WO2024040952A1

WO2024040952A1 - Sludge and waste concrete-based green concrete preparation method

Info

Publication number: WO2024040952A1
Application number: PCT/CN2023/082691
Authority: WO
Inventors: 王伟; 乐绍林; 朱世峰; 段庆松; 陈伟; 路洋; 马小云; 高望; 桑毅彩
Original assignee: 中交特种工程有限公司
Priority date: 2022-08-23
Filing date: 2023-03-21
Publication date: 2024-02-29
Also published as: CN115594446A

Abstract

Disclosed in the present invention is a sludge and waste concrete-based green concrete preparation method, comprising the following steps: step S1, sludge pretreatment; step S2, waste concrete crushing; step S3, recycled fine aggregate treatment; step S4, recycled coarse aggregate treatment; and step S5, green concrete preparation. According to the present invention, a large amount of construction waste such as waste concrete and sludge in rivers, lakes and seas is used as raw materials, so that a large amount of construction waste is consumed, achieving resource reutilization of construction waste, and reducing high energy consumption caused by conventional methods, and therefore, the present invention relates to a green recycling technology; the concrete in the present invention can be applied to structures such as rural cement concrete pavements, and thus has broad application prospects and considerable benefits.

Description

A method for preparing green concrete based on silt and waste concrete

Technical field

The present invention relates to the field of preparation methods of green concrete based on silt and waste concrete. More specifically, the present invention relates to a method for preparing green concrete based on silt and waste concrete.

Background technique

As the sludge has a high moisture content and complex composition, it is prone to secondary pollution. Improper disposal will have extremely adverse effects on the environment. Therefore, the treatment and disposal of dredged river bottom sludge has become a common concern. The existing silt utilization technologies mainly include solidified soil, sintered ceramsite, unfired ceramsite, silt bricks, silt cement, etc. Among them, the technology of unfired ceramsite has the broadest prospects. The current recycling path for waste concrete is relatively clear and mature. After the demolition waste concrete is initially crushed on site, it is transported to the recycling and crushing material recycling plant. Through fine crushing, coarse aggregate (gravel) and powder (sand and cement slurry are crushed) material), in which coarse aggregate is mixed into fresh concrete to prepare concrete, and powder is mixed into base materials to build the base layer.

Chinese Patent Application Publication No. CN 110156409 A discloses a concrete containing silt and its preparation method. Cement, silt, fly ash, basalt gravel, river sand, polypropylene fiber, and nano-reinforcement are added to a concrete mixer and mixed. Evenly, then add the mixed solution and stir evenly to obtain it. Its strength is about 30-35MPa. Chinese Patent Authorization Announcement No. CN 103755267 B announces a silt concrete and its preparation method, including cement, water, gravel, fly ash, mineral powder, sand and admixtures, and uses silt to replace part of the sand as fine aggregate. Finally, The strength is about 35MPa. Chinese Patent Application Publication No. CN 108558337 A discloses a method for preparing organic active concrete by modifying sludge. The sludge is deodorized and reacted with an organic synthetic curing agent, and then the modified sludge, Portland cement, and pulverized coal are combined. Mix ash, etc. to obtain organic active concrete. The concrete obtained by the above three patented technologies has lower strength and less silt participation. Compared with ordinary C30 concrete, the cost is higher, the added value is lower, and the market competitiveness is poor.

Chinese Patent Application Publication No. 114436601A discloses a recycled aggregate self-compacting concrete and its preparation method. Waste concrete is crushed, sorted and screened to make aggregate particles; water glass, PVA, nano-silica , phosphoric acid and water are mixed evenly to make a composite liquid, and the aggregate particles are placed in the composite liquid and soaked; the aggregate particles soaked in the composite liquid are placed in a closed container, evacuated, and carbon dioxide gas is introduced, and the pressure is raised to 0.1-0.4MPa, maintain pressure for 20-24h to make reinforced aggregate particles; soak the reinforced aggregate particles in water-based silicone resin emulsion, dry, and finally stir to form self-compacting concrete, which has a dense structure, high mechanical strength, and resistance to The advantage of strong freezing resistance. Chinese Patent Authorization Announcement No. CN 113024199 B announces a recycled concrete prepared from waste construction concrete and its preparation method. The preparation method is: 1) crush, clean and screen the waste construction concrete to obtain recycled aggregate; 2 ) Mix the recycled aggregate with magnesium sulfate, lithium carbonate, sodium sulfate, and potassium dihydrogen phosphate to obtain a mixture; 3) Mix the mixture with cementitious materials, coarse aggregate, fine aggregate, additives, synergists and water Mixing is carried out to obtain recycled concrete prepared from waste construction concrete, which increases the anti-permeability performance of the concrete and has good crack resistance at the same time. The above 2 patents There are many materials used and the production process is cumbersome, and it still does not get rid of the convention of treating coarse aggregate and fine aggregate differently. After screening, the coarse aggregate is divided into three types: 20-30cm, 10-20cm, and 5-10cm, which are added separately. Different grades of concrete are generally not added to one type of concrete at the same time; fine aggregate cannot be added to concrete and is generally added to the base layer (a downgraded use). This will result in a large amount of powder that can only be used for low-grade base layers, mortars, etc. building.

