RO137964A2 - Manufacturing process and lining elements made of cement-free alkali-activated geopolymer micro concrete - Google Patents

Abstract

The invention relates to a process for manufacturing a cement-free alkali-activated geopolymer micro concrete and to lining elements made of said concrete, to be used in lining outer or inner walls or other vertical or inclined elements thereof. According to the invention, the process comprises the following stages: preparing a dry mixture of 40% by mass, at the most, of F-class power plant ash with a fineness, as sieve residue, of 0.045 mm and natural river aggregates with a maximum granulation of 4 mm, with disperse reinforcement of metallic fibres, an alkali activator consisting of a Na2SiO3 solution and NaOH solution, in various molar concentrations, at a mass ratio in the range of 0.5...2.5, so that the metallic fibers content in the composite mass ranges between 5...15 kg/m3 of binder, gravimetrically dosing the dry mixture and the alkali activator so as to achieve an alkali activator : power plant ash ratio ranging between 0.5...1.0, preparing the geopolymer micro concrete, by mixing the dry mixture with the alkali activator, in a mixer, for 5...10 min, the resulting composite is poured in specific moulds where it is vibrated for 3...5 min and then it is subjected to a heat treatment at a temperature ranging between 50...80°C, for 4...48 h, followed by dismantling, trimming and storage. The lining elements, as claimed, have variable shapes and sizes, with a maximum side size of 500 ± 5mm and a minimum thickness of three times the size of the biggest grain of natural aggregates, and the following physical-mechanical characteristics, 7 days after casting: dry-state fingerprint density in the range of 1500...2000 kg/m3, water absorption of 8% at the most, good freeze-thaw resistance and resistance to environment factors and to usually employed cleaning solutions.

Description

Manufacturing process and cladding elements from alkaline-activated geopolymer microconcrete, without cement content

The invention refers to a Manufacturing process and cladding elements from alkaline activated geopolymer microconcrete, without cement content, using as raw materials power plant ash available in Romania, an alkaline activator based on sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) and natural river sort aggregates with a maximum size of 4 mm, intended for the production of cladding elements of external or internal walls of buildings or other inclined or vertical elements thereof.

following the Production process and cladding elements from alkaline activated geopolymer microconcrete, without cement content, finished elements are obtained, in the form of plates, dispersedly reinforced, intended for use in the creation of finishes in the form of coatings by cladding the surface of external or internal walls of constructions or other inclined or vertical elements thereof.

Alkaline-activated geopolymer microconcrete cladding elements without cement content are prefabricated elements, ready to be put into operation, whose structure consists of a geopolymer binder matrix in which natural river aggregates with a maximum grain of 4 mm are embedded and dispersed reinforcement with metallic fibers. depending on the molding pattern used, the cladding elements can be flat on the exposed (external) face or have different profiles / designs.

The main peculiarity of the Alkaline-activated geopolymer microconcrete production process and cladding elements, without cement content, is the use of local raw materials, alkaline-activated power plant ash and natural aggregates of Romanian origin.

basically, the raw materials used for the production of geopolymeric microconcrete are power plant ash, alkaline activator, natural river aggregates and metal fibers for dispersed reinforcement. The alkaline activator is a solution made by quantitatively controlled mixing of sodium silicate solution Na2SiO3 and a solution of sodium hydroxide NaOH.

As Davidovits showed as early as 1979, the matrix of the geopolymer binder is based on a Si-O-Al-O structure, by alternating tetrahedra of S1O4 and AIO4, joined together in three directions with all oxygen atoms, calling them geopolymeric materials ( Davidovits, 1979). in a simplified method, it can be stated that geopolymers can be synthesized by alkaline activation of materials that are rich in S1O2 and Al2O3 (Al Bakri Abdullah et al., 201 lb).

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The supply of oxides required for the production of the geopolymer binder of each individual material is shown in figure 1. The natural river aggregates form a skeleton covered in the geopolymer binder matrix.

The empirical formula for the entire geopolymerization process of the binder is (Davidovits, 1988):

Mn{-(SiO2)z-AlO2}n,wH ₂ O (1) where: M - represents the alkaline element, which can be: K (potassium); Na (sodium); Ca (calcium);

The symbol indicates the presence of a link;

n - represents the degree of polycondensation (or polymerization);

z - is 1, 2, 3 or greater, up to 32;

w - represents the number of bound water molecules.

Power plant ash * SiO ₂

Sodium silicate * A1 ₂ O ₃

Sodium hydroxide ----- — -4 Na ₂ O

Water-------------'** H ₂ O

Fig. 1. The origin of the molar elements that compose the alkaline activated geopolymer paste when the two components of the geopolymer material (the reactive solids and the alkaline solution) react, an alumino-silicate network is formed, resulting in a hard, water-resistant product (Duxon et al ., 2007). The geopolymerization reaction can also be expressed chemically according to the series of chemical equations (2).

2SÎOj AljO, + 3 OH“+ 3 H _? O ™—* 2 [Al(OH)JT* [StO^OH).] ^2- , -HjO

[AI(OH)J-*(SrO ₂ (OH) ₂ f----—►

HCţ O

HO O' polycondensa bon

(2)

Geopolymerization reaction (Duxon et al., 2007) these materials are currently under development, research being encouraged mainly by the need to reduce CO2 emissions globally. Having excellent mechanical properties and resistances in aggressive environments, these materials represent an opportunity for both

environment as well as for engineering, an alternative to traditional technology (Lloyd and Rangan, 2010). However, it must also be taken into account that the production of activators based on sodium silicate or sodium hydroxide produces emissions that are not of the type of "greenhouse gases" (SOx, NOx, phosphates, etc.), but can become problematic if the development of rigorous methods of their production is not continued (Herbert et al., 2011).

Worldwide, research on alkaline-activated geopolymer materials exists, but their implementation differs greatly, due to factors that greatly influence this type of binding material. The parameters that influence the final characteristics of the geopolymer binder are:

- Physico-chemical characteristics of power plant ash

- The properties of the alkaline activator

- The ratio between Na2SiC>3 Solution and NaOH Solution

- Ratio of alkaline activator to source material

- The ratio between solid raw materials and water

- Thermal treatment parameters

The large amount of thermal power plant ash resulting from the combustion of coal for the production of electricity, in Romania, can create new opportunities for the realization of this type of innovative materials, with satisfactory durability and with a low negative impact on the environment. in Romania there are many thermal power plants whose ash, resulting as a by-product/waste, could be exploited for the production of geopolymer concrete based on power plant ash (Figure 2).

