A dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated gelling material and preparation method thereof

Abstract

The present invention discloses a dechlorination and detoxification fly ash-waste glass powder-slag composite alkali-activated gelling material and a preparation method thereof. The alkali-activated gelling material is mainly composed of hydrated calcium aluminosilicate gel and hydrated sodium aluminosilicate gel, and the raw material composition includes: dechlorination and detoxification fly ash, waste glass powder, slag and alkali activator, wherein the alkali activator is prepared from sodium silicate solution and sodium hydroxide solid; the present invention realizes efficient resource utilization and improvement of the performance of alkali-activated gelling materials by scientifically proportioning raw materials. The precursor selected by the present invention is rich in active mineral components such as calcium, silicon, and aluminum, and the alkali activator prepared by adding sodium silicate solution and sodium hydroxide solid provides an ideal alkaline environment for the system, and the chemical components between the components complement and synergize, so that the system can simultaneously generate C-A-S-H gel and N-A-S-H gel. Thereby achieving material properties of high compressive strength, moderate setting time, and reaction heat balance, while having good working performance and long-term durability.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization and building materials, and in particular to a dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated gelling material and a preparation method thereof. Background Art

[0002] Alkali-activated cementitious materials are a new type of low-carbon and environmentally friendly building material, mainly made of minerals or industrial wastes rich in aluminosilicates. Under the action of alkali activators, the raw materials first dissolve to form silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedron monomers, and then combine with alkali metal ions such as calcium and sodium in the system through polycondensation reactions to form a three-dimensional network structure of aluminosilicate gel (also known as geopolymer). Compared with traditional silicate cement, alkali-activated cementitious materials not only have simple preparation processes, low energy consumption, and low pollution, but also have excellent mechanical and corrosion resistance properties and the ability to solidify heavy metals. They have become sustainable alternative materials for addressing environmental problems in the construction industry. In addition, its preparation process can efficiently utilize industrial solid waste and is completed at room temperature, thereby reducing greenhouse gas emissions, and has broad prospects for resource utilization.

[0003] Alkali-activated gelling materials can be divided into two categories: one is a high-calcium system with hydrated calcium aluminosilicate gel (CASH gel) as the main gel product, and the other is a calcium-free system with hydrated sodium aluminosilicate gel (NASH gel) as the gel product. CASH gel contributes greatly to the compressive strength of the system, so by adding calcium-rich alumina precursors, such as dechlorinated fly ash and slag, the system can be prompted to generate more CASH gel; but the high-calcium system has a fast reaction rate, short setting time, and high reaction heat, which easily leads to material cracking, which is not conducive to actual production. Using alumina precursors with very low calcium content, such as waste glass powder, as raw materials, the calcium-free system can produce more NASH gel, thereby alleviating the problems caused by high reaction heat; but the calcium-free system usually has a long setting time, is prone to weathering, cracking, and has low compressive strength. Therefore, it is necessary to select suitable raw materials, take advantage of the strengths and avoid the weaknesses through scientific formulas, and comprehensively utilize the advantages of the two systems to prepare alkali-activated gelling materials with moderate setting time and reaction heat and excellent mechanical properties.

