Recycling treatment method for production wastewater of concrete mixing plant

Abstract

The invention discloses a method for recycling and treating production wastewater of a concrete mixing plant, belongs to the technical field of solid-containing wastewater recovery, and aims to solve the technical problems that the recyclable consumption of the wastewater of the concrete mixing plant in the concrete processing process is low and fine aggregates and gel materials in the wastewater are not effectively recovered in the prior art. The method specifically comprises the following steps: adding the wastewater generated by the mixing plant into a settling tank, standing and settling for 1-3 days, and separating liquid to obtain settled slag and settled liquid. Solid impurities in the wastewater of the concrete mixing plant are regenerated and recycled and then are combined with fly ash to reinforce concrete; according to the present invention, the plasticizing performance and the pumpability of the concrete material are effectively improved, the compressive strength and the chloride ion permeation resistance of the concrete material are improved, and the prepared reuse water can be directly used for concrete production and processing, and is not affected by the addition amount.

Description

Technical Field

[0001] The present invention relates to the technical field of solid wastewater recovery, and in particular to a method for recovering and utilizing production wastewater from a concrete mixing station. Background Art

[0002] During the production, equipment cleaning and site maintenance processes, concrete mixing plants will produce a large amount of highly alkaline wastewater with complex components. It is estimated that every cubic meter of concrete produced generates about 0.03-0.07 tons of wastewater. The annual wastewater discharge of large mixing plants can reach tens of thousands of tons. This type of wastewater contains high concentrations of suspended solids, high alkalinity and soluble ions. Some wastewater is also mixed with oil and residual admixtures. If it is discharged directly without treatment, it will not only seriously pollute the soil and water ecology, but also cause huge waste of water resources and usable solid waste.

[0003] The wastewater from existing concrete mixing plants contains a large amount of suspended matter, which can clog the pores of concrete, reducing its density and impermeability. Furthermore, the wastewater contains high concentrations of chloride and sulfate ions. High concentrations of chloride ions can cause corrosion of steel bars inside the concrete, while high concentrations of sulfate ions can trigger an alkali-aggregate reaction, causing concrete expansion and cracking. Consequently, the wastewater cannot be used in large quantities in the concrete preparation process. Furthermore, approximately 30-40% of the fine aggregate and cementitious materials in the wastewater are not effectively recovered, resulting in resource loss. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for recycling and utilizing wastewater produced by a concrete mixing station, so as to solve the technical problems in the prior art of low recyclable consumption of wastewater produced by a concrete mixing station during concrete processing and ineffective recovery of fine aggregate and gel materials in the wastewater.

[0005] The purpose of the present invention can be achieved by the following technical solution: A method for recycling and treating wastewater produced by a concrete mixing station, comprising the following steps:

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

[0007] The synthetic reaction mechanism of recycled water preparation is:

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

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

[0010] S3, regenerating the small-particle mortar to prepare regenerated mortar sand;

[0011] S4. Mix large-size aggregate and crushed stone to obtain coarse aggregate; mix recycled mortar sand and fly ash to obtain admixture; add coarse aggregate, fine aggregate, admixture, cement and admixture into a mixer and stir, while adding recycled water while stirring. After the addition is completed, mix for 10-15 minutes to obtain concrete.

[0012] Furthermore, in step S1, the ratio of the sedimentation liquid to the sedimentation agent is 100 mL:7-8 g, and the sedimentation agent is composed of calcium oxide and sodium metaaluminate 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 regenerated mortar sand is as follows: adding recycled water to small-particle mortar to obtain a mixed slurry; adding cement to the mixed slurry at room temperature, stirring and mixing for 20-30 minutes, then adding silica sol thereto, stirring and keeping warm for 40-50 minutes, and post-treating to obtain pre-treated mortar sand; after the pre-treated mortar sand is carbonized with carbon dioxide to prepare carbonized mortar sand, the carbonized mortar sand is re-treated with modified polysiloxane to prepare regenerated mortar sand.

