CN114380562B

CN114380562B - Preparation method of anti-freezing recycled concrete and anti-freezing recycled concrete

Info

Publication number: CN114380562B
Application number: CN202210181122.XA
Authority: CN
Inventors: 王辉; 肖云; 马淑梅; 李腾飞; 崔坤栋; 刘传海; 夏秀成; 王泽洋; 张娟
Original assignee: Qingdao Everbright Group Engineering Co ltd
Current assignee: Qingdao Everbright Group Engineering Co ltd
Priority date: 2022-02-25
Filing date: 2022-02-25
Publication date: 2022-11-08
Anticipated expiration: 2042-02-25
Also published as: CN114380562A

Abstract

The application relates to the field of concrete materials, and particularly discloses a preparation method of anti-freezing recycled concrete and the anti-freezing recycled concrete. A preparation method of anti-freezing recycled concrete comprises the following steps: crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in the graphene oxide dispersion liquid, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surface is anhydrous to obtain a regenerated coarse aggregate; according to parts by weight, 270-290 parts of cement, 830-850 parts of recycled coarse aggregate, 830-850 parts of fine aggregate, 110-130 parts of admixture, 40-50 parts of waste foamed rubber powder, 170-180 parts of water, 6-8 parts of anti-freezing water reducer and 5-10 parts of expansion crack resistance agent are taken and uniformly stirred, and the anti-freezing recycled concrete is obtained. The anti-freezing recycled concrete prepared by the method has a good freeze-thaw resistance effect and excellent mechanical strength.

Description

Preparation method of anti-freezing recycled concrete and anti-freezing recycled concrete

Technical Field

The application relates to the field of concrete materials, in particular to early-strength antifreezing concrete and a preparation method thereof.

Background

Concrete is a general term for engineering mixed materials which integrate aggregate by cementitious materials and is widely applied to civil engineering. Concrete is required to have different functions according to the use environment. Because the region of China is vast and the temperature in northern regions is generally below-5 ℃ in winter, the concrete is required to have certain freeze-thaw resistance. The main reason for the damage of common concrete caused by freezing is that the ice crystal is increased at low temperature and the structure of the concrete is damaged due to pressure, and the use of the anti-freezing additive is an effective method for improving the freezing resistance of the concrete.

However, as for recycled concrete, as the used aggregate is crushed from waste concrete, compared with natural aggregate, the recycled aggregate has more surface cracks and high water absorption rate, and the expansion pressure of the cement stone generated by freezing water in concrete pores at low temperature can aggravate the growth of fine cracks, so that the recycled aggregate is more easily damaged at low temperature; in addition, the interface bonding strength between mortar and recycled aggregate in the concrete is deteriorated under low temperature conditions, and the durability of the concrete is further affected. Obviously, the current formula design of the anti-freezing concrete is not well suitable for recycled concrete.

Disclosure of Invention

In order to solve the problems, the application provides a preparation method of anti-freezing recycled concrete and the anti-freezing recycled concrete.

In a first aspect, the application provides a preparation method of anti-freezing recycled concrete, which adopts the following technical scheme: a preparation method of anti-freezing recycled concrete comprises the following steps:

crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in the graphene oxide dispersion liquid, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surfaces of the prefabricated coarse aggregate particles are anhydrous to obtain a regenerated coarse aggregate;

according to parts by weight, 270-290 parts of cement, 830-850 parts of recycled coarse aggregate, 830-850 parts of fine aggregate, 110-130 parts of admixture, 40-50 parts of waste foamed rubber powder, 170-180 parts of water, 6-8 parts of anti-freezing water reducer and 5-10 parts of expansion crack resistance agent are taken and evenly stirred, and the anti-freezing recycled concrete is obtained.

The recycled coarse aggregate is obtained by crushing waste concrete, so that the recycled coarse aggregate has more cracks and high water absorption rate, the anti-freezing effect is inferior to that of common concrete, modification and reinforcement treatment needs to be carried out on the recycled coarse aggregate in order to improve the performance of the concrete, and the traditional modifying method of the recycled coarse aggregate is complex, low in efficiency and difficult to operate. By adopting the technical scheme, the waste concrete is soaked in the graphene oxide dispersion liquid, no additional particle shaping or complex strengthening process is needed, the mechanical strength of the recycled aggregate can be improved by treating the graphene oxide dispersion liquid, the mass loss rate of the recycled concrete can be reduced under freeze-thaw cycle, and the performance of the recycled coarse aggregate is improved, so that the anti-freezing performance of the recycled coarse aggregate is improved.

