CN114634344A

CN114634344A - Efficient green building material and preparation method thereof

Info

Publication number: CN114634344A
Application number: CN202210479099.2A
Authority: CN
Inventors: 刘玉曦; 刘波
Original assignee: Wuchang University of Technology
Current assignee: Wuchang University of Technology
Priority date: 2022-05-05
Filing date: 2022-05-05
Publication date: 2022-06-17

Abstract

The invention discloses a high-efficiency green building material which comprises the following raw materials in parts by weight: 150 portions of Portland cement, 150 portions of water, 200 portions of medium sand, 780 portions of medium sand, 800 portions of broken stone, 250 portions of concrete waste, 50-100 portions of fly ash, 200 portions of mineral powder, 4-5 portions of water reducing agent, 2-3 portions of retarder and 1-5 portions of coated double hydroxide. The added coated double hydroxide can effectively relieve corrosion and has certain self-repairing performance, so that the obtained concrete material has good corrosion resistance and better water permeability and frost resistance.

Description

Efficient green building material and preparation method thereof

Technical Field

The invention relates to the technical field of building materials, in particular to a high-efficiency green building material and a preparation method thereof.

Background

With the improvement of environmental protection awareness of people and the continuous increase of the demand of environmental protection products, environmental protection performance has become one of the main future trends of the development of various industries. The method is matched with the environmental protection property and is an important measure for realizing the industry development. Particularly in the civil engineering construction link, the demand of people for buildings is no longer limited to the maintenance of sustainable living properties, but rather tends to live in buildings with environmental protection properties, and the harmony of the living environment and the environmental protection work is expected to be realized. In short, when the modern building demanders the civil engineering construction process, the effect is related to the environmental friendliness, and the comprehensive quality of the building is determined by overall evaluation on the performances of the building on the aspects of environmental protection, energy conservation and the like. In the contents of building evaluation standards of related institutions, there are more and more parts including green building regulations, such as environmental protection and resource conservation, and the occupied proportion of the parts tends to increase significantly. Under the promotion of the concept of using green building materials, the green building material industry in China is vigorously developed, the use frequency and the proportion of the green building materials for civil engineering construction are increased more and more, personnel engaged in civil engineering are in the process of changing the theme of times, plans and modules are made in advance according to the concrete content of building construction, the use of the green building materials is merged into construction plans to the greatest extent, and the accuracy and the efficiency of civil engineering construction in China are fully realized by utilizing green building technology and the like. Constructors mostly adopt green building materials in the civil engineering construction process, can realize harmless influence of the construction process on the environment as much as possible, and reduce negative influence on the environment caused by civil engineering construction, thereby ensuring that the green building industry of China continuously makes progress.

The green, healthy and environment-friendly building material is also called ecological material, healthy material and the like, and is a novel environment-friendly material which is low in power consumption, free of radioactivity and free of pollution and is realized by reducing the use of energy and largely utilizing waste materials through a cleaning technology. The term "green" is not intended to mean green, but is an environmental and healthy symbol, which indicates that the material will not damage the environment, and can effectively promote ecological construction and protection of the environment. The green, healthy and environment-friendly building material is researched and developed through scientific research and novel technology, contains no radioactive elements, and is also focused on energy utilization in the manufacturing process, so that the energy consumption of the manufacturing process of the material is low, and the influence on the external environment is small, so that the material has the effects of energy conservation and emission reduction, and accords with related concepts such as ecological construction. The green, healthy and environment-friendly building material realizes the effects of environmental protection and energy conservation by using waste materials and adopting an advanced technology, and simultaneously realizes the effect of saving cost due to the simplicity of material taking.