[0004] Waste incineration fly ash contains about 40% CaO and has significant alkalinity, making it one of the important raw materials for alkali-activated cementitious materials. However, about 20% of its soluble chloride salts will have an adverse effect on the compressive strength and durability of the material, and will enrich heavy metals and dioxin-type persistent organic pollutants. Therefore, it is necessary to remove the chlorine from the fly ash through water washing and degrade dioxins by low-temperature thermal decomposition, while retaining a high content of CaO and strong alkalinity, so as to ensure that the fly ash used can not only provide the calcium phase components required for alkali-activated cementitious materials, but also significantly improve the mechanical properties and durability of the materials. However, due to the lack of silicon and aluminum phase components in the treated dechlorinated and detoxified fly ash, it is difficult to meet the requirements for preparing alkali-activated cementitious materials when used alone, so it needs to be used in combination with other industrial solid wastes to optimize the components and performance. Waste glass contains 60%-70% amorphous SiO2 and is an important silicon source for alkali-activated cementitious materials. However, waste glass has a stable structure and low reaction activity, and it is difficult to quickly participate in the reaction process of cementitious materials. Therefore, the volcanic ash activity of waste glass powder can be effectively improved by reducing the particle size of waste glass powder by mechanical grinding and other methods to achieve mechanical activation, and combining sodium-based activators to accelerate the dissolution rate of SiO2. In addition, the micro-aggregate effect of waste glass powder also helps to improve the density and mechanical properties of cementitious materials, so that it can fully play its role in generating gel. Slag, as a conventional raw material for alkali-activated cementitious materials, is a highly active calcium-silicon-aluminum-based mineral with a high proportion of glassy structure. It reacts rapidly in an alkaline environment and can efficiently generate CASH gel, thereby significantly improving the early strength of alkali-activated cementitious materials. However, the slag reaction heat release rate of high-calcium system is high and the setting time is short, which may cause cracking problems. In practical applications, by rationally coordinating with dechlorinated and detoxified fly ash and waste glass powder, the reaction rate of slag can be effectively optimized, the setting time and reaction heat can be balanced, and the mechanical properties and durability of the material can be improved. The introduction of slag can not only provide active calcium-silicon components, but also significantly enhance the overall performance of the material. It is an indispensable component in the alkali-activated system.

[0005] The prior art has the following technical problems:

[0006] 1) The production of traditional silicate cement needs to be carried out under high temperature and high pressure conditions. The process is complicated, energy consumption is high, and there is a lot of carbon emissions, which does not meet the current development requirements of low-carbon and environmental protection.

[0007] 2) The output of fly ash and waste glass powder from urban waste incineration is huge, but the ways to utilize them are limited, making it difficult to achieve large-scale disposal, causing environmental pollution and waste of resources;

[0008] 3) Direct use of fly ash from garbage incineration to prepare alkali-activated cementitious materials has the problem of too high chloride content, which can easily cause steel corrosion in actual production applications. At the same time, fly ash contains dioxins and potential heavy metals, and direct preparation of building materials products may have the risk of heavy metal leaching, which limits its application and promotion;

[0009] 4) The alkali-activated cementitious materials of the high-calcium system have a too fast reaction rate, short setting time and high reaction heat, which can easily lead to material cracking and is not conducive to actual production applications; while the materials of the calcium-free system have a slow reaction rate, too long setting time, are easily weathered and cracked, and have low compressive strength, making it difficult to meet engineering performance requirements. Summary of the invention

[0010] The present invention aims to propose a composite alkali-activated cementitious material based on dechlorinated and detoxified fly ash-waste glass powder-slag and a preparation method thereof. The method uses dechlorinated and detoxified fly ash, waste glass powder and slag as main raw materials, and prepares high-performance alkali-activated cementitious materials through the chemical composition complementarity mechanism between the three industrial solid wastes, combined with scientific formula design and optimized process flow. Compared with the prior art, the all-solid waste-based alkali-activated cementitious material prepared by the present invention has the remarkable characteristics of adjustable setting time, excellent crack resistance, strong weathering resistance and high compressive strength, and exhibits good comprehensive mechanical properties and durability.

[0011] To achieve the above object, the present invention adopts the following technical solution:

[0012] The invention discloses a dechlorination and detoxification fly ash-waste glass powder-slag composite alkali-activated gelling material, wherein the alkali-activated gelling material has hydrated calcium aluminosilicate gel and hydrated sodium aluminosilicate gel as main components, and the reaction product and raw materials thereof include: dechlorination and detoxification fly ash, waste glass powder, slag and alkali activator, wherein the alkali activator is prepared from sodium silicate solution and sodium hydroxide solid;

[0013] The mass ratio of dechlorinated and detoxified fly ash, waste glass powder and slag is (5-9): (9-5): 6;

[0014] The mass of Na2O in the alkaline activator is 4%-8% of the total mass of dechlorinated and detoxified fly ash, waste glass powder and slag;

[0015] The modulus of sodium silicate in the alkaline activator is 0.6-1.4, and the modulus represents the molar ratio of SiO2 to Na2O;

[0016] The mass ratio of the total mass of dechlorinated and detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkali activator is 1:(0.35-0.65).

