WO2017116312A1

WO2017116312A1 - Cement composition with layered double hydroxide

Info

Publication number: WO2017116312A1
Application number: PCT/TH2015/000097
Authority: WO
Inventors: Dermot O'hare; Sakprayut SINTHUPINYO; Thanakrit CHATRA; Anchalee WONGARIYAKAWEE; Benjaluk NA LAMPANG; U-bonwan KHOPONGPAIBOON
Original assignee: Scg Cement Co., Ltd.
Priority date: 2015-12-28
Filing date: 2015-12-28
Publication date: 2017-07-06

Abstract

There is provided a cement composition, comprising: a portland cement (comprising a clinker; limestone; and gypsum); a layered double hydroxide; and, optionally, an additional amount of powdered limestone and/or gypsum, where the portland cement composition and the additional amount of powdered limestone and/or gypsum, when present, are taken as 100 wt%, wherein the total amount of limestone in the composition is from 3.0 to 20.0 wt%; total amount of gypsum in the composition is from 4.0 to 8.0 wt%; and amount of the layered double hydroxide in the composition is from 0.35 to 6.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

Description

CEMENT COMPOSITION WITH LAYERED DOUBLE HYDROXIDE Technical Field

The current invention relates to a cement formulation that can increase the compressive strength of cement, mortar or concrete that utilizes said cement formulation.

Background Art

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

Important properties of cement and/or concrete include the setting time and its early strength. The early strength of cement and/or concrete refers to the strength of the cement and/or concrete up to 24 hours after placement.

High early strength concrete can replace general purpose concrete in all applications but is commonly specified where higher than normal early strengths are required. Examples of areas where high early strength concrete may be used are concrete product applications (roof tiles and masonry blocks), precast and tiltup concrete, pavement repair, cold-weather construction and where early stripping of formwork is desired, amongst other things.

Chinese patent application publication No. 101244918 discloses a using method for adopting calcium aluminum hydrotalcite as an early strength agent for cement concrete. Chinese patent application publication No. 102249280 discloses a calcium-aluminum hydrotalcite concrete admixture with sodium polyacrylate adsorbed on the surface of hydrotalcite, and a preparation method of the concrete admixture, where the concrete admixture can be used to improve the compression strength of concrete.

Layered double hydroxides (LDHs) are a class of layered materials with positively charged layers and weakly bound, often exchangeable, charge-balancing anions located in the interlayer region. Naturally occurring examples of LDH are classified as members of the hydrotalcite supergroup. A LDH can be described as having a brucite-like layered structure, where some of the divalent cation sites in the brucite structure are substituted by trivalent or tetravalent cations. This creates positively-charged metal hydroxide layers in the structure and this positive charge is balanced by the intercalation of anions in the interlayer region to retain an overall electroneutrality. A general formula (1) for LDH materials may be written as [M_p ^z+MV⁺(OH)₂]^a+(Xⁿ .bH₂0 (I) wherein M^z+ and M'^y+ are metal cations or mixtures of metal cations, z = 1 or 2; y = 3 or 4; p + q = 1 ; b = 0 to 10, X^11" is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a = zp+yq-2.

The production of cement is an energy-intensive process, which results in significant carbon dioxide emissions (typically 0.8 kg of C0₂ per kg of cement produced). Given this, the addition of supplementary cementing materials (SCMs), such as limestone, to ordinary cement may help to reduce the cost and also retain many of the properties of the cement. The addition of limestone to cement has been practiced for a significant period of time. However, while the addition of limestone to the cement matrix can reduce the quantity of clinker in the cement (thereby reducing cost and carbon dioxide emissions) it is known that the addition of limestone reduces the early compressive strength and the final strength of the resulting cement and/or concrete.

There remains a need for improved compositions of cement and/or concrete that are more environmentally friendly and have high early strength.

Summary of Invention

Surprisingly, it has been found that a combination of cement, an LDH and an increased limestone content in the composition results in the improvement of early strength, resulting in a composition that is more environmentally friendly due to the reduction of clinker in the cement. These results are surprising and contrary to normal expectations, as limestone is known to reduce the early strength of cement and/or concrete.

