A composite retarder and its application in magnesium phosphate cement-based material

Abstract

The present invention relates to a composite retarder and its application in magnesium phosphate cement-based materials, and the use methods include but are not limited to the following three methods: 1) dry-mixing the composite retarder powder with the solid components of the magnesium phosphate cement-based materials, and then adding mixing water for stirring and application; 2) fully stirring and dissolving zinc acetate and water, and then adding it to the solid mixture of magnesium phosphate cement-based materials that have been doped with borate, stirring and application; 3) fully stirring and dissolving zinc acetate and borate with mixing water, and then adding it to the solid mixture of magnesium phosphate cement-based materials, stirring and application. Compared with the prior art, the composite retarder of the present invention has a very significant retarding effect. Compared with the traditional single borate retarder, it can greatly extend the setting time of magnesium phosphate cement-based materials, and can achieve effective regulation of the setting time of magnesium phosphate cement-based materials between tens of minutes and more than ten hours, meeting the actual application needs.

Description

Technical Field

[0001] The invention relates to the field of preparation and application of magnesium phosphate cement-based materials, and in particular to a composite retarder and application thereof in magnesium phosphate cement-based materials. Background Art

[0002] Magnesium phosphate cement is a special cementitious material. It is widely used in emergency construction and repair projects in the field of civil engineering, such as airport runways, highways, concrete bridges, military construction projects, deep-sea projects, etc., as well as in the solidification and safe disposal of heavy metals, active metals, and medium and low radioactive materials in the environmental field, due to its advantages of fast setting, high early strength, small shrinkage, good bonding with old concrete, low pH value of the hardened matrix pore solution, and good solidification of heavy metals and medium and low radioactive nuclear waste. In addition, in recent years, magnesium phosphate cement-based materials have many other new applications, such as 3D printing cement-based inks, fuel cell bipolar plates, graphene / magnesium phosphate cement structure supercapacitors, bioengineering repair materials, etc.

[0003] However, the too fast setting of magnesium phosphate cement-based materials will also lead to too short actual application operation time, resulting in the inability to meet construction or other implementation operation requirements. At present, borates (boric acid and borax) are traditional retarders for magnesium phosphate cement-based materials, but the retarding effect of borates is relatively limited. Therefore, in recent years, other various chemical reagents have been used in magnesium phosphate cement-based materials to delay cement coagulation, such as the composite retarder in the invention patents such as application numbers 201310393211.1 and 201510808706.5. Although its retarding effect has been improved to a certain extent, the composite retarder contains chloride salts, which are easy to cause rust to the exposed steel bars in the repair project, affecting the durability of the repaired project. In addition, although invention patents with application numbers such as 202110124840.9, 202110855364.8, and 202111273586.5 do not contain chloride salts, their improvement in the retarding effect on magnesium phosphate cement-based materials is relatively limited and cannot meet the actual construction or other implementation operation requirements.

[0004] In summary, the large-scale mixing and application of magnesium phosphate cement-based materials in actual engineering projects urgently requires a new type of retarder that can effectively prolong the setting time, so as to effectively regulate the setting time of magnesium phosphate cement-based materials according to different actual working conditions. Summary of the invention

[0005] The purpose of the present invention is to provide a composite retarder and its application in magnesium phosphate cement-based materials in order to solve the above problems. Zinc acetate and borate are used as composite retarders. The new composite retarder has a significant retarding effect and can effectively regulate the setting time of magnesium phosphate cement-based materials between tens of minutes and more than ten hours according to the actual requirements of different working conditions.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a composite retarder, which comprises zinc acetate and borate; the composite retarder is used for preparing magnesium phosphate cement-based materials.

[0008] Furthermore, the components of the composite retarder are zinc acetate and borate.

[0009] Furthermore, the ratio of the mass of the zinc acetate to the mass of the borate is 1:9 to 9:1.

[0010] Further preferably, the ratio of zinc acetate to borate is 1:3, 1:1, 3:1.

[0011] Furthermore, the zinc acetate is zinc acetate dihydrate, anhydrous zinc acetate or other zinc acetate hydrates; and the borate is borax or boric acid.

[0012] More preferably, the zinc acetate is zinc acetate dihydrate.

[0013] Further preferably, the borate is borax.

