WO2013139961A1

WO2013139961A1 - A composition for production of construction materials

Info

Publication number: WO2013139961A1
Application number: PCT/EP2013/056069
Authority: WO
Inventors: Mohammad Hajmohammadian BAGHBAN
Original assignee: INSTITUTT FOR BYGG ANLEGG OG TRANSPORT
Current assignee: INSTITUTT FOR BYGG ANLEGG OG TRANSPORT
Priority date: 2012-03-23
Filing date: 2013-03-22
Publication date: 2013-09-26
Anticipated expiration: 2014-09-23
Also published as: NO20141145A1

Description

A COMPOSITION FOR PRODUCTION OF CONSTRUCTION MATERIALS

Field of invention The present invention concerns novel construction material compositions, and the use of such compositions in the production of building elements.

Background A building material which have properties such as a high heat and sound insulation, good fire resistance, light weight, versatility and quick production and installation has always been the dream material for architects and builders.

Different types of concretes such as light weight aggregate concrete or aerated autoclaved concrete have been under development in the last years to obtain building materials with improved properties.

WO 201 166209 discloses the use of aerogel granules as aggregates in concrete to improve the material properties. Since aerogel granules have low thermal conductivity, relatively high strength and are resistant to fire; they can be a good option for this purpose. A special type of surfactant is usually used in this type of product for dispersing aerogel granules in concrete. However since thermal conduction of the solid part of hardened portland cement paste in the composite is much higher than of conventional aerogels, the matrix acts like thermal bridge in the composite system and results in a concrete with much higher thermal conductivity than the thermal conductivity of typical aerogel granules.

US 5645518 discloses the use of chemically bonded phosphate ceramics as alternatives to Portland cement due to their outstanding properties. Such ceramics can be made without firing which makes them easier, cheaper and more

environmentally friendly to produce. Furthermore, comparison between the energy costs for producing such types of binders compared to Portland cement showed that production of these binders usually demands much less energy compared to production of Portland cement ("Chemically bonded phosphate ceramics", book by Wagh, 2004). Magnesium potassium phosphate ceramic is an example of such type of ceramics. Dissolving mono-potassium phosphate (KH₂PO₄) in water results in an acidic solution in which magnesium oxide (MgO) can be dissolved and an acid-base reaction initiates between the two dissolved components. Usually a small amount of boric acid is also used as retardant to slow the setting. Moreover, since the acid-base reaction is highly exothermic, the reaction rate of the dissolved components needs to be slowed down by using additional materials or methods to avoid the rapid setting of the slurry and thus ending up with an incomplete product with no workability, especially for production in large size. Thus, to slow down the reaction rate, MgO is calcined at 1300 °C prior to mixing in order to reduce its solubility for practical applications. See for instance US patent no. 6,776,837 and 6,204,214, wherein the desired use of calcined MgO in the production of phosphate ceramics is disclosed. However, even using calcined MgO and boric acid may not be enough for reducing the exothermic heat of the reaction and thus mono-potassium phosphate with low solubility of for example about 15 g/1 has been used for this purpose, see Wagh, et al, Oil & Gas Journal, May 9, 2005, p. 53-55. Moreover, higher compressive strength and lower thermal conductivity than conventional Portland cement can be obtained by adding fly ash [US patent 5,830,815] or silicate [US patent 6,518,212] to the mixture. Based on the above it is recognized that there is a clear demand for construction materials having improved properties compared to the prior art construction materials.

Summary of the invention

The present invention provides a composition for producing construction materials having improved properties compared to prior art materials. In the production process the composition is mixed with water to provide the desired construction material.

The scope of the invention is defined by the appended claims, and the invention is further described in the following:

The present invention provides a composition for the production of construction materials, comprising:

15-80 wt% hydrophobic aerogel granules based on the total weight of the composition;

- uncalcined MgO; and

an alkali phosphate salt;

wherein the molecular ratio between uncalcined MgO and phosphate is in the range of 0.75- 1.25.

In one aspect of the invention, the composition comprises 20-80 wt% hydrophobic aerogel granules based on the total weight of the composition, preferably 30-80 wt%.

In a further aspect of the invention, the composition comprises 5-25 wt% uncalcined MgO.

