Waste concrete recycled micro-powder activating agent as well as preparation method and application thereof

Abstract

The invention discloses a waste concrete regenerated micro-powder activating agent and a preparation method and application thereof, and belongs to the technical field of cement-based material admixtures, and the regenerated micro-powder activating agent comprises polyether side chain modified polyethylene polyamine organic activated molecules and nano silicon dioxide. According to the waste concrete regenerated micro-powder activating agent disclosed by the invention, the dissolution-crystallization process of the regenerated micro-powder in a cement-based material system can be effectively improved through the adsorption effect of specific functional groups in the organic activated molecules on the surface of the regenerated micro-powder, and a mineral phase beneficial to a microstructure is formed through induction, so that the utilization efficiency and quality of the regenerated micro-powder are improved. Compared with a single-component organic activated molecule, the organic molecule-nano particle hybrid activating agent has better activating efficiency on the regenerated micro powder, and the performance of the regenerated micro powder mortar / concrete is improved more obviously.

Description

Technical Field

[0001] The invention belongs to the technical field of cement-based material admixtures, and in particular relates to a waste concrete recycled micro-powder activator and a preparation method and application thereof. Background Art

[0002] Waste concrete refers to the concrete blocks discarded after the disintegration of buildings. The amount of waste concrete generated in my country has increased year by year. The traditional treatment method is mainly landfill, which not only occupies a large amount of land, but also affects the ecological environment. Based on this, the high-quality concrete blocks and sand powder after crushing and screening can be used as recycled coarse / fine aggregates for concrete respectively, and a large amount of micropowder can be used as the raw material of recycled adhesive. The concrete prepared with recycled aggregate and recycled adhesive can enter the next cycle, and achieve zero waste emissions in the entire cycle. However, in the past, the recycling of waste concrete focused on recycled aggregates, while about 30~40% of waste concrete micropowder was not effectively utilized due to its low quality. Therefore, making full use of waste concrete micropowder is not only a need for environmental protection and low emissions, but also can alleviate the problem of the increasing scarcity of mineral admixture resources in my country, which has important practical significance.

[0003] Different from ordinary cement and mineral admixtures, recycled micropowder has low activity and strong adsorption. When added as a cementitious material, it is easy to interact with other cementitious components during the hydration process, thus affecting the hydration hardening, mechanical properties and durability of recycled micropowder mortar / concrete. In addition, the adsorption and chemical reaction between recycled micropowder and chemical admixtures (such as water reducers, thickeners, etc.) are the key to affecting the working performance of recycled micropowder mortar / concrete. Therefore, the development of efficient solubilization and activation technology for recycled micropowder is a major scientific issue to achieve the performance improvement of recycled micropowder mortar / concrete.

[0004] Patent applications CN115569687A, CN115745531A, CN114507050A, CN112876145A, etc. respectively mentioned the preparation method and application of concrete blocks and sand powder after crushing and screening of waste concrete as recycled coarse / fine aggregates, while there are few reports on the use of fine powder produced by waste concrete as recycled adhesive; Patent applications CN109320162A and CN113788638A reported the preparation of recycled fine powder and its application in concrete, but the recycled fine powder lacked efficient activation means, which affected the performance of concrete. The addition of functional chemical admixtures can effectively improve the performance of cement / concrete. Compared with pure organic admixtures, organic-inorganic hybrid admixtures with nano-silica as organic molecule carriers (Construction and Building Materials, 2023, 362, 129739; Materials, 2022, 15, 7993) have a better effect on improving the performance of mortar / concrete. Therefore, through molecular design, the development of recycled micropowder activators hybridizing nano-silica and organic molecules is expected to have a better activation effect on recycled micropowders of waste concrete, but research in this area has not been reported yet. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a waste concrete recycled micropowder activator and a preparation method and application thereof, which has better activation efficiency for recycled micropowder and more obvious performance improvement for recycled micropowder mortar / concrete.

