AU774303B2 - Compositions and methods for curing concrete - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: MBT Holding AG Actual Inventors: Roland Tak Yong Liang and Robert Keith Sun Address for Service: BALDWIN SHELSTON WATERS 60 MARGARET STREET *SYDNEY NSW 2000 Invention Title: 'COMPOSITIONS AND METHODS FOR CURING CONCRETE' The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 28020AUP00 -2- TECHNICAL FIELD The present invention is concerned with self-curing concrete and in particular with internal curing compositions and methods of using said compositions for curing concrete.

BACKGROUND ART Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Curing compositions are well known in the concrete art. They are materials which are applied to the surface of wet concrete to reduce or eliminate the loss of water from the concrete and therefore result in a better concrete which has lower permeability and therefore better strength and durability. These are typically emulsions of paraffins or microwaxes which are sprayed on to the surface. While these serve the purpose well, it is not always desirable to leave them on the surface to wear away by exposure to the elements, and removal can be costly and time-consuming.

It has been suggested that concrete can be cured by an "internal" curing admixture, that is, by the addition to and mixing into a concrete mix of an admixture which provides 0 curing. While such compositions have been used in specialised applications such as 0. .shotcrete application, to date no such composition has been found to be able to meet the standards required in general concrete applications, for example, (Australian Standard 0AS 3799).

The object of the present invention is to ameliorate at least one of the oeeoe disadvantages of the prior art or to provide a useful alternative.

0 -3- SUMMARY OF THE INVENTION The present invention is based on the observation that a combination of a wax and a glycol, when added to concrete, enables internal curing of concrete which in many respects is equal to or superior to traditional forms of curing concrete, as assessed by a number of relevant parameters. The present invention provides for the first time an internal curing composition which, when added to concrete or other cementitious mixes, meets the required standards of curing (Australian Standard AS 3799).

According to a first aspect there is provided a composition including a glycol and a wax, wherein said composition internally cures concrete.

Glycols suitable for use in the present invention are for example polyethylene glycol (PEG) or methoxypolyethylene glycol (MPEG), or mixtures thereof. The preferred glycol is polyethylene glycol. A PEG of molecular weight in the range of from about 200 to about 10,000 may be suitably employed. The preferred molecular weight of PEG is 200. In the case of MPEG a suitable molecular weight range can be selected from about 350 to about 5,000.

Waxes which are suitable for use in the present invention are for example paraffin Swax, microcrystalline wax or a blend of paraffin and microcrystalline wax. The most preferred wax is paraffin wax.

S•oThe preferred ratio of glycol to wax is from about 1:3 to about 1:12. More preferred is a ratio of about 1:4 to about 1:8. Even more preferred is a ratio of about 1:6.

S•According to a second aspect there is provided an concrete curing concentrate including a composition according to the first aspect and water.

•eooo Preferably the concentrate includes from about 5% to about 15% polyethylene •glycol, from about 52% to about 62% paraffin wax and from about 23% to about 43% -3awater. Even more preferred is a concentrate which includes about 10% polyethylene glycol, about 57% paraffin wax and about 33% water. Also preferred is a concentrate with a high solids content, for example in excess of 50%. Conveniently the concentrate is prepared in two parts, one including the paraffin wax and water, and the other polyethylene glycol. It would be understood however that polyethylene glycol and water may constitute one of the parts of the concentrate while the other part may be the paraffin wax. The two parts are combined to form the internal curing composition before addition to cement or a cementitious mix such as concrete. Optionally, the two parts of the concentrate may be added as separate components either simultaneously or sequentially in any order.

According to a third aspect there is provided a cementitious mix including a composition according to the first aspect or a concentrate according to the second aspect.

According to a fourth aspect there is provided a concrete mix including a composition according to the first aspect or a concentrate according to the second aspect.

Preferably the internal curing concentrate is present in the amount of about 2 I/m 3 to about 10 I/m 3 of cement or cementitious mix. Even more preferred is the amount of l/m 3 According to a fifth aspect there is provided a method of preparing internally curing cementitious mix or internally curing concrete mix including combining cement and aggregate with a composition according to the first aspect or a concentrate according to the second aspect, in the amount sufficient to enable a slurry or a paste prepared from said cementitious mix or said concrete mix to cure.

According to a sixth aspect there is provided a method of preparing internally curing concrete structure including combining cement and aggregate with a composition according to the first aspect or a concentrate according to the second aspect in the amount sufficient to enable said concrete structure to cure.