[0014] Furthermore, the composite retarder is prepared by dry mixing zinc acetate and borate in a specified mass ratio to prepare a composite retarder powder to prepare a magnesium phosphate cement-based material, or dissolving zinc acetate in water and directly adding borate to prepare a magnesium phosphate cement-based material, or dissolving zinc acetate and borate in water in a specified mass ratio to prepare a magnesium phosphate cement-based material.

[0015] The second object of the present invention is to provide the use of the above-mentioned composite retarder in magnesium phosphate cement-based materials, and to use the composite retarder in the preparation of magnesium phosphate cement-based materials.

[0016] Furthermore, the magnesium phosphate cement-based material comprises magnesium oxide, phosphate, and the composite retarder.

[0017] Further preferably, the magnesium phosphate cement-based material also includes admixtures, aggregates, functional fillers, and other additives.

[0018] Furthermore, the dosage of the composite retarder used is 0.5% to 10% of the total mass of magnesium oxide and phosphate.

[0019] Further preferably, the dosage of the composite retarder used is 0.5% to 5% of the total mass of magnesium oxide and phosphate.

[0020] Furthermore, the specific use methods of the composite retarder include three (but not limited to) methods:

[0021] Method 1 (Method 1): dry-mix the composite retarder powder with the solid components of the magnesium phosphate cement-based material, and then add mixing water for stirring and application;

[0022] Method 2: Zinc acetate and mixing water are fully stirred and mixed to dissolve, and then added to a solid mixture of magnesium phosphate cement-based materials that has been mixed with borate, and stirred and applied.

[0023] Method three (Method 3): Zinc acetate and borate are fully stirred and mixed with mixing water to dissolve, and then added into the solid mixture of magnesium phosphate cement-based materials, stirred and applied.

[0024] Optionally, the preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps:

[0025] The composite retarder powder is dry-mixed with other components in the magnesium phosphate cement-based material except the composite retarder, and then mixing water is added for stirring.

[0026] Furthermore, the preparation method of the composite retarder powder is to mix zinc acetate and borate according to a set ratio and then stir them evenly using a mortar.

[0027] Optionally, the preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps:

[0028] Zinc acetate and water are fully stirred and mixed to dissolve, and then added into a solid mixture of other components except the composite retarder in the magnesium phosphate cement-based material mixed with borate, and stirred.

[0029] Optionally, the preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps:

[0030] The zinc acetate and borate are fully stirred and mixed with mixing water to dissolve, and then added into the solid mixture of magnesium phosphate cement-based materials for stirring and application.

[0031] Furthermore, the magnesium oxide is dead-burned magnesium oxide.

[0032] Furthermore, the phosphate comprises a mixture of one or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0033] Further, the admixture comprises a mixture of one or more of fly ash, mineral powder, wollastonite (wollastonite powder), metakaolin, diatomaceous earth, recycled micro powder (recycled powder), garbage incineration ash, sludge, etc.;

[0034] Furthermore, the aggregate comprises a mixture of one or more of natural sand and gravel aggregate (natural sand), machine-made sand and gravel, recycled aggregate, artificial aggregate, etc.

[0035] Furthermore, the natural sand and gravel aggregate may be natural sand.

[0036] Furthermore, the functional filler includes one or more of phase change energy storage materials, glass microspheres, titanium dioxide, etc.

[0037] Furthermore, the phase change energy storage material includes one or more of phase change microcapsules, diatomaceous earth / paraffin composite phase change materials, expanded vermiculite / paraffin composite phase change materials, and the like.

[0038] Furthermore, the other admixtures include water reducing agent and the like.

[0039] Furthermore, the water reducer includes one or more of naphthalene-based water reducer, polycarboxylic acid water reducer and the like.

[0040] Furthermore, the magnesium-phosphorus molar ratio (M / P molar ratio) is 1: 1 to 12: 1. The magnesium-phosphorus molar ratio is the ratio of the molar amounts of dead-burned magnesium oxide and phosphate.

[0041] Furthermore, the water-to-solid ratio (W / S) is 0.1 to 0.6. The water in the water-to-solid ratio refers to mixing water, and the solid refers to the sum of magnesium oxide, phosphate, admixture and the composite retarder.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. The composite retarder of the present invention has a significant retarding effect on magnesium phosphate cement-based materials, and can make the setting time of magnesium phosphate cement-based materials exceed 10 hours. Compared with the result of adding traditional retarder borax, the retarding effect is improved by 11 to 55 times, which is much better than the retarding effect of other retarders used in current literature reports and patents.