[0006] The present invention is achieved through the following technical solutions: A waste concrete regeneration micro-powder activator comprises a polyether side chain modified polyethylene polyamine organic activating molecule and nano silicon dioxide; the structural formula of the polyether side chain modified polyethylene polyamine organic activating molecule is shown in general formula I: Formula I; In the general formula I, m is a natural number from 1 to 5, and n is a natural number from 5 to 20.

[0007] Preferably, the nano-silica is prepared by a sol-gel method, with ammonia water as solvent and tetraethoxysilane as silicon source; wherein the mass ratio of the polyether side chain modified polyethylene polyamine organic activated molecule, ammonia water and tetraethoxysilane is (5-15):1:2.

[0008] Preferably, the average particle size of the regenerated micropowder activator is 100-200 nm.

[0009] The method for preparing the above-mentioned waste concrete recycled micro-powder activator comprises the following steps: Step 1) introducing ethylene oxide into polyethylene polyamine under the action of a catalyst for 1 to 3 hours to obtain an organic activated polyethylene polyamine molecule modified with a polyether side chain; Step 2) Stir and mix the polyether side chain modified polyethylene polyamine organic activated molecules and ammonia water at 30-40°C, slowly add tetraethoxysilane and continue stirring at 30-40°C for 5-10 hours; filter the obtained solid and wash it with a small amount of anhydrous ethanol, and vacuum dry it to obtain the product.

[0010] Preferably, the temperature of introducing ethylene oxide in step 1) is 120-140°C.

[0011] Preferably, the catalyst in step 1) is sodium hydride, sodium methoxide or sodium tert-butoxide.

[0012] Preferably, the structural formula of the polyethylene polyamine in step 1) is as shown in general formula II: Formula II; In the general formula II: m is a natural number from 1 to 5; The molar ratio of the polyethylene polyamine, the catalyst and the ethylene oxide is 1:[0.01(2+m)~0.1(2+m)]:[5(2+m)~20(2+m)].

[0013] Preferably, the concentration of the ammonia water in step 2) is 28%.

[0014] The above-mentioned waste concrete recycled micropowder activator, or the waste concrete recycled micropowder activator prepared by the above-mentioned preparation method is used in the activation treatment of waste concrete recycled micropowder.

[0015] Preferably, the activator and the recycled fine powder obtained by crushing, removing impurities and grinding the waste concrete are fully mixed in a mass ratio of (0.2~2):100.

[0016] The beneficial effects of the present invention are as follows: The waste concrete regenerated micropowder activator of the present invention, from the perspective of chemical structure, adopts an organic-inorganic hybridization method, firstly introduces a polyether side chain into the molecular structure of polyethylene polyamine to obtain an organic activating molecule, and then uses nano-silicon dioxide as a carrier of the organic activating molecule to obtain an organic molecule-nanoparticle hybrid activator. Among them, the adsorption effect of specific functional groups in the organic activating molecules on the surface of the regenerated micropowder can effectively improve the dissolution-crystallization process of the regenerated micropowder in the cement-based material system, induce the formation of a mineral phase that is beneficial to the microstructure, thereby improving the utilization efficiency and quality of the regenerated micropowder. Compared with single-component organic activating molecules, the organic molecule-nanoparticle hybrid activator of the present invention has better activation efficiency for the regenerated micropowder, and the performance improvement of the regenerated micropowder mortar / concrete is also more obvious. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to specific embodiments.

[0018] The materials used in the following examples are all commercially available chemicals, among which all reagents (chemically pure) used in the synthesis of waste concrete recycled micropowder activator are purchased from Anage Technology Co., Ltd. and Sinopharm Chemical Reagent Co., Ltd., and polycarboxylic acid water reducer, air entraining agent, water retention agent, and retarder are all from Jiangsu Subote New Materials Co., Ltd. The active recycled micropowder used is the recycled micropowder obtained by crushing, removing impurities, and grinding the waste concrete (strength grade C50) obtained by demolishing a building at a construction site in Nanjing, which meets the technical indicators of Class II recycled micropowder in the industry standard JG / T 573-2020 "Recycled Micropowder for Concrete and Mortar".

