A polycarboxylic acid water reducing agent for high micro-powder recycled masonry mortar, a preparation method and application thereof

Abstract

The application relates to a polycarboxylic acid water reducing agent for high-micro-powder regenerated masonry mortar and a preparation method and application thereof. The polycarboxylic acid water reducing agent is prepared through the following steps: mixing and dissolving IPEG and water, heating to a certain temperature, adding an oxidizing agent, and preparing solution A; mixing a reducing agent and a chain transfer agent, and preparing solution B by adding water; mixing an unsaturated acid monomer and a phosphoric acid group-containing monomer, and preparing solution C by adding water; adding solution B and solution C into solution A, stirring at constant temperature until the reaction is completed, and cooling to room temperature to obtain the polycarboxylic acid water reducing agent. Compared with the prior art, the polycarboxylic acid water reducing agent has the advantages of reducing adsorption of the polycarboxylic acid water reducing agent on micro powder, improving the dispersion effect of the polycarboxylic acid water reducing agent, and improving the working performance of the high-micro-powder regenerated masonry mortar.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture preparation, and in particular to a polycarboxylate superplasticizer for high-micron recycled masonry mortar, its preparation method and application. Background Technology

[0002] The scale of construction waste production in my country is increasing, and its large-scale accumulation has led to numerous environmental burdens. Utilizing recycled building materials from construction waste to protect the environment and reduce energy consumption and emissions has become an industry consensus. The crushed concrete contained in construction waste can be converted into recycled aggregate for masonry mortar production through secondary crushing. In addition, construction waste also contains a large amount of fine powder, which, when appropriately added to mortar, can significantly improve mortar strength. The combined application of recycled aggregate and fine powder to prepare high-fine-powder recycled masonry mortar can greatly improve the resource utilization rate of construction waste and alleviate its accumulation problem. However, due to characteristics such as high water absorption, recycled aggregate and fine powder can cause a significant decrease in mortar workability. In practice, polycarboxylate superplasticizers must be added to improve the workability of high-fine-powder recycled masonry mortar. Even so, due to the similar particle size of fine powder and cement, they compete for the adsorption of superplasticizer molecules, resulting in a significant reduction in the dispersion effect of the superplasticizer. The above situation hinders the engineering and industrial application of high-fine-powder recycled masonry mortar, and there is an urgent need to develop a high-efficiency polycarboxylate superplasticizer specifically adapted to high-fine-powder recycled masonry mortar.

[0003] Patent publication number CN117903378A discloses a polycarboxylate superplasticizer containing phosphate groups, its preparation method, and its application. The method includes the following steps: adding isopentenyl alcohol polyoxyethylene ether to a reaction vessel, adding deionized water, and automatically stirring at room temperature until completely dissolved; adding an aqueous solution of unsaturated carboxylic acid monomers, a chain transfer agent, an aqueous solution of an initiator, and a monomer containing phosphate groups; adjusting the reaction vessel temperature to 65-70℃ and reacting at this temperature for 2-2.5 hours; subsequently raising the temperature to 70-75℃ and holding for 3-3.5 hours; cooling to room temperature to obtain the polycarboxylate superplasticizer containing phosphate groups. However, in the preparation of this superplasticizer, the initiator containing the oxidant is added after the isopentenyl alcohol polyoxyethylene ether, which can easily lead to problems such as uneven reaction rates. Furthermore, the high reaction temperature poses certain uncontrollable and dangerous risks. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as poor adaptability and poor dispersion of polycarboxylate superplasticizers in high-fineness recycled mortar, and to provide a polycarboxylate superplasticizer for high-fineness recycled masonry mortar, its preparation method and application, thereby reducing the adsorption of fineness by polycarboxylate superplasticizer, improving the dispersion effect of polycarboxylate superplasticizer, and thus improving the workability of high-fineness recycled masonry mortar.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One of the technical solutions of this invention is to provide a method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar, comprising the following steps:

[0007] Dissolve isopentenyl alcohol polyoxyethylene ether (IPEG) in water, heat to a certain temperature, add oxidant, and prepare solution A;

[0008] Mix the reducing agent and chain transfer agent, and add water to prepare solution B;

[0009] Mix unsaturated acid monomers and monomers containing phosphate groups, and add water to prepare solution C;

[0010] Add solutions B and C to solution A, stir at a constant temperature until the reaction is complete, cool to room temperature, and the polycarboxylate superplasticizer is obtained. The reaction is complete.