[0044] 2. The composite retarder of the present invention can prolong the setting time of the magnesium phosphate cement-based material and can effectively regulate the setting time of the magnesium phosphate cement-based material between tens of minutes and more than ten hours by adjusting its dosage. It is suitable for different actual working conditions and will greatly expand the actual application scenarios of magnesium phosphate cement-based materials.

[0045] 3. The composite retarder of the present invention has no adverse effect on the durability of reinforced concrete structures and can effectively solve the problem of corrosion of exposed steel bars in the repaired project caused by the existing chloride-containing composite retarder.

[0046] 4. The composite retarder of the present invention is applicable to different magnesium-phosphorus molar ratios and water-solid ratios, and can also be used in combination with admixtures, aggregates, functional fillers and other types of admixtures without adversely affecting its retarding effect. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0048] During the course of conception, the applicant believed that: borate acts on magnesium oxide to generate insoluble substances to wrap the magnesium oxide particles to delay the reaction of magnesium oxide, while zinc acetate mainly acts on phosphate to slow down the reaction rate of phosphate, and there is a synergistic effect between the two, which makes the retarding effect far better than adding either alone.

[0049] Any features such as preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution shall be deemed as common technical features disclosed in the prior art.

[0050] In the following examples of the present invention, all raw materials are commercially available.

[0051] The following examples and comparative examples mainly include the determination of two indicators, namely, the setting time and compressive strength of magnesium phosphate cement-based materials. The setting time is determined in accordance with GB / T1346-2011 "Test Method for Water Consistency, Setting Time and Stability of Cement Standard Consistency", and the compressive strength is determined in accordance with GB / T17671-1999 "Test Method for Cement Mortar Strength".

[0052] The magnesium oxide was selected as dead-burned magnesium oxide purchased from Jinan Ludong Refractory Material Co., Ltd.

[0053] The phosphate was selected as industrial-grade potassium dihydrogen phosphate with a purity of ≥98 wt %, purchased from Lianyungang Guansu Industrial Co., Ltd.

[0054] The raw materials selected for the retarder of the present invention include the following three, all of which are purchased from Shanghai MacLean Biochemical Technology Co., Ltd.:

[0055] Zinc acetate dihydrate, white crystals, purity ≥99wt%;

[0056] Boric acid, white powder, purity ≥99.5wt%;

[0057] Borax, white powder, purity ≥99.5wt%.

[0058] Fly ash, metakaolin, wollastonite powder, recycled powder, and natural sand are all commercially available products, and recycled powder refers to the industry standard JG / T573-2020 "Recycled Micropowder for Concrete and Mortar". Admixtures and aggregates are not improvements of this application. In the following examples and comparative examples, admixtures and aggregates are added only to verify that the composite retarder of this application is suitable for magnesium phosphate cement systems with different admixtures or aggregates. The specific composition of fly ash, metakaolin, wollastonite powder, recycled powder, and natural sand will not be repeated.

[0059] In order to verify the effectiveness and applicability of the composite retarder of the present invention to magnesium phosphate cement-based materials at different magnesium-phosphorus (M / P) molar ratios, water-solid ratios (W / S), composite retarder components and dosages, admixtures and aggregates, the following comparative examples and examples were carried out.

[0060] Example 1

[0061] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), which is weighed according to the M / P molar ratio of magnesium oxide and potassium dihydrogen phosphate of 4:1. The retarder is composed of zinc acetate dihydrate and boric acid, wherein the ratio of zinc acetate dihydrate to boric acid is 3:1 as the composite retarder No. 1 of the present invention, weighing 2.26% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate, placing zinc acetate dihydrate and boric acid separately, and weighing 0.22 times the total mass of magnesium oxide, potassium dihydrogen phosphate and mixing water of the composite retarder.

[0062] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0063] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0064] (2) The magnesium oxide, potassium dihydrogen phosphate and boric acid were dry-mixed for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, slowly stirred for 90 seconds and rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement with borax as a retarder at the same ratio are shown in Table 2.