[0014] The synthetic reaction mechanism of carbonized slurry sand is:

[0015] During the reaction process, water glass dissociates into sodium ions and silicate or more complex oligomeric silicates in water, which interact with nano-SiO2 to form a stable silica sol. Cement reacts with water to form 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, improves the density, and strengthens the interface bonding between the aggregate and the cementitious material. After carbonization, the carbonization of the CSH gel forms calcium carbonate and silica gel to form a new cementing phase. The silica in the silica sol promotes the dissolution of carbon dioxide in an alkaline environment and participates in the formation of a calcium silicate carbonate complex, forming a repair and reinforcement structure on the pre-treated mortar sand to prepare carbonized mortar sand.

[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-processing includes: after stirring is completed, filtering, spreading the filter cake evenly on the drying yard, and drying to a moisture content of 30-40% to obtain pre-treated slurry sand.

[0017] Furthermore, the preparation method of silica sol is: mixing nano-silica and drinking water, ultrasonically dispersing for 30-50 minutes, adding water glass to the reaction system, and continuing ultrasonic dispersion for 40-60 minutes to obtain silica sol, wherein the dosage ratio of the nano-silica, drinking water and water glass is 20-25g:100mL:8-12g, and the modulus of the water glass is 2.0-2.8.

[0018] Furthermore, the preparation method of carbonized slurry sand is as follows: the pre-treated slurry sand is spread in a carbonization box, and at room temperature, carbon dioxide is introduced into the carbonization box to replace the internal air, 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.

[0019] Furthermore, the regenerated slurry sand is obtained by processing the following steps:

[0020] A1. Under inert gas protection, hydroxy silicone oil and toluene were mixed and stirred, the reaction system temperature was raised to 60-70°C, and isocyanatepropyltriethoxysilane was added to the reaction system. The reaction was kept warm for 60-80 minutes, and post-processed to obtain modified polysiloxane;

[0021] A2. Stir and mix the carbonized mortar sand, modified polysiloxane and recycled water, increase the temperature of the reaction system to 60-70°C, stir and mix for 40-60 minutes, and post-treat to obtain regenerated mortar sand.

[0022] The synthetic reaction mechanism of regenerated slurry sand is:

[0023] During the reaction, the hydroxyl groups on the hydroxy silicone oil molecules condense with the isocyanate groups on the isocyanatepropyltriethoxysilane molecules to form triethoxysilane modifications on the siloxane chains of the hydroxy silicone oil, thereby preparing modified polysiloxane. Then, in an aqueous environment, the siloxane bonds on the modified polysiloxane molecules are hydrolyzed to form silanol groups, which react with the active reaction sites on the surface of the carbonized slurry sand particles to form chemical bonds, thereby preparing regenerated slurry sand.

[0024] Furthermore, in step A1, the amount ratio of the hydroxy silicone oil and toluene is 1g:6mL, the amount of the isocyanatepropyltriethoxysilane is 0.95 times the molar amount of hydroxyl groups in the hydroxy silicone oil, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is raised to 80-90°C, and low-boiling substances are removed under reduced pressure to obtain modified polysiloxane; in step A2, the amount ratio of the carbonized slurry, modified polysiloxane and recycled water is 7g:1.5-1.8g:5mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, and it is spread out in a drying yard to dry itself to obtain regenerated slurry.

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

[0026] Furthermore, the weight ratio of the coarse aggregate, fine aggregate, admixture, cement, admixture and recycled water is 850-950:850-950:90-110:150-160:6-7:160-170, the fine aggregate is composed of machine-made 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 admixture is composed of a water reducer and a retarder in a weight ratio of 3:2, the water reducer is a polycarboxylate water reducer, 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. The present invention uses a precipitant to treat the sedimentation liquid after the wastewater containing concrete mortar generated by the concrete mixing station is allowed to settle, which can effectively reduce the influence of the wastewater on concrete processing, so that the wastewater can be directly used in concrete production and processing without being affected by the amount of addition. In addition, the mechanical impurities in the wastewater of the concrete mixing station are treated and regenerated, and then the mechanical impurities are combined with fly ash to form an admixture to strengthen the concrete material, which not only effectively improves the plasticizing performance and pumpability, but also improves its compressive strength and resistance to chloride ion penetration.

