GB2620363A

GB2620363A - Cementitious binder composition, a method for preparing the same and its uses

Info

Publication number: GB2620363A
Application number: GB2208851.2A
Authority: GB
Inventors: Bouaissi Aissa
Original assignee: Una Developments Ltd
Current assignee: Una Developments Ltd
Priority date: 2022-06-16
Filing date: 2022-06-16
Publication date: 2024-01-10
Also published as: GB202208851D0; WO2023242570A1

Abstract

A dry cementitious composition comprising a binder comprising ground granulated blast-furnace slag (GGBS), fly ash (FA) or a mixture thereof, and an activator comprising a silicate and a source of chloride ions (Cl-). A cement, mortar, concrete, grout or render prepared from the composition is defined, and a method wherein the cementitious composition is combined with water and cured. A component or structure prepared from the cementitious composition, or the cement, mortar, concrete, grout or render is also defined. The binder of the cementitious composition may further comprise a source of calcium (Ca2+) ions, which may be calcium hydroxide. The silicate may comprise an alkali metal or alkaline earth metal silicate, or a mixture thereof, and may be selected from sodium metasilicate (Na2SiO3), sodium orthosilicate (Na4SiO4), sodium pyrosilicate (Na6Si2O7), and mixtures thereof. The source of chloride ions may comprise an alkali metal or alkaline earth metal chloride, and may comprise calcium chloride. The cementitious composition may comprise one or more plasticiser or superplasticiser, which may be a blend of polycarboxylate polymers. The cementitious composition may further comprise an alkali metal hydroxide.

Description

CEMENTITIOUS BINDER COMPOSITION, A METHOD FOR PREPARING THE SAME

AND ITS USES

The present invention relates to a cementitious binder composition. The composition finds use, for example, in construction. The composition is of particular use when used as a binder and combined with a filler, for example an aggregate to form concrete. The present invention also relates to a method for preparing the cementitious binder composition and materials containing the cementitious binder composition.

It is well known and established in the art to form a range of construction materials, such as cement and concrete, from Portland cement. While Portland cement has been used extensively for many years, there are considerable environmental issues arising from its preparation and use. The production of Portland cement is highly energy intensive and requires an embodied energy of about 1300 kWh/tonne. In addition, the manufacture of a tonne of Portland cement results in the emission of about 0.8 tonne of carbon dioxide. Portland cement is used extensively in the production of concrete in combination with aggregate. Depending upon the composition of the concrete, the production of one tonne of Portland cement concrete requires about 150 to 250 kWh of embodied energy and products approximately 75 to 175 kg carbon dioxide.

There is a need for an alternative to Portland cement and other similar cements that are more environmentally friendly in both their production and use. A number of alternatives to Portland cement have been proposed in the art.

KR 101332346 discloses an inorganic binder composition comprising aluminosilicate and magnesium silicate minerals. The composition comprises silicon and aluminium in a molar ratio of 0.5 to 4.0, a mixture of SiO2 and Na2O in a molar ratio of from 0.5 to 2.5, Si02/Li20 in a molar ratio of 0.5 to 2.5 and SiO2/K2O in a molar ratio of 0.5 to 2.5. The binder composition may be prepared by combining appropriate amounts metakaolin, fly ash, blast furnace slag powder or silicafume. The binder composition has lower calcining temperature than conventional cementitious binders.

US 2014/0349104 discloses an inorganic polymer/organic polymer composite and a method of preparing the same. The inorganic polymer is formed by reacting a reactive powder, an activator and, optionally a retardant, in the presence of water. The reactive powder comprises 85% by weight or greater fly ash and less than 10% by weight Portland cement.

US 2015/0251951 concerns the production of bricks from mine tailings using geopolymerisation. A method for producing bricks is disclosed, which method comprises mixing mine tailings, in particular the tailings of copper mining, with alkaline solution. It is indicated that the bricks prepared in this manner do not require high temperature kiln firing.

More recently, WO 2016/023073 discloses geopolymers and geopolymer aggregates. The aggregates may be used in concrete. The geopolymer composition comprises fly ash or a fly ash substitute, an aluminium phyllosilicate, an alkaline component and water. The geopolymer composition is compacted under pressure and cured.

US 8,337,612 discloses an environmentally friendly composite construction material. The material is an alumina-silicate cementitious material and is formed by combining a pozzolanic material and/or a kaolin clay with an activator. The activator comprises sodium silicate and sodium hydroxide. The activator is combined with the pozzolanic material and/or kaolin clay, together with water. The material may be combined with or incorporate an aggregate, to form a concrete.

CN 101239800 discloses an inorganic non-metal fibre-reinforced cement-based composite material.

High-water-permeability concrete water-permeable ground tiles are disclosed in CN 108640617.

A geopolymer concrete is disclosed by A. Bouaissi, et al., 'Mechanical properties and microstructure analysis of FA-GGBS-HMNS based geopolymer concrete', Construction and Building Materials, 210 (2019), pages 198 to 209. The geopolymer concrete comprises class F fly ash (FA), ground granulated blast-furnace slag (GGBS) and high-magnesium nickel slag (HMNS). The geopolymer was activated using aqueous solutions of sodium silicate and sodium hydroxide.

More recently, WO 2021/116676 discloses a geopolymer composition comprising fly ash (FA), ground granulated blast-furnace slag (GGBS) and high-magnesium nickel slag (HMNS).