[0019] A waste concrete regeneration micro-powder activator comprises polyether side chain modified polyethylene polyamine organic activation molecules and nano silicon dioxide.

[0020] The structure of the polyether side chain modified polyethylene polyamine organic activated molecule conforms to the general formula I:

[0021] Formula I In the general formula I: m is a natural number from 1 to 5, and n is a natural number from 5 to 20 (the same below).

[0022] The nano-silica is prepared by a sol-gel method, with ammonia water as solvent and tetraethoxysilane as silicon source; wherein the mass ratio of the polyether side chain modified polyethylene polyamine organic activated molecule, ammonia water and tetraethoxysilane is (5-15):1:2.

[0023] A method for preparing a waste concrete recycled micro-powder activator, the specific steps are as follows: (1) Polyethylene polyamine and a catalyst are placed in a high-pressure reactor, and ethylene oxide is introduced at 120-140°C for 1-3 hours to obtain an organic activated molecule of polyethylene polyamine modified with a polyether side chain.

[0024] The structure of the polyethylene polyamine conforms to the general formula II:

[0025] Formula II The reaction formula of the above reaction is shown in Reaction Formula III:

[0026] Reaction formula III The catalyst is sodium hydride, sodium methoxide or sodium tert-butoxide; the molar ratio of the polyethylene polyamine, the catalyst and ethylene oxide is 1:[0.01(2+m)~0.1(2+m)]:[5(2+m)~20(2+m)].

[0027] (2) Nano-silica is prepared by the sol-gel method known in the art. The above-mentioned organic activated molecules are used as template reagents and tetraethoxysilane (TEOS) is used as a silicon source under alkaline conditions. Specifically, the polyether side chain-modified polyethylene polyamine organic activated molecules are stirred and mixed with 28% ammonia water at 30-40°C, TEOS is slowly added and stirred continuously at 30-40°C for 5-10 hours; the obtained solid is filtered and washed with a small amount of anhydrous ethanol, and then vacuum dried to obtain the waste concrete recycled micro-powder activator.

[0028] Example 1 A method for preparing a waste concrete recycled micro-powder activator, the specific steps are as follows: (1) Place 10 mmol of diethylenetriamine and 0.3 mmol of sodium hydride in a high-pressure reactor, introduce 150 mmol of ethylene oxide at 120°C, and react for 1 h to obtain an organic activated molecule.

[0029] (2) 50 g of organic activated molecules and 10 g of 28% ammonia water were stirred at 30°C, and 20 g of TEOS was slowly added and stirred at 30°C for 5 h. The obtained solid was filtered and washed with a small amount of anhydrous ethanol, and then vacuum dried to obtain a regenerated micropowder activator (in Formula I, m=1, n=5) with an average particle size of 120 nm.

[0030] Example 2 A method for preparing a waste concrete recycled micro-powder activator, the specific steps are as follows: (1) Place 10 mmol of tetraethylenepentamine and 2.5 mmol of sodium methoxide in a high-pressure reactor, introduce 500 mmol of ethylene oxide at 130°C, and react for 2 h to obtain an organic activated molecule.

[0031] (2) 100 g of organic activated molecules and 10 g of 28% ammonia water were stirred at 35°C, and 20 g of TEOS was slowly added and stirred at 35°C for 7 h. The obtained solid was filtered and washed with a small amount of anhydrous ethanol, and then vacuum dried to obtain a regenerated micropowder activator (in Formula I, m=3, n=10) with an average particle size of 160 nm.

[0032] Example 3 A method for preparing a waste concrete recycled micro-powder activator, the specific steps are as follows: (1) Place 10 mmol of hexaethyleneheptamine and 7 mmol of sodium tert-butoxide in a high-pressure reactor, introduce 1400 mmol of ethylene oxide at 140°C, and react for 3 h to obtain an organic activated molecule.

