A method for recycling and treating wastewater from a concrete mixing plant.

Abstract

This invention discloses a method for recycling and treating wastewater from concrete mixing plants, belonging to the field of solid wastewater recycling technology. It addresses the technical problems of low recyclability and ineffective recovery of fine aggregates and gel materials from concrete mixing plant wastewater during concrete processing. Specifically, the method includes the following steps: adding wastewater from the mixing plant to a settling tank, allowing it to settle for 1-3 days, separating the liquid to obtain settling slag and settling liquid. This invention regenerates and recovers solid impurities from concrete mixing plant wastewater, then combines it with fly ash to strengthen concrete. This not only effectively improves the plasticity and pumpability of concrete materials but also enhances their compressive strength and resistance to chloride ion penetration. Furthermore, the prepared recycled water can be directly used in concrete production and processing, regardless of the amount added.

Description

Technical Field

[0001] This invention relates to the field of solid wastewater recycling technology, specifically to a method for recycling and treating wastewater from a concrete mixing plant. Background Technology

[0002] Concrete mixing plants generate large amounts of highly alkaline wastewater with complex composition during production, equipment cleaning, and site maintenance. It is estimated that approximately 0.03-0.07 tons of wastewater are generated for every cubic meter of concrete produced. Large mixing plants can discharge tens of thousands of tons of wastewater annually. This type of wastewater contains high concentrations of suspended solids, high alkalinity, and soluble ions. Some wastewater is also mixed with grease and residual additives. If discharged directly without treatment, it will not only seriously pollute the soil and aquatic ecosystems but also cause a huge waste of water resources and usable solid waste.

[0003] The wastewater from existing concrete mixing plants contains a large amount of suspended solids, which may clog the capillary pores of the concrete, reducing its density and impermeability. In addition, the wastewater contains high concentrations of chloride and sulfate ions. High concentrations of chloride ions may cause corrosion of the steel reinforcement inside the concrete, while high concentrations of sulfate ions may trigger alkali-aggregate reaction, causing the concrete to expand and crack. As a result, the wastewater cannot be used in large quantities in the concrete preparation process, and about 30-40% of the fine aggregates and cementitious materials in the wastewater are not effectively recovered, resulting in resource loss. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recycling and treating wastewater from concrete mixing plants, which addresses the technical problems in the prior art where the recyclable consumption of wastewater from concrete mixing plants during concrete processing is low and the fine aggregates and gel materials in the wastewater are not effectively recovered.

[0005] The objective of this invention can be achieved through the following technical solution: a method for recycling and treating wastewater from a concrete mixing plant, comprising the following steps:

[0006] S1. Add the wastewater generated by the mixing plant to the settling tank, let it stand for 1-3 days to settle, separate the liquid to obtain settling residue and settling liquid; add a settling agent to the settling liquid, stir at room temperature for 60-80 minutes, and then treat it to obtain recycled water and filter residue.

[0007] The synthetic reaction mechanism for preparation using recycled water is as follows:

[0008] When treating the settling liquid, the hydrolysis products of calcium oxide and sodium aluminate in the settling agent form ettringite precipitate with sulfate ions and Friedel salt precipitate with chloride ions, thereby reducing the chloride and sulfate ion content in the settling liquid and preparing recycled water.

[0009] S2. Mix the filter residue and sediment, and sieve them using a sieve with a mesh size of 6-8mm to obtain large-diameter aggregate and small-diameter mortar.

[0010] S3. Regenerate the small-particle-size mortar to prepare recycled mortar.

[0011] S4. Mix large-diameter aggregates and crushed stone to obtain coarse aggregates; mix recycled mortar and fly ash to obtain admixtures; add coarse aggregates, fine aggregates, admixtures, cement and additives to a mixer and stir, adding recycled water while stirring. After adding all the water, mix for 10-15 minutes to obtain concrete.

[0012] Furthermore, in step S1, the ratio of the sediment to the sedimenting agent is 100mL:7-8g, and the sedimenting agent is composed of calcium oxide and sodium aluminate in a weight ratio of 2.5:1. The post-treatment includes: after the reaction is completed, using a centrifuge to separate the solid and liquid to obtain recycled water and filter residue.

[0013] Furthermore, the preparation method of recycled slurry is as follows: add recycled water to small-particle-size mortar to obtain a mixed slurry; add cement to the mixed slurry at room temperature and stir for 20-30 minutes, then add silica sol, keep warm and stir for 40-50 minutes, and then perform post-treatment to obtain pretreated slurry; after the pretreated slurry is carbonized with carbon dioxide to prepare carbonized slurry, the carbonized slurry is further treated with modified polysiloxane to prepare recycled slurry.

[0014] The synthesis reaction mechanism of carbonized slurry sand is as follows:

[0015] During the reaction, water glass dissociates in water into sodium ions and silicate or more complex oligomeric silicates, which interact with nano-SiO2 to form a stable silica sol. Cement reacts with water to generate CSH gel and calcium hydroxide. The active silica in the silica sol reacts with the calcium hydroxide generated by cement hydration to form additional CSH gel. The silica sol fills the pores of inorganic particles in the mortar, increasing density and enhancing the interfacial bonding between aggregates and cementitious materials. After carbonation, the carbonation of CSH gel forms calcium carbonate and silica gel, which together constitute a new cementing phase. Silica in the silica sol promotes carbon dioxide dissolution in an alkaline environment and participates in the formation of calcium silicate carbonate complex, forming a repair and reinforcement structure on the pretreated mortar, thus preparing carbonized mortar.

[0016] Furthermore, the solid content of the mixed slurry is 35-45%; the weight ratio of the mixed slurry, cement, and silica sol is 100:3-5:80-90; the post-treatment includes: after mixing, filtration, spreading the filter cake evenly on the drying field, and drying it to a moisture content of 30-40% to obtain pre-treated slurry sand.

[0017] Furthermore, the preparation method of silica sol is as follows: mix nano-silica and drinking water, ultrasonically disperse for 30-50 min, add water glass to the reaction system, and continue ultrasonic dispersion for 40-60 min to obtain silica sol. The ratio of nano-silica, drinking water and water glass is 20-25 g: 100 mL: 8-12 g, and the modulus of water glass is 2.0-2.8.

[0018] Furthermore, the preparation method of carbonized slurry is as follows: the pretreated slurry is spread in a carbonization box, and carbon dioxide is introduced into the carbonization box at room temperature to replace the air inside, so that the internal pressure is stabilized at 0.35-0.45MPa. The pressure is maintained for 20-24 hours, the pressure is reduced to normal pressure, and the material is discharged to obtain carbonized slurry.

[0019] Furthermore, the recycled slurry is obtained through the following steps:

[0020] A1. Under inert gas protection, hydroxyl silicone oil and toluene are mixed and stirred. The temperature of the reaction system is raised to 60-70℃. Propyltriethoxysilane isocyanate is added to the reaction system. The reaction is kept at the temperature for 60-80 min. After post-treatment, modified polysiloxane is obtained.

[0021] A2. Mix carbonized slurry sand, modified polysiloxane, and recycled water. Raise the temperature of the reaction system to 60-70℃ and mix for 40-60 minutes. Then, perform post-treatment to obtain recycled slurry sand.

[0022] The synthesis reaction mechanism of recycled slurry is as follows:

[0023] During the reaction, the hydroxyl groups on the hydroxyl silicone oil molecules condense with the isocyanate groups on the propyltriethoxysilane molecules, forming a triethoxysilane modification on the siloxane chain of the hydroxyl silicone oil, thus preparing a modified polysiloxane. Then, in an aqueous environment, the siloxane bonds on the modified polysiloxane molecules hydrolyze to form silanol groups. The silanol groups react with the active reaction sites on the surface of the carbonized slurry sand particles to form chemical bonds, thus preparing a regenerated slurry sand.

[0024] Further, in step A1, the ratio of hydroxyl silicone oil to toluene is 1g:6mL, and the amount of propyltriethoxysilane is 0.95 times the molar amount of hydroxyl in the hydroxyl silicone oil. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is raised to 80-90℃, and low-boiling substances are removed by vacuum evaporation to obtain modified polysiloxane. In step A2, the ratio of carbonized slurry sand, modified polysiloxane, and recycled water is 7g:1.5-1.8g:5mL. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, and it is spread out in a drying yard to air dry to obtain regenerated slurry sand.

[0025] Furthermore, in step S4, the weight ratio of the large-diameter aggregate to the crushed stone is 1:6, and the crushed stone is composed of small crushed stone with a particle size of 5-10mm, medium crushed stone with a particle size of 10-20mm, and large crushed stone with a particle size of 20-30mm in a weight ratio of 2:3:5; the weight ratio of the recycled slurry sand to the fly ash is 4:9.

[0026] Furthermore, the weight ratio of the coarse aggregate, fine aggregate, admixture, cement, additives, and recycled water is 850-950:850-950:90-110:150-160:6-7:160-170. The fine aggregate is composed of manufactured sand with a particle size of 2-3 mm and stone chips with a particle size of 3-5 mm in a weight ratio of 1:1. The additives are composed of water-reducing agent and retarder in a weight ratio of 3:2. The water-reducing agent is a polycarboxylate water-reducing agent, and the retarder is any one of tartaric acid, potassium tartrate, and calcium tartrate.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention involves allowing the wastewater containing concrete mortar from a concrete mixing plant to settle, then treating the sediment with a settling agent. This effectively reduces the impact on concrete processing, allowing the wastewater to be directly used in concrete production without being affected by the amount added. Furthermore, by treating and regenerating the mechanical impurities in the wastewater and then combining it with fly ash to form an admixture, the invention strengthens the concrete material. This not only effectively improves the plasticizing and pumpability properties but also enhances the compressive strength and resistance to chloride ion penetration.

[0029] 2. The polysiloxane-modified surface of the recycled slurry of this invention forms a ball-bead effect, modifying the sliding properties between particles. The slow reaction of the pozzolanic material reduces water consumption during initial hydration, maintaining slurry fluidity. Furthermore, the recycled slurry contains a certain amount of cement hydration products and unhydrated cement particles, which can continue to hydrate in concrete, contributing to its strength development. Simultaneously, the addition of recycled slurry improves the concrete's gradation, density, and compressive strength. Fly ash, with its pozzolanic activity, can react with hydrogen produced during cement hydration. Calcium oxide undergoes a secondary hydration reaction, generating gel products such as hydrated calcium silicate, which fill the pores inside the concrete, improving the concrete's density and compressive strength. The polysiloxane modified on the surface of the recycled mortar forms a hydrophobic film on the aggregate surface, which can block the diffusion path of chloride ions. Furthermore, the calcium carbonate and silica gel modified on the surface of the recycled mortar fill the capillary pores. The secondary hydration reaction of fly ash can generate gel products such as hydrated calcium silicate, which fill the pores inside the concrete, further reducing the channels for chloride ion penetration, thereby improving the concrete's resistance to chloride ion penetration. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flow chart of the process for recycling and treating wastewater from a concrete mixing plant according to the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In this invention, the nano-silica is selected from Qinghe County Chaotai Metal Materials Co., Ltd., with a particle size of 20,000 mesh and a silicon content of ≥99.9%;

[0034] In this invention, the hydroxyl silicone oil is selected from Jinan Hailan Chemical Co., Ltd., with an effective ingredient content of 99% and a density of 0.95 g / cm³. 3 The hydroxyl content is 6-8%;

[0035] In this invention, the cement is slag silicate cement with a compressive strength of not less than 32.5 MPa;

[0036] In this invention, the polycarboxylate superplasticizer is selected from Jinan Quanchi New Materials Co., Ltd., and has a solid content of 99%.

[0037] Example 1

[0038] Please see Figure 1 This embodiment provides a method for recycling and treating wastewater from a concrete mixing plant, including the following steps:

[0039] Step 1: Wastewater Settling

[0040] Wastewater from the mixing plant is added to a settling tank and allowed to settle for one day. The supernatant is then pumped out, and the slurry is filtered through a filter cloth to obtain settling residue and filtrate. The filtrate is then mixed with the supernatant to obtain settling liquid.

[0041] Calcium oxide and sodium aluminate were mixed evenly at a weight ratio of 2.5:1 to obtain a settling agent;

[0042] The ratio of settling liquid to settling agent is 100 mL: 7 g. The settling agent is added to the settling liquid and stirred at room temperature for 60 minutes. After the reaction is complete, the solid and liquid are separated by centrifugation to obtain recycled water and filter residue.

[0043] Step 2: Slurry and residue screening

[0044] The filter residue and sediment residue are mixed and screened using a 6mm sieve. The large-diameter aggregate at the top of the sieve is washed with recycled water to obtain large-diameter aggregate and small-diameter mortar.

[0045] Step 3: Slurry and sand recycling

[0046] Reclaimed water was added to the small-particle-size mortar to obtain a mixed slurry with a solid content of 35%.

[0047] Weigh out 200g of nano-silica and 1L of drinking water and add them to the reaction flask. At room temperature, sonicate for 30min. Add 80g of water glass with a modulus of 2.0 to the reaction flask and continue to sonicate for 40min to obtain silica sol.

[0048] Weigh out 1 kg of mixed slurry and 30 g of cement and add them to the mixer. Mix at room temperature for 20 minutes. Add 800 g of silica sol to the mixer and mix for 40 minutes. Filter the mixture and spread the filter cake evenly on the drying field. Dry the mixture until the moisture content is 30% to obtain the pretreated slurry.

[0049] The pretreated slurry was spread in a carbonization box. At room temperature, carbon dioxide was introduced into the carbonization box to replace the air inside, so that the internal pressure was stabilized at 0.35MPa. The pressure was maintained for 20 hours, then the pressure was reduced to atmospheric pressure, and the material was discharged to obtain carbonized slurry.

[0050] Weigh out 100g of hydroxyl silicone oil and 600mL of toluene, add them to a nitrogen-protected reaction flask, and stir. Raise the temperature of the reaction system to 60℃, and proceed according to n... 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of propyltriethoxysilane to be added, and add it to the reaction flask. Keep the reaction at a constant temperature for 60 min. Raise the temperature of the reaction flask to 80℃, remove the low-boiling substances by vacuum distillation, and then process the modified polysiloxane to obtain the modified polysiloxane.

[0051] Weigh out 700g of carbonized slurry sand, 150g of modified polysiloxane, and 500mL of recycled water. Add them to a mixer and stir to mix. Raise the mixer temperature to 60℃ and stir for 40 minutes. Then lower the mixer temperature to room temperature and spread it out on a drying field to air dry, thus obtaining recycled slurry sand.

[0052] Step 4: Prepare concrete

[0053] Small crushed stone with a particle size of 5-10mm, medium crushed stone with a particle size of 10-20mm, and large crushed stone with a particle size of 20-30mm are mixed in a weight ratio of 2:3:5 to obtain crushed stone; large-particle aggregate and crushed stone are mixed in a weight ratio of 1:6 to obtain coarse aggregate.

[0054] The recycled slurry sand and fly ash are mixed at a weight ratio of 4:9 to obtain the admixture;

[0055] Fine aggregate is obtained by mixing manufactured sand with a particle size of 2-3 mm and stone chips with a particle size of 3-5 mm in a weight ratio of 1:1.

[0056] Polycarboxylate superplasticizer and potassium tartrate retarder are mixed in a weight ratio of 3:2 to obtain the admixture;

[0057] Weigh out the following by weight: 850 parts coarse aggregate, 850 parts fine aggregate, 90 parts admixture, 150 parts cement, and 6 parts additives. Add these to the mixer and stir. While stirring, add 160 parts recycled water. After adding all the water, mix for 10 minutes to obtain concrete.

[0058] Example 2

[0059] Please see Figure 1 This embodiment provides a method for recycling and treating wastewater from a concrete mixing plant, including the following steps:

[0060] Step 1: Wastewater Settling

[0061] Wastewater from the mixing plant is added to a settling tank and allowed to settle for 2 days. The supernatant is then pumped out, and the slurry is filtered through a filter cloth to obtain settling residue and filtrate. The filtrate is then mixed with the supernatant to obtain settling liquid.

[0062] Calcium oxide and sodium aluminate were mixed evenly at a weight ratio of 2.5:1 to obtain a settling agent;

[0063] The ratio of settling liquid to settling agent is 100 mL: 7.5 g. The settling agent is added to the settling liquid and stirred at room temperature for 70 min. After the reaction is complete, the solid and liquid are separated by centrifugation to obtain recycled water and filter residue.

[0064] Step 2: Slurry and residue screening

[0065] The filter residue and sediment residue are mixed and screened using a 7mm sieve. The large-diameter aggregate at the top of the sieve is washed with recycled water to obtain large-diameter aggregate and small-diameter mortar.

[0066] Step 3: Slurry and sand recycling

[0067] Reclaimed water was added to the small-particle-size mortar to obtain a mixed slurry with a solid content of 40%.

[0068] Weigh out 225g of nano-silica and 1L of drinking water and add them to the reaction flask. At room temperature, sonicate for 4min. Add 100g of water glass with a modulus of 2.4 to the reaction flask and continue to sonicate for 50min to obtain silica sol.

[0069] Weigh out 1 kg of mixed slurry and 40 g of cement and add them to the mixer. Mix at room temperature for 25 minutes. Add 850 g of silica sol to the mixer and mix for 45 minutes. Filter the mixture and spread the filter cake evenly on the drying field. Dry the mixture until the moisture content is 35% to obtain the pretreated slurry.

[0070] The pretreated slurry was spread in a carbonization box. At room temperature, carbon dioxide was introduced into the carbonization box to replace the air inside, so that the internal pressure was stabilized at 0.40 MPa. The pressure was maintained for 22 hours, then the pressure was reduced to atmospheric pressure, and the material was discharged to obtain carbonized slurry.

[0071] Weigh out 100g of hydroxyl silicone oil and 600mL of toluene, add them to a nitrogen-protected reaction flask, and stir. Raise the temperature of the reaction system to 65℃, and proceed according to n... 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of propyltriethoxysilane to be added, and add it to the reaction flask. Keep the reaction at a constant temperature for 70 min. Raise the temperature of the reaction flask to 85℃, remove the low-boiling substances by vacuum distillation, and then process the modified polysiloxane to obtain the modified polysiloxane.

[0072] Weigh out 700g of carbonized slurry sand, 165g of modified polysiloxane, and 500mL of recycled water. Add them to a mixer and stir to mix. Raise the mixer temperature to 65℃ and stir for 50 minutes. Then lower the mixer temperature to room temperature and spread it out on a drying field to air dry, thus obtaining recycled slurry sand.

[0073] Step 4: Prepare concrete

[0074] Small crushed stone with a particle size of 5-10mm, medium crushed stone with a particle size of 10-20mm, and large crushed stone with a particle size of 20-30mm are mixed in a weight ratio of 2:3:5 to obtain crushed stone; large-particle aggregate and crushed stone are mixed in a weight ratio of 1:6 to obtain coarse aggregate.

[0075] The recycled slurry sand and fly ash are mixed at a weight ratio of 4:9 to obtain the admixture;

[0076] Fine aggregate is obtained by mixing manufactured sand with a particle size of 2-3 mm and stone chips with a particle size of 3-5 mm in a weight ratio of 1:1.

[0077] The admixture is obtained by mixing polycarboxylate superplasticizer and calcium tartrate retarder in a weight ratio of 3:2.

[0078] Weigh out the following by weight: 900 parts coarse aggregate, 900 parts fine aggregate, 100 parts admixture, 155 parts cement, and 6.5 parts additives. Add these to the mixer and stir. While stirring, add 165 parts recycled water. After adding all the water, mix for 13 minutes to obtain concrete.

[0079] Example 3

[0080] Please see Figure 1 This embodiment provides a method for recycling and treating wastewater from a concrete mixing plant, including the following steps:

[0081] Step 1: Wastewater Settling

[0082] Wastewater from the mixing plant is added to a settling tank and allowed to settle for 3 days. The supernatant is then pumped out, and the slurry is filtered through a filter cloth to obtain settling residue and filtrate. The filtrate is then mixed with the supernatant to obtain settling liquid.

[0083] Calcium oxide and sodium aluminate were mixed evenly at a weight ratio of 2.5:1 to obtain a settling agent;

[0084] The ratio of settling liquid to settling agent is 100 mL: 8 g. The settling agent is added to the settling liquid and stirred at room temperature for 80 minutes. After the reaction is complete, the solid and liquid are separated by centrifugation to obtain recycled water and filter residue.

[0085] Step 2: Slurry and residue screening

[0086] The filter residue and sediment residue are mixed and screened using a sieve with an 8mm aperture. The large-diameter aggregate at the top of the sieve is washed with recycled water to obtain large-diameter aggregate and small-diameter mortar.

[0087] Step 3: Slurry and sand recycling

[0088] Reclaimed water was added to the small-particle-size mortar to obtain a mixed slurry with a solid content of 45%.

[0089] Weigh out 250g of nano-silica and 1L of drinking water and add them to the reaction flask. At room temperature, sonicate for 50min. Add 120g of water glass with a modulus of 2.8 to the reaction flask and continue to sonicate for 60min to obtain silica sol.

[0090] Weigh out 1 kg of mixed slurry and 50 g of cement and add them to the mixer. Mix at room temperature for 30 minutes. Add 900 g of silica sol to the mixer and mix for 50 minutes. Filter the mixture and spread the filter cake evenly on the drying field. Dry the mixture until the moisture content is 40% to obtain the pretreated slurry.

[0091] The pretreated slurry was spread in a carbonization box. At room temperature, carbon dioxide was introduced into the carbonization box to replace the air inside, so that the internal pressure was stabilized at 0.45MPa. The pressure was maintained for 24 hours, then the pressure was reduced to atmospheric pressure, and the material was discharged to obtain carbonized slurry.

[0092] Weigh out 100g of hydroxyl silicone oil and 600mL of toluene, add them to a nitrogen-protected reaction flask, and stir. Raise the temperature of the reaction system to 70℃, and proceed according to n... 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of propyltriethoxysilane to be added, and add it to the reaction flask. Keep the reaction at a constant temperature for 80 min. Raise the temperature of the reaction flask to 90℃, remove the low-boiling substances by vacuum distillation, and then process the modified polysiloxane to obtain the modified polysiloxane.

[0093] Weigh out 700g of carbonized slurry sand, 180g of modified polysiloxane, and 500mL of recycled water. Add them to a mixer and stir to mix. Raise the mixer temperature to 70℃ and stir for 60 minutes. Then lower the mixer temperature to room temperature and spread it out on a drying field to air dry, thus obtaining recycled slurry sand.

[0094] Step 4: Prepare concrete

[0095] Small crushed stone with a particle size of 5-10mm, medium crushed stone with a particle size of 10-20mm, and large crushed stone with a particle size of 20-30mm are mixed in a weight ratio of 2:3:5 to obtain crushed stone; large-particle aggregate and crushed stone are mixed in a weight ratio of 1:6 to obtain coarse aggregate.

[0096] The recycled slurry sand and fly ash are mixed at a weight ratio of 4:9 to obtain the admixture;

[0097] Fine aggregate is obtained by mixing manufactured sand with a particle size of 2-3 mm and stone chips with a particle size of 3-5 mm in a weight ratio of 1:1.

[0098] The admixture is obtained by mixing polycarboxylate superplasticizer and tartaric acid retarder in a weight ratio of 3:2.

[0099] Weigh out the following by weight: 950 parts coarse aggregate, 950 parts fine aggregate, 110 parts admixture, 160 parts cement, and 7 parts additives. Add these to the mixer and stir. While stirring, add 170 parts recycled water. After adding all the water, mix for 15 minutes to obtain concrete.

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 3 is that in step 1, the weight ratio of calcium oxide to sodium aluminate is 1.5:1.

[0102] Comparative Example 2

[0103] The difference between this comparative example and Example 3 is that the carbonized slurry in step 3 is used instead of the recycled slurry in step 4.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 3 is that water glass was not added during the silica sol preparation process in step 3.

[0106] Comparative Example 4

[0107] The difference between this comparative example and Example 3 is that no recycled slurry was added in step 4.

[0108] Performance testing:

[0109] The slump and slump loss over time of the concrete materials prepared in Examples 1-3 and Comparative Examples 1-4 were determined using the standard GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures".

[0110] Referring to the specimen preparation and curing in the standard GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the concrete materials prepared in Examples 1-3 and Comparative Examples 1-4 were prepared into test samples, and the compressive strength of the test samples was measured after 7 days and 28 days of curing.

[0111] The unsteady chloride ion migration coefficients of the test samples prepared by Examples 1-3 and Comparative Examples 1-4 on day 28 were determined in accordance with the standard GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". The specific test data are shown in Table 1 below.

[0112] Table 1 - Performance Test Data of Samples

[0113]

[0114] Data Analysis:

[0115] Comparative analysis of the data in Table 1 shows that the concrete material prepared by this invention has a slump value of 235 mm, a slump loss over time reduced to 20 mm, a 7-day compressive strength of 34.2 MPa, a 28-day compressive strength of 46.7 MPa, and a non-steady-state chloride ion migration coefficient reduced to 15 × 10⁻⁶. -14 m 2The performance test data were all better than the comparative example, indicating that the present invention regenerates and recovers solid impurities in the wastewater of concrete mixing plants and combines them with fly ash to strengthen concrete. This not only effectively improves the plasticity and pumpability of concrete materials, but also improves their compressive strength and resistance to chloride ion penetration. Furthermore, the wastewater without solid impurities is settled, effectively reducing its impact on concrete processing, allowing it to be directly used in concrete production and processing, regardless of the amount added.

[0116] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for recycling and treating wastewater from a concrete mixing plant, characterized in that, Includes the following steps: S1. Add the wastewater generated by the mixing plant to the settling tank, let it stand for 1-3 days to settle, separate the liquids to obtain settling residue and settling liquid. Add a settling agent to the settling liquid, stir at room temperature for 60-80 minutes, and then perform post-treatment to obtain recycled water and filter residue. S2. Mix the filter residue and sediment, and sieve them using a sieve with a mesh size of 6-8mm to obtain large-diameter aggregate and small-diameter mortar. S3. Add recycled water to the small-particle-size mortar to obtain a mixed slurry; at room temperature, add cement to the mixed slurry and stir for 20-30 minutes, then add silica sol, keep warm and stir for 40-50 minutes, and then perform post-treatment to obtain pretreated slurry sand; after the pretreated slurry sand is carbonized with carbon dioxide to prepare carbonized slurry sand, the carbonized slurry sand is further treated with modified polysiloxane to prepare recycled slurry sand; S4. Mix large-diameter aggregates and crushed stone to obtain coarse aggregates; mix recycled mortar and fly ash to obtain admixtures; add coarse aggregates, fine aggregates, admixtures, cement and additives to a mixer and mix while adding recycled water. After adding all the water, mix for 10-15 minutes to obtain concrete. The method for preparing silica sol is as follows: nano-silica and drinking water are mixed and ultrasonically dispersed for 30-50 min. Water glass is added to the reaction system and ultrasonically dispersed for 40-60 min to obtain silica sol. The ratio of nano-silica, drinking water and water glass is 20-25 g: 100 mL: 8-12 g, and the modulus of water glass is 2.0-2.