[0011] Further, IPEG and water are mixed and dissolved, and heated to 25~35°C, preferably 29~31°C; the temperature for constant temperature stirring is 25~35°C, preferably 29~31°C.

[0012] Further, in solution A, the molar ratio of IPEG, unsaturated acid monomer, and phosphate-containing monomer is 1:3~5:0.01~0.2, preferably 1~3.5~4.5:0.05~0.15;

[0013] The mass ratio of the total mass of the oxidant, reducing agent, chain transfer agent, IPEG, unsaturated acid monomer, and phosphate-containing monomer is 1~1.2:0.15~0.2:0.35~0.4:100.

[0014] Furthermore, the mass concentration of IPEG in solution A is 30%~80%, preferably 40%~60%;

[0015] The mass concentration of the reducing agent in solution B is 1% to 5%, preferably 1% to 3%;

[0016] The mass concentration of unsaturated acid monomers in solution C is 30%~80%, preferably 40%~60%.

[0017] Furthermore, the oxidant is ammonium persulfate (APS);

[0018] The reducing agent is ascorbic acid (VC).

[0019] The chain transfer agent is β-mercaptopropionic acid (MPA).

[0020] The unsaturated acid monomer is acrylic acid (AA).

[0021] The phosphate-containing monomer is 2-(methacryloyloxy)ethyl phosphate (MOEP).

[0022] Furthermore, the molecular weight of the IPEG is 4000~5000.

[0023] Furthermore, solutions B and C are added to solution A via a peristaltic pump, with the total addition time being 3 to 3.5 hours, followed by 0.5 to 2 hours of constant temperature stirring.

[0024] The second technical solution of the present invention is to provide a polycarboxylate superplasticizer for high-micron recycled masonry mortar, which is prepared by the preparation method described above.

[0025] Furthermore, the weight-average molecular weight of the polycarboxylate superplasticizer is 4000~45000.

[0026] The third technical solution of the present invention is to provide an application of a polycarboxylate superplasticizer for high-fineness recycled masonry mortar in the field of high-fineness recycled masonry mortar, characterized in that the polycarboxylate superplasticizer is used to prepare high-fineness recycled masonry mortar.

[0027] Furthermore, the high-micron recycled masonry mortar includes micronized powder, recycled aggregate, cement, polycarboxylate superplasticizer, and water.

[0028] Furthermore, the mass content of micro powder in the high-micro powder recycled masonry mortar is 10wt%~20wt%.

[0029] Furthermore, the solid content of polycarboxylate superplasticizer in the high-fineness recycled masonry mortar is 0.1wt%~0.5wt%, that is, the polycarboxylate superplasticizer accounts for 0.1wt%~0.5wt% of the total mass of solids in the high-fineness recycled masonry mortar.

[0030] Furthermore, the mass ratio of cement to recycled aggregate is 1:2 to 3, preferably 1:2 to 2.5.

[0031] Furthermore, the mass ratio of water to cement (i.e., the water-cement ratio) is 0.4~0.45:1.

[0032] Furthermore, the particle size of the recycled aggregate is 1.18~4.75mm.

[0033] Furthermore, the cement is silicate cement.

[0034] Furthermore, the particle size of the micro powder is less than 0.075 mm.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The polycarboxylate superplasticizer provided by the present invention is synthesized in one step using IPEG, unsaturated acid monomers, phosphate-containing monomer oxidants, reducing agents and chain transfer agents as raw materials. The preparation process is simple, the reaction is mild and the pollution is small.

[0037] (2) The polycarboxylate superplasticizer provided by the present invention has adsorption groups such as carboxyl groups and phosphate groups in the reactive polymer chain, which can reduce the adsorption of the superplasticizer on the micro powder and improve the dispersion effect of the superplasticizer.

[0038] (3) The present invention fully disperses IPEG and oxidant before reaction, which reduces the temperature required to maintain the reaction rate, improves the controllability of the reaction process, and reduces the reaction risk.

[0039] (4) The present invention adds an oxidant before the reaction and disperses it fully, which avoids uneven generation of free radicals when the oxidant is added during the reaction and improves the purity of the product.

[0040] (5) By slowly adding solutions B and C, this invention ensures that the reducing agent, chain transfer agent and unsaturated monomer are evenly distributed in the system, thereby improving the reaction efficiency.