In a first aspect of the invention, there is provided a cement composition, comprising:

a portland cement comprising:

a clinker; limestone; and

gypsum;

a layered double hydroxide; and,

optionally, an additional amount of powdered limestone and/or gypsum, where the portland cement composition and the additional amount of powdered limestone and/or gypsum, when present, are taken as 100 wt%, wherein the:

total amount of limestone in the composition is from 3.0 to 20.0 wt%; total amount of gypsum in the composition is from 4.0 to 8.0 wt%; and amount of the layered double hydroxide in the composition is from 0.35 to 6.0 wt%,

relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

In embodiments of the invention, the additional amount of powdered limestone, when present, may have a particle size of less than 75 μτη (e.g. a particle size of from 10 μιη to 70 μηι).

In further embodiments of the invention, the total amount of limestone in the composition may be from 3.5 to 15.0 wt% (e.g. from 4.0 to 10.0 wt%, such as from 4.5 to 10.0 wt%), relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum. For example, the total amount of limestone in the composition may be from 7.0 to 8.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

In yet further embodiments of the invention, the layered double hydroxide may be present in an amount of from 0.75 to 4.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum. For example, the layered double hydroxide may be present in an amount of from 1.0 to 2.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

In still further embodiments, the layered double hydroxide has the general formula (I)

wherein M^z+ and M' ⁺ are metal cations or mixtures of metal cations, z = 1 or 2; y = 3 or 4; p + q = l ; b = 0 to 10, X^n~ is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a = zp+yq-2.

In certain embodiments, M may be Mn, or more particularly, Li, Mg, Zn, Fe, Ni, Co, Cu, Ca, or a mixture of two or more thereof. In yet further embodiments, y may be 3 and JVT is Ni, or more particularly, Cr, Mn, Co, V, Sc or, more particularly, Al, Ga, Fe or a mixture of two or more thereof (e.g. y may be 3 and M' may be Al). In certain embodiments, the layered double hydroxide M/M' may be selected from Zn Al, Ni/Al, Mg/Al, and/or Ca Al. For example, the layered double hydroxide may be a Ca/Al layered double hydroxide.

In yet further embodiments, X^11" may be an anion selected from halide, inorganic oxyanion, anionic surfactants, anionic chromophores, and/or anionic UV absorbers. For example, X^n" may be an inorganic oxyanion selected from one or more of (e.g. two or three) the group consisting of carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, sulfate, sulphite and phosphate (e.g. the inorganic oxyanion may be nitrate or sulfate).

In yet further embodiments, the layered double hydroxide may be in a particulate form and the particles may have a size of not greater than 2000 nm, preferably not greater than 300 nm, most preferably not greater than 100 nm.

In still further embodiments, the layered double hydroxide is [Ca₂Al(OH)₆](N0₃) bH₂0 or [Ca₂Al(OH)₆](S0₄)o_.5-bH₂0, where b = 0-10, such as from 4 to 7, such as 6.

In yet still further embodiments, the composition may further comprise a fine and/or a coarse aggregate.

In a yet further embodiment of the invention, the layered double hydroxide may be a slurry, provided that the amount of layered double hydroxide added to the composition is calulated based upon the dry weight of layered double hydroxide used. For example, the slurry of the layered double hydroxide may be a slurry in water, wherein the slurry comprises a solid weight content of from 20 to 80 wt% (e.g. from 30 to 50 wt%, such as from 40 to 45 wt%, such as 44 wt%).

In particular embodiments of the invention that may be mentioned herein, the layered double hydroxide may have a particle size of from 50 to 350 nm in diameter (e.g. from 100 to 325 nm, such as from 200 to 300 nm in diameter as measured using transmission electron microscopy.

It will be appreciated that the embodiments of the first aspect of the invention may be combined in any suitable manner. In a second aspect of the invention, there is provided a method of making a cement or concrete using the cement composition of the first aspect of the invention and its embodiments.

In a third aspect of the invention, there is a method of making a cement or concrete using the cement composition of the first aspect of the invention and its embodiments.

Brief Description of Drawing

Figures 1, 3, 5, 7 and 9 provide the measured compressive strengths in ksc (kilogram- force per square centimetre) of the examples and comparative formulations (blanks 1-3).

Figures 2, 4, 6, 8 and 10 provide the strength index (in percent) of the various formulations relative the compressive strength of a comparative example.

Figure 11 depicts a composition of the current invention, wherein the layered double hydroxide is shown to have a size of from about 200 to about 300 nm.

