Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/006—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing mineral polymers, e.g. geopolymers of the Davidovits type
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B12/00—Cements not provided for in groups C04B7/00 - C04B11/00
  • C04B12/005—Geopolymer cements, e.g. reaction products of aluminosilicates with alkali metal hydroxides or silicates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/041—Aluminium silicates other than clay
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/10—Clay
  • C04B14/106—Kaolin
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B18/04—Waste materials; Refuse
  • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
  • C04B18/08—Flue dust, i.e. fly ash
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B18/04—Waste materials; Refuse
  • C04B18/14—Waste materials; Refuse from metallurgical processes
  • C04B18/141—Slags
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
  • C04B20/0076—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials characterised by the grain distribution
  • C04B20/008—Micro- or nanosized fillers, e.g. micronised fillers with particle size smaller than that of the hydraulic binder
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
  • C04B22/08—Acids or salts thereof
  • C04B22/12—Acids or salts thereof containing halogen in the anion
  • C04B22/124—Chlorides of ammonium or of the alkali or alkaline earth metals, e.g. calcium chloride
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/0004—Compounds chosen for the nature of their cations
  • C04B2103/001—Alkaline earth metal or Mg-compounds
  • C04B2103/0011—Ba
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/20—Retarders
  • C04B2103/22—Set retarders
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the disclosed invention relates generally to admixtures for geopolymer compositions. More particularly, it relates to retarding admixtures for efficient control of settings in a geopolymer compositions and systems which may be employed for specific applications.
• geopolymers should have a reasonably long setting time. This means that concrete or mortar made using a pozzolanic binder should have a setting time long enough to permit transport and placement. However, it becomes uneconomic if the setting time is too long. Thus, improvements in proper control of the setting time by using a set retarder is crucial to successful applications of geopolymer materials in construction and building industries.
• the present disclosure provides a geopolymer composition having a controllable setting time comprising: at least one reactive aluminosilicate; at least one retarder; and at least one alkali silicate activator solution.
• the present disclosure provides a method of making a geopolymer composition having a controllable setting time comprising: combining at least one reactive aluminosilicate, at least one retarder and at least one alkali silicate activator solution.
• FIG. 1 illustrates Raman spectra of a sodium silicate activator solution that contain 0% to 5% barium chloride monohydrate BWOB according to one embodiment of the present disclosure.
• FIG. 2 illustrates Raman spectra of co-precipitated silicate materials that contains 0.5%, 0.75, 0.875 and 1.0% barium chloride monohydrate BWOB according to one embodiment of the present disclosure.
• the term“comprising”, the term“having”, the term“including,” and variations of these words are intended to be open-ended and mean that there may be additional elements other than the listed elements.
• directional terms such as“top,”“bottom,” “upper,”“lower,”“above,”“below,”“left,”“right,”“horizontal,”“vertical,”“up,”“down,” etc., are used merely for convenience in describing the various embodiments of the present disclosure.
• the embodiments of the present disclosure may be oriented in various ways.
• the diagrams, apparatuses, etc., shown in the drawing figures may be flipped over, rotated by 90° in any direction, reversed, etc.
• a value or property is “based” on a particular value, property, the satisfaction of a condition, or other factor, if that value is derived by performing a mathematical calculation or logical decision using that value, property or other factor.
• actual temperature refers to the actual temperature of the air in any particular place, as measured by a thermometer.
• the term“BWOB” refers“by weight of binder” which is generally recognized as the amount (in percent) of a material added to cement when the material is added based on the total amount of a specific binder or the blend of binders.
• binders are typically pozzolanic materials called pozzolanic precursor which can be activated by alkaline solutions.
• cement refers to a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together.
• Seldom used on its own, cement may be utilized to bind sand and gravel (aggregate) together.
• Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete.
• Cements used in construction are usually inorganic, often lime or calcium silicate based, and can be characterized as either hydraulic or non-hydraulic, depending on the ability of the cement to hydrate in the presence of water.
• the term“concrete” refers to a heavy, rough building material made from a mixture of broken stone or gravel, sand, cementing material, and water, that can be spread or poured into molds and that forms a stone-like mass on hardening.
• Some embodiments may include a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time. Most frequently Portland cement may be utilized but sometimes other hydraulic cements may be used, such as a calcium alumina te cement.
• Geopolymers are considered to be a new type of cementing materials without Portland cement.
• geopolymer refers to sustainable cementing binder systems without Portland cement.
• geopolymers of the disclosed invention are related to inorganic polymers with a three-dimensional network structure similar to those of organic thermoset polymers.
• the backbone matrix of the disclosed geopolymers is an X-ray amorphous analogue of the framework of zeolites, featuring tetrahedral coordination of Si and A1 atoms linked by oxygen bridges, with alkali metal cations (typically Na + and/or K + ) associated as charge balancers for AIO 4 .
• Geopolymers of the disclosed invention may be more widely regarded as a class of alkali- activated materials (AAM) composed up of alkali-aluminosilicate and/or alkali-alkali earth- aluminosilicate phases, as a result of the reaction of an solid aluminosilicate powder (term pozzolanic precursor) with an alkali activator.
• AAM alkali- activated materials
• geopolymer composition refers to a mix proportion consisting of pozzolanic precusors and alkali activator in solid or liquid form Additionally a geopolymer composition may further include fine and coarse aggregate, fibers and other admixtures depending on the application.
• the term“mortar” refers to a workable paste containing fine aggregate used to bind building blocks such as stones, bricks, and concrete masonry units together, fill and seal the irregular gaps between them, and sometimes add decorative colors or patterns in masonry walls.
• mortar includes pitch, asphalt, and soft mud or clay, such as used between mud bricks. Cement or geopolymer mortar becomes hard when it cures, resulting into a rigid structure.