EP 3398918 discloses an activator composition comprising calcium oxide or lime and a superplasticiser. The activator may be used to form a cementitious binder from ground granulated blast-furnace slag (GGBS) and/or pulverised fuel ash (PFA).

A range of different materials and their potential to replace cement, in particular Ordinary Portland Cement, is discussed by A. Al-Mansour, et al., 'Green Concrete: By-Products Utilization and Advanced Approaches', Sustainability 2019, 11, 5145.

US 2017/0204008 discloses geopolymers and geopolymer aggregates comprising WO 2013/178967 discloses a cementitious binder comprising 90% by weight of a hydraulically active material, such as ground granulated blast-furnace slag (GGBS) and at least 0.1% by weight of an alkali activator.

WO 2013/179065 discloses a cementitious binder comprising 90% by weight of a hydraulically active material comprising ground granulated blast-furnace slag (GGBS) and/or pulverised fly ash (PFA) and at least 0.1% by weight of calcium oxide in an activator.

There remains a need for an improved cementitious binder composition that does not employ Portland cement. It would be advantageous if the cementitious binder composition could be prepared in an energy efficient manner. It would be further advantageous if the cementitious binder composition could be prepared using waste materials. It would also be advantageous if the cementitious binder composition could be easily stored, transported and activated on site in an easy manner by the end user. Still further, it would be advantageous if the cementitious composition could have an increased strength when cured.

It has been found that a cementitious composition can be prepared using a range of waste materials as a binder with only a minimal consumption of energy. The cementitious binder composition is a dry composition and is able to be activated at the location of end use merely by the addition of a low amount of water.

According to the present invention there is provided a dry cementitious composition comprising: a binder comprising ground granulated blast-furnace slag (GGBS), fly ash (FA) or a mixture thereof; and an activator comprising: a silicate; and a source of chloride ions.

The cementitious composition advantageously employs waste materials, in particular ground granulated blast-furnace slag (GGBS), pulverised fly ash (PFA) or a mixture thereof, optionally in combination with one or more other slags. It has been found that the cementitious composition of the present invention can be formed from these waste materials using a minimum amount of energy. This is in contrast to traditional Portland Cement. The cementitious composition is particularly useful as a binder, for example for aggregate, or a cement and when combined with water and allowed to cure can exhibit a very high strength, in particular a high compressive strength. A further advantage of the cementitious composition of the present invention is that it exhibits a lower heat of hydration than known compositions. This in turn results in a reduced temperature during the curing of the composition.

The cementitious composition of the present invention is a dry powder. In this respect, references to the composition being 'dry' are to the Loss on Ignition (L01) of the composition being below 10%, more preferably below 9%, still more preferably below 8%.

More preferably, the cementitious composition has a LOI within Category B, that is and LOI of 7%. Suitable methods for determining the LOI of the composition are known in the art and include: ASTM C 25 Standard test methods for chemical analysis of limestone, quicklime and hydrated lime; and ASTM C 114 Standard test methods for chemical analysis of hydraulic cement.

The cementitious composition of the present invention comprises a binder. The binder comprises ground granulated blast furnace slag (GGBS) and/or fly ash (FA).

Typical compositions for these components are summarised in Table 1 below. The compositions of these components may vary from those shown in Table 1, for example depending upon the source of the component material, as described in more detail below.

The binder of the cementitious composition of the present invention may comprise ground granulated blast furnace slag (GGBS). Ground granulated blast furnace slag is obtained by quenching molten iron slag produced in the production of iron and steel. The molten iron slag is removed from the blast furnace and typically quenched in water or steam to produce a glassy, granular product that is then dried and ground into a fine powder.

The composition of the ground granulated blast furnace slag (GGBS) depends upon the raw materials used in the iron or steel production, including the iron ore, coke and the flux employed.

It is known to use ground granulated blast furnace slag (GGBS) in combination with Portland cement to form concrete. Concrete made with ground granulated blast furnace slag (GGBS) cement sets more slowly than concrete made with ordinary Portland cement, depending on the amount of ground granulated blast furnace slag in the cementitious material. This results in a lower heat of hydration and lower temperature rises of the bulk concrete during curing. However, the slower setting rate can be disadvantageous and makes concretes containing significant amounts of ground granulated blast furnace slag (GGBS) undesirable or unacceptable for many applications where a high setting rate is required. The composition of the present invention exhibits a higher setting rate, as a result of the activator employed, discussed in more detail below.

The binder of the cementitious composition of the present invention may comprise ground granulated blast furnace slag (GGBS) in any suitable amount. If ground granulated blast furnace slag (GGBS) is present, it is preferably present in an amount of at least 5% by weight of the binder, more preferably at least 10% by weight, still more preferably at least 15%, more preferably still at least 20% by weight, especially at least 25% of the binder. The binder may consist essentially of ground granulated blast furnace slag (GGBS). In embodiments in which the binder comprises other components, ground granulated blast furnace slag (GGBS) may be present in the binder in an amount of up to 90% by weight, more preferably up to 85%, still more preferably up to 80%, more preferably still up to 75% by weight, especially up to 70% by weight. In some preferred embodiments, ground granulated blast furnace slag (GGBS) is present in the binder in an amount of from 5 to 75% by weight, preferably from 10 to 70%, more preferably from 15 to 65%, especially from 20 to 60% by weight.

The setting time of the cementitious composition may be controlled by varying the amount of ground granulated blast furnace slag (GGBS). In this respect, ground granulated blast furnace slag (GGBS) generally contains a significant amount of calcium oxide (CaO). The amount of calcium oxide present varies, depending upon the source of the ground granulated blast furnace slag (GGBS) and can be determined using X-ray fluorescence (XRF), as known in the art. In the composition, Ca 4+ ions are reactive and accelerate the chemical reactions within the mixture during the curing process. A high concentration of Ca ++ ions can lead to the formation of new phases of gels at a faster rate, thereby reducing the setting time of the composition, once activated.

The binder of the cementitious composition of the present invention may comprise fly ash (FA). Fly ash is a product of the combustion of coal and, as a result, is produced in large amounts, for example as a result of burning coal to generate electricity. Fly ash (FA) is a pozzolan, that is a substance containing aluminous and siliceous material. Depending upon the source and composition of the coal being burned, the components of fly ash (FA) vary considerably.

Fly ash has been used in Portland cement concrete as a mineral admixture, and more recently as a component of blended cement. As an admixture, fly ash (FA) functions as either a partial replacement for, or an addition to, Portland cement and is added directly into ready-mix concrete at the batch plant. ASTM C595 defines two blended cement products in which fly ash (FA) has been added: 1) Portland-pozzolan cement (Type IP), containing 15 to 40 percent pozzolan, or 2) Pozzolan modified Portland cement (Type IPM), containing less than 15 percent pozzolan.

ASTM C618 defines two classes of fly ash for use in concrete: 1) Class F, typically derived from the burning of anthracite or bituminous coal; and 2) Class C, typically derived from the burning of lignite or subbituminous coal.

ASTM C618 also specifies requirements for the physical, chemical; and mechanical properties for these two classes of fly ash. In particular, Class F fly ash is pozzolanic, with little or no cementing value alone. Class C fly ash has self-cementing properties as well as pozzolanic properties.

In the present invention, any type or class of fly ash (FA) or mixtures thereof may be used. Class F fly ash (FA) is preferred for use in the present invention. Preferably, the fly ash (FA) employed comprises a major portion of Class F fly ash, that is at least 50% by weight Class F fly ash, more preferably at least 60%, still more preferably at least 70%, more preferably still at least 80%, especially at least 90% by weight, more especially at least 95% by weight Class F fly ash. In a particularly preferred embodiment the fly ash (FA) component of the binder consists essentially of Class F fly ash.

The fly ash employed in the present invention is preferably pulverised fly ash (PEA).

The binder may comprise fly ash in any suitable amount. Preferably, fly ash is present in an amount of at least 10% by weight, more preferably at least 15% by weight, still more preferably at least 20%, more preferably still at least 25% by weight, especially at least 30% by weight of the binder. The binder may consist essentially of fly ash (FA). In embodiments in which the binder contains other components, fly ash (FA) is preferably present in an amount of up to 90% by weight, more preferably up to 85%, still more preferably up to 80%, more preferably still up to 75% by weight. In some preferred embodiments, fly ash is present in an amount of from 10 to 90% by weight, preferably from 15 to 85%, more preferably from 20 to 80%, especially from 25 to 75% by weight.

In one preferred embodiment, the binder comprises both granulated blast-furnace slag (GGBS) and fly ash (FA). In this embodiment, the weight ratio of fly ash (FA) to granulated blast-furnace slag (GGBS) may be from 0.25 to 4, preferably from 0.4 to 3.5, more preferably from 0.5 to 3.0, still more preferably from 0.6 to 2.75, more preferably still from 0.7 to 2.5. In some preferred embodiments, the ratio of fly ash (FA) to granulated blast-furnace slag (GGBS) is preferably at least 0.8, more preferably at least 0.9, especially at least 1. In some preferred embodiment, the ratio of fly ash (FA) to granulated blast-furnace slag (GGBS) is from 0.9 to 2.5, preferably from 1 to 2.35. In one preferred embodiment, the ratio of fly ash (FA) to granulated blast-furnace slag (GGBS) is 1. In an alternative preferred embodiment, the ratio of fly ash (FA) to granulated blast-furnace slag (GGBS) is 2.33.

The binder may contain other components. In one embodiment, the binder further comprises a source of calcium (Ca') ions. The inclusion of a source of calcium ions (Ca") can improve the curing or setting rate of the composition once activated, as discussed above. The inclusion of an additional source of calcium (Ca") ions is particularly preferred where the other components of the binder contain only low or insufficient amounts of calcium compounds able to provide calcium (Ca") ions. Any suitable source of calcium (Ca') ions may be used and include calcium salts, in particular water-soluble calcium salts. One preferred calcium salt is calcium hydroxide or lime (Ca(OH)2).

The addition of calcium hydroxide or lime can reduce the strength of the cementitious composition when cured or set. However, as noted above, its inclusion can improve the setting time, as well as the workability of the composition. As a result, the inclusion of calcium hydroxide or lime is preferred for compositions that will be employed as cements or mortar, where a faster curing time may be advantageous, but is less preferred for compositions that will be employed for concrete.

The source of calcium (Ca") ions may be present in any suitable amount to provide the required setting properties of the composition. If employed, calcium-containing component may be present in the binder in a sufficient amount to provide calcium (Ca') ions in an amount of from 1% by weight of the binder, preferably from 2%, more preferably from 3%, still more preferably from 4%, more preferably still from 5% by weight of the binder. The calcium-containing component may be present in the binder in a sufficient amount to provide calcium (Ca) ions in an amount of up to 15% by weight of the binder, preferably up to 12%, more preferably up to 10%, still more preferably up to 8%, more preferably still up to 7%, especially up to 6% by weight of the binder. The calcium-containing component may provide calcium (Cat) ions in an amount of from 2 to 12%, preferably from 3 to 10%, more preferably from 4 to 8%, still more preferably from 5 to 7% by weight of the binder.

Other components that may be included in the binder include other slags, including ferrous, ferroalloy, and non-ferrous slags.

The components of the binder are preferably finely divided, for example by being ground. The average particle size of the binder may be from 5 microns, more preferably from 10 microns, still more preferably from 15 microns, more preferably still from 20 microns, especially from 25 microns, more especially from 30 microns. The average particle size of the binder may be up to 900 microns, more preferably up to 800 microns, still more preferably up to 700 microns, more preferably still up to 600 microns. A preferred average particle size is up to 500 microns, more preferably up to 400 microns, still more preferably up to 300 microns, more preferably still up to 200 microns, especially up to 100 microns. The binder may have an average particle size of from 10 to 800 microns, more preferably from 10 to 500 microns, still more preferably from 15 to 400 microns, more preferably still from 20 to 300 microns, especially from 30 to 200 microns.

The particle size and fineness of the components of the binder is preferably such that at least 5% by weight of the binder has a particle size of from 10 to 100 microns, more preferably from 10 to 80 microns, more preferably at least 7.5%, still more preferably at least 10%, more preferably still at least 12.5%, especially at least 15% by weight. The particle size and fineness of the components of the binder is preferably such that up to 60% by weight of the binder has a particle size of from 10 to 100 microns, more preferably from 10 to 80 microns, more preferably up to 55%, still more preferably up to 50%, more preferably still up to 45%, especially up to 40% by weight. The particle size and fineness of the components of the binder is preferably such that from 5 to 60% by weight of the binder has a particle size of from 10 to 100 microns, more preferably from 10 to 80 microns, more preferably from 7.5 to 55%, still more preferably from 10 to 50%, more preferably still from 12.5 to 45%, especially from 15 to 40% by weight. Preferably, the binder has a particle size distribution such that from 16 to 36.5% by weight of the binder is particles having a size of from 10 to 100 microns, more preferably 10 to 80 microns. The relevant standard for fineness of the binder particles is BS EN 450-1. Preferably, binder meets the requirements of fineness category N of BS EN 450-1.

It is particularly preferred that the fly ash (FA) meets the aforementioned fineness specifications. The granulated blast-furnace slag (GGBS) may have a larger average particle size, for example from 0.01 to 1mm, more preferably from 0.02 to 0.8.mm, still more preferably from 0.03 to 0.7mm, more preferably still from 0.04 to 0.6mm. However, it is preferred for the GGBS also to have a fineness as set out above.

The cemenfifious composition further comprises an activator. The activator 10 comprises: i) a silicate; and ii) a source of chloride (CI-) ions.

The activator comprises a silicate. The silicate employed in the activator may be any suitable silicate. Suitable silicates include silicates of alkali metals and alkaline earth metals. Alkali metal silicates are preferred, in particular, potassium silicates and sodium silicates. Sodium silicates are a preferred group of silicates. Examples of preferred sodium silicates include sodium metasilicate (Na2SiO3), sodium orthosilicate (Na4SiO4), and sodium pyrosilicate (Na6Si207). Sodium metasilicate is one preferred silicate. The silicate may be anhydrous or hydrated, for example sodium silicate pentahydrate (Na2SiO3.5H20) sodium silicate nonahydrate (Na25iO3.9H20). Sodium silicate pentahydrate is another preferred silicate.

The silicate may be present in any suitable amount to activate the binder. In particular, the silicate may be present in an amount of from from 1% by weight of the binder, preferably from 2%, more preferably from 3%, still more preferably from 4%, more preferably still from 5% by weight of the binder, especially from 6%, more especially from 7.5% by weight of the binder. The silicate may be present in an amount of up to 20% by weight of the binder, preferably up to 18%, more preferably up to 16%, still more preferably up to 15%, more preferably still up to 13%, especially up to 12% by weight of the binder. The silicate may be present in an amount of from 2 to 18%, preferably from 3 to 16%, more preferably from 4 to 15%, still more preferably from 5 to 13% by weight of the binder. In one preferred embodiment, the silicate is present in an amount of from 8 to 12%, by weight of the binder, more preferably from 9 to 11% by weight of the binder, especially about 10% by weight of the binder.

The activator further comprises a source of chloride (CV) ions. The chloride (CI-) ions function to activator and accelerate the curing and setting of the composition, once water has been added. Any suitable source of chloride (CI-) ions may be used. Chloride salts are particularly suitable, especially metal chloride salts. Examples of suitable salts include alkali metal chlorides, such as sodium chloride and potassium chloride, and alkaline earth metal chlorides, such as magnesium chloride and calcium chloride. Alkaline earth metal chlorides are preferred for many embodiments, especially calcium chloride.

The source of chloride (CV) ions may be employed in any suitable amount to provide the necessary activation and acceleration activity. The chloride (Cl) ions may be present in the composition in an amount of from 0.1% by weight of the binder, preferably from 0.2% by weight, more preferably from 0.3%, still more preferably from 0.4%, especially from 0.5% by weight of the binder. The amount of chloride (Cl-) provided in the composition will depend upon the end use for the composition. In many applications, it is desirable to have a low concentration of chloride (CI-) ions in the cured cement, mortar or concrete. In such cases, where the end use is sensitive to the chloride (CI-) ion concentration, the chloride (CD ions may be present in the composition in an amount of up to 1.5% by weight of the binder, preferably up to 1.2% by weight, more preferably up to 1%, still more preferably up to 0.9%, especially up to 0.8% by weight of the binder. The chloride (CI-) ions may be present in the composition in an amount of from 0.1 to 1.5% by weight of the binder, preferably from 0.2 to 1.2%, more preferably from 0.3 to 1%, still more preferably from 0.4 to 0.8%, more preferably still from 0.5 to 0.7% by weight of the binder.

In one preferred embodiment, the chloride (CI-) ions are present in the composition in an amount of from 0.6 to 0.7% by weight of the binder. In cases, where the end use is not sensitive to the chloride (CD ion concentration, the chloride (CD ions may be present in the composition in an amount of up to 2% by weight of the binder, preferably up to 1.9% by weight, more preferably up to 1.8%, still more preferably up to 1.7%, especially up to 1.6% by weight of the binder. In such cases, where chloride (CV) ions can be tolerated, the chloride (CD ions may be present in the composition in an amount of from 0.2 to 2% by weight of the binder, preferably from 0.4 to 1.8%, more preferably from 0.5 to 1.5%, still more preferably from 0.6 to 1.4%, more preferably still from 0.7 to 1.2% by weight of the binder. Examples of cases where higher concentrations of chloride (Ct) ions can be tolerated is in the oil and gas sector, for example when the composition is employed in downhole operations, such as downhole cementing.

The cementitious composition of the present invention may further comprise one or more plasticisers or superplasticisers. The plasticisers and superplasticisers reduce the amount of water required to be employed and can improve the consistency of the composition when cured and set. Suitable plasticisers and superplasticisers are known in the art and are commercially available. Examples of suitable plasticisers and superplasticisers include lignosulfonates, sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, acetone formaldehyde condensates and polycarboxylate ethers. An example of a preferred superplasticiser is a blend of polycarboxylate polymers. Commercially available products include Fosroc Auracast 200 and/or Fosroc Auracast 400, Flowaid SCC and Oscreed 893.

The plasticiser or superplasticiser may be employed in any suitable amount. For example, the plasticiser or superplasticiser may be present in the composition in an amount of from 0.1% by weight of the binder, preferably from 0.2%, more preferably from 0.3%, still more preferably from 0.4%, more preferably still from 0.5% by weight of the binder. The plasticiser or superplasticiser may be present in the composition in an amount of up to 2% by weight of the binder, preferably up to 1.8%, more preferably up to 1.5%, still more preferably up to 1.3%, more preferably still up to 1.2% by weight of the binder. The plasticiser or superplasticiser may be present in the composition in an amount of from 0.1 to 2% by weight of the binder, preferably from 0.2 to 1.7%, more preferably from 0.4 to 1.5%, still more preferably from 0.5 to 1.4%, more preferably still from 0.6 to 1.2% by weight of the binder.

The composition may further comprise a strong alkali, to control the setting time of the composition after the addition of water, in particular to accelerate the setting time. Suitable alkalis include the alkali metal hydroxides, in particular potassium hydroxide and sodium hydroxide. The alkali may be present in the composition in an amount of from 0.1% by weight of the binder, preferably from 0.2%, more preferably from 0.3%, still more preferably from 0.4%, more preferably still from 0.5% by weight of the binder. The alkali may be present in the composition in an amount of up to 2% by weight of the binder, preferably up to 1.8%, more preferably up to 1.5%, still more preferably up to 1.3%, more preferably still up to 1.2% by weight of the binder. The alkali may be present in the composition in an amount of from 0.1 to 2% by weight of the binder, preferably from 0.2 to 1.7%, more preferably from 0.4 to 1.5%, still more preferably from 0.5 to 1.4%, more preferably still from 0.6 to 1.2% by weight of the binder.

The inclusion of a strong alkali, such as sodium hydroxide, contributes to the acceleration of the chemical reactions involving the binders. In particular, the alkali reacts with the silicates present in the binders, such as aluminosilicates, as well as the silicate present in the activator, leading to more rapid formation of gels.

The cementitious composition of the present invention may be prepared in a simple manner by combining each of the components in a dry condition to form the dry composition. Each of the components is most preferably employed in the form of a finely divided solid or powder. Suitable techniques for combining and mixing the components are known in the art and suitable equipment for performing this operation is known and commercially available.

It is an advantage of the cementitious composition of the present invention that it can be handled, stored and transported in a dry state, in particular as a dry powder until such times as it is required to be used.

As noted above, when it is required to employ and cure the cementitious composition, the composition is combined with water.

Accordingly, in a further aspect, the present invention provides a cement, mortar, concrete, grout or render prepared from a cementitious composition as hereinbefore described.

Still further, the present invention provides a method for forming a cement, mortar, concrete, grout or render, the method comprising: i) providing a cementitious composition as hereinbefore described; ii) combining the cementitious composition with water; and iii) curing the resulting mixture.

The composition may be combined with water in any suitable manner. For example, the composition and water may be combined in a suitable vessel with simple mixing. The resulting mixture is then allowed to cure and set. This can be carried out at ambient temperature without any heat being provided to the mixture.

Water is provided in sufficient amount to fully hydrate the components of the composition and cause the composition to fully cure and set. Water may be combined with the composition in an amount of from 10% by weight of the binder, preferably from 15%, more preferably from 20%, still more preferably from 25%, more preferably still from 30% by weight of the binder. Water may be combined with the composition in an amount of up to 60% by weight of the binder, preferably up to 55%, more preferably up to 50%, still more preferably up to 45%, more preferably still up to 40% by weight of the binder. Water may be combined with the composition in an amount of from 10 to 60% by weight of the binder, preferably from 15 to 55%, more preferably from 20 to 50%, still more preferably from 25 to 45%, more preferably still from 30 to 40% by weight of the binder.

After the composition has been combined with water, the resulting mixture may be employed, for example as a cement or mortar, a render, a grout, or employed in a concrete.

The cemenfifious composition of the present invention is advantageous in that it is compatible with a wide range of filler materials. The filler materials can be selected to provide the cured composition with a wide range of desirable and advantageous properties, as will now be described in more detail.

In one embodiment, the composition is combined with an aggregate, allowing the composition to be employed as a concrete. Suitable aggregate materials are well known in the art and include all the commercially available aggregate materials in their commercially available grades. Suitable aggregates include sand, fine gravel and course gravel. The range of suitable aggregates will be well known to the person skilled in the art.

When the composition is combined with an aggregate, the aggregate is preferably combined with the composition before or at the same time as the addition of water. It some embodiments is preferred to saturate the aggregate with water, prior to combining the aggregate with the composition.

In another embodiment, the cementitious composition may comprise carbon in one or more forms. The inclusion of carbon in the composition can provide the composition with advantageous properties, for example increased thermal conductivity and increased electrical conductivity. A range of different forms or allotropes of carbon may be employed, for example graphite, graphene, fullerene and nano-carbon structures. In one preferred embodiment, the composition comprises carbon in the form of one or more nano-structures, for example nanotubes, nanobuds and nanoribbons.

The one or more forms of carbon are preferably combined with the composition before the addition of water, preferably when the composition is being formulated from the individual components.

The one or more carbon materials may be present in the composition in any suitable amount to provide the required properties, for example the required thermal or electrical conductivity. The carbon material is preferably present in an amount of from 0.2% by weight of the binder, more preferably from 0.4%, still more preferably from 0.6%, more preferably still from 0.8%, especially from 1%, more especially from 1.2% by weight of the binder. The carbon material may be present in an amount up to 10% by weight, preferably up to 8%, more preferably up to 7%, still more preferably up to 6%, especially up to 5% by weight of the binder. The carbon materials may be present in the composition in an amount of from 0.2 to 10% by weight of the binder, preferably from 0.4 to 8%, more preferably from 0.6 to 7%, still more preferably from 0.8 to 6%, more preferably still from 1 to 5% by weight of the binder.

Including carbon material in the composition may improve a number of properties of the composition when cured. First, the inclusion of carbon materials, such as carbon nanotubes, can increase the strength of the composition. Further, inclusion of the carbon material increases the thermal conductivity and electrical conductivity of the cured material, as noted above. This provides a number of significant advantages.

First, the cured composition can be used in situations where heating is required. Heat can be generated by passing an electrical current through the geopolymer composition. Such situations where heating is required include roads, runways, walkways and footpaths, bridges and the like. Construction components formed from the composition, such as bricks, blocks, slabs, or tiles, such as tiles for walls and flooring, may be used to provide heating in domestic, commercial and industrial applications.

Further, the ability of the composition to conduct and electrical current can be used in a non-destructive method for detecting flaws in poured, cast or moulded components, such as components for buildings and other structures, such as bridges and tunnels. Flaws in the finished component, such as cracks and voids, will become apparent when the electrical conductivity of the bulk material is measured and will be revealed as regions of low or zero conductivity. This method also allows the condition of components made using the composition to be monitored over time, for example to detect degradation of the composition.

The carbon materials may be distributed throughout the bulk of the composition. In an alternative embodiment, components may be formed having a bulk comprising the composition described above and a surface layer formed from the composition further comprising the carbon materials. In this way, the use of carbon materials is confined to the surface layer. The surface layer may be formed together with the bulk of the component, for example by casting or moulding the bulk composition and the surface layer composition together in the same mould. Alternatively, the surface layer may be applied to component, for example using a suitable adhesive.

Other filler materials that may be included in the composition include rubber, for example natural rubber, synthetic rubber, recycled rubber, such as rubber crumb recovered from used vehicle tyres. Elastomers, such as recycled elastomer materials, may also be used as fillers. Other filler materials include plant materials, such as sugar powder waste, natural fibres derived from plants, such as cotton, flax, jute, ramie and hemp. Inorganic fillers may also be used, for example silica, and oxides of aluminium, calcium, titanium, iron and magnesium. Suitable fillers are known in the art and advantageously include materials that are generally considered as waste materials.

In a further aspect, the present invention provides a component or structure formed from a composition as hereinbefore described.

The component may be a structure, such as building or bridge, or a part thereof, a brick, a block, a slab or an installation, such as a road, path, pavement or the like.

Embodiments of the present invention will now be described, for illustration purposes only, by way of the following examples.

Percentages are weight percent, unless otherwise indicated.

Class F FA was obtained from Drax power station, North Yorkshire in the UK. The average particle size of the FA was about 18 pm, with fineness category N according to the BS EN 450-1 specification. The particle density of the FA was around 2210 kg/m3.