Preferably the glycol and the wax are added simultaneously. It will be understood that in alternative embodiments of the present invention the glycol and the wax can be added sequentially in any order. Further, in preferred embodiments the internal curing concentrate is to be added without dilution. Optionally, however, the internal curing concentrate may be diluted with water before use.

According to a seventh aspect there is provided a method of preparing internally curing concrete structure including combining a mix according to the third or the fourth aspect and water.

According to an eighth aspect there is provided a a cementitious mix, a concrete mix or a concrete structure, when prepared by the method of any one of fifth, sixth or seventh aspects.

The term "cementitious mix" as used in the context of the present invention is intended to include mixes such as mortar, concrete and such like, and which may include other additives such as lime, plasticizers, defoamers, retarders, accelerators, water reducers, etc. However, the term "concrete" may be independently used in reference to a mix of cement and aggregate consisting of sand and/or gravel, which may also contain lime and plasticizers, defoamers, retarders, accelerators, water reducers, etc.

The term "aggregate" as used in the context of the present invention includes materials such as sand, gravel and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 Compressive strength at 7 days of age of specimens cured under different methods; at 28 days of age of specimens cured under different methods Fig.2 Porosity of concrete cured under different methods Fig.3 Rate of evaporation versus age, from 200x200x50mm concrete slabs curing using internal curing compositions (dosage 5 I/m 3 DESCRIPTION OF THE PREFERRED EMBODIMENTS Self-curing is an "internal curing system" where a water soluble polymer is added to the concrete mix. This method overcomes the difficulty in ensuring that 10 effective curing procedures are employed by the construction personnel as the internal curing composition is a component of the mix. The mechanism of self-curing can be explained as follows: Continuous evaporation of moisture takes place from an exposed surface due to the difference in chemical potentials (free energy) between the vapour and liquid phases. The polymers added in the mix mainly form hydrogen bonds with water molecules and reduce the chemical potential of the molecules which in turn reduces the vapour pressure. This reduces the rate of evaporation from the surface.

The effect of curing, particularly new techniques such as "self-curing", on the properties of high performance concrete is of primary importance to the modern 20 concrete industry. As an initial step, the effect of self-curing compositions, including that of the present invention, on moisture retention, strength development, porosity, permeability and shrinkage was investigated. Long-term strength development was also included in the test programme. The composition of the present invention, which is a combination of a wax and a glycol, was compared with one type of curing membrane, as an example of a traditional method of curing, and two internal curing compositions already known in the field, and results were compared with the traditional methods of water curing in a laboratory experimental programme. The test programme is detailed in Table 1

C

Table 1. Test Proqramme for self-curinq concrete Proiect Test Specimen Test parameter Curing conditions No curing 3day water 7day water Membrane mnt Cur 1I mt Cur 2 Int Cur 3.

Concrete slabs Evaporation rate 200x200xlOOmm up to 28 days Prisms e Shrinkage 75x75x285mm Weight loss Cylinders 7-day comp. 1 OOx200mmn Strength Concrete slabs strength 300x200x5Omm evaporation Note: Test carried out as at July 1998

EXPERIMENTAL

Example 1. Internal curing compositions and curing membrane The properties of the curing membrane and the internal curing compositions used are given in Table 2. Internal curing composition 3 is generically similar to that described in the technical literature Internal curing composition 1 is a commercially available product sold under the name of MEYCO TCC 735 (MBT, Australia). Internal curing composition 2 is the concrete curing composition of the present invention. For the purposes of this study, internal curing composition 2 consisted of paraffin wax polyethylene glycol and water The paraffin wax used is an off-white solid and has a melting point of approximately 580C (Cas No. 8002-74-2). Other suitable waxes can be employed such as Microcrystalline wax or a combination of paraffin wax and microcrystalline wax. The preferred polyethylene glycol (PEG) has a molecular weight of approximately 200 and is an odourless liquid (Cas No. 25322-68-3) but PEG can also be selected from a broader range of molecular weights, for example MW 200 to 10,000. Similarly, PEG can be replace with methoxypolyethylene glycol (MPEG) selected from a molecular weight range of MW350 to 5,000.

*It will be understood by those skilled in the art that cementitious mixes which employ large aggregates may use less internal curing composition due to surface area considerations and lower porosity, which results in smaller reaction areas, than mixes prepared with finer aggregates which have larger surface area and greater porosity resulting in increased propensity to lose moisture.