• room temperature refers to a temperature of from about 15 °C (59 °F) to 25 °C (77 °F).
• the term“setting” refers to conversion of a plastic paste into a non-plastic and rigid mass.
• the term“set time” or“setting time” refers to the time elapsed between the moment water (alkali activator solution) is added to the cement (pozzolanic precursor) to the time at which paste starts losing its plasticity (initial setting).
• Final setting time is the time elapsed between the moment the water (alkali activator solution) is added to the cement (pozzolanic precursor) to the time at which the paste has completely lost its plasticity and attained sufficient firmness to resist certain definite pressure.
• the term“sparingly soluble in water” refers to a substance having a solubility of 0.1 g per 100 ml of water to 1 g per 100 ml of water. Unless specified otherwise, the term“sparingly soluble” and“sparingly soluble in water” are used interchangeably in the description of the invention below to refer to substances that are sparingly soluble in water.
• water insoluble refers to a substance that has a solubility of less than 0.1 g per 100 ml of water.
• Geopolymers are a class of alkali-activated binders with a three-dimensional network structure similar to those of organic thermoset polymers.
• the backbone matrix of geopolymers is an X-ray amorphous analogue of the framework of zeolites, featuring tetrahedral coordination of Si and A1 atoms linked by oxygen bridges, with alkali metal cations (typically Na + and/or K + ) associated as charge balancers for AIO 4 .
• the empirical formula of geopolymers can be presented as M n [-(Si0 2 ) z -A10 2 ] n ⁇ wFUO where M represents the alkalis cation; z, the molar ratio of Si to A1 (1, 2 or 3); and n, the degree of polycondensation.
• M represents the alkalis cation
• z the molar ratio of Si to A1 (1, 2 or 3)
• n the degree of polycondensation.
• the dissolution of the reactive Low-Ca aluminosilicate source by alkaline hydrolysis consumes water and produces aluminate and silicate species.
• This first stage of the geopolymerization is controlled by the aptitude of the alkaline compound to dissolve the fly ash glass network and to produce small reactive species of silicates and aluminates:
• the species become part of the aqueous phase, i.e., the activating solution, which already contains silicate.
• a complex mixture of silicate, aluminate and aluminosilicate species is thereby formed.
• the solution becomes more and more concentrated, resulting in the formation of an alkali aluminosilicate gel (AAS), as the species in the aqueous phase form large networks by poly-condensation:
• AAS alkali aluminosilicate gel
• the system continues to rearrange and reorganize, as the connectivity of the gel network increases, resulting in a three-dimensional aluminosilicate network that set and hardens during subsequent curing process.
• Low-Ca reactive aluminosilicates include m eta kaolin (MK), certain calcined zeolites, and low Ca Class F fly ash (Low-Ca FFA).
• Metakaolin is an amorphous aluminosilicate pozzolanic material and its use dates back to 1962 when it was incorporated in concrete for the Jupia Dam in Brazil. It is a thermally activated aluminosilicate material with high pozzolanic activity comparable to or exceeded by the activity of fumed silica. It is generated by calcination of kaolinitic clay at 650 °C to 800 °C depending on the purity and crystallinity of the precursor clays. Alkali activation of metakaolin yields a typical AAS gel composition that will set and harden at ambient temperatures.
• the mechanical properties and microstructure of geopolymer strongly depend on the initial molar Si/Al ratio. Better strength properties have been reported for mixtures with S1O2/AI2O3 ratios in the range of 3.0-3.8 with a molar M2O/AI2O3 ratio of about one.
• Fly ash is a fine, powdery substance that“flies up” from the coal combustion chamber (boiler) and is captured by emissions control systems, such as an electrostatic precipitator or fabric filter“baghouse,” and scrubbers. About 131 million tons of fly ash is produced annually and approximately 56 million tons of that fly ash is recycled. Worldwide, about 65% of the fly ash produced is disposed of in landfills or ash ponds. The burning of anthracite and bituminous coal typically produces Class F fly ash that contains less than 8% CaO. Fly ash is mainly comprised of glassy spherical particles. American Society for Testing and Materials (ASTM) C618 standard recognizes two major classes of fly ashes, Class C and Class F.
• ASTM American Society for Testing and Materials
• the lower limit of (Si(3 ⁇ 4 + AI2O3 + Fe2(3 ⁇ 4) for Class F fly ash (FFA) is 70% and that for Class C fly ash (CFA) it is 50%.
• High calcium oxide content makes Class C fly ashes, which possess cementitious properties leading to the formation of calcium silicate and calcium aluminate hydrates when mixed with water, without requiring alkali activation.
• US Pat. No. 5,435,843 discloses an alkali activated Class C fly ash composition where the initial setting time of the cement is less than about 5 minutes.
• Class F fly ashes have a maximum content of calcium oxide of about 18 wt.%, whereas Class C fly ashes generally have higher calcium oxide contents, such as 20 to 40 wt.%.
• Low-Ca FFA usually contains less than 8 wt.% of CaO.
• Low-Ca FFA based geopolymers usually set and harden very slowly and have a low final strength when cured at ambient temperatures (e.g., room temperature) but its reactivity increases with increasing curing temperature.
• alkali activation of Low-Ca FFA requires high temperature curing.
• a more reactive aluminosilicate material such as ground granulated blast furnace slag (BFS) or metakaolin must be blended to manufacture a geopolymer product that sets and hardens at ambient temperatures.
• BFS ground granulated blast furnace slag
• metakaolin must be blended to manufacture a geopolymer product that sets and hardens at ambient temperatures.
• Ground granulated blast furnace slag is another type of reactive aluminosilicate material that is rich in alkali-earth oxides such as CaO and MgO. It is a glassy granular material that varies, from a coarse, popcorn-like friable structure greater than 4.75 mm in diameter to dense, sand-size grains. Grinding reduces the particle size to cement fineness, allowing its use as a supplementary cementitious material in Portland cement-based concrete.