[0017] As a further improvement, the dechlorinated and detoxified fly ash of the present invention is obtained directly from a factory after the waste incineration fly ash undergoes three-stage water washing treatment and low-temperature heat treatment.

[0018] As a further improvement, the particle size requirements of the dechlorinated and detoxified fly ash, waste glass powder and slag powder in step S1 of the present invention are: the pass rate through a 100-mesh sieve reaches 100%, and the pass rate through a 200-mesh sieve is not less than 85%.

[0019] As a further improvement, the alkali-activated cementitious material of the present invention has a compressive strength of 18.5-33.5 MPa, an initial setting time of 52-255 min, a final setting time of 131-410 min, and a fluidity of 120-225 mm.

[0020] The present invention also discloses a method for preparing a dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated gelling material, comprising the following steps:

[0021] S1: mixing dechlorinated detoxification fly ash, waste glass powder and slag in a mass ratio of (5-9): (9-5): 6 to obtain a matrix material;

[0022] S2: Weighing a liquid sodium silicate solution and a solid sodium hydroxide solution in a ratio of 0.6-1.4 so that the modulus of sodium silicate is 0.6-1.4, and mixing them to prepare an alkali activator;

[0023] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1: (0.35-0.65), and the mass of Na2O in the alkaline activator is 4%-8% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag. After mixing evenly, let it stand for 1-12 hours to obtain the alkaline activator;

[0024] S4: Mix the matrix material in S1 and the alkali activator in S3 and stir them evenly to obtain a slurry, then pour it into a standard mold for vibration molding, and flatten the surface to form a sample;

[0025] S5: The sample is sealed and cured in a standard curing box, then demoulded and cured to the target age to obtain a finished alkali-activated cementitious material.

[0026] As a further improvement, the stirring process in S4 described in the present invention is to stir for 1-4 min at a stirring blade speed of 300-500 r / min.

[0027] As a further improvement, the standard curing conditions in the standard curing box in S5 described in the present invention have a specific temperature standard of 20±2° C. and a relative humidity standard of more than 95%.

[0028] As a further improvement, the target age in S5 described in the present invention is 3 days and 28 days.

[0029] Compared with the prior art, the invention has the following beneficial effects.

[0030] The present invention provides a new approach to the resource utilization of solid waste. By using dechlorinated and detoxified fly ash, waste glass powder, slag and alkali activator as raw materials, based on alkali activation technology and standard maintenance and other means, it is possible to prepare all-solid waste-based alkali-activated cementitious materials and building materials that meet actual production requirements, and also to achieve large-scale disposal and resource utilization of industrial solid waste.

[0031] The present invention scientifically proportions the raw materials, wherein the ratio of dechlorinated detoxified fly ash: waste glass powder: slag is (5-9): (9-5): 6, the modulus range of the alkali activator is 0.6-1.4, the alkali equivalent is 4-8%, and the water-cement ratio is 0.35-0.65. This ratio gives full play to the complementarity of the chemical components of the three solid waste materials, realizes efficient resource utilization and improves the performance of alkali-activated cementitious materials. The precursor selected by the present invention is rich in active mineral components such as calcium, silicon, and aluminum. The alkali activator prepared by adding sodium silicate solution and sodium hydroxide solid provides an ideal alkaline environment for the system. The chemical components of each component complement and synergistically act, so that the system can simultaneously generate CASH gel and NASH gel. Thereby achieving material properties with high compressive strength, moderate setting time, and reaction heat balance, while having good working performance and long-term durability. While optimizing the early strength of the alkali-activated cementitious material, it also significantly improves the later durability and balances the comprehensive mechanical properties.

[0032] The present invention optimizes the ratio of the three components of dechlorinated detoxified fly ash, waste glass powder and slag through experiments, ensuring the operability and stability of the prepared alkali-activated cementitious material in actual industrial production. By scientifically designing the formula and regulating the setting time and fluidity, the material exhibits good working performance during the production process and meets the actual engineering requirements of strength, setting time and fluidity. At the age of 28 days, the compressive strength of the material reaches 32.8 MPa, showing excellent mechanical properties, and can replace ordinary C30 and other building materials products.

