1. A method for preparing an ultra-high performance concrete admixture by using concrete waste slurry is characterized by comprising the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, carrying out a neutralization reaction until the solution is neutral, and then filtering to obtain an impurity I and a solution A;

(2) adding the impurity I obtained after filtering in the step (1) into a second batch of nitric acid solution, soaking the nitric acid solution in the nitric acid solution, placing the nitric acid solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, slowly injecting sodium hydroxide solution into the closed container through the pipeline after reacting for a period of time, continuously stirring to adjust the pH value of the solution to 12-14, and filtering out particles to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 11-12 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, and performing ultrasonic dispersion while stirring to obtain an additive mixed solution D;

(5) and (5) spray drying the admixture mixed liquor D obtained in the step (4) to obtain the concrete powder admixture.

2. The method for preparing the ultra-high performance concrete admixture by using the concrete waste slurry as claimed in claim 1, wherein the surfactant in the step (1) is sodium ethylene diamine tetra methylene phosphonate, sodium di-sec-octyl maleate sulfonate (rapid penetrant T), allyl polyoxyethylene ether according to a mass ratio of 1-3: 1-2: 0.2-0.5, wherein the mixing amount is 0.5-1 wt% of the solid content of the concrete waste slurry.

3. The method for preparing an ultra-high performance concrete admixture using concrete waste slurry as claimed in claim 1, wherein the mixed solution of nitric acid and ferric chloride in step (1) is prepared by adding FeCl into the first nitric acid solution₃Powder is obtained by stirring until the powder is dissolved, and the mass concentration of the first batch of nitric acid solution is 30-60%; wherein, HNO in the mixed solution of nitric acid and ferric chloride₃The mass ratio of the waste concrete slurry to the waste concrete slurry is 0.4-0.9: 1, FeCl₃The mass ratio of the waste concrete slurry to the waste concrete slurry is 0.1-0.3: 1.

4. The method for preparing an ultra-high performance concrete admixture by using the concrete waste slurry as claimed in claim 3, wherein the mass concentration of the first nitric acid solution is 40%.

5. The method for preparing the ultra-high performance concrete admixture by using the waste concrete slurry as claimed in claim 1, wherein the reaction time in the step (2) is 6-8 h.

6. The method for preparing the ultra-high performance concrete admixture by using the waste concrete slurry as claimed in claim 1, wherein the mass concentration of the second batch of nitric acid solution in the step (2) is 30-60%;

the mass concentration of the hydrofluoric acid solution is 20% -35%, wherein the mass ratio of HF to the concrete waste slurry in the step (1) is 0.2-0.5: 1;

the mass concentration of the sodium hydroxide solution is 20-45%.

7. The method for preparing the ultra-high performance concrete admixture by using the waste concrete slurry as claimed in claim 6, wherein the mass concentration of the second batch of nitric acid solution in the step (2) is 40%;

the mass concentration of the hydrofluoric acid solution is 30%;

the mass concentration of the sodium hydroxide solution is 30%.

8. The method for preparing an ultra-high performance concrete admixture using concrete waste slurry as claimed in claim 1, wherein in the methacrylic acid copolymer of step (3), the number of the polyoxyethylene unit of the polymer side chain is not less than 60, and the amount of the substance is HNO in the mixed liquid of nitric acid and ferric chloride of step (1)₃The amount of the substance is 2-2.5 times, and the volume of the solution C is 1.5-2.5 times of the volume of the solution A.

9. The method for preparing the ultra-high performance concrete admixture by using the waste concrete slurry as claimed in claim 1, wherein the ultrasonic dispersion time in the step (4) is 48-72 h.

Background

A large amount of waste cement slurry can be generated in the production process of commercial concrete, the commercial concrete mainly comprises a large amount of waste muddy water generated after a mixer and a transport vehicle are washed in production, and the mud contains cement, aggregate, additives and the like, so that the commercial concrete is a concrete waste material. At present, due to the defects of the difference and the management of the technology and the weak environmental awareness of production enterprises, the waste cement slurry is discharged and disposed at will, a large amount of land is occupied by stacking and burying, and the waste slurry is a strong alkaline substance and is extremely large in damage to the soil, so that the environment is damaged, and the waste of a large amount of water resources is also caused. Meanwhile, the waste disposal cost is required to be borne by enterprises when the enterprises treat the waste cement paste, so that the cost of concrete production is greatly increased. At present, the utilization of waste slurry mainly uses precipitated waste water for preparing concrete, and the waste slurry is directly used for producing the concrete, so that the cost is saved, the waste utilization is realized to a certain extent, the discharge of the waste slurry is reduced, and certain economic, social and environmental benefits are achieved.

However, for concrete, the concrete is mainly applied to concrete with medium and low strength grades, namely, concrete waste slurry is used as an admixture to be mixed into the concrete, at present, the method is applied to the concrete production to a certain extent, and on the premise that the waste slurry is well treated, the performance of the concrete with medium and low strength is not influenced, even the mechanical property of the concrete can be improved to a certain extent, but the expansion degree and the slump of the concrete mixture are reduced. The method is mainly used for solving the problems that the waste concrete slurry has a certain retardation effect, the early strength of the concrete is reduced after the waste concrete slurry is doped into the mineral admixture, and the overall strength of the concrete is also reduced.

Disclosure of Invention

The invention provides a method for preparing an ultra-high performance concrete (UHPC) admixture by utilizing waste concrete slurry, aiming at the problems existing in the prior art that the treated waste concrete slurry is used for the ultra-high performance concrete (UHPC), the waste concrete slurry is improved to form the admixture capable of improving the performance of the ultra-high performance concrete (UHPC), the early strength of the concrete is improved, and the final strength of the concrete is not influenced; and the resource utilization and high-end utilization of the waste slurry can be realized, and the additional value of the recycling of the concrete waste cement slurry is improved.

The invention provides a method for preparing an ultra-high performance concrete admixture by using concrete waste slurry, which comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, carrying out a neutralization reaction until the solution is neutral, and then filtering to obtain an impurity I and a solution A;

(2) adding the impurity I obtained after filtering in the step (1) into a second batch of nitric acid solution, soaking the nitric acid solution in the nitric acid solution, placing the nitric acid solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, slowly injecting sodium hydroxide solution into the closed container through the pipeline after reacting for a period of time, continuously stirring to adjust the pH value of the solution to 12-14, and filtering out particles to obtain a solution B;

the reaction time in the step (2) is 6-8 h;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 11-12 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, and performing ultrasonic dispersion while stirring to obtain an additive mixed solution D;

the ultrasonic dispersion time in the step (4) is 48-72 h;

(5) and (5) spray drying the admixture mixed liquor D obtained in the step (4) to obtain the concrete powder admixture.

The surfactant in the step (1) is ethylenediamine tetramethylene phosphonic acid sodium salt, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether in a mass ratio of 1-3: 1-2: 0.2-0.5, wherein the mixing amount is 0.5-1 wt% of the solid content of the concrete waste slurry;

the mixed solution of nitric acid and ferric chloride in the step (1) is obtained by adding FeCl into the nitric acid solution of the first batch₃Powder is obtained by stirring until the powder is dissolved, and the mass concentration of the first batch of nitric acid solution is 30-60%; wherein, HNO in the mixed solution of nitric acid and ferric chloride₃The mass ratio of the waste concrete slurry to the waste concrete slurry is 0.4-0.9: 1, FeCl₃The mass ratio of the waste concrete slurry to the waste concrete slurry is 0.1-0.3: 1. Preferably, the mass concentration of the nitric acid solution of the first batch is 40%.

The mass concentration of the second batch of nitric acid solution in the step (2) is 30-60%, and the preferred mass concentration is 40%.

The mass concentration of the hydrofluoric acid solution in the step (2) is 20% -35%, wherein the mass ratio of HF to the concrete waste slurry in the step (1) is 0.2-0.5: 1; preferably, the hydrofluoric acid solution has a mass concentration of 30%.

In the step (2), the mass concentration of the sodium hydroxide solution is 20-45%. Preferably, the solution has a mass concentration of 30%.

In the methacrylic acid copolymer in the step (3), the number of polymer side chain polyoxyethylene units is not less than 60, and the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃The amount of the substance is 2-2.5 times, and the volume of the solution C is 1.5-2.5 times of the volume of the solution A.

According to the invention, the surfactant is added into the concrete waste slurry and ultrasonic dispersion is carried out, so that waste slurry particles are uniformly dispersed, further hydration reaction is prevented, and excessive C-S-H gel is avoided; the addition of ferric chloride solution in nitric acid can promote the hydrolysis of the generated C-S-H gel particles, accelerate and increase the dissolution of substances as much as possible. Hydrofluoric acid is injected into the sealed air to dissolve silicon dioxide and residual C-S-H coagulation and other substances, and sodium fluosilicate and sodium silicate can be generated in the solution by further adding calcium hydroxide. The product of the step (1) and the step (2) reacts in the alkaline methacrylic acid copolymer solution of the step (3), and the generated mixed solution is sprayed and dried to form the powder admixture with the early strength function.

Has the advantages that:

after the concrete waste cement paste is modified by the method, the problem of concrete performance reduction caused by the concrete waste cement paste as a high-performance concrete admixture is solved, the improvement of the early strength of the ultrahigh-performance concrete is ensured, and the resource utilization and the fine high-end utilization of the concrete waste cement paste are realized.

Detailed Description

In order to better understand the present invention, the following embodiments are further described, but it should not be understood that the present invention is only applicable to the following examples, and those skilled in the art can make some insubstantial changes and modifications to the present invention based on the above disclosure, and still fall within the scope of the present invention.

Example 1

A method for preparing an ultra-high performance concrete admixture by utilizing waste concrete slurry comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, and carrying out a neutralization reaction until the solution is neutral; filtering impurities to form a solution A;

(2) adding the filtered impurities into a second batch of nitric acid solution, immersing the impurities, placing the impurities in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, and reacting for 6 hours; slowly injecting a sodium hydroxide solution into the closed container through a pipeline, continuously stirring, adjusting the pH value of the solution to 12, and filtering out particulate matters to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 11 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, stirring and ultrasonically dispersing for 48 hours to obtain a mixed solution D;

(5) and (4) spray drying the additive mixed solution D to obtain the concrete powder additive.

The solid content of the concrete waste slurry is 1 part; the mass parts of the following substances are based on the solid content of the concrete waste slurry;

the surfactant is sodium ethylene diamine tetra methylene phosphonate, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether in a mass ratio of 1: 1:0.5, wherein the mixing amount is 0.5 percent of the solid content of the waste slurry;

the mixed solution of nitric acid and ferric chloride is prepared by adding FeCl into a nitric acid solution with the mass concentration of 30%₃And stirring the powder until the powder is dissolved. Wherein, HNO₃0.4 part by mass of FeCl₃The mass portion is 0.1 portion.

The mass concentration of the hydrofluoric acid solution is 20%, wherein the mass part of HF is 0.2.

The mass concentration of the sodium hydroxide solution is 20%.

In the methacrylic acid copolymer, the number of polymer side chain polyoxyethylene units is 60; the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃2 times the amount of substance.

Example 2

A method for preparing an ultra-high performance concrete admixture by utilizing waste concrete slurry comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, and carrying out a neutralization reaction until the solution is neutral; filtering impurities to form a solution A;

(2) and adding the filtered impurities into a second batch of nitric acid solution, immersing the impurities, placing the solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, and reacting for 8 hours. Slowly injecting a sodium hydroxide solution into the closed container through a pipeline, continuously stirring, adjusting the pH value of the solution to be 14, and filtering out particulate matters to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 12 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, and carrying out ultrasonic dispersion while stirring for 72 hours to obtain a mixed solution D;

(5) and (4) spray drying the additive mixed solution D to obtain the concrete powder additive.

The solid content of the concrete waste slurry is 1 part; the mass parts of the following substances are based on the solid content of the concrete waste slurry;

the surfactant is sodium ethylene diamine tetra methylene phosphonate, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether according to the mass ratio of 3: 2: 0.2, wherein the mixing amount is 1 percent of the solid content of the waste slurry;

the mixed solution of nitric acid and ferric chloride is prepared by adding FeCl into a nitric acid solution with the mass concentration of 60%₃And stirring the powder until the powder is dissolved. Wherein, HNO₃0.9 part by mass of FeCl₃The mass portion is 0.3 portion.

The mass concentration of the hydrofluoric acid solution is 35%, wherein the mass part of HF is 0.5.

The mass concentration of the sodium hydroxide solution is 45%.

In the methacrylic acid copolymer, the number of polymer side chain polyoxyethylene units is 94; the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃2 times the amount of substance.

Example 3

A method for preparing an ultra-high performance concrete admixture by utilizing waste concrete slurry comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, and carrying out a neutralization reaction until the solution is neutral; filtering impurities to form a solution A;

(2) and adding the filtered impurities into a second batch of nitric acid solution, immersing the impurities, placing the solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, and reacting for 7 hours. Slowly injecting a sodium hydroxide solution into the closed container through a pipeline, continuously stirring, adjusting the pH value of the solution to 13, and filtering out particulate matters to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 12 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, and carrying out ultrasonic dispersion while stirring for 60 hours to obtain a mixed solution D;

(5) and (4) spray drying the additive mixed solution D to obtain the concrete powder additive.

The solid content of the concrete waste slurry is 1 part; the mass parts of the following substances are based on the solid content of the concrete waste slurry;

the surfactant is sodium ethylene diamine tetra methylene phosphonate, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether according to a mass ratio of 2: 1.5: 0.3, wherein the mixing amount of the mixed solution is 0.8 percent of the solid content of the waste slurry;

the mixed solution of nitric acid and ferric chloride is prepared by adding FeCl into a nitric acid solution with the mass concentration of 40%₃And stirring the powder until the powder is dissolved. Wherein, HNO₃0.7 part by mass of FeCl₃0.2 part by mass;

the mass concentration of the hydrofluoric acid solution is 30%, wherein the mass part of HF is 0.4;

the mass concentration of the sodium hydroxide solution is 30 percent;

in the methacrylic acid copolymer, the number of polyoxyethylene units in the side chain of the polymer94 pieces of; the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃2.2 times the amount of material.

Example 4

A method for preparing an ultra-high performance concrete admixture by utilizing waste concrete slurry comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, and carrying out a neutralization reaction until the solution is neutral; filtering impurities to form a solution A;

(2) and adding the filtered impurities into a second batch of nitric acid solution, immersing the impurities, placing the solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, and reacting for 6 hours. Slowly injecting a sodium hydroxide solution into the closed container through a pipeline, continuously stirring, adjusting the pH value of the solution to be 14, and filtering out particulate matters to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 11 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, stirring and ultrasonically dispersing for 54h to obtain a mixed solution D;

(5) and (4) spray drying the additive mixed solution D to obtain the concrete powder additive.

The solid content of the concrete waste slurry is 1 part; the mass parts of the following substances are based on the solid content of the concrete waste slurry;

the surfactant is sodium ethylene diamine tetra methylene phosphonate, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether according to a mass ratio of 1.5: 2: 0.5, wherein the mixing amount of the mixed solution is 0.9 percent of the solid content of the waste slurry;

the mixed solution of nitric acid and ferric chloride is prepared by adding FeCl into 35% nitric acid solution₃And stirring the powder until the powder is dissolved. Wherein, HNO₃0.75 portion of FeCl₃0.25 part by mass;

the mass concentration of the hydrofluoric acid solution is 25%, wherein the mass part of HF is 0.35;

the mass concentration of the sodium hydroxide solution is 40%;

in the methacrylic acid copolymer, the number of polymer side chain polyoxyethylene units is 107; the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃2.4 times the amount of substance.

Example 5

A method for preparing an ultra-high performance concrete admixture by utilizing waste concrete slurry comprises the following steps:

(1) adding a surfactant into the waste concrete slurry, stirring and ultrasonically dispersing to form a suspension dispersion liquid, then dropwise adding a mixed solution of nitric acid and ferric chloride, and carrying out a neutralization reaction until the solution is neutral; filtering impurities to form a solution A;

(2) and adding the filtered impurities into a second batch of nitric acid solution, immersing the impurities, placing the solution in a closed container provided with a single pipeline, injecting hydrofluoric acid solution into the container through the pipeline, continuously and slowly stirring, and reacting for 7 hours. Slowly injecting a sodium hydroxide solution into the closed container through a pipeline, continuously stirring, adjusting the pH value of the solution to 12.7, and filtering out particulate matters to obtain a solution B;

(3) dissolving a methacrylic acid copolymer in water, and dropwise adding sodium hydroxide to adjust the pH of the solution to 11.8 to obtain a solution C;

(4) slowly pumping the solution A obtained in the step (1) and the solution B obtained in the step (2) into the solution C obtained in the step (3) at the same time, and carrying out ultrasonic dispersion while stirring for 70 hours to obtain a mixed solution D;

(5) and (4) spray drying the additive mixed solution D to obtain the concrete powder additive.

The solid content of the concrete waste slurry is 1 part; the mass parts of the following substances are based on the solid content of the concrete waste slurry;

the surfactant is sodium ethylene diamine tetra methylene phosphonate, di-sec-octyl maleate sodium sulfonate (rapid penetrant T) and allyl polyoxyethylene ether according to the mass ratio of 3: 1: 0.2, wherein the mixing amount of the mixed solution is 0.6 percent of the solid content of the waste slurry;

the mixed solution of nitric acid and ferric chloride is prepared by adding FeCl into 35% nitric acid solution₃And stirring the powder until the powder is dissolved. Wherein, HNO₃0.5 part by mass of FeCl₃0.3 part by mass;

the mass concentration of the hydrofluoric acid solution is 28%, wherein the mass part of HF is 0.42;

the mass concentration of the sodium hydroxide solution is 30 percent;

in the methacrylic acid copolymer, the number of polymer side chain polyoxyethylene units is 102; the amount of the substances is HNO in the mixed solution of nitric acid and ferric chloride in the step (1)₃2.5 times the amount of substance.

Application embodiment mode

Referring to a test method in GB/T50080, preparing UHPC (ultra high performance concrete) with the formula shown in Table 1; in Table 1, the river sand has the particle size of 0.075-4.75 mm, the cement is P.O42.5, the steel fiber has the length of 10-15 mm and the diameter of 0.12-0.2 mm, and in comparative example 2, the additive is PCE (polycarboxylic acid high-performance water reducing agent, manufacturer: China new materials Co., Ltd.);

TABLE 1UHPC concrete mix proportion

Serial number	Water to glue ratio	River sand	Cement	Fly ash micro-bead	Silica fume	Steel fiber	Additive agent
								Comparative example 1	0.18	1370	750	200	200	200	0
Comparative example 2	0.18	1370	750	200	200	200	25
								Example 1	0.18	1370	750	200	200	200	25
Example 2	0.18	1370	750	200	200	200	25
								Example 3	0.18	1370	750	200	200	200	25
Example 4	0.18	1370	750	200	200	200	25
								Example 5	0.18	1370	750	200	200	200	25

The slump of the mix was tested according to test method in GB50080 and the 1d, 3d, 7d and 28 day strength of the concrete was tested according to test method in GB50081 as shown in table 2:

TABLE 2 concrete Performance parameters

In table 2, when the mix proportion test was performed as in table 1, the concrete mixture had poor fluidity without adding the water reducing agent, and it was difficult to measure the extension degree and slump, and it was difficult to mold due to dry and hard, and the molded test piece had poor strength and had no reference. When the PCE water reducing agent and the additive are added into concrete, the concrete can show better strength. As can be seen from table 2, the additive of the present invention can exhibit substantially the same extension, slump, and apparent density as PCE, with no significant statistical variation. However, compared with PCE, the invention can better improve the early strength of the ultra-high performance concrete (UHPC), and the 28d strength is not only not inverted but also higher than that of the concrete added with PCE water reducing agent.