CN112759293A

CN112759293A - Concrete admixture, concrete product and preparation method thereof

Info

Publication number: CN112759293A
Application number: CN202011643518.9A
Authority: CN
Inventors: 董鹏飞; 李华军
Original assignee: Shenzhen Tutao Environmental Protection Technology Co ltd
Current assignee: Shenzhen Tutao Environmental Protection Technology Co ltd
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2021-05-07

Abstract

A concrete admixture, a concrete product and a preparation method thereof, the preparation method of the concrete admixture comprises the following steps: adding water into engineering slag soil, and mixing to obtain slurry with the Baume degree of 1.8-2.5, wherein the main component of the engineering slag soil contains kaolin; purifying the slurry to remove quartz particles, plant fibers, hematite and pyrolusite from the slurry; drying, calcining and pulverizing the purified slurry to obtain the concrete admixture; wherein the calcining conditions are as follows: calcining the dried particles of the slurry at 600-800 ℃ for 100-200 min, and then rapidly cooling to normal temperature at a speed of more than or equal to 7 ℃/s. The invention also provides the prepared concrete admixture and a concrete product. The concrete admixture prepared by the invention can be added into concrete to obviously improve the flexural strength and compressive strength of the concrete, and provides a recycling solution for engineering slag soil treatment.

Description

Concrete admixture, concrete product and preparation method thereof

Technical Field

The invention relates to the technical field of resource utilization of sand making wastes, in particular to a concrete admixture and a concrete product which take engineering slag as a raw material and a preparation method thereof.

Background

With the rapid development of economic and urbanized construction, the demand of the construction industry for gravels is greatly increased, and the traditional cobblestones and river sand can not meet the increased demand of the construction industry. At present, the coarse aggregate and the fine aggregate required by the building industry are obtained by crushing rocks and washing and dressing the soil formed by weathered rocks. However, the process of preparing coarse aggregate and fine aggregate by adopting broken rock and washed soil brings a large amount of engineering dregs such as sand washing mud and the like. At present, the engineering dregs are generally used as construction waste for landfill and stacking treatment, which brings certain environmental pollution problem and resource waste.

Disclosure of Invention

In view of the above, the present invention provides a concrete admixture, a concrete product and a method for preparing the same, which are intended to at least partially solve at least one of the above-mentioned technical problems.

In order to achieve the purpose, the technical scheme of the invention is as follows:

as one aspect of the invention, the invention provides a method for preparing a concrete admixture by taking engineering slag as a raw material, which comprises the following steps: adding water into engineering slag soil, and mixing to obtain slurry with the Baume degree of 1.8-2.5, wherein the main component of the engineering slag soil contains kaolin; purifying the slurry to remove quartz particles, plant fibers, hematite and pyrolusite from the slurry; drying, calcining and pulverizing the purified slurry to obtain the concrete admixture; wherein the calcining conditions are as follows: calcining the dried particles of the slurry at 600-800 ℃ for 100-200 min, and then rapidly cooling to normal temperature at a speed of more than or equal to 7 ℃/s.

As another aspect of the invention, there is provided a concrete admixture produced by the method as described above.

As a further aspect of the present invention, there is provided a concrete product prepared from the following raw materials in parts by weight: 40-80 parts of the concrete admixture, 320-360 parts of Portland cement, 1600 parts of stones with the particle size of 3-5 mm and 150 parts of water.

Based on the technical scheme, the concrete admixture, the concrete product and the preparation method thereof have at least one or part of the following beneficial effects:

(1) the invention provides a method for preparing a metakaolin-like high-activity concrete admixture by taking engineering slag soil as a raw material, and provides a solution for recycling solid wastes for the treatment of the engineering slag soil.

(2) The concrete admixture prepared by the invention can obviously improve the flexural strength and compressive strength of concrete when being added into the concrete.

Drawings

FIG. 1 shows the steps of preparing a high-activity concrete admixture by using engineering slag as a raw material in the embodiment of the invention.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments. Unless otherwise specified, percentages included herein generally refer to weight percentages.