[0033] The present invention directly uses the dechlorinated and detoxified fly ash after low-temperature thermal decomposition and three-stage water washing treatment in the factory as the raw material of the alkali-activated cementitious material. Compared with the untreated original fly ash, the chlorine content of the fly ash is significantly reduced, and the soluble chloride salt content is greatly reduced, thereby effectively mitigating the risk of steel corrosion that may be caused by the material during use. In addition, the dechlorinated and detoxified fly ash no longer contains dioxins, and the heavy metal content is significantly reduced. This feature not only improves the durability and long-term stability of the material, but also reduces the environmental risks caused by heavy metal leaching, further expanding the scope of application of the material in engineering applications.

[0034] The present invention adopts a room temperature alkali activation process, which does not require high temperature firing. Compared with the production process of traditional silicate cement, it significantly reduces energy consumption and carbon emissions. At the same time, the present invention effectively disposes of three types of solid wastes, namely, dechlorination and detoxification fly ash, waste glass powder and slag, and realizes the high-value resource utilization of solid wastes, especially the disposal of fly ash, which breaks through the limitations of traditional landfill or incineration processes and further explores its recycling value.

[0035] To sum up, the present invention has both environmental and socio-economic benefits. It not only provides a new and feasible way for the resource utilization of solid waste, but also provides technical support for the green and low-carbon transformation of the construction industry. It has important application prospects and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention discloses a flow chart of a dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material and a preparation method thereof. DETAILED DESCRIPTION

[0037] The present invention provides a dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material and a preparation method thereof. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] The embodiment of the present invention provides a method for preparing an alkali-activated gelling material using dechlorinated and detoxified fly ash, waste glass powder and slag as main raw materials.

[0039] In some specific embodiments, in order to ensure that the dechlorinated detoxified fly ash, waste glass powder and slag particles are in full contact as much as possible, the particle size is small and the specific surface area is large, which can not only increase the reaction area, but also make the raw materials and the alkali activator more fully contact, thereby improving the utilization rate of the raw materials. The present invention selects dechlorinated detoxified fly ash, waste glass powder and slag powder with a pass rate of 100% through a 100 mesh sieve and a pass rate of not less than 85% through a 200 mesh sieve for embodiments. The finer the raw material with the particle size meeting the requirements, the better the effect.

[0040] In some specific embodiments, the mass fraction of sodium oxide in the original liquid sodium silicate solution used is 10%, the mass fraction of silicon dioxide is 30%, and the mass fraction of water is 60%.

[0041] In some specific embodiments, the weighed sodium hydroxide solid and the sodium silicate solution need to be left standing for 1-12 hours after mixing, and the purpose of standing is to ensure that the sodium hydroxide is completely dissolved and fully reacts with the sodium silicate, so as to obtain a uniform sodium silicate solution. For two different groups of single variable experimental groups, different standing times do not affect the single experimental variable principle, because the standing time only affects the uniformity and completeness of the solution, and does not involve changes in the core experimental variables, so it will not interfere with the main variable control of the experiment.

[0042] In some specific embodiments, the mixed alkali activator and matrix material need to be stirred for 1-4 min at a stirring blade speed of 300-500 rpm. The main purpose of stirring is to ensure that the alkali activator and the matrix material are fully and evenly mixed, thereby providing consistent initial conditions for the experiment. In single variable experiments of different groups, the difference in the speed of the stirring blade and the difference in stirring time do not affect the single variable principle, because stirring is only an auxiliary step in the mixing process, and its purpose is to eliminate the interference that may be caused by uneven mixing, rather than to have a substantial impact on the experimental results.

[0043] In some specific embodiments, in order to expel bubbles in the slurry, the slurry needs to be vibrated on a vibration table after being poured into a standard mold. Example 1

[0044] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0045] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 so that the modulus of sodium silicate is 0.8 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 72.94%, and the mass fraction of the solid sodium hydroxide is 27.06%.

[0046] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 53.54% and 46.46% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0047] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0048] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 2

[0049] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 7:7:6 to obtain a matrix material.

[0050] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 so that the modulus of sodium silicate is 0.8 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 72.94%, and the mass fraction of the solid sodium hydroxide is 27.06%.

[0051] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 53.54% and 46.46% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0052] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0053] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 3

[0054] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 9:5:6 to obtain a matrix material.