Fig. 2. The geographical distribution of power plants in Romania (CEPROCIM, 2009) in the invention patent number R000121965, an invention is mentioned regarding an ecological cement composition with a content of 35-40% power plant ash. This material differs from the geopolymer binder that is the subject of this request in that it has a cement content of 6-8% and an aqueous ester solution of a modified resin, resulting from conifers of 0.180.22 1 and is intended for the realization of hydrotechnical road constructions .

in the patent number R000123502 an invention is mentioned regarding a composition for polymeric macroporous concrete intended for civil and industrial constructions. The composition of the polymeric macroporous concrete consists of polymer aggregates in the form of cubes with sides of 25 mm, 15 mm and 10 mm, and in the form of spheres with a diameter of 3 mm, mineral aggregate, with a grain size of 0, 05...0 , 1 mm, mineral binder, acrylic resin, bisphenolic epoxy resin, hardener and water, which clearly differentiates it from the geopolymer microconcrete that is the subject of this request.

in the invention patent with the number RO00125903, an invention is mentioned regarding a composition and a process for obtaining a cement-polymer mixture as well as a process for applying the composition to paving roads and highways. This cement-polymer mixture is clearly different from the geopolymer microconcrete that is the subject of this request because it uses power plant ash as raw materials but also cement, carbon black and zinc oxide, and the field of use is totally different.

in the invention patent with the number R000106126, an invention related to a process for obtaining concrete products based on thermal power plant ash is mentioned. The content of calcium chemical activator and glass fiber waste, as well as the hardening carried out at 15 °C - 30 °C and humidity of 70 - 100% or by greenhouse effect differentiates this process from that of making alkaline activated geopolymer microconcrete, without cement content that is the subject of this request.

in patent number EP2852562, published also under numbers UAa201413803, CA2874234, CN104781209, US20150321960, AU2013264456, DK2852562, BR112014029174, ES2625015, ID2015/01680, MYPI 2014003224, IN2396/MUMNP/2014, PT2852562,

WO2013/176545 mentions an invention related to a geopolymer material, but which in its composition contains sugar, its derivatives, organic acids and salt.

In the patent number EP2951133, published also under the numbers KR1020150118969, US20150376060, RU2015133906, ID2017/00351, TH160513,

BR112015018590, IN2336/KOLNP/2015, RU0002664723, WO2014/118242, mentions an invention relating to a fire-resistant geopolymer material, but made with magnesium-based compounds.

in the invention patent with the number US09290416, an invention is mentioned regarding a process for making a geopolymer material based on thermal power plant ash, but the principle of making it is based on the method of theoretical calculation of the composition. A similar process is presented in patent number W02005049522, also published under numbers ZA2006/04360, EP1689691, US20070125272, CN1882516, CA2545407, NZ547756, AU2004290614, IN131 l/KOLNP/2006, EP 1689691, whose main difference from the proposal shown is the content of 40-60% aggregates, and the alkaline activator may contain a silicate of the alkaline-earth metals, not necessarily sodium silicate.

in the invention patent with the number CN 106630903, an invention is mentioned regarding geopolymer concrete whose composition includes thermal power plant ash and slag but intended for the execution of foundations with high durability.

in the invention patent with the number WO2011135584, also published under the number IN1365/MUM/2010, an invention is mentioned regarding an alkaline activated geopolymer material, but in the composition of which calcium hydroxide and Portland cement are also found.

in the invention patent with the number IN1830/CHE/2015, an invention is mentioned regarding a geopolymer material but based on alkaline activated hearth ash (fatty ash), with hardening at normal temperature, without heat treatment.

in the invention patent with the number CN 104529300, an invention is mentioned regarding a geopolymer material containing glass powder, slag, kaolin, zinc oxide, titanium dioxide, etc.

in the invention patent with the number IN6203/DELNP/2011, also published under the numbers EP2385966, US20110271876, CN102325736, W02010/079414, an invention is mentioned regarding a geopolymer material, but which in its composition contains blast furnace slag and bauxite.

in the invention patent with the number NZ707001, published also under the numbers US20150321954, AU2013344816, WO2014/075134, an invention related to a geopolymer material, but which also contains sodium carbonate in its composition, is mentioned.

in the invention patent with the number CN103172295, an invention related to a geopolymer material is mentioned, but which in the composition of the activator contains triethanolamine, a naphthalene water reducer, quartz powder and milk of lime.

in the invention patent with the number IN7105/CHE/2015, an invention related to a geopolymer material is mentioned, but which in its composition contains sand with a controlled granulometric curve, without dispersed reinforcement.

in the invention patent with the number CN 109437701, an invention related to a geopolymer material is mentioned, but which also contains clay and cristobalite powder in its composition.

the invention patent number CN106336158 mentions an invention related to a geopolymer material, but which in its composition also contains mineral waste powder, ultrafine silica, water reducing agent and aggregates.

in the invention patent with the number CN106082927, an invention related to a geopolymer material is mentioned, but which in its composition also contains slag, micro-powder from construction waste and sodium hydroxide powder.

patent number JP2016005994 mentions an invention related to a geopolymer material, but which in its composition also contains blast furnace slag and ultrafine silica.

patent number RU0002599742 mentions an invention related to a geopolymer material, but which in its composition also contains potassium hydroxide and ultrafine silica, and the alkaline activator also contains potassium silicate.

patent number WO201603 0904 mentions an invention related to a geopolymer material, but which in its composition does not contain sodium hydroxide, instead it contains blast furnace slag.

in the invention patent with the number RU0002517729, an invention related to a geopolymer material is mentioned, but which in its composition contains a gelation enhancing additive based on clay minerals (montmorillonite), and the heat treatment temperature is in the range of 25°C -75 °C.

in the invention patent with the number IN201841008645, an invention related to a geopolymer material is mentioned, but which in its composition contains furnace slag, nanosilica, sea water and marble dust.

in the invention patent with the number CN101891498, an invention related to a geopolymer material is mentioned, but which in its composition contains aluminum dust.

in the invention patent with the number IN201737001848, published also under the numbers AU2015303826, US20170204008, CN107074651, W02016/023073, an invention is mentioned regarding a geopolymer material, but which in its composition contains either power plant ash or an aluminum phyllo-silicate as a substitute of it.

in the invention patent with the number W02014141051, published and under the number EP2970003, an invention is mentioned regarding a cellular geopolymer material, with an apparent density of 400 kg/m ³ - 1200 kg/m ³ and a compressive strength 28 days after casting of 3 - 17 MPa and which in the composition contains Portland cement, furnace slag, meta-kaolin, furnace dust, pozzolanic aluminosilicates rich in calcium oxide and gelling agent.

in patent number WO2012083255, published also under numbers CA2821512, EP2651846, JP2013545714, MX342948, RU2013132983, KR1020140010018, RU0002599742, BR112013014685, VN35844 ΊΉ147136, CN107265937, IN5571/CHENP/2013, EG27474 mentions an invention relating to a geopolymer material, but which in the composition contains pozzolanic additive, nanosilica, and the heat treatment temperature is 90-150 °C.

in the invention patent number IN9721/DELNP/2014, published also under the numbers UAa201412514, CA2871577, CN104245621, EP2841390, JP2015514675, KR1020150006855, RU2014146785, NZ702224, AU2013252 686, RU0002622263, BR112014025056, MYPI 2014703079, W02013/163010, an invention relating to to a geopolymer material, but which also contains calcium sulfate in its composition.

in the invention patent with the number CN106854045, published also under the numbers CN106854072, CN106854059, an invention is mentioned regarding a method of making a geopolymeric material which, however, uses slag and recycled aggregates.

in patent number US20180015515, published also under numbers SG11201607307Q, MYPI 2017702815, CA2976409, CN107249765, KR1020170116086, PH1/2017/501408, ID2018/01002, WO2016/1 28994, mention is made of an invention relating to a method of making the elements of paving using municipal waste. The main difference from the present request is the realization of a geopolymer using not the thermal power plant ash, but the ash resulting from the burning of municipal solid waste.

in the invention patent with the number IN201841049049, an invention is mentioned regarding a method of making paving elements from geopolymeric material, but they refer to the test and admissibility conditions according to IS 15658:2006, more permissive in terms of limits of acceptability and which provides for testing 28 days after pouring, and blast furnace slag is used in the composition of the geopolymer.

in the invention patent with the number US20100058957 an invention is mentioned regarding a method of making a geopolymeric material, which can be used in the manufacture of paving elements, but in its composition using recycled aggregates and the alkaline activator and may contain hydroxides, carbonates , aluminates, silicates of alkaline earth metals or combinations thereof.