• Blast furnace slag is essentially a calcium aluminosilicate glass, typically containing 27-38% Si0 2 , 7-12% A1 2 0 3 , 34-43% CaO, 7-15% MgO, 0.2-1.6% Fe 2 0 3 , 0.15-0.76% MnO and 1.0- 1.9% by weight.
• Blast furnace slag is usually classified into three grades, i.e., 80, 100 and 120 by ASTM C989-92. Furthermore, ultrafine blast furnace slag is even more reactive compared to BFS 120.
• MC-500® Microfine® Cement (de neef Construction Chemicals) is an ultrafine furnace slag with particle sizes less than about 10 mpi and a specific surface area of about 800 m /kg. Since BFS is almost 100% glassy, it is generally more reactive than most fly ashes. Alkali activation of BFS yields essentially calcium silicate hydrate (CSH) and calcium aluminosilicate (CASH) gels. It is well known that geopolymers made by alkali activation of BFS usually set and hardens very quickly even at ambient temperature, resulting in much higher ultimate strength than geopolymers made with low Ca class F fly ash.
• the time of initial set is less than 60 minutes making it difficult to mix, place and finish.
• Alkali activated slag has been found to have some superior properties as compared to Portland cement concrete such as low hydration heat, high early strength and excellent durability in an aggressive environment. 1
• a survey of the published literature showed that this binder system has some serious problems such as rapid setting and high drying shrinkage.2’ 3 These problems must be resolved before it can be used in commercial practice.
• fly ash containing high CaO contents (High-Ca FFA), e.g., greater than 8 wt.% and less than 20 wt.% may still be classified as type F according to ASTM C-618.
• the setting times of fly ash based geopolymers decrease exponentially as the CaO content increases and however compressive strength increases with increasing CaO. 4 Disclosed embodiments found that flash setting might occur in fresh geopolymers made with High-Ca FFA containing 12.2 wt.% CaO.
• Class C fly ash bears some similarities to blast furnace slag. Both are calcium alumino-silicate glasses. These pozzolanic materials are termed reactive alkali-earth aluminosilicates, or High-Ca reactive aluminosilicate. 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 of fiberglass production. In a representative glass fiber manufacturing facility, typically about 10-20 wt.% of the processed glass material is not converted into the final product and is rejected as by-product or waste VCAS and sent for disposal to a landfill.
• VCAS is 100% amorphous and its composition is very consistent, mainly including about 50-55 wt.% Si(3 ⁇ 4, 15-20 wt.% AI 2 O 3 , and 20-25 wt.% CaO.
• Ground VCAS exhibits pozzolanic activity comparable to silica fume and metakaolin when tested in accordance with ASTM C618 and Cl 240.
• CKD is a by-product of the manufacture of Portland cement, and is an industrial waste. Over 30 million tons of CKD are produced worldwide annually, with significant amounts put into landfills.
• Typical CKD contains about 38-64 wt.% CaO, 9-16 wt.% Si(3 ⁇ 4, 2.6-6.0 wt.% AI 2 O 3 , 1.0-4.0 wt.% Fe 2 0 3 , 0.0-3.2 wt.% MgO, 2.4-13 wt.% K 2 0, 0.0-2.0 wt.% Na 2 0. 1.6-18 wt.% SO 3 , 0.0-5.3 wt.% Cf, and has 5.0- 25 wt.% LOI.
• CKD is generally a very fine powder (e.g., about 4600-14000 cm / g specific surface area).
• CSH gel ettringite (3CaO Al 2 0 3 -3CaS0 4 -32H 2 0), and/or syngenite (a mixed alkali-calcium sulfate) will occur during alkali activation.
• ettringite 3CaO Al 2 0 3 -3CaS0 4 -32H 2 0
• syngenite a mixed alkali-calcium sulfate
• geopolymers should have a reasonably long setting time. This means that concrete or mortar made using a pozzolanic binder should have a setting time long enough to permit transport and placement. However, it becomes uneconomic if the setting time is too long. According to disclosed embodiments, proper control of the setting time by using a set retarder is crucial to successful applications of geopolymer materials in construction and building industries.
• Control of set times may be achieved by appropriately formulating an activator solution composition for High-Ca aluminosilicate based geopolymers.
• a large w/b and a low concentration of alkali silicate may yield a geopolymer paste with a sufficiently long set time or workability.
• the performance of the hardened product is usually affected significantly and a much lower strength and large dry shrinkage are expected.
• a diverse selection of admixtures has been used to retard the setting in alkali-activated cements or geopolymers, although their retarding efficiencies vary widely.
• US Pat. No. 5,366,547 discloses a method to use a phosphate additive to retard the set time of sodium hydroxide activated blast furnace slag.
• Examples of a phosphate retarder include sodium metaphosphate, sodium polyphosphate, potassium metaphosphate, and potassium polyphosphate.
• the retarding effect of these phosphate additives may vary when the sodium silicate solution is used to activate BFS or other types of High-Ca aluminosilicates.
• Kalina et al. 7 used Na 3 P0 4 to retard setting 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 affected (decreased) significantly when a high dosage of the retarder was applied to achieve a long set time or workable time.
• US 2011/0284223 discloses compositions and methods for well cementing application that employ organic compounds to retard thickening of geopolymeric systems at elevated temperatures.
• the geopolymer compositions are not new and have been disclosed in the prior art and extensively studied in the literature.
• the preferred compounds as a retarder include aminated polymer, amine phosphonates, quaternary ammonium compounds and tertiary amines. While geopolymer composition itself is not unique, however, the impact of these retarders on the hardened properties such as compressive strength was not previously developed ⁇ communicated.
• Chinese Pat. CN 102249594B discloses complex retarders to retard set times of alkali activated blast furnace slag.