[0055] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 so that the modulus of sodium silicate is 0.8 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 72.94%, and the mass fraction of the solid sodium hydroxide is 27.06%.

[0056] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 53.54% and 46.46% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0057] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0058] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 4

[0059] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0060] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.6 so that the modulus of sodium silicate is 0.6 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 65.04%, and the mass fraction of the solid sodium hydroxide is 34.97%.

[0061] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, and the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag. The specific mass fractions of water and the alkaline activator in the preparation of S2 are 60.00% and 40.00% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0062] S4: Mix the matrix material in S1 with the alkali activator prepared in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0063] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 5

[0064] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0065] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 1.4 to prepare an alkali activator; the mass fraction of the liquid sodium silicate solution is 86.45% and the mass fraction of the solid sodium hydroxide is 13.55%.

[0066] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 35.82% and 64.18% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0067] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0068] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 6

[0069] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0070] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 of the modulus of sodium silicate to prepare an alkali activator; the mass fraction of the liquid sodium silicate solution is 72.94% and the mass fraction of the solid sodium hydroxide is 27.06%.

[0071] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 4% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 78.99% and 21.01% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0072] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0073] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 7

[0074] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0075] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 of the modulus of sodium silicate to prepare an alkali activator; the mass fraction of the liquid sodium silicate solution is 72.94% and the mass fraction of the solid sodium hydroxide is 27.06%.

[0076] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.45, the mass of Na2O in the alkaline activator is 12% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator in S2 are 46.04% and 53.96% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0077] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0078] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 8

[0079] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0080] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 so that the modulus of sodium silicate is 0.8 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 72.94%, and the mass fraction of the solid sodium hydroxide is 27.06%.

[0081] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.53, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 58.92% and 41.08% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0082] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0083] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Example 9

[0084] S1: The dechlorination and detoxification fly ash, waste glass powder and slag are uniformly mixed in a mass ratio of 5:9:6 to obtain a matrix material.

[0085] S2: Liquid sodium silicate solution and solid sodium hydroxide are weighed and mixed in a ratio of 0.8 so that the modulus of sodium silicate is 0.8 to prepare an alkali activator; wherein the mass fraction of the liquid sodium silicate solution is 72.94%, and the mass fraction of the solid sodium hydroxide is 27.06%.

[0086] S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1:0.35, the mass of Na2O in the alkaline activator is 8% of the total mass of dechlorinated detoxified fly ash, waste glass powder and slag, and the mass fractions of the specifically weighed water and the alkaline activator prepared in S2 are 44.4% and 55.6% respectively. After mixing evenly, let it stand for 8 hours to obtain the alkaline activator.

[0087] S4: Mix the matrix material in S1 with the alkali activator in S3, stir for 2 minutes at a stirring blade speed of 400 r / min to obtain a pure slurry, then pour it into a standard mold of 20 mm×20 mm×20 mm for vibration molding, and scrape the surface to form a sample.

[0088] S5: The sample is sealed and cured in a standard curing box with a temperature standard of 20±2 ℃ and a relative humidity standard of more than 95%, then demoulded and continued to be cured to obtain a finished alkali-activated cementitious material. Comparative Example 1

[0089] This comparative example is compared with Example 1, except that it does not contain dechlorinated detoxification fly ash, and the rest is the same as Example 1. Comparative Example 2

[0090] This comparative example is compared with Example 1, except that it does not contain waste glass powder, and the rest is the same as Example 1.

[0091] According to the requirements of the above embodiments and comparative examples, the raw material dosages of the embodiments and comparative examples are summarized in Table 1. The compressive strength of alkali-activated cementitious materials was measured according to GB / T 50107-2010 "Standard for Testing and Evaluation of Concrete Strength", and the initial setting time and final setting time were measured according to the method in GB / T 1346-2011 "Standard for Testing Methods of Cement Standard Consistency Water Consumption, Setting Time and Stability", and the test results are shown in Table 2. The heavy metal leaching concentration of the finished product after the target age curing was completed was tested according to GB5085.3-2007 "Standard for Identification of Hazardous Waste Leaching Toxicity Identification", and the test results are shown in Table 3.