In a further aspect of the invention, the composition comprises 15-65 wt% of alkali phosphate salt.

In a further aspect of the invention, the composition comprises a alkali phosphate salt selected from a group consisting of mono-potassium phosphate, dipotassium phosphate, mono-sodium phosphate and disodium phosphate, and any combination thereof, preferably the alkali phosphate salt is mono-potassium phosphate.

In a further aspect of the invention, the mono-potassium phosphate has a water- solubility of at least 15 g/1, at least 100 g/1, or preferably at least 200 g/1 at 25 °C.

In a further aspect of the invention, the composition is able to form a homogenous slurry which cure without separation when mixed with water in the range of 50-600 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt, preferably in the range of 100-600 wt% or 150-600 wt%, and even more preferred 200-600 wt%.

The term homogenous slurry is in this application intended to define a slurry being overall homogenous, or uniform, in the sense that it does not separate into phases of different viscosity.

In a further aspect of the invention the amount of water is in the range of 15-70 wt% based on the total weight of the composition. In a further aspect of the invention the homogenous, or uniform, slurry would comprise 5-65% wt% of hydrophobic aerogel granules based on the total weight of the slurry. In a further aspect of the invention, the composition comprises at least one additive selected from fly ash, silicate materials, foaming agents, surfactants, fibers and aggregates.

In yet a further aspect, the invention provides a construction material produced by mixing a composition according to the invention and water, wherein the amount of water is in the range of 50-600 wt%, 100-600 wt%, 150-600 wt%, or 200-600 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt.

In a further aspect of the invention, the construction material has a thermal conductivity of less than 0.040 W/mK, less than 0.030 W/mK, less than 0.025 W/mK or even more preferred less than 0.020 W/mK.

In a further aspect of the invention, the construction material has a compressive strength higher than 0.3 MPa, 1 MPa, 3 MPa, 10 MPa or 20 MPa, and even more preferred higher than 60 MPa.

In a further aspect of the invention, the construction material comprises 5-65 wt% of hydrophobic aerogel granules based on the total weight of the construction material. In yet a further aspect, the invention provides the use of a composition according to the invention, for preparing a construction material, preferably a self-supporting concrete type construction material.

In yet a further aspect, the invention provides a process for the production of a construction material comprising the step of mixing a composition according to the invention and water, wherein the amount of water is in the range of 50-600 wt%, 100-600 wt%, 150-600 wt%, or 200-600 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt. Alternatively, the amount of water is more than 100 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt, preferably more than 150 wt%, more than 200 wt%, and even more preferred more than 300 wt%.

In yet a further aspect, the composition of the invention is able to form a homogenous slurry which cure without separation when mixed with water in an amount of more than 100 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt, preferably more than 150 wt%, more than 200 wt%, and even more preferred more than 300 wt%.

In yet a further aspect, the invention provides a construction material produced by mixing a composition according to the invention and water, wherein the amount of water is more than 100 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt, preferably more than 150 wt%, more than 200 wt%, and even more preferred more than 300 wt%. Detailed description of the invention

The present invention provides a composite, or composition, containing aerogel granules, magnesium oxide and an alkali phosphate salt. The phosphate and the magnesium oxide form a chemically bonded phosphate ceramic when mixed with water. The construction material obtained after mixing the composition according to the invention with water, will have a much lower thermal conductivity than the prior art concretes. Nevertheless, it is noteworthy that although replacing Portland cement with chemically bonded phosphate ceramics results in a matrix with lower thermal conductivity, the thermal conduction of the matrix will still be much higher than the aerogel granules. Thus, a method is proposed to further reduce the thermal conductivity of the matrix which leads to an even more environmentally friendly construction material and a more cost effective composition as well.

The porosity of a concrete-type construction material is, among many factors, dependent on the water-cement ratio. The cement is here considered as the total amount of MgO and phosphate salt. The maximum water-cement ratio may for example be limited to less than 60 % of the cement weight for ordinary Portland cement pastes. Special techniques and methods, such as rotating curing or chemical stabilizers, are needed to avoid separation if increased water content is desired. The amount of water normally used in the magnesium potassium phosphate ceramic mixes is about 50 % of the cement weight (weight of MgO and KH₂P0₄).