• the complex retarder is composed of sodium chromate, heterocyclic amino acid and silicone surfactant.
• Chinese Pat. CN 1118438C discloses a complex retarder consisting of potassium chromate, sugar and phenol for sodium silicate activated slag. The initial setting can be adjusted between 1 hour and 70 hours. However, the retarder may not be desirable as chromate is a highly mobile, easily migrating, toxic anionic species and poses the risk to contaminate the environment.
• Chinese Pat. Appl. CN 101723607A discloses soluble zinc salts to retard set times of sodium silicate activated blast furnace slag.
• These zinc salts include nitrate, sulfate and chloride.
• Chinese Pat. Appl. CN 1699251 A and CN 100340517C disclose barium salt as a retarder for alkali-activated carbonite/blast furnace slag. Either zinc or barium salt is dissolved in water and added to blast furnace slag. Then the alkaline activator solution is added to the mixture. Alternatively, the salt powder is ground with blast furnace slag. The activator solution is then mixed with the solid blend.
• CN 102249594B discloses that silicone surfactant is adsorbed on the surfaces of blast furnace slag particles, chargers are introduced, resulting in repulsion to reduce the migrating rate of Ca 2+ and/or reduce the electrostatic attraction of silicate anions, thereby preventing CSH gel formation.
• Ca 2+ cations released during dissolution of blast furnace slag in a highly alkaline environment bond to the phosphate anions from the phosphate retarder, e.g., NasPCU Formation of insoluble calcium phosphate compounds reduces available Ca 2+ and thus causes nucleation and growth of the CSH phase to be poisoned, and thus set times are extended.
• US 20160060170 discloses geopolymer compositions with a nanoparticle retarder to control set times.
• the reactive aluminosilicates include metakaolin, fly ash or rice husk ash.
• Reactive aluminosilicate particles are coated with nanoparticles such as halloysite nanotube or kaolin nanoclay particles before mixing with sodium silicate activator solution.
• the nanoparticle coating is to retard geopolymerization reaction.
• the barium salt solution is premixed with blast furnace slag/carbonatite powders. Because the surfaces of blast furnace slag particles are negatively charged in water, Ba 2+ cations tend to adsorb on the surfaces of the slag grains.
• insoluble barium precipitates form a thin film on the slag grains and thus prevent the slag from contact with the alkaline solution (Chinese Pat. Appl. CN 1699251A).
• the solution of the metal salts such as barium nitrate must be mixed with the pozzolanic particles before mixing with an alkaline silicate solution to improve the coverage of the protective coating.
• Disclosed embodiments provide a new method using metal salts to retard set times of alkali activated materials or geopolymers.
• Fast setting of alkali activated High-Ca reactive aluminosilicates is related to the formation of CSH and/or CASH gels at early curing time. Ca 2+ cations are released during dissolution of High-Ca reactive aluminosilicate particles and the cations react almost instantly with silicate anions present in the alkaline solution. Control of setting can be achieved through the methods in the prior art, e.g., through removal of Ca 2+ ions in the alkaline solution and/or formation of protecting layers on the surfaces of pozzolanic particles.
• Control of setting can be also achieved by controlling availability of silicate species for nucleation and growth of CSH and/or CASH gels.
• powdered alkali silicate glass is used in the disclosed method for well cementing geopolymers.
• the geopolymer paste contains little silicate species in the early curing time.
• the powdered alkali silicate glass dissolves and releases silicate species at a controlled rate during the early curing time and thus thickening and setting times are extended.
• this method yields hardened geopolymers that are not appropriate in the application for construction materials where strength over 30 MPa is required.
• metal salts e.g., barium chloride
• these metal salts such as barium chloride hydrolyze in the alkaline solution and during hydrolysis silicate anions are co-precipitated, leaving an activator solution depleted in silicate species.
• the extent of metal-silicate interactions depends on the molar metal/Si ratio that determines efficiency of retardation.
• the co-precipitated silicate re-dissolves slowly and becomes available for geopolymerization and/or formation of CSH and/or CASH gels during the subsequent curing process. Thus, the set time is extended.
• the disclosed method uses much less barium salts to reach comparable set times as with the“Protecting Layers” method disclosed in Chinese Pat. Appl. CN 101723607A, CN 1699251A and CN 100340517C where metal salt solution must be premixed with the solid, i.e., the blast furnace slag to achieve a protective coating on the pozzolanic grains.
• metal salt solution must be premixed with the solid, i.e., the blast furnace slag to achieve a protective coating on the pozzolanic grains.
• at least 2% BWOB zinc salts take the retarding effect in the sodium silicate activated blast furnace slag.
• At least 4% BWOB barium salts take retarding effect in sodium silicate activated blast furnace slag/carbonatite.
• a higher dosage of retarders is needed to achieve better coverage of the protecting layers and however, usually causes significant reduction of compressive strength of a hardened product.
• the extent of the coverage of the protecting layers depends significantly on the surface charge of pozzolanic particles. Though the surface charge of blast furnace slag can be negative, the surface charge for fly ash can be positive in the solution. Therefore, with the“Protecting Layers” method, the efficiency of the retarding effect may differ significantly among different reactive aluminosilicate sources.
• disclosed embodiments provide efficient inorganic retarding admixtures to regulate thickening and setting times of a geopolymer composition that can be applied as a well cementing grout, mortar and concrete.
• a geopolymer composition comprises: (i) at least one Low-Ca Class F fly ash having less than or equal to 8 wt.% of calcium oxide; (ii) at least one High-Ca aluminosilicate selected from the group of blast furnace slag, Class C fly ash, vitreous calcium silicate, and kiln dust; (iii) a retarding solution; and (iv) an aqueous alkali silicate activator.
• the disclosed retarder solution is made by dissolving at least one soluble metal salt in water where at least one soluble metal salt is selected from 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.
