A water-resistant magnesium phosphate repair mortar based on industrial waste and its preparation method

Abstract

This invention discloses a water-resistant magnesium phosphate repair mortar based on industrial waste residue and its preparation method, comprising mineral admixtures, potassium dihydrogen phosphate, magnesium oxide, quartz sand, organosilicon gel, retarder, and mixing water; the mineral admixtures are composed of steel slag, nickel slag, and fly ash. During preparation, potassium dihydrogen phosphate, retarder, and mixing water are first mixed and stirred, then the mineral admixtures, magnesium oxide, and organosilicon gel are added sequentially and stirred rapidly, and finally the quartz sand is added and stirred. The repair mortar of this invention exhibits a setting time ≥23 min, fluidity ≥195 mm, 3-hour compressive strength ≥25.2 MPa, 3-day compressive strength ≥47.4 MPa, 3-hour flexural strength ≥3.6 MPa, 3-day flexural strength ≥6.1 MPa, and 1-day tensile bond strength ≥0.8 MPa; and a water absorption ratio below 0.15.

Description

Technical Field

[0001] This invention belongs to the field of magnesium phosphate repair mortar, and particularly relates to a water-resistant magnesium phosphate repair mortar based on industrial waste residue and its preparation method. Background Technology

[0002] With the rapid development of infrastructure construction in my country, defects in concrete structures caused by aging, natural disasters, and other external factors during long-term service are becoming increasingly prominent. To prevent these defects from worsening, rapid repair is necessary. This places new demands on traditional structural repair materials, which are characterized by long construction cycles, complex procedures, and high costs. Magnesium phosphate repair mortar, as a new type of repair material, is a cementitious material formed by mixing phosphates, magnesium oxide, and fine aggregates with water. Due to its excellent early strength and fluidity, magnesium phosphate repair mortar is widely used in road repair, bridge construction, and municipal engineering projects.

[0003] Currently, the main material in magnesium phosphate repair mortar, magnesium oxide, is produced from natural magnesite through high-temperature calcination and crushing. Magnesite is a non-renewable energy source, and improving reaction efficiency is a preferred solution for achieving low-carbon and environmentally friendly practices. Existing magnesium phosphate repair mortars have advantages over cement-based repair materials due to their rapid hardening, early strength, and convenient construction. However, their use is limited by defects such as excessively rapid early hardening time and limited mid-term strength improvement.

[0004] Therefore, there is an urgent need to develop a new type of magnesium phosphate repair mortar that is lower in carbon than traditional repair mortar, has a controllable setting time during construction, good fluidity, stable strength growth after forming, and strong water resistance. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a water-resistant magnesium phosphate repair mortar based on industrial waste residue, which can effectively increase mechanical properties such as setting time and water resistance, and its preparation method.

[0006] Technical solution: The present invention is based on water-resistant magnesium phosphate repair mortar made from industrial waste residue, which includes, by mass fraction, 8-10 parts of mineral admixture, 15-22 parts of potassium dihydrogen phosphate, 30-37 parts of magnesium oxide, 44-52 parts of quartz sand, 0.4-1.8 parts of organosilicon gel, 0.8-1.1 parts of retarder and 8-15 parts of mixing water.

[0007] Firstly, the magnesium phosphate repair mortar of the present invention, based on potassium dihydrogen phosphate and magnesium oxide, incorporates organosilicon gel. This organosilicon gel is a solid-liquid coexisting cementitious material. On one hand, its addition allows it to adhere to the magnesium oxide particles, hindering the contact between the magnesium oxide particles and water, slowing down the hydrolysis process, and thus delaying the hydration reaction of the magnesium phosphate cementitious material. On the other hand, due to its solid-liquid coexisting characteristics, the organosilicon gel can effectively flow and disperse in the internal pore structure of the repair mortar as a filler. Under the exothermic conditions of the hydration reaction, it promotes the curing of the organosilicon gel, thereby not only improving the overall mechanical properties of the repair mortar, but also effectively improving its water resistance due to its filling of pores and its hydrophobic properties, further enhancing its mechanical properties.

[0008] Furthermore, the mineral admixture used in this repair mortar is made by mixing steel slag, nickel slag, and fly ash in a weight ratio of 1:(2-4):(1-2), and then ball-milling with 0.03-0.05% of triethanolamine, a grinding aid, in the weight ratio of the three. Preferably, the mineral admixture contains ≥10% MgO in the steel slag, ≥30% total MgSiO3 and Mg2SiO4 content in the nickel slag, and ≥75% total silica and alumina content in the fly ash.

[0009] The ball-milled solid waste mineral admixture of this invention possesses both an activity effect and a micro-aggregate filling effect. While increasing the strength of magnesium phosphate repair mortar, it can also slow down the hydration reaction. The incorporation of industrial waste residue can also better realize the resource utilization of solid waste. The ground mineral admixture not only reduces the amount of fly ash used but also effectively improves the growth mode of MgKPO4·6H2O crystals in the main hydration products. The smaller particle size of the ball-milled mineral admixture can fill the pores within the products, exerting a micro-aggregate effect to a certain extent, thereby improving the mechanical properties of magnesium phosphate repair mortar.

[0010] Furthermore, the retarder used in this repair mortar is a mixture of boric acid and sucrose in a weight ratio of (1-3):1.

[0011] Furthermore, the particle size of the potassium dihydrogen phosphate retarder used in the repair mortar can be 2-30μm; the particle size of the quartz sand can be 0.5-2.0mm.

[0012] Furthermore, the magnesium oxide retarder used in this repair mortar can be obtained by calcining and grinding magnesite at 1500-1800℃, with a particle size of 2-60μm and a specific surface area of ​​360m². 2 / kg.

[0013] The method for preparing the above-mentioned water-resistant magnesium phosphate repair mortar based on industrial waste residue according to the present invention includes the following steps:

[0014] (1) Mix potassium dihydrogen phosphate, retarder, and mixing water for 1-2 minutes;

[0015] (2) Add magnesium oxide, organosilicon gel and mineral admixture in sequence and mix for 1-2 minutes;

[0016] (3) Finally, add quartz sand and mix for 2-3 minutes to obtain the water-resistant magnesium phosphate repair mortar.

[0017] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: the setting time of the repair mortar is ≥23min, and the setting time is controllable; the fluidity is ≥195mm, indicating good fluidity; the 3h compressive strength is ≥25.2MPa, the 3d compressive strength is ≥47.4MPa, the 3h flexural strength is ≥3.6MPa, and the 3d flexural strength is ≥6.1MPa, indicating good strength stability; the 1d tensile bond strength is ≥0.8MPa, indicating good bonding performance; and the water absorption ratio can reach below 0.15, indicating strong water resistance. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the embodiments. It should be noted that the raw materials used in the present invention can all be purchased commercially. Among them, the steel slag was purchased from Yancheng Lianxin Steel Co., Ltd.; the nