JP7296135B2 - Controlling curing time of geopolymer compositions containing high CA reactive aluminosilicate materials - Google Patents

Description

The disclosed invention relates generally to admixtures for geopolymer compositions. More specifically, the present invention relates to retarding admixtures for effectively controlling curing in geopolymer compositions and geopolymer systems that can be used in certain applications.

In general, geopolymers made with certain reactive high-Ca aluminosilicates set and harden very quickly due to the instantaneous formation of calcium silicate hydrates and calcium aluminosilicate hydrate gels. become. In engineering practice, geopolymer cure times should be fairly long. This means that concrete or mortar made using pozzolanic binders require sufficiently long curing times to allow transport and placement.

However, if the curing time is too long, it becomes uneconomical. Thus, improved proper control of cure time through the use of cure retarders is critical to the successful application of geopolymer materials in the construction and construction industry.

(Outline of invention)
According to a first broad embodiment, the present disclosure has a controllable cure time comprising at least one reactive aluminosilicate, at least one retarder, and at least one alkali silicate activator solution. A geopolymer composition is provided.
According to a second broad embodiment, the present disclosure provides a controllable cure comprising combining at least one reactive aluminosilicate, at least one retarder and at least one alkali silicate activator solution. A method of making a geopolymer composition with time is provided.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the general description given above and the detailed description given below, illustrate the invention. It serves to explain the characteristics.

4 shows a Raman spectrum of a sodium silicate activator solution containing 0% to 5% barium chloride monohydrate BWOB, according to one embodiment of the present disclosure;

FIG. 2 shows Raman spectra of a co-precipitated silicate material comprising 0.5%, 0.75, 0.875 and 1.0% barium chloride monohydrate BWOB, according to one embodiment of the present disclosure; FIG.

DEFINITIONS Where the definition of terms departs from the commonly used meaning of the term, applicant intends to utilize the definitions provided below unless otherwise indicated.

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of any subject matter claimed. In this application, the use of the singular includes the plural unless specifically stated otherwise. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that In this application, the use of "or" means "and/or" unless stated otherwise. Furthermore, use of the term "including" as well as other forms such as "includes", "includes" and "included" is not limiting.

For purposes of this disclosure, the terms "comprising," "having," "including," and variations of these words are open-ended. , means that there may be additional elements other than the listed elements.

For purposes of this disclosure, "top", "bottom", "upper", "lower", "above", "below", "left ),” “right,” “horizontal,” “vertical,” “up,” “down,” etc. It is used only for convenience in describing various embodiments. Embodiments of the present disclosure can be oriented in various ways. For example, figures, devices, etc. shown in the drawings could be flipped over, rotated 90 degrees in any direction, or flipped.

For the purposes of this disclosure, a value or property is defined as the value of a particular value, property, or condition when that value is derived by performing a mathematical calculation or logical decision using that value, property, or other factor. It is "based" on satisfaction, or other factors.

It is noted that in order to provide a more concise description of the present disclosure, some of the quantitative expressions given herein are not qualified with the term "about." All quantities given herein are meant to refer to the actual given value, regardless of whether the term "about" is explicitly used, and for such given value It is also meant to refer to approximations to a given value as reasonably inferred based on ordinary skill in the art, including approximations due to experimental and/or measurement conditions.

For purposes of this disclosure, the term "actual temperature" refers to the actual temperature of air at any particular location as measured by a thermometer.

For the purposes of this disclosure, the term "BWOB" is commonly recognized as the amount (percentage) of material added to cement when the material is added based on the total amount of a particular binder or blend of binders. "by weight of binder". In the case of geopolymer materials, the binder is typically a pozzolanic material called a pozzolanic precursor that can be activated with an alkaline solution.

For the purposes of this disclosure, the term "cement" refers to a binder, a substance used in construction that hardens, hardens, and adheres other materials together. Cement is rarely used alone and can be used to bind sand and gravel (aggregate). Cement mixed with fine aggregate produces mortar for masonry or mixed with sand and gravel to produce concrete. Cement used in construction is usually inorganic, often lime or calcium silicate based, and can be characterized as hydraulic or non-hydraulic depending on the ability of the cement to hydrate in the presence of water. can.

For the purposes of this disclosure, the term “concrete” refers to a stone-like mass that can be spread or poured into a mold and, when hardened, is made from a mixture of broken stone or gravel, sand, cementitious materials, and water. Refers to heavy, rough building materials that form Some embodiments may include composite materials composed of fine and coarse aggregates bonded together with a flowable cement (cement paste) that hardens over time. Most often Portland cement can be used, but sometimes other hydraulic cements such as calcium aluminate cement can be used. Geopolymers are considered to be a new type of cement material that does not contain Portland cement.

For the purposes of this disclosure, the term "geopolymer" refers to a sustainable cement binder system that is Portland cement free. In a narrow sense, the geopolymers of the disclosed invention relate to inorganic polymers that have a three-dimensional network structure similar to organic thermoset polymers. The backbone matrix of the disclosed geopolymer is _an X-ray amorphous analogue of the zeolite framework, characterized by tetrahedral coordination of Si and Al atoms connected by oxygen bridges, ^with with an associated alkali metal cation (usually Na ⁺ and/or K ⁺ ) as a charge balancer. The geopolymers of the disclosed invention are composed of alkali aluminosilicate and/or alkali alkaline earth aluminosilicate phases as a result of the reaction of a solid aluminosilicate powder (term, pozzolanic precursor) and an alkali activator. It may be viewed more broadly as a class of Alkali Activated Materials (AAM).

For the purposes of this disclosure, the term "geopolymer composition" refers to a mixed ratio of pozzolanic precursors and alkaline activators in solid or liquid form. Additionally, the geopolymer composition may further comprise fine and coarse aggregates, fibers and other mixtures depending on the application.

For the purposes of this disclosure, the term "mortar" is used to join building blocks such as stone, brick, and concrete blocks, to fill and seal irregular gaps between them, and sometimes to add decorative colors and textures in masonry walls. Refers to a workable paste containing fine aggregates used to add patterns. In its broadest sense, mortar includes pitch, asphalt, and soft muds or clays such as those used between mud bricks. As cement or geopolymer mortar hardens, it hardens into a rigid structure.

For the purposes of this disclosure, the term “room temperature” refers to temperatures between about 15° C. (59° F.) and 25° C. (77° F.).

For the purposes of this disclosure, the term "setting" refers to the transformation from a plastic paste to a non-plastic rigid body.

For the purposes of this disclosure, the term "set time" or "setting time" refers to the time from the moment water (alkaline activator solution) is added to the cement (pozzolanic precursor) until the paste refers to the elapsed time until it begins to lose its plasticity (initial hardening). The final hardening time is from the moment water (alkaline activator solution) is added to the cement (pozzolanic precursor), when the paste has completely lost its plasticity and reached a hardness sufficient to withstand a certain pressure. It is time to

For the purposes of this disclosure, the term "sparingly water soluble" refers to substances with a solubility of 0.1 g/100 ml water to 1 g/100 ml water. Unless otherwise stated, the terms "sparingly soluble" and "sparingly water soluble" are used interchangeably in the following description of the invention to refer to substances that are sparingly soluble in water.

For the purposes of this disclosure, the term "water-insoluble" refers to substances that have a solubility of less than 0.1 g in 100 ml of water.