In addition, the antifreezing water reducing agent of the present application can be selected from common antifreezing water reducing agents having antifreezing effects, and the types thereof are not particularly limited as long as certain antifreezing and water reducing effects can be achieved. Under the low-temperature freeze-thaw environment, the water in the concrete is subjected to the alternating action of positive and negative temperature, so that the volume-shrinkage periodic change occurs, the periodic fatigue stress is generated in the concrete, the bonding strength of the aggregate and the cementing material is influenced, and the compression strength and the breaking strength of the concrete are reduced. In order to solve the problems, the waste foamed rubber powder is added, and the rubber particles have rough surfaces and are easy to adsorb bubbles, so that the stability and uniformity of gas distribution in concrete can be improved, and the effect similar to that of an air entraining agent is achieved; and the interior of the foamed rubber has a fine pore structure, so that the foamed rubber has good elastic deformation capacity, can play a role in buffering the expansive force during water freeze thawing and delay the growth of microcracks, thereby improving the freeze-thaw resistance of the recycled concrete.

Preferably, 10-20 parts of redispersible latex powder and 4-6 parts of carboxymethyl cellulose are added into 300-400 parts of water and uniformly mixed, and then 30-40 parts of graphene oxide and 50-70 parts of nano silicon dioxide are added and uniformly mixed to obtain the graphene oxide dispersion.

By adopting the technical scheme, the carboxymethyl cellulose added into the graphene oxide dispersion liquid can improve the mixing and dispersing uniformity of all raw materials, and the graphene oxide dispersion liquid can be filled into the fine cracks of the recycled aggregate and forms a film, so that the water absorption rate of the recycled aggregate is reduced, the growth of the cracks is inhibited, and the performance of the recycled aggregate is improved.

Preferably, the waste foamed rubber powder is prepared by foaming the following raw materials in parts by weight: 100-120 parts of waste rubber powder, 10-20 parts of modified corncob powder, 1-2 parts of vulcanizing agent, 1-2 parts of accelerator, 1-2 parts of activator, 30-40 parts of plasticizer and 2-4 parts of foaming agent;

the modified corncob powder is obtained by processing corncobs through a graphene oxide dispersion liquid.

The corncob has the advantages that the corncob mainly comprises sugar and crude fiber, and a plurality of micro pores are formed in the corncob, so that the corncob has good elasticity; the obtained corncob-rubber composite material is used in concrete and can play a role in improving the early strength of the concrete. However, since the plant fiber in the corncob contains a large amount of polar groups such as hydroxyl groups and the like, the surface of the corncob has strong polarity and strong hygroscopicity, and the corncob has poor compatibility with rubber, the graphene oxide dispersion liquid can be adsorbed by utilizing the high adsorption force of the corncob through the treatment of the graphene oxide dispersion liquid, so that the surface performance of the corncob is improved, the compatibility of the corncob with the rubber is improved, and the obtained modified corncob is used as a filler of the foamed rubber, so that the pore structure of the foamed rubber can be enriched, and the elasticity of the foamed rubber at low temperature is improved.

Preferably, the waste foamed rubber powder is prepared by the following method: crushing waste rubber to obtain waste rubber particles;

according to the proportion, waste rubber particles are put into an internal mixer, after the internal mixing temperature is raised to 100-110 ℃, an activating agent, modified corncob powder and a plasticizer are added, after the internal mixing temperature is raised to 130-140 ℃, the internal mixing is carried out for 3-5min, and a first-stage rubber compound is obtained;

adding the first-stage rubber compound, the accelerator, the vulcanizing agent and the foaming agent into an internal mixer, raising the internal mixing temperature to 130-140 ℃, and continuing to stir for 3-5min to obtain a second-stage rubber compound;

vulcanizing the two-stage rubber compound for 200-250s under the conditions that the temperature is 160-170 ℃ and the pressure is 6-8MPa to obtain vulcanized rubber; and crushing and sieving the vulcanized rubber to obtain the waste foamed rubber powder.

By adopting the technical scheme, the waste foamed rubber powder takes waste rubber as a raw material, so that the production cost can be reduced, no additional carbon black is required to be added, and the preparation method is simple and easy to operate.