Through analysis of the components of the engineering slag soil, the main components of the engineering slag soil formed by preparing coarse aggregate or fine aggregate from the soil mass formed by granite or weathered granite as a raw material are kaolin, feldspar, mica, fine quartz particles, a small amount of colored hematite, pyrolusite and organic matters, wherein SiO is₂+Al₂O₃The content is more than or equal to 70 wt%. Aiming at the engineering slag soil, the invention provides a concrete admixture taking the engineering slag soil as a raw material, a concrete product and a preparation method thereof, and aims to partially solve the problems of environmental pollution and resource waste caused by stacking and burying the engineering slag soil.

According to some embodiments of the present invention, there is provided a method of preparing a high activity concrete admixture, comprising the steps of (as shown in fig. 1):

firstly, pulping:

the engineering residue soil is added with water and adjusted to be slurry with the Baume degree of 1.8-2.5, the preferred concentration is 2.0-2.2, the deposition phenomenon can occur when the concentration is too high, the purification is not facilitated, the concentration is too low, and the drying energy consumption is increased.

And a second step, purification:

the slurry is purified to remove impurities such as quartz particles, plant fibers, hematite, pyrolusite and the like in the slurry.

In some embodiments, the step of purifying specifically comprises: the slurry was wet screened using a screen of > 150 mesh to remove oversize material (mainly fine quartz particles and fine plant fibers). And then removing colored hematite and pyrolusite in the slurry under the sieve by using an iron remover, and controlling the total content of iron oxide and manganese oxide in the slurry to be lower than 1.5 wt%.

In other embodiments, the combined purification of screening and de-ironing separator may be replaced by a combined purification of gravity separation, flotation and centrifugation, as well as a purified slurry of fine quartz particles, fine plant fibers, colored hematite and pyrolusite. The specific steps of gravity separation, flotation and centrifugal separation are conventional process steps in the field and are not described in detail herein.

Step three, drying:

and drying the purified slurry in a drying mode including dehydration drying, spray drying and the like. In some embodiments, the step of dehydrating drying specifically comprises: the purified slurry is pressed and filtered to form a mud cake, so that SiO in the mud cake₂+Al₂O₃The content is more than or equal to 79 wt%; then the mud cake is put into a drier for drying, so that the water content of the mud cake is less than or equal to 2 wt%. If SiO in mud cake₂+Al₂O₃When the content is too low (less than 70%), the mechanical strength of the concrete cannot be improved and even the mechanical strength is reduced when the mud cake is used as a concrete admixture after being calcined as a raw material.

In some embodiments, the step of spray drying specifically comprises: the purified slurry is directly dried into powder by using a conventional spray dryer, the water content of the slurry is reduced to less than or equal to 7 wt%, the spray drying simplifies the operation compared with dehydration drying, and the crushing procedure before calcination is omitted.

Step four, calcining:

compared with the method of directly calcining mud cakes, the method of calcining mud cakes by using particles has the advantages that the temperature rising rate and the temperature reducing rate of the particles are higher, the calcining time is saved, the activity of the calcined metakaolin is higher, and the mechanical property of a concrete product prepared by mixing the metakaolin into concrete is better. Therefore, the mud cake obtained by the dehydration drying mode is crushed into particles with the particle size of less than 10mm, preferably, the particles with the particle size of less than 5mm and the average particle size of less than 1.5mm, and then the crushed mud cake is sent into a calcining kiln with the temperature of 600-800 ℃, preferably 650-750 ℃ for calcining for 100-200 min, preferably 130-150 min. The calcining kiln is a clean heat source calcining kiln which takes electric heat or natural gas as fuel. After calcining and sintering, rapidly cooling, cooling the particles to normal temperature, wherein the cooling rate is more than or equal to 7 ℃/s, preferably more than or equal to 9 ℃/s.

The invention firstly crushes mud cakes into particles with the particle size less than 10mm, then calcinates the particles at 600-800 ℃ for 100-200 min, thus finishing the calcination of the metakaolin into metakaolin, and then rapidly cools the metakaolin to obtain the admixture with the highest activity.

Fifthly, pulverization:

and (3) pulverizing the cooled particles, and screening the pulverized particles by using a screen of 400-650 meshes to prepare the metakaolin-like concrete admixture.

According to some embodiments of the present invention, there is provided a concrete admixture produced by the method of preparation as described above.