[0029] 2. The polysiloxane modified on the surface of the regenerated mortar sand of the present invention forms a ball effect, which improves the sliding properties between the particles, while the volcanic ash reacts slowly, reducing the water consumption of hydration in the initial stage and maintaining the fluidity of the slurry. In addition, the regenerated mortar sand contains a certain amount of cement hydration products and unhydrated cement particles. These components can continue to hydrate in the concrete and contribute to the strength development of the concrete. At the same time, the addition of regenerated mortar sand can improve the gradation of concrete, increase the density and compressive strength of concrete, and the fly ash has volcanic ash activity and can react with the hydrogen generated by cement hydration to form a hygroscopic concrete. Calcium oxide undergoes a secondary hydration reaction to generate gel products such as hydrated calcium silicate, which fill the pores inside the concrete and improve the density and compressive strength of the concrete. The polysiloxane modified on the surface of the recycled mortar sand forms a hydrophobic film on the surface of the aggregate, which can block the diffusion path of chloride ions. The calcium carbonate modified on the surface of the recycled mortar sand and the silica gel fill the capillary pores. The secondary hydration reaction of the fly ash can generate gel products such as hydrated calcium silicate, which fill the pores inside the concrete and further reduce the channels for chloride ion penetration, thereby improving the concrete's resistance to chloride ion penetration. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a process flow chart for recycling and utilizing wastewater produced by a concrete mixing station according to the present invention. DETAILED DESCRIPTION

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] In the present invention, the nano silicon dioxide is selected from Qinghe Chaotai Metal Materials Co., Ltd., with a particle size / mesh number of 20000 mesh and a silicon content of ≥99.9%;

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

[0035] In the present invention, the cement is slag Portland cement, and the compressive strength is not less than 32.5 MPa;

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

[0037] Example 1

[0038] See also Figure 1 This embodiment provides a method for recycling and treating wastewater produced by a concrete mixing station, comprising the following steps:

[0039] Step 1: Wastewater sedimentation

[0040] The wastewater generated by the mixing station is added to the sedimentation tank and allowed to settle for 1 day. The supernatant liquid is extracted by a water pump. The slurry is then filtered through a filter cloth to obtain sediment residue and filtrate. The filtrate is mixed with the supernatant liquid to obtain sediment liquid.

[0041] Calcium oxide and sodium metaaluminate are mixed uniformly in a weight ratio of 2.5:1 to obtain a sedimentation agent;

[0042] According to the ratio of sedimentation liquid to sedimentation agent = 100 mL: 7 g, the sedimentation agent was added to the sedimentation liquid and stirred at room temperature for 60 minutes. After the reaction was completed, a centrifuge was used for solid-liquid separation to obtain recycled water and filter residue.

[0043] Step 2: Slurry screening

[0044] The filter residue and the sedimentation residue were mixed and sieved using a sieve with an aperture of 6 mm. The large-size aggregate on the top of the sieve was washed with recycled water to obtain large-size aggregate and small-size mortar.

[0045] Step 3: Slurry sand regeneration

[0046] Adding recycled water to the small-particle mortar to obtain a mixed slurry with a solid content of 35%;

[0047] Weigh 200 g of nano-silica and 1 L of drinking water into a reaction flask, and ultrasonically disperse them for 30 min at room temperature. Then, add 80 g of water glass with a modulus of 2.0 into the reaction flask and continue ultrasonically dispersing for 40 min to obtain silica sol.

[0048] Weigh: 1 kg of mixed slurry and 30 g of cement are added to a blender and stirred at room temperature for 20 minutes. 800 g of silica sol is added to the blender and stirred for 40 minutes. The mixture is filtered and the filter cake is evenly spread on a drying yard and dried to a moisture content of 30% to obtain pre-treated slurry sand.