In short, the existing technologies are either for river and lake bottom mud or for waste concrete. There are few cases of combined use of the two. They have not maximized the green application of construction waste such as silt and waste concrete in construction projects and highway projects.

Contents of the invention

In order to achieve these objects and other advantages according to the present invention, a preferred embodiment of the present invention provides a preparation method of green concrete based on silt and waste concrete, comprising the following steps:

Step S1, sludge pretreatment

Stir the sludge and quicklime, let it stand, dry and grind, to obtain the treated sludge, which is divided into two parts, namely Part A and Part B;

Step S2: Crushing waste concrete

Remove debris from waste concrete and crush and screen it to obtain recycled coarse aggregate and recycled fine aggregate;

Step S3, recycled fine aggregate processing

Thoroughly mix the regenerated fine aggregate obtained in step S2, part A of the sludge obtained by pretreatment in step S1, and metakaolin, and then mix and stir the mixture with water;

Step S4, recycled coarse aggregate processing

Spray water on the regenerated coarse aggregate obtained in step S2 so that the regenerated coarse aggregate is in a saturated surface dry state;

Step S5: Preparing green concrete

The recycled coarse aggregate obtained in step S4, part B of the recycled fine aggregate obtained in step S3, the sludge obtained in step S1, cement, water and water-reducing agent are mixed and stirred to finally obtain the target product green concrete.

Preferably, in step S1, the sludge and quicklime are stirred and left to dry and grind, specifically including the following operations:

The sludge is sieved, and the sifted sludge and quicklime are mixed and stirred in a weight ratio of 100:6-16, left to dry, and then ground to 0.08mm before use.

Preferably, step S2 removes impurities in waste concrete and crushes it to obtain regenerated coarse aggregate and regenerated fine aggregate, which specifically includes the following operations:

Step S21: Preliminarily crush the waste concrete and clean up the debris;

Step S22: Continue secondary crushing to obtain a mixture with a diameter of less than 35 cm;

Step S23: further sieve the mixture obtained in step S22 to obtain regenerated coarse aggregate and regenerated fine aggregate respectively.

Preferably, in step S3, the regenerated fine aggregate obtained in step S2, part A of the sludge obtained by pretreatment in step S1, and metakaolin are fully mixed, and then the mixture and water are mixed and stirred, specifically including the following operations:

Step S31: Mix the recycled fine aggregate obtained in step S2, the sludge obtained by pretreatment in step S1, metakaolin, and cement in a mass ratio of 100:5-10:0-5:2 to obtain a mixture;

Step S32: Mix the mixture and water at a mass ratio of 100:1-4, where water is added while stirring and spraying until the water is added, and cured for at least 7 days before use.

Preferably, in step S5, the regenerated coarse aggregate obtained by step S4 of step B, the regenerated fine aggregate obtained by step S3, the sludge obtained by step S1, cement, water and water reducing agent are mixed and stirred, Finally, the target product green concrete is obtained, which specifically includes the following step;

Step S51: Fully stir the recycled coarse aggregate obtained in step S4 and the recycled fine aggregate obtained in step S3;

Step S52: Continue to add the sludge obtained in step S1 and stir thoroughly;

Step S53: Add water and water-reducing agent, stir thoroughly, and finally obtain the target product green concrete;

Among them, the weight ratio of the recycled coarse aggregate obtained in step S4, the recycled fine aggregate obtained in step S3, the sludge obtained in step S1, cement, water and water reducing agent is 65-75:190-200:20- 30:90-110:35-40:2-4.