Although in the documents presented above there are common elements with Production process and cladding elements from alkaline activated geopolymer microconcrete without cement content - generally the presence of power plant ash and the use of its alkaline activation method, none of them refers to a product or process for obtaining a geopolymer microconcrete using exclusively thermal power plant ash available in Romania, and each of the previously presented has at least one particularity that differentiates them. As previously presented, the general characteristics, the oxide composition and the fineness of the power plant ash, as well as the technological stages of preparation of the alkaline activator are essential for the realization of the geopolymer binder, respectively the finished product - the geopolymer microconcrete cladding element, and clearly differentiate the process from production of the alkaline-activated geopolymer microconcrete, without cement content, which is the subject of this request, in relation to the documents presented and analyzed above.

The purpose of this invention is to offer, using local materials from Romania, a complete and environmentally friendly solution for the production of cladding elements from alternative construction materials, with a low impact on the environment by applying the circular economy concept for power plant ash that from - an industrial by-product becomes a raw material in the design and production of alkaline activated geopolymer materials, thus preventing its conversion into landfilled waste.

The innovativeness of this invention consists in the valorization of local materials through the development of new compositions of alkaline activated materials based only on thermal power plant ash and the specific design of compositions suitable for the realization of prefabricated elements for cladding with physical-mechanical characteristics satisfying the intended field of use.

The problem solved by this Process for making cladding elements from alkaline activated geopolymer microconcrete, without cement content, by its conception, is to offer a possibility of making a material without cement content, which reintroduces a by-product/waste into the economic circuit - power plant ash that is still being dumped. The present request is fundamentally motivated by the need, identified both at global and national level, to implement the principles of sustainable development, with sustainable consumption of resources, of valorizing existing waste and preventing the generation of new ones, in the global ecological context of drastic reduction of harmful effects related to pollution, destabilization of ecosystems, global warming and all related elements. in this sense, this proposal approaches the in-depth research of the potential of the utilization of thermal power plant ash, as a raw material.

The difficulty of making geopolymer microconcrete lies in the fact that the physicochemical characteristics of power plant ash vary depending on the technological parameters of the power plant, the type of coal burned, the type of capture facility, the methods of post-capture processing of the ash, etc. Thus, thermal power plant ash can present variations in the oxide composition, granularity, specific surface, etc., all of which influence the evolution of the geopolymerization mechanism. Also, the binder - natural aggregates ratio and the granulometric distribution of the aggregates decisively influence the distribution of the aggregates in the geopolymeric matrix and the physical-mechanical characteristics, strength and durability of the cladding elements. The use of metallic fibers as dispersed reinforcement material in the geopolymer binder composite matrix brings, on the one hand, advantages in terms of physical-mechanical performance and durability, but on the other hand, it introduces a dosing problem, especially of the activator alkaline. The share of the alkaline activator in the entire mixture as well as its availability for the main purpose, that of contributing to the reactions of

geopolymerization, the workability and homogeneity of the mixture can be influenced, these two indicators being also influenced by the weight of metallic fibers and their potential for homogeneous dispersion during mixing.

The advantages of using the Manufacturing process and cladding elements from alkaline activated geopolymer microconcrete, without cement content, are the possibility of re-introducing into the economic circuit a polluting by-product/dumped waste - thermal power plant ash and the possibility of making small prefabricated elements (cladding elements ) that can be used after 7 days from casting, thus reducing the storage time for maturing, which in the case of similar precast concrete is 28 days from casting. Furthermore, precast cladding elements made from cement-free, alkali-activated geopolymer microconcrete, which mature faster than concrete, have at maturity mechanical strength characteristics comparable to concrete and a lower material density, which reduces including storage, transportation, handling and commissioning effort. These precast elements present a smooth, smooth, crack-free surface with good aesthetic characteristics, with low water absorption, resistance to abrasive agents or cleaning treatments, On the other hand, the production process and cladding elements of alkaline activated geopolymer microconcrete , without cement content contributes to the reduction of carbon emissions as a result of the fact that it does not use cement - it is known that the cement production industry is highly polluting.

Example of realization

Manufacturing process and cladding elements from alkaline-activated geopolymer microconcrete, without cement content, uses the following raw materials:

I. thermal power plant ash - pulverulent material, with fineness characterized as residue on the 0.045 mm sieve, maximum 40%. Class F thermal power plant ash is used, according to ASTM C618/2019 with the following conditions imposed for the oxide composition: (SiO ₂ + AI2O3 + Fe ₂ O ₃ ) >70%; SO ₃ <5%;PC<6%.

II. alkaline activator - solution prepared by mixing sodium silicate solution (Na ₂ SO ₃ ) and sodium hydroxide (NaOH) in known proportions.

III. natural river aggregates with a maximum grain size of 4 mm. IV. smooth metallic fibers.

The technological parameters imposed for the production process and cladding elements from alkaline activated geopolymer microconcrete, without cement content and the stages of the technological process are:

> Properties of alkaline activator raw materials

- sodium silicate solution (Na2SC>3) - marketed product and also known as glass water, with a ratio between molar percentage concentrations S1O2 / Na2O in the range of 1.5 and 3.5, is used as such;

- sodium hydroxide (NaOH) solution - is prepared by dissolving sodium hydroxide (NaOH) flakes in water, so as to obtain molar concentrations of 8M, 1 OM or 12M. The sodium hydroxide (NaOH) solution is used after 24 h of preparation and storage in closed containers.

> Preparation of alkaline activator - it is done by combining solutions of Na2SiO3 and NaOH. The mass ratio between the Na2SiO3 solution and the NaOH solution used for the preparation of the alkaline activator is in the range of 0.5 - 2.5.

> Age of the alkaline activator - the alkaline activator is used after 24 h of preparation and storage in closed containers.

> The mass ratio between the alkaline activator and power plant ash is in the range of 0.5 - 1.0.

> Mass percentage ratio between natural river aggregates and geopolymer binder is 50% - 50%, 60% - 40%, 65% - 35% or 70% - 30%.

> Preparation technology - the mixing of the components is carried out at a temperature of (20±3)°C, in the following stages:

- making the dry mixture by adding the predetermined amount of power plant ash to the aggregate mixture and homogenizing the dry matter (aggregate + ash) by mixing at low speed for another 60 seconds.

- the introduction of metallic fibers, in a mass ratio of 5-15 kg/m ³ of binder in the dry mixture and the homogenization of the mixture by kneading at low speed for another 60 seconds.

- adding the alkaline activator at a rate so that the entire amount of solution is introduced into the mixing tank during 90 seconds.