According to some embodiments of the present invention, there is also provided a concrete product, which is prepared from the following raw materials in parts by weight: 40-80 parts of the concrete admixture, 320-360 parts of portland cement, 1600 parts of stones with the particle size of 3-5 mm and 150 parts of water. Specifically, the raw materials are stirred for 2-3 minutes, and then are placed into a die to be molded and pressed to obtain the pervious concrete product.

Preferably, the raw material comprises the following components in parts by weight: 40-60 parts of the concrete admixture, 340-360 parts of PO42.5 cement, 1600 parts of stones with the particle size of 3-5 mm and 150 parts of water.

The concrete product includes but is not limited to pervious concrete members, pervious bricks, precast concrete slabs, concrete pipes, rain covers and the like.

The technical solution of the present invention will be described in detail below by referring to a plurality of specific examples. It should be noted that the following specific examples are only for illustration and are not intended to limit the invention.

Example 1

The method is used for treating the engineering muck of weathered granite soil, and comprises the following steps:

firstly, pulping: adding water into the engineering residue soil to adjust the engineering residue soil into slurry with the Baume degree of 2.2.

And a second step, purification: the slurry was wet screened using a 200 mesh screen to remove oversize material (mainly fine quartz particles and fine plant fibers). And then removing colored hematite and pyrolusite in the slurry under the sieve by using an iron remover, and controlling the total content of iron oxide and manganese oxide in the slurry to be lower than 1.5 wt%.

Step three, dehydration and drying: the purified slurry is pressed and filtered to form a mud cake, so that SiO in the mud cake₂+Al₂O₃The content is more than or equal to 79 wt%; then the mud cake is put into a drier for drying, so that the water content of the mud cake is less than or equal to 2 wt%.

Step four, calcining: crushing the dewatered and dried mud cake into particles smaller than 10mm, and then feeding the particles into a calcining kiln at the temperature of 700 ℃ for calcining for 140 min. The calcining kiln is a clean heat source calcining kiln which takes electric heat or natural gas as fuel. After the calcining and sintering, the granules are rapidly cooled, the granules are cooled to normal temperature (generally 20-25 ℃), and the cooling rate is 9 ℃/s.

Fifthly, pulverization: and (4) pulverizing the cooled particles, and screening the pulverized particles by a 400-mesh screen to prepare the concrete admixture.

Example 2

Similar to the operation of example 1, except that the weathered granite earthen engineering muck was replaced with coal gangue engineering muck.

Examples 3 to 5

Similar to the operation of example 1, except that the calcination conditions shown in Table 1 were used in examples 3 to 5, in which example 3 crushed the mud cake to 100mm or less, the calcination temperature of example 4 was 750 ℃ and the cooling rate of example 5 was natural cooling.

TABLE 1

Example 6

The concrete admixture of example 1 was prepared in a weight ratio of PO42.5 cement to gravel to reactive concrete admixture prepared from engineering slag to water of 352: 1600: 48: 150 to give a test block in which the admixture ratio of concrete admixture was 12% for concrete admixture/(concrete admixture + cement). The test block is a cube 150mm by manufactured according to GJJT 135-2009 technical Specification for permeable cement concrete pavements.

Example 7 to example 11

Similar to example 6, except that examples 7 to 10 were concrete admixtures prepared in examples 2 to 5, respectively, in place of the reactive concrete admixtures in example 6, and example 11 was a mixture ratio of the concrete admixtures in example 6 was adjusted from 12% to 20%.

Comparative experiment 1

Comparative run 1 was conducted similarly to example 6, except that no concrete admixture was added.

And (3) performance testing: the test pieces of examples 6 to 11 and comparative test 1 were each subjected to a strength property test under a standard curing condition (temperature 20. + -. 2 ℃ C., relative humidity of 95% or more) by a standard test method, and the results are shown in Table 2. From Table 2, it can be known that the high-activity concrete admixture prepared from the engineering slag soil can improve the flexural strength of the pervious concrete by 2.6-9.2% and the compressive strength by 14-19% when added into the pervious concrete.