[0065] Example 2

[0066] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The retarder is composed of zinc acetate dihydrate and boric acid, wherein the ratio of zinc acetate dihydrate to boric acid is 1:1 as the composite retarder No. 2 of the present invention, weighing 2.26% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate, placing zinc acetate dihydrate and boric acid separately, and weighing 0.22 times the total mass of magnesium oxide, potassium dihydrogen phosphate and composite retarder. Mixing water.

[0067] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0068] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0069] (2) The magnesium oxide, potassium dihydrogen phosphate and boric acid were dry-stirred for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, and the mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time results and the increase in the setting time of magnesium phosphate cement using boric acid as a retarder under the same ratio are shown in Table 2, and the compressive strength results are shown in Table 3.

[0070] Example 3

[0071] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The retarder is composed of zinc acetate dihydrate and boric acid, wherein the ratio of zinc acetate dihydrate to boric acid is 1:3 as the composite retarder No. 3 of the present invention, weighing 2.26% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate, placing zinc acetate dihydrate and boric acid separately, and weighing 0.22 times the total mass of magnesium oxide, potassium dihydrogen phosphate and composite retarder. Mixing water.

[0072] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0073] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0074] (2) After the magnesium oxide, potassium dihydrogen phosphate and boric acid are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using boric acid as a retarder under the same ratio are shown in Table 2.

[0075] Example 4

[0076] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1 as the composite retarder No. 4 of the present invention, weighing 2.26% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate, placing zinc acetate dihydrate and borax separately, and weighing 0.22 times the total mass of magnesium oxide, potassium dihydrogen phosphate and the mixing water of the composite retarder.

[0077] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0078] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0079] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time results and the increase in the setting time of magnesium phosphate cement using boric acid as a retarder under the same ratio are shown in Table 2, and the compressive strength results are shown in Table 3.

[0080] The method adopted in this embodiment is method 2.

[0081] Example 5

[0082] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are mixed in a mortar, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0083] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0084] The weighed composite retarder was added to magnesium oxide and potassium dihydrogen phosphate and stirred for 60 seconds until the mixture was uniform, and then clean water was added and stirred slowly for 90 seconds and quickly for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0085] The method adopted in this embodiment is method 1.

[0086] Example 6

[0087] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0088] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0089] The weighed composite retarder, namely zinc acetate dihydrate and borax, was added to the weighed mixing water and stirred until completely dissolved. After dry stirring in magnesium oxide and potassium dihydrogen phosphate for 60 seconds until evenly mixed, the prepared composite retarder solution was added, slowly stirred for 90 seconds and quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0090] The method adopted in this embodiment is method 3.

[0091] Example 7

[0092] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 1:1. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0093] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0094] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0095] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0096] Example 8

[0097] The present embodiment provides a preparation method of a composite retarder (a composite retarder suitable for a magnesium phosphate cement system), a composite retarder suitable for a magnesium phosphate cement system, and a magnesium oxide and potassium dihydrogen phosphate M / P molar ratio of 8:1 are weighed. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the retarder No. 4 of the present invention with a sum of 2.26% of the mass of magnesium oxide and potassium dihydrogen phosphate is weighed, and zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate, and water 0.22 times the total mass of the composite retarder are weighed.

[0098] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0099] (1) adding weighed zinc acetate dihydrate to weighed water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, to prepare a zinc acetate dihydrate solution;

[0100] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0101] Example 9

[0102] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 12:1. The retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0103] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0104] (1) adding weighed zinc acetate dihydrate to weighed water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, to prepare a zinc acetate solution;

[0105] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0106] Example 10

[0107] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.18 times of the composite retarder are weighed.

[0108] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0109] (1) adding weighed zinc acetate dihydrate to weighed water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, to prepare a zinc acetate solution;

[0110] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0111] Embodiment 11

[0112] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), which is weighed according to the M / P molar ratio of magnesium oxide and potassium dihydrogen phosphate 4:1. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, weighing the composite retarder No. 4 of the present invention with a total mass of 2.26% of magnesium oxide and potassium dihydrogen phosphate, placing zinc acetate dihydrate and borax separately, and weighing 0.25 times the total mass of magnesium oxide, potassium dihydrogen phosphate and composite retarder. Mixing water.

[0113] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0114] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0115] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 2.