[0092] Table 1: Raw material dosage of examples and comparative examples

[0093]

[0094] Table 2: Properties of alkali-activated gelling materials prepared in Examples and Comparative Examples

[0095]

[0096] Table 3: Heavy metal leaching test results of various embodiments and comparative examples (unit: mg / L)

[0097]

[0098] It can be seen from Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 that the compressive strength of the alkali-activated cementitious material prepared by the ternary solid waste system of dechlorinated detoxified fly ash-waste glass powder-slag is higher than that of the binary system composed of waste glass powder-slag or dechlorinated detoxified fly ash-slag. This is because the calcium minerals and silicon-aluminum minerals in the ternary system are sufficient to generate sufficient CASH gel to improve the compressive strength. In addition, with the increase in the amount of waste glass powder, the compressive strength of the alkali-activated cementitious material at the age of 28 days gradually increased from 20.8 MPa to 32.8 MPa, and the initial setting time and final setting time were gradually delayed; the fluidity also increased from 120 mm in Example 3 to 210 mm in Example 1. The compressive strength of Comparative Examples 1 and 2 is low, and the initial setting time of Comparative Example 2 is only 20 min, and the final setting time of Comparative Example 2 reaches 550 min, which is not conducive to actual production and processing.

[0099] It can be seen from Example 1, Example 4 and Example 5 that the use of an alkali activator prepared from sodium hydroxide and sodium silicate solution with a modulus of 0.6-1.4 can effectively activate the precursor components, so that the compressive strength of the alkali-activated cementitious material is within the range of 22.7-32.8 MPa. As the modulus increases, the setting time of the alkali-activated cementitious material is gradually prolonged, and the fluidity gradually increases, but they all fluctuate within a reasonable range and can meet actual production needs. Properly increasing the modulus of the alkali activator can improve the compressive strength, but when the modulus is too high, the compressive strength will decrease instead. This is because a high modulus means that the amount of sodium hydroxide used is relatively small, resulting in a decrease in the OH⁻ ion concentration in the solution, making it difficult to fully activate the decomposition of the glass in the slag and the volcanic ash activity of the waste glass powder and the dechlorinated and detoxified fly ash; at the same time, the Ca dissolved from the surface of the raw material particles 2+ , Si 4+ , Al 3+ The gel product generated is less, resulting in reduced compressive strength. On the other hand, the alkali activator with a low modulus is usually in a semi-solidified state, with poor fluidity, and is prone to rapid setting when mixed with the matrix material, causing difficulty in operation. In combination with actual operation, material performance and economic factors, the present invention selects an alkali activator with a modulus of 0.6-1.4 as a reasonable range.

[0100] It can be found from Example 1, Example 6 and Example 7 that when the alkali equivalent increases from 4% to 8%, the compressive strength of the alkali-activated cementitious material increases from 18.5 MPa to 32.8 MPa, the initial setting time is shortened from 240 min to 165 min, the final setting time is shortened from 410 min to 310 min, and the fluidity of the slurry is slightly increased. This is because with the increase of the alkali equivalent, the alkalinity of the solution increases, which promotes the dissociation of the vitreous body in the dechlorinated and detoxified fly ash, waste glass powder and slag, generates more CASH gel, improves the compressive strength, reduces the internal friction between the raw material particles, and improves the fluidity of the slurry; at the same time, the hydration reaction rate is accelerated, resulting in a shortened setting time. When the alkali equivalent increases from 8% to 12%, the compressive strength decreases from 32.8 MPa to 28.6 MPa, the initial setting time is extended from 165 min to 184 min, the final setting time is extended from 310 min to 360 min, and the fluidity is slightly reduced. This is because too high an alkali equivalent will cause the generated gel precipitation to cover the surface of the unreacted raw material particles, hindering further reaction and inhibiting the continuous generation of CASH gel, thereby reducing the compressive strength, delaying the setting time and affecting the fluidity of the slurry. In summary, the alkali equivalent of the alkali-activated gelling material prepared from dechlorinated and detoxified fly ash, waste glass powder and slag in the present invention should not be too low or too high. Considering the actual operation, material working performance and economic factors, the present invention suggests that it is reasonable to control the alkali equivalent within the range of 4%-8%.