• At least one metal salt is dissolved in the retarder solution and the retarder solution contains about 0.1 to about 10% metal salts BWOB.
• the metal salt is barium chloride dihydrate.
• the dosage of barium chloride dihydrate is from about 0.10 to about 5% BWOB, and more preferably from about 0.5% to about 2.5% BWOB.
• a soluble barium salt is dissolved in water.
• the retarder solution is mixed with an alkali silicate activator solution before mixing the activator solution with all other ingredients.
• the retarder solution and the activator solution are added separately at the time when mixing with the dry ingredients.
• the alkali silicate activator solution may comprise metal hydroxides and metal silicates wherein the metal is potassium, sodium or combinations of both.
• a disclosed embodiment provides a geopolymer composition including: (i) at least one High-Ca aluminosilicate selected from the group of BFS, CFA, vitreous calcium silicate, and kiln dust; (ii) a retarder solution; and (iii) an alkali silicate solution.
• a geopolymer composition includes (i) at least one High-Ca aluminosilicate selected from the group of BFS, CFA, vitreous calcium silicate, and kiln dust; (ii) metakaolin; (iii) a retarder solution; and (iv) an alkali silicate solution.
• the geopolymer composition further includes fine and/or coarse aggregates, superplasticizer or fiber to manufacture mortar and concrete for construction applications.
• High performance and ultrahigh performance concrete compositions whose set times can be regulated by an inorganic retarder.
• High performance and ultrahigh performance concrete compositions comprise: (i) Blast furnace slag; (ii) Metakaolin; (iii) a retarding solution; and (iv) an aqueous alkali silicate activator, (v) at least one aggregate; and (vi) at least one micron/submicron filler.
• An objective of the present disclosure is to provide an effective retarding admixture to regulate setting times of a geopolymer composition that can be applied as well cementing, mortar and concrete.
• the present disclosure provides an efficient retarding method to control setting of geopolymer systems containing High-Ca FFA or High- Ca aluminosilicate.
• Low-Ca FFA based geopolymers set and harden very slowly and have a low final strength if cured at low temperatures (e.g., room temperature) due to the fly ash’s low reactivity in the alkaline solution.“Reactivity” is herein defined as the relative mass of a binder pozzolan that has reacted with an alkaline solution. Fly ashes with smaller particle sizes are usually more reactive, such as ultrafine fly ash (UFFA) with a mean particle size of about 1 to 10 mpi. UFFA is carefully processed by mechanically separating the ultrafine fraction from the parent fly ash.
• UFFA ultrafine fly ash
• UFFA can also reduce the w/b ratio for a desirable workability, e.g., slump and yields a hardened geopolymer with better performance.
• Coal gasification fly ash is discharged from coal gasification power stations, usually as Si(3 ⁇ 4-rich, substantially spherical particles having a maximum particle size of about 5 to 10 mpi. To make use of less reactive fly ashes, a second binder that is much more reactive is required to produce settable geopolymer products at ambient temperatures. [0056] Alkali activation of metakaolin yields a typical geopolymer gel that possesses a reasonably long set time, e.g., 2 to 6 hours.
• the resulting geopolymer composition may not require a retarding admixture.
• alkali activation of BFS, CFA, CKD or VCAS yields essentially CSF1 and/or CASF1 gels.
• Quick precipitation of CSF1 and/or CASF1 shortens setting times and increases the rate of strength gain as well as the final strength of the product.
• the second binder is a Fligh-Ca aluminosilicate pozzolan, the setting behavior of the resulting geopolymer system will be significantly modified.
• BFS High-Ca aluminosilicate pozzolans
• the Low-Ca FFA can be a fly ash which comprises less than or equal to about 8 wt.% of calcium oxide.
• the classification of fly ash is based on ASTM C618, which is generally understood in the art.
• the Low-Ca FFA comprises less than or equal to about 5 wt.% of calcium oxide.
• the fly ash should contain at least 65 wt.% amorphous aluminosilicate phase and have a mean particle diameter of 60 pm or less, such as 50 pm or less, such as 45 pm or less, such as 30 pm or less.
• the Low-Ca FFA has a Loss On Ignition (LOI) less than or equal to 5%.
• the Low-Ca FFA has a LOI less than or equal 1%.
• a Low-Ca FFA based geopolymer composition comprises: (i) at least one Low-Ca Class F fly ash having less than or equal to 8 wt.% of calcium oxide; (ii) at least one High-Ca aluminosilicate selected from the group of blast furnace slag, Class C fly ash, vitreous calcium silicate, and kiln dust; (iii) a retarding solution; and (iv) an aqueous alkali silicate activator.
• the retarder solution is made by dissolving a soluble metal salt in water where a soluble metals salt is selected from barium chloride, barium chloride dehydrate, barium nitrate, barium nitrite, barium metaborate monohydrate, barium nitrate hydrate, zinc nitrate, zinc chloride, zinc sulfate, strontium chloride, strontium nitrate and strontium sulfate. Soluble barium salts are preferred.
• the Low-Ca FFA based geopolymer compositions further include metakaolin; in one embodiment, the geopolymer compositions further include fine and coarse aggregates to manufacture concrete products.
• One embodiment provides a High-Ca aluminosilicate based geopolymer composition including: (i) at least one High-Ca aluminosilicate selected from the group of High-Ca FFA, BFS, CFA, vitreous calcium silicate, and kiln dust; (ii) a retarder solution; and (iii) at least one alkali silicate solution.
• the High-Ca aluminosilicate is a High-Ca FFA; In one embodiment, the High-Ca aluminosilicate is BFS; and in another embodiment, the High-Ca aluminosilicate is CFA.
• the High-Ca aluminosilicate based geopolymer composition further includes at least one Low-Ca aluminosilicate pozzolan selected from the group: Low- Ca FFA and metakaolin.