[0116] Example 12

[0117] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The composite retarder is composed of zinc acetate dihydrate and boric acid, wherein the ratio of zinc acetate dihydrate to boric acid is 1:1, and the composite retarder No. 2 of the present invention with a total mass of 1.08% of magnesium oxide and potassium dihydrogen phosphate is weighed, and zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0118] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0119] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0120] (2) After the magnesium oxide, potassium dihydrogen phosphate and boric acid are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement with borax as a retarder (2.26%) under the same ratio are shown in Table 2, and the compressive strength results are shown in Table 3.

[0121] Embodiment 13

[0122] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a total mass of 1.08% of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate and mixing water with a total mass of 0.22 times of the composite retarder are weighed.

[0123] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0124] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0125] (2) After the magnesium oxide, potassium dihydrogen phosphate and borax are dry-mixed for 60 seconds until they are uniformly mixed, the zinc acetate solution is added, and the mixture is slowly stirred for 90 seconds and then quickly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder (2.26%) at the same ratio are shown in Table 2.

[0126] Embodiment 14

[0127] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. Fly ash is selected as an admixture, and the admixture amount is 10% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a sum of the mass of magnesium oxide and potassium dihydrogen phosphate of 2.26% is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate, fly ash and mixing water of 0.22 times the total mass of the composite retarder are weighed.

[0128] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0129] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0130] (2) The magnesium oxide, potassium dihydrogen phosphate, fly ash and borax were dry-mixed for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, and the mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 4.

[0131] Embodiment 15

[0132] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. Metakaolin is selected as an admixture, and the admixture amount is 10% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a sum of 2.26% of the mass of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate, metakaolin and 0.22 times the total mass of the composite retarder are weighed. Mixing water.

[0133] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0134] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0135] (2) The magnesium oxide, potassium dihydrogen phosphate, metakaolin and borax were dry-mixed for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, and the mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 4.

[0136] Example 16

[0137] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. Wollastonite powder is selected as an admixture, and the admixture amount is 10% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a sum of 2.26% of the mass of magnesium oxide and potassium dihydrogen phosphate is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate, wollastonite powder and mixing water of 0.22 times the total mass of the composite retarder are weighed.

[0138] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0139] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0140] (2) The magnesium oxide, potassium dihydrogen phosphate, wollastonite powder and borax were dry-stirred for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added. The mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time results are shown in Table 4.

[0141] Embodiment 17

[0142] This embodiment provides a preparation method of a composite retarder (composite retarder suitable for magnesium phosphate cement system), magnesium oxide and potassium dihydrogen phosphate are weighed according to the M / P molar ratio of 4:1. Regenerated powder is selected as an admixture, and the admixture amount is 10% of the sum of the mass of magnesium oxide and potassium dihydrogen phosphate. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and the composite retarder No. 4 of the present invention with a sum of the mass of magnesium oxide and potassium dihydrogen phosphate of 2.26% is weighed, zinc acetate dihydrate and borax are placed separately, and magnesium oxide, potassium dihydrogen phosphate, regenerated powder and 0.22 times the total mass of the composite retarder are weighed. Mixing water.

[0143] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0144] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0145] (2) The magnesium oxide, potassium dihydrogen phosphate, regenerated powder and borax were dry-mixed for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, and the mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement paste. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 4.

[0146] Embodiment 18

[0147] This embodiment provides a method for preparing a composite retarder (a composite retarder suitable for a magnesium phosphate cement system), and magnesium oxide and potassium dihydrogen phosphate are weighed according to a 4:1 molar ratio of M / P. The composite retarder is composed of zinc acetate dihydrate and borax, wherein the ratio of zinc acetate dihydrate to borax is 1:1, and 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate is weighed. Zinc acetate dihydrate and borax are placed separately, and natural sand is selected as fine aggregate to prepare magnesium phosphate cement mortar, and the sand-binder ratio is 80%, that is, 80% of the total mass of magnesium oxide, potassium dihydrogen phosphate, regenerated powder and composite retarder is weighed. Mixing water of 0.22 times the total mass of magnesium oxide, potassium dihydrogen phosphate, regenerated powder and composite retarder is weighed.