- low-speed mixing of the fresh geopolymer microconcrete mixture for 5 - 10 minutes, depending on the workability of the mixture.

> Pouring into molds - fresh geopolymer microconcrete is poured into polypropylene molds with the usual shapes and geometry for cladding elements. The size of the side of the print (length and / or width) will be a maximum of 500±5 mm. Regardless of the dimensions and shape of the selected patterns, the necessary conditions will be ensured to obtain a thickness of the finished product of min. 3 x maximum aggregate grain size.

> Vibration - after pouring in the patterns, they are vibrated for 5 minutes to homogenize and eliminate any air bubbles included in the geopolymer microconcrete mass during the preparation or casting process.

> Heat treatment procedure - the prepared geopolymer microconcrete hardens by keeping it at a temperature of 50°C -80°C, for 4-48 h.

> After completing the heat treatment stage, the products are left to cool to ambient temperature, they are removed from the mold and, if necessary, final finishing operations (deburring) are carried out. After hardening under heat treatment, the finished product is easily removed from the formwork because the geopolymeric microconcrete does not have great adhesion to the polypropylene from which the molds are made.

> To reach maturity by finalizing the polymerization reactions, the unformed elements are stored on pallets, in temperature conditions of 20±3°C and 60±5% relative air humidity, protected from the direct action of sunlight, rain, frost or other conditions environmental extremes, until reaching the age of 7 days from casting, after which they can be used for finishing works by cladding the walls of buildings. At this age, the products meet the requirements for easy commissioning and durability.

Figure 3 shows schematically the technological flow for the manufacturing process and cladding elements from alkaline-activated geopolymer microconcrete, without cement content.

Figure 3. Technological flow for Production process and cladding elements from alkaline activated geopolymer microconcrete, without cement content

The installation of the cladding elements made of alkaline activated geopolymer microconcrete, without cement content, is carried out without particular difficulties, by personnel qualified for such works, in a similar way to the installation of classic concrete cladding elements, using specific adhesives for cladding works, available on the building materials market.

The cladding elements resulting from the technological process shown in the diagram in figure 3 are prefabricated products which, at the age of 7 days after casting, present the following physical-mechanical and appearance characteristics;

> Appearance - dark gray-brown color, smooth appearance, and open porosity on the surface.

> Shape - variable, depending on mold shape.

> Dimensions - variable, depending on mold shape. The size of the side of the pattern (length and / or width) maximum 500±5 mm, the minimum thickness of 3 x the size of the largest grain of natural aggregates, depending on the profile of the pattern (mold).

> Apparent density - 1500 - 2000 kg/m ³ .

> Water absorption - maximum 8%.

> Bending strength - minimum 5 N/mm ² .

> Resistance to freeze-thaw, to the action of environmental factors and to treatments and cleaning solutions used on a regular basis.

These physical-mechanical characteristics can vary depending on the type and characteristics of the power plant ash, the molar concentration of the NaOH solution, the mass ratio between the NazSiO? solution and the NaOH solution used to prepare the alkaline activator, the mass ratio between the alkaline activator and the power plant ash, the temperature and the duration of the heat treatment, the values presented above being the minimum level of performance achieved.

Figure 4 shows, by way of example, without being considered significant from the point of view of shape and dimensions, the pavers made of alkaline activated geopolymer microconcrete, without cement content.

Fig. 4. Alkaline-activated geopolymer microconcrete cladding element, without cement content

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24. Willis N. J., IN201737001848 Geopolymers and geopolymer aggregates (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

25. Gong W., Lutz W., Pegg L, W02014141051 High-strength geopolymer composite cellular concrete (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

26. Gong W., Lutz W., Pegg L, WO2012083255 Geopolymer composite for ultra high performance concrete (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

27. Dubey A., IN9721/DELNP/2014 Dimensionally stable geopolymer compositions and method (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

28. Sheng S., CN106854045 Method for preparing concrete from geopolymer and recycled aggregate (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

29. Sivakumar S. K., US20180015515 A new method and an apparatus in converting unsorted municipal solid waste into geo-polymer pellets/briquettes and geo-polymer bricks/paver blocks (https://patentscoDe.wiDQ.int/search/en/search. isf accessed August 2019)

30. Partheeban P., IN201841049049 A geopolymer concrete with ggbs paver block (https://Datentscope.wipo.int/search/en/search.i sf accessed August 2019)

31. Chett B., US20100058957 Pervious concrete comprising a geopolymerized pozzolanic ash binder (https://patentscope.wipo.int/search/en/search.isf accessed August 2019)

32. Davidovits J. (1979), Synthesis of new high-temperature Geopolymers for reinforced plastics and composites, SPE PACTE'79, Costa Mesa, California, Society of Plastics Engineers, SUApp:151-154

33. Al Bakri Abdullah A.M.M., Hussin K., Bnuhussain M., Ismail K.N., Ahmad M.I. (2011b), Chemical Reactions in the Geopolymerisation Process Using Fly Ash-Based Geopolymer: A review, Australian Journal of Basic and Applied Sciences.

34. Davidovits J. (1988), Geopolymers of the first generation: SILIFACE-Process, Geopolymer ’88, First European Conference on Soft Mineralogy, Compiegne, France pp:49-67.

35. Duxon P., Provis J.L., Lukey G.C., van Demeter J.S.J. (2007), The role of inorganic polymer technology in the development of 'green concrete', Cement Concr. Res 37:1590-1597.

36. Lloyd N.A., Rangan B.V. (2010), Geopolymer concrete with fly ash, Second International Conference on Sustainable Materials and Technologies, Italy.

37. Herbert G., d'Espinose de Lacaillerie J.B, Roussel N. (2011), An environmental evaluation of geopolymer based concrete production: reviewing current research trends, J.Cleaner Prod. 19(11): 1229-1238.

38. CEPROCIM, (2009), C439 - The use of fly ash (type II admixture) in concrete, in order to improve the durability characteristics in accordance with the appropriate standards and/or regulations, harmonized with the European directive on construction products, Ministry of Regional Development and Tourism , Bucharest Romania

Claim 1

Manufacturing process and cladding elements from alkaline-activated geopolymer microconcrete, without cement content, using Class F thermal power plant ash as raw materials, according to ASTM C618/2019, with the fineness characterized as the residue on the 0.045 mm sieve, maximum 40% available in Romania, an alkaline activator based on sodium silicate (ȚS^SiCh) and sodium hydroxide (NaOH), natural river aggregates with a maximum grain size of 4 mm, and dispersed reinforcement with metal fibers intended for the production of cladding elements, for use in finishing works / protection of walls or other inclined or vertical elements of constructions.. The mass ratio between the NazSiCh solution and the NaOH solution used for the preparation of the alkaline activator is in the range of 0.5 - 2.5, and the mass ratio between the alkaline activator and power plant ash is in the range 0.5 1.0. The content of metal fibers for the reinforcement dispersed in the composite mass is 5-15 kg/m ³ binder.

