and/or potas-sium oxalate.
As the carbonate donor or generator, compounds can be utilized which release, in an alkaline aqueous medium, carbonate ions or which react, with reactive calcium compounds, such as Portlandite Ca(OH)2, C3A, C3S, etc., to calcium carbonate and/or compunds con-taining calcium carbonate, such as, for example, carbo-aluminates 4CaO CaC03 1lH20, carboalumoferrites, taumasite, carboaluminosilicates, etc.
Soluble salts of carbonic acid, such as alkali carbonates MC03 and/or alkali hydrogen carbonates MHC03 (M - Li, Na, K), but also tetraalkylammonium carbonates act as the carbonate donor. Compounds which release, in aqueous media, carbon dioxide and/or carbonate, such as, for example, compounds of carbamic acid, act as carbonate generators.
In order to increase shelf life, it is also possible to use potassium carbonate trihydrate 2~7~8~

The effective strength-raising additive is produced by mixing its components, preferably in powder form, optionally with fillers and/or other strength-increasing additives (such as, for example, micro-silica, alkali silicates, etc.). The components ofthe strength-raising additive can, however, also be added to the binder individually.
The strength-increasing additive is dimen-sioned in its amount so that the binder mixture con-tains 3-12 mmol-% of iron-complexing compounds (e.g.
0.1 - 4% by weight of potassium citrate monohydrate) and 1 - 40 mmol-% of carbonate donors (e.g. 0.1 - 4 by weight of potassium bicarbonate).
Advantageous results are also obtained by adding 0-10% by weight of sparingly soluble to insol-uble carbonates, such as, for example, calcium carbonate. The aforementioned carbonates can be used separately or jointly with the respective additives as their component or by combined grinding with the Portland cement clinker.
The hydraulic binder of this invention is preferably produced by mixing its componentsin a conventional dry mixer. As mentioned above, the tem-peratureduring mixing should not exceed 120 C or, preferably, 70 C.

2 ~ 7 ~

The advantageous properties of the invention will be demonstrated by the following individual examples and comparative experiments.
In Tables l.l, 1.2, 1.3, the elementary compositions of the clinkers and cements utilized in the examples (calculated as oxides) and the correspond-ing clinker phase compositions, calculated according to Bogue (ASTM C150, modified),are set forth.
Table 2 shows the effect of the gypsum phase (especially the advantageous effect of adding the calcium-sulfate-containing additive) on high-early-strength Portland cement formulations. As the alkali activator, 2% by weight of K2CO3 and, as the retarder, 0.3% by weight of citric acid were added. In Table 2, a comparison is made between clinker ground without gypsum, combined with dihydrate, and the corresponding commercial Portland cements (DH = dihydrate, A =
anhydrite, HH = hemihydrate, DF = compressive strength).
It can be seen from Table 2 that the addi-tion of the effectively activating additive (alkaliactivator and retarder being contained therein) to Portland cemen~ clinker (PZX) grGund without gypsum, mixed with dihydrate, clearly brings advantages as compared with the activation of the corresponding Port-land cement (PZ) with regard to strengths (6 h DF,24 h DF), water requirement (W/C) and regarding sensitivities of the strengths as well as of the setting times (SET).

2 ~ 6 ~
The hemihydrate-free binder (based on clinker ground devoid of gypsum) is characterized by a lower water requirement ~about 10%), longer setting times (35%), higher early strenghts (35%), and higher long-term strengths (5-17%).
Furthermore, the sensitivity of the setting times to changes in the water/cement ratio is markedly lower (34%).
Tables 3 and 4 illustrate the effect of the addition of gypsum on the properties of the binder of this invention, using the comparison of commercial Portland cements with the corresponding Portland cement clinkers, ground without gypsum, which have been mixed with gypsum. The Portland cement clinkers and, if necessary, also the commercial Portland cements were ground to Blaine 5000 cm2/g. Potassium citrate mono-hydrate (iron-complexing compound) was used as activators and potassium carbonate (Table 3) and, respectively, potassium bicarbonate (Table 4) were used for increas-ing the strength. Portland cement clinkers, ground ac-cording to this invention without gypsum, combined with dihydrate, were compared with the corresponding Portland cements in ISO mortar mixtures.
The examples listed in Table 3 contained, as the activa~or, potassium carbonate (K2CO3) in varying amounts of 24-40% by weight, and potassium citrate monohydrate in amounts of 48-49% by weigh~. A relatively 20~6869 reactive Portland cement clinker forms the basis for the first comparison series (lines 1-5). In the remaining comparison tests (lines 6-17), Portland cements were used with HH contents of less than 50%.
Table 4 shows examples for activating additives, the proportion of potassium bicarbonate (KHCO3) of which ranges, depending on the example, between 54 and 75~ by weight, the proportion of potassium citrate monohydrate therein assuming values in a range of between 25 and 57~ by weight.
The results compiled in the two Tables 3 and 4 show that binder formulations, prepared from clinkers, ground without gypsum, of a great variety of re-activities, set, in ISO mortar mixtures of comparable consistency (FLOW), in a relatively narrow range of 80-135 minutes They exhibit strength values for 6 hours of 15-23 MPa and have 24-hour strength values of 36-Sl MPa. In the coxresponding binders made of Portland cements, the setting periods 1uctuate enormously (4 - 620 minutes3. From the viewpoint of the user, such variations cannot be tolerated. In the binders produced from Portland cements, the strength development likewise fluctuates more strongly.
In case of binders containing a small amount up to no amount at all of hemihydrate, the type of clinker and the clinker reactivity thus exert only 2 ~ 6 ~
a moderate influence on the relevant properties. This is in contrast to the results based on binders with a high proportion of hemihydrate. This effect is most pronounced in comparison of PK9/1 with PZ9/1-PZ9/3 (Table 3). The results show that fluctuations of the hemihydrate content due to the manufacturing process can bring about fluctuations in the setting times of 4 minutes (setting in the mixer~ up to 620 minutes (useless as a high-early-strength binder). The formulations containing potassium bicarbonate (Table 4) are, in turn, subjected to enormous fluctuations of the early strengths.
The effect of the hemihydrate content is influenced by the clinker type: In case of clinkers having high C3A contents ( ~ 10%) such as PK9/1-3 !
PK4/2, PK5/2, the hemihydrate causes a multiplication of the setting times. In low-reactive clinkers, such as, for example, PKl/1-5 with a C3A content of ~ 10%, the hemihydrate content brings about a shortening of the setting periods.
The setting times, the consistencyj the early strengths and/or the 24-hour strengths react, in binders wherein the hemlhydrate content is > 20%, with markedly higher sensitivity to changes in the water/cement value than binders which contain no hemihydrate or only a small amount (about 20~). Binder formulations 2~7~
containing potassium bicarbonate furthermore react with greater sensitivity than those containing potassium carbonate.
Binder mixtures of this invention containing predominantly insoluble anhydrite and a small amount ( < 20%) of hemihydrate are extensively insensitive to variations of the parameters and correspond in their behavior essentially to binder formulations containing gypsum-free clinker and dihydrate. However, formllla-tions which contain anhydrite set more rapidly.
Table 5 illustrates the influence of various calcium sulfate phases (dihydrate, a-hemihydrate, ~-hemihydrate, anhydrite insoluble, anhydrite soluble~
on the properties of the binder. The clinker ~PK5/2) was ground gypsum-free to a fineness or 5000 cm2/g ac-cording to Blaine. An amount of 3% by weight of activator was added, consisting to an extent of 66% of K2CO3 and to an extent of 33% of potassium citrate monohydrate.
The comparisons show that binders based on reactive clinker (PK5/2~ (C3S content of 56% and C3A
of 10.5%) show with dihydrate the far most favorable properties with respect to setting time and strength evolution.