The membrane-forming curing compound (Masterkure 200R, MBT, Australia) used on the surface of the test specimens is a solvent borne resin with an efficiency of 94% as determined in accordance with AS 3799 (1998) Table 2. Characteristics of Internal Curing Compositions and membrane-forming curing compound.

Curing Material Curing Int. Curing Int. Curing Int. Curing Membrane Comp. 1 Comp. 2 Comp. 3 Base material Solvent Water, wax Water, paraffin Water-based borne resin emulsion and wax &polyethylene polyethers with dye high MW glycol polyethylene oxide Solids content(%) 48 25 64 71 Specific Gravity 0.89 0.978 0.934 1.110 Curing Efficiency 94* Appearance Clear Red Milky Milky Emulsion Dark liquid liquid Emulsion Viscosity Low Low Low Low Solubility in water Not Soluble Low Solubility Low Solubility Low Solubility Tested according to AS 3799 1998 Example 2. Binder Types A type GP cement was used in the initial programme and the mixes do not have any other chemical admixtures such as superplasticizers. However, some slabs with a mix containing a superplasticizer have also been investigated. The compatibility between the internal curing compositions and superplasticizers is an important consideration. The mix proportions, used in the initial investigation, with Type GP cement are shown in Table 3.

Subsequent investigations included fly ash and slag replacements. The mix with fly ash contains 25% of the cement replacement and the mix with slag contains of cement replacement.

Table 3. Details of the mix with Type GP cement per m 3 Mix 1 Mix 2 Mix 3 Mix 4 Binder type Type GP Type GP Type GP Type GP cement cement cement cement Cement (kg) 470 470 470 470 Sydney sand (kg) 565 565 565 565 Nepean gravel -20mm crushed 940 940 940 940 (kg) Water (kg) 188 188 188 188 Internal curing comp. 1 (litres) 2,5,10 Internal curing comp. 2 (litres) ___2,5,10 Internal curing comp. 3 (litres) 2,5,10 Example 3. Preparation of Specimens Concrete slabs of 200x200x100mm were cast in steel moulds. Soon after the surface water has disappeared (2-3 hours after casting), the specimens were transferred to the controlled environment. The specimens were demoulded after 1 day and kept in the controlled environment of 23±2 0 C and 50±5% R.H. Cylinders and prisms were also cast and kept under the same environment until testing for compressive strength or shrinkage. To avoid any possible interaction between the mould releasing agent and the polymers used, the steel moulds were lined with 'Rencourse' (aluminium core damp course) lining which served as a moisture barrier on five sides of the slabs exposing only the top surface. The following curing methods were used: no curing (ii) 3 day water curing by ponding and these specimens were stored in the fog room at 23°C. The specimens were removed to the controlled environment after 3 days.

(iii) 7 day water curing by ponding and these specimens were stored in the fog room at 230C. The specimens were removed to the controlled environment after 7 days.

(iv) curing by the application of a curing membrane (solvent based resin curing compound with a dye) applied evenly at a rate of 0.2 litres/m 2 with a spraying equipment.

l* o 15 curing using the internal curing compositions at a dosage of typically 5 litres per m 3 S.In addition to the slabs, it was necessary to cast a number of cylinders as companion specimens in order to measure certain properties as detailed below. All the companion specimens were subjected to exactly the same curing methods as their respective slabs.

Example 4. Test Methods Rate of evaporation Moisture loss due to evaporation from the surface of the concrete slabs was measured periodically up to an age of 28 days using an electronic balance with a resolution of 0.1 g. The exposed surface of the slab is as cast and the other five surfaces were sealed with a water proofing sheet which consists of an aluminium foil core (Rencourse). The top edges of the specimens were also sealed.

Compressive strength AS 1012 [261 Compressive strength was measured at ages of 3, 7 and 28 days using 100 mm diameter concrete cylinders, cured and stored in the same environment as the slabs. In addition a number of cores cut from the slabs were also tested for comparison with the cylinders.

Porosity -RILEM Method [27] Porosity of concrete was determined using a vacuum saturation method The oven-dried specimens were evacuated dry for 1 hour and a further evacuation was carried out for 1 hour after introducing water in order to saturate the specimens. The porosity was then calculated from the oven-dry weight, saturated weight and submerged weight of the specimens.

Water absorption RILEM Method [27] From the vacuum saturation method for porosity measurement, it was also possible to obtain values for the total water absorption. These values based on an oven-dry basis of the specimens are reported here.

Test Results and Discussion oo The results obtained to date are presented and discussed below. These include compressive strength development with different dosages, porosity, water absorption t. and rate of evaporation. Comments are also made on the shrinkage of the specimens cured under different methods.