Claim 2

Alkaline-activated geopolymer microconcrete, without cement content, dispersed reinforced, made as a result of the application of the Production Process and cladding elements from alkaline-activated geopolymer microconcrete, without cement content, using Class F thermal power plant ash as raw materials, according to ASTM C618/ 2019, with the fineness characterized as a residue on the sieve of 0.045 mm, maximum 40% available in Romania, an alkaline activator based on sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), natural river aggregates with a maximum grain size of 4 mm , and dispersed reinforcement with metal fibers intended for the production of cladding elements, for use in finishing works / protection of walls or other inclined or vertical elements of constructions. The physico-mechanical characteristics of the alkaline-activated geopolymer microconcrete, without cement content, at the age of 7 days after casting are: apparent density in hardened state 1500-2000 kg/m ³ , water absorption max. 8%, tensile strength by bending min. 5.0 N/mm ² and the compressive strength min. 25 N/mm ² .

Claim 3

Alkaline-activated micro-concrete geopolymer cladding element, without cement content, produced by Production process and cladding elements from alkaline-activated geopolymer micro-concrete, without cement content, for use in finishing work / protection of walls or other inclined elements or vertical, of constructions, with the following physico-mechanical characteristics (values recorded at the age of 7 days after casting): variable shape and dimensions depending on the characteristics of the pattern, with a maximum side size of 500±5 mm, a minimum thickness equal to 3 x the size of the larger grains of natural aggregates, apparent density in dry state 1500-2000 kg/m ³ , resistance to freeze-thaw, to the action of environmental factors and to currently used treatments and cleaning solutions.

MODIFIED DESCRIPTION

Process for making an alkaline activated geopolymer microconcrete without cement content and cladding elements made from it

The invention refers to a Process for making an alkaline activated geopolymer microconcrete, without cement content and cladding elements made from it, using as raw materials the power plant ash available in Romania, an alkaline activator based on sodium silicate (NaaSiCb) and sodium hydroxide (NaOH) and natural river sort aggregates with a maximum size of 4 mm, intended for the production of cladding elements of external or internal walls of constructions or other inclined or vertical elements thereof.

Following the Process of making an alkaline activated geopolymer microconcrete, without cement content and cladding elements made from it, finished elements are obtained, in the form of plates, dispersedly reinforced, intended for use in the creation of finishes in the form of surface cladding external or internal walls of buildings or other inclined or vertical elements thereof.

Alkaline-activated geopolymer microconcrete cladding elements without cement content are prefabricated elements, ready to be put into operation, whose structure consists of a geopolymer binder matrix in which natural river aggregates with a maximum grain of 4 mm are embedded and dispersed reinforcement with metallic fibers. depending on the molding pattern used, the cladding elements can be flat on the exposed (external) face or have different profiles / patterns.

The main feature of the Process for making an alkaline-activated geopolymer microconcrete, without cement content and cladding elements made from it, is the use of local raw materials, alkaline-activated power plant ash and natural aggregates of Romanian origin.

basically, the raw materials used for the production of geopolymeric microconcrete are power plant ash, alkaline activator, natural river aggregates and metal fibers for dispersed reinforcement. The alkaline activator is a solution made by quantitatively controlled mixing of sodium silicate solution NaaSiCh and a solution of sodium hydroxide NaOH.

As Davidovits showed as early as 1979, the matrix of the geopolymer binder is based on a Si-O-Al-O structure, by alternating tetrahedra of S1O4 and AIO4, joined together in three directions with all oxygen atoms, calling them geopolymeric materials ( Davidovits, 1979). in a simplified method, it can be stated that geopolymers can be synthesized by alkaline activation of materials that are rich in S1O2 and AI2O3 (Al Bakri Abdullah et al., 2011b).

RO 137964 A2 MODIFIED DESCRIPTION

The supply of oxides required for the production of the geopolymer binder of each individual material is shown in figure 1. The natural river aggregates form a skeleton covered in the geopolymer binder matrix.

The empirical formula for the entire geopolymerization process of the binder is (Davidovits, 1988):

Mn{-(SiO ₂ )z-AlO ₂ }n,wH ₂ O (1) where: M - represents the alkaline element, which can be: K (potassium); Na (sodium); Ca (calcium);

The symbol indicates the presence of a link;

n - represents the degree of polycondensation (or polymerization);

z - is 1, 2, 3 or greater, up to 32;

w - represents the number of bound water molecules.

Power plant ash * SiO ₂

Sodium silicate ·' A1 ₂ O ₃

Sodium hydroxide '> k: - - - — Na ₂ O

Water H ₂ O

Fig. 1. The origin of the molar elements that compose the alkaline activated geopolymer paste when the two components of the geopolymer material (the reactive solids and the alkaline solution) react, an alumino-silicate network is formed, resulting in a hard, water-resistant product (Duxon et al ., 2007). The geopolymerization reaction can also be expressed chemically according to the series of chemical equations (2).

2SiO ₂ -AI ₂ Oj + 3 OH ^- ·!- 3 H ₂ O-------► 2 [ΑΙ(ΟΗ) ₄ Γ+ [SiO^OH)./

-HO 0'

[Al (OHfSiCyOH)/- ----—> _HO -AI- O-SI-OH ----►

HO V ροϊνϊοπΰθπϊάίοπ I I . I ~-------------? ? ?

(2)

Geopolymerization reaction (Duxon et al., 2007) these materials are currently under development, research being encouraged mainly by the need to reduce CO ₂ emissions globally. Having excellent mechanical properties and resistances in aggressive environments, these materials represent an opportunity for both

RO 137964 Α2 _cpr

CHANGED DESCRIPTION environmental as well as engineering alternative to traditional technology (Lloyd and Rangan, 2010). However, it must also be taken into account that the production of activators based on sodium silicate or sodium hydroxide produces emissions that are not of the type of "greenhouse gases" (SOx, NOx, phosphates, etc.), but can become problematic if the development of rigorous methods of their production is not continued (Herbert et al., 2011).

Worldwide, research on alkaline-activated geopolymer materials exists, but their implementation differs greatly, due to factors that greatly influence this type of binding material. The parameters that influence the final characteristics of the geopolymer binder are:

- Physico-chemical characteristics of power plant ash

- The properties of the alkaline activator

- The ratio between NajSiCh Solution and NaOH Solution

- Ratio of alkaline activator to source material

- The ratio between solid raw materials and water

- Thermal treatment parameters

The large amount of thermal power plant ash resulting from the burning of coal for the production of electricity, in Romania, can create new opportunities for the creation of this type of innovative materials, with satisfactory durability and with a low negative impact on the environment. in Romania there are many thermal power plants whose ash, resulting as a by-product/waste, could be exploited for the production of geopolymer concrete based on power plant ash (Figure 2).

f Zalau Oradea __J · ♦ Arad X Timisoara Otira V · ♦ * \ #· The mind X. Piroirni <*Ruins > ·· Xu * V ·· Crave X/* ¹ ·· \ Sutures \ TRIBUTE X la»! • X BkiH | ·· i Bmov I * · Galiti .. Campulung »''' jj Dwwti (C Zv. ^r F··''·''i'iPL) 11 / ' ·· jXjitdaMtfy λ'Λ Giurgiu --<

• Thermoelectric plants

AMENDED DESCRIPTION patent number R000121965 mentions an invention related to an ecological cement composition with a content of 35-40% power plant ash. This material differs from the geopolymer binder that is the subject of this request in that it has a cement content of 6-8% and an aqueous ester solution of a modified resin, resulting from conifers of 0.180.22 1 and is intended for the realization of hydrotechnical road constructions .

