Industrial waste residue-arsenic sandstone geopolymer gelling material and preparation method thereof

Abstract

The present invention belongs to the field of geopolymers, and discloses an industrial waste residue-arsenic sandstone geopolymer cementitious material and a preparation method thereof. The material uses arsenic sandstone and industrial solid waste as main raw materials, and is mixed in a specific ratio to form a new type of geopolymer cementitious material, aiming to improve resource utilization, reduce environmental impact and reduce construction costs. Through systematic research and experiments, the optimal critical dosage of arsenic sandstone was determined to be 22.5%, at which the mechanical properties of the material remain basically unchanged. The comparative analysis of arsenic sandstone and standard sand verified its feasibility as aggregate, which is crucial to the economic benefits and environmental friendliness of the material. Industrial waste residue and arsenic sandstone can be obtained locally, reducing costs and transportation expenses. The present invention also provides preparation steps such as precise raw material proportioning, mixing, curing and mechanical property testing to ensure excellent material quality, low environmental load and low economic cost.

Description

Technical Field

[0001] The invention belongs to the field of geopolymers and discloses an industrial waste residue-arsenic sandstone geopolymer gelling material and a preparation method thereof. Background Art

[0002] Arsenic sandstone is an interbedded rock mass composed of thick layers of sandstone, mudstone, mudstone, and shale. Its characteristics include weak cementation, severe weathering, and susceptibility to damage. Although relatively hard in a dry state, its internal structure is loose and its cementation is insufficient, resulting in its dispersion in water and erosion in wind. Previous research has focused on methods to manage arsenic sandstone, while the exploration of incorporating arsenic sandstone into cementitious material systems and utilizing it is still in its infancy.

[0003] Geopolymer is an inorganic gelling material, which is mainly composed of a three-dimensional network structure formed by the polymerization reaction of [SiO4] tetrahedron and [AlO4] tetrahedron.

[0004] Current research on geopolymer cementitious materials focuses primarily on exploring the impact of various raw materials on their performance. For example, fly ash and slag have been shown to be ideal raw materials for the preparation of high-performance geopolymers, realizing the resourceful utilization of waste. Current research on arsenic sandstone materials primarily focuses on its physicochemical properties and arsenic sandstone modification technologies. The latter primarily examines the mechanical properties of arsenic sandstone after high-temperature curing after composites of arsenic sandstone and other materials have been shown to significantly improve the mechanical strength of modified arsenic sandstone components through high-temperature compaction.

[0005] Reference 1 (Wu Tiejun, Shao Zhiyuan, Fan Weiwu, et al. Effect of calcium hydroxide content on fly ash-based and metakaolin-based polymer foam materials [J]. Cement, 2022, (07): 1-5. DOI:10.13739 / j.cnki.cn11-1899 / tq.2022.07.001) describes the geopolymer reaction process, which is divided into three basic steps: (1) alkali dissolves and leaches the active silica and alumina phase in the raw materials; (2) dissolved precursor ions migrate and condense into oligomeric monomers; (3) monomer condensation and polymerization to amorphous to semi-crystalline silicate polymers.

[0006] Reference 2 (Fang Mingwei, Wang Dan, Zhou Fengtao, et al. Effect of alkali activator on the performance of fly ash geopolymer concrete [J]. Functional Materials, 2023, 54 (11): 11170-11176.) explains that alkali-activated solid aluminosilicate cementitious materials are one of the forward-looking research areas of advanced inorganic non-metallic materials. Alkali-activated aluminosilicate cementitious materials are prepared by reacting industrial solid waste (fly ash, slag, steel slag, coal gangue and various tailings, etc.) with alkaline activator solution. It has the advantages of simple process, no need for firing, low cost, low energy consumption, low CO2 emissions, maintaining ecological balance, environmental friendliness and the ability to achieve large-scale recycling of solid waste resources.

[0007] Since arsenic sandstone contains potential volcanic ash active substances, through alkali excitation, its internal silicon-aluminum compounds can be converted into a tightly cross-linked silicon-oxygen-aluminum network structure, which can greatly improve the material performance.