[0049] The pre-treated slurry sand is spread in a carbonization box. At room temperature, carbon dioxide is introduced into the carbonization box to replace the air inside the box until the internal pressure is stabilized at 0.35 MPa. The pressure is maintained for 20 hours, and then the pressure is reduced to normal pressure and discharged to obtain carbonized slurry sand.

[0050] Weigh: 100g of hydroxy silicone oil and 600mL of toluene were added to a nitrogen-protected reaction flask and stirred. The temperature of the reaction system was raised to 60°C and the mixture was heated to 400°C. 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of isocyanatepropyltriethoxysilane to be added, and add it to the reaction bottle, keep the temperature to react for 60 minutes, raise the temperature of the reaction bottle to 80°C, and distill under reduced pressure to remove low-boiling substances to obtain modified polysiloxane, which is then post-treated to obtain modified polysiloxane;

[0051] Weigh: 700 g of carbonized slurry sand, 150 g of modified polysiloxane, and 500 mL of recycled water, add them into a stirrer and stir and mix. Raise the stirrer temperature to 60°C, stir and mix for 40 minutes, lower the stirrer temperature to room temperature, spread it out in the drying yard, and dry it by itself to obtain regenerated slurry sand.

[0052] Step 4: Prepare concrete

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

[0054] The recycled mortar sand and fly ash are mixed in a weight ratio of 4:9 to obtain an admixture;

[0055] Mix machine-made 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 to obtain fine aggregate;

[0056] A polycarboxylate water reducer and a setting retarder, potassium tartrate, are mixed in a weight ratio of 3:2 to obtain an admixture;

[0057] Weigh out 850 parts of coarse aggregate, 850 parts of fine aggregate, 90 parts of admixture, 150 parts of cement and 6 parts of admixture by weight, add them into a mixer and stir, add 160 parts of recycled water while stirring, and after the addition is completed, mix for 10 minutes to obtain concrete.

[0058] Example 2

[0059] See also Figure 1 This embodiment provides a method for recycling and treating wastewater produced by a concrete mixing station, comprising the following steps:

[0060] Step 1: Wastewater sedimentation

[0061] The wastewater generated by the mixing station is added to the sedimentation tank and allowed to settle for 2 days. The supernatant liquid is extracted by a water pump. The slurry is then filtered through a filter cloth to obtain sediment residue and filtrate. The filtrate is mixed with the supernatant liquid to obtain sediment liquid.

[0062] Calcium oxide and sodium metaaluminate are mixed uniformly in a weight ratio of 2.5:1 to obtain a sedimentation agent;

[0063] According to the ratio of sedimentation liquid to sedimentation agent = 100 mL: 7.5 g, the sedimentation agent was added to the sedimentation liquid and stirred at room temperature for 70 minutes. After the reaction was completed, a centrifuge was used for solid-liquid separation to obtain recycled water and filter residue.

[0064] Step 2: Slurry screening

[0065] The filter residue and the sedimentation residue were mixed and sieved using a sieve with an aperture of 7 mm. The large-size aggregate on the top of the sieve was washed with recycled water to obtain large-size aggregate and small-size mortar.

[0066] Step 3: Slurry sand regeneration

[0067] Adding recycled water to the small-particle mortar to obtain a mixed slurry with a solid content of 40%;

[0068] Weigh 225 g of nano-silica and 1 L of drinking water into a reaction flask, and ultrasonically disperse them for 4 min at room temperature. Then, add 100 g of water glass with a modulus of 2.4 into the reaction flask, and continue ultrasonically dispersing for 50 min to obtain silica sol.

[0069] Weigh: 1 kg of mixed slurry and 40 g of cement are added to a blender and stirred at room temperature for 25 minutes. 850 g of silica sol is added to the blender and stirred for 45 minutes. The mixture is filtered and the filter cake is evenly spread on a drying yard and dried to a moisture content of 35% to obtain pre-treated slurry sand.