[0101] It can be seen from Example 1, Example 8, and Example 9 that as the water-cement ratio gradually increases, the setting time gradually increases, and the strength gradually decreases. In actual operation, when the water-cement ratio is lower than 0.35, the initial setting time cannot meet the actual production requirements; when the water-cement ratio is higher than 0.65, the final setting time does not meet the requirements, and the strength is significantly reduced. The present invention only shows embodiments with water-cement ratios of 0.35, 0.45, and 0.53, and can be implemented in the range of 0.35-0.65 water-cement ratios.

[0102] In summary, by reasonably controlling the dosage of dechlorinated detoxified fly ash, waste glass powder, slag and alkali activator, and selecting appropriate ratios and implementation methods according to actual needs, alkali-activated cementitious materials with excellent performance can be prepared. The method of the present invention is simple in process and easy to operate. The prepared materials have outstanding mechanical properties and working performance, and the environmental risks are extremely low. With the gradual maturity of technology and application conditions, the present invention has the potential to be widely promoted and applied.

[0103] The above is only a preferred embodiment of the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material, characterized in that: The alkali-activated gelling material has hydrated calcium aluminosilicate gel and hydrated sodium aluminosilicate gel as main components, and the reaction product, the raw materials include: dechlorinated detoxification fly ash, waste glass powder, slag and alkali activator, wherein the alkali activator is prepared from sodium silicate solution and sodium hydroxide solid; The mass ratio of the dechlorinated and detoxified fly ash, waste glass powder and slag is (5-9): (9-5): 6; The mass of Na2O in the alkaline activator is 4%-8% of the total mass of the dechlorinated detoxified fly ash, waste glass powder and slag; The modulus of sodium silicate in the alkaline activator is 0.6-1.4, and the modulus represents the molar ratio of SiO2 to Na2O; The mass ratio of the total mass of the dechlorinated and detoxified fly ash, waste glass powder and slag to the mass ratio of the water in the alkali activator is 1: (0.35-0.65); The dechlorinated and detoxified fly ash is obtained by subjecting waste incineration fly ash to three-stage water washing treatment and low-temperature heat treatment; The particle size requirements of the dechlorinated and detoxified fly ash, waste glass powder and slag powder in step S1 are: the passing rate through a 100-mesh sieve reaches 100%, and the passing rate through a 200-mesh sieve is not less than 85%; The alkali-activated gelling material has a compressive strength of 18.5-33.5 MPa, an initial setting time of 52-255 min, a final setting time of 131-410 min, and a fluidity of 120-225 mm; The dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated gelling material comprises the following steps: S1: mixing dechlorinated detoxification fly ash, waste glass powder and slag in a mass ratio of (5-9): (9-5): 6 to obtain a matrix material; S2: Weighing a liquid sodium silicate solution and a solid sodium hydroxide solution in a ratio of 0.6-1.4 so that the modulus of sodium silicate is 0.6-1.4, and mixing them to prepare an alkali activator; S3: Weigh water and mix it with the alkaline activator in S2, so that the mass ratio of the total mass of the dechlorinated detoxified fly ash, waste glass powder and slag to the mass ratio of water in the alkaline activator is 1: (0.35-0.65), and the mass of Na2O in the alkaline activator is 4%-8% of the total mass of the dechlorinated detoxified fly ash, waste glass powder and slag. After mixing evenly, let it stand for 1-12 hours to obtain the alkaline activator; S4: Mix the matrix material in S1 and the alkali activator in S3 and stir them evenly to obtain a slurry, then pour it into a standard mold for vibration molding, and flatten the surface to form a sample; S5: The sample is sealed and cured in a standard curing box, then demoulded and cured to the target age to obtain a finished alkali-activated cementitious material.

2. The dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material according to claim 1, characterized in that: The stirring process in S4 is to stir for 1-4 minutes at a stirring blade speed of 300-500 r / min.

3. The dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material according to claim 1, characterized in that: The standard curing conditions in the standard curing box in S5 are as follows: the specific temperature standard is 20±2° C., and the relative humidity standard is above 95%.

4. The dechlorinated and detoxified fly ash-waste glass powder-slag composite alkali-activated cementitious material according to claim 1, characterized in that: The target ages in S5 are 3 days and 28 days.

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