[0008] Reference 3 (Zhang Meixiang, Luo Zhongtao, Yin Huiling, et al. Study on the preparation of concrete using arsenic sandstone as a substitute for fine aggregate and its anti-erosion performance [J]. Concrete, 2016, (06): 158-160.) describes the replacement rate of arsenic sandstone for river sand in cement mortar experiments. When the replacement rate is 20%, the mechanical properties requirements can be met. However, when the replacement rate reaches 50%, the strength reduction is serious.

[0009] Reference 4 (Dong Jingliang, Zhang Tingting, Wang Lijiu, et al. Study on the properties of Inner Mongolia arsenic sandstone and its influence on the mechanical properties of cement [J]. Journal of Soil and Water Conservation in China, 2015, (07): 46-49+73. DOI:10.14123 / j.cnki.swcc.2015.0192.) shows that arsenic sandstone can replace cement. When the replacement rate is below 20%, the material performance meets the standard. When the replacement rate reaches 30%, the various properties of the material deteriorate significantly.

[0010] Reference 5 (Dong Jingliang, Zhang Tingting, Wang Lijiu, et al. Study on the properties of Inner Mongolia arsenic sandstone and its influence on the mechanical properties of cement [J]. Soil and Water Conservation in China, 2015, (07): 46-49+73. DOI:10.14123 / j.cnki.swcc.2015.0192.) shows that when the concentration of sodium hydroxide is low, it helps to increase the distribution range of the product in the voids.

[0011] Reference 6 (Du Tianling, Liu Ying, Yu Yongyan, et al. Effect of water glass on the strength of fly ash slag geopolymer and its excitation mechanism [J]. Journal of Highway and Transportation Research and Development, 2021, 38 (01): 41-49.) shows that when the water glass content is 20% and the modulus is between 1.2 and 1.6, the compressive strength of the material reaches the optimal value.

[0012] In summary, it is verified that arsenic sandstone can replace part of river sand and cement under alkali-activated conditions, ensuring that at the appropriate dosage, the performance of geopolymer cementitious materials is not only unaffected, but may even be improved to a certain extent.

[0013] The chemical composition of arsenic sandstone is similar to that of standard sand. Both are rich in silica and have similar particle diameter distribution, which provides feasibility for local arsenic sandstone resources to replace standard sand.

[0014] The shortcomings of the above technology are:

[0015] (1) Most studies have mixed arsenic sandstone with other materials alone. When arsenic sandstone is mixed with other minerals, they fail to provide accurate data on the replacement rate of arsenic sandstone and the amount of other materials added.

[0016] For example, when arsenic sandstone is mixed with other mineral materials, such as fly ash and slag, the dosage of each material needs further study.

[0017] (2) Whether different types of alkali activators can still meet the ideal requirements for materials with different dosages.

[0018] For example, although activators can improve the activity and stability of cementitious materials to a certain extent, attention must be paid to the type and dosage of the activators.

[0019] The threat posed by arsenic sandstone to the environment and ecology primarily manifests as soil and water pollution, leading to bioaccumulation and food chain transmission, harming plant and animal health, and disrupting ecological balance. Furthermore, its weathering products can cause land degradation and desertification, exacerbating regional erosion vulnerability. Therefore, it is essential to explore a building material that can meet the needs of transportation projects in seasonally frozen regions where arsenic sandstone is located, integrating arsenic sandstone resources locally with secondary industrial waste, and exploring the dosage of each material. Summary of the Invention

[0020] To address the shortcomings of existing technologies, the present invention discloses an industrial waste residue-arsenic sandstone geopolymer cementitious material and its preparation method. Using arsenic sandstone and industrial waste residue as raw materials, the present invention formulates a building material that meets the requirements of transportation projects in seasonally frozen regions where arsenic sandstone is located, providing a new solution to the problems faced by projects in seasonally frozen regions. The material significantly reduces the consumption of materials such as cement and sand, reduces transportation costs, and significantly improves economic efficiency.

[0021] The present invention includes the following technical solutions:

[0022] An industrial waste residue-arsenic sandstone geopolymer cementitious material comprises the following components in percentage by mass: 0-22.5% of arsenic sandstone, 0-31.75% of fly ash, 0-31.75% of slag, 20.6% of water glass, 0.5-1.5% of calcium hydroxide, 15% of water, and 0.4% of a retarder.

[0023] Reaction mechanism:

[0024] (1) A small amount of active substances in the arsenic sandstone material undergo depolymerization and polymerization reactions under the action of an alkaline environment. The Si-O bonds and Al-O bonds in the material break down into silicon oxide monomers and aluminum oxide monomers in this environment. These monomers can gradually polymerize into gelling substances.

[0025] (2) With the addition of fly ash and slag, more suitable silicon and aluminum substances in the alkali-activated system participate in the reaction, and the OH in the mixed material - With Ca 2+ The reaction generates calcium silicate hydrate gel (CSH) and calcium aluminate hydrate (CAH). The formed calcium aluminate hydrate comes into contact with air and can react with CO2 to generate calcium carbonate.

[0026] (3) Water glass acts as both an activator and a reactant. The Na2O in the water glass breaks the Si-O and Al-O bonds in the fly ash and slag, causing elements such as Si and Al to dissolve. The siliceous components in the water glass act as a reactant and react with the Ca2O dissolved in the slag. 2+ React to generate hydrated calcium silicate gel, Al dissolved in fly ash and slag 3+ and Si 4+ It penetrates deep into the vicinity of the water glass core and reacts with the SiO2 in the core under dehydration conditions. The polymerization products of adjacent cores overlap each other to form a whole, which is the fundamental reason for the establishment of the strong network structure of the geopolymer.

[0027] Microstructure:

[0028] Geopolymer is an inorganic gelling material, which is mainly composed of a three-dimensional network structure formed by the polymerization reaction of [SiO4] tetrahedron and [AlO4] tetrahedron.

[0029] Preferably, the above-mentioned industrial waste slag-arsenic sandstone geopolymer cementitious material includes the following components in percentage by mass: arsenic sandstone 22.5%, fly ash 20%, slag 20%, water glass 20.6%, calcium hydroxide 1.5%, water 15%, and retarder 0.4%.

[0030] Furthermore, the above-mentioned industrial waste slag-arsenic sandstone geopolymer cementitious material, the arsenic sandstone comes from the Shanxi, Shaanxi and Inner Mongolia regions, and the main oxides are silicon dioxide, aluminum oxide, iron oxide and calcium oxide; the mass fractions thereof are: silicon dioxide 50% to 65%, aluminum oxide 10% to 20%, iron oxide 5% to 10%, calcium oxide 5% to 10%, and the content of other oxides is less than 10%;

[0031] The proportions of different particle sizes of arsenic sandstone are: <0.1mm accounts for 3% to 8%, 0.1~0.25mm accounts for 35% to 50%, 0.25~0.5mm accounts for 25% to 40%, 0.5~1mm accounts for 10% to 20%, and ≥1mm accounts for 2% to 6%.

[0032] Furthermore, in the above-mentioned industrial waste residue-arsenic sandstone geopolymer cementitious material, the fly ash is Class I F fly ash, and the purity of the calcium hydroxide is 90% to 98%.

[0033] Furthermore, in the above-mentioned industrial waste slag-arsenic sandstone geopolymer cementitious material, the slag is slag powder with an activity index of S105.

[0034] Furthermore, in the above-mentioned industrial waste residue-arsenic sandstone geopolymer cementitious material, the water glass is sodium silicate water glass, and the modulus is 1.0 to 1.4.

[0035] The present invention also discloses a method for preparing the above-mentioned industrial waste residue-arsenic sandstone geopolymer gelling material, comprising the following steps:

[0036] (1) Accurately weigh the arsenic sandstone, fly ash, slag, calcium hydroxide, and retarder, mix these dry materials in a blender and set aside;

[0037] (2) Accurately weigh water and water glass, add them into the blender, stir at low speed and then change to high speed to make the mixture uniform;

[0038] (3) Pour the stirred slurry into the test mold, seal and cure it, and after demoulding, cure it under standard curing conditions for the specified time, and then conduct a mechanical property test.

[0039] Furthermore, in the preparation method of the above-mentioned industrial waste slag-arsenic sandstone geopolymer gelling material, the rotation speed of the mixer during low-speed stirring is 135±10r / min, and the revolution speed is 60±10r / min; the rotation speed during high-speed stirring is 280±15r / min, and the revolution speed is 120±15r / min.

[0040] Furthermore, in the preparation method of the above-mentioned industrial waste residue-arsenic sandstone geopolymer cementitious material, the size of the test mold is 50mm×50mm×50mm, the test piece is demolded between 20h and 24h after molding, and cured under standard curing conditions for 28d±8h.

[0041] Furthermore, in the preparation method of the above-mentioned industrial waste residue-arsenic sandstone geopolymer cementitious material, the mechanical property test is an unconfined compressive strength test, which is carried out using a microcomputer-controlled electro-hydraulic servo universal testing machine with a maximum test force of 300Kn.

[0042] Preferably, it is prepared according to the following parameters:

[0043] (1) Accurately weigh fly ash, slag, arsenic sandstone, solid activator, and retarder. After ensuring that the mixer is dry, stir these dry materials in the mixer for 30 seconds to mix evenly and set aside.

[0044] (2) Accurately weigh water and water glass, add them to the blender, stir at low speed for 30 seconds, then switch to high speed stirring for 180 seconds to ensure uniform mixture.

[0045] (3) Molding and curing: Pour the stirred slurry into a 50mm x 50mm x 50mm test mold in batches. Before demolding the specimen, cover the mold with a glass plate, keeping the distance between the cover and the mold at 2mm to 3mm. Demold the specimen 20h to 24h after molding. Curing is carried out under standard curing conditions for 28d (28d ± 8h).

[0046] (4) The 28-day unconfined compressive strength test of the specimens was carried out in accordance with the "Highway Geotechnical Test Code" (JTG3430-2020). The compressive strength test of the cementitious material was carried out using a WAW-300B microcomputer-controlled electro-hydraulic servo universal testing machine.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] As a building material, the advantages of arsenic sandstone in reducing economic costs are mainly reflected in the following aspects:

[0049] 1) Local materials: Arsenic sandstone can be directly obtained locally, eliminating the need to transport traditional building materials such as cement and sand, greatly saving transportation costs and material purchase costs.

[0050] 2) Reduce material consumption: By mixing arsenic sandstone with industrial waste residues such as fly ash, the consumption of traditional materials such as cement and sand can be reduced. This not only improves the economic efficiency of the materials, but also effectively utilizes industrial waste residues and reduces the environmental impact of waste.

[0051] 3) Improve soil water properties: The combined use of arsenic sandstone and fly ash can improve the water properties of the soil and increase the soil's water retention and water supply capacity, which is of great significance for soil improvement and vegetation restoration in arid and semi-arid areas, thereby reducing the economic cost of building materials in these areas.

[0052] 4) Increasing the amount of slag and fly ash in geopolymer cementitious materials improves the material's compressive strength. However, excessively high levels of argillaceous sandstone inhibit this strength improvement. This is because, while argillaceous sandstone has potential reactivity and can produce a certain amount of cementitious material upon alkali activation, the proportion of active components (SiO₂ and Al₂O₃) within it that can participate in the reaction is limited. Furthermore, as the fly ash and slag content increases, the amount of these active components that dissolve gradually increases, playing a key role in enhancing the strength of the geopolymer, resulting in a rapid increase in its compressive strength. When the content is further reduced to below 22.5%, the material's strength growth stabilizes, becoming virtually unaffected by the argillaceous sandstone content. Below 22.5%, there is no significant reduction in the material's compressive strength; the critical argillaceous sandstone content in this invention is 22.5%. DETAILED DESCRIPTION

[0053] The particle size of arsenic sandstone was tested through indoor testing in accordance with the "Standard for Geotechnical Test Methods" (GB50123-2019). The sieve analysis process followed the sieve analysis test steps in 8.2.2 of the "Standard for Geotechnical Test Methods" (GB50123-2019).