.15 Compressive Strength Development Compressive strength developments of concrete curing under different curing methods are compared in Figures l(a) and At 7 days of age, specimens water too 9cured for 7 days showed the highest compressive strength of 40MPa and specimens water cured for 3 days showed a strength of 38Mpa. Membrane method of curing showed a comparable strength of 38Mpa. Internal curing compositions 1 and 2 showed a strength above 35 MPa at dosages of 2 and 5 l/m 3 Internal curing composition 3 showed a strength slightly below 35 MPa at the above dosages. At a dosage of 10 I/m 3 internal curing compositions 1 and 2 showed a slight reduction in strength. However, composition 3, at a dosage of 10 I/m 3 showed a considerable reduction to give a strength of only 29MPa. When compared with 3-day water cured and membrane cured specimens, this is a reduction of about 24%.

At 28 days of age, specimens with 7-day and 3-day water curing showed strengths of 58MPa and 55MPa, respectively, and the membrane method of curing showed a strength of 49MPa. At a dosage of 5 l/m 3 internal curing composition 2 gave a comparable result (to the membrane method of curing) of 51MPa but internal curing composition 3 gave a lower result of 47MPa. This is a reduction of 15% when compared with 32 day water curing.

At dosages of 2 and 5 I/m 3 internal curing compositions 1 and 2 give compressive strengths comparable to those specimens cured using a high quality membrane. Internal curing composition 3 appears to give significantly lower compressive strengths.

Porosities of concrete, as determined by a vacuum saturation method, at 7 and 28 days of age are compared in Fig.2. Internal curing composition 2 gave porosity values similar to the membrane cured specimens but internal curing composition 3 showed no reduction in porosities when compared with a non-cured specimen, particularly at an early age of 7 days.

The rate of evaporation at 23 0 C and 50% R.H. of 50mm thick concrete slabs are compared in Fig. 3.

Internal curing composition 2 was performing similar to the membrane after 28 days and is better than 3-day water curing. A specimen cured in water for 3 days and then exposed to the same environment lost more moisture after 28 days when compared with both membrane method and internal curing composition 2 method. In both these cases, the rates of evaporation of moisture from the slabs were considerably lower than those of a non-cured slab.

The water absorption, determined from the saturated, submerged and oven-dry weights of specimens cured under different conditions are shown in Table 4. Water absorption clearly distinguishes the different curing methods. Water curing for 3 days, .*membrane method and internal curing composition 2 clearly show a substantial reduction in the absorption values when compared with the other methods.

Table 4 Water Absorption under different curing conditions (based on oven-dried basis) Curing Condition 7 Day Absorption 28 Day Absorption No Curing 5.10 5.04 3 Day Water Curing 3.24 3.15 Curing Membrane 3.88 3.28 Internal Curing Composition 1 4.90 4.78 Internal Curing Composition 2 3.99 3.31 Internal Curing Composition 3 4.71 4.45 Some of the conclusions which can be drawn from the results available to date are as follows: 1. Internal curing composition 2 of the present invention retained moisture similar to the solvent borne resin membrane and performs better than 3-day water curing.

2. At dosages from 2 to 5 I/m 3 the strength development of the three internal curing compositions were compared. Internal curing compositions 1 and 2 give compressive strengths similar to a high quality solvent borne resin membrane.

However, internal curing composition 3 appears to show a significantly lower strength, particularly, at the highest dosages.

3. Porosity and absorption values obtained with internal curing composition 2 are comparable to that cured with the solvent borne resin membrane. These values are also comparable to 3-day water curing.

"oo 9.oOInternal curing composition of the present invention provides significant advantages over the known compositions and provides for the first time a reliable means of S.9: ensuring that proper curing is carried out and eliminates the need for. external curing procedures.

Although the present invention has been described with reference to preferred embodiments, it will be understood that variations which are in keeping with the spirit and intent of the invention are also contemplated and fall within its scope.

Soo to.

*to* so** Got* 13 References 1. Neville,A.M., "Properties of concrete," 3rd Edition, Pitman, 1981, 779pp.

2. Powers,T.C., "The physical structure and engineering properties of concrete," Portland Cement Association Research Dept. Bullettin 90, Chicago, 1958, 39pp.

3. Dhir,RK, Hewlett, P.C. and Dyer,T.D., "Influence of microstructure on the physical properties of self-curing concrete," ACI Materials Journal, Vol.93, No.5, Sept- Oct. 1996 pp465-471.