Granulated GGBS was obtained from Hanson Cement Group in the UK. The average particle size of the GGBS was about 0.05mm. The relative density of the GGBS was around 2.4 to 3 g/cm3.

The chemical compositions of the FA and GGBS are summarised in Table 1, which were determined using x-ray fluorescence analysis.

Table 1

Component FA (wt%) GGBS (wt%) Si02 55.7 28.2 A1203 27.8 9.73 Fe203 7.27 0.98 Ca0 4.10 52.69 TiO2 2.29 1.01 503 0.27 1.46 K20 1.55 1.22 MgO 2.9 MnO - 0.74 LOI 3.04 3.76 Others 1.018 1.05

EXAMPLES Example 1

A cementitious composition was prepared from the components summarised in Table 2 below.

Table 2

Binder Pulverised Fly Ash (PFA) 315kg Ground Granulated Blast-Furnace Slag (GGBS) 135kg Activator Sodium Metasilicate 45kg Weight ratio of Sodium Metasilicate to Binder 0.1 Calcium Chloride 4.5kg Weight ratio of Calcium Chloride to Binder 0.01 Sodium Hydroxide 4.5kg Weight ratio of Sodium Hydroxide to Binder 0.01 The composition was prepared by combining all the components as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained.

Example 2

A cementitious composition was prepared from the components summarised in Table 3 below.

Table 3

Binder Pulverised Fly Ash (PFA) 225kg Ground Granulated Blast-Furnace Slag (GGBS) 225kg Activator Sodium Metasilicate 45kg Weight ratio of Sodium Metasilicate to Binder 0.1 Calcium Chloride 4.5kg Weight ratio of Calcium Chloride to Binder 0.01 The composition was prepared by combining all the components as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained

Example 3

A cementitious composition was prepared from the components summarised in Table 4 below.

Table 4

Binder Pulverised Fly Ash (PFA) 225kg Ground Granulated Blast-Furnace Slag (GGBS) 225kg Activator Sodium Metasilicate 45kg Weight ratio of Sodium Metasilicate to Binder 0.1 Calcium Chloride 4.5kg Weight ratio of Calcium Chloride to Binder 0.01 Sodium Hydroxide 4.5kg Weight ratio of Sodium Hydroxide to Binder 0.01 The composition was prepared by combining all the components as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained.

Example 4

A cementitious composition was prepared from the components summarised in Table 5 below.

Table 5

Binder Pulverised Fly Ash (PFA) 225kg Ground Granulated Blast-Furnace Slag (GGBS) 225kg Calcium Hydroxide 49.5kg Weight ratio of Calcium Hydroxide to (PFA +GGBS) 0.11 Activator Sodium Metasilicate 45kg Weight ratio of Sodium Metasilicate to (PFA +GGBS) 0.1 Calcium Chloride 4.5kg Weight ratio of Calcium Chloride to (PFA +GGBS) 0.01 Superplasticiser (Fosroc Auracast 200) 4.5kg The composition was prepared by combining all the components as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained.

Example 5

Each of the cementitious compositions of Examples 1 to 4 was combined with 162kg of water (ratio of water to PFA + GGBS of 0.36) and the resulting mixture stirred to form a paste. The resulting paste was divided into samples and each sample was allowed to cure at 15°C (+/-2°C) under. water.

The compressive strength of the samples was measured using the procedures set out in British Standard EN 12390-3 after 7 days and 28 days. The results of the measurements are summarised in Table 6 below.

Table 6

Example No. Compressive Strength Compressive Strength after 7 days after 28 days (MPa) (MPa) 1 9.78 14.29 2 22.52 27.35 3 22.36 29.05 4 6.66 12.62 Example 6-Concrete Composition A concrete composition was prepared from the components summarised in Table 7 below:

Table 7

Binder Pulverised Fly Ash (PFA) 184.5kg Ground Granulated Blast-furnace Slag (GGBS) 184.5kg Activator Sodium Metasilicate 41kg Calcium Chloride 4.1kg Aggregate Fine Aggregate 764kg Coarse Aggregate 1153kg Particle Size of Coarse Aggregate -20mm 692kg (60%) Particle Size of Coarse Aggregate -10mm 461kg (40%) Superplasticiser (Fosroc Auracast 200) 4.1kg Water 155kg The components, with the exception of water, were combined as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained.

Water was then added to the dry mixture with stirring to produce a uniform concrete composition.

Example 7 -Concrete Composition A concrete composition was prepared from the components summarised in Table 8 below:

Table 8

Binder Pulverised Fly Ash (PFA) 157.5kg Ground Granulated Blast-furnace Slag (GGBS) 157.5kg Activator Sodium Metasilicate 35kg Calcium Chloride 4.1kg Aggregate Fine Aggregate 815kg Coarse Aggregate 1142kg Particle Size of Coarse Aggregate -20mm 686kg (60%) Particle Size of Coarse Aggregate -10mm 457kg (40%) Superplasticiser (Fosroc Auracast 200) 3.5kg Water 147kg The components, with the exception of water, were combined as dry, finely divided or powdered solids and mixing until a visibly homogeneous dry mixture was obtained.

Water was then added to the dry mixture with stirring to produce a uniform concrete cornposition.

Example 8-Concrete Composition -Strength Tests The concrete compositions of Examples 6 and 7 were separated into samples and all samples were allowed to cure at 15°C (+/-2°C) under water.

The compressive strength of the samples was measured using the procedures set out in British Standard EN 12390-3 after 3, 7, 14, 28, 56 and 91 days. The results of the measurements are summarised in Table 9 below.