DESCRIPTION While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. The invention is not intended, however, to be limited to the particular forms disclosed, but on the contrary the invention covers all modifications, equivalents and alternatives falling within the spirit and scope of the invention. It should be understood that

溶解すると、これらの種は水相の一部、すなわちすでにシリケートを含む活性化溶液になる。これにより、シリケート、アルミン酸塩及びアルミノケイ酸塩種の複合混合物が形成される。水相の種が重縮合によって大きなネットワークを形成するため、溶液はますます濃縮され、その結果アルカリアルミノケイ酸塩ゲル（ＡＡＳ）が形成される：

ゲル化後、ゲルネットワークの接続性が増加するため、この系は再構成と再編成を続け、その後の硬化プロセス中に硬化して固まる３次元アルミノケイ酸塩ネットワークをもたらす。 Geopolymers are a class of alkali-activated binders that have a three-dimensional network structure similar to that of organic thermoset polymers. The geopolymer backbone matrix is the X-ray amorphous analogue of the zeolite framework, characterized by tetrahedral coordination of Si and Al atoms connected by oxygen bridges, acting as a charge balancer for _AlO4- ^. With associated alkali metal cations (usually Na ⁺ and/or K ⁺ ). Nominally, the empirical formula of a geopolymer can be expressed as _Mn [-( _SiO2 ) _z - _AlO2 ] _nWH2O , where M represents an alkali _cation and z is the Denotes a molar ratio (1, 2 or 3), where n represents the degree of polycondensation. Dissolution of reactive low-Ca aluminosilicate sources by alkaline hydrolysis consumes water and produces aluminate and silicate species. This first step of geopolymerization is controlled by the ability of alkaline compounds to dissolve fly ash glass networks and generate small reactive species of silicates and aluminates:

Upon dissolution, these species become part of the aqueous phase, ie the activated solution already containing silicates. This forms a complex mixture of silicate, aluminate and aluminosilicate species. As species in the aqueous phase form a large network through polycondensation, the solution becomes increasingly concentrated, resulting in the formation of an alkali aluminosilicate gel (AAS):

After gelation, the system continues to rearrange and rearrange as the connectivity of the gel network increases, resulting in a three-dimensional aluminosilicate network that hardens and hardens during the subsequent curing process.

Examples of these low Ca reactive aluminosilicates include metakaolin (MK), certain calcined zeolites, and low Ca class F fly ash (low Ca FFA).

Metakaolin is an amorphous aluminosilicate pozzolanic material whose use dates back to 1962 when it was incorporated into the concrete of Jupiadam, Brazil. is a heat-activated aluminosilicate material with high pozzolanic activity comparable to, or less than, that of fumed silica. Metakaolin is produced by calcining kaolinite clay at 650° C. to 800° C., depending on the purity and crystallinity of the precursor clay. Alkaline activation of metakaolin produces a typical AAS gel composition that cures and hardens at ambient temperature. The mechanical properties and microstructure of geopolymers strongly depend on the initial Si/Al molar ratio. Better strength properties have been reported for mixtures with M ₂ O/Al ₂ O ₃ molar ratios of about 1 and SiO ₂ /Al ₂ O ₃ ratios ranging from 3.0 to 3.8.

Fly ash is a fine, powdery material that "sprays" out of coal combustion chambers (boilers) and is captured by emission control systems and scrubbers, such as electrostatic precipitators and fibrous filter "baghouses." About 131 million tons of fly ash are produced annually, of which about 56 million tons of fly ash are recycled. Worldwide, approximately 65% of fly ash produced is disposed of in landfills or ash ponds. Combustion of anthracite and bituminous coal typically produces class F fly ash with less than 8% CaO. Fly ash is mainly composed of glassy spherical particles. The American Society for Testing and Materials (ASTM) C618 standard recognizes two major classes of fly ash, Class C and Class F. The lower limit of (SiO ₂ +Al ₂ O ₃ +Fe ₂ O ₃ ) for class F fly ash (FFA) is 70% and for class C fly ash (CFA) is 50%. A high content of calcium oxide results in a Class C fly ash with cementitious properties that, when mixed with water, lead to the formation of calcium silicate and calcium aluminate hydrates without the need for alkali activation. US Pat. No. 5,435,843 discloses an alkali-activated Class C fly ash composition in which the cement has an initial hardening time of less than about 5 minutes. Class F fly ash generally has a maximum calcium oxide content of about 18 wt%, while Class C fly ash generally has a higher calcium oxide content, such as 20-40 wt%. Low Ca FFAs typically contain less than 8 wt% CaO. Low-Ca FFA-based geopolymers are typically very slow to cure and harden, with low ultimate strength when cured at ambient (e.g., room temperature) temperatures, but their reactivity increases with increasing curing temperature. do. Alkali activation of low-Ca FFAs requires high temperature curing to produce useful construction materials. Alternatively, a more reactive aluminosilicate material such as fine blast furnace slag (BFS) powder or metakaolin must be blended to produce a geopolymer product that cures and hardens at ambient temperatures. .

Ground granulated blast furnace slag is another type of reactive aluminosilicate material rich in alkaline earth oxides such as CaO and MgO. Ground granulated blast furnace slag is a glassy granular material that varies from popcorn-like, crumbly, coarse structures to dense, sand-sized particles with diameters greater than 4.75 mm. Grinding reduces the particle size to cement fineness and can be used as a supplemental cementitious material in Portland cement-based concrete. Blast furnace slag is essentially calcium aluminosilicate glass, typically 27-38 wt% _SiO2 , 7-12 wt% _Al2O3 , _34-43 wt% CaO, 7-15 wt%. MgO, 0.2-1.6 wt% Fe ₂ O ₃ , 0.15-0.76 wt% MnO and 1.0-1.9 wt%. Blast furnace slag is commonly classified into three grades, 80, 100 and 120, according to ASTM C989-92. Moreover, ultra-fine blast furnace slag is more reactive compared to BFS 120. For example, MC-500® Microfine® cement (de Neef Construction Chemicals) is an ultra-fine pulverized coal with a particle size of less than about 10 μm and a specific surface area of about 800 m ² /kg. Since BFS is nearly 100% vitreous, it is generally more reactive than most fly ash. Alkaline activation of BFS essentially produces calcium silicate hydrate (CSH) and calcium aluminosilicate (CASH) gels. Geopolymers produced by alkali activation of BFS typically cure and harden very rapidly even at ambient temperatures, resulting in much higher ultimate strength than geopolymers produced with low-Ca Class F fly ash. can get. Some compositions have an initial cure time of less than 60 minutes, making them difficult to mix, place and finish. Alkali-activated slag has been found to have several superior properties compared to Portland cement concrete, such as low heat of hydration, high early strength and excellent durability in aggressive environments. ¹ A survey of the published literature showed that this binder system had some serious problems such as rapid curing and high drying shrinkage. ^{A few} of these issues must be resolved before it can be used in commercial activities.

Recently, the use of lignite and sub-bituminous coal has increased significantly, and a significant percentage of US coal reserves produce fly ash containing significant amounts of CaO. Fly ash containing high CaO content (high Ca FFA), eg, greater than 8 wt% and less than 20 wt%, may still be classified as Type F by ASTM C-618. Cure time of fly ash-based geopolymers decreases exponentially with increasing CaO content, but compressive strength increases with increasing CaO. ⁴ According to the disclosed embodiments, it was found that fast curing can occur with fresh geopolymers made with high Ca FFA containing 12.2 wt% CaO. Geopolymers made with CFA with more than 20% CaO typically cure within 36 minutes, and fast cures, eg, minutes, are very common. ⁵ Clearly, geopolymers made with high Ca FFAs (eg >8% CaO) and CFAs require adequate cure control to produce useful construction materials. Alkaline activation of ^6- high Ca FFAs produces hydrated products such as CSH and CASH along with alkali aluminosilicate gels. The curing time of the geopolymer depends on the properties of the alkaline activator solution, such as alkali molarity, _SiO2 / _M2O (M=Na, K) molar ratio, binder to water ratio (w/b). . For example, curing time decreases with increasing alkali hydroxide molar concentration and SiO ₂ /M ₂ O (M=Na, K) molar ratio, but increases with increasing w/b. Conversely, the compressive strength of the consolidated geopolymer increases with increasing alkali hydroxide molar concentration and SiO ₂ /M ₂ O (M=Na, K) molar ratio.