4. Dhir,RX., Hewlett, Lota, J.S. and Dyer,T.D, "An investigation into the 10 feasibility of formulating self-cure concrete," RILEM Materials and Structures, Vol.27, 1994, pp606-615.

5. Parrott, "Moisture profiles in drying concrete," Advances in cement Sresearch (UK),Vol. 1, No.3, July 1988, ppl64-170.

6. British Standards Institution, Specification for aggregates from natural sources 15 for concrete BS 882, 1983.

7. Cabreni, J.G. and Lyrisdale, A new gas permeameter for measuring the permeability of mortar and concrete, Magazine of Concrete Research, Vol. 40. No. 144, September 1988, ppl77-182.

8. Cabrera, LG. and Lyrisdale, Measurement of chloride permeability in super-plasticised ordinary Portland cement and pozzolanic cement mortars, Proceedings of the International Conference on Measurement and Testing in Civil Engineering, Lyon, France, Vol. 1, 13-16 September 1988, pp 279-291.

9. British Standards Institution, Methods of testing hardened concrete for other than strength, BS 1881: Part 5, 1970.

10. Cabrera, Gowripalan,N. and Wainwright, "An assessment of concrete curing efficiency using gas permeability," Magazine of Concrete Research, Vol.41, No.149, December 1989, pp 193-198.

11. Patel, Killoh, Parrott, L.J. and Cutteridge, Influence of curing at different relative humidities upon compound reactions and porosity in Portland cement paste," Materials and Structures: Research and Testing, Vol. 2 1, No. 123, May 1988, pp 192-197.

12. Gowripalan, Cabrera, Cusens, A.R. and Wainwright, "Effect of curing procedure on some durability-related properties of concrete," Concrete International, Vol. 12, No.2, February 1990, pp47-54.

13. Commonwealth Experimental Building Station, Australia, Curing compounds and bonding agents for concrete and their effects on strength development and adhesion, Technical Record TR 521751409, February 1973, 22pp.

14. British Standards Institution, Method of testing for curing compounds for concrete, DD 147, DRAFTFOR DEVELOPMENT, 1987.

15. American Society for Testing and Materials, Standard test method for water retention by concrete curing materials, C156-95, 1997.

16. Senbetta, E. And Scholer, "A new approach for testing concrete curing efficiency," ACI Journal, Vol. 8 1, No. 1, Jan-Feb. 1984, pp82- 86.

17. Figg, LW., "Methods of measuring the air and water permeability of concrete," Magazine of Concrete Research, Vol. 25, No. 85, December 1973, pp213-219.

18. Montgomery, F.R. and Adams, "Early experience with a new concrete S. permeability apparatus," Proceedings of Second International Conference on Structural Faults and Repair, London, 30 April 2 May 1985, Edinburgh Engineering Technics 20 Press, 1985, pp359-363.

19. American Society. for Testing and Materials, "Evaluating the effectiveness of materials for curing concrete," CI 151-91, 1997.

Cabrera, LG., Gowripalan, N. and Wainwright, P.L, "Curing of concrete in hot environments Assessment of the efficiency of curing membranes by measuring permeability and pore structure." Proceedings of the Third International Conference on Deterioration and Repair of Reinforced Concrete in the Arabian Gulf, 21-24 October 1989, pp529-542.

21. Parrott, "Influence of cement type and curing on the drying and air permeability of cover concrete," Magazine of Concrete Research, Vol.47, No 17 1, June 1995, pp 103-111.

22. Day,R.L. and Shi, "Effect of initial water curing on the hydration of cements containing natural pozzalan," Cement and concrete Research, Vol.24, No.3, 1994, pp463-472.

23. Alsayed,S.H., and Arrijad,M.A., "Effect of curing conditions on strength, porosity, absorptivity and shrinkage of concrete in hot and dry climate, Vol.24, No.7, 1994, pp1390-1398.

24. Wang, Dhir, RX. and Levitt, "Membrane curing of concrete: Moisture loss," Cement and concrete Research, Vol.24, No.8, 1994, ppl463-1474.

AS 3799, Liquid membrane-forming Curing Compounds for concrete, Standards Australia, 1998,32pp.

26. AS 1012.9, Method of Testing Concrete Determination of the compressive strength of concrete specimens, Standards Australia, 1986.Wii 27. RILEM RECOMMENDATIONS CPC 11.3, Absorption of water by immersion under vacutin Materials and Structures: Research and Testing, Vol.17, No.101, Sept- 15 Oct. 1984, pp391-394.