[0054] Among them, the test sieves required by the instrument and equipment are: sieves with specifications of 0.10 mm, 0.25 mm, 0.50 mm, 1.00 mm, and 2 mm, with sieve bottom and sieve cover, and should comply with the regulations on square hole test sieves in the specifications "Technical Requirements and Inspection of Test Sieve" GB / T 6003.1 and GB / T6003.2.

[0055] Specific process:

[0056] From the air-dried, loose sandstone sample, a representative sample is taken using the quartering method according to the following provisions:

[0057] 1) For particles with a diameter less than 2 mm, take 100g~300g;

[0058] 2) For particles with a maximum particle size less than 10 mm, take 300g~1000g;

[0059] 3) For particles with a maximum diameter less than 20 mm, take 1000g~2000g;

[0060] 4) For particles with a maximum particle size less than 40 mm, take 2000g~4000g;

[0061] 5) Take more than 4000g of particles with a maximum diameter of less than 60mm.

[0062] 2 The sieve analysis method should be carried out in the following steps:

[0063] 1) Take out the sample and weigh it to the nearest 0.1g; when the sample mass is greater than 500g, weigh it to the nearest 1g;

[0064] 2) Pass the sample through a 2mm fine sieve and weigh the mass of the sandstone above and below the sieve respectively;

[0065] 3) If the amount of arsenic sandstone below the 2 mm sieve is less than 10% of the total mass of the sample, the fine sieve analysis can be omitted; if the amount of arsenic sandstone above the 2 mm sieve is less than 10% of the total mass of the sample, the coarse sieve analysis can be omitted;

[0066] 4) Take the sample on the 2mm sieve and pour it into the sensitive upper sieve of the coarse sieve stacked in sequence;

[0067] Take the sample under the 2mm sieve and pour it into the top sieve of the selected fine sieve for sieving. The fine sieve should be placed on a vibrating sieve machine and shaken for 10 minutes to 15 minutes.

[0068] 5) Starting with the sieve with the largest aperture, remove each sieve in sequence. Gently tap and shake the sieve on a piece of white paper. If soil particles still leak through, continue tapping and shaking the sieve until no more arsenic sandstone leaks through. All remaining arsenic sandstone should be placed on the next sieve. Weigh the sample remaining on each sieve individually. If the sample mass is less than 500g, weigh it to the nearest 0.1g.

[0069] 6) The difference between the total mass of the sample before screening and the sum of the mass of the samples on the sieves and at the bottom of the sieve at all levels after screening shall not be greater than 1% of the total mass of the sample.

[0070] The sieve analysis results show that the different particle sizes of the arsenic sandstone used in this experiment account for: <0.1mm (5.34%), 0.1~0.25mm (43.37%), 0.25~0.5mm (32.15%), 0.5~1mm (14.91%), and ≥1mm (4.23%).

[0071] In accordance with the standard "Fly Ash for Use in Cement and Concrete" (GB T 1596-2017), the test used Class I F fly ash, which has high reactivity. The physical and chemical performance requirements are as described in 6.1 of "Fly Ash for Use in Cement and Concrete" (GB T 1596-2017).

[0072] With reference to the specifications "Granulated blast furnace slag for use in cement" (GB / T 203-2008) and "Granulated blast furnace slag powder for use in cement, mortar and concrete" (GBT18046-2017), the test used S105 grade slag powder with the highest activity index.

[0073] Refer to the specification "Industrial Calcium Hydroxide" (HG / T 4120-2009). The calcium hydroxide for the test was purchased from Tianjin Xinbot Chemical Co., Ltd., with a purity of 95%, in the form of white powder, and belongs to the first-class product.

[0074] The test water glass is sodium silicate water glass purchased from Henan Luboshi New Material Technology Co., Ltd., with a modulus of 1.2.