- 9 2~7~g~

Highly reactive clinkers, such as, for ex-ample, PK9/2 (61% C3S and 10.4% C3A) react with greater sensitivity to the sulfate carrier than nonreactive clinkers. With anhydrite, the setting times are, in general, significantly shorter than with dihydrate.
However, they can be prolonged by the subsequent addi-tion of dihydrate to the Portland cement ground with anhydri~e The binders indicated at the three bottom lines of Table 5 are unusable on account of lack of early strength.
For they contain too many readily soluble CaSO4 phases and, from this viewpoint, clearly do not correspond to the formulating principles of this invention.
Figure 6 shows the factorial effect of water (coefficient A) toward potassium carbonate or potassium bicarbonate (coefficient B~ and of potassium citrate (coefficient C) on the 6-hour strength of a mortar with various basic binders. The coefficients were determined statistically (following the known mathod of factorial experimental planning) with the aid of the equation set forth below:

- so -2 ~
Y' = 1 + 2(a[A] + b[B] + c[C~ + ab[A][B] + ac[A][C] +
bc[B][C] + abc[A][B][C]) Y' = measured variable (6 hour compressive strength), standardized to Y0 ~measured value at central S point) a ... c coefficientsstandardized to Y0 A ... C concentrations (-1 to + 1) standardized to clinkers of A = water, B = potassium (bi)-carbonate, C = potassium citrate It can be seen from Figure 6 that, in the binders according to this invention as tested, based on Portland cement clinkers of a greatly differing com~
position, potassium citrate (especially in the presence of potassium carbonate) is the component determining for the 6-hour strength development.
It can also be seen from Figure 6 that the effect of potassium citrate as well as that of potas-sium carbonate and, respectively, bicarbonate becomes stronger with increasing ferrite content.
Figures 7 and 8 show the correlation of the 6-hour strengths with the C4AF content (determined according to Bogue) o~ a series o~ clinkers activated according to this invention. As the activating additive, a mixture of citrate and bicarbonate was used in the examples of Figure 7, and a mixture of citrate and carbonate was used in those of Figure 8.

2~7~8~9 In the presence of bicarbonate (Figure 7), a positive correlation can be found of the 6-hour strength with the ferrite content of the clinker. In other words, with a rise of the C4AF content from 6~ by weight to about 10% by weight, the compressive strength (DF) of 16 MPa increases to just about 20 MPa. The relationship can be considered to be proportional in the first approximation.
When using potassium carbonate (Figure 8), the rise in strength proceeds in a markedly steeper fashion than in case of the potassium bicarbonate (Figure 7).
According to the invention, citric acid and alkali salts of citric acid exert, due to the activa-tion of the ferrite phase of the clinker according tothe invention, an accelera~ing and strength-raising effect. This is to be explained with reference to Tables 6-9.
Table 6 shows the effect of potassium citrate on the hardening characteristic of Portland cement (Blaine 5000 cmZ/g, 6% dihydrate) in ISO mortar.
Table 7 shows the effect of potassium bicarbonate and potassium citrate on the cement hardening process~
Table 8 shows the effect of alkali carbonate and potasslum cltrate on cement hardening. Table 9 finally shows an example with citric acid and potassium carbonate as additives for increasing the strength.

2 ~
The values set out in Table 6 clearly show the accelerating and early-strength-raising effect of potassium citrate. The setting time is reduced from 240 minutes ~without potassium citrate) to 20, respect-ively 30 minutes with 2% by weight of citrate. Thisis contradictory to the existing teaching according to which citric acid as well as citrate exert a retarding effect.
It can be derived from Tables 7 and 8 that markedly higher strengths(factor 2) are attained with potassium citrate in combination with alkali carbonates and, respectively, alkali bicarbonates. At the same time, the plasticizing effect is enhanced. The addi-tion of alkali carbonate, especially alkali bicarbonate, brings about a prolongation of the setting times as compared with the carbonate-free binders (Table 6).
In the examples of Table 7, the setting time is reduced from 240 minutes (0% by weight of potassium citrate) to 120 minutes (2.7% by weight of potassium citrate). When using potassium carbonate (Table 8), the setting time is reduced from 220 min-utes (1.7% by weight of potassium citrate) to 70 min-utes (with 3% by weight of potassium citrate).
The citrate is also the component essential to obtalning high early strengths in the presence of cæ~onates or, respectively, bicarbonates. The effect of the citrate (high early strengths, reduction of - 53 ~

water requirement) is enhanced by the carbonates. The effect of carbonate, particularly of potassium bi-carbonate, which delays setting in the presence of citrate permits a regulation of the setting time which is practical for commercial applications.
The activating action of potassium citrate, especially in conjunction with bicarbonates, on the ferrite phase, considered to be nonreactive in the state of the art, in the Portland cement clinker is confirmed by determinations of hydrated binder paste carried out by X-ray diffractometry.
Table 10 shows the extent of hydration of the clinker phases, determined by X-ray diffractometry (clinker 1, 6% by weight gypsum).
A 30% hydration of the C3S phase is also definitely customary in nonactivated Portland cements, but here the alkali carbonate or bicarbonate present in the binder of this invention as the carbonate donor leads to the formation of unusually dense, quasi-amorphous silicate hydrates, as they cannot be ob-served in ordinary hydrated Portland cements. These very dense, partial~y sulfate-, potassium-, iron- and carbonate-containing silicate phases contribute with certainty toward an increased early and particularly long-term strenqth. An alkali activation of the silicate phases in the early stage of the hydration (up to 24 hours) cannot be detected, however, in the presence of citrate.