Preferably, the cement is ultrafine cement, with a median particle size D50 below 1 um, a maximum particle size no more than 18 um, and more than 80% of the particle sizes below 5 um.

Preferably, the water reducing agent is an anti-mud type high-efficiency water reducing agent.

Preferably, the metakaolin is obtained by grinding kaolinite and calcining it at 600-900°C, with a fineness of 4000-18000m ² /Kg.

Preferably, the weight ratio of Part A to Part B is 100: (50-200).

The present invention at least includes the following beneficial effects:

(1) This invention uses a large amount of waste concrete, rivers, lakes and sea silt and other waste as raw materials, and consumes a large amount of construction waste. It not only realizes the resource reuse of construction waste, but also reduces the high energy consumption generated by traditional methods. It is A green recycling technology, the invented concrete can be used in rural cement concrete pavements, low-grade highways and non-institutional concrete, with broad application prospects and considerable benefits.

(2) In the technology of solving waste concrete fine aggregate and dredged silt, the present invention avoids the low added value, high energy consumption, fierce market competition and the need for downstream technologies that exist in traditional technologies (such as making ceramsite, making bricks, and roadbed). The issue of project acceptance has maximized the value of construction waste and achieved obvious economic benefits.

(3) The present invention utilizes the expansion component in the sludge (if not, a small amount of calcined metakaolin is added), dry-mixes the regenerated fine aggregate to fill the gaps in the fine aggregate, and sprays a small amount of water to realize the expansion of the expansion component in the gap. Expansion provides expansion force to achieve tight filling of fine aggregate gaps, effectively improving the problem of low strength of recycled fine aggregates.

(4) The waste concrete of the present invention is fully graded for utilization, which avoids the use of fine aggregates for the base layer in traditional utilization methods, and reduces the cost of repeated transportation and the loss of added value caused by the downgraded use of materials in the process.

(5) The concrete prepared by the present invention can absorb about 40% of waste concrete and more than 5% of silt while ensuring that the concrete strength is not less than 30MPa. Compared with ordinary C30 concrete, this method saves 45% of new construction materials.

Other advantages, objects, and features of the present invention will be apparent in part from the description below, and in part will be understood by those skilled in the art through study and practice of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the examples, so that those skilled in the art can implement it according to the text of the description.

The following description is provided to disclose the invention to enable those skilled in the art to practice the invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious modifications. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the invention.

It should be understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in other embodiments, the number of the element may be The number may be multiple, and the term "one" shall not be understood as a limitation on the number.

Example 1:

(1) Pretreatment of sludge:

After filtering the dredged sediment from rivers, lakes and seas through a 10cm mesh, add 6 parts of quicklime for every 100 parts of silt (water content), stir and let stand for 2 days, after drying, grind it to less than 0.08mm for later use, and divide it into two parts, part A and part B respectively.

(2) Crushing of waste concrete

1) Preliminarily crush the waste concrete and clean up debris such as steel bars;

2) Crush the above-mentioned waste concrete twice to obtain a mixture with a diameter of less than 35cm;

3) Sieve the above mixture with a 5mm square hole sieve to obtain recycled coarse aggregate and recycled fine aggregate respectively.

(3) Regenerated fine aggregate treatment

1) Fully mix the recycled fine aggregate with part A of the pretreated sludge obtained in (1) according to the ratio of fine aggregate: silt: cement = 100:10:2;

2) Stir the above mixture and water in a ratio of 100:3. Water is added by spraying, stirring while spraying, until the water is added, and cured for at least 7 days before use.

(4) Treatment of recycled coarse aggregate

Spray water on the recycled coarse aggregate so that the recycled coarse aggregate is in a saturated and dry state.

(5) Green concrete preparation

Combine (4) medium recycled coarse aggregate, ordinary aggregate, (3) medium recycled fine aggregate, part B of the pretreated sludge in (1), cement, water and water reducing agent according to 65:210:190:20: Stir in a ratio of 110:35:3. When stirring, first fully stir the recycled coarse aggregate, ordinary aggregate, and recycled fine aggregate for 1 minute, then add silt and cement in sequence and stir for 1 minute, and finally add water and water-reducing agent to stir. In 3 minutes, green concrete containing silt and fully graded waste concrete is produced.

Green concrete containing silt and fully graded waste concrete was finally produced. In this example, the fully graded waste concrete accounted for about 40.3% of the total weight, the absolute dry silt accounted for about 5.9% of the total weight, and the compressive strength was about 39.5MPa. .