In order to solve the problems of low water logging in low-hanging areas, underground water level reduction, urgent treatment of construction waste and the like caused by urban heat island effect and summer rainstorm, various performances of pervious concrete are deeply researched at home and abroad, and the construction waste is converted into recycled aggregate by optimizing the mixing proportion, and the recycled aggregate and the natural aggregate are mixed into the pervious concrete together to relieve the problems of urban construction waste recovery and environment. Several studies have shown that the hydration reaction between cement and water is not sufficiently performed during normal concrete mixing, and 20% of cement is used as inert filler and does not participate in the hydration reaction. The former is doped with a common water reducing agent to improve hydration collision between cement and water, but unhydrated cement particles cannot be distinguished; the latter researches the intensifier as the admixture, improves the activity of the cementing material and leads the hydration reaction to be basically and fully carried out. In order to reduce the use of building raw materials, make internal disorder or usurp people have used by-products and wastes of different industries as a substitute for concrete raw materials, but how to ensure the water permeability without losing the properties of the material such as compression resistance and light weight is a major concern. However, when the recycled waste is used, because a certain amount of hardened mud and the like can be contained in the recycled waste, when the recycled waste is exposed to humid air, a certain amount of chloride ions are contained in the recycled waste, and when the content of the chloride ions in the aggregate exceeds the standard, the concrete is expanded and fluffed, cracks and even cracks are generated, so that the durability and the corrosion resistance are weakened, and the compressive strength and the service life of the recycled waste are influenced.

Patent CN 113045272A discloses a green environment-friendly concrete and a preparation method thereof. The green environment-friendly concrete comprises the following components in parts by mass: 265 portions of cementing material and 285 portions; 900 portions of coarse aggregate and 1100 portions of coarse aggregate; 35-45 parts of nano silicon carbide; 25-30 parts of potassium borate; 20-25 parts of calcium chloride; water 160 and 175; the preparation method comprises the following steps: step 1) uniformly mixing coarse aggregate, nano silicon carbide, potassium borate and calcium chloride to obtain a mixture; step 2) uniformly mixing the mixture, the cementing material, the water reducing agent, the synergist and water to obtain green and environment-friendly concrete slurry; and 3) naturally curing the green environment-friendly concrete slurry at normal temperature to obtain the green environment-friendly concrete. The green concrete can permeate water into underground pipe network channels, improves the utilization rate of natural precipitation, is green, has better freeze-thaw resistance, and can keep good compressive strength.

Patent CN 111320438A discloses green environment-friendly concrete and a preparation method thereof, relates to the technical field of concrete, and solves the problem that the compressive strength of the recycled concrete waste material is greatly reduced in a long-time use process due to the existence of more micro cracks on the surface of the recycled concrete waste material. The green environment-friendly concrete comprises the following components in parts by weight: 180 portions and 220 portions of Portland cement; 170 portions of water and 180 portions of water; 740 and 760 portions of medium sand; 800-860 portions of broken stone; 210 portions and 240 portions of recycled concrete waste; 70-80 parts of fly ash; 190 portions of ore powder; 4-5 parts of a water reducing agent; 2-3 parts of a retarder; 8-12 parts of a filling reinforcing material; 10-16 parts of diatomite; 25-35 parts of urea; 8-10 parts of soybean seed coat powder. The green environment-friendly concrete has low carbonization speed in long-time application, and can keep good and stable compressive strength integrally.

In the prior art, the problem that the material is easy to corrode due to the fact that the content of chloride ions in recycled waste materials is high is not solved, so that the invention of the environment-friendly concrete material which is good in water permeability and not easy to corrode is necessary, and if the added corrosion inhibitor has a certain self-repairing capability, the service life of the material is further prolonged.

Disclosure of Invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to prepare an environment-friendly concrete material with good water permeability and corrosion resistance.

The technical scheme of the invention is as follows:

an efficient green building material is characterized in that: comprises the following components: portland cement, water, medium sand, broken stone, concrete waste, fly ash, mineral powder, a water reducing agent, a retarder and a coated layer-shaped double hydroxide.

Preferably, the efficient green building material comprises the following raw materials in parts by weight:

150 portions of Portland cement and 250 portions of Portland cement;

150 portions of water and 200 portions of water;

700 portions of medium sand and 780 portions of medium sand;

800 portions and 900 portions of broken stone;

200 portions and 250 portions of concrete waste;

50-100 parts of fly ash;

150 portions of mineral powder and 200 portions of mineral powder;

4-5 parts of a water reducing agent;

2-3 parts of a retarder;

1-5 parts of coated double hydroxide.

Further, the water reducing agent is any one of a naphthalene water reducing agent, a polycarboxylic acid water reducing agent and a molasses water reducing agent.

Further, the retarder is any one of sodium tripolyphosphate, sodium gluconate and sodium citrate.