[0070] The pre-treated slurry sand was spread in a carbonization box. At room temperature, carbon dioxide was introduced into the carbonization box to replace the air inside the box until the internal pressure was stabilized at 0.40 MPa. The pressure was maintained for 22 hours, and then the pressure was reduced to normal pressure and discharged to obtain carbonized slurry sand.

[0071] Weigh: 100g of hydroxy silicone oil and 600mL of toluene were added to a nitrogen-protected reaction flask and stirred. The temperature of the reaction system was raised to 65°C and the mixture was heated to 400°C. 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of isocyanatepropyltriethoxysilane to be added, and add it to the reaction bottle, keep the temperature to react for 70 minutes, raise the temperature of the reaction bottle to 85°C, and distill under reduced pressure to remove low-boiling substances to obtain modified polysiloxane, which is then post-treated to obtain modified polysiloxane;

[0072] Weigh: 700 g of carbonized slurry sand, 165 g of modified polysiloxane, and 500 mL of recycled water, add them into a stirrer and stir and mix. Raise the stirrer temperature to 65°C, stir and mix for 50 minutes, lower the stirrer temperature to room temperature, spread it out in the drying yard, and dry it by itself to obtain regenerated slurry sand.

[0073] Step 4: Prepare concrete

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

[0075] The recycled mortar sand and fly ash are mixed in a weight ratio of 4:9 to obtain an admixture;

[0076] Mix machine-made 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 to obtain fine aggregate;

[0077] The polycarboxylate water reducer and the retarder calcium tartrate are mixed in a weight ratio of 3:2 to obtain an admixture;

[0078] Weigh out 900 parts of coarse aggregate, 900 parts of fine aggregate, 100 parts of admixture, 155 parts of cement and 6.5 parts of admixture in parts by weight and add them into a mixer and stir. Add 165 parts of recycled water while stirring. After the addition is completed, mix for 13 minutes to obtain concrete.

[0079] Example 3

[0080] See also Figure 1 This embodiment provides a method for recycling and treating wastewater produced by a concrete mixing station, comprising the following steps:

[0081] Step 1: Wastewater sedimentation

[0082] The wastewater generated by the mixing station is added to the sedimentation tank and allowed to settle for 3 days. The supernatant liquid is extracted by a water pump. The slurry is then filtered through a filter cloth to obtain sediment residue and filtrate. The filtrate is mixed with the supernatant liquid to obtain sediment liquid.

[0083] Calcium oxide and sodium metaaluminate are mixed uniformly in a weight ratio of 2.5:1 to obtain a sedimentation agent;

[0084] According to the ratio of sedimentation liquid to sedimentation agent = 100 mL: 8 g, the sedimentation agent was added to the sedimentation liquid and stirred at room temperature for 80 minutes. After the reaction was completed, a centrifuge was used for solid-liquid separation to obtain recycled water and filter residue.

[0085] Step 2: Slurry screening

[0086] The filter residue and the sedimentation residue were mixed and sieved using a sieve with an aperture of 8 mm. The large-size aggregate on the top of the sieve was washed with recycled water to obtain large-size aggregate and small-size mortar.

[0087] Step 3: Slurry sand regeneration

[0088] Adding recycled water to the small-particle mortar to obtain a mixed slurry with a solid content of 45%;

[0089] Weigh 250 g of nano-silica and 1 L of drinking water into a reaction flask, and ultrasonically disperse them for 50 min at room temperature. Then, add 120 g of water glass with a modulus of 2.8 into the reaction flask, and continue ultrasonically dispersing for 60 min to obtain silica sol.

[0090] Weigh: 1 kg of mixed slurry and 50 g of cement are added to a blender and stirred at room temperature for 30 min. 900 g of silica sol is added to the blender and stirred for 50 min. The mixture is filtered and the filter cake is evenly spread on a drying yard and dried to a moisture content of 40% to obtain pre-treated slurry sand.