Example 2:

(1) Pretreatment of sludge:

After filtering the dredged sediment from rivers, lakes and seas through a 10cm mesh, add: 16 parts of quicklime for every 100 parts of sludge (water content), stir and let stand for 4 days. After drying, grind to less than 0.08mm for later use. It is divided into two parts, namely Part A and Part B.

(2) Crushing of waste concrete

(3) Regenerated fine aggregate treatment

1) Fully mix the recycled fine aggregate and part A of the pretreated sludge obtained in (1) according to the ratio of fine aggregate: silt: metakaolin: cement = 100:5:5:2;

2) Stir the above mixture and water in a ratio of 100:2. Water is added by spraying, stirring while spraying, until the water is added, and cured for at least 7 days before use.

(4) Treatment of recycled coarse aggregate

(5) Green concrete preparation

Combine (4) medium recycled coarse aggregate, ordinary aggregate, (3) medium recycled fine aggregate, part B of the pretreated sludge in (1), cement, water and superplasticizer according to 75:190:200:30: Stir in a ratio of 110:40:4. When stirring, first fully stir the recycled coarse aggregate, ordinary aggregate, and recycled fine aggregate for 1 minute, then add silt and cement in sequence and stir for 1 minute, and finally add water and water-reducing agent and stir. In 3 minutes, green concrete containing silt and fully graded waste concrete is produced.

Green concrete containing silt and fully graded waste concrete was finally produced. In this example, the fully graded waste concrete accounted for approximately 43.4% of the total weight, the absolute dry silt accounted for approximately 7.6% of the total weight, and the compressive strength was approximately 30.4MPa. .

Example 3:

(1) Pretreatment of sludge:

After filtering the dredged sediment from rivers, lakes and seas through a 10cm screen, add: 10 parts of quicklime for every 100 parts of sludge (water content), stir and let stand for 4 days. After drying, grind to less than 0.08mm for later use. It is divided into two parts, namely Part A and Part B.

(2) Crushing of waste concrete

(3) Regenerated fine aggregate treatment

1) Fully mix the recycled fine aggregate and part A of the pretreated sludge obtained in (1) according to the ratio of fine aggregate: silt: metakaolin: cement = 100:10:5:2;

(4) Treatment of recycled coarse aggregate

(5) Green concrete preparation

Combine (4) medium recycled coarse aggregate, ordinary aggregate, (3) medium recycled fine aggregate, part B of the pretreated sludge in (1), cement, water and water reducing agent according to 70:200:195:30: Stir in a ratio of 90:40:4. When stirring, first fully stir the recycled coarse aggregate, ordinary aggregate, and recycled fine aggregate for 1 minute, then add silt and cement in sequence and stir for 1 minute, and finally add water and water-reducing agent and stir. In 3 minutes, green concrete containing silt and fully graded waste concrete is produced.

Green concrete containing silt and fully graded waste concrete was finally produced. In this example, the fully graded waste concrete accounted for approximately 41.9% of the total weight, the absolute dry silt accounted for approximately 8.8% of the total weight, and the compressive strength was approximately 31.2MPa. .

Example 4:

(1) Pretreatment of sludge:

After filtering the dredged sediment from rivers, lakes and seas through a 10cm screen, add: 10 parts of quicklime for every 100 parts of sludge (water content), stir and let stand for 5 days. After drying, grind to less than 0.08mm for later use. It is divided into two parts, namely Part A and Part B.

(2) Crushing of waste concrete

(3) Regenerated fine aggregate treatment

(4) Treatment of recycled coarse aggregate

(5) Green concrete preparation

Combine (4) medium recycled coarse aggregate, ordinary aggregate, (3) medium recycled fine aggregate, part B of the pretreated sludge in (1), cement, water and water reducing agent according to 70:205:190:20: Stir in a ratio of 100:35:4. When stirring, first fully stir the recycled coarse aggregate, ordinary aggregate, and recycled fine aggregate for 1 minute, then add silt and cement in sequence and stir for 1 minute, and finally add water and water-reducing agent and stir. In 3 minutes, green concrete containing silt and fully graded waste concrete is produced.

Green concrete containing silt and fully graded waste concrete was finally produced. In this embodiment, the fully graded waste concrete accounted for approximately 41.1% of the total weight, the absolute dry silt accounted for approximately 7.1% of the total weight, and the compressive strength was approximately 34.1MPa. .