To further lower the thermal conductivity of the construction material produced by the composition of the invention, the porosity of the matrix around the aerogel aggregates is increased by substantially increasing the water-cement ratio without causing separation.

The applicant discovered a method of increasing the amount of water to more than 550 wt% of the cement weight (MgO and KH₂PO₄) while still obtaining a paste having a proper consistency, i.e. not a water like slurry, but a homogenous paste which is firm enough to avoid separation while curing.

This substantial increase in water content was predominantly obtained by replacing calcined MgO with uncalcined MgO in the above-mentioned composition

comprising aerogel granules, magnesium oxide and an alkali phosphate salt, preferably mono-potassium phosphate. The uncalcined MgO has finer and more porous particles compared to the calcined MgO, and is also much more reactive towards water and phosphate. The use of uncalcined MgO also leads to a more environmentally friendly product due to elimination of the calcination process which has a high energy demand. Using uncalcined MgO may not be feasible for practical applications in the prior art mixes comprising magnesium potassium phosphate ceramic, since the attempt of making the ceramic in large scale may fail due to a very high exothermic heat production. However, using hydrophobic aerogel granules in the mix as aggregates reduces the total exothermic heat production in the volume compared to the plain magnesium potassium phosphate ceramic mixes. Furthermore, the demand for water will further increase by using the hydrophobic aerogel granules, and the increased amount of water in the mix helps cooling the mixture during the mixing process. In fact, using uncalcined MgO with finer particles and hydrophobic aerogel granules helps to increase the water content of the mix, and increasing the water content together with using hydrophobic aerogel granules as aggregate make it practical to use uncalcined MgO with fine particles instead of calcined MgO. The particle size of the uncalcined MgO is normally in the range of 5 nm - 400 μιη, wherein a finer particle size increases the water demand. However, use of MgO powder with particle size of less than 5 nm is also possible, but such powders are usually very expensive. Therefore, from an economic aspect it is sufficient to use powder with a particle size not impairing the adhesion force during cement setting.

Aerogels in the sense of the present invention include colloidal substances which are gelled and dried. They have low density and high porosity. The solid substance is only about 1 to 15 volume %, of the aerogel. The rest of its volume is gas, or even vacuum, which means that they have a high surface area (up to 1000 m²/g). Inorganic aerogels are usually hydrophilic by themselves and are considered one of the lightest materials and one of the best heat insulators. Aerogel granulates may be obtained by grinding of aerogel monoliths. Hydrophobic in the sense of the present invention is water-repellent, is that the used aerogel shows a marked interaction with polar solvents like water. The used hydrophobic aerogel granulates have a water contact angle > 90 °. Hydrophobic aerogel granulates are often obtained from hydrophilic aerogel granulates by a hydrophobizing treatment. Inorganic, that is mostly oxidic, aerogels for example, in many cases still contain free OH-groups and are therefore hydrophilic. By a hydrophobizing treatment, such as an etherification using trimethylsilyl chloride (TMSC1), can thus convert a hydrophilic aerogel into a hydrophobic aerogel. Alternatively, hydrophobic aerogel is prepared using hydrophobizing agents during the formation of the aerogel.

Alkali phosphate salts include all such salts suitable for use in a composition for the production of construction materials. These include water soluble phosphates like the various sodium and potassium salts, and especially mono-potassium phosphate. The phosphate salt, for instance mono-potassium phosphate salt, has an initial solubility in water of more than 15 g/1 at 25 °C, and even more preferred about 220 g/1 at 25 °C. The initial solubility of mono-potassium phosphate is adjusted by the size and consistency of the particles used. Use of mono-potassium phosphate with high water solubility in the mixture will result in an even higher demand for water, faster setting, and finally even lower thermal conductivity.

Moreover, fly ash or other materials containing silicate can also be used in the mixture to further increase the total water demand and also increase the strength. Other types of chemically bonded phosphate ceramics or other types of binders, like Portland cement and gypsym, can also be used for modification of the material properties.