[0148] Method of use (application) in the preparation of magnesium phosphate cement-based materials:

[0149] (1) adding weighed zinc acetate dihydrate to weighed mixing water, and stirring thoroughly until the zinc acetate dihydrate is dissolved in the water, thereby preparing a zinc acetate solution;

[0150] (2) The magnesium oxide, potassium dihydrogen phosphate, natural sand and borax were dry-mixed for 60 seconds until they were uniformly mixed, and then zinc acetate solution was added, and the mixture was slowly stirred for 90 seconds and then rapidly stirred for 90 seconds to obtain magnesium phosphate cement mortar. The measured setting time and the increase in the setting time of magnesium phosphate cement using borax as a retarder under the same ratio are shown in Table 4.

[0151] Comparative Example 1

[0152] In order to verify that the composite retarder of the present invention has a better retarding effect than the traditional retarder currently used in the magnesium phosphate cement system, the traditional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio is 4, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.22. The setting time and compressive strength results of the magnesium phosphate cement paste are shown in Tables 2 and 3, respectively.

[0153] Comparative Example 2

[0154] In order to verify that the composite retarder of the present invention has a better retarding effect than the traditional retarder currently used in the magnesium phosphate cement system, the traditional retarder boric acid is used as a comparative example of the present invention, the M / P molar ratio used is 4, the amount of boric acid added is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.22. The setting time and compressive strength results of the magnesium phosphate slurry are shown in Tables 2 and 3, respectively.

[0155] Comparative Example 3

[0156] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when the M / P molar ratio is 1, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio used is 1, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.22. The setting time results of magnesium phosphate slurry are shown in Table 2.

[0157] Comparative Example 4

[0158] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when the M / P molar ratio is 8, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio used is 8, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.22. The setting time results of magnesium phosphate neat slurry are shown in Table 2.

[0159] Comparative Example 5

[0160] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when the M / P molar ratio is 12, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio used is 12, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.22. The setting time results of the magnesium phosphate cement paste are shown in Table 2.

[0161] Comparative Example 6

[0162] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when the water-solid ratio is 0.18, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio is 4, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.18. The setting time results of the magnesium phosphate cement paste are shown in Table 2.

[0163] Comparative Example 7

[0164] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when the water-solid ratio is 0.25, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio used is 4, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the water-solid ratio is 0.25. The setting time results of the magnesium phosphate cement paste are shown in Table 2.

[0165] Comparative Example 8

[0166] In order to verify that the composite retarder of the present invention has a better retarding effect when added with fly ash admixture than the conventional retarder of the current magnesium phosphate cement system, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio is 4, the water-solid ratio is 0.25, and the borax and fly ash dosage is 2.26% and 10% of the total mass of magnesium oxide and potassium dihydrogen phosphate. The setting time results of magnesium phosphate cement paste are shown in Table 4.

[0167] Comparative Example 9

[0168] In order to verify that the composite retarder of the present invention has a better retarding effect when added with metakaolin admixture than the conventional retarder of the current magnesium phosphate cement system, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio is 4, the water-solid ratio is 0.25, and the amounts of borax and metakaolin are 2.26% and 10% of the total mass of magnesium oxide and potassium dihydrogen phosphate. The setting time results of magnesium phosphate cement paste are shown in Table 4.

[0169] Comparative Example 10

[0170] In order to verify that the composite retarder of the present invention has a better retarding effect when added with wollastonite powder admixture than the conventional retarder of the current magnesium phosphate cement system, the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio is 4, the water-solid ratio is 0.25, and the amounts of borax and wollastonite powder are 2.26% and 10% of the total mass of magnesium oxide and potassium dihydrogen phosphate. The setting time results of magnesium phosphate cement paste are shown in Table 4.

[0171] Comparative Example 11

[0172] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when adding the regenerated powder admixture, the conventional retarder borax (sodium tetraborate decahydrate) is used as the comparative example of the present invention, the M / P molar ratio is 4, the water-solid ratio is 0.25, and the borax and regenerated powder dosage is 2.26% and 10% of the total mass of magnesium oxide and potassium dihydrogen phosphate. The setting time results of the magnesium phosphate cement paste are shown in Table 4.

[0173] Comparative Example 12

[0174] In order to verify that the composite retarder of the present invention has a better retarding effect than the conventional retarder of the current magnesium phosphate cement system when adding aggregate (natural sand), the conventional retarder borax (sodium tetraborate decahydrate) is used as a comparative example of the present invention, the M / P molar ratio used is 4, the water-solid ratio is 0.25, the borax dosage is 2.26% of the total mass of magnesium oxide and potassium dihydrogen phosphate, and the ratio of natural sand to the total mass of magnesium oxide, potassium dihydrogen phosphate, and borax, i.e., the sand-binder ratio, is 80%. The setting time results of magnesium phosphate cement mortar are shown in Table 4.