in the patent number R000123502 an invention is mentioned regarding a composition for polymeric macroporous concrete intended for civil and industrial constructions. The composition of the polymeric macroporous concrete consists of polymer aggregates in the form of cubes with sides of 25 mm, 15 mm and 10 mm, and in the form of spheres with a diameter of 3 mm, mineral aggregate, with a grain size of 0, 05...0 , 1 mm, mineral binder, acrylic resin, bisphenolic epoxy resin, hardener and water, which clearly differentiates it from the geopolymer microconcrete that is the subject of this request.

in the invention patent with the number R000125903, an invention is mentioned regarding a composition and a process for obtaining a cement-polymer mixture as well as a process for applying the composition to paving roads and highways. This cement-polymer mixture is clearly different from the geopolymer microconcrete that is the subject of this request because it uses power plant ash as raw materials but also cement, carbon black and zinc oxide, and the field of use is totally different.

in the invention patent with the number R000106126, an invention related to a process for obtaining concrete products based on thermal power plant ash is mentioned. The content of calcium chemical activator and glass fiber waste, as well as the hardening carried out at 15 °C - 30 °C and humidity of 70 - 100% or by greenhouse effect differentiates this process from that of making alkaline activated geopolymer microconcrete, without cement content that is the subject of this request.

in patent number EP2852562, published also under numbers UAa201413803, CA2874234, CN104781209, US20150321960, AU2013264456, DK2852562, BR112014029174, ES2625015, ID2015/01680, MYPI 2014003224, IN2396/MUMNP/2014, PT2852562, WO2013/176545 an invention is mentioned referring to a geopolymer material, but which in its composition contains sugar, its derivatives, organic acids and salt.

In the patent number EP2951133, published also under the numbers KR1020150118969, US20150376060, RU2015133906, ID2017/00351, TH160513,

BR112015018590, IN2336/KOLNP/2015, RU0002664723, WO2014/118242, mentions an invention relating to a fire-resistant geopolymer material, but made with magnesium-based compounds.

AMENDED DESCRIPTION in the invention patent number US09290416 an invention is mentioned regarding a process for making a geopolymer material based on thermal power plant ash, but the principle of making it is based on the method of theoretical calculation of the composition. A similar process is presented in patent number W02005049522, also published under numbers ZA2006/04360, EP1689691, US20070125272, CN1882516, CA2545407, NZ547756,

AU2004290614, INI31 l/KOLNP/2006, EP1689691, whose main difference from the presented proposal is the content of 40-60% aggregates, and the alkaline activator may contain a silicate of alkaline earth metals, not necessarily sodium silicate.

in the invention patent with the number CN106630903, an invention related to geopolymer concrete is mentioned, in the composition of which there is power plant ash and slag, but intended for the execution of foundations with high durability.

in the invention patent with the number WO2011135584, also published under the number IN1365/MUM/2010, an invention is mentioned regarding an alkaline activated geopolymer material, but in the composition of which calcium hydroxide and Portland cement are also found.

in the invention patent with the number IN1830/CHE/2015, an invention is mentioned regarding a geopolymer material but based on alkaline activated hearth ash (fatty ash), with hardening at normal temperature, without heat treatment.

in the invention patent with the number CN104529300, an invention related to a geopolymer material containing glass powder, slag, kaolin, zinc oxide, titanium dioxide, etc. is mentioned.

in the invention patent with the number IN6203/DELNP/2011, also published under the numbers EP2385966, US20110271876, CN102325736, W02010/079414, an invention is mentioned regarding a geopolymer material, but which in its composition contains blast furnace slag and bauxite.

in the invention patent with the number NZ707001, published also under the numbers US20150321954, AU2013344816, WO2014/075134, an invention related to a geopolymer material, but which also contains sodium carbonate in its composition, is mentioned.

in the invention patent with the number CN103172295, an invention related to a geopolymer material is mentioned, but which in the composition of the activator contains triethanolamine, a naphthalene water reducer, quartz powder and milk of lime.

in the invention patent with the number IN7105/CHE/2015, an invention related to a geopolymer material is mentioned, but which in its composition contains sand with a controlled granulometric curve, without dispersed reinforcement.

in the invention patent with the number CN109437701, an invention related to a geopolymer material is mentioned, but which in its composition also contains clay and cristobaJite powder.

AMENDED DESCRIPTION in the patent number CN106336158 an invention is mentioned regarding 5 » » a geopolymer material, but which also contains mineral waste powder, ultrafine silica, water reducing agent and aggregates.

in the invention patent with the number CN106082927, an invention related to a geopolymer material is mentioned, but which in its composition also contains slag, micro-powder from construction waste and sodium hydroxide powder.

patent number JP2016005994 mentions an invention related to a geopolymer material, but which in its composition also contains blast furnace slag and ultrafine silica.

in the invention patent with the number RU0002599742, an invention related to a geopolymer material is mentioned, but which in the composition also contains potassium hydroxide and ultrafine silica, and the alkaline activator also contains potassium silicate.

patent number WO2016030904 mentions an invention related to a geopolymer material, but which in its composition does not contain sodium hydroxide, instead it contains blast furnace slag.

in the invention patent with the number RU0002517729, an invention is mentioned regarding » J J a geopolymer material, but which in the composition contains a gelation enhancing additive based on clay minerals (montmorillonite), and the heat treatment temperature is in the range of 25°C -75°C.

in the invention patent with the number IN201841008645, an invention related to a geopolymer material is mentioned, but which in its composition contains furnace slag, nanosilica, sea water and marble dust.

in the invention patent with the number CN101891498, an invention related to a geopolymer material is mentioned, but which in its composition contains aluminum dust.

in the invention patent number IN201737001848, published also under the numbers AU2015303826, US20170204008, CN107074651, W02016/023073, an invention is mentioned regarding a geopolymer material, but which in its composition contains either power plant ash or an aluminum phyllo-silicate as a substitute of it.

in the invention patent with the number W02014141051, published and under the number EP2970003, an invention is mentioned regarding a cellular geopolymer material, with an apparent density of 400 kg/m ³ - 1200 kg/m ³ and a compressive strength 28 days after casting of 3 - 17 MPa and which in the composition contains Portland cement, furnace slag, meta-kaolin, furnace dust, pozzolanic aluminosilicates rich in calcium oxide and gelling agent.

in patent number WO2012083255, published also under numbers CA2821512, EP2651846, JP2013545714, MX342948, RU2013132983, KR1020140010018, RU0002599742, BR112013014685, VN35844 TH 147136, CN107265937, IN5571/CHENP/2013, EG27^4

RO 137964 Α2

AMENDED DESCRIPTION mentions an invention related to a geopolymer material, but which in the composition contains pozzolanic additive, nanosilica, and the heat treatment temperature is 90-150 °C.

in the invention patent number IN9721/DELNP/2014, published also under the numbers UAa201412514, CA2871577, CN104245621, EP2841390, JP2015514675, KR1020150006855, RU2014146785, NZ702224, AU2013252 686, RU0002622263, BR112014025056, MYPI 2014703079, W02013/163010, an invention relating to to a geopolymer material, but which also contains calcium sulfate in its composition.