• a High-Ca aluminosilicate based geopolymer composition further includes fine and coarse aggregates to manufacture concrete products.
• the geopolymer compositions further include fine and/or coarse aggregates to manufacture concrete products.
• US Pat. No. 9,090,508 discloses geopolymeric compositions for high performance and ultrahigh performance concrete.
• very reactive aluminosilicate materials must be used as the binder, such as m eta kaolin and blast furnace slag; the w/b ratios much be small, e.g., near minimum; the packing density of particulates must be high to minimize the product’s porosity and no coarse aggregates greater than 10mm should be used to favor homogeneity. Therefore, set times of fresh concretes are relatively short particularly when a large amount of blast furnace slag is used in the formulations.
• the compositions disclosed in US Pat. No. 9,090,508 are essentially blast furnace slag/metakaolin based binary geopolymers.
• High performance and ultrahigh performance concrete compositions whose set times can be regulated by an inorganic retarder.
• High performance and ultrahigh performance concrete compositions comprise: (i) Blast furnace slag; (ii) Metakaolin; (iii) a retarding solution; and (iv) an aqueous alkali silicate activator, (v) at least one aggregate; and (vi) at least one micron/submicron filler.
• the retarder solution is prepared by dissolving at least one soluble metal salt in water where at least one soluble metals salt is selected from barium chloride, barium chloride dehydrate, 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 and strontium sulfate.
• Any soluble metal salt that hydrolyzes in the alkaline solution and is able to co-precipitate silicate species that are present originally in the alkali silicate activator solution could be used as an inorganic retarding admixture.
• the retarding effect depends on the type of metals as well as dosage. Metal-silicate interactions are expected to increase with increasing dosage or molar metal to silicate ratio. The metal- silicate interactions should be not excessive. If the interactions are overwhelming, release of silicate species to the geopolymer system will be greatly hindered during subsequent curing process and thus the early compressive strength of the product will be affected significantly. Among all these metal salts, barium salts are preferred.
• At least one metal salt is dissolved in water.
• the retarder solution is mixed with an alkali silicate activator solution before mixing of all the ingredients.
• the alkali silicate activator solution combined with the retarder solution is poured into the mixer containing all the dry ingredients.
• the retarder solution and the activator solution are added separately at the time when mixing with the dry ingredients to manufacture geopolymer products.
• the retarder solution is mixed with an alkali silicate activator solution for approximately 30 minutes before mixing with all other ingredients.
• the retarder solution is mixed with an alkali silicate activator solution for approximately 10 minutes before mixing of all the ingredients.
• the retarder solution is mixed with an alkali silicate activator solution for approximately 24 hours before mixing of all the ingredients.
• the retarder solution is added to the concrete during mixing in a ready mix truck. In this case, the retarder solution serves as a set brake to prevent the mixing concrete from hardening in a ready mix truck during transportation to the job site, e.g., in an emergency.
• At least one metal salt is included in the retarder solution and the retarder solution contains about 0.1 to about 10% metal salts BWOB.
• the metal salt is barium chloride dihydrate.
• the dosage of barium chloride dihydrate is from about 0.10 to about 5% BWOB, and more preferably from about 0.5% to about 2.5% BWOB.
• the metal salt is barium metaborate monohydrate; in one embodiment the retarder solution contains barium chloride dihydrate and zinc nitrate; in one embodiment the retarder solution contains strontium nitrate and zinc chloride.
• a new method is provided to use metal salts to control set times of alkali activated materials or geopolymers by controlling release of silicate species in the activator solution that are available for nucleation and growth of CSH and/or CASH gels at early curing time.
• Select embodiments conducted experiments to study the co-precipitation process of silicate with hydrolyzed barium chloride in the sodium silicate activator solution by Raman Spectroscopy. In one series of testing, Raman spectra of supernatant liquids and the precipitates were monitored with increasing dosage of barium chloride after mixing barium chloride dehydrate solution with the sodium silicate solution for 0.5 hours.
• Sodium hydroxide beads (99% purity) were dissolved in DI water and combined with Type Ru sodium silicate solution from PQ Corp to prepare a sodium silicate activator solution.
• Barium chloride dehydrate (99% purity) was dissolved in DI water separately.
• the compositions of the activator solutions are shown in Table 1. Molar concentration of NaOH was fixed at 5 and mass ratio of Si(3 ⁇ 4/Na 2 C) was 1.25 throughout Examples 1 to 4.
• the activator solution used for testing was a part of a High-Ca FFA geopolymer composition and dosages of barium chloride dehydrate were expressed as by weight of the fly ash binder.
• a single grating spectrograph - notch filter micro-Raman system was used to gather the Raman spectra.
• a Melles-Griot Model 45 Ar + laser provided the 5145 A wavelength incident light that was directed through a broad band polarization rotator (Newport Model PR-550) to the laser microscope that guided the laser light to the precipitated solids or the solution in a 25 ml transparent vial through a long working distance Mitutoyo 10 microscope objective.
• the laser light power was approximately 22 mW at the sample.
• the scattered light was directed through an analyzer polarizer and the scattered light proceeded through a 150 pm aperture, and then to holographic notch and super-notch filters (Kaiser Optical Systems).
• the spectrograph used a 1200 gr/mm grating (Richardson Grating Faboratory).
• the incident slits of the JY-Horiba HR460 spectrograph were set to 6 cm 1 resolution to collect spectra from 50 to 1600 cm 1 .
• the spectrograph was frequency calibrated using CC14, so that the recorded frequencies are accurate to within ⁇ 1 cm 1 .
• Parallel-polarized (VV) spectra were collected where the incident laser light was vertically polarized.
• FIG. 1 presents Raman spectra of the supernatant samples of the sodium silicate solutions after mixing with barium chloride solution for 0.5 hours at four dosages of barium chloride dehydrate.