[0091] The pre-treated slurry sand is spread in a carbonization box. At room temperature, carbon dioxide is introduced into the carbonization box to replace the air inside the box until the internal pressure is stabilized at 0.45 MPa. The pressure is maintained for 24 hours, and then the pressure is reduced to normal pressure and discharged to obtain carbonized slurry sand.

[0092] Weigh: 100g of hydroxy silicone oil and 600mL of toluene were added to a nitrogen-protected reaction flask and stirred. The temperature of the reaction system was raised to 70°C and the mixture was heated to 400°C. 羟基硅油-OH :n 异氰酸丙基三乙氧基硅烷 =1:0.95, calculate the amount of isocyanatepropyltriethoxysilane to be added, and add it to the reaction bottle, keep warm and react for 80 minutes, raise the temperature of the reaction bottle to 90°C, and distill under reduced pressure to remove low-boiling substances to obtain modified polysiloxane, which is then post-treated to obtain modified polysiloxane;

[0093] Weigh: 700 g of carbonized slurry sand, 180 g of modified polysiloxane, and 500 mL of recycled water, add them into a stirrer and stir and mix, increase the stirrer temperature to 70°C, stir and mix for 60 minutes, lower the stirrer temperature to room temperature, spread it out in the drying yard, and dry it by itself to obtain regenerated slurry sand.

[0094] Step 4: Prepare concrete

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

[0096] The recycled mortar sand and fly ash are mixed in a weight ratio of 4:9 to obtain an admixture;

[0097] Mix machine-made 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 to obtain fine aggregate;

[0098] The polycarboxylate water reducer and the retarder tartaric acid are mixed in a weight ratio of 3:2 to obtain an admixture;

[0099] Weigh out 950 parts of coarse aggregate, 950 parts of fine aggregate, 110 parts of admixture, 160 parts of cement and 7 parts of admixture by weight, add them into a mixer and stir, add 170 parts of recycled water while stirring, and after the addition is completed, 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 metaaluminate is 1.5:1.

[0102] Comparative Example 2

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

[0104] Comparative Example 3

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

[0106] Comparative Example 4

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

[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 measured using the standard GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures";

[0110] With reference 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 after curing for 7 days and 28 days was measured;

[0111] The non-steady-state chloride ion migration coefficients of the test samples prepared in Examples 1-3 and Comparative Examples 1-4 on the 28th day were measured with reference to the standard GB / T 50082-2024 "Standard for Test Methods for Long-term Performance and Durability of Concrete". Specific test data are shown in Table 1 below.

[0112] Table 1-Performance test data of the sample

[0113]

[0114] Data Analysis:

[0115] Comparative analysis of the data in Table 1 above shows that the slump value of the concrete material prepared by the present invention reaches 235 mm, the slump loss over time is reduced to 20 mm, the 7-day compressive strength of the concrete material reaches 34.2 MPa, the 28-day compressive strength reaches 46.7 MPa, and the non-steady-state chloride ion migration coefficient is reduced to 15×10 -14 m 2 / s, and all performance test data are better than those of the comparative example, indicating that the present invention regenerates and recovers solid impurities in wastewater from a concrete mixing station and combines them with fly ash to reinforce concrete, which not only effectively improves the plasticizing performance and pumpability of the concrete material, but also improves its compressive strength and resistance to chloride ion penetration. In addition, the wastewater without solid impurities is settled, effectively reducing its impact on concrete processing, so that it can be directly used in concrete production and processing without being affected by the amount of addition.