Preferably, the modified corncob meal is prepared by adopting the following method: and putting the dried corncobs into the graphene oxide dispersion liquid, fully soaking, drying, crushing and sieving to obtain the modified corncob powder.

Preferably, the fine aggregate is composed of medium sand and coarse sand in a weight ratio of 1.

By adopting the technical scheme, the fine aggregate consisting of the medium sand and the coarse sand can be filled into the framework built by the coarse aggregate, so that the compactness and the structural stability of the concrete can be improved, and the mechanical strength of the concrete is improved.

Preferably, the admixture consists of fly ash and mineral powder in a weight ratio of 1.5-2.

By adopting the technical scheme, the addition of the admixture can reduce the dosage of cement, thereby reducing the hydration heat of the cement and reducing the generation of concrete cracks; the addition of the fly ash and the mineral powder is beneficial to improving the early strength of the concrete and improving the frost resistance of the concrete.

In a second aspect, the present application provides an antifreeze recycled concrete prepared by the method of preparing antifreeze recycled concrete.

In summary, the present application has the following beneficial effects:

1. because this application will be wasted the concrete through the soaking treatment of peroxide graphite alkene dispersion, need not carry out extra granule plastic or complicated intensive process, through the processing of oxidation graphite alkene dispersion, can improve the mechanical strength of regeneration aggregate, moreover under freeze-thaw cycle, can reduce the quality loss rate of regeneration concrete, improve the performance of regeneration coarse aggregate to improve the freeze proof performance of regeneration coarse aggregate.

2. According to the method, the modified corncobs are added into the waste foamed rubber, so that the pore structure of the foamed rubber can be enriched, and the elasticity of the waste foamed rubber at a low temperature is improved; the obtained corncob-rubber composite material is used in recycled concrete and can play a role in improving the early strength of the concrete.

Detailed Description

The present application will be described in further detail with reference to examples.

Preparation example of graphene oxide dispersion liquid

The carboxymethyl cellulose in the following preparation examples had a viscosity of 1000; the particle size of the nano silicon dioxide is 400nm.

Preparation example 1 of graphene oxide dispersion liquid

Adding 1kg of redispersible latex powder and 0.4kg of carboxymethyl cellulose into 30kg of water with the temperature of 60 ℃, uniformly mixing, then adding 3kg of graphene oxide and 5kg of nano silicon dioxide, and uniformly mixing to obtain the graphene oxide dispersion.

Preparation example 2 of graphene oxide dispersion liquid

Adding 2kg of redispersible latex powder and 0.6kg of carboxymethyl cellulose into 40kg of water with the temperature of 60 ℃, uniformly mixing, then adding 4kg of graphene oxide and 7kg of nano silicon dioxide, and uniformly mixing to obtain the graphene oxide dispersion.

Preparation example of modified corncob meal the graphene oxide dispersion liquid in the following preparation example was prepared from preparation example 1 of a graphene oxide dispersion liquid.

Drying the corncobs at the temperature of 80 ℃ for 4h, taking 3kg of dried corncobs, adding 10kg of graphene oxide, fully soaking for 5h, taking out, drying at the temperature of 80 ℃ for 6h, crushing, and sieving with a 200-mesh sieve to obtain modified corncob powder.

Preparation example of waste foamed rubber powder

As shown in Table 1, the main difference between the preparation examples 1 to 3 of waste foamed rubber powders is the ratio of raw materials.

The following description will be made by taking a production example 1 of waste foamed rubber powder as an example. Except for special description, the raw materials in the preparation examples can be obtained by market, wherein the waste rubber powder in the preparation examples is from truck tires; the activator consists of zinc oxide and stearic acid in a weight ratio of 2; the plasticizer is paraffin oil; the accelerator consists of an accelerator DM (2, 2' -dithiodibenzothiazole) and an accelerator TMTD (tetramethylthiuram disulfide) in a weight ratio of 3; the vulcanizing agent is sulfur; the foaming agent is azodicarbonamide; the modified corncob meal is prepared from the preparation example of the modified corncob meal.