~7~
It is to be noted that the above-described efects can also be observed with a low potassium citrate dosage. Consequently, it appears probable that the salient feature here is not the activation of the C3A phase already observed in the state of the art with high doses of citric acid. This supposition is also supported by the fact that the highest early strengths have been reached in this invention with a sulfate-resistant, C3A-free clinker (clinker No. 7).
Tables 6-10 show that in the investigated binders, potassium citrate, as a representative of a polyoxy- or polycarboxylic acid, is the important component for reaching the high early strengths. The hydration of the ferrite phase, activated by potassium citrate, yields the largest contribution toward the strengths within the firs~ 24 hours after onset of hydration (compare Figure 6).
Potassium carbonate or bicarbonate as the carbonate donor enhances activation of the ferrite and increases the plasticizing effect of the citrate. The aforementioned carbonate donors, on the other hand, retard setting. The prolongation of the resting phase (duration of workability) of the cement paste or of the mortar is due with great probability to the forma-tion of a calcium carbonate protective layer on thesurface of the CaO-containing clinker phase ("carbonate effect").

2 ~
Ordinary Portland cement usually contains 4-7% by weight of gypsum as the setting retarding agent.
This is added in the form of natural gypsum and/or chemical gypsum to the Portland cement clinker before grinding.
In the Portland cement, the gypsum is present as a mix-ture of dihydrate, hemihydrate and anhydrite. The quantitative ratios of the calcium sulfate phases depend to a very great extent on the grinding conditions.
In the binder of this invention, the amount of the calcium sulfate phases and the manner of ad-mixing the calcium-sulfate-containing additives exert an effect on the strength evolution and the setting behavior. Advantageously, dihydrate ~CaSO4 2H2O) is used advantageously for the calcium-sulfate-containing additive wherein the latter can also be mixed with fillers, such as limestone. Alternatively, it is also possible to utilize anhydrite (CaSO4). The early strengths attainable in this case range, however, 10-30% lower than with dihydrate.
If the binder of this invention contains hemihydrate (CaSO4 0.5H2O, respectively CaSO4 0.8H2O), ths strength development and the setting characteristic depend on the type of clinker.
Tables 11 and 12 illustrate the influence of the hemihydrate in the presence of dihydrate on the properties of the binder in dependence on the 2~7~
formulation of the activating additive. Commercial Portland cements are compared with the corresponding clin~ers, ground devoid of gypsum according to this invention, with added dihydrate. The iron-complexing compound employed is, on the one hand, potassium citrate and, on the other hand, citric acid, and the carbonate donor is, on the one hand, potassium carbonate and, on the other hand, potassium bicarbonate The examples in Table 11 have the following chemical and physical parameters:

Commercial Portland cement (PZll) Blaine 5500 cm2/g Dihydrate 1.4% by weight Hemihydrate 3 % by weight Anhydrit~, insoluble 2.2% by weight The above basic mixture was combined with two dif~erent activators:

Al: Total 4.6% by weight, containing 40% of K2CO3 and 60~ of potassium citrate monohydrate A2: Total 3.5% by weight, containing 71~ of K2CO3 and 29% of citxic acid ~ 57 ~ 20 ~S8~9 The chemical and physical properties of the examples in Table 12 are as follows:

Commercial Portland cement (Kleinkems) Blaine 5000 cm~/g Dihydrate 1.5~ by weight Hemihydrate 1.2% by weight This basic mixture was combined with three different activator formulations:
A1: 4.6% by weight,40% K2CO3, 60% potassium citrate monohydrate A2: 4.7~ by weight,43% K2CO3, 57% potassium citrate monohydrate A3: 3.S% by weight,71% K2CO3, 29% citric acid The examples of Table 13 are based on clinker (PKl/4), ground free of gypsum, having a fineness of 5300 cm2/g Blaine, and 6% by weight of dihydrate. As the activating additives, 18.09 mmol % of K2CO3 was utilized, combined with varying amounts of citric acid or citrate (in equivalent molar quantities).
The examples of Table 14 are based on clinker (PKl/4~, ground free of gypsum, having a fineness of 5300 cm2/g according to Blaine and 5% by weight of added dihydrate. As the activating additives, 8.32 mmol-%
of potassium citrate monohydrate was utilized in con-junction with varying amounts of potassium carbonate or potassium bicarbonate.

2~7~
The binder mixtures of Table 15 are based on clinker (PKl/5), ground devoid of gypsum, and 0-6% by weight of gypsum and 6-0~ by weight of hemihydrate.
In each case, the following activating additives were employed:
Al: 4.6~ by weight, 40% K2CO3, 60% potassium citrate monohydrate A2: 3.5% by weight, 71% K2CO3, 29% citric acid It can be seen ~rom the results of Tables 11 to 15 that there exists a marked and significant dif-ference with respect to the influence of the composition of the activating additive on the properties of the binder according to this invention between the clinkers containing Portland cement and clin~ers ground free of gypsum (or hemihydrate-free formulations).
In the presence of potassium carbonate as the carbonate donor, citric acid acts, in formulations containing Portland cement, as an efficient retarding agent, whereas it acts, in formulations free of hemi-hydrate, as an activator with respect to tha settingtimes and the strength development. In contrast there-to, potassium citrate acts in both formulations as an activator. The water re~uirement and the sensitivity with respect to changes in the water/cement ratio is, in citric-acid-containing formulations, clearly and significantly higher than in K3C-containing formula-tions (especially in binder mixtures containing Portland cement).

Binder formulations containing potassium carbonate/citric acid and commercial Portland cement (e.g. as described in US 4,842,649 cited in the beginning) are distinguished, as contrasted to formulations con-taining potassium carbonate/potassium citrate, ingeneral by high sensitivity of the setting times and of the strength development with respect to changes in the water/cement ratio, and by significantly lower strengths.
The delaying action of citric acid, described in US
4,842,649, could only be confirmed in formulations containing Portland cement, rather than in formulations having a low hemihydrate content. Especially when using clinkers ground without gypsum, the citric acid acts like an activator with regard to the setting times as well as the strength development. The xetarding ef-fect of potassium citrate, equated to citric acid in US 4,842,649, could not be confirmed in mixtures con-taining Portland cement or in formulations having a low hemihydrate content (especially, this could not be con-firmed in formulations containing clinkers ground freeof gypsum).