[0075] Refer to the specification "Cement Paste Mixer" (JC-T729-2005). The main instrument for this experiment is characterized in that: the cement paste mixer mainly consists of a mixing pot, mixing blades, a transmission mechanism and a control system. The mixing blades perform a revolution and a rotation in opposite directions in the mixing pot and can be adjusted vertically. The mixing pot can be lifted and lowered. The transmission structure ensures that the mixing blades rotate in the specified direction and speed. The control system has two functions of automatic control and manual control according to the program. The rotation speed of the mixing blades at high speed and low speed should meet the requirements of the specification. The rotation speed of self-rotation is 140±5r / min (low speed) and 285±10r / min (high speed), with the direction being clockwise. The rotation speed of revolution is 62±5r / min (low speed) and 125±10r / min (high speed), with the direction being counterclockwise. The rotation speed of self-rotation is set at 140±5r / min (low speed) and 285±10r / min (high speed), with the direction being clockwise. The rotation speed of revolution is 62±5r / min (low speed) and 125±10r / min (high speed), with the direction being counterclockwise.

[0076] Refer to the specification "Technical Conditions of Electric Shaking Table" (GB / T 13310-1991). The normal working ambient temperature of the shaking table is 5-35°C, and the relative humidity is not more than 90% (at 25°C). The frequency range of the shaking table is 5 Hz < f < 50 Hz, not more than ±1Hz, f > 50 Hz, not more than ±2%f. The vibration frequency of the shaking table is stabilized at 50Hz, and the amplitude is 0.5mm~2mm.

[0077] Refer to the specification "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021). Make, maintain and test the performance of the specimens according to this specification.

[0078] To prevent the discreteness of experimental data, three parallel specimens are required for each group of specimen working conditions tests. If the difference between any test value and the median value is greater than 15%, then this value is excluded, and the median value is used as the final test result.

[0079] During the test process, the instrument is required to ensure that only axial pressure is applied to the specimen, and no external force is applied laterally. Load until the specimen is crushed, and the recorded maximum pressure value is the unconfined compressive strength of the specimen.

[0080] The technical solutions in this embodiment are described clearly and completely below. The described embodiments are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0081] Example

[0082] The arsenic sandstone is distributed in the Shanxi, Shaanxi, and Inner Mongolia regions and was collected from Ordos City, Inner Mongolia Autonomous Region. The main oxides in the arsenic sandstone are silicon dioxide, aluminum oxide, iron oxide, and calcium oxide, with mass fractions of 57.31%, 15.7%, 8.67%, and 6.97%, respectively. The content of other oxides is below 10%. The proportions of different particle sizes are: <0.1mm (5.34%), 0.1-0.25mm (43.37%), 0.25-0.5mm (32.15%), 0.5-1mm (14.91%), and ≥1mm (4.23%).

[0083] The test used Class I F fly ash with high reactivity.

[0084] The test used S105 grade slag powder with the highest activity index.

[0085] The experimental calcium hydroxide was purchased from Tianjin Xinbote Chemical Co., Ltd. with a purity of 95%. It is in the form of white powder and is a first-class product.

[0086] The test water glass is sodium silicate water glass purchased from Henan Luboshi New Material Technology Co., Ltd., with a modulus of 1.2.

[0087] Preparation and testing of cementitious materials:

[0088] 1) Mixing ratio:

[0089] In order to explore the influence of different raw material ratios, the proportion of slag and fly ash in geopolymer was adjusted in a step-by-step manner. The increment of each group was set at 10%, and the arsenic sandstone content was reduced by 10% accordingly. A total of 7 groups of control experiments were designed.

[0090] The technical solution adopted by the present invention is: an industrial waste slag-arsenic sandstone composite cementitious material and a preparation method thereof, comprising 0-63.5% of arsenic sandstone, 0-31.75% of fly ash, 0-31.75% of slag, 20.6% of water glass, 0.5-1.5% of calcium hydroxide, 15% of water, and 0.4% of retarder.