• the spectrum for the activator solution without retarder (RM-BC-0) shows clearly that the activator solution is dominated by the Q , Q , and Q type silicate species.
• the Q° type silicate species is fully dissociated (FIG. 1).
• All the supernatant solutions for the samples with barium chloride dihydrate (Table 1) contain practically no silicate species, even at a very low dosage with a molar Ba/Si of 0.04 (RM-BC 0.875).
• FIG. 2 presents Raman spectra of the co-precipitated solids after mixing with barium chloride solution with the activator solution for 0.5 hours at three dosages of the retarder.
• the co-precipitated sample with the lowest dosage of the retarder shows a sharp Raman spectrum pattern where a new vibration band occurs at 1062 cm 1 in addition to the bands associated with the Q°, Q 1 and Q 2 type silicate species.
• the 1062 cm 1 band can be assigned to the Q silicate species. Comparing this Raman spectrum with the one for the activator solution without the retarder (FIG.
• Ground granulated blast furnace slag grade 120 (NewCem Slag cement) was from the Lafarge-Holcim’ s Sparrow Point plant in Baltimore, MD. Activity index was about 129 according to ASTM C989.
• the blast furnace slag contained about 38.5 % CaO, 38.2 % Si0 2 , 10.3% AI2O3, and 9.2% MgO with a mean particle size of 13.8 pm and 50 vol% less than 7 pm.
• Metakaolin (Kaorock) was from Thiele Kaolin Company, Sandersville, GA.
• the metakaolin had a particle size between 0.5 and 50 pm with 50 vol% less than 4 pm.
• Silica fume an industrial waste product from Fe-Si alloying, was from Norchem Inc.
• the silica fume contained 2.42 wt.% carbon.
• the silica fume was used to prepare activator solutions by dissolving silica fume in alkali hydroxide solution, or added as submicron reactive filler in preparing ultrahigh performance concrete samples.
• Bluestone #7 (AASHTO T-27) was used as coarse aggregate. To reach a saturated surface dry (SSD) condition, the dry aggregate was immersed in water for 24 hours, and then the free water was manually removed from the aggregate surface using a dry cloth. River sands either in SSD or oven dry condition was used. A Trident moisture probe (model T90) was used to determine the moisture content of a fine aggregate sample. A Min U-SIL® crushed quartz powder from U.S. Silica was used to prepare ultrahigh performance concrete. The quartz powders have a particle size between 1 to 25 pm with a median diameter of about 5 pm.
• Type Ru sodium silicate solution from PQ, Corp was used to prepare alkali silicate activator solution.
• the mass ratio of Si(3 ⁇ 4/Na 2 0 was about 2.40.
• the solution as received contains about 13.9 wt.% Na 2 0, 33.2 wt.% Si0 2 and 52.9 wt.% water.
• Sodium hydroxide beads (99% purity) and potassium hydroxide flakes (91% purity) were used for preparing alkali activator solution.
• Geopolymer samples with high-Ca Class F fly ash from Jewett Power Station, Texas, USA were prepared. The mix compositions were shown in Table 3 and ingredients were shown in grams. The batch size was about 5000 grams. The Jewett fly ash contained about 12.2 wt.% CaO.
• the geopolymer samples from Example #1 and 2 were prepared with the retarder sodium hexa-metaphosphate (SHMP) for a comparison. Sodium phosphate was disclosed in prior art or in the literature as a retarder. The dosage of SHMP was 1.50% and 2.25% BWOB, respectviely.
• the geopolymer samples from Example #4 to #7 were prepared with the retarder barium chlorie dihydrate at dosages of 0.50% to 1.00 wt.% BWOB to demonstrate the efficiency of retading.
• NaOH beads (99% purity) were dissolved in water and the resulting solution was then combined with Type Ru sodium silicate solution to prepare the activator solution.
• the retarder solution was mixed for 2 hours and then poured into Jewett fly ash in a high intensive K-Lab mixer (Kercher Industries) for 6 minutes.
• the obtained fresh pastes were immediately transferred into molds (3” high and 40 mm high), followed by treating on a vibrating table for about 1 minute to remove entrapped air bubbles.
• the fresh pastes were determined for initial and final set times with a Vicatronic Automatic Vicat instrument (Model E004N), hereafter called AutoVicat according to ASTM
• the initial set time for the control sample (Example 3, BCOO) was determined to be 29 minutes and the final set time was 45 minutes. Adding 0.50% BWOB of barium chloride dihydrate, the initial set time was increased to 47 minutes and the final set time to 78 minutes (Example 4). Increasing barium chloride dihydrate to 0.75% BWOB, the initial set time was increased to 68 minutes and the final set time to 99 minutes (Example 5). Increasing barium chloride dihydrate to 0.875% BWOB, the initial set time was increased to 114 minutes and the final set time to 144 minutes (Example 6).
• the activator solution without barium chloride dihydrate (Example #8) was poured into the FFA/BFS/sand mixture and mixed for 5 minutes at an intermediate speed.
• the fresh mortar was measured for set times with an AutoVicat accordimng to ASTM C191. The initial set time was 114 minutes and the final set time was 186 minutes.
• the retarder solution was mixed with the activator solution for 30 minutes before preparing the geopolymer mortar sample (Example 9).
• the fresh mortar was measured for set times with an AutoVicat accordimng to ASTM C 191. The initial set time was 249 minutes and the final set time was 348 minutes.
• the retarder solution was added at the time the activator solution was poured to the dry ingredient mixture (Example 10). The mixture was mixed for 5 minutes. The fresh mortar was measured for set times with an AutoVicat accordimng to ASTM C191. The initial set time was 236 minutes and the final set time was 342 minutes.
• the activator solution without barium chloride dihydrate (Example #11) was poured into the FFA/BFS/sand mixture and mixed for 5 minutes at an intermediate speed.