[0175] There are four different combinations of the composite retarder of the present invention used in the examples as shown in Table 1, the composite retarder No. 1 of the present invention: 75% zinc acetate dihydrate + 25% boric acid; the composite retarder No. 2 of the present invention: 50% zinc acetate dihydrate + 50% boric acid; the composite retarder No. 3 of the present invention: 25% zinc acetate dihydrate + 75% boric acid; the composite retarder No. 3 of the present invention: 50% zinc acetate dihydrate + 50% borax. The above ratios are the mass ratios of different components.

[0176] Table 1 Components and proportions of the composite retarder of the present invention.

[0177] serial number Zinc acetate dihydrate (%) Boric acid(%) Borax(%) Composite retarder No. 1 of the present invention 75 25 0 Composite retarder No. 2 of the present invention 50 50 0 Composite retarder No. 3 of the present invention 25 75 0 Composite retarder No. 4 of the present invention 50 0 50

[0178] The test results of setting time of magnesium phosphate cement paste with different M / P molar ratios, water-solid ratios, and retarder types / dosages are shown in Table 2.

[0179] Table 2 Test results of setting time of magnesium phosphate cement paste with different M / P molar ratios, water-solid ratios, and retarder types / dosages.

[0180]

[0181]

[0182]

[0183] The compressive strength test results of magnesium phosphate cement paste of some comparative examples and embodiments are shown in Table 3.

[0184] Table 3 Compressive strength test results of magnesium phosphate cement paste.

[0185]

[0186] The test results of the setting time of magnesium phosphate cement paste and mortar mixed with different admixtures and aggregates in some comparative examples and embodiments are shown in Table 4.

[0187] Table 4 Test results of setting time of magnesium phosphate cement paste and mortar with different admixtures and aggregates.

[0188]

[0189]

[0190] The test results of Tables 1 to 4 show that:

[0191] (1) Compared with the comparative examples (Comparative examples 1, 3-8) in which borax retarder was added under the same proportion, the setting time of the magnesium phosphate cement slurry (Examples 1-11) using the composite retarder of the present invention increased by 32 min to 864 min, with an increase of 267% to 5567%. Compared with comparative example 1, even if the retarder dosage of Examples 12 and 13 was 50% of that of comparative example 1, the setting time of Examples 12 and 13 was still increased by 68 and 15 min, respectively, with an increase of 567% and 125%, which proves that the retarding effect of the composite retarder of the present invention is very significant.

[0192] (2) The test results of Examples 7, 8, 9 and Comparative Examples 3, 4, 5 show that the retarder of the present invention has obvious retarding effect at M / P molar ratios of 1 to 12; the test results of Examples 10, 11 and Comparative Examples 6, 7 show that the composite retarder of the present invention has significant retarding effect at different water-to-solid ratios.

[0193] (3) Compared with comparative examples 8 to 11, the setting time of Examples 14 to 17 with different admixtures increased by 157 min to 258 min, with an increase of 924% to 1518%. The composite retarder of the present invention is suitable for magnesium phosphate cement systems with different admixtures, and its effect is far better than that of the traditional retarder borax.

[0194] (4) Compared with the comparative example 12, the setting time of the embodiment 18 in which the aggregate (natural sand) is added increases by 107 min, with an increase of 713%, indicating that the composite retarder of the present invention is also suitable for magnesium phosphate cement mortar in which the aggregate is added, and the effect is far better than the traditional retarder borax.