2~7~g~

Binder formulations according to US 4,842,649 containing commercial Portland cement and potassium carbonate/citric acid as the activating additive can lead to surprising results not only with respect to setting times but also with regard to the strength evolution: The citric-acid-containing binder mixture based on PZll/l (Table 11, rows 5 and 6) does harden after 210 and 270 minutes, respectively, but shows no early strengths at all. Yet, after 3 days, a compres-sive strength of 43 MPa was measured. However, thisdoes not involve a so-called "false set" which an expert can very readily distinguish from actually hardened mortars and concretes. The hardened mortar sample did not differ in its appearance from the cor-responding samples containing potassium citrate. How-ever, the latter exhibited compressive strengths of 23-24 MPa. It is clearly apparent that, in practical usage (for example on a building site), such surprising results can have catastrophic consequences (collapse on account of premature formwork removal).
Comparative tests have shown that the puzzolanic additives are essential ~or the binder described in US
4,842,649, for, in general, the strength values in-dicated therein could not be obtained without admixture of the additives described therein (metakaolin, fly ash, fumed silica, etc.) - 61 - ~ V~

Figures 9 and 10 illustrate the effect of gypsum addition on the setting times of ISO mortar mixtures and standard concrete mixtures. A Portland cement clinker (type PKl/5) was combined with 6% by weight of gypsum. The 4.55~ by weight of activating additive contained 40~ K2CO3 and 60~ potassium citrate monohydrate. Figure 9 illustrates the results obtained with the use of a binder according to this invention in an ISO mortar mixture. Figure 10 shows the strength development in standard concrete mixtures.
The results shown in Figures 9 and 10 clearly demonstrate that, by way of the gypsum content, the setting times of the binder of this invention can be regulated between 2 minutes (spray concrete formula-tion) and about 120 minutes (ready-mixed concrete) (almost linear dependence of the setting time on the dihydrate content). As contrasted to conventional high-early-strength binders, however, the strength development is not a~ected thereby. In spite o~
differing dihydrate content (DH), the strength develop-ments take essen~ially the same course.
The ef~ect o~ gypsum on the setting times decreases with increasing content of gypsum. This is advantageous, above all, ~or usages in the ready-mixed concrete area (between 80 and lZ0 minutes).

- 62 - ~7~8~9 Simllar results were obtained with formula-tions containing nat.ural anhydrite. In the presence or anhydrite, however, the setting times react with greater sensitivity to the gypsum content.
Table 16 shows a compilation of preferred embodiments. The following activators were used as the additives:

CaSO4: 5.0 - 5.8% by weight dihydrate, anhydrite, hemihydrate (calculated as the dihydrate) Al: 3.85 - 5.0% by weight, 40-56% K2CO3, 40-60 potassium citrate monohydrate A2: 4.7 - 5.7% by weight, 43-53% KHCO3, 47-57%
potassium citrate monohydrate A3: 2.3% by weight, 87% K2CO3, 13% by weight citric acid Table 17 illustrates the properties of especially pre~erred embodiments of the invention in standard concrete (400 kg/m3, standard aggregate) at various water/cement ratios and, respectively, at varying workability of the fresh concrete. The follow-ing binder formulation was used:
Clinker PKl/5, ground devoid of gypsum 6~ by weight of dihydrate 4.55~ by weight of activator (40~ K2CO3, 60% potassium citrate~

- 63 - ~ 8~

Four especially preferred embodiments of the invention are compiled in Table 12. The binder of this invention was used in standard concrete (400 kg of cement per m3, standard aggregate) at varying water/cement ratios and, respectively, differing work-ability of the fresh concrete. The grading curve of the standard aggregates corresponds to the Fuller c~rve.
The binder utilized has the following formulation:

Clinker PKl/5 ground devoid of gypsum Dihydrate 6% by weight Activator 4.55% by weight, containing 40% K2CO3 and 60% potassium citrate The table shows clearly that, with water/cement values of between 0.32 and 0.37 and good workability (extent of flow 35-63 cm), very high early strengths (4 hours) can be obtained of markedly above 20 MPa.
After 28 days, the strength was between 80 and 90 MPa.
Table 13 shows the influence of adding dipotassium oxalate on the binder properties in ISO
mortar mixtures. All binders are based on the c~inkPr type PKl/5 mixed with 6% by weight of dihydrate.
The results show that K3C
can be extensively replaced by oxalate without any substantial effect on the strength development. The use of oxalate entails, however, a slight increase in - 64 - ~ ~ r~

the water requirement and a prolongation of the setting periods. The reduction in heat of hydration is of advantage.
Figure 11 shows the dependency of the 4-hour strength on the water/cement ratio. Activated Portland cements (PKl/5, 400 kg/m3) are compared with known high-early-strength Portland cements (HPC Untervaz and PC55 Kleinkrems).
It can be seen from Figure 11 that the dependency of the compressive s~rength evolution on the water/cement ratio (W/C) is approximately of the same magnitude as in case of ordinary Portland cements, i.e. those without additives. This is a great advantage.
Figure 12 illustrates that the invention is clearly distinguished over conventional high-early-strength binders with respect to the sensitivity to changes in the water/cement value. The binder 'iPyrament" (according to US 4,842,649) used for com-parison, called T505 in the figure, is markedly more sensitive. With a change of the water/cement ratio by 10% from 0.33 to 0.30, the 4-hour strength changes by a factor of 2. In contrast thereto, a cor-responding change in the water/cemen~ ratio from 0.37 to 0.34 in a binder of this invention leads to a compressive strength increase of merely about 15%.
Similar remarks apply with regard to the 24-hour strength.

- 65 ~

Figure 13 shows the temperature dependency of the early strength evolution in case of ISO mortar mixtures. The temperature in degrees C is plotted on the abscissa, and the compressive strength in MPa is plotted on the ordinate. The binder of this invention (PKl/5, ground free of gypsum ~o Blaine 5300 cm2/g) was compared with a known early-strength cement of the type P50. As can be derived from the figure, the 4-hour ~trength and, in particular, the 6-hour strenyth ob-tained with the binder according to this invention ismarkedly less depsndent on the temperature than the 48-hour strength relevant to P50.
Figure 14 shows the advantageously high flow-ability (FLOW) of a binder according to the lnvention in dependence on the water/cement value (W/C). With a water/cement value of W/C = 0.34, the FLOW of a binder based on the clinker PKl/5 amounts to about 125%. In case of W/C = 0.37, the FLOW is even at about 150~.
In case of the "Pyrament" (T505) mentioned repe~edly above, the FLOW ls barely somewhat more than 110~ (standard) with a water/cement ratio of W/C =
0.33. With a W/C value of 0.30, the FLOW is even below 100%. Therefore, the invention shows a clearly improved behavior over the conventional high-early strength binder.