Disclosure of Invention

As mentioned hereinbefore, there is provided a cement composition, comprising:

a portland cement comprising:

a clinker;

limestone; and

gypsum;

a layered double hydroxide; and,

optionally, an additional amount of powdered limestone and/or gypsum, where the portland cement composition and the additional amount of powdered limestone and/or gypsum, when present, are taken as 100 wt%, wherein the: total amount of limestone in the composition is from 3.5 to 20.0 wt%; total amount of gypsum in the composition is from 4.0 to 8.0 wt%; and amount of the layered double hydroxide in the composition is from 0.35 to 6.0 wt%,

When used herein, the term "comprising" is intended to require all components mentioned to be present, but to allow further components to be added. It will be appreciated that the term "comprising" also covers the terms "consisting of and "consisting essentially of as subsets, which are limited to only the components mentioned or to only the component mentioned along with some impurities, respectively. For the avoidance of doubt, it is explicitly contemplated that every use of the word "comprising" may be replaced with "consisting of and "consisting essentially of and variants thereof.

The term "portland cement", when used herein refers to a composition that comprises:

from 92.5 to 95.5 wt% of a clinker;

from 2.0 to 4.0 wt% of limestone; and

from 5.4 to 6.7 wt% of gypsum.

Thus, it will be appreciated that, when the total amount of limestone is over 4.0 wt% or the the total amount of gypsum is over 6.7 wt%, then the composition contains an additional amount of limestone or gypsum, respectively. When used herein, the term "clinker" takes it normal meaning in the art. That is, "clinker" refers to a product obtained from a cement kiln as a result of burning various raw materials at high temperature. Normally, the clinker produced is a grey ball with a size of approximately 1 inch (2.5 cm) or smaller. It is normally ground with other materials (i.e. limestone and gypsum) to produce cement. It will be appreciated that the composition of "clinker" is not clearly defined and international standards such as ASTM CI 50 only limit the maximum quantity of some elements in the entire cement composition (not the clinker itself, but components that almost entirely come from the clinker) such as C₃A and MgO. As such, it will be appreciated that the term "clinker" may relate to a number of different possible components and impurities. In embodiments of the invention that may be mentioned herein, the clinker may be a Portland cement clinker, wherein the main chemical constituents are tricalcium silicate (C₃S), dicalcium silicate (C₂S), tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF). Some other minor elements such as Sulfur trioxide (S0₃), Magnesium Oxide (MgO), Sodium Oxide (N₂0) or Potassium Oxide (K₂0) may also be present. Maximum and minimum amounts of the above components are suggested in Table A below.

As before, it will be appreciated that additional minor components may be present in Portland cement clinker.

When used herein, the term "gypsum" may refer to the naturally occurring mineral CaS0₄.2H₂0,

i

or to the anhydrite (CaS0₄) or hemihydrate (CaS0₄. - H₂0) forms of gypsum.

The term "layered double hydroxide", when used herein refers to a naturally occurring or synthetic composition that has a brucite-like layered structure, where some of the divalent cation sites in the brucite structure are substituted by trivalent or tetravalent cations to create positively- charged layers within the structure, balanced by the intercalation of anions in the interlayer region to retain overall electroneutrality.

For example, the layered double hydroxide may have the general formula (I) [M_p ^z+MV⁺(OH)₂]^a+(Xⁿ-)_a;_n ^«bH₂0 (I) wherein M^z+ and M'^y+ are metal cations or mixtures of metal cations, z = 1 or 2; y = 3 or 4; p + q = 1 ; b = 0 to l 0, X^n~ is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a = zp+yq-2.

M may be selected from one or more of the group consisting of Mn, Li, Mg, Zn, Fe, Ni, Co, Cu, and Ca. In particular embodiments, M may be selected from one or more of the group consisting of Li, Mg, Zn, Fe, Ni, Co, Cu, and Ca. For example, in particular embodiments, when z is 1, M may be Li. Alternatively, when z is 2, M may be selected from one or more of Mn, Mg, Zn, Fe, Ni, Co, Cu, and Ca (e.g. M may be Ca).

In certain embodiments, y may be 3 and M' may be selected from one or more of the group selected from Ni or, more particularly, Cr, Mn, Co, V, Sc, Al, Ga, and Fe. Particular values of M' in this embodiment may be one or more of the group consisting of Al, Ga and Fe. For example, M' may be Al.