[0091] The test numbers and material ratios are shown in Table 1:

[0092] Table 1 Test number and material mix ratio:

[0093]

[0094] 2) Material preparation:

[0095] Referring to the specification "Cement Slurry Mixer" (JC-T729-2005), the mixer's rotation speed is set to 140±5r / min (low speed) and 285±10r / min (high speed), in a clockwise direction, and the revolution speed is set to 62±5r / min (low speed) and 125±10r / min (high speed), in a counterclockwise direction.

[0096] Accurately weigh fly ash, slag, arsenic sandstone, solid activator, and retarder, stir these dry materials in a blender for 30 seconds, mix them evenly, and set aside. In this step, the mixing pot must be kept dry.

[0097] Following the above steps, weigh water and water glass and add them into the blender. Stir at low speed for 30 seconds and then switch to high speed stirring for 180 seconds.

[0098] 3) Specimen preparation:

[0099] With reference to the specification "Cement Slurry Mixer" (JC-T729-2005), the mixed slurry is fully poured into the 50mm✕50mm✕50mm test mold in batches.

[0100] Use a vibration table to form the product, refer to the standard "Technical Conditions for Electric Vibration Tables" (GB / T 13310-1991), the vibration frequency of the vibration table is stable at 50Hz, and the amplitude is 0.5mm~2mm.

[0101] 4) Specimen curing:

[0102] Before demolding the test piece, cover the mold with a glass plate, keeping the distance between the cover and the mold at 2mm~3mm. Demold the test piece 20h~24h after forming.

[0103] Refer to the specification "Cement Slurry Mixer" (JC-T729-2005), and cure for 28 days (28 days ± 8 hours) under standard curing conditions.

[0104] 5) Compression resistance test:

[0105] After curing for 28 days under standard curing conditions, the specimens were taken out and tested for compressive strength using a microcomputer-controlled electronic universal testing machine in groups of 3.

[0106] The compressive strength test of cementitious materials was conducted using a WAW-300B microcomputer-controlled electro-hydraulic servo universal testing machine. This machine has a maximum test force of 300 kN and a loading rate range of 0.2% to 5% FS / s. This instrument, directly connected to a computer system, can be used to determine the unconfined compressive strength of specimens.

[0107] To ensure the accuracy of the specimen strength, three parallel specimens were prepared and tested for each test. After the test, if the difference between any test value and the median value was greater than 15%, the maximum or minimum value was discarded, and the median value was used as the final test result. If the deviation between the two test values ​​and the median value exceeded 15%, the set of specimens was deemed invalid and required retesting. During the test, the instrument ensured that only axial pressure was applied to the specimen, while ensuring that no external lateral forces were applied. The test continued until the specimen failed due to being unable to withstand the increasing axial pressure. The maximum pressure value recorded was the unconfined compressive strength of the specimen.

[0108] 6) Test results:

[0109] The test numbers and their corresponding compressive strengths are shown in Table 2:

[0110] Table 2 Test numbers and their corresponding compressive strengths:

[0111]

[0112] 7) Comparative analysis of arsenic sandstone and standard sand:

[0113] Through experiments, it was found that the impact of arsenic sandstone on the material was small when the content was below 22.5% (E3 group). Therefore, when replacing arsenic sandstone with standard sand, E3 group was selected as the reference benchmark to study the feasibility of arsenic sandstone replacement. The specific mix ratio is shown in Table 3:

[0114]

[0115] The specific compressive strength values ​​are shown in Table 4:

[0116]

[0117] Compressive strength data show that as the alkali activator content gradually increases, the compressive strength gap between the arsenic sandstone material (Group E) and the standard sand material (Group I) shows a gradually narrowing trend. Under test conditions with sufficient alkali activator, the compressive strength of the arsenic sandstone material at 28 days was 41.4 MPa, and the compressive strength of the standard sand material was 42.1 MPa. The compressive strength of the E3 specimen with an appropriate amount of arsenic sandstone was only 1.7% lower than that of the specimen with the same amount of standard sand. It can be concluded that, under the premise of ensuring sufficient alkali activator, the compressive strength of geopolymer cementitious materials with an appropriate amount of arsenic sandstone is almost the same as that of geopolymer cementitious materials with standard sand added under the same conditions.