28. Leikauf, B. and Oppliger,M., Durability of Concrete Quality Improvement by New Admixture types, (prepared for presentation at the 5th CANMET/ACI International Conference on Superplasticizers and Other Chemical. Admixtures in Concrete), Research and Development of Underground Construction-MBT, Switzerland, 20 November 1996, 14pp.

Claims (29)

1. A composition including a glycol and a wax, wherein said composition internally cures concrete.

2. A composition according to claim 1 wherein the glycol is polyethylene glycol or methoxypolyethylene glycol.

3. A composition according to claim 1 or claim 2 wherein the glycol is polyethylene glycol.

4. A composition according to any one of claims 1 to 3 wherein the wax is paraffin wax, microcrystalline wax or mixtures thereof.

5. A composition according to any one of claims 1 to 4 wherein the wax is paraffin wax.

6. A composition according to any one of claims 2 to 5 wherein polyethylene glycol is selected from molecular weight range of about 200 to about 10,000.

7. A composition according to claim 6 wherein the polyethylene glycol has a molecular weight of about 200.

8. A composition according to any one of claims 2 to 5 wherein methoxypolyethylene glycol is selected from molecular weight range of about 350 to about 5,000.

9. A composition according to any one of claims 1 to 8 wherein the ratio of glycol to wax is from about 1:3 to about 1:12. A composition according to claim 9, wherein the ratio of glycol to wax is from about 1:4 to about 1:8.

11. A composition according to claim 9, wherein the ratio of glycol to wax is about 1:6. -17-

12. A concrete curing concentrate including a composition according to any one of claims 1 to 11, and water.

13. A concentrate according to claim 12, including from about 5% to about polyethylene glycol, from about 52% to about 62% paraffin wax and from about 23% to about 43% water.

14. A concentrate according to claim 13, including about 10% polyethylene glycol, about 57% paraffin wax and about 33% water. A cementitious mix including a composition according to any one of claims 1 to 11 or a concentrate according to any one of claims 12 to 14.

16. A concrete mix including a composition according to any one of claims 1 to 11 or a concentrate according to any one of claims 12 to 14.

17. A mix according to claim 15 or claim 16, further including water in the amount sufficient to prepare a slurry or a paste suitable for forming structures.

18. A mix according to any one of claims 15 to 17, wherein the composition or the concentrate are present in the amount sufficient to cure the paste or slurry prepared from said mix. ooo• •19. A mix according to any one of claims 15 to 18 wherein the concentrate is present in the amount of about 2 1/m 3 to about 10 1/im 3 of the mix. A mix according to claim 19, wherein the concentrate is present in the amount of about 5 1/m 3

21. A structure formed from the cementitious mix or the concrete mix according to any one of claims 15 to

22. A method of preparing internally curing cementitious mix or internally curing concrete mix including combining cement and aggregate with a composition according to any one of claims to 11 or a concentrate according to any one of claims 12 to 14 in to any one of claims 1 to 11 or a concentrate according to any one of claims 12 to 14 in -18- the amount sufficient to enable a slurry or a paste prepared from said cementitious mix or said concrete mix to cure.

23. A method according to claim 22, further including the addition of water.

24. A method of preparing internally curing concrete structure including combining cement and aggregate with a composition according to any one of claims 1 to 11 or a concentrate according to any one of claims 12 to 14 in the amount sufficient to enable said concrete structure to cure. A method of preparing internally curing concrete structure including combining a mix according to any one of claims 15 to 20 and water.

26. A method of any one of claims 22 to 25, wherein the glycol and the wax are added simultaneously.

27. A method according to claim 26 wherein water is added simultaneously.

28. A cementitious mix, a concrete mix or a concrete structure, when prepared by the method of any one of claims 20 to 27.

29. A composition, substantially as herein described with reference to any one of the examples.

30. A concrete curing concentrate, substantially as herein described with reference to j any one of the examples. S•31. A cementitious or concrete mix, substantially as herein described with reference to any one of the examples.

32. A structure, substantially as herein described with reference to any one of the examples. ooooo o• 19

33. A method of preparing internally curing cementitious mix, concrete mix or a concrete structure, substantially as herein described with reference to any one of the examples. DATED this 30th Day of December, 2003 BALD WTN SHELSTON WATERS Attorneys for: MBT HOLDING AG S S S *0 S S S S 5 S S. 555 5 55 C S S S *5 9

55.5 .55. 5.555. S 55.5 9

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