in the invention patent with the number CN106854045, published also under the numbers CN106854072, CN 106854059, an invention is mentioned regarding a method of making a geopolymeric material which, however, uses slag and recycled aggregates.

in patent number US20180015515, published also under numbers SG11201607307Q, MYPI 2017702815, CA2976409, CN107249765, KR1020170116086, PH1/2017/501408, ID2018/01002, WO2016/1 28994, mention is made of an invention relating to a method of making the elements of paving using municipal waste. The main difference with the present request is the realization of a geopolymer using not the thermal power plant ash, but the ash resulting from the burning of municipal solid waste.

in the invention patent with the number IN201841049049, an invention is mentioned regarding a method of making paving elements from geopolymeric material, but they refer to the test and admissibility conditions according to IS 15658:2006, more permissive in terms of limits of acceptability and which provides for testing 28 days after pouring, and blast furnace slag is used in the composition of the geopolymer.

in the invention patent with the number US20100058957 an invention is mentioned regarding a method of making a geopolymeric material, which can be used in the manufacture of paving elements, but in its composition using recycled aggregates and the alkaline activator and may contain hydroxides, carbonates , aluminates, silicates of alkaline earth metals or combinations thereof.

Although in the documents presented above there are elements in common with the Process for making an alkaline activated geopolymer microconcrete without cement content and cladding elements made from it - in general the presence of power plant ash and the use of its alkaline activation method, neither one of them does not refer to a product or process for obtaining a geopolymer microconcrete using exclusively thermal power plant ash available in Romania, and each of the previously presented has at least one particularity that differentiates them. As previously presented, the general characteristics, oxide composition and fineness of the power plant ash, as well as the technological stages of preparation of the alkaline activator are essential for the realization of the geopolymer binder, respectively the finished product - cladding element from

MODIFIED DESCRIPTION geopolymer microconcrete, and clearly differentiates the process of making the alkali-activated geopolymer microconcrete, without cement content, which is the subject of this request, in relation to the documents presented and analyzed above.

The purpose of this invention is to offer, using local materials from Romania, a complete and environmentally friendly solution for the production of cladding elements from alternative construction materials, with a low impact on the environment by applying the circular economy concept for power plant ash that from - an industrial by-product becomes a raw material in the design and production of alkaline activated geopolymer materials, thus preventing its conversion into landfilled waste.

The innovativeness of this invention consists in the valorization of local materials through the development of new compositions of alkaline activated materials based only on thermal power plant ash and the specific design of compositions suitable for the realization of prefabricated elements for cladding with physical-mechanical characteristics satisfying the intended field of use.

The problem solved by this Process for making an alkali-activated geopolymer microconcrete, without cement content and cladding elements made from it, by its conception, is to offer a possibility to make a material without cement content, which reintroduces into the circuit economically a by-product/waste - power plant ash which is still landfilled. The present request is fundamentally motivated by the need, identified both at global and national level, to implement the principles of sustainable development, with sustainable consumption of resources, of valorizing existing waste and preventing the generation of new ones, in the global ecological context of drastic reduction of harmful effects related to pollution, destabilization of ecosystems, global warming and all related elements. in this sense, this proposal approaches the in-depth research of the potential of the utilization of thermal power plant ash, as a raw material.

The difficulty of making geopolymer microconcrete lies in the fact that the physicochemical characteristics of power plant ash vary depending on the technological parameters of the power plant, the type of coal burned, the type of capture facility, the methods of post-capture processing of the ash, etc. Thus, thermal power plant ash can present variations in the oxide composition, granularity, specific surface, etc., all of which influence the evolution of the geopolymerization mechanism. Also, the binder - natural aggregates ratio and the granulometric distribution of the aggregates decisively influence the distribution of the aggregates in the geopolymeric matrix and the physical-mechanical characteristics, strength and durability of the cladding elements. The use of metallic fibers as dispersed reinforcement material in the geopolymer binder composite matrix brings, on the one hand, advantages in terms of physical-mechanical performance and durability, but on the other hand, it introduces a dosing problem, especially of the activator alkaline. The weight of the alkaline activator in the whole

MODIFIED DESCRIPTION mixture as well as its availability for the main purpose, that of contributing to geopolymerization reactions, can influence the workability and homogeneity of the mixture, these two indicators being also influenced by the weight of metallic fibers and their potential for homogeneous dispersion during mixing.

The advantages of using the Process for making an alkaline activated geopolymer microconcrete, without cement content and cladding elements made from it, are the possibility of re-introducing into the economic circuit a polluting by-product/dumped waste - thermal power plant ash and the possibility of making small prefabricated elements (cladding elements) that can be used after 7 days from casting, thus reducing the storage time for maturing, which in the case of similar concrete prefabs is 28 days from casting. Furthermore, precast cladding elements made from cement-free, alkali-activated geopolymer microconcrete, which mature faster than concrete, have at maturity mechanical strength characteristics comparable to concrete and a lower material density, which reduces including storage, transportation, handling and commissioning effort. These precast elements present a smooth, smooth surface without cracks, with good aesthetic characteristics, with low water absorption, resistance to abrasive agents or cleaning treatments, On the other hand, the Process for making an alkaline-activated geopolymer microconcrete, without content of cement and cladding elements made from it contribute to the reduction of carbon emissions as a result of the fact that it does not use cement - it is known that the cement production industry is highly polluting.

Example of realization

The process of making an alkaline activated geopolymer microconcrete without cement content and cladding elements made from it uses the following raw materials:

I. thermal power plant ash - pulverulent material, with fineness characterized as residue on the 0.045 mm sieve, maximum 40%. Class F power plant ash is used, according to ASTM C618/2019 with the following conditions imposed for the oxide composition: (SiO ₂ + A1 ₂ O ₃ + Fe ₂ O ₃ ) >70%; SO ₃ <5%;PC<6%.

II. alkaline activator - solution prepared by mixing sodium silicate solution (Na ₂ SO ₃ ) and sodium hydroxide (NaOH) in known proportions.

III. natural river aggregates with a maximum grain size of 4 mm. IV. smooth metallic fibers.

The technological parameters imposed for the Process of making an alkaline activated geopolymer microconcrete, without cement content and cladding elements made from it and the stages of the technological process are: I

CHANGED DESCRIPTION > Alkaline Activator Raw Material Properties

- sodium silicate solution (Na ₂ SO3) - marketed product and also known as glass water, with a ratio between percentage molar concentrations of SiO ₂ / Na ₂ O in the range of 1.5 and 3.5, is used as such;

- sodium hydroxide (NaOH) solution - is prepared by dissolving sodium hydroxide (NaOH) flakes in water, so as to obtain molar concentrations of 8M, 1 OM or 12M. The sodium hydroxide solution (NaOH) is used after 24 h of preparation and storage in closed containers.

> Preparation of the alkaline activator - it is done by combining solutions of Na ₂ SiO3 and NaOH. The mass ratio between the Na ₂ SiO3 solution and the NaOH solution used for the preparation of the alkaline activator is in the range of 0.5 - 2.5.

> Age of the alkaline activator - the alkaline activator is used after 24 h of preparation and storage in closed containers.