2~76~69 Finally, it will furthermore be demonstrated that, thanks to the invention, the "hit probability"
in the manufacture of binders is considerably increased and the "variance" is considerably lowered, as compared with the state of the art.
For the statistical evaluation illustrated in Table 13, various clinkers were ground free of gypsum and homogenized with 6% by weight of dihydrate and 3.55~ by weight of activating additives. The additives utilized were K2CO3 and K3C (potassium citrate) in a molar ratio of 1.75. The clinkers were of the type PKl/4 (Blaine 5300 cm2/g) and PKl/5 (Blaine 5600 cm2/g).
Two batches from different clinker production cycles, with customary spectrum of chemical composition and reactivity, were ground in a ball mill with a closed grinding cycle.
The concrete tests took place in two concrete laboratories (BL1 and BL2) under the following conditions:

BLl: Two differen~ aggregates (ZF1, ZF2), grading curve corresponding to the Fuller curve.

Per m3: 756 kg sand (0/5 mm), 1128 kg gravel (5/32 mm), 400 kg cement.

2~7686~
BL2: An aggregate (ZE3), mineralogical composition and grading curve corresponding to the standard of the Federal Measuring and Testing Institute (EMPA).
Per m3: 626 kg sand (0/5 mm), 1330 kg gravel (5/32 mm), 400 kg cement.
Mixing of the concrete took place according to ASTM C192, and testing was carried out on 12 x 12 x 36 cm prisms. The processing temperature was between 17 and 22 C.

~7~9 The following can be derived from the series of tests:
The variations in clinker quality (composition, clinker reactivity), the grinding conditions (atmospher-ic humidity, clinker grinding capacity), mixing condi-tions, type of aggregate, grading curve, and standard workability (extent of flow 46-Sl cm) correspond to the fluctuations customarily encountered under practical conditions.
With the binders according to this inven~ion, the standard deviation is +5.5% (1.1 MPa) and the variance is +6.5~ (1.3 MPa). These values thus range markedly below the values that can be expected with ordinary Portland cements. As per ACI 214, a standard deviation of 3.0 - 4.0 MPa with regard to the 28-hour strengths (21-28 MPa) of ordinary Portland cement is considered to be very good. The hit probabili~y of 99.8% ~or obtaining s~reng~hs above the specified com-pressive strengths(l5 MPa after 4 hours), in particular, constitutes a substantial advantage of the binder ac-cording to this invention over customary Portland ce-ments and, above all, over the known alkali-activated binder systems. The g5% confidence range is even at 19.9 + 2.2 MPa.

2~7S8~
The following can be noted, in summation:

The subject of the invention is a hydraulic binder containing Portland cement clinker, a calcium-sulfate-containing additive, strength-raising additives, and optionally fillers or aggregates as usually found in mixed cements, and making it possible, as compared with previous binders, to obtain increased early and final strengths (> 28 days) in concrete and mortar mixtures.
The invention overcomes, in particular, the following disadvantages of conventional binders:

- uncommon workability in mortar mixtures and concrete mixtures, - high sensitivity of the relevant usage parameters with respect to Ghanges in the binder composition, - sensitivity with respect to the water/cement ratio, - great dependency of the early strength on the working temperature.

The binder of this invention is preferably distinguished by a hemihydrate content of less than 50%, especially less than 20%, calcula~ed as the dihydrate. At least one iron-complexing compound and at least one carbonate donor are preferably used as the strength-increasing additives.

2~7686~
The invention also indicates advantageous processes for the production of Portland cements having a defined maximum hemihydrate content.

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_ _ ~ I _ _ . . _ Clinker PZ cwatso~ w/c Flow Set 6h DF 24h DF
% min MPa _ MPa .,_ . __ __ _._ ~
PK5/2 ¦ 5% DH 1 0.37 115 7011.4 47.4 PK5/2_ ~ 1 5% DH_ 0.39 129 95 9 0 45 ? I
- 1~ ~ 038 lll 45 70 394 PZ5/1 1.3% DH 0.42 132 805.90 34.4 _ . _ 3.7~/0 HH __ ~ __ __ _ clDtker PZ CaS04 Activatol w/c Flow Set 6h DF 24h DF
% min MPa MPa .
PK911 5.5% DH 5.45%0.35 135 135 22.80 50.80 _ _ PK 9/3 7% DH 4.55% 0.35 133 185 18.2 44.40 _ _ 1% DH 4.45%0.38 128 620 0.00 30.40 PZ9/1 4% HH
0.8% A
1.5% DH 4.S5%0.35 129 220 22.40 46.0 PZ912 3.0% HH
1.3% A
PZ9/3 6% DH 4.55%0.38 135 10 24.40 45.50 . - .: _ . . _ PK4/1 7% DH 4.55%0.35 128 80 18.6 36.1 _ _ _ . . _ PK4/1 7% DH 4.55%0.38 163 95 15.2 32.0 _ _ PZ4~ 51 4/oHH 4.55% 0.35 122 225 17.9 34.0 _ PZ4/ 1 51 40/ DH 4.SS% 0.38 148 280 13.4 28.0 __ . . ~ ~ . _ . . _ . . .
PK112 5% DH 3.55% 0.35 124 220 14.7 41.9 _ _ _. , PK112 5% D~ 3.55% 0.38 150 195 12.6 38 . _ _ _ PZl/l 0.1% DH 3.55% 0.35 111 140 13.3 39.2 0.4% HH
1.5% A ___ _ _ _ _ ._ PZIII 0.1% DH 3.55% 0.38 144 155 10.7 29.8 0.4% HH
.5% A _~ _ _ PK10125%DH 4.55%0.35 139 110 19.0 ~4.6 __ _ _ ._ _ PK10125%DH 4.55%0.38 161 155 16.5 42.5 _ _ _ _ ~ . _ PZ10/2 1.6% HH 4.55%0.3S 119 45 22.7 46.8 4% A, inso: _ _ PZ1012 1.6% HH 14 55% 0.38 150 45 19.2 43.7 __ ~ _ __ __ 2~rj~;3~