[0118] 8) Conclusion:

[0119] After testing, considering economic, engineering, and mechanical properties, the optimal dosage was selected: 22.5% arsenic sandstone, 20% fly ash, 20% slag, 20.6% water glass, 1.5% calcium hydroxide, 15% water, and 0.4% retarder (Group E3).

[0120] In summary, the present invention discloses an industrial waste slag-arsenic sandstone geopolymer cementitious material and a preparation method thereof. The material uses arsenic sandstone and industrial solid waste materials as main raw materials, and is mixed in a specific ratio to form a new type of geopolymer cementitious material. The research and development of this material aims to improve the utilization rate of industrial waste slag and arsenic sandstone, reduce the impact on the environment, and greatly reduce construction costs. During the preparation process, the present invention determined through systematic research and experiments that the optimal critical dosage of arsenic sandstone replacement rate is 22.5%. Without exceeding this dosage, the mechanical properties of the material can be kept basically unchanged, while the amount of arsenic sandstone used can be reduced. The feasibility of arsenic sandstone as an aggregate added to cementitious materials was verified through comparative analysis of arsenic sandstone and standard sand. This discovery is of great significance to the economic benefits and environmental friendliness of the material. Since industrial waste slag can be obtained near the construction site and arsenic sandstone can be sourced locally, the material cost and transportation cost are greatly reduced. The present invention also provides a preparation method that includes precise raw material proportioning, mixing, curing, and mechanical property testing to ensure material quality and performance. The industrial waste residue-arsenic sandstone composite cementitious material prepared by this method not only exhibits excellent mechanical properties but also has a low environmental impact and economic cost.

[0121] The above are limited to several preferred embodiments of the present invention, and their description is relatively specific and detailed, but it should not be understood as limiting the scope of the present invention. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. An industrial waste residue-arsenic sandstone geopolymer cementitious material, characterized in that: The following components are included in mass percentage: Arsenic sandstone 12.5-22.5%, fly ash 20-25%, slag 20-25%, water glass 20.6%, calcium hydroxide 0.5-1.5%, water 15%, retarder 0.4%; The arsenic sandstone comes from the Shanxi, Shaanxi and Inner Mongolia regions, and its main oxides are silicon dioxide, aluminum oxide, iron oxide and calcium oxide; their mass fractions are: silicon dioxide 50-65%, aluminum oxide 10-20%, iron oxide 5-10%, calcium oxide 5-10%, and the content of other oxides is less than 10%; The proportions of different particle sizes of arsenic sandstone are as follows: <0.1mm accounts for 3-8%, 0.1-0.25mm accounts for 35-50%, 0.25-0.5mm accounts for 25-40%, 0.5-1mm accounts for 10-20%, and ≥1mm accounts for 2-6%; The fly ash is Class I F fly ash, and the purity of the calcium hydroxide is 90-98%; The slag is slag powder with an activity index of S105; The water glass is sodium silicate water glass with a modulus of 1.0-1.4; The preparation method of the above-mentioned gelling material comprises the following steps: (1) Accurately weigh arsenic sandstone, fly ash, slag, calcium hydroxide, and retarder, and mix these dry materials in a blender for standby use; (2) Accurately weigh water and water glass, add them into the blender, stir at low speed and then change to high speed to make the mixture uniform; (3) Pour the stirred slurry into the test mold, seal and cure, demould and cure under standard curing conditions for the specified time, and then conduct mechanical property tests; The stirrer has an autorotation speed of 135±10 r / min and an orbital speed of 60±10 r / min during low-speed stirring; an autorotation speed of 280±15 r / min and an orbital speed of 120±15 r / min during high-speed stirring; The size of the test mold is 50mm×50mm×50mm. The test piece is demoulded between 20h and 24h after molding and cured under standard curing conditions for 28d±8h. The mechanical property test is an unconfined compressive strength test, which is performed using a microcomputer-controlled electro-hydraulic servo universal testing machine with a maximum test force of 300 kN, and a loading rate set at 2 mm / min.

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