Preparation example 1 of waste foamed rubber powder

(1) Crushing waste rubber to obtain waste rubber particles with the average particle size of 15-20 mm;

putting waste rubber particles into an internal mixer, mixing and heating to 105 ℃, adding an activating agent, modified corncob powder and a plasticizer, mixing and heating to 135 ℃, and turning for 4min to obtain a first-stage rubber compound;

adding the first-stage rubber compound, the accelerator, the vulcanizing agent and the foaming agent into an internal mixer, continuously turning for 4min after the internal mixing temperature is raised to 135 ℃, adjusting the roller spacing, and discharging to obtain a second-stage rubber compound;

placing the two-stage rubber compound in a flat vulcanizing machine, and vulcanizing for 240s under the conditions that the temperature is 165 ℃ and the pressure is 7MPa to obtain vulcanized rubber;

and crushing the vulcanized rubber, and sieving the crushed vulcanized rubber by a 400-mesh sieve to obtain the waste foamed rubber powder.

TABLE 1 raw material compounding Table (unit: kg) of waste foamed rubber powder

Preparation example 4 of waste foamed rubber powder

The difference between the preparation example and the preparation example 4 of waste foamed rubber powder is that the modified corncob meal is replaced by an equal amount of unmodified common corncob meal.

Examples

As shown in Table 2, examples 1 to 3 are different in the ratio of raw materials.

The following description will be given by taking example 1 as an example. The starting materials in the examples are all commercially available, unless otherwise specified. Wherein the cement is P.O42.5 portland cement; the fine aggregate consists of medium sand and coarse sand with the weight ratio of 1; the fineness modulus of the medium sand is 2.9, and the mud content is 1.9%; the fineness modulus of the roughness is 3.2, and the mud content is 0.5%; the admixture consists of fly ash and mineral powder in a weight ratio of 1:1.8, wherein the fly ash is F-class II-grade fly ash, and the mineral powder is S95-grade mineral powder; the antifreezing water reducing agent has no special requirement, and can meet the antifreezing and water reducing effects, and the antifreezing water reducing agent in the embodiment is purchased from Qingdao Donghong spinning frame Co., ltd, and has the model of DH-7; the expansion crack-resistant agent is purchased from Wuhan three-source special building materials, inc., and has the model of SY-G.

Example 1: the anti-freezing recycled concrete is prepared by the following method:

s1, crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in graphene oxide dispersion liquid with the weight 3 times that of the prefabricated coarse aggregate particles for 6 hours, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surface of the prefabricated coarse aggregate particles is anhydrous to obtain regenerated coarse aggregate;

and S2, taking cement, the recycled coarse aggregate with the grain size of 5-31.5mm and continuous gradation, fine aggregate, admixture, waste foamed rubber powder, water, an anti-freezing water reducer and an expansion crack resistance agent in parts by weight, and uniformly stirring to obtain the anti-freezing recycled concrete.

Wherein the waste foamed rubber powder is prepared by the preparation example 1 of the waste foamed rubber powder.

TABLE 2 raw material usage Scale (unit: kg) for examples 1-3

Example 4

The present example is different from example 1 in that the waste foamed rubber powder is prepared by preparation example 2 of waste foamed rubber powder.

Example 5

This example is different from example 1 in that the waste foamed rubber powder is prepared by preparation example 3 of waste foamed rubber powder.

Example 6

This example is different from example 1 in that the waste foamed rubber powder is prepared by the preparation example 4 of the waste foamed rubber powder.

Comparative example

Comparative example 1

The comparative example differs from example 1 in S1 and S2.

S1 specifically comprises the following steps: crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in water with the weight 3 times of that of the prefabricated coarse aggregate particles for 6 hours, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surface is anhydrous to obtain the regenerated coarse aggregate.

And waste foamed rubber powder is not added into the raw material of S2.

Comparative example 2

The comparative example differs from example 1 in that S1 specifically includes the following steps: crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in water with the weight 3 times of that of the prefabricated coarse aggregate particles for 6 hours, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surface is anhydrous to obtain the regenerated coarse aggregate.

Performance test

The properties of the concrete of examples and comparative examples were measured according to the following methods, and the results are shown in Table 3.

The freezing resistance performance is as follows: according to GB/T50082-2009 Standard test method for long-term performance and durability of ordinary concrete, the maximum freezing-thawing cycle times of the concrete are tested by a slow freezing method.

Early crack resistance: according to the method in GB/T50082-2009 test method standards for long-term performance and durability of ordinary concrete, the total cracking area of the concrete test block in a unit area of 24h is measured.