[0041] (6) When preparing high-micro powder recycled masonry mortar, adding a small amount of polycarboxylate superplasticizer provided by the present invention can significantly improve the workability of high-micro powder recycled masonry mortar. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0043] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0044] In the following embodiments, VC's CAS number is 50-81-7, Shanghai testing; MPA's CAS number is 107-96-0, Alfa-A13261, 99%; AA's CAS number is 79-10-7, AR (Shanghai testing), ≥99.0%; MOEP's CAS number is 52628-03-2, 98% (Wokai); all of the above were purchased from Sinopharm Chemical Reagent Co., Ltd. The reference silicate cement (PO 42.5) was purchased from Tangshan Polar Bear Building Materials Co., Ltd. Recycled micro-powder and recycled aggregate were collected from abandoned building demolition sites. The commercial water-reducing agent was PCA®-I polycarboxylate high-performance water-reducing agent, purchased from Jiangsu Subote New Material Co., Ltd.

[0045] Example 1

[0046] A method for preparing a polycarboxylate superplasticizer includes the following steps:

[0047] (1) Place 112.9g of IPEG into a flask, add an equal mass of water, and then place it in a 30℃ water bath for constant temperature. Use an external electric stirrer until the IPEG dissolves. Then add 0.12g of APS (oxidant) to the solution to form solution A.

[0048] (2) Add 0.18g VC (reducing agent) and 0.42g MPA (chain transfer agent) to a beaker, add 29.4g water, stir with a glass rod, and prepare mixed solution B.

[0049] (3) Add 0.5g AA (unsaturated acid monomer) and 6.6g MOEP (monomer containing phosphate group) to a beaker, add 7.1g water, stir with a glass rod, and prepare unsaturated monomer solution C.

[0050] (4) Solution B and unsaturated monomer solution C were slowly added to solution A simultaneously using a peristaltic pump at pumping rates of 0.04 ml / min and 0.16 ml / min, respectively. The total time for the addition process was 3.5 h. After the addition was completed, the solution was stirred at a constant temperature of 30°C for 1 h. Then the solution was poured out of the flask and cooled to room temperature to obtain the polycarboxylate superplasticizer.

[0051] Based on the ratio of raw materials to water, the solid content of the polycarboxylate superplasticizer is calculated to be 40%.

[0052] The sample was taken and the weight-average molecular weight of the water-reducing agent was determined by GPC to be 42977, and the dispersion coefficient was 1.6.

[0053] The polycarboxylate superplasticizer prepared in this embodiment is applied to the preparation of high-micron recycled masonry mortar, as follows:

[0054] The high-micro-powder recycled masonry mortar includes micro-powder, recycled aggregate, cement, polycarboxylate superplasticizer, and water.

[0055] The high-fineness recycled masonry mortar comprises a gelling material, a polycarboxylate superplasticizer, and water. The cementitious material comprises fine powder, recycled aggregate, and cement. Specifically, it uses 90 wt% standard silicate cement (PO 42.5), 10 wt% fine powder with a particle size less than 0.075 mm, 33 wt% recycled fine aggregate of 1.18~2.36 mm and 67 wt% of 2.36~4.75 mm. The amount of polycarboxylate superplasticizer is 0.1 wt% of the cementitious material, the water-cement ratio is 0.45, and the mass ratio of cement to recycled aggregate is 1:2. The mortar is mixed according to GB / T 17671-2021, and the mortar fluidity is measured according to GB / T 2419-2009 after mixing.

[0056] Example 2

[0057] Compared with Example 1, most of them are the same, except that the amount of micro powder added is adjusted to 15wt% in the preparation process of high-micro powder recycled masonry mortar.

[0058] Example 3

[0059] Compared with Example 1, most of them are the same, except that the amount of micro powder added is adjusted to 20wt% in the preparation process of high-micro powder recycled masonry mortar.

[0060] Example 4

[0061] Compared with Example 1, most of the process is the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.3% in the preparation of high-micron recycled masonry mortar.

[0062] Example 5

[0063] Compared with Example 2, most of the contents are the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.3% in the preparation of high-micron recycled masonry mortar.

[0064] Example 6

[0065] Compared with Example 3, most of them are the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.3% in the preparation process of high-micron recycled masonry mortar.

[0066] Example 7

[0067] Compared with Example 1, most of them are the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.5% in the preparation process of high-micron recycled masonry mortar.

[0068] Example 8

[0069] Compared with Example 2, most of them are the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.5% in the preparation process of high-micron recycled masonry mortar.

[0070] Example 9

[0071] Compared with Example 3, most of them are the same, except that the dosage of polycarboxylate superplasticizer is adjusted to 0.5% in the preparation process of high-micron recycled masonry mortar.