Class C fly ash has some similarities to blast furnace slag. Both are calcium aluminosilicate glasses. These pozzolanic materials are called reactive alkaline earth aluminosilicates or high Ca reactive aluminosilicates. In addition to BFS and CFA, high Ca FFA, vitreous calcium silicate (VCAS), and clinker kiln dust (CKD) fall into this category. VCAS is a waste product associated with glass fiber manufacturing. In a typical fiberglass manufacturing facility, typically about 10-20% by weight of the processed glass material is not converted into final product and is excluded as a by-product or waste VCAS and sent to landfill. VCAS is 100% amorphous and its composition is very consistent, primarily about 50-55 wt% SiO ₂ , 15-20 wt% Al ₂ O ₃ , and 20-25 wt%. of CaO. Ground VCAS exhibits pozzolanic activity comparable to silica fume and metakaolin when tested according to ASTM C618 and C1240. CKD is a by-product of Portland cement manufacturing and is an industrial waste. Over 30 million tons of CKD are produced annually worldwide, a significant amount of which ends up in landfills. A typical CKD is about 38-64 wt% CaO, 9-16 wt% SiO ₂ , 2.6-6.0 wt% Al ₂ O ₃ , 1.0-4.0 wt% Fe ₂ O ₃ , 0 0-3.2 wt % MgO, 2.4-13 wt % K ₂ O, 0.0-2.0 wt % Na ₂ O, 1.6-18 wt % SO ₃ , 0.0-5. It contains 3 wt% Cl 2 ⁻ and has a 5.0-25 wt% LOI. CKD is generally a very fine powder (eg, specific surface area of about 4600-14000 cm ² /g). During alkaline activation, CSH gel, ettringite (3CaO.Al ₂ O 3.3CaSO _{4.32H 2} O) and/or syngenite (alkali-calcium sulfate mixture ₎ will be further formed.

In general, geopolymers made by alkali activation of these reactive high-Ca aluminosilicates set very quickly due to the instantaneous formation of calcium silicate hydrates and calcium aluminosilicate hydrate gels. , hardens. In engineering practice, geopolymer cure times should be fairly long. This means that concrete or mortar made using pozzolanic binders require sufficiently long curing times to allow transport and placement. However, if the curing time is too long, it becomes uneconomical. According to disclosed embodiments, proper control of set time by using set retarders is very important for effective application of geopolymer materials in the construction and construction industry.

Control of cure time can be achieved by properly formulating the activator solution composition for high Ca aluminosilicate-based geopolymers. For example, a high w/b and low concentration of alkali silicate may result in a geopolymer paste with sufficient long cure times and workability. However, the performance of the cured product is usually greatly affected, with significant loss of strength and large drying shrinkage to be expected. Various types of mixtures have been used in recent years to retard the setting of alkali-activated cements or geopolymers, but their retarding efficiencies vary widely. ³ U.S. Pat. No. 5,366,547 discloses a method of retarding the setting time of sodium hydroxide activated blast furnace slag using a phosphoric acid additive. Examples of phosphate retarders include sodium metaphosphate, sodium polyphosphate, potassium metaphosphate, and potassium polyphosphate. The retarding effect of these phosphate additives can change when sodium silicate solutions are used to activate BFS or other types of Ca-rich aluminosilicates. Kalina et ^al.7 used Na ₃ PO ₄ to retard the hardening of sodium silicate activated blast furnace slag. Solid sodium phosphate was blended with BFS and then mixed with the sodium silicate activator solution. Compressive strength was significantly affected (decreased) when a high dose of retarder was applied to achieve a long set or workable time. Chang ⁸ and Chang et al. ⁹ concluded that the use of phosphoric acid alone prolongs the hardening time of alkali-activated slags after reaching a critical concentration, but reduces the compressive strength at early age. Ca ²⁺ ions released during dissolution of blast furnace slag in highly alkaline solutions were estimated to be bound to phosphate anions from retarders. Calcium dihydrogen, with subsequent formation of the hydrogen phosphate structure, results in a shortage of calcium ions in solution, which hinders the nucleation and growth of CSH and CASH. Therefore, the initial hardening time is lengthened.

The efficiency of certain retarders commonly used in Portland cement varies with geopolymer. Most retarding admixtures that are effective in Portland cement may not work in highly alkaline geopolymer systems. Wu et ^al.10 observed that potassium tartrate or sodium tartrate had no effect on the initial setting time of the alkali-activated slag, but slightly shortened the final setting time. Rathanasak et al ^{. 11} found that sucrose and gypsum, which worked well in Portland cement, did not extend setting time for sodium silicate-activated high-Ca FFAs. Brought et ^al.12 investigated the retarding effect of NaCl on the setting time of sodium silicate activated slag systems. Addition of NaCl at high doses significantly retarded both hardening and strength development, whereas at low doses, ie, 4 wt% or less of the slag, NaCl acted as an accelerator. In another sodium silicate-activated slag system, ¹³ little effect of NaCl on curing time was observed with additions up to 20% by weight of binder (BWOB) above which retarded curing. However, the addition of such large amounts of chloride to reinforced geopolymer concrete can greatly accelerate corrosion of rebar, resulting in reduced service life.

The use of borate as a retarder for Portland cement is also very well known. However, Nicholson et ^al.14 found that borate added to alkali-activated fly ash (Class C) had no effect on hardening behavior and, on the contrary, binder strength was adversely affected by large amounts of borate. reported. US Pat. No. 4,997,484 discloses alkali hydroxide activated Class C fly ash geopolymer compositions (free of soluble silicates). The geopolymer composition, which uses borax as a retarder, exhibits rapid strength build-up, such as 1800-4000 psi, after curing at 73 degrees Fahrenheit for 3-4 hours. Boron retarders were not effective in retarding the cure of alkali-activated CFA geopolymers. Both US Pat. No. 7,794,537 and US Pat. No. 7,846,250 disclose certain chemical compounds as known retarders for Portland cement and geopolymers. Geopolymer compositions are MK or FFA based for oilfield applications or carbon dioxide storage. These compounds retard the thickening of well cementing grouts at high temperatures such as 85° C. and include borax (Na ₂ B ₄ O _{7.10H 2} O), boric acid, sodium phosphate, and lignosulfonates. is included.

US Patent Application No. 2011/0284223 discloses compositions and methods for wellbore cementing applications that use organic compounds to retard thickening of geopolymer systems at elevated temperatures. Geopolymer compositions are not new and have been disclosed in the prior art and extensively studied in the literature. Preferred compounds as retarders include aminated polymers, amine phosphonates, quaternary ammonium compounds and tertiary amines. Although the geopolymer composition itself is not unique, the impact of these retarders on cure properties such as compressive strength has not been previously developed/communicated.

Chinese Patent No. 102249594B discloses a composite retarder for retarding the hardening time of alkali-activated blast furnace slag. Complex retarders are composed of sodium chromate, heterocyclic amino acids and silicone surfactants. Chinese Patent No. 1118438C discloses a composite retarder consisting of potassium chromate, sugar and phenol for sodium silicate activated slag. Initial cure can be adjusted between 1 hour and 70 hours. However, retarders can be undesirable because chromates are highly mobile, easily mobile, and toxic anionic species that pose a risk of contaminating the environment. Chinese Patent Application No. 101723607A discloses a soluble zinc salt for retarding the hardening time of sodium silicate activated blast furnace slag. These zinc salts include nitrates, sulfates and chlorides. Chinese patent applications Nos. 1699251A and 100340517C disclose barium salts as retarders for alkali-activated carbonite/blast furnace slag. Either a zinc salt or a barium salt is dissolved in water and added to the blast furnace slag. An alkaline activator solution is then added to the mixture. Alternatively, salt powder is ground with blast furnace slag. The active agent solution is then mixed with the solid blend.

Unfortunately, most retarders of the prior art were developed only for alkali activated slag. It is well known that the efficiency of retarders is highly dependent on binder composition. Retarders that are effective in Portland cement and alkali-activated slag do not always work well in geopolymer systems such as those made from high Ca FFA, CFA, or low Ca FFA and BFS blends.