8. The modified polysiloxane is prepared as follows: under inert gas protection, hydroxyl silicone oil and toluene are mixed and stirred, the temperature of the reaction system is raised to 60-70℃, propyltriethoxysilane isocyanate is added to the reaction system, the reaction is kept at this temperature for 60-80 min, and then post-processed to obtain the modified polysiloxane. The ratio of hydroxyl silicone oil to toluene is 1g:6mL, and the amount of propyltriethoxysilane is 0.95 times the molar amount of hydroxyl groups in the hydroxyl silicone oil.

2. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, In step S1, the ratio of the sediment to the sedimentation agent is 100mL:7-8g, and the sedimentation agent is composed of calcium oxide and sodium aluminate in a weight ratio of 2.5:

1. The post-treatment includes: after the reaction is completed, solid-liquid separation is performed using a centrifuge to obtain recycled water and filter residue.

3. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, The solid content of the mixed slurry is 35-45%; the weight ratio of the mixed slurry, cement, and silica sol is 100:3-5:80-90. The post-treatment includes: after mixing, filtration, spreading the filter cake evenly on the drying field, and drying it to a moisture content of 30-40% to obtain pretreated slurry sand.

4. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, The preparation method of carbonized slurry sand is as follows: the pretreated slurry sand is spread in the carbonization box, and carbon dioxide is introduced into the carbonization box at room temperature to replace the air inside, so that the internal pressure is stabilized at 0.35-0.45MPa. The pressure is maintained for 20-24 hours, the pressure is reduced to normal pressure, and the material is discharged to obtain carbonized slurry sand.

5. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, The molding method of recycled slurry sand is as follows: carbonized slurry sand, modified polysiloxane, and recycled water are stirred and mixed. The temperature of the reaction system is raised to 60-70℃, stirred and mixed for 40-60 minutes, and then post-treated to obtain recycled slurry sand.

6. The method for recycling and treating wastewater from a concrete mixing plant according to claim 5, characterized in that, The ratio of carbonized slurry sand, modified polysiloxane, and recycled water is 7g:1.5-1.8g:5mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, and the system is spread out in a drying field to air dry, thereby obtaining regenerated slurry sand.

7. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, In step S4, the weight ratio of the large-diameter aggregate to the crushed stone is 1:6, and the crushed stone is composed of small crushed stone with a particle size of 5-10mm, medium crushed stone with a particle size of 10-20mm, and large crushed stone with a particle size of 20-30mm in a weight ratio of 2:3:5; the weight ratio of the recycled slurry sand to the fly ash is 4:

9.

8. The method for recycling and treating wastewater from a concrete mixing plant according to claim 1, characterized in that, The weight ratio of coarse aggregate, fine aggregate, admixture, cement, additives, and recycled water is 850-950:850-950:90-110:150-160:6-7:160-170. The fine aggregate is composed of manufactured sand with a particle size of 2-3 mm and stone chips with a particle size of 3-5 mm in a weight ratio of 1:

1. The additives are composed of water-reducing agent and retarder in a weight ratio of 3:

2. The water-reducing agent is a polycarboxylate water-reducing agent, and the retarder is any one of tartaric acid, potassium tartrate, and calcium tartrate.

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