[0195] (5) From the compressive strength test results of Comparative Examples 1 and 2 and Examples 2, 4 and 12 in Table 3, it can be seen that the 7d compressive strength of the magnesium phosphate cement paste in Example 11, which uses the composite retarder No. 2 of the present invention and has a dosage of 1.08%, is better than that of Comparative Example 2 using the boric acid retarder alone, and is only 2.4MPa lower than that of Comparative Example 1 using borax, but its setting time is increased by 567% and 129% compared with Comparative Examples 1 and 2, respectively. This shows that the composite retarder of the present invention can double the setting time of magnesium phosphate cement paste at a relatively small dosage, and has almost no adverse effect on the compressive strength of magnesium phosphate cement. The setting time of magnesium phosphate cement in Examples 2 and 4 is extended to 680min and 253min, respectively, wherein the increase in Example 2 is as high as 55.7 times compared with Comparative Example 1, while its 7d compressive strength is only reduced by 28% and 29% respectively compared with Comparative Example 1, which shows that the composite retarder of the present invention has little effect on the compressive strength while greatly increasing the setting time of magnesium phosphate cement.

[0196] (6) Compared with Example 1 in which borax was used alone in the same proportion, the setting time of Examples 4, 5 and 6 were respectively increased by 2008%, 267% and 1883%, indicating that the retarder of the present invention can significantly increase the setting time of magnesium phosphate cement under the three usage methods, but the setting time of Example 4 using method 2 is better than that of Example 5 using method 1 and Example 6 using method 3. Therefore, when conditions permit, the composite retarder of the present invention is more recommended to use method 2 to exert the maximum retarding effect of the composite retarder of the present invention.

[0197] In summary, the composite retarder of the present invention significantly improves the setting time of magnesium phosphate cement-based materials, and its retarding effect is significantly better than that of traditional single borates (borax and boric acid), and it can be used in combination with cement admixtures, aggregates, functional fillers, and other admixtures without adversely affecting the retarding effect; and it has no adverse effect on the mechanical properties of magnesium phosphate cement-based materials, and can meet the mixing, operation and strength requirements of rapid magnesium phosphate cement-based materials in practical applications.

[0198] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A composite retarder, characterized in that: The composite retarder is composed of borax or boric acid and zinc acetate; The mass ratio of the borax or boric acid to zinc acetate is 1:9-9:1; The composite retarder is used for preparing magnesium phosphate cement-based materials; The magnesium phosphate cement-based material comprises magnesium oxide, phosphate, and the composite retarder; The dosage of the composite retarder used is 0.5% to 10% of the total mass of magnesium oxide and phosphate; The composite retarder can prolong the setting time of the magnesium phosphate cement-based material and, by adjusting its dosage, effectively regulate the setting time of the magnesium phosphate cement-based material between tens of minutes and more than ten hours.

2. A composite retarder according to claim 1, characterized in that: The zinc acetate is anhydrous zinc acetate or zinc acetate hydrate.

3. Use of the composite retarder according to any one of claims 1 to 2 in magnesium phosphate cement-based materials, characterized in that: The composite retarder is used in the preparation of magnesium phosphate cement-based materials.

4. The use of a composite retarder in magnesium phosphate cement-based materials according to claim 3, characterized in that: The preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps: The composite retarder powder is dry-mixed with other components in the magnesium phosphate cement-based material except the composite retarder, and then mixing water is added for stirring.

5. The use of a composite retarder in magnesium phosphate cement-based materials according to claim 3, characterized in that: The preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps: Zinc acetate and water are fully stirred and mixed to dissolve, and then added into a solid mixture of other components except the composite retarder in the magnesium phosphate cement-based material which has been added with borax or boric acid, and stirred.

6. Use of a composite retarder in magnesium phosphate cement-based materials according to claim 3, characterized in that: The preparation of the composite retarder for magnesium phosphate cement-based material comprises the following steps: Borax or boric acid and zinc acetate are mixed and dissolved with water, and then added into a solid mixture of magnesium phosphate cement-based materials and stirred.

7. Use of a composite retarder in magnesium phosphate cement-based materials according to claim 3, characterized in that: The magnesium phosphate cement-based material further comprises admixtures, aggregates, functional fillers and other additives.

8. Use of a composite retarder in magnesium phosphate cement-based materials according to claim 7, characterized in that: The phosphate comprises a mixture of one or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; The admixture comprises a mixture of one or more of fly ash, mineral powder, wollastonite, metakaolin, diatomaceous earth, recycled micro powder, garbage incineration ash, and sludge; The aggregate comprises a mixture of one or more of natural sand and gravel aggregate, machine-made sand and gravel, recycled aggregate, and artificial aggregate; The functional filler comprises one or more of phase change energy storage materials, glass microspheres, and titanium dioxide; The other admixtures include a water reducing agent.

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