Preparation method of a commodity concrete waste slurry-based thickening type slurry admixture

Abstract

The application discloses a preparation method of a commercial concrete waste slurry-based thickening type slurry admixture. The commercial concrete waste slurry-based thickening type slurry admixture is prepared by taking concrete waste slurry and two kinds of solid wastes as precursors. When 20-30 kg / m 3 (dry mass) of the commercial concrete waste slurry-based thickening type slurry admixture prepared by the application is added into commercial concrete with fly ash and slag, the concrete has good working performance, does not bleed water and does not separate, can promote the development of early strength of the concrete, and can also improve the 28d strength of the concrete. In addition, the commercial concrete waste slurry-based thickening type slurry admixture prepared by the application can replace cement with the same weight, and the amount of fly ash or slag can be reduced by 10-20 kg / m 3 , so that the preparation cost of the concrete is effectively reduced, and the added value and resource utilization rate of the commercial concrete waste slurry are improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a method for preparing a thickening paste-like admixture based on waste slurry from commercial concrete. Background Technology

[0002] With the rapid development of my country's economy and the continuous acceleration of urbanization, the demand for concrete is constantly increasing, and the production volume of ready-mixed concrete plants is also constantly increasing. During the concrete production process, a large amount of waste slurry is generated from washing, mixing, transporting, and cleaning pumping equipment and sites, becoming a significant type of waste. This waste slurry is highly alkaline with a pH value greater than 13 and contains hydraulic cementitious materials such as cement, slag powder, and fly ash. The ready-mixed concrete industry has long lacked a scientific management system and supporting treatment and disposal technologies. Large amounts of waste slurry are directly discharged into sewers, polluting clean water sources and making them alkaline. The fine particles in the waste slurry accumulate and harden, clogging sewers and generating new waste residue. Simultaneously, the accumulation of large amounts of solid waste during production not only occupies space but also generates wastewater and dust due to rainwater and wind, causing secondary pollution. Some waste residue is even dumped indiscriminately, and its high alkalinity leads to soil salinization, causing significant pollution to soil and groundwater.

[0003] With increasing environmental awareness and growing pressure to protect the environment, promoting cleaner production and implementing green product design and full-process control in the production of ready-mixed concrete is imperative. In China, some building materials research institutions and concrete mixing plant technicians have studied waste slurry recycling methods, using sand and gravel separators to separate the waste slurry. The resulting sand, gravel, and slurry are then recycled according to their categories. This method solves the problem of waste recycling at mixing plants to some extent. However, in actual production, the large fluctuations in waste slurry concentration and unstable quality can lead to quality fluctuations and potential quality risks when used in concrete.

[0004] Therefore, realizing the resource utilization of waste slurry from concrete mixing plants has become a key research and solution issue for many concrete production enterprises and technicians. Summary of the Invention

[0005] In view of this, the present invention aims to provide a thickening slurry admixture based on commercial concrete waste slurry, which is prepared by using concrete waste slurry and two kinds of solid waste as precursors to make a thickening slurry admixture for commercial concrete, effectively solving the problem of the difficulty in resource utilization of waste slurry from existing concrete mixing plants.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing a thickening paste-like admixture based on commercial concrete waste slurry includes the following steps:

[0008] 1) Mix the waste slurry of filter press concrete, slag, and phosphogypsum in a dry mass ratio of 10:1:0.05 to 15:1:0.1, and then ball mill for a period of time to obtain a mixed slurry;

[0009] 2) Add polycarboxylate superplasticizer to the mixed slurry with a solid content of 30-40%, stir and homogenize for a period of time, then ball mill and perform ultrafine treatment to obtain a commercial concrete waste slurry-based thickening slurry admixture with a median particle size of 4-8 μm. The amount of polycarboxylate superplasticizer added is 0.1-0.3% of the dry mass of the mixed slurry.

[0010] Optionally, the moisture content of the filter press-filtered concrete waste slurry in step 1) is ≤50%, the pH is 11.0-13.0, and the density is 1.002 kg / m³. 3 -1.102kg / m 3 .

[0011] Optionally, the ball milling speed in step 1) is 20-28 r / min, and the ball milling time is 20-30 min.

[0012] Optionally, the slag mentioned in step 1) is S95 grade mineral powder with an Al2O3 content ≥12%.

[0013] Optionally, the calcium sulfate dihydrate content in the phosphogypsum described in step 1) is ≥65%.

[0014] Optionally, the polycarboxylate superplasticizer in step 2) is a slump-retaining polycarboxylate superplasticizer, and the solid content of the polycarboxylate superplasticizer is 30-40%.

[0015] Optionally, the homogenization time for stirring and homogenizing in step 2) is 24-28 hours.

[0016] Optionally, the solid content of the commercial concrete waste slurry-based thickening admixture in step 2) is 30-40%.

[0017] Compared with existing technologies, the preparation method of the commercial concrete waste slurry-based thickening admixture of the present invention has the following advantages:

[0018] 1. This invention uses concrete waste slurry and two kinds of solid waste as precursors to prepare a thickening slurry admixture for commercial concrete, which can not only improve the utilization rate of solid waste resources, but also reduce the preparation cost and increase the added value of raw materials.

[0019] 2. The slag hydration rate of the thickening slurry admixture prepared by this invention can reach over 50%. This is because the filter-pressed commercial concrete waste slurry has a strong alkalinity with a pH value greater than 13, which increases the solubility of H4SiO4 on the surface of the slag particles. This dissolves various forms of silicate ions and Ca(OH)2 in the solution to form hydrated calcium silicate, effectively improving the slag hydration rate based on the precipitation-dissolution equilibrium principle. Simultaneously, under the activation of a small amount of gypsum, a small amount of ettringite is generated. Its small size acts as a nucleation inducer in the early stages of cement hydration, promoting the formation of nano-ettringite, thus providing not only a good thickening effect but also a strengthening effect.

[0020] 3. The waste slurry-based thickening admixture for commercial concrete prepared according to this invention is added at a rate of 20-30 kg / m³ to commercial concrete with both fly ash and slag admixtures. 3 (Dry weight) It does not bleed or segregate, and can replace the same weight of cement while reducing the amount of fly ash or mineral powder used by 10-20 kg / m³. 3 To maintain the same mechanical properties. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions and effects of the present invention, several embodiments will be provided below. Obviously, the following description is only an embodiment and does not limit the scope of protection of the present invention.

[0022] Example 1

[0023] A method for preparing a thickening paste-like admixture based on commercial concrete waste slurry includes the following steps:

[0024] 1) 500g, 50g, and 2.5g of dry weight of filter press concrete waste slurry, slag, and phosphogypsum were placed in a tube ball mill and mixed and milled at 28 r / min for 20 min to obtain a mixed slurry. The filter press concrete waste slurry had a water content of 45.2%, a pH of 11.56, and a density of 1.058 kg / m³. 3 The slag is S95 grade mineral powder with an Al2O3 content of 13.6%; the phosphogypsum contains 67.8% calcium sulfate dihydrate.

[0025] 2) Add 0.5525g of slump-retaining polycarboxylate superplasticizer with a solid content of 40% to a mixed slurry with a solid content of 35%. After stirring and homogenizing for 24 hours at room temperature using a magnetic stirrer, the mixture is ball-milled using a tubular ball mill for ultrafine treatment to obtain a commercial concrete waste slurry-based thickening slurry admixture with a median particle size of 6.5μm, a solid content of 38%, a pH value of 12.9, a chloride content of 56mg / L, and a sulfate content of 32mg / L. The dispersion effect of the slump-retaining polycarboxylate superplasticizer is shown in Table 1.

[0026] Table 1. Dispersion effect of slump-retaining polycarboxylate superplasticizer

[0027]

[0028] The commercial concrete waste slurry-based thickening paste admixture of Example 1 of this invention was used in concrete. After multiple adaptations, mix proportion experiments were conducted using appropriate sand ratios. The C30, C40, and C50 mix proportions are shown in Table 2. 0-1 is the blank control group for Application Examples 1 and 2, 0-2 is the blank control group for Application Examples 3 and 4, and 0-3 is the blank control group for Application Examples 5 and 6. The amount of commercial concrete waste slurry-based thickening paste admixture in each mix proportion is based on dry weight. The fineness modulus of the manufactured sand is 2.6, the particle size of the crushed stone is 5-10 mm, and the water-reducing agent is the slump-retaining polycarboxylate water-reducing agent from step 2).

[0029] Table 2 Mix Proportion Design

[0030]

[0031] The slump and spread of concrete containing the waste slurry-based thickening slurry admixture of this invention were tested according to Example 1-Application Example 6 of GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The water retention and cohesiveness of the concrete were observed during the test, and the workability of the concrete was evaluated based on the final results. Table 3 shows the effect of different dosages of the waste slurry-based thickening slurry admixture of this invention on the slump of the concrete, and Table 4 shows the effect of different dosages on the spread of the concrete.

[0032] As shown in Tables 3 and 4, with the increase of the dosage of the waste slurry-based admixture in the commercial concrete of the present invention, both the initial slump and spread increase with the increase of the dosage, which improves the workability of the concrete to a certain extent. The same trend can be found in Application Examples 3-6. In the experiment, the mixtures showed good workability, with no segregation or bleeding. Furthermore, the slump and spread of the mixtures in Application Examples 1-6 all met the construction requirements.

[0033] Table 3 Slump Results

[0034] Application examples Initial slump / mm 30min slump / mm 60min slump / mm 0-1 210 205 185 Application Example 1 220 210 190 Application Example 2 225 220 195 0-2 220 215 210 Application Example 3 230 220 215 Application Example 4 235 225 220 0-3 225 220 215 Application Example 5 230 225 220 Application Example 6 240 230 225

[0035] Table 4 Expansion Results

[0036] Application examples Initial expansion / mm 30min expansion / mm 60min expansion / mm 0-1 500 490 485 Application Example 1 525 495 490 Application Example 2 530 500 495 0-2 530 525 515 Application Example 3 545 535 525 Application Example 4 585 550 545 0-3 540 535 530 Application Example 5 560 545 540 Application Example 6 590 565 550

[0037] The mechanical properties of concrete specimens containing the waste slurry-based thickening admixture of this invention were tested according to Example 1-Application Example 6 of the standard GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are shown in Table 5.

[0038] Table 5 Mechanical Properties

[0039]

[0040] As shown in Table 5, compared with the control group, adding 20-30 kg of the dry weight of the commercial concrete waste slurry-based thickening admixture of this invention to the concrete not only promotes the development of early strength but also improves the 28-day strength of the concrete. This is because the concrete waste slurry contains active ingredients such as cement, fly ash, and mineral powder. These active ingredients are relatively fine and have a certain filling effect on the pores of the concrete, increasing its density. Therefore, at the same water-cement ratio, the strength increases to a certain extent with the increase of the admixture dosage.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a thickening slurry-like admixture based on commercial concrete waste slurry, characterized in that, Includes the following steps: 1) Mix the waste slurry of filter press concrete, slag, and phosphogypsum in a dry mass ratio of 10:1:0.05 to 15:1:0.1, and then ball mill for a period of time to obtain a mixed slurry; 2) Add polycarboxylate superplasticizer to the mixed slurry with a solid content of 30-40%, stir and homogenize for a period of time, then ball mill and perform ultrafine treatment to obtain a commercial concrete waste slurry-based thickening slurry admixture with a median particle size of 4-8 μm. The amount of polycarboxylate superplasticizer added is 0.1-0.3% of the dry mass of the mixed slurry.

2. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The filter press waste concrete slurry mentioned in step 1) has a moisture content of ≤50%, a pH of 11.0-13.0, and a density of 1.002 kg / m³. 3 -1.102kg / m 3 .

3. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The ball milling speed in step 1) is 20-28 r / min, and the ball milling time is 20 min.

4. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The slag mentioned in step 1) is S95 grade mineral powder with an Al2O3 content ≥12%.

5. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The calcium sulfate dihydrate content in the phosphogypsum described in step 1) is ≥65%.

6. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The polycarboxylate superplasticizer mentioned in step 2) is a slump-retaining polycarboxylate superplasticizer, and the solid content of the polycarboxylate superplasticizer is 40%.

7. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The homogenization time for stirring and homogenizing in step 2) is 24-28 hours.

8. The method for preparing a thickening slurry-like admixture based on waste concrete slurry according to claim 1, characterized in that, The solid content of the commercial concrete waste slurry-based thickening admixture mentioned in step 2) is 30-40%.

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