The methods disclosed in the prior art mainly employ two important mechanisms to retard the hardening time of alkali-activated slag. Retardants are added to chelate and/or precipitate released Ca ²⁺ and prevent Ca ²⁺ from reacting with silicate species already present in the alkaline activator solution. Alternatively, retarders are added to form a protective layer directly bonded to the surface of the anhydrous blast furnace slag particles, thereby reducing their ability to dissolve in highly alkaline solutions. These adherent layers can be either adsorbed species or insoluble calcium salts that precipitate and adhere to the surface. This method is referred to herein as a "protective layer". Chinese Patent No. 102249594B discloses that when a silicone surfactant is adsorbed on the surface of blast furnace slag particles and a charger is introduced, a resulting repulsive force is generated to reduce the migration rate of Ca ²⁺ and/or silicic acid It is disclosed to reduce the electrostatic attraction of anions, thereby preventing CSH gel formation. Ca ²⁺ cations released during melting of blast furnace slag in a highly alkaline environment bind to phosphate anions from phosphate retarders such as Na ₃ PO ₄ . Formation of insoluble calcium phosphate compounds reduces available Ca ²⁺ , inhibits nucleation and growth of the CSH phase, and prolongs hardening time. ⁷ A boron compound dissolved in an alkaline solution forms tetrahydroxyborate, which reacts with Ca ²⁺ . Precipitated calcium borate (such as Ca(B[OH] ₄ ) ₂ H ₂ O) partially or completely covers the surface of blast furnace slag particles. The presence of such an impermeable calcium borate layer therefore prevents further dissolution of the blast furnace slag particles in the alkaline solution. ¹⁵ Soluble zinc salts are converted to a calcium zincate phase (e.g., _CaZn2 (OH) _6.H2O ), which partially or completely covers the blast furnace slag particles, thus making them susceptible to further hydration or alkali activation. Passivate them. ^16,17 US Patent Application No. 20160060170 discloses geopolymer compositions containing nanoparticle retarders to control curing time. Reactive aluminosilicates include metakaolin, fly ash or rice hull ash. Reactive aluminosilicate particles are coated with nanoparticles, such as halloysite nanotubes and kaolin nanoclay particles, prior to mixing with the sodium silicate activator solution. The nanoparticle coating is to retard the geopolymerization reaction. The barium salt solution is premixed with the blast furnace slag/carbonatite powder. Since the surface of blast furnace slag particles is negatively charged in water, Ba ²⁺ cations tend to adsorb to the surface of the slag particles. When exposed to an alkaline silicate solution, insoluble barium precipitates form a thin film on the slag particles, preventing the slag from coming into contact with the alkaline solution (Chinese Patent Application No. 1699251A).

If the formation of a protective layer on the surface of the pozzolan particles is used to delay the curing time of the alkali-activated material, a metal such as barium nitrate is added prior to mixing with the alkali silicate solution to improve the coverage of the protective coating. A salt solution must be mixed with the pozzolanic particles.

The disclosed embodiments provide a new method of using metal salts to retard the curing time of alkali-activated materials or geopolymers. Rapid curing of alkali-activated high Ca-reactive aluminosilicates is associated with the formation of CSH and/or CASH gels upon premature curing. Ca ²⁺ cations are released during dissolution of high Ca-reactive aluminosilicate particles and the cations react almost instantaneously with silicate anions present in the alkaline solution. Curing control can be achieved by prior art methods, for example, through removal of Ca ²⁺ ions in alkaline solutions and/or formation of a protective layer on the surface of the pozzolan particles. Curing control can also be achieved by controlling the availability of silicic acid species for nucleation and growth of CSH and/or CASH gels. For example, methods disclosed for wellbore ^cementing geopolymers18 use powdered alkali silicate glass. The geopolymer paste contains almost no silicate species during pre-curing. Powdered alkali silicate glasses dissolve and release silicic acid species at a controlled rate during pre-curing, thus extending the thickening and curing time. However, this method produces a cured geopolymer that is not suitable for construction material applications requiring strength greater than 30 MPa. Alternatively, the metal salt (eg barium chloride) is dissolved in water and the resulting solution is then blended with the alkali silicate solution and then mixed with the dry ingredients in a mixer. These metal salts, such as barium chloride, hydrolyze in alkaline solutions, and the silicate anions co-precipitate during hydrolysis, leaving an activator solution depleted of silicate species. The degree of metal-silicate interaction depends on the metal/Si molar ratio, which determines the efficiency of the retardation. The co-precipitated silicate slowly redissolves and becomes available for geopolymerization and/or formation of CSH and/or CASH gels during subsequent curing processes. This prolongs the curing time.

For the disclosed method, the metal salt solution has to be pre-mixed with blast furnace slag to apply a protective coating to the solid, i. Much less barium salt is used to reach cure times equivalent to those of the conventional "protective layer" method. For example, at least 2% BWOB zinc salt has a retarding effect on sodium silicate activated blast furnace slag. At least 4% BWOB barium salt provides a retarding effect in sodium silicate activated blast furnace slag/carbonatite. Higher amounts of retarder are required for good protective layer coverage, but usually result in a significant reduction in the compressive strength of the cured product. Furthermore, the coverage of the protective layer is highly dependent on the surface charge of the pozzolan particles. The surface charge of blast furnace slag can be negative, while the surface charge of fly ash can be positive in solution. Therefore, in the "protective layer" method, the efficiency of the retarding effect can vary greatly with different reactive aluminosilicate sources.

Accordingly, the disclosed embodiments provide efficient inorganic retarding admixtures for controlling thickening and setting times of geopolymer compositions applicable as well cementing grouts, mortars and concretes.

Other embodiments described herein provide geopolymer compositions whose cure time can be altered by inorganic retarders. The geopolymer composition is from the group of (i) at least one low Ca Class F fly ash having no more than 8 wt% calcium oxide, (ii) blast furnace slag, Class C fly ash, vitreous calcium silicate, and kiln dust. selected at least one Ca-rich aluminosilicate; (iii) a retarding solution; and (iv) an aqueous alkali silicate activator.

The disclosed retarder solution is made by dissolving in water at least one soluble metal salt, the at least one soluble metal salt being barium chloride, barium chloride dihydrate, barium nitrate, barium nitrite. , barium metaborate monohydrate, barium nitrate hydrate, zinc nitrate, zinc chloride, zinc sulfate, lead chloride, lead nitrate, strontium chloride, strontium nitrate and strontium sulfate. Barium chloride and barium nitrate are preferred.

In one embodiment, at least one metal salt is dissolved in the retarder solution, and the retarder solution comprises from about 0.1 to about 10% metal salt BWOB. In one embodiment, the metal salt is barium chloride dihydrate. The dose of barium chloride dihydrate is about 0.10 to about 5% BWOB, more preferably about 0.5% to about 2.5% BWOB.

In one embodiment, the soluble barium salt is dissolved in water. The retarder solution is mixed with the alkali silicate activator solution prior to mixing the activator solution with all other ingredients. In another embodiment, the retardant solution and the activator solution are added separately when mixed with the dry ingredients. Alkali silicate activator solutions may include metal hydroxides and metal silicates, where the metal is potassium, sodium, or a combination of both.

Disclosed embodiments comprise (i) at least one Ca-rich aluminosilicate selected from the group of BFS, CFA, vitreous calcium silicate, and kiln dust, (ii) a retardant solution, and (iii) an alkali A geopolymer composition is provided that includes a silicate solution.

In one disclosed embodiment, the geopolymer composition comprises (i) at least one Ca-rich aluminosilicate selected from the group of BFS, CFA, vitreous calcium silicate, and kiln dust; (ii) metakaolin; (iii) a retardant solution; and (iv) an alkali silicate solution.

In one disclosed embodiment, the geopolymer composition further comprises fine and/or coarse aggregates, superplasticizers or fibers to produce mortars and concretes for construction applications.

One disclosed embodiment provides high performance and ultra high performance concrete compositions whose setting time can be controlled by inorganic retarders. High performance and ultra high performance concrete compositions comprise (i) blast furnace slag, (ii) metakaolin, (iii) a retarding solution, (iv) an aqueous alkali silicate activator, (v) at least one aggregate, and (vi) at least one micron/submicron filler;

It is an object of the present disclosure to provide effective retarding admixtures for controlling the setting time of geopolymer compositions that can be applied as well cementing, mortar and concrete. In particular, the present disclosure provides an efficient retarding method for controlling cure of geopolymer systems containing high Ca FFAs or high Ca aluminosilicates.