The anion X may be an anion preferably selected from halide (for example, chloride), inorganic oxyanion, anionic surfactants, anionic chromophores, an/or anionic UV absorbers. Examples of inorganic oxyanions include carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, sulphate and phosphate. In embodiments of the invention that may be mentioned herein, the anion X may be nitrate or sulfate (e.g. nitrate).

In certain embodiments, then layered double hydroxide M/M' may be selected from one of more of the group of combinations consisting of Zn/Al, Ni/Al, Mg/Al, and Ca/Al. In particular embodiments of the invention that may be mentioned herein, the layered double hydroxide may be a Ca/Al layered double hydroxide. For example, the layered double hydroxide may be a Ca- A1-S0₄ LDH (e.g. [Ca₂Al(OH)₆](SO₄)₀.5-bH₂O or, more particularly, a Ca-Al-N0₃ LDH (e.g. [Ca₂Al(OH)₆](N0₃) bH₂0). When used be examples herein, "b" may be a number from 0 to 10, such as from 4 to 7, such as 6.

The layered double hydroxide may be present in an amount of from 0.75 to 4.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum. For example, the layered double hydroxide is present in an amount of from 1.0 to 2.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum. The layered double hydroxide may be in a particulate form and the particles may have a size of not greater than 2000 nm, preferably not greater than 300 nm, most preferably not greater than 100 nm. In particular embodiments of the invention that may be mentioned herein, the layered double hydroxide may have a particle size of from 50 to 350 nm in diameter (e.g. from 100 to 325 nm, such as from 200 to 300 nm in diameter as measured using transmission electron microscopy.

In certain embodiments of the invention, the additional amount of powdered limestone may have a particle size of less than 75 μηι, such as from 10 μηι to 70 μιη. The total amount of limestone in the composition may be from 3.5 to 15.0 wt% (e.g. from 4.0 to 10.0 wt%, such as from 4.5 to 10.0 wt%), relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum. In particular embodiments of the invention that may be mentioned herein, the total amount of limestone in the composition is from 7.0 to 8.0 wt% (e.g. 7.5 wt%), relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

A cement composition according to the current invention may be made in a number of ways. In general, the bulk materials (e.g. clinker, limestone and gypsum) may be dry-ground together (intergrinding) or separately using a vertical cement mill or tube mill. When the bulk materials are ground separately, the resulting ground materials are mixed together. The additive materials (e.g. the layered double hydroxide) may be added to one or more of the bulk materials before grinding or separately after grinding and/or mixing of the materials has finished. This is because the amount of each additive is generally less than 1 wt%, so separate processing is not practical. For the LDHs mentioned herein, the LDHs may be in the form of a dry powder or in solution, with the addition preferably being after the cement is ground and mixed or just before formation of the cement itself, respectively. It will be appreciated that the cement composition described hereinbefore may be used to prepare concrete. As such, the cement composition may further comprise a fine and/or a coarse aggregate. When used herein "a fine aggregate" and "a coarse aggregate" are each intended to cover one or more (e.g. 1 , 2, 3) aggregates. In addition, the invention relates to a method of making a cement or concrete using the cement composition disclosed herein.

EXAMPLES

Example 1

Preparation of formulations

Table 1 lists formulations according to the current invention, as well as some comparative examples that do not contain any LDH.

Formulati % Composition (by weight)

on Clinke Limeston Gypsum LDH LDH LDH

r e (Slurry of (Powder- (Powder-

[Ca₂Al(OH)₆ [Ca₂Al(OH)₆ [Ca₂Al(OH)₆

] ] ]

(Ν0₃)·6Η₂0 (S0₄)o.5-6H₂ (Ν0₃)·6Η₂0

LDH) O LDH)* LDH)*

Blank 1 91.0% 3.0% 6.0% - - -

1 91.0% 3.0% 6.0% 0.36% - -

2 91.0% 3.0% 6.0% 2.00% - -

3 91.0% 3.0% 6.0% - 1.00% -

4 91.0% 3.0% 6.0% - 2.00% -

5 91.0% 3.0% 6.0% - 2.00%

6 89.5% 3.0% 7.5% - 2.00%

Blank 2 86.7% 7.5% 5.8% - - -

7 86.7% 7.5% 5.8% - 1.00% -

8 86.7% 7.5% 5.8% - 2.00% -

Blank 3 87.1% 7.5% 5.4% - - -

9 87.1% 7.5% 5.4% - - 2.00%

10 86.5% 7.5% 6.0% - - 2.00%

Amount of LDH shown above based upon 100% by weight of raw material

(clinker+limestone+gypsum)

The bulk materials are prepared as discussed hereinbefore by grinding and mixing. The powder LDHs are dry mixed into the cement composition, this can be done before or after grinding. The LDH slurry was added at the time of mixing the cement with water. The LDH slurry is preferably formed using water and has a 44 wt% solid content. As noted above, the %wt provided in the table above for the LDH in slurry is based upon the dry weight of the LDH added.