C~¢s _ Cas04 Activator ~v/c Fiow Set 6h DF 24hDF
% min MPa MPa pKsn 5% DH 4% 0.36 114 10511.50 49.60 _ ~ PZ5/1 3 37o/O DH 4o/o 0.38 115 75 1.40 4.40. . . __ . . __ .
PK4/1 7% DH 4.70% 0.35 119 90 18.6 36.9 _ . _ PK4/1 7% DH 4.70% 0.38 144 12514.9 31.8 _ , . .
PZ4/1 5.6% DH 4.70% 0.35 104 24015.3 30.5 PZ4/1 1 5 6% DH 4.70% 0.38 132 3950.00 20.7 PK112 5% DH 3.70% 0.35 109 17015.4 44.1 PKI/2 5% DH 3.70% 0.38 135 26512.7 40.2 _ , PZI/I 0.1% DH 3.70% 0.35 110 17012.9 38.3 Oj4% HH
PZ 1/ 1 0.1 % DH 3.70% 0.38 i 50 235 9.2 20.9 Oj4% HH
__ .... .. __ . ___ _ ..
PK10/25%DH 4.70% 0.35 121 290 18.6 47.1 __ ~ . _ . __ ~.
PK10/25%DH 4.70% 0.38 142 28S 15.6 43.5 _PZ 10i2 ~ 1.6% HH 4.70~io 0.35 126 120 24.4 50.1 _4% A, mso: _ PZ 10/2 1.6% HH I 4,70% 0.38 158 140 18.8 36.0 _ 4% A, insol . _ ~ - ~ I

2~7~g~

TAsLE 5 CaS04-w/c Flow Set 6h DF 24h DF
Phase % min MPa MPa _ . ~__ .

5% DH 0.37 109 185 12.10 50.60 2.5% DH 0.37 121 145 11.80 49.80 æ5%CaCO3 .
5% A, natØ37 118 95 8.8 42.9 _ _ ~
5% A,solØ37 112 85 "False 43.8 Set"
_ _ ._ ~. , .
5% ~x~HH 0.37 l l l ~ 24h0.00 0.00 _ . ~
5%,B~HH 0.37 i05 ~ 24h0.00 0.00 _ _____ 2 0 ~

K3C w/c Flow Set 4h CStr 6h CStr 24h CStr wt% cement % nun MPa MPa MPa . . . .
0% 0.50 96 240 0 0 27 .9 . _ 1% 0.34 46 85 7.~ 8.4 39.0 2% ~ 0.34 64 20 -12.5 12.6 31.4 _ _ __ _ 2% 0.38 105 30 5.5 9.7 20.9 . __ 3% 0.34 4 .
. _ . ,,, .. .. _ _____ ___ _ _ _ K3C KHC03 w/c Flow Se~ 6h CStr 24h CStr wt% wt% % nun MPa MPa _ ~ . ... __.__. __ 0 0 0.50 96 240 0 27 .9 . _.
1.0 2.0 0.34 1 16 235 0 51.6 I .7 ~ 2.0 0.32 109--~ i70 - ~ 15.4--44.1 -_ _ __ 1.7 2.7 0.32 I 10 185 19.3 52.0 2.7 2.7 0.32 131 - 120 j 22.6 - 49.9 ~
, . . . _ __ _ __ __ 2~7~

. ., . . . .
K3C K2CO3 w/c Flow Set 6h CStr 24h CStr % % i~ nun MPa MPa 0 0 0.50 97 1 85 0 28 . 2 I .70 I .85 0.32 1 24 220 14.7 41 .9 _ 2.70 I .85 0.32 138 135 17. 1 41 .0 - 2.70- 2.15 - 0.32 134 85 16.9 38.7 -~
3.00 2.0 ~ 0.29 1 107 120 21.40 - -48.70 3.00 L~_ 030 L~ 70 122.20--50.9 -K2CO3 w/c I Flow Set j 6h CStr 24h CStr I
% % % m~n MPa MPa _ .. _ . --_ 0.3 2.0 0.36 120 40 5.0 37.6 _ . . _ . ., _ _ _ __ ~ l Clinker Phase ¦ C3s ¦ C~S ~ l I
2.7% K3C, 2% KHC03~hl__~
j 2.7% ~C3-C, 2% KHC03 ~ `
~ _ _ _ _ 2.7%K3C,2%KHC036 10% 0% 1 7j% 95%
~ _ _ _ . , _ 2.0~ C3C 6 10% 1 0% ~0% 1 ~0%
2.7%K3C,2%-KHC03 ~ _ I ~0% 1 ~% 1 9j% 1 95%
_ ~ _ _ _ L

2 ~ r7 ~

TA~LE 1 1 Acti- DH w/c vatorAdded ___ A I 0 0.38 _ Flash Set A 2 _ . 0.38 _Flas 1 Set A I 3% 0.35 12S 65 22.8 _ 23.6 A I 3/O 0.38 159 95 20.2 21.4 A 2 3% 0.35_ 107 2!0 -A2 3% 038 _135 270 00 00 207~

_ _ ~ _ , .
Acti- DH w/c Flow Set 6h DF 24h DF
ator_ Added % _ min MPa MPa_ A 1 0% 34 r 1 16 225 19.6 43.3 A 2 0% 0.34 90 360 3.4 (~ 32.2 A 3 0% 0.34 69 295 8.1 39.1 A I 0O/O 0.37 _ 142 240 I S.5 36.5 A 2 0% 0.37 124 > 540 0.0 _ 22.2 A 3 _0% _ 0.37 _ 107_ 325_ 5.7 (7h) 301 A I 1 % 034 111 360 14.7~hl 37 2 A 2 1% 0.3-4 90 > 465 0.0 _ 26.8 i ¦ A 3_ I% 0.34 69 _ 325 0.0 _ 1% 0.37 137 385 _ 7.1(7h? 28 4 A 2 I ~/~ 0.37 122 _> 480 0.0 17. I
A 3 1% 0 37 105 365 0.0 27 7 _~_ __ . . . . . . ___ . ..
K3C Ci~.Ac. w/c Flow Set 4h DF 6h ~F 24h DF
nunol% nunol% % min Mpa ~ _ Mpa 4.16 . 0~34 tl5 t45_ 12.0 15.t_ 42.3 4.16 0.34 95 _ t30 t4.7 15.0_ 42.8 5.20 - 0.34 t l9 t65 t4.6 16.7 41.1 5 20 0.34 lO0 120 15.7 16 2 41.3 .25_ __ 0.34 _ 130 _170 16.4 17.9_ 41.4_ _ 6.25 0.34 105 115_t7.8 t8.6 42.0 _ 10.62_ 0.34 106 85 20.2 21.2_ 38.0 4.16 037 14~ 220 2.5 12.7 35.0 4 t6 0.37 _ 1~9 14__l2 2 12.7 34 3 5 20 0.37_ t46 215 6 6 t3.9 _ 35.0 5.20 0.37 129 t 3013.6 t 4.4 29.8 6.25 _ _ Oi37 _ l 57 t80 t2.7 _15.2 35.9_ _ ~ 6 25 0.37 l36 125_t3.g _ t5.1 _ 28.2 10.62 0.37 139 80 17.4 l9 0 31 3 8 ~ ~