Low-Ca Fly Ash-Based Geopolymers Due to the low reactivity of fly ash in alkaline solutions, low-Ca FFA-based geopolymers are very slow to harden and can be cured at low temperatures (e.g., room temperature). lower final strength. "Reactivity" is defined herein as the relative mass of the binder pozzolan that has reacted with the alkaline solution. Smaller particle size fly ash is usually more reactive, such as ultrafine fly ash (UFFA), which has an average particle size of about 1-10 μm. UFFA is carefully processed by mechanically separating the ultrafine fraction from the parent fly ash. UFFA can also reduce the w/b ratio for desirable workability such as slump, producing cured geopolymers with better performance. Coal gasification fly ash is typically discharged from coal gasification power plants as SiO ₂ -rich substantially spherical particles with a maximum particle size of about 5-10 μm. The use of less reactive fly ash requires a more reactive secondary binder to produce ambient temperature curable geopolymer articles.

Alkaline activation of metakaolin produces typical geopolymer gels with moderately long curing times, eg, 2-6 hours. When metakaolin is blended, the resulting geopolymer composition may not require a retardant admixture. In contrast, alkaline activation of BFS, CFA, CKD or VCAS essentially produces CSH and/or CASH gels. Faster precipitation of CSH and/or CASH reduces curing time and improves the rate of increase in strength and final strength of the product'. When the second binder is a high Ca aluminosilicate pozzolan, the curing behavior of the resulting geopolymer system will be significantly altered. Cure times of fly ash-based geopolymers, especially alkaline activator solutions with high molar alkali hydroxide and high _SiO2 / _M2O (M=Na, K) molar ratios, have been found to be useful geopolymer products. decreases exponentially with increasing amounts of high Ca aluminosilicate pozzolans, such as BFS, that are blended. Therefore, in practical applications, proper curing control is required.

In one embodiment, the low-Ca FFA can be fly ash containing less than or equal to about 8% by weight calcium oxide. Classification of fly ash is based on ASTM C618, commonly understood in the art. In one embodiment, the low Ca FFA comprises about 5% or less by weight calcium oxide. In one embodiment, the fly ash should comprise at least 65 wt% amorphous aluminosilicate phase and have an average particle size of 60 μm or less, such as 50 μm or less, such as 45 μm or less, such as 30 μm or less. In one embodiment, the low Ca FFA has a loss on ignition (LOI) of 5% or less. In one embodiment, the low Ca FFA has an LOI of 1% or less.

One embodiment described herein provides a geopolymer composition whose cure time can be controlled by an inorganic retarder. The low Ca FFA-based geopolymer composition comprises (i) at least one low Ca Class F fly ash having no more than 8 wt% calcium oxide, (ii) blast furnace slag, Class C fly ash, vitreous calcium silicate, and at least one Ca-rich aluminosilicate selected from the group of kiln dust, (iii) a retardation solution, and (iv) an aqueous alkali silicate activator. The retarder solution is made by dissolving soluble metal salts in water, the soluble metal salts being barium chloride, barium chloride dehydrate, barium nitrate, barium nitrite, barium metaborate monohydrate, barium nitrate hydrated. zinc nitrate, zinc chloride, zinc sulfate, strontium chloride, strontium nitrate and strontium sulfate. Soluble barium salts are preferred.

In one embodiment, the low Ca FFA-based geopolymer composition further comprises metakaolin, and in one embodiment, the geopolymer composition further comprises fine and coarse aggregates for making concrete products.

High-Ca Aluminosilicate-Based Geopolymers Alkali activation of high-Ca aluminosilicate pozzolans typically produces CSH and/or CASH gels immediately upon exposure to highly alkaline solutions, resulting in excessive curing times. shortens to Without proper control of curing time, these geopolymer materials cannot be used to make useful products. Examples of these Ca-rich aluminosilicates include Ca-rich FFA, CFA, BFS, VCAS, bottom ash, and clinker kiln dust (CKD).

One embodiment comprises (i) at least one Ca-rich aluminosilicate selected from the group of Ca-rich FFA, BFS, CFA, vitreous calcium silicate, and kiln dust, (ii) a retarder solution, and (iii) A high Ca aluminosilicate-based geopolymer composition comprising at least one alkali silicate solution is provided.

In one embodiment the Ca-rich aluminosilicate is Ca-rich FFA, in one embodiment the Ca-rich aluminosilicate is BFS, and in another embodiment the Ca-rich aluminosilicate is CFA.

In one embodiment, the high Ca aluminosilicate-based geopolymer composition further comprises at least one low Ca aluminosilicate pozzolan selected from the group of low Ca FFA and metakaolin. In one embodiment, the high Ca aluminosilicate-based geopolymer composition further comprises fine and coarse aggregates for producing concrete products. In one embodiment, the geopolymer composition further comprises fine aggregate and/or coarse aggregate for producing concrete products.

High Performance and Ultra High Performance Concrete US Pat. No. 9,090,508 discloses geopolymer compositions for high performance and ultra high performance concrete. To achieve high and ultra high performance geopolymer products, highly reactive aluminosilicate materials such as metakaolin and blast furnace slag must be used as binders. The w/b ratio should be very small, eg close to the minimum. The packing density of the fine particles should be high to minimize product porosity, and coarse aggregates larger than 10 mm should not be used to improve uniformity. Thus, the hardening time of ready-mixed concrete is relatively short, especially when large amounts of blast furnace slag are used in the formulation. The composition disclosed in US Pat. No. 9,090,508 is essentially a blast furnace slag/metakaolin based binary geopolymer.

One embodiment described herein provides high performance and ultra high performance concrete compositions whose setting time can be controlled by inorganic retarders. High performance and ultra high performance concrete compositions comprise (i) blast furnace slag, (ii) metakaolin, (iii) a retarding solution, (iv) an aqueous alkali silicate activator, (v) at least one aggregate, and (vi) at least one micron/submicron filler;

Retardant Disposition Method The retardant solution is prepared by dissolving at least one soluble metal salt in water, the at least one soluble metal salt being barium chloride, barium chloride dehydrate, barium nitrate, barium nitrite, metaborate. It is selected from barium acid monohydrate, barium nitrate hydrate, zinc nitrate, zinc chloride, zinc sulfate, lead chloride, lead nitrate, strontium chloride, strontium nitrate and strontium and strontium sulfate. Any soluble metal salt that can hydrolyze in alkaline solution and co-precipitate the silicate species originally present in the alkali silicate activator solution can be used as the inorganic retardant admixture. The retarding effect depends on the type and dose of metal. The metal-silicate interaction is expected to increase with increasing dose or molar ratio of metal to silicate. The interaction between metal and silicate should not be excessive. If the interactions are dominant, the release of silicate species into the geopolymer system will be greatly hindered during the subsequent curing process, significantly affecting the early compressive strength of the product. Among all these metal salts, barium salts are preferred.

In one embodiment, at least one metal salt is dissolved in water. The retarder solution is mixed with the alkali silicate activator solution prior to mixing all ingredients. Pour the alkali silicate activator solution combined with the retarder solution into the mixer containing all the dry ingredients. In another embodiment, the retardant solution and the activator solution are added separately when mixed with the dry ingredients to make the geopolymer product.

In one embodiment, the retarder solution is mixed with the alkali silicate activator solution for about 30 minutes before mixing with all other ingredients. In another embodiment, the retarder solution is mixed with the alkali silicate activator solution for about 10 minutes before all ingredients are mixed. In another embodiment, the retarder solution is mixed with the alkali silicate activator solution for about 24 hours before all ingredients are mixed. In another embodiment, the retarder solution is added to the concrete during mixing in the ready mix truck. In this case, the retarder solution acts as a setting brake, preventing the mixed concrete from setting in the ready-mix truck during transportation to the site, such as in an emergency.

In one embodiment, at least one metal salt is included in the retarder solution, and the retarder solution comprises from about 0.1 to about 10% metal salt BWOB. In one embodiment, the metal salt is barium chloride dihydrate. The dose of barium chloride dihydrate is about 0.10 to about 5% BWOB, more preferably about 0.5% to about 2.5% BWOB.

In one embodiment the metal salt is barium metaborate monohydrate, in one embodiment the retarder solution comprises barium chloride dihydrate and zinc nitrate, in one embodiment the retarder solution comprises: Contains strontium nitrate and zinc chloride.