Layered Double Hydroxides (LDHs), also known as hydrotalcites, have a three-dimensional crystal structure formed by longitudinally and orderly extending nanoscale octahedral two-dimensional laminates, wherein the laminates are composed of divalent and trivalent metal hydroxides, anions between the laminates are used for making up the charge balance of the laminates, and the layered double hydroxides are connected with a main laminate in the modes of electrostatic attraction, hydrogen bonds or ionic bonds, so that the layered double hydroxides integrally show electric neutrality. The LDHs has a regular two-dimensional layered structure, can release corrosion inhibitor anions through the exchange effect of interlayer anions, and can be used as an inorganic coating main body or an organic coating filler, so that the permeation path of a corrosive medium in the coating can be prolonged, the barrier property of the coating is improved, and the coating can obtain corrosion inhibition capability. In addition, a large number of hydroxyl groups on the surface of the LDHs enable the LDHs to have coating compatibility which cannot be compared with other inorganic fillers, the preparation process is simple, the cost is low, and the LDHs have conversion conditions of industrial production.

The technical idea of the LDHs in the anti-corrosion application of the coating is as follows: firstly, a load corrosion inhibitor is used as a nano load container of the corrosion inhibitor through the ion exchange performance of LDHs, and the nano load container is doped into organic resins such as epoxy resin, polyurethane and the like to realize corrosion prevention; secondly, an LDH film is directly grown on the surface of the alloy to provide an anti-corrosion effect; and thirdly, growing LDHs materials on pores and surfaces of oxide films on the surfaces of the alloys to fill up the defects of the oxide films and generate a synergistic anticorrosion effect. However, as water, oxygen and chloride ions invade, the coating can start to generate micropores and cracks to accelerate the corrosion of the material, so that the improvement of the durability of the LDH to have certain self-repairing capability can help the corrosion inhibitor to play a role for a longer time.

The coated layered double hydroxide is prepared by the following method:

s1, adding magnesium nitrate and silver nitrate into water, and uniformly mixing to obtain a solution A;

s2, adding sodium nitrate and sodium hydroxide into water, and uniformly mixing to obtain a solution B;

s3, mixing the solution A and the solution B, heating to 60-70 ℃, stirring for 5-8 hours, transferring the mixed solution, and carrying out hydrothermal reaction at 120-130 ℃;

after the reaction of S4 is finished, filtering, washing with water, and drying a filter cake to obtain Mg-Al layered double hydroxide;

s5, adding the Mg-Al layered double hydroxide and benzotriazole obtained in the step S4 into water, stirring for 1-2 h when the pH is 9-10, washing a filter cake to be neutral after filtering, and adding the filter cake into the water to obtain a solution X;

s6, mixing the solution X with a copper sulfate aqueous solution, stirring for 5-10 min, filtering, washing a filter cake with water, centrifuging the filter cake to remove supernatant, and drying to obtain the coated layered double hydroxide.

Preferably, the method for preparing the coated double hydroxide comprises the following steps:

s1 adding 25-30 parts by weight of Mg (NO) into 200-250 parts by weight of water₃)₂·6H₂18 to 20 parts by weight of Al (NO)₃)₃·9H₂O, mixing uniformly to obtain a solution A;

s2 NaNO is taken in 15-20 parts by weight₃Adding 10-12 parts by weight of NaOH into 200-250 parts by weight of water, and uniformly mixing to obtain a solution B;

s3, mixing the solution A and the solution B, heating to 60-70 ℃, stirring for 5-8 h, transferring the mixed solution, and carrying out hydrothermal reaction at 120-130 ℃ for 20-24 h;

after the reaction of S4 is finished, filtering, washing with 50-60 parts by weight of water, and drying a filter cake at 80-90 ℃ for 24-28 h to obtain Mg-Al layered double hydroxide;

s5, weighing 5-8 parts by weight of Mg-Al layered double hydroxide and 2.5-4 parts by weight of benzotriazole in the step S4, adding the Mg-Al layered double hydroxide and the benzotriazole into 500-800 parts by weight of water, adjusting the pH to 9-10 by using 0.5-1 mol/L NaOH solution, stirring for 1-2 hours, washing a filter cake to be neutral by using water after filtering, and adding the filter cake into 500-600 parts by weight of water to obtain a solution X;

s6 weighing 12-15 parts by weight of CuSO₄Adding the solution X and the solution Y into 500-600 parts by weight of water to obtain a solution Y, mixing the solution X and the solution Y, stirring for 5-10 min, filtering, washing a filter cake with 50-60 parts by weight of water, centrifuging the filter cake at 4000-4500 rpm for 5-10 min to remove a supernatant, and drying at 80-90 ℃ for 24-28 h to obtain the coated layered double hydroxide.