, . , ~ _ ................... _ K2C03 KHC03 w/c Flow Set 6h DF 24h DF
mmol% mmol% _ % min MPa MPa 15.56 034 134 _ 85 _16.9 38.7_ . 19.98 0.34 _ 123 ~ !25 17.6 42.6 15.56 _ 0.38 > IS0 95 14.3 35.1_ _ 19.98 L~L~ 140 15.1 40.4_ 2 ~

Acti- ; DH/HH w/c Flow Se~ j 4h DF 6h DF
vator Added % m~n MPa MPa __ _ _,_ . . ., , ,_ __ __ A 1 6.9/0.0 0.34 136105 17.7 19.3 A I 6.0/0.0 0.37 162105 14.4 15.2 A 2 60/0.0 0.34 103130 _ 16.2 17.1 A 2 6.0/0.0 _ 0.37 134135 13.1 14.0 A ! 4.5/1.5 0.34 135 85 18.9 20.3 A 1 4.5/1.5 0.3? 160 _85 15.1 16.4 _ A 2 4.5/1.5 0.34 _ 104 120 16.0 16.9 A 2 4.5/1.5 0 37 133125 13.8 14.8 _ _ . _ _ A I 3.0/3.0 0.34 134_ 5 19.7 21.
A I 3 0/3.0 037 16255 16.1 17.1 . _ ~_ A 2 3.0/3.0 0.34 108110 16.4 17.3 A 2 3 0/3 0 037 129120 14.6 15.2 . _ __ _ A I I 1.5/4.5_ 0.34 71 25 18.3 194 L 1.5/4.5 0.37 125 30 1~.9 15.7 A 2_ !-5/45 034 103 ~5 l69 18~3 A 2 1.5!4.5 0.37 125 90 14.6~_ 15.3 A I 0.0/6.0 0.34 57 _ lO 18.4 19.9 i A I 0.0/6.0 037 8l 20 14.6 !~ 3 A 2 0.0/6.0 0.34 69 50 16.0 17.2 A 2 0.0/6.0 0.37 119 70 13 2 14 0 g Clinker PZ CaS04 Type Carb. ~cti- w/c Flow Set 6h 24h ¦ 7d 28d /Don. vator % rnin DF DF DF DF
_ o o/o % _ MPa MPa MPa MPa PKI/I 100 DH A I 2.00 3 00 0.31107 120 21.4 48.779.7 PKI/2 100 DH A I 1.85 2.70 0.35136 140 18.7 42 4 _ 75 3 PK7 100 DH A I 1.85 2 70 0.35143 14Q 19 0 46.0 _ 80.3 PZ9/269 HH A I 2.15 1.70 0.35109 265 18.3 47.773.8 21 DH/A __ _ _ _ PZ9/~69 HH A I 2.00 2.20 0.37142 230 19.1 45.8 86.8 _ 21 DH!A __ __ _ _ PZ9/3100 Dll A I 1.30 2.00 0.36110 !90 23.3 42 0 80 7 94 2 Pzlon2791HH A I 2.00 I.70 0.37123 60 18.6 44.8 84.5 _ . ., . _ _ _ _ _ _ _ .
PKl/2 100 DH A 2 2.00 2.70 0 35 123 125 19 6 46.1 . 84 2 PKI/3 ! DH A 2 2.00 2 70 0.35 104 115 20.4 45.0 65.9 _ PK6 ~ 100 DH A 2 2.00 2.70 0 30 82 50 22 5 50 6 84.0 i PK_ _ 100 DH A 2 2 00 2.70 0.35 146 80 16.8 44 1?7.6 --PK10/2 _ 100 DH A 2 3.00 2.70 0.3S 125 L~ 22 5 52.181.7 _ PZ9 3 100 DH A2 3.00 2.70 0.3S 98 85 29 0 53 589 1 98 0PZ10/2 29 HH A 2 2.00 ¦ 1.70 ~ 0.38 ¦ 148~ 600 0.0 20.3 99.3 . 7! A - ~ --------PKl/l _ 100 DH ~ 3 2 00 0.30 0.37 108 30 ~5.3 42 3 63 182.1 2 ~

. . - ~ . _ ,_ . . . _ -_ w/C D~ul.kty Flow 4h DF 6h DF24h DF 7 Days DF 28 Days DF
kg/lT-3 Extent MPa MPa MPa MPa MPa _ cr4 . _ ~
0.322 2508 35 2~.35_ 30.45 61.i_73.80 90.05 .
0.335 2505 47 24.15 28.75 58.S074.75 _.60 0.348 j 2480 1 57 21.75 25.00 56.85_ 71.0Q 80.80 i 0,363 2483 ~ 2~40 L~ 5630 1~ 1~040 ~ a ~

TAsLE 1 8 _ __ , __ K2C03 KHC03 K2aO4 K-CItr. w/c Flow Set 6h DF 24hDF
j mmol% mmol% mmol% mmol% . _ % min P3_ MPa 14 08.3 0.34 129 1001~.6 41.2_ -- 3 -53 _ 1 034 - 1ll l?5 ~ 419--i 0_83 ~ 034 118 12518.80 420 _ 20 3.0 j 5.3 1 0.34 106 17016.70 :40.1 i 20 _ 5 2 ~ L~ . I l 1~ 145 ~7.0 42 8 2~76f~

TABLE l 9 _ . , l Lab Clinker Additive w/c of Flow 4h DF
. i - ~cm1 j ~MPa1 i BL1 _ jPK1/4 F1 0.363_ 47 1 18.2 _ i BLl IPKI/4 _ ZF2 0.365 46 _ 18.6 _ l BLI IPKI/5 ZF1 0.363~ 47 _ 21.2 i BLI PKI/5 _ZF I 0 363 50 21.1 _ BL2 _ PK1/4 ZE3 0.350_ 49 19.3 _ BL2 j PK1/5 ZE3 _ 0.340 50 _ 19.8 l BL2 1 PK1/5 ZE3_ 0.338 - 4? 20.9 i _ ZE3 __ 0.350 49 19 3 l I AVER~GE VALUE 035 49 19.9 _ i : STANDARD DEVIAT ION + 0.012 + 2 ~ 1~1 ___ VARIANCE _ ~ ~ l _~ 1 17.7-~2.1 i ~ _ ~ L~ i

Claims (30)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. Process for producing a calcium-sulfate-containing hydraulic binder for use in a mortar or concrete mixture, the properties of which, such as workability, setting time, early and/or long-term strength are to be regulated by additives, characterized by the use of a Portland cement having a specific maximum calcium sulfate hemihydrate content.