Example 2

Testing of Samples 1. 500 grams of a cement from Example 1 is mixed with approximately 240 grams of water (quantity of water may change according to the flow measured in step 5) and mixed at approximately 150 rpm for 30 seconds.

2. 1,375 grams of Ottawa sand (a standard sand used for cement testing) is slowly added to the mixture, with mixing, over the next 30 seconds.

3. The mixing speed is then increased to 285 rpm for 30 seconds, then the mixer is stopped and the sample is left standing until a total time of three minutes from step 1 has passed (i.e. the mixture is left standing for 90 seconds).

4. The resulting mixture is then mixed again at 285 rpm for 60 seconds.

5. The flow of the resulting mixture/cement paste is measured using a Flow Table by raising and dropping the table 25 times and the and the diameter of the mass is measured and compared to the initial size and expressed as a percentage of the initial size. The required controlled flow value for each cement paste is 1 10% ±5%. If the recorded flow value is more or less than 110% ±5%, then step 1 is repeated using more or less water as required (and may be repeated iteratively) until the control flow value is obtained.

6. Once the proper flow is achieved, the cement paste is placed and compacted into a cube- shaped mold having a size of 5x5x5 cm. The top surface of each cube is finished using a trowel, and the molds are placed into a moisture controlled curing cabinet. After 8 hours of curing, the molds are stripped from the cube specimens. The compressive strength is then tested at specified curing intervals of 8 hours, 1 day, 3 days, 7 days and 28 days.

ASTM CI 09 is used for the mortar strength measurement. The steps used to prepare the cement for said test are set out below.

Results

Figures 1, 3, 5, 7 and 9 provide the measured compressive strengths in ksc (kilogram-force per square centimetre) of the examples and comparative formulations (blanks 1-3). Figures 2, 4, 6, 8 and 10 (derived from the values in Figures 1 , 3, 5, 7 and 9, respectively) provide the strength index of the various formulations relative the compressive strength of the comparative example. For example, Figure 2 is derived from Figure 1 by dividing the compressive strength values for each sample by the compressive strength value of the comparative example (blank 1) and multiplying the resulting figure by 100.

As can be seen, all of the formulations provide an improved early compressive strength at 8 hours (0.33 days) compared to the comparative examples (blanks). In particular, Formulations 2 and 9 show an increase of 69% and 1 14% of the compressive strength, respectively, in comparison to their respective comparative examples.

As shown in Formulations 1 and 2, even the addition of a small amount of LDH in solution (0.36 wt% of [Ca₂Al(OH)6](N0₃) bH₂0 in Formulation 1] can lead to a significant improvement in the early compressive strength of the resulting cement. Further, the addition of 2.00 wt% of the solution-based LDH shows an even higher early compressive strength at 8 hours, while also maintaining an equivalent strength to a cement formulation that is not treated with LDH at 28 days. As shown in Figures 5 and 6, when 2.00 wt% of a powdered form of [Ca₂Al(OH)6](N0₃) bH₂0 is used in Formulation 5, there is a considerable drop in the 1 day compressive strength recorded when directly compared to the equivalent solution LDH form used in Formulation 2 (as shown in Figures 1 and 2). Surprisingly, this can be remedied by the introduction of additional gypsum to the cement composition, as shown in Formulation 6. It is noted that Formulations 7 to 10 show significantly improved compressive strengths compared to the comparative examples, even though these formulations contain a significant amount of limestone, which is expected to reduce the compressive strength of the cement. In addition, it is noted that the compressive strength of the formulations is the same as, or not significantly worse than, the comparative examples even at 28 days, which would also not be expected given the increased amount of limestone present in these formulations.