The invention also provides a preparation method of the efficient green building material, which comprises the following steps:

s1, stirring the crushed stone, the medium sand, the fly ash, the portland cement, the mineral powder, the concrete waste and the coated double hydroxide for 30-40 min at 80-120 ℃ and 600-900 rpm, cooling, and continuously stirring and mixing for 10-20 min to obtain a mixture;

s2, stirring water, a water reducing agent and a retarder in a stirring barrel at a speed of 300-600 rpm for 10-15 min to obtain a mixed solution;

s3, pouring the mixture obtained in the step S1 into the mixed liquid obtained in the step S2 in batches, stirring and pouring the mixture while stirring, wherein the stirring speed is controlled to be 1000-1200 rpm, and stirring is carried out for 15-20 min, so that the efficient green building material is obtained.

Compared with the prior art, the invention has the beneficial effects that:

(1) the layered double hydroxide is adopted for ion exchange, so that the anion of the corrosion inhibitor can be released and chloride ions can be adsorbed, and the concrete material can be well protected from being corroded;

(2) the Cu/BTA (benzotriazole) composite material is adopted for coating, when hydroxyl on the surface of the layered double hydroxide is oxidized to generate hydroxyl ions, the pH value of the surface is locally reduced, the composite can be decomposed, the BTA is released and adsorbed on the surface of the material to exert the corrosion inhibition performance of the BTA, and the corroded area is repaired;

(3) the prepared concrete material has good water permeability and good frost resistance, and is suitable for being used under outdoor conditions and the like.

Detailed Description

Hereinafter, the technical solution of the present invention will be described in detail by specific examples, but these examples should be explicitly proposed for illustration, but should not be construed as limiting the scope of the present invention.

The parameters of part of the raw materials in the embodiment of the invention are as follows:

p.o22.5 ordinary portland cement, fineness of cement: 3%, initial setting time: 2.5h, Lingshou county, Yuantong mineral products trade, Inc.

Polycarboxylate water reducing agent dry powder, solid content: 98 ± 1%, pH: 7-9, Shandong bock chemical Co., Ltd.

Comparative example 1

The preparation of the high-efficiency green building material comprises the following steps:

s1, mixing 800g of broken stone, 750g of medium sand, 80g of fly ash, 200g of portland cement, 180g of mineral powder, 220g of concrete waste and 4g of layered double hydroxide, stirring at 100 ℃ and 900rpm for 30min, cooling, and continuing to stir and mix for 20min to obtain a mixture;

s2, uniformly mixing 200g of water, 5g of polycarboxylic acid water reducing agent and 3g of sodium tripolyphosphate in a stirring barrel, and stirring at 600rpm for 15min to obtain a mixed solution;

s3, pouring the mixture obtained in the step S1 into the mixed solution in batches, stirring while pouring, and stirring at 1200rpm for 20min to obtain the efficient green building material.

The preparation method of the layered double hydroxide comprises the following steps:

s1 taking 200g of deionized water, adding 25g of Mg (NO)₃)₂·6H₂O，18gAl(NO₃)₃·9H₂O, mixing uniformly to obtain a solution A;

s2 taking 17g NaNO₃Adding 12g of NaOH into 200g of deionized water, and uniformly mixing to obtain a solution B;

s3, mixing the solution A and the solution B, heating to 70 ℃, stirring for 5 hours, transferring the mixed solution, and carrying out hydrothermal reaction for 24 hours at 120 ℃;

and after the reaction of S4 is finished, filtering, taking a filter cake, washing the filter cake with 50g of deionized water, and drying the filter cake at 80 ℃ for 24 hours to obtain the Mg-Al layered double hydroxide.