[0116] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for recycling and treating wastewater produced by a concrete mixing station, characterized in that: The following steps are involved: S1. Add the wastewater generated by the mixing station into the sedimentation tank, let it settle for 1-3 days, and separate the liquid to obtain the sediment residue and sediment liquid; Add a sedimentation agent to the sedimentation liquid, stir at room temperature for 60-80 minutes, and post-treat to obtain recycled water and filter residue; S2. Mix the filter residue and the sediment residue, and sieve them using a sieve with a pore size of 6-8 mm to obtain large-size aggregate and small-size mortar; S3, regenerating the small-particle mortar to prepare regenerated mortar sand; S4. Mix large-size aggregate and crushed stone to obtain coarse aggregate; mix recycled mortar sand and fly ash to obtain admixture; add coarse aggregate, fine aggregate, admixture, cement and admixture into a mixer and stir, while adding recycled water while stirring. After the addition is completed, mix for 10-15 minutes to obtain concrete.

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

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

3. The method for recycling and treating wastewater from a concrete mixing station according to claim 1, characterized in that: The preparation method of regenerated mortar sand is as follows: adding recycled water to small-particle mortar to obtain a mixed slurry; adding cement to the mixed slurry at room temperature, stirring and mixing for 20-30 minutes, then adding silica sol thereto, stirring and preserving for 40-50 minutes, and post-treating to obtain pre-treated mortar sand; the pre-treated mortar sand is carbonized with carbon dioxide to prepare carbonized mortar sand, and then the carbonized mortar sand is re-treated with modified polysiloxane to prepare regenerated mortar sand.

4. The method for recycling and treating wastewater from a concrete mixing station according to claim 3, 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-processing includes: after stirring, filtering, spreading the filter cake evenly on the drying yard, and drying to a moisture content of 30-40% to obtain pre-treated slurry sand.

5. The method for recycling and utilizing wastewater from a concrete mixing station according to claim 3, wherein: The preparation method of silica sol is as follows: nano-silica and drinking water are mixed, ultrasonically dispersed for 30-50 minutes, water glass is added to the reaction system, and ultrasonic dispersion is continued for 40-60 minutes to obtain silica sol, wherein the dosage ratio of the nano-silica, drinking water and water glass is 20-25g:100mL:8-12g, and the modulus of the water glass is 2.0-2.

8.

6. The method for recycling and treating wastewater from a concrete mixing station according to claim 3, characterized in that: The preparation method of carbonized slurry sand is as follows: the pre-treated slurry sand is spread in a carbonization box, and at room temperature, carbon dioxide is introduced into the carbonization box to replace the internal air, 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.

7. The method for recycling and utilizing wastewater from a concrete mixing station according to claim 3, wherein: Recycled slurry sand is obtained by the following steps: A1. Under inert gas protection, hydroxy silicone oil and toluene were mixed and stirred, the reaction system temperature was raised to 60-70°C, and isocyanatepropyltriethoxysilane was added to the reaction system. The reaction was kept warm for 60-80 minutes, and post-processed to obtain modified polysiloxane; A2. Stir and mix the carbonized mortar sand, modified polysiloxane and recycled water, increase the temperature of the reaction system to 60-70°C, stir and mix for 40-60 minutes, and post-treat to obtain regenerated mortar sand.

8. The method for recycling and treating wastewater from a concrete mixing station according to claim 7, characterized in that: In step A1, the amount ratio of the hydroxy silicone oil and toluene is 1g:6mL, the amount of the isocyanatepropyltriethoxysilane is 0.95 times the molar amount of hydroxyl groups in the hydroxy silicone oil, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is raised to 80-90°C, and low-boiling substances are removed under reduced pressure to obtain modified polysiloxane; in step A2, the amount ratio of the carbonized slurry, modified polysiloxane and recycled water is 7g:1.5-1.8g:5mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, and it is spread out in a drying yard to dry itself to obtain regenerated slurry.

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

9.

10. The method for recycling and treating wastewater from a concrete mixing station according to claim 1, characterized in that: The weight ratio of the coarse aggregate, fine aggregate, admixture, cement, admixture and recycled water is 850-950:850-950:90-110:150-160:6-7:160-170, the fine aggregate is composed of machine-made 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 admixture is composed of a water reducer and a retarder in a weight ratio of 3:2, the water reducer is a polycarboxylate water reducer, and the retarder is any one of tartaric acid, potassium tartrate and calcium tartrate.

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