Compressive strength and flexural strength: and (3) manufacturing a standard test block according to a method in GB/T50081-2016 standard of mechanical property test methods of common concrete, and measuring the compressive strength of the standard test block after 3d and 28d maintenance and the flexural strength of the standard test block after 28d maintenance.

Table 3 table for testing performance of concrete of examples and comparative examples

As can be seen by combining example 1 and comparative example 1 with Table 3, the antifreeze recycled concrete prepared by the method of the present application has good antifreeze performance, crack resistance, compressive strength and flexural strength. The properties of the recycled coarse aggregate obtained by the method can be improved, the recycled coarse aggregate can be used for completely replacing natural broken stones, and the waste foamed rubber powder is added as a filler, so that the properties of concrete can be improved under the condition of realizing resource recycling.

It can be seen from the combination of example 1 and example 6 that the frost resistance, crack resistance, compressive strength and flexural strength of the concrete of example 1 are significantly better than those of example 6, because the modified corncob can be used as a pore-forming agent when preparing the waste foamed rubber powder, so as to improve the pore structure of the rubber and the elasticity thereof at low temperature, and because the corncob is subjected to modification treatment, the compatibility of the corncob with the rubber can be significantly improved, so that the stability of the performance of the waste foamed rubber powder is improved, and the comprehensive performance of the concrete is improved.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The preparation method of the anti-freezing recycled concrete is characterized by comprising the following steps of:

crushing and screening waste concrete to obtain prefabricated coarse aggregate particles; fully soaking the prefabricated coarse aggregate particles in the graphene oxide dispersion liquid, taking out the prefabricated coarse aggregate particles, and airing the prefabricated coarse aggregate particles until the surface is anhydrous to obtain a regenerated coarse aggregate;

taking 270-290 parts of cement, 830-850 parts of regenerated coarse aggregate, 830-850 parts of fine aggregate, 110-130 parts of admixture, 40-50 parts of waste foamed rubber powder, 170-180 parts of water, 6-8 parts of anti-freezing water reducer and 5-10 parts of expansion crack resistance agent by weight parts, and uniformly stirring to obtain anti-freezing regenerated concrete;

the graphene oxide dispersion liquid is prepared by the following method: adding 10-20 parts by weight of redispersible latex powder and 4-6 parts by weight of carboxymethyl cellulose into 300-400 parts by weight of water, uniformly mixing, then adding 30-40 parts by weight of graphene oxide and 50-70 parts by weight of nano silicon dioxide, and uniformly mixing to obtain a graphene oxide dispersion liquid;

the waste foamed rubber powder is prepared by foaming the following raw materials in parts by weight: 100-120 parts of waste rubber powder, 10-20 parts of modified corncob powder, 1-2 parts of vulcanizing agent, 1-2 parts of accelerator, 1-2 parts of activator, 30-40 parts of plasticizer and 2-4 parts of foaming agent;

2. The preparation method of the antifreeze recycled concrete according to claim 1, characterized in that the waste foamed rubber powder is prepared by the following method: crushing waste rubber to obtain waste rubber particles;

adding the first-stage rubber compound, the accelerator, the vulcanizing agent and the foaming agent into an internal mixer, and continuing to roll for 3-5min after the internal mixing temperature is raised to 130-140 ℃ to obtain a second-stage rubber compound;

vulcanizing the two-stage rubber compound for 200-250s under the conditions that the temperature is 160-170 ℃ and the pressure is 6-8MPa to obtain vulcanized rubber;

and crushing and sieving the vulcanized rubber to obtain the waste foamed rubber powder.

3. The method for preparing the anti-freezing recycled concrete as claimed in claim 1, wherein the modified corncob meal is prepared by the following method: and putting the dried corncobs into the graphene oxide dispersion liquid, fully soaking, drying, crushing and sieving to obtain the modified corncob powder.

4. The method for preparing the antifreeze recycled concrete according to claim 1, wherein the fine aggregate consists of medium sand and coarse sand in a weight ratio of 1.

5. The method for preparing the antifreeze recycled concrete according to claim 1, wherein the admixture consists of fly ash and mineral powder in a weight ratio of 1.5-2.

6. The antifreeze recycled concrete prepared by the method for preparing the antifreeze recycled concrete according to claim 1.