TABLE 2 pervious concrete Strength Performance data

From the results in the table, it can be seen that, compared with comparative test 1, the flexural strength and the compressive strength of the concrete admixture added in example 6 are significantly improved, which indicates that the concrete admixture provided in example 6 is very beneficial for improving the flexural strength and the compressive strength of the concrete;

compared with the comparative test 1, the compressive strength of the concrete admixture is slightly improved in the example 7, but the improvement effect is far inferior to that of the example 6, and the difference between the example 7 and the example 6 is mainly that the sources of engineering slag for preparing the concrete admixture are different, which shows that the activity of the metakaolin-like concrete admixture is more favorable when the engineering slag is weathered from granite soil;

compared with the comparative test 1, the compressive strength and the flexural strength of the concrete admixture are improved in the example 8, but the improvement effect is far inferior to that of the concrete admixture in the example 6, and the difference between the example 8 and the example 6 is mainly that the dry particle size of the slurry is different during calcination, which indicates that the activity of the metakaolin-like concrete admixture is unfavorable for improvement due to the excessive particle size;

compared with the comparative test 1, the compressive strength and the flexural strength of the concrete admixture are obviously improved, and the improvement effect is even better than that of the concrete admixture of the example 6, which shows that the calcination temperature is increased to 750 ℃ to be more beneficial to improving the activity of the concrete admixture;

compared with the comparative test 1, the compressive strength and the flexural strength of the admixture are improved in the example 10, but the improvement effect is not as good as that of the admixture in the example 6, and the cooling speed after calcination is different from that of the admixture in the example 10, so that the rapid cooling mode can improve the activity of the admixture compared with the natural cooling mode;

although the compressive strength and the flexural strength of example 11 were improved as compared with those of comparative test 1, the improvement effect was inferior to that of example 6, and example 11 was different from example 6 mainly in the blending ratio of the concrete admixture, indicating that too high a blending ratio is disadvantageous in improving the strength of the concrete.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a concrete admixture by taking engineering slag as a raw material comprises the following steps:

adding water into engineering slag soil, and mixing to obtain slurry with the Baume degree of 1.8-2.5, wherein the main component of the engineering slag soil contains kaolin;

purifying the slurry to remove quartz particles, plant fibers, hematite and pyrolusite from the slurry;

drying, calcining and pulverizing the purified slurry to obtain the concrete admixture;

wherein the calcining conditions are as follows: calcining the dried particles of the slurry at 600-800 ℃ for 100-200 min, and then rapidly cooling to normal temperature at a speed of more than or equal to 7 ℃/s.

2. The method of claim 1, wherein the engineered slag is formed from a raw material of granite or weathered granite argillaceous material, wherein SiO is₂+Al₂O₃The content is more than or equal to 70 wt%.

3. The method of claim 1, wherein the baume degree of the slurry is 2.0 to 2.2.

4. The method of claim 1, wherein the slurry is purified by a combination of wet screening and de-ironing or a combination of gravity separation, flotation and centrifugation.

5. A method according to claim 1 or 4, characterized in that the total content of iron oxide and manganese oxide in the slurry after purification is less than 1.5% by weight.

6. The method of claim 1, wherein drying the purified slurry is by dehydration drying, comprising:

filter-pressing the purified slurry to form a mud cake, so that SiO in the mud cake₂+Al₂O₃The content is more than or equal to 79 wt%;

putting the mud cakes into a dryer for drying to ensure that the water content of the mud cakes is less than or equal to 2 wt%;

and crushing the dried mud cake into particles with the particle size less than 10 mm.

7. The method of claim 1, wherein drying the purified slurry is by spray drying comprising:

and drying the purified slurry into powder by using a spray dryer, and reducing the water content of the slurry to less than or equal to 7 wt%.

8. The method according to claim 1, characterized in that the calcination conditions are: calcining the dried particles of the slurry at 650-750 ℃ for 130-150 min, and then rapidly cooling to normal temperature at a speed of more than or equal to 9 ℃/s.

9. A concrete admixture made by the method of any one of claims 1 to 6.

10. A concrete product is prepared from the following raw materials in parts by weight:

40 to 80 parts of the concrete admixture according to claim 9, 320 to 360 parts of portland cement, 1600 parts of stones with a particle size of 3 to 5mm, and 150 parts of water.