Table 9

Compressive Strength (MPa) Example No. 3 days 7 days 14 days 28 days 56 days 91 days 7 20.31 36.25 46.84 57.00 57.08 59.0 8 7.70 18.86 24.6 37.34 38.61 39.0

Example 9

A cementitious composition was prepared from the components summarised in Table 10 below:

Table 10

Binder Pulverised Fly Ash (PFA) 225kg Ground Granulated Blast-Furnace Slag (GGBS) 225kg Activator Sodium Metasilicate 45kg Weight ratio of Sodium Metasilicate to Binder 0.1 Calcium Chloride 4.5kg Weight ratio of Calcium Chloride to Binder 0.01 The cemenfifious composition was divided into 2 samples. Each sample was combined with dry sand at the weight ratios indicated in Table 11 below. Each of the resulting mixture was combined with water in a weight ratio of water to binder of 0.36 and the samples allowed to cure.

The compressive strength of each cured sample was determined using the procedures set out in British Standard EN 12390-3 at 3, 7 and 28 days. The flexural strength of each cured sample was determined using the procedures set out in British Standard EN 12390-5 at 3, 7 and 28 days. The results are summarised in Table 11 below.

Table 11

Compressive Strength (MPa) Flexural Strength (MPa) Weight ratio of cementitious composition and sand 1:3 3 days 12.0 2.5 7 days 13.8 3.8 28 days 16.0 5.3 Weight ratio of cementitious composition and sand 1:4 3 days 9.6 3.0 7 days 13.7 3.7 28 days 15.8 5.5 The data presented in the tables above, show that the cementitious composition of the present invention can be formulated to produce a range of different cement, concrete and mortar grades with various strengths. Compressive strengths of 60 MPa may be achieved with high strength concrete grades. Alternatively, lower strength grades can be produced, for example for use as mortar for masonry.

Claims

CLAIMS1. A dry cementitious composition comprising: a binder comprising ground granulated blast-furnace slag (GGBS), fly ash (FA) or a mixture thereof; and an activator comprising: a silicate; and a source of chloride (Cl-) ions.
2. The composition according to claim 1, wherein the composition has a loss on ignition (L01) of less than or equal to 7% by weight.
3. The composition according to either of claims 1 or 2, wherein the binder comprises both ground granulated blast-furnace slag (GGBS) and fly ash (FA).
4. The composition according to any preceding claim, wherein ground granulated blast-furnace slag (GGBS) is present in the composition in an amount of from 5 to 75% by weight of the binder.
5. The composition according to any preceding claim, wherein fly ash (FA) is present in the composition in an amount of from 10 to 90% by weight of the binder.
6. The composition according to any preceding claim, wherein the binder comprises both ground granulated blast-furnace slag (GGBS) and fly ash (FA), wherein the weight ratio of fly ash to ground granulated blast-furnace slag is 0.25 to 4.
7. The composition according to any preceding claim, wherein the binder further comprises a source of calcium (Ca++) ions.
8. The composition according to claim 7, wherein the binder comprises calcium hydroxide.
9. The composition according to either of claims 7 or 8, wherein the source of calcium ions provides (Ca++) ions is present in an amount of 2 to 12% by weight of the binder.
10. The composition according to any preceding claim, wherein the binder has a particle size distribution such that 16 to 36.5% by weight of the binder is particles having a size of from 10 to 100 microns.
11. The composition according to any preceding claim, wherein the silicate comprises a silicate of an alkali metal or an alkaline earth metal or a mixture thereof.
12. The composition according to claim 11, wherein the silicate is selected from sodium metasilicate (Na2SiO3), sodium orthosilicate (Na43iO4), sodium pyrosilicate (Na63i207) and mixtures thereof.
13. The composition according to any preceding claim, wherein the composition comprises the silicate in an amount of from 2 to 18% by weight of the binder.
14. The composition according to any preceding claim, wherein the source of chloride (Cl-) ions comprises a chloride of an alkali metal or an alkaline earth metal.
15. The composition according to claim 14, wherein the source of chloride (Cl-) ions comprises calcium chloride.
16. The composition according to any preceding claim, wherein the chloride (Cl-) ions are present in the composition in an amount of from 0.2 to 2% by weight of the binder.
17. The composition according to any preceding claim, wherein the composition further comprise one or more plasticisers or superplasficisers.
18. The composition according to claim 17, wherein the composition comprises a superplasticiser, wherein the superplasticiser is a blend of polycarboxylate polymers.
19. The composition according to either of claims 17 or 18, wherein the plasticiser and/or the superplasticiser is present in the composition in an amount of from 0.1 to 2% by weight of the binder.
20. The composition according to any preceding claim, further comprising an alkali metal hydroxide.
21. The composition according to claim 20, wherein the alkali metal hydroxide is present in an amount of from 0.1 to 2% by weight of the binder.
22. A cement, mortar, concrete, grout or render prepared from a cementitious composition according to any preceding claim.
23. A method for forming a cement, mortar, concrete, grout or render, the method comprising: i) providing a cementitious composition according to any of claims 1 to 21; ii) combining the cementitious composition with water; and iii) curing the resulting mixture.
24. The method according to claim 23, wherein in step (ii) water is combined with the composition in an amount of from 10 to 60% by weight of the binder.
25. A component or structure prepared from a composition according to any of claims 1 to 21 or a cement, mortar, concrete, grout or render according to claim 22.