Example 3

A composition containing [Ca₂Al(OH)6](N0₃) bH₂0 was subjected to transmission electron microscopy (TEM) to obtain an approximate size of the LDH. As shown in Figure 1 1, the examined LDH (the smaller hexagonal particles) had a particle diameter of approximately 200 to 300 nm in size.

Claims

1. A cement composition, comprising:

a portland cement comprising:

a clinker;

limestone; and

gypsum;

a layered double hydroxide; and,

2. The cement composition according to Claim 1, wherein, when present, the additional amount of powdered limestone has a particle size of less than 75 μη .

3. The cement composition according to Claim 2, wherein the additional amount of powdered limestone has a particle size of from 10 μιη to 70 μηι.

4. The cement composition according to any one of the preceding claims, wherein total amount of limestone in the composition is from 3.5 to 15.0 wt% (e.g. from 4.0 to 10.0 wt%, such as from 4.5 to 10.0 wt%), relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

5. The cement composition according to Claim 4, wherein total amount of limestone in the composition is from 7.0 to 8.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

6. The cement composition according to any one of the preceding claims, wherein the layered double hydroxide is present in an amount of from 0.75 to 4.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

7. The cement composition according to Claim 6, wherein the layered double hydroxide is present in an amount of from 1.0 to 2.0 wt%, relative to the 100 wt% of the portland cement composition and, when present, the additional amount of powdered limestone and/or gypsum.

8. The cement composition according to any one of the preceding claims, wherein the layered double hydroxide has the general formula (I)

[M_p ^z+ M'_q ^y+ (OH)₂]^a+(Xⁿ-)_a/n.bH₂0 (I) wherein M^z+ and M'^y+ are metal cations or mixtures of metal cations, z = 1 or 2; y = 3 or 4; p + q = 1 ; b = 0 to l0, X^n~ is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a = zp+yq-2.

9. The cement composition according to Claim 8, wherein M is Mn, Li, Mg, Zn, Fe, Ni, Co, Cu, Ca, or a mixture of two or more thereof.

10. The cement composition according to Claim 8 or Claim 9, wherein y is 3 and M' is Ni, Cr, Mn, Co, V, Sc or, more particularly, Al, Ga, Fe or a mixture of two or more thereof.

1 1. The cement composition according to any one of Claims 8 to 10, wherein M' is Al.

12. The cement composition according to any one of Claims 8 to 1 1, wherein in the layered double hydroxide M/M' is selected from Zn/Al, Ni/Al, Mg/Al, and/or Ca/Al.

13. The cement composition according to Claim 12, wherein the layered double hydroxide is a Ca/Al layered double hydroxide.

14. The cement composition according to any one of Claims 8 to 13, wherein X^n~ is an anion selected from halide, inorganic oxyanion, anionic surfactants, anionic chromophores, and/or anionic UV absorbers.

15. The cement composition according to Claim 14, wherein the inorganic oxyanion is carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, sulfate, sulphite or phosphate or a mixture of two or more thereof.

16. The cement composition according to Claim 14, wherein the inorganic oxyanion is nitrate or sulfate.

17. The cement composition according to any one of Claims 8 to 16, wherein the layered double hydroxide is in a particulate form and the particles have a size of not greater than 2000 nm, preferably not greater than 300 nm, most preferably not greater than 100 nm.

18. The cement composition according to any one of Claims 8 to 16, wherein the layered double hydroxide component is [Ca₂Al(OH)₆](N0₃) bH₂0 or [Ca₂Al(OH)₆](SO₄)_{0 5} bH₂O.

19. The cement composition of any one of the preceding claims, wherein the composition further comprises a fine and/or a coarse aggregate.

20. The cement composition of any one of the preceding claims, wherein the layered double hydroxide is a slurry, provided that the amount of layered double hydroxide added to the composition is calulated based upon the dry weight of layered double hydroxide used.

21. The cement composition of Claim 20, wherein the slurry of the layered double hydroxide is a slurry in water, wherein the slurry comprises a solid weight content of from 20 to 80 wt% (e.g. from 30 to 50 wt%, such as from 40 to 45 wt%, such as 44 wt%).

22. The cement composition of any one of the preceding claims, wherein the layered double hydroxide has a diameter of from 10 to 350 nm (e.g. from 200 to 300 nm).

23. Use of the composition of any one of Claims 1 to 22 to make concrete with high early strength.

23. A method of making a cement or concrete using the cement composition of any one of Claims 1 to 22.