• the fresh mortar was measured for set times with an AutoVicat accordimng to ASTM C191.
• the initial set time was 59 minutes and the final set time was 144 minutes.
• the compressive strength was 4081 psi after curing for 7 days and was increased to 8032 psi after curing for 28 days.
• the retarder solution was mixed with the activator solution for 30 minutes before preparing the geopolymer mortar sample (Example 12).
• the fresh mortar was measured for set times with an AutoVicat accordimng to ASTM Cl9l. The initial set time was 136 minutes and the final set time was 198 minutes.
• the compressive strength was 3673 psi after curing for 7 days and increased to 7734 psi after curing for 28 days.
• the retarder solution was added at the time the activator solution was poured to the dry ingredient mixture (Example 13). The mixture was mixed for 5 minutes. The fresh mortar was measured for set times with an AutoVicat accordimng to ASTM C191. The initial set time was 114 minutes and the final set time was 180 minutes. The compressive strength was 4064 psi after curing for 7 days and increased to 7970 psi after curing for 28 days.
• the activator solution was then poured into the MK/BFS blend and mixed for 3 minutes at about 350 rpm. Then dry river sand (50 wt.%) and quartz powder (10.00 wt.%) were added to the mixture and continued mixed for 3 minutes. Toward ending of mixing, silica fume (2.00%) was added and continued mixing for 3 minutes.
• the resulting paste was determined for initial set time with an AutoVicat or with a manual Vicat device.
• the paste was poured into 2”x4” cylindrical molds and cured at room temperature. Compressive strength was measured after curing for 28 days on a Test Mark CM-4000-SD compression. The compression machine was calibrated against the NIST Traceable standards.
• the initial set time was estimated about 30 minutes and the compressive strength was about 19972 psi after curing for 28 days.
• 1 wt.% BWOB of barium chloride dihydrate was added (Example 15)
• the initial set time was 54 minutes and the compressive strength was about 20146 psi after curing for 28 days.
• 2 wt.% BWOB of barium chloride dihydrate was added (Example 16)
• the initial set time increased to 89 minutes and the compressive strength was about 19424 psi after curing for 28 days.
• GUHPC samples m eta kaolin (5.92 wt.%) and ground granulated blast furnace slag (15.28 wt.%) were mixed in a high intensive mixer (K-Lab, Kercher Industries).
• An activator was prepared by mixing Na 2 0 (1.08 wt.%) as NaOH, K 2 0 (2.47 qt% wt.%) as KOH, Si0 2 (3.80 wt.%) as silica fume, and water (9.45 wt.%).
• Silica fume was dissolved in the alkali hydroxide solution and the resulting activator solution was aged for a week before use.
• the activator solution was then poured into the MK/BFS blend and mixed for 3 minutes at about 350 rpm. Then dry river sand (50 wt.%) and quartz powder (10.00 wt.%) were added to the mixture and continued mixing for 3 minutes. Toward ending of mixing, silica fume (2.00%) was added and continued mixing for 3 minutes.
• the resulting paste was determined for initial and final set times with a manual Vicat device. The paste was poured into 2”x4” cylindrical molds and cured at room temperature. Compressive strength was measured after curing for 28 days.
• Examples 19 and 20 demonstrate the efficiency in control of setting using a soluble barium salt in geopolymer concretes.
• the mix composition for both concrete samples contained 78.75 wt.% aggregates with the mass ratio of coarse to fine of 1.74.
• the binder contained 80% of Low-CaO FFA and 20% of blast furnace slag.
• the w/b ratio was 0.47
• molar NaOH concentration was 5.7
• mass ratio of Si0 2 /Na 2 0 was 1.15 for the activator solution.
• To prepare geopolymer concrete samples the Low-CaO FFA from Neilsens Group, Australia, blast furnace slag from Fafarge- Holcim, and river sand (SSD condition) were mixed for 3 minutes in a high intensive mixer (K-Fab, Kercher Industries). NaOH beads were dissolved in water and the resulting solution was then combined with Type Ru sodium silicate solution to prepare the activator solution. The activator solution was left overnigh 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. Then SSD coarse aggregate (Grade #7) was added and mixed for 5 minutes at a low mixing speed (e.g., 20 rpm).
• the fresh concrete was sieved to obtain mortar sample that was measured with an Acme Penetrometer for set times according to ASTM C403.
• the fresh concrete was also poured into 3”x6” cylidrical moulds and vibrated for 1 minute on a vibratio table. The samples were capped on and cured at room temperatures until compressive strength was measured. The initial set time was 75 minutes and the final set time was 168 minutes.
• the compressive strength after curing for 7 days was 4509 psi and increased to 7992 psi after curing for 28 days.
• Example 20 additional concrete samples with a retarder were prepared (Example 20). Barium chloride dihydrate was dissolved in water separately. The dosage of retarder was 1.00% BWOB. The retarder solution was mixed for 30 minutes with the activator solution before preparing fresh concrete sample. The fresh concrete was sieved to obtain mortar sample for set times with an Acme Penetrometer according to ASTM C403. The initial set time was 313 minutes and the final set time was 572 minutes. The compressive strength was 3707 psi after curing for 7 days and 7259 psi after curing for 28 days.
• Example #8 The same mix composition without the retarder solution as in Example #8 was mixed for 30 min and then the retarder solution (3% barium chloride BWOB) was poured into the paste while mixing and was additionally mixed for 10 min. After mixing was stopped, the mortar sample was subject to ASTM C191 for set time determination. At about 7.4 hours after pouring the activator solution into the dry mixture, the mortar sample did not show any sign of setting, indicating that the retarder did delay setting efficiently.
• the retarder can be used for emergency set brake of a fresh geopolymer concrete that is in transportation in a ready mix truck.

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