2. Process for producing a calcium-sulfate-containing hydraulic binder for use in a mortar or concrete mixture, the properties of which, such as workability, setting time, early and/or long-term strength are to be regulated by additives, characterized by the use of a Portland cement clinker ground without gypsum, and by a subsequent admixture of gypsum and/or anhydrite.

3. Process according to claim 1 or 2, characterized in that at least one activating, strength-increasing additive is admixed at tempera-tures of less than 120° C, preferably less than 70°C.

4. Process according to claim 1 or 3, characterized by admixing to the binder, for lowering the hemihydrate content, gypsum and/or anhydrite.

5. Process for producing a Portland cement for use in a process according to claim 1 wherein Portland cement clinker is ground together with a given amount of dihydrate, characterized in that the process temperature and/or the humidity during the grinding step is or, respectively, are set so that the calcium sulfate hemihydrate content of the thus-produced Portland cement does not exceed a predeter-mined maximum value.

6. Process for producing a Portland cement for use in a process according to claim 1, char-acterized in that Portland cement clinker is ground together with a given quantitative ratio of dihydrate and anhydrite so that the calcium sulfate hemihydrate content of the thus-produced Portland cement does not exceed a predetermined maximum value.

7. Hydraulic binder for producing concrete with a high early and long-term strength, based on a ground Portland cement clinker with calcium sulfate phases and additives for regulating workability, setting time, early and/or long-term strength, characterized by a defined maximum calcium sulfate hemihydrate content of less than 50% by weight, calculated as the dihydrate.

8. Binder according to claim 7, characterized in that the calcium sulfate hemihydrate content, calculated based on the dihydrate, amounts to less than 20% by weight.

9. Binder according to claim 7 or 8, characterized by a calcium-sulfate-containing additive for prolonging the setting time.

10. Binder according to claim 9, characterized in that the calcium-sulfate-containing additive contains gypsum, anhydrite, or a mixture of both.

11. Binder according to claim 9 or 10, characterized in that the amount of the calcium-sulfate-containing additive is dimensioned so that the calcium sulfate content of the binder, calculated as CaSO4, ranges between 0.7% by weight and 8% by weight.

12. Binder according to one of claims 6-11, characterized in that the additives for increasing the strength contain at least one carbonate donor, partic-ularly water-soluble salts of carbonic acid, and at least one iron-complexing compound, especially a water-soluble salt of polyoxycarboxylic acid or of polycarboxylic acid, or a diketone.

13. Binder according to claims 8 and 10, characterized in that the additives comprise potassium bicarbonate as the carbonate donor.

14. Binder according to one of claims 7-13, characterized in that the Portland cement clinker contains a proportion of more than 10% by weight of C3A, and that the calcium sulfate hemihydrate content, calculated based on the dihydrate, amounts to less than 10% by weight.

15. Binder according to one of claims 7-13, characterized in that the Portland cement clinker contains a proportion of more than 8% by weight of C3A and a proportion of more than 0.9% by weight of K20, and that the calcium sulfate hemihydrate content amounts to less than 5% by weight.

16. Binder according to one of claims 7-13, characterized in that the Portland cement clinker contains a proportion of more than 9% by weight of C3A and a proportion of more than 1.0% by weight of K20, and that the calcium sulfate hemihydrate content amounts to less than 1% by weight.

17. Mortar or fresh concrete, characterized by a hydraulic binder according to claim 7 and by a water/cement value in the range of 0.25 - 0.4, especially 0.30 - 0.37.

18. Binder according to one of claims 7-17, characterized in that the additives contain a propor-tion, based on the clinker, of at least 3 mmol-% of at least one iron-complexing compound, and at least one carbonate donor in a molar ratio, based on the iron-complexing compound, of between 0.3 and 4.

19. Binder according to one of claims 7-18, characterized by a molar ratio of sulfate to the iron-complexing compound of more than 1 and less than 20.

20. Binder according to one of claims 7-19, characterized by a molar ratio of sulfate to the iron-complexing compound of at least 3 and at most 8.

21. Binder according to one of claims 18-20, characterized in that the carbonate donor is present in a molar ratio, based on the iron-complexing compound, of more than 1 and preferably less than 3.

22. Binder according to one of claims 7-21, characterized in that the Portland cement clinker is present in a grinding fineness according to Blaine of at least 4000 cm2/g, preferably of between 4500 cm2/g and 5500 cm2/g.

23. Binder according to one of claims 7-23, characterized in that the additives contain, as the carbonate donor, salts of carbonic acid that are soluble in water as well as sparingly soluble to insoluble, especially calcium carbonate, magnesium carbonate and/or dolomite wherein the salts have been activated by grinding and/or thermal treatment, and that the amount of the salts showing sparing solubility or being insoluble in water ranges between 2% by weight and 20% by weight.

24. Binder according to one of claims 7-23, characterized in that the additives contain, as the carbonate donor, at least one water-soluble salt of carbonic acid, especially alkali carbonates and/or alkali hydrogen carbonates, and,as the iron-complexing compound, at least one water-soluble salt of polyoxy-carboxylic acid or of polycarboxylic acid, or a diketone.

25. Binder according to one of claims 7-24, characterized in that the additives contain, as the carbonate donor, potassium carbonate, potassium carbonate trihydrate or potassium bicarbonate, and, as the iron-complexing compound, tripotassium citrate monohydrate or a mixture of dipotassium oxalate mono-hydrate and tripotassium citrate monohydrate,wherein the proportion of dipotassium oxalate monohydrate amounts to less than 50 mol-%.

26. Binder according to one of claims 7-25, characterized in that the additives contain a propor-tion, based on the clinker, of at least 4.5 mmol-%, preferably at least 7.5 mmol-%, of potassium citrate monohydrate.

27. Binder according to one of claims 7-24, characterized in that the additives contain a propor-tion, based on the clinker, of at least 11 mmol-% of citric acid.

28. Binder according to one of claims 7-27, characterized in that the additives, for obtaining a high early strength, contain a proportion, based on the clinker, of at least 5 mmol-% and at most 25 mmol-%
of carbonate.

29. Binder according to one of claims 7-28, characterized in that the additives, for obtaining a high long-term strength, contain a proportion, based on the clinker, of at least 9 mmol-% and at most 30 mmol-%
of bicarbonate.

30. Binder according to one of claims 7-29, characterized in that the additives also comprise puzzolan earths, clay minerals, fly ashes and/or extremely finely divided reactive silica.