Moreover, foaming agents can be added to the mix to introduce macro air pores to the composite and still further increase the porosity of the material. Other types of admixtures such as surfactants can also be used to improve the mechanical and thermal properties. Using hydrophobic agents during the mixing process or after mixing can also be beneficial in order to increase the durability and decrease the thermal conductivity of the material in moist condition such as in building envelopes in contact with rain, or for construction elements in contact with underground water or sea water. In addition, using different types of fibers can enhance mechanical or even thermal properties of the material. Phase change materials in either encapsulated form or without encapsulation as well as other materials with high specific heat capacity can also be introduced to the mixture to improve the thermal properties of the material. And finally different types of aggregates may be used in the mixture to modify the material properties.

Experimental part

Examples of various embodiments of the invention are listed in Table 1 below. wt % Thermal

Mix conductivity number

KH₂P0₄ MgO Water Aerogel granule Fly Ash

(W/mK)

1 12, 1 4,0 52,3 15,3 16,3 0,037

2 7,6 2,5 54,7 25, 1 10,1 0,028

3 39,0 13,0 39,0 9,0 0,0 0,065

4 15,0 5,0 25,0 55,0 0,0 0,019 Use of compositions as disclosed in the present application provides composite construction materials having advantageous properties such as light weight, versatility, quick production and installation, high thermal insulation, fire resistance and sound insulation.

Claims

1. A composition for the production of construction materials, comprising:

- uncalcined MgO; and

an alkali phosphate salt;

2. A composition according to claim 1 , comprising 20-80 wt% hydrophobic aerogel granules based on the total weight of the composition, preferably 30- 80 wt%.

3. A composition according to claim 1 or 2, comprising 5-25 wt% uncalcined MgO.

4. A composition according to any of the preceding claims, comprising 15-65 wt% of alkali phosphate salt.

5. A composition according to any of the preceding claims, wherein the alkali phosphate salt is selected from a group consisting of mono -potassium phosphate, dipotassium phosphate, mono-sodium phosphate and disodium phosphate, and any combination thereof, preferably the alkali phosphate salt is mono-potassium phosphate.

6. A composition according to claim 5, wherein the mono-potassium phosphate has a water-solubility of at least 15 g/1, at least 100 g/1, or preferably at least 200 g/1.

7. A composition according to any of the preceding claims, able to form a

homogenous slurry which cure without separation when mixed with water in the range of 50-600 wt% based on the combined weight of uncalcined MgO and alkali phosphate salt, preferably in the range of 100-600 wt% or 150-600 wt%, and even more preferred 200-600 wt%, or in an amount of more than 300 wt%.

8. A composition according to claim 7, wherein the amount of water

range of 15-70 wt% based on the total weight of the composition.

9. A composition according to claim 7 or 8, wherein the homogenous slurry would comprise 5-65% wt% of hydrophobic aerogel granules based on the total weight of the slurry.

10. A composition according to any of the preceding claims, comprising at least one additive selected from fly ash, silicate materials, foaming agents, surfactants, fibers and aggregates.

1 1. A construction material produced by mixing a composition according to any of claims 1-10 and water, wherein the amount of water is in the range of 50- 600 wt%, 100-600 wt%, 150-600 wt%, or 200-600 wt%, or more than 300 wt%, based on the combined weight of uncalcined MgO and alkali phosphate salt.

12. A construction material according to claim 1 1 , having a thermal conductivity of less than 0.040 W/mK, less than 0.030 W/mK, less than 0.025 W/mK or even more preferred less than 0.020 W/mK.

13. A construction material according to claim 1 1 or 12, having a compressive strength higher than 0.3 MPa, 1 MPa, 3 MPa, 10 MPa or 20 MPa, and even more preferred higher than 60 MPa.

14. A construction material according to any one of claims 1 1-13, comprising 5- 65 wt% of hydrophobic aerogel granules based on the total weight of the construction material.

15. Use of a composition according to any one of claims 1- 10, for preparing a construction material, preferably a self-supporting concrete type construction material.

16. A process for the production of a construction material comprising the step of mixing a composition according to any of claims 1-10 and water, wherein the amount of water is in the range of 50-600 wt%, 100-600 wt%, 150-600 wt%, or 200-600 wt%, or more than 300 wt%, based on the combined weight of uncalcined MgO and alkali phosphate salt.