[0072] Comparative Example 1

[0073] Most of the components are the same as in Example 1, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0074] Comparative Example 2

[0075] Most of the components are the same as in Example 2, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0076] Comparative Example 3

[0077] Most of the components are the same as in Example 3, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0078] Comparative Example 4

[0079] Most of the components are the same as in Example 4, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0080] Comparative Example 5

[0081] Most of the components are the same as in Example 5, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0082] Comparative Example 6

[0083] Most of the components are the same as in Example 6, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0084] Comparative Example 7

[0085] Most of the components are the same as in Example 7, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0086] Comparative Example 8

[0087] Most of the components are the same as in Example 8, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0088] Comparative Example 9

[0089] Most of the components are the same as in Example 9, except that the polycarboxylate superplasticizer is replaced with a commercial superplasticizer.

[0090] The flowability test results of the high-micron recycled masonry mortars prepared in Examples 1-9 and Comparative Examples 1-9 are shown in Tables 1 and 2.

[0091] Table 1. Flowability test results of the high-micron recycled masonry mortar prepared in Examples 1-9

[0092]

[0093] Table 2. Flowability test results of the high-micron recycled masonry mortar prepared in Examples 1-9

[0094]

[0095] As shown in Tables 1 and 2, the high-micron powder recycled masonry mortar prepared by this invention exhibits good adaptability, and the low dosage of carboxylic acid water-reducing agent can effectively improve the fluidity of the recycled masonry mortar. Furthermore, compared to commercial water-reducing agents, the carboxylic acid water-reducing agent prepared by this invention significantly increases the improvement in the fluidity of the recycled masonry mortar.

[0096] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar, characterized in that, Includes the following steps: Dissolve isopentenyl alcohol polyoxyethylene ether in water, heat to 25-35℃, add oxidant, and prepare solution A; Mix the reducing agent and chain transfer agent, and add water to prepare solution B; Mix unsaturated acid monomers and monomers containing phosphate groups, and add water to prepare solution C; Add solutions B and C to solution A, stir at a constant temperature until the reaction is complete, cool to room temperature, and you will get the polycarboxylate superplasticizer. The reaction is complete. The molar ratio of isopentenyl alcohol polyoxyethylene ether, unsaturated acid monomer, and phosphate-containing monomer is 1:3~5:0.01~0.2; The chain transfer agent is β-mercaptopropionic acid; The unsaturated acid monomer is acrylic acid; The phosphate-containing monomer is 2-(methacryloyloxy)ethyl phosphate.

2. The method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 1, characterized in that, Dissolve isopentenyl alcohol polyoxyethylene ether in water and heat to 25~35℃; maintain constant temperature stirring at 25~35℃.

3. The method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 1, characterized in that, The mass ratio of the total mass of the oxidant, reducing agent, chain transfer agent, isopentenyl alcohol polyoxyethylene ether, unsaturated acid monomer, and phosphate-containing monomer is 1~1.2:0.15~0.2:0.35~0.4:

100.

4. The method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 1, characterized in that, The mass concentration of isopentenyl alcohol polyoxyethylene ether in solution A is 30%~80%; The mass concentration of the reducing agent in solution B is 1%~5%; The mass concentration of unsaturated acid monomers in solution C is 30%~80%.

5. The method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 1, characterized in that, The oxidant is ammonium persulfate; The reducing agent is ascorbic acid.

6. The method for preparing a polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 1, characterized in that, Solution B and solution C are added to solution A via a peristaltic pump. The total time for the addition process is 3 to 3.5 hours, and the time for constant temperature stirring after addition is 0.5 to 2 hours.

7. A polycarboxylate superplasticizer for high-micron recycled masonry mortar, which is prepared by any one of the preparation methods described in claims 1 to 6.

8. A polycarboxylate superplasticizer for high-micron recycled masonry mortar according to claim 7, characterized in that, The weight-average molecular weight of the polycarboxylate superplasticizer is 4000~45000.

9. The application of the polycarboxylate superplasticizer for high-fineness recycled masonry mortar as described in claim 7 in the field of high-fineness recycled masonry mortar, characterized in that, The polycarboxylate superplasticizer is used to prepare high-micron recycled masonry mortar.

10. The application according to claim 9, characterized in that, The high-micro-powder recycled masonry mortar includes micro-powder, recycled aggregate, cement, polycarboxylate superplasticizer, and water.

Images