Retardation Mechanisms The following examples illustrate mechanisms for retarding the cure time of geopolymers of the present disclosure.

According to disclosed embodiments, metal salts are used to control the release of silicate species in the activator solution that are available for nucleation and growth of CSH and/or CASH gels during pre-curing, thereby reducing alkali A new method is provided to control the curing time of activated materials or geopolymers. In selected embodiments, experiments were conducted to study the co-precipitation process of hydrolyzed barium chloride and silicate in sodium silicate activator solutions by Raman spectroscopy. In a series of tests, after mixing the barium chloride dehydrate solution and the sodium silicate solution for 0.5 hours, the Raman spectra of the supernatant and precipitate were monitored with increasing doses of barium chloride. In a second series of tests, combined solutions of barium chloride and sodium silicate solutions were mixed and aged with a fixed dose of barium chloride dihydrate for 0.5, 2 and 24 hours respectively. The spectra of the supernatants of these barium chloride/sodium silicate solutions were then recorded.

A sodium silicate activator solution was prepared by dissolving sodium hydroxide beads (99% purity) in DI (deionized) water and combining with PQ Corp type Ru sodium silicate solution. Barium chloride dihydrate (99% purity) was separately dissolved in DI water. Table 1 shows the composition of the activator solution. The NaOH molarity was fixed at 5 and the SiO ₂ /Na ₂ O mass ratio was 1.25 throughout Examples 1-4. The activator solution used for testing was part of a high Ca FFA geopolymer composition and the dose of barium chloride dehydrate was expressed as the weight of the fly ash binder.

Raman spectra were collected using a single grating spectrograph-notch filter micro-Raman system. A Melles-Griot model 45 Ar ⁺ laser provided 5145 Å wavelength incident light directed through a broadband polarization rotator (Newport model PR-550) into the laser microscope, which was connected to a long working distance Mitutoyo 10 laser microscope. Laser light was directed through a microscope objective onto the precipitated solid or solution in a 25 ml clear vial. The laser light power was about 22 mW at the sample. The scattered light was directed through the polarizer of the analyzer and passed through a 150 μm aperture and then to holographic notch and supernotch filters (Kaiser Optical Systems). The spectroscope used a 1200 gr/mm diffraction grating (Richardson Grating Laboratory). Spectra from 50 to 1600 cm ⁻¹ were collected with the entrance slit of a JY-Horiba HR460 spectrometer set at a resolution of 6 cm ⁻¹ . The spectrometer was frequency calibrated using CCl4, so the recorded frequencies are accurate to within ±1 cm ⁻¹ . Parallel polarization (VV) spectra were collected where the incident laser light was vertically polarized.

The assignment of Raman vibrations is shown in Table 2. Attribution was made according to Halasz et ^al.19,20 . The results are shown in Figure 1 for the supernatant and Figure 2 for the precipitated solids.

FIG. 1 represents the Raman spectra of supernatant samples of sodium silicate solution after mixing with barium chloride solution for 0.5 hours for four doses of barium chloride dehydrate. The spectrum of the activator solution without retarder (RM-BC-0) clearly shows that Q ⁰ , Q ¹ and Q ² type silicate species dominate the activator solution. The ^Q0 type silicate species are completely dissociated (Fig. 1). All supernatants of samples containing barium chloride dihydrate (Table 1) showed substantially does not contain silicate species. This suggests that almost all the silicate originally present in the activator solution co-precipitated with barium hydroxide when the barium chloride solution was mixed with the alkali sodium silicate activator solution. Since silicate species precipitate as barium silicate complexes, the concentration of soluble silicate available for geopolymerization is very low during early curing. Limited availability of silicate species results in retarded cure times by impeding nucleation and growth of CSH and/CASH gels.

FIG. 2 shows the Raman spectra of the co-precipitated solid after mixing the barium chloride solution and the activator solution for 0.5 hours for three doses of retarder. The co-precipitated sample with the lowest dose of retarder (RM-BC 0.875) develops a new vibrational band at 1062 cm ⁻¹ in addition to the bands associated with Q ⁰ , Q ¹ and Q ² type silicate species. It shows a sharp Raman spectral pattern. The 1062 cm ⁻¹ band can be assigned to the Q ³ silicate species. Comparing this Raman spectrum with the spectrum of the activator solution without the retarder ( FIG. 1 , RM-BC00), the disclosed embodiment shows that the addition of the retarder results in fully dissociated silicate species (Q ⁰ ) and other It was found that the relative proportion of silicate species of the type Apparently, the barium cations interact to some extent with the silicate species, resulting in increased polymerization of the silicate species.

The intensity of each Raman band decreased with increasing dose of retarder. When the retarder was increased to 5% BWOB or a B/Si molar ratio of 0.23 (Fig. 2), the respective Raman bands disappeared almost completely, indicating that the significant interaction between barium and silicate species was It was shown to be induced with a precipitated complex. The increased interaction at high doses of barium chloride dihydrate significantly retards the release of silicate species, thus greatly extending the curing time, during which a cured geopolymer with reduced initial strength is produced.

Examples Examples Relating to the Present Invention The following examples illustrate the practice of the present disclosure in its preferred embodiments.

The following raw materials were used to prepare the samples of Examples 1-21. Two fly ash were used. One was a high CaO FFA (12.5%) from Jewett Power Station, Texas, USA, sold by Headwater Resources (Jewett fly ash). This fly ash contains 12.2 wt% CaO and has a loss on ignition (LOI) of 0.15%. The sum of Si+Al+Fe oxides was 79.57 wt%, exceeding the minimum requirement of 75 wt% for Class F fly ash according to ASTM C618. The second fly ash was a low Ca FFA from Neilsens Group, Australia. This FFA was a product of the coarser fly ash class. Its LOI was less than 0.15%. The sum of Si+Al+Fe oxides was about 93% by weight. Ground blast furnace slag grade 120 (NewCem slag cement) was obtained from Lafarge-Holcim's Sparrow Point plant in Baltimore, Maryland. The activity index was about 129 according to ASTM C989. Blast furnace slag contains about 38.5% CaO, 38.2% _SiO2 , _10.3 % _Al2O3 , and 9.2% MgO, with an average particle size of 13.8 μm, 50 volume % was less than 7 μm. Metakaolin (Kaorock) was obtained from Thiele Kaolin Company, Sandersville, GA. Metakaolin had a particle size of 0.5-50 μm, with 50% by volume less than 4 μm. Silica fume, an industrial waste product from Fe—Si alloys, is supplied by Norchem Inc. obtained from The silica fume contained 2.42 wt% carbon. Silica fume has been used to prepare activator solutions by dissolving silica fume in alkaline hydroxide solutions or added as submicron reactive fillers in the preparation of ultra high performance concrete samples.

Bluestone #7 (AASHTO T-27) was used as coarse aggregate. Dry aggregates were soaked in water for 24 hours to achieve saturated surface dryness (SSD) conditions, then a dry cloth was used to manually remove free water from the aggregate surface. SSD or oven-dried river sand was used. A Trident Solids Hygrometer (Model T90) was used to measure the moisture content of the fine aggregate samples. U.S.A. S. Silica's Min U-SIL® ground quartz powder was used to prepare ultra high performance concrete. The quartz powder has a particle size of 1-25 μm, with a median particle size of about 5 μm.

An alkali silicate activator solution was prepared using a PQ, Corp type Ru sodium silicate solution. The SiO ₂ /Na ₂ O mass ratio was about 2.40. The obtained solution contains about 13.9 wt% _Na2O , 33.2 wt% _SiO2 and 52.9 wt% water. An alkaline activator solution was prepared using sodium hydroxide beads (99% purity) and potassium hydroxide flakes (91% purity).

Examples 1 to 7
Geopolymer samples were prepared comprising high Ca Class F fly ash from Jewett Power Station, Texas, USA. The mix composition is shown in Table 3 and the ingredients are given in grams. The batch size was approximately 5000 grams. The Jewett fly ash contained approximately 12.2 wt% CaO. Geopolymer samples from Examples 1 and 2 were prepared with the retardant sodium hexametaphosphate (SHMP) for comparison. Sodium phosphate has been disclosed as a retardant in the prior art or literature. SHMP doses were 1.50% and 2.25% BWOB, respectively. Geopolymer samples of Examples #4 through Example #7 were prepared using the retardant barium chloride dihydrate at doses of 0.50% to 1.00% by weight BWOB to demonstrate retardation efficiency.