> The mass ratio between the alkaline activator and power plant ash is in the range of 0.5 - 1.0.

> Mass percentage ratio between natural river aggregates and geopolymer binder is 50% - 50%, 60% - 40%, 65% - 35% or 70% - 30%.

> Preparation technology - the mixing of the components is carried out at a temperature of (20±3)°C, in the following stages:

- making the dry mixture by adding the predetermined amount of power plant ash to the aggregate mixture and homogenizing the dry matter (aggregate + ash) by mixing at low speed for another 60 seconds.

- the introduction of metallic fibers, in a mass ratio of 5-15 kg/m ³ of binder in the dry mixture and the homogenization of the mixture by kneading at low speed for another 60 seconds.

- adding the alkaline activator at a rate so that the entire amount of solution is introduced into the mixing tank during 90 seconds.

- low-speed mixing of the fresh geopolymer microconcrete mixture for 5 - 10 minutes, depending on the workability of the mixture.

> Pouring into molds - fresh geopolymer microconcrete is poured into polypropylene molds with the usual shapes and geometry for cladding elements. The size of the side of the print (length and / or width) will be a maximum of 500±5 mm. Regardless of the dimensions and shape of the selected patterns, the necessary conditions will be ensured to obtain a thickness of the finished product of min. 3 x maximum aggregate grain size.

RO 137964 Α2 93

MODIFIED DESCRIPTION > Vibration - after pouring into the molds, they are vibrated for 5 minutes to homogenize and eliminate any air bubbles included in the geopolymer microconcrete mass during the preparation or casting process.

> Heat treatment procedure - the prepared geopolymer microconcrete hardens by keeping it at a temperature of 50°C -80°C, for 4-48 h.

> After completing the heat treatment stage, the products are left to cool to ambient temperature, they are removed from the mold and, if necessary, final finishing operations (deburring) are carried out. After hardening under heat treatment, the finished product is easily removed from the formwork because the geopolymeric microconcrete does not have great adhesion to the polypropylene from which the molds are made.

> To reach maturity by finalizing the polymerization reactions, the unformed elements are stored on pallets, in temperature conditions of 20±3°C and 60±5% relative air humidity, protected from the direct action of sunlight, rain, frost or other conditions environmental extremes, until reaching the age of 7 days from casting, after which they can be used for finishing works by cladding the walls of buildings. At this age, the products meet the requirements for easy commissioning and durability.

Figure 3 shows schematically the technological flow for the Process of making an alkaline-activated geopolymer microconcrete without cement content and cladding elements made from it.

Ash Natural river aggregates Metal fibers Silicate solution Thermal power plant sodium hydroxide sort 0/4 mm sodium (Na2SC>3) (NaOH)

RO 137964 Α2

MODIFIED DESCRIPTION

The installation of cladding elements made of alkaline activated geopolymer microconcrete, without cement content, is carried out without particular difficulties, by personnel qualified for such works, in a similar way to the installation of classic cladding elements made of concrete, using specific adhesives for cladding works, available on the building materials market.

The cladding elements resulting from the technological process shown in the diagram in figure 3 are prefabricated products which, at the age of 7 days after casting, present the following physical-mechanical and appearance characteristics:

> Appearance - dark gray-brown color, smooth appearance, no open porosity on the surface.

> Shape - variable, depending on mold shape.

> Dimensions - variable, depending on mold shape. The size of the side of the pattern (length and / or width) maximum 500±5 nun, the minimum thickness of 3 x the size of the largest grain of natural aggregates, depending on the profile of the pattern (mold).

> Apparent density - 1500 - 2000 kg/ra ³ .

> Water absorption - maximum 8%.

> Bending strength - minimum 5 N/mm ² .

> Resistance to freeze-thaw, to the action of environmental factors and to treatments and cleaning solutions used on a regular basis.

These physico-mechanical characteristics may vary depending on the type and characteristics of the power plant ash, the molar concentration of the NaOH solution, the mass ratio between the Na?SiO3 solution and the NaOH solution used to prepare the alkaline activator, the mass ratio between the alkaline activator and the power plant ash, temperature and duration of heat treatment, the values presented above being the minimum level of performance achieved.

Figure 4 shows, by way of example, without being considered significant from the point of view of shape and dimensions, the pavers made of alkaline activated geopolymer microconcrete, without cement content.

Fig. 4. Alkaline-activated geopolymer microconcrete cladding element, without cement content

CHANGED DESCRIPTION

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Claims (1)

Claim 1 PROCEDURE FOR MAKING AN ALKALINE ACTIVATED GEOPOLYMER MICROCONCRETE WITHOUT CEMENT CONTENT, characterized in that it has the following stages: 1). Class F thermal power plant ash with a fineness of 0.045 mm sieve residue, maximum 40%, available in Romania, an alkaline activator based on sodium silicate (NazSiCh) and sodium hydroxide (NaOH), natural aggregates are used as raw materials of river with the maximum grain of 4 mm, and dispersed reinforcement with metal fibers, so that the content of metal fibers in the composite mass is 5-15 kg/m ³ binder. 2). Class F thermal power plant ash and natural river aggregates with a maximum grain size of 4 mm are dosed gravimetrically. 3). The dry mixture of Class F thermal power plant ash and natural river aggregates with a maximum grain size of 4 mm is made. 4). The metallic fibers are dosed gravimetrically. 5). The dry mixture containing Class F thermal power plant ash, natural river aggregates with a maximum grain size of 4 mm and metal fibers is made. 6). Prepare the alkaline activator composed of NazSiCh solution and NaOH solution (of different molar concentrations) so that the mass ratio between them is between 0.5 and 2.5. 7). The dry mixture and the alkaline activator are dosed gravimetrically, so that the mass ratio between the alkaline activator and the power plant ash is in the range of 0.5 - 1.0. 8). The geopolymer microconcrete is prepared by mixing the dry mixture with the alkaline activator for 5-10 minutes. 9). The resulting composite is poured into specific molds and vibrated for 3-5 minutes. 10). The heat treatment is carried out by maintaining the patterns with composite at a temperature of 50°C -80°C, for 4-48 h. 11). Stripping, deburring, storage. Claim 2 ALKALINE ACTIVATED GEOPOLIMER MICROCONCRETE, WITHOUT CEMENT CONTENT, characterized by the fact that it consists of Class F thermal power plant ash with a fineness as residue on the 0.045 mm sieve, maximum 40% available in Romania, an alkaline activator based on sodium silicate ( NazSiOs) and sodium hydroxide (NaOH), natural river aggregates with a maximum grain size of 4 mm and dispersed reinforcement with metal fibers. Claim 3 CLADDING ELEMENTS MADE OF MICROCONCRETE GEOPOLIMER, characterized by the fact that they have variable shape and dimensions depending on the dimensions of the pattern, with the following physical-mechanical characteristics (values recorded at the age of 7 days after casting): variable shape and dimensions depending on the characteristics of the pattern, with maximum side size of 500±5 mm, minimum thickness equal to 3 x the size of the largest grain of natural aggregates, apparent density in dry state 1500-2000 kg/m ³ , water absorption max. 8%, resistance to freeze-thaw, to the action of environmental factors and to treatments and cleaning solutions used on a regular basis.