Example 1

s1, mixing 800g of broken stone, 750g of medium sand, 80g of fly ash, 200g of portland cement, 180g of mineral powder, 220g of concrete waste and 4g of coated layered double hydroxide, stirring at 100 ℃ and 900rpm for 30min, cooling, and continuously stirring and mixing for 20min to obtain a mixture;

The preparation method of the coated double hydroxide comprises the following steps:

after the reaction of S4, filtering, taking a filter cake, washing the filter cake with 50g of deionized water, and drying the filter cake at 80 ℃ for 24 hours to obtain Mg-Al layered double hydroxide;

s5, weighing 5g of Mg-Al layered double hydroxide and 2.5g of benzotriazole in the step S4, adding the Mg-Al layered double hydroxide and the benzotriazole into 500g of water, adjusting the pH to 9 by using 1mol/L NaOH solution, stirring for 1h, filtering, washing a filter cake to be neutral by using water, and adding the filter cake into 500g of water to obtain a solution X;

s6 weighing 12g of CuSO₄Adding into 500g water to obtain solution Y, mixing solution X and Y, stirring for 10min, filtering, washing the filter cake with 50g water, centrifuging the filter cake at 4000rpm for 5min to remove supernatant, and drying at 80 deg.C for 24h to obtain coated layered double hydroxide.

Example 2

s1, mixing 800g of broken stone, 750g of medium sand, 80g of fly ash, 200g of portland cement, 180g of mineral powder and 220g of concrete waste, stirring at 100 ℃ and 900rpm for 30min, cooling, and continuously stirring and mixing for 20min to obtain a mixture;

Example 3

s1, mixing 800g of broken stone, 750g of medium sand, 80g of fly ash, 200g of portland cement, 180g of mineral powder, 220g of concrete waste and 4g of coated modified layered double hydroxide, stirring for 30min at 100 ℃, 900rpm, cooling, and continuing to stir and mix for 20min to obtain a mixture;

A process for the preparation of a coated modified layered double hydroxide comprising the steps of:

s2 taking 17g NaNO₃Adding 12g of NaOH and 1g of sodium lignosulfonate into 200g of deionized water, and uniformly mixing to obtain a solution B;

after the reaction of S4 is finished, filtering, washing with 50g of deionized water, and drying a filter cake for 24 hours at 80 ℃ to obtain modified Mg-Al layered double hydroxide;

s5, weighing 5g of Mg-Al layered double hydroxide modified in the step S4 and 2.5g of benzotriazole, adding the Mg-Al layered double hydroxide and the benzotriazole into 500g of water, adjusting the pH to 9 with 1mol/L NaOH solution, stirring for 1h, filtering, washing a filter cake with water to be neutral, and adding the filter cake into 500g of water to obtain a solution X;

s6 weighing 12g of CuSO₄Adding into 500g water to obtain solution Y, mixing solution X and Y, stirring for 10min, filtering, washing the filter cake with 50g water, centrifuging the filter cake at 4000rpm for 5min to remove supernatant, and drying at 80 deg.C for 24h to obtain coated modified layered double hydroxide.

Test example 1

The water permeability of the comparative examples and the examples is tested, 4 samples are prepared, the mixed concrete mixture is mixed back and forth three times by a shovel, the concrete mixture is loaded into a test mold once, a spatula is inserted and tamped along the wall of each test mold during loading, the concrete mixture is enabled to be higher than the opening of the test mold, the test mold is fixed on a vibrating table, and the vibration is continued until the surface is discharged. Each set of test specimens was 100mm by 150mm in size. According to the technical specification of permeable cement concrete pavement of the industrial standard CJ/T135-2009, the periphery of a sample is sealed before a test, only water is allowed to permeate from the upper surface to the lower surface of the sample, the sample is placed into a water permeability instrument and injected with water, the water level in the sample is maintained to be about 150mm, when the water outflow amount of the sample and the water outflow amount of the sample are consistent, the water outflow amount of an overflow water tank within 5min is recorded, the steps are repeated for three times, the average value is taken, and the water permeability coefficient is calculated according to the following formula:

K＝Qh/SHt

K-Permeability coefficient of sample (mm/s)

Q-is the amount of water (mm) that exudes in t seconds³)

h-height of sample (mm)

S-Upper surface area of sample (mm)²)

H-water head difference (mm)

t-time(s)

TABLE 1 Permeability coefficient test results table

Experimental protocol	Coefficient of water permeability (mm/s)
		Comparative example 1	7.56
Example 1	9.31
		Example 2	5.45
Example 3	10.64

From the results, it can be seen that the water permeability of the material can be enhanced by adding the layered double hydroxide, probably because the layered double hydroxide is dispersed in the material to form a good skeleton structure, which can accelerate the permeation of moisture, and in example 3, the layered double hydroxide is modified by adding sodium lignosulfonate, so that the communication pores and the semi-closed pores inside the concrete are more perfect, and the water permeability of the concrete is further improved.