To sum up, it can be seen from the data of Examples 1-4 that the concrete prepared by the present invention can absorb about 40% of waste concrete and more than 5% of silt while ensuring that the concrete strength is not less than 30MPa. , equivalent to ordinary C30 concrete, this method saves 45% of building materials and has good application prospects.

Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and embodiments. They can be applied to various fields suitable for the present invention. For those familiar with the art, they can easily Additional modifications may be made, and the invention is therefore not limited to the specific details and embodiments shown and described herein without departing from the general concept defined by the claims and equivalent scope.

Claims

A method for preparing green concrete based on silt and waste concrete, which is characterized by including the following steps:

Step S1, sludge pretreatment

Stir the sludge and quicklime, let it stand, dry and grind, to obtain the treated sludge, which is divided into two parts, namely Part A and Part B;

Step S2: Crushing waste concrete

Remove debris from waste concrete and crush and screen it to obtain recycled coarse aggregate and recycled fine aggregate;

Step S3, recycled fine aggregate processing

Fully mix the regenerated fine aggregate obtained in step S2, part A of the sludge obtained by pretreatment in step S1, metakaolin, and cement, and then mix and stir the mixture with water;

Step S4, recycled coarse aggregate processing

Spray water on the regenerated coarse aggregate obtained in step S2 so that the regenerated coarse aggregate is in a saturated surface dry state;

Step S5: Preparing green concrete

The recycled coarse aggregate obtained in step S4, the recycled fine aggregate obtained in step S3, part B of the sludge obtained in step S1, cement, water and water-reducing agent are mixed and stirred to finally obtain the target product green concrete.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that in step S1, the silt and quicklime are stirred and left to dry and grind, specifically including the following operations:

The sludge is sieved, and the sifted sludge and quicklime are mixed and stirred in a weight ratio of 100:6-16, left to dry, and then ground to 0.08mm before use.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that, in step S2, the debris in the waste concrete is removed and crushed to obtain regenerated coarse aggregate and regenerated coarse aggregate. Fine aggregate, specifically including the following operations:

Step S21: Preliminarily crush the waste concrete and clean up the debris;

Step S22: Continue secondary crushing to obtain a mixture with a diameter of less than 35 cm;

Step S23: further sieve the mixture obtained in step S22 to obtain regenerated coarse aggregate and regenerated fine aggregate respectively.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that in step S3, the regenerated fine aggregate obtained in step S2, part A of the silt pretreated in step S1 and partial The kaolin clay is thoroughly mixed, and then the mixture and water are mixed and stirred, including the following operations:

Step S31: Mix the recycled fine aggregate obtained in step S2, the sludge obtained by pretreatment in step S1, metakaolin, and cement in a mass ratio of 100:5-10:0-5:2 to obtain a mixture;

Step S32: Mix the mixture and water at a mass ratio of 100:1-4, where water is added while stirring and spraying until the water is added, and cured for at least 7 days before use.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that in step S5, the regenerated coarse aggregate obtained in step S4, the regenerated fine aggregate obtained in step S3, and Part B of the sludge obtained through S1 treatment is mixed with cement, water and superplasticizer to finally obtain the target product green concrete, which specifically includes the following steps;

Step S51: Fully stir the recycled coarse aggregate obtained in step S4 and the recycled fine aggregate obtained in step S3;

Step S52: Continue to add the sludge obtained in step S1 and stir thoroughly;

Step S53: Add water and water-reducing agent, stir thoroughly, and finally obtain the target product green concrete;

Among them, the weight ratio of the recycled coarse aggregate obtained in step S4, the recycled fine aggregate obtained in step S3, part B of the sludge obtained in step S1, and cement, water and water reducing agent is 65-75:190-200 :20-30:90-110:35-40:2-4.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that the cement is ultrafine cement, the median particle diameter D50 is below 1um, the maximum particle diameter does not exceed 18um, and more than 80% The particle size is below 5um.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that the water reducing agent is an anti-mud type high-efficiency water reducing agent.
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that the metakaolin is obtained by grinding kaolin and calcining it at 600-900°C, and the fineness is 4000-18000m2 /Kg .
The preparation method of green concrete based on silt and waste concrete according to claim 1, characterized in that the weight ratio of part A and part B is 100: (50-200).