[0033] (2) 150 g of organic activated molecules and 10 g of 28% ammonia water were stirred at 40°C, and 20 g of TEOS was slowly added and stirred at 40°C for 10 h. The obtained solid was filtered and washed with a small amount of anhydrous ethanol, and then vacuum dried to obtain a regenerated micropowder activator (in Formula I, m=5, n=20) with an average particle size of 170 nm.

[0034] Comparative Example 1 The organic activated molecule in Example 3 is directly used as a regenerated micropowder activator (in Formula I, m=5, n=0, and does not contain nano-silicon dioxide).

[0035] Comparative Example 2 Commercially available nano-silica particles, with an average particle size of 150-200 nm, are directly used as regeneration micropowder activators.

[0036] Test Example 1 Preparation and evaluation of premixed (dry mix) mortar using active regenerated micropowder The mortar mix ratio is: 89 g of Conch 52.5 RP II cement, 30 g of fly ash, 51 g of activated regenerated micropowder (containing 0.5% of regenerated micropowder activator and activated), 820 g of river sand (fineness modulus Mx=2.6), and 150 g of water.

[0037] The admixture formula is: 35 g air entraining agent, 105 g water retaining agent, 60 g retarder, and 800 g fly ash.

[0038] Mix the above powders evenly and add 1 g of them in the mortar. Mix the dry mortar and admixture for 30 seconds, then add water and stir slowly for 90 seconds. According to the relevant provisions of the national standard GB / T 25181-2019 "Premixed Mortar", the various index data of the premixed mortar were tested.

[0039] The regenerated micro-powder activators tested were Examples 1-3 and the five regenerated micro-powder activator samples prepared in Comparative Examples 1 and 2. The experimental results are shown in Table 1.

[0040] Table 1 Comparison of performance of different recycled micro powder activators in premixed (dry mix) mortar

[0041] As can be seen from Table 1, compared with the blank sample (original mortar) without the regenerated micropowder activator (the regenerated micropowder is not activated), the three samples to which the regenerated micropowder activator prepared by Examples 1-3 is added have stable bulk density and consistency data, slightly increased water retention data, and significantly increased 28-day compressive strength, which are 37.5%, 47.9% and 63.5% higher than the blank sample, respectively. This shows that the regenerated micropowder activator of the present invention has a good activation efficiency for the regenerated micropowder, and significantly improves the performance of the regenerated micropowder mortar. Compared with Comparative Example 1 (a single organic active molecule, not hybridized with nano-silicon dioxide) and Comparative Example 2 (a single nano-silicon dioxide), the regenerated micropowder activator prepared by Examples 1-3 can further improve the compressive strength of the mortar, indicating that the present invention has a higher activation efficiency for the regenerated micropowder than the conventional single-component organic activator, and the performance improvement of the regenerated micropowder mortar is also more obvious.

[0042] Test Example 2 Preparation and evaluation of concrete using active recycled micropowder The concrete mix ratio is: 3.3 kg of Conch 52.5 RP II cement, 0.4 kg of fly ash, 1.6 kg of activated regenerated micropowder (containing 0.8% of regenerated micropowder activator and activated), 11.0 kg of river sand (fineness modulus Mx=2.6), 11.55 kg of large stone (particle size 10~25 mm), 4.95 kg of small stone (particle size 5~10 mm), and 2.5 kg of water.

[0043] The admixture formula is: polycarboxylic acid water-reducing agent with a solid content of 20%, the dosage is 52.5 g; water-retaining agent with a solid content of 3%, the dosage is 7.5 g.

[0044] Referring to the relevant provisions of the national standard GB / T 8076-2008 "Concrete Admixtures" and GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the slump / expansion and compressive strength of concrete were tested respectively.

[0045] The regenerated micro-powder activators tested were Examples 1-3 and the five regenerated micro-powder activator samples prepared in Comparative Examples 1-2. The experimental results are shown in Table 2.