Test example 2

The salt spray test is carried out on the comparative example and the embodiment, then the content of chloride ions is detected, 4 samples are prepared, the mixed concrete mixture is mixed back and forth three times by using a shovel, the concrete mixture is loaded into a test mold once, a spatula is used for inserting and tamping along the wall of each test mold during loading, the concrete mixture is enabled to be higher than the opening of the test mold, the test mold is fixed on a vibration table, and vibration is continued until the surface is discharged. Each set of test specimens was 100mm by 150mm in size. 1.5 wt% NaCl solution was prepared and sprayed continuously into the closed space where the sample was placed, and exposed to salt spray for 200 h. Manually coarsely crushing a sample, drying, crushing, taking NaCl solutions with different concentrations to activate and calibrate an electrode, weighing 1g of powder, adding 100mL of distilled water and 2mL of 5mol/L NaNO₃The solution is stirred and then the electrodes are placed in the solution, the average value of each group of measurement is obtained, the standard content of the chloride ions and the data in GB/50164-.

Table 2 table of chloride ion test results

Experimental protocol	Chloride ion content (. times.10)^-2mol/L)
		Comparative example 1	0.039
Example 1	0.031
		Example 2	0.050
Example 3	0.024

The common silicate cement is added with a little chloride salt in the calcining process, so that the common silicate cement contains chloride ions, the recycled aggregate mainly comprises waste concrete, the waste concrete contains a certain amount of hardened cement paste, and the recycled aggregate is exposed in humid air for a long time and contains a certain amount of chloride ions; the mixing water also contains a large amount of chloride ions, because many water is disinfected by hypochlorous acid in the purification process, so that the mixing water contains a large amount of chloride ions. When the content of the chloride ions exceeds the standard, the concrete can be expanded and fluffy, so that cracks and even cracks are generated, and therefore, the defect is often improved by adding a corrosion inhibitor. However, when corrosion continues to occur, typical corrosion inhibitors tend to fail due to the long-term attack of the chloride ions that continue to enter the cracks. In example 1, when the concrete material is corroded, hydroxyl on the surface of the layered double hydroxide is oxidized to generate hydroxyl ions, so that the pH value of the surface is locally reduced, under the condition, a Cu/BTA (benzotriazole) compound coated on the surface of the layered double hydroxide is decomposed, the BTA is released and adsorbed on the surface of the material to exert the corrosion inhibition performance, and the corroded area is repaired, so that the corrosion of the material by chlorine ions and the like is inhibited. In example 3, the specific surface area of the layered double hydroxide is increased by adding sodium lignosulfonate, so that the binding capacity with chloride ions and the surface adsorption performance of the layered double hydroxide are improved, the concentration of external corrosion ions is successfully reduced after the corrosion ions are adsorbed, and after a Cu/BTA (benzotriazole) compound on the surface of the layered double hydroxide is decomposed, the adsorption of BTA can protect the surface, so that the corrosion resistance is further improved.

Test example 3

The frost resistance is an index which can show that the material can still keep the original performance after multiple freeze-thaw tests without being damaged, and the durability of the concrete can be fully verified. The freeze-thaw damage that occurs when concrete is subjected to cold weather conditions has always been a significant problem affecting its performance. In cold areas, the pervious concrete is easy to expand when being frozen, the volume and the mass of the pervious concrete are changed, the performance of the pervious concrete is greatly influenced, and even the pervious concrete is cracked, so that the service performance of the pervious concrete is greatly weakened. Preparing 4 samples, mixing the mixed concrete mixture by using a shovel for three times, loading the concrete mixture into a test mold once, inserting and smashing the concrete mixture along the wall of each test mold by using a spatula during loading so that the concrete mixture is higher than the opening of each test mold, fixing the test mold on a vibrating table, and continuously vibrating until the surface is pulped. Each set of test specimens was 100mm by 150mm in size. The test method and the standard refer to an industry standard CJJ/T135-2009 technical Specification for pervious concrete pavements. And (3) soaking the sample in water for 3h, weighing, freezing for 3h, soaking in water for 3h, weighing, repeatedly freezing and thawing for 25 cycles in this way, and calculating the mass loss rate, wherein the mass loss rate is up to the standard if the mass loss rate is less than or equal to 5% after 25 freezing and thawing cycles.

TABLE 3 Frost resistance test results Table

Experimental protocol	Mass loss rate (%)
		Comparative example 1	4.1
Example 1	3.5
		Example 2	4.8
Example 3	3.4

The results show that the prepared sample can reach the anti-freezing standard specified in the industry, because the layered double hydroxide is dispersed in the concrete material to form a good framework structure, the moisture permeation is facilitated, the layered double hydroxide is not easy to store in the material, and the material cannot be damaged due to the volume expansion of the frozen and melted water.

Claims

1. An efficient green building material is characterized in that: comprises the following components: portland cement, water, medium sand, broken stone, concrete waste, fly ash, mineral powder, a water reducing agent, a retarder and a coated layer-shaped double hydroxide.

2. The efficient green building material of claim 1, comprising the following components in parts by weight: 150 portions of Portland cement, 150 portions of water, 200 portions of medium sand, 780 portions of medium sand, 800 portions of broken stone, 250 portions of concrete waste, 50-100 portions of fly ash, 200 portions of mineral powder, 4-5 portions of water reducing agent, 2-3 portions of retarder and 1-5 portions of coated double hydroxide.

3. The high-efficiency green building material according to claim 1 or 2, wherein the coated layered double hydroxide is prepared by the following method:

s4, after the reaction is finished, filtering, washing with water, and drying a filter cake to obtain Mg-Al layered double hydroxide;

4. The high efficiency green building material of claim 3, wherein said coated layered double hydroxide is prepared by the following method:

s1 weighing 200-250 parts by weight of water, and adding 25-30 parts by weight of Mg (NO)₃)₂·6H₂O, 18 to 20 parts by weight of Al (NO)₃)₃·9H₂O, mixing uniformly to obtain a solution A;

s2 weighing 15-20 parts by weight of NaNO₃Adding 10-12 parts by weight of NaOH into 200-250 parts by weight of water, and uniformly mixing to obtain a solution B;

s5, weighing 5-8 parts by weight of Mg-Al layered double hydroxide in the step S4 and 2.5-4 parts by weight of benzotriazole, adding the Mg-Al layered double hydroxide and the benzotriazole into 500-800 parts by weight of water, adjusting the pH to 9-10 by using 0.5-1 mol/L NaOH solution, stirring for 1-2 hours, washing a filter cake to be neutral by using water after filtering, and adding the filter cake into 500-600 parts by weight of water to obtain a solution X;

s6 weighing 12-15 parts by weight of CuSO₄Adding the solution X and the Y into 500-600 parts by weight of water to obtain a solution Y, mixing the solution X and the Y, stirring for 5-10 min, filtering, taking a filter cake, washing the filter cake with 50-60 parts by weight of water, centrifuging the filter cake at 4000-4500 rpm for 5-10 min to remove a supernatant, and drying at 80-90 ℃ for 24-28 h to obtain the coated layered double hydroxide.

5. The high efficiency green building material of claim 4, wherein: and the hydrothermal reaction time in the step S3 is 20-24 h.

6. A high efficiency green building material as claimed in claim 1 or 2, wherein: the water reducing agent is any one of a naphthalene water reducing agent, a polycarboxylic acid water reducing agent and a molasses water reducing agent.

7. A high efficiency green building material as claimed in claim 1 or 2, wherein: the retarder is any one of sodium tripolyphosphate, sodium gluconate and sodium citrate.

8. The method for preparing high efficiency green building material according to any one of claims 1 to 7, comprising the steps of:

s1, stirring the broken stone, the medium sand, the fly ash, the portland cement, the mineral powder, the concrete waste and the coated double hydroxide at 80-120 ℃ and 600-900 rpm for 30-40 min, cooling, and continuously stirring and mixing for 10-20 min to obtain a mixture;