An activator solution was prepared by dissolving NaOH beads (99% purity) in water and then combining the resulting solution with type Ru sodium silicate solution. Retardant solutions were prepared by separately dissolving barium chloride dihydrate or sodium metaphosphate (SHMP) in water. After mixing the retarder solution for 2 hours, it was poured over the Jewett fly ash in a high intensity K-Lab mixer (Kercher Industries) for 6 minutes. The resulting fresh paste was immediately transferred to a mold (3 inches high and 40 mm high) and treated on a vibrating table for about 1 minute to remove trapped air bubbles. For fresh pastes, initial and final set times were determined using a Vicatronic Automatic Vicat apparatus (model E004N). Hereinafter, said device will be referred to as AutoVicat according to ASTM C191.

The initial cure time for the control sample (Example 3, BC00) was determined to be 29 minutes and the final cure time was 45 minutes. The addition of 0.50% BWOB barium chloride dihydrate increased the initial set time to 47 minutes and the final set time to 78 minutes (Example 4). Increasing the barium chloride dihydrate to 0.75% BWOB increased the initial set time to 68 minutes and the final set time to 99 minutes (Example 5). Increasing the barium chloride dihydrate to 0.875% BWOB increased the initial set time to 114 minutes and the final set time to 144 minutes (Example 6). Further increasing the barium chloride dihydrate to 1% BWOB increased the initial set time to 391 minutes and the final set time to 450 minutes (Example 7). Isothermal calorimetry data revealed that the addition of retarder significantly reduced the heat of hydration of the geopolymer.

In comparison, doping with 1.5% BWOB sodium metaphosphate gave an initial set time of 35 minutes and a final set time of 57 minutes. Increasing the sodium metaphosphate to 2.25% BWOB showed a slight increase in initial set time to 38 minutes and final set time to 63 minutes. Clearly, the present retardant is much more efficient than those disclosed in the prior art or literature.

Examples 8-10
A binary FFA/BFS geopolymer mortar sample of the mixed composition shown in Table 4 is prepared. Ingredients are given in grams. Low Ca Class F fly ash from Neilsens Concrete, Australia, ground blast furnace slag from Lafarge-Holcim, and river sand (saturated surface dry) were mixed for 3 minutes in a Waring 7 quart planetary mixer. An activator solution was prepared by dissolving NaOH beads in water and then combining the resulting solution with type Ru sodium silicate solution. The activator solution was allowed to stand overnight before use. If barium chloride dihydrate was present, it was dissolved separately in water. The retardant dose was fixed at 0.875% BWOB.

An activator solution without barium chloride dihydrate (Example #8) was poured into the FFA/BFS/sand mixture and mixed at medium speed for 5 minutes. Fresh mortar was measured for set time using an AutoVicat according to ASTM C191. The initial cure time was 114 minutes and the final cure time was 186 minutes.

Geopolymer mortar samples were prepared after mixing the retarder solution with the activator solution for 30 minutes (Example 9). For fresh mortar, curing time was measured with AutoVicat according to ASTM C191. The initial cure time was 249 minutes and the final cure time was 348 minutes.

The retarder solution was added when the activator solution was poured into the dry ingredient mixture (Example 10). The mixture was mixed for 5 minutes. Fresh mortar was measured for set time using an AutoVicat according to ASTM C191. The initial cure time was 236 minutes and the final cure time was 342 minutes.

Examples 11-13
Binary FFA/BFS geopolymer mortar samples of the same mixed composition used in Examples 8-10 are prepared (Table 4). Low Ca Class F fly ash from Neilsens Group, Australia, ground blast furnace slag from Wagners, Australia, and river sand (saturated surface dry) were mixed in a Waring 7 quart planetary mixer for 3 minutes. An activator solution was prepared by dissolving NaOH beads in water and then combining the resulting solution with type Ru sodium silicate solution. The activator solution was allowed to stand overnight before use. If barium chloride dihydrate was present, it was dissolved separately in water. The retardant dose was fixed at 1.25% BWOB.

An activator solution without barium chloride dihydrate (Example #11) was poured into the FFA/BFS/sand mixture and mixed at medium speed for 5 minutes. Fresh mortar was measured for set time using an AutoVicat according to ASTM C191. The initial cure time was 59 minutes and the final cure time was 144 minutes. The compressive strength was 4081 psi after 7 days of curing and increased to 8032 psi after 28 days of curing.

Geopolymer mortar samples were prepared after mixing the retarder solution with the activator solution for 30 minutes (Example 12). For fresh mortar, curing time was measured with AutoVicat according to ASTM C191. The initial cure time was 136 minutes and the final cure time was 198 minutes. The compressive strength was 3673 psi after 7 days of curing and increased to 7734 psi after 28 days of curing.

The retarder solution was added when the activator solution was poured into the dry ingredient mixture (Example 13). The mixture was mixed for 5 minutes. Fresh mortar was measured for set time using an AutoVicat according to ASTM C191. The initial cure time was 114 minutes and the final cure time was 180 minutes. The compressive strength was 4064 psi after 7 days of curing and increased to 7970 psi after 28 days of curing.

Examples 14-16
To prepare geopolymeric ultra high performance concrete (GUHPC), metakaolin (5.71 wt%) and ground blast furnace slag (14.72 wt%) were mixed in a high intensity mixer (K-Lab, Kercher Industries). Mixed. The activators are Na ₂ O (2.12 wt %) as NaOH, K ₂ O (1.35 quart % wt %) as KOH, SiO ₂ (3.95 wt %) as type Ru sodium silicate solution, and Prepared by mixing water (10.15% by weight). Any barium chloride dihydrate was dissolved separately in water and combined with the activator solution 5 minutes prior to sample preparation. The activator solution was then poured into the MK/BFS blend and mixed for 3 minutes at approximately 350 rpm. Dry river sand (50% by weight) and quartz flour (10.00% by weight) were then added to the mixture and mixing was continued for 3 minutes. Towards the end of mixing silica fume (2.00%) was added and mixing continued for 3 minutes. For the resulting pastes, the initial set time was determined using an AutoVicat or a manual Vicat device. The paste was poured into a 2″×4″ cylinder and allowed to cure at room temperature. Compressive strength was measured after curing for 28 days with a Test Mark CM-4000-SD compression. The compressor is calibrated to NIST traceable standards.

In the absence of barium chloride dihydrate (Example 14), the initial cure time was estimated to be about 30 minutes and the compressive strength was about 19972 psi after 28 days of cure. With the addition of 1 wt% BWOB barium chloride dihydrate (Example 15), the initial cure time was 54 minutes and the compressive strength after 28 days of cure was about 20146 psi. When 2 wt% BWOB of barium chloride dihydrate was added (Example 16), the initial set time increased to 89 minutes and the compressive strength after 28 days of set was about 19424 psi.

Examples 17-18
To prepare the GUHPC samples, metakaolin (5.92 wt%) and ground blast furnace slag (15.28 wt%) were mixed in a high intensity mixer (K-Lab, Kercher Industries). The activators were Na ₂ O (1.08 wt %) as NaOH, K ₂ O (2.47 quart % wt %) as KOH, SiO ₂ (3.80 wt %) as silica fume, and water (9.45 wt %). % by weight). Silica fume was dissolved in an alkali hydroxide solution and the resulting activator solution was aged for one week prior to use. Any barium chloride dihydrate was dissolved separately in water and then combined with the activator solution 10 minutes prior to sample preparation. The activator solution was then poured into the MK/BFS blend and mixed for 3 minutes at approximately 350 rpm. Dry river sand (50% by weight) and quartz flour (10.00% by weight) were then added to the mixture and mixing was continued for 3 minutes. Towards the end of mixing silica fume (2.00%) was added and mixing continued for 3 minutes. For the resulting pastes, a manual Vicat device was used to determine initial and final set times. The paste was poured into a 2″×4″ cylinder and allowed to cure at room temperature. Compressive strength was measured after 28 days of curing.