[0046] Table 2 Comparison of performance of different recycled micro powder activators in concrete

[0047] As can be seen from Table 2, compared with the blank sample (original concrete) without the addition of the regenerated micropowder activator (the regenerated micropowder is not activated), the slump / spread data of the three samples to which the regenerated micropowder activator prepared by Examples 1-3 is added remain stable, and the 28-day compressive strength is significantly increased, which is 21.0%, 36.9% and 40.9% higher than the blank sample, respectively. This shows that the regenerated micropowder activator of the present invention has a good activation efficiency for the regenerated micropowder, and has a significant improvement in the performance of the regenerated micropowder concrete. Compared with Comparative Example 1 (a single organic active molecule, not hybridized with nano-silicon dioxide) and Comparative Example 2 (a single nano-silicon dioxide), the regenerated micropowder activator prepared by Examples 1-3 can further improve the compressive strength of the concrete, indicating that the present invention has a better activation efficiency for the regenerated micropowder than the conventional single-component organic activator, and the performance improvement of the regenerated micropowder concrete is also more obvious.

[0048] In summary, the regenerated micropowder activator of the present invention has a good activation efficiency for waste concrete regenerated micropowder and significantly improves the performance of regenerated micropowder mortar / concrete.

[0049] The embodiments described above are only some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. The scope of protection of the present invention shall be subject to the scope required by the claims. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work shall fall within the scope of protection of the present invention.

Claims

1. A waste concrete recycled micro powder activator, characterized in that: It comprises polyether side chain modified polyethylene polyamine organic activated molecules and nano silicon dioxide; the structural formula of the polyether side chain modified polyethylene polyamine organic activated molecules is shown in general formula I: Formula I; In the general formula I, m is a natural number from 1 to 5, and n is a natural number from 5 to 20.

2. The waste concrete recycled micro powder activator according to claim 1, characterized in that: The nano-silica is prepared by a sol-gel method, with ammonia water as solvent and tetraethoxysilane as silicon source; wherein the mass ratio of the polyether side chain modified polyethylene polyamine organic activated molecule, ammonia water and tetraethoxysilane is (5-15):1:

2.

3. The waste concrete recycled micro powder activator according to claim 1, characterized in that: The average particle size of the regenerated micropowder activator is 100-200 nm.

4. The method for preparing a waste concrete recycled micro powder activator according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1) introducing ethylene oxide into polyethylene polyamine under the action of a catalyst for 1 to 3 hours to obtain an organic activated polyethylene polyamine molecule modified with a polyether side chain; Step 2) Stir and mix the polyether side chain modified polyethylene polyamine organic activated molecules and ammonia water at 30-40°C, slowly add tetraethoxysilane and continue stirring at 30-40°C for 5-10 hours; filter the obtained solid and wash it with a small amount of anhydrous ethanol, and vacuum dry it to obtain the product.

5. The method for preparing a waste concrete recycled micro powder activator according to claim 4, characterized in that: In step 1), the temperature of introducing ethylene oxide is 120-140°C.

6. The method for preparing a waste concrete recycled micro powder activator according to claim 4, characterized in that: Step 1) The catalyst is sodium hydride, sodium methoxide or sodium tert-butoxide.

7. The method for preparing a waste concrete recycled micro powder activator according to claim 4, characterized in that: Step 1) The structural formula of the polyethylene polyamine is shown in general formula II: Formula II; In the general formula II: m is a natural number from 1 to 5; The molar ratio of the polyethylene polyamine, the catalyst and the ethylene oxide is 1:[0.01(2+m)~0.1(2+m)]:[5(2+m)~20(2+m)].

8. The method for preparing a waste concrete recycled micro powder activator according to claim 4, characterized in that: Step 2) The concentration of the ammonia water is 28%.

9. Use of the waste concrete recycled micropowder activator according to any one of claims 1 to 3 in activating waste concrete recycled micropowder.

10. The use according to claim 9, characterized in that: The activator is fully mixed with the recycled fine powder obtained by crushing, removing impurities and grinding the waste concrete in a mass ratio of (0.2~2):100.

Images