Without barium chloride dihydrate (Example 17), the initial set time was 15 minutes, the final set time was 19 minutes, and the compressive strength after 28 days of curing was about 26418 psi. With the addition of 1.5 wt% BWOB barium chloride dihydrate (Example 18), the initial set time was 73 minutes, the final set time was 81 minutes, and the compressive strength after 28 days of curing was about It was 23817 psi.

Examples 19-20
Examples 19 and 20 demonstrate the efficiency in controlling hardening using soluble barium salts in geopolymer concrete.

The mix composition for both concrete samples contained 78.75 wt% aggregate with a coarse to fine aggregate mass ratio of 1.74. The binder contained 80% low CaO FFA and 20% blast furnace slag. The w/b ratio was 0.47, the NaOH molarity was 5.7 and the _SiO2 / _Na2O mass ratio was 1.15 for the activator solution. To prepare geopolymer concrete samples, low CaO FFA from Neilsens Group, Australia, blast furnace slag from Lafarge-Holcim, and river sand (SSD conditions) were mixed in a high intensity mixer (K-Lab, Kercher Industries) for 3 minutes. An activator solution was prepared by dissolving NaOH beads in water and then combining the resulting solution with type Ru sodium silicate solution. The activator solution was allowed to stand overnight before use.

The activator solution without retarder (Example #19) was poured into the FFA/BFS/sand mixture and mixed for 3 minutes at 300 rpm. SSD coarse aggregate (Grade #7) was then added and mixed at a low mixing speed (eg, 20 rpm) for 5 minutes. Ready-mixed concrete was sieved to obtain mortar samples measured with an Acme Penetrometer according to ASTM C403 for set time. Ready-mixed concrete was also poured into a 3″×6″ cylinder and shaken on a vibrating table for 1 minute. The samples were capped and cured at room temperature until the compressive strength was measured. The initial cure time was 75 minutes and the final cure time was 168 minutes. Compressive strength after 7 days of curing was 4509 psi and increased to 7992 psi after 28 days of curing.

Additional concrete samples with retarders were prepared using the same procedure described in Example 19 (Example 20). Barium chloride dihydrate was separately dissolved in water. The retardant dose was 1.00% BWOB. The retarder solution was mixed with the activator solution for 30 minutes prior to preparing ready-mixed concrete samples. The ready-mixed concrete was sieved to obtain mortar samples for set time using an Acme Penetrometer according to ASTM C403. The initial cure time was 313 minutes and the final cure time was 572 minutes. Compressive strength was 3707 psi after 7 days of curing and 7259 psi after 28 days of curing.

example 21
The same mix composition as Example #8 without the retarder solution was mixed for 30 minutes, then the retarder solution (3% barium chloride BWOB) was poured into the paste with mixing and mixed for an additional 10 minutes. After mixing was stopped, the mortar sample was subjected to ASTM C191 for set time determination. About 7.4 hours after pouring the activator solution into the dry mixture, the mortar sample showed no signs of hardening, indicating that the retarder effectively retards hardening. Retarders can be used for emergency setting braking of raw geopolymer concrete in transit on ready-mix trucks.

Having described in detail a number of embodiments of the present disclosure, it will be apparent that modifications and variations are possible without departing from the scope of the invention as defined in the appended claims. Furthermore, all examples in this disclosure, while indicating numerous embodiments of the present invention, are provided as non-limiting examples and are therefore to be construed as limiting the various implementations so indicated. It should be understood that it should not.

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All documents, patents, journal articles and other materials cited in this application are hereby incorporated by reference.

Although the present disclosure has been disclosed with reference to certain specific embodiments, many modifications to the described embodiments can be made without departing from the scope and scope of the present disclosure as defined in the appended claims. Modifications, alterations, and alterations are possible. Therefore, it is intended that the present disclosure not be limited to the described embodiments, but rather have the full scope defined by the language of the following claims and equivalents thereof.

Claims (15)

A method of making a geopolymer composition comprising dissolving at least one retarder in water and combining with at least one alkali silicate activator solution prior to mixing with other ingredients to make a geopolymer product. and
The geopolymer composition is
at least one reactive aluminosilicate;
A geopolymer composition having a controllable cure time comprising at least one retarder solution and at least one alkali silicate activator solution, the composition comprising:
wherein said at least one retarder is a soluble metal salt that hydrolyzes in alkaline solution and co-precipitates silicate species present in said alkali silicate activator solution,
a geopolymer composition, wherein the at least one retarder is barium chloride dihydrate, used in an amount of 0.5-5% BWOB;
Method. Dissolving at least one retarder in water to form a retarder solution, and adding at least one alkali silica to the retarder solution when combined with other ingredients to produce the geopolymer product. A method of making a geopolymer composition for addition with an acid salt activator solution, comprising:
The geopolymer composition is
at least one reactive aluminosilicate;
A geopolymer composition having a controllable cure time comprising at least one retarder solution and at least one alkali silicate activator solution, the composition comprising:
wherein said at least one retarder is a soluble metal salt that hydrolyzes in alkaline solution and co-precipitates silicate species present in said alkali silicate activator solution,
a geopolymer composition, wherein the at least one retarder is barium chloride dihydrate, used in an amount of 0.5-5% BWOB;
Method. dissolving at least one retarder in water to form a retarder solution, and adding the retarder solution after mixing at least one alkali silicate activator solution with dry ingredients; A method of manufacturing,
The geopolymer composition is
at least one reactive aluminosilicate;
A geopolymer composition having a controllable cure time comprising at least one retarder solution and at least one alkali silicate activator solution, the composition comprising:
wherein said at least one retarder is a soluble metal salt that hydrolyzes in alkaline solution and co-precipitates silicate species present in said alkali silicate activator solution,
a geopolymer composition, wherein the at least one retarder is barium chloride dihydrate, used in an amount of 0.5-5% BWOB;
Method. 1. A method of making a geopolymer composition having a controllable cure time comprising combining at least one reactive aluminosilicate, at least one retarder and at least one alkali silicate activator solution, the method comprising:
the retarder comprises a retarder solution made by dissolving a soluble metal salt in water;
the soluble metal salt hydrolyzes in an alkaline solution to co-precipitate silicate species present in the alkali silicate activator solution;
the retarder is added to the reactive aluminosilicate at or after the addition of the alkali silicate activator to the retarder;
the at least one retarder is barium chloride dihydrate, used in an amount of 0.5-5% BWOB;
The manufacturing method. 5. The method of claim 4, wherein the at least one reactive aluminosilicate comprises low Ca Class F fly ash (FFA) and blast furnace slag (BFS). 6. The method of claim 5, wherein the low Ca Class F fly ash (FFA) is fly ash containing 8 wt% or less calcium oxide. 6. The method of claim 5, wherein said at least one reactive aluminosilicate further comprises metakaolin (MK). The at least one reactive aluminosilicate is high Ca class F fly ash (FFA), class C fly ash (CFA), blast furnace slag (BFS), vitreous calcium silicate (VCAS), bottom ash, and clinker kiln 5. The method of claim 4, comprising at least one Ca-rich aluminosilicate selected from the group of dusts (CKD). 9. The method of claim 8, wherein the at least one reactive aluminosilicate further comprises metakaolin (MK). 5. The method of claim 4, wherein the at least one reactive aluminosilicate comprises blast furnace slag (BFS) and metakaolin (MK). 5. The method of claim 4, wherein the at least one reactive aluminosilicate comprises class C fly ash (CFA) and metakaolin (MK). 5. The method of claim 4, wherein the soluble metal salt is barium chloride dihydrate. 5. The method of claim 4, wherein the retarder solution is mixed with the alkali silicate activator solution prior to mixing with all other ingredients. 5. The method of claim 4, wherein said retarder solution and said alkali silicate activator solution are added separately when mixed with all other ingredients. 5. The method of claim 4, wherein the retarder solution is mixed with the alkali silicate activator solution for one period of 10 minutes, 30 minutes, and 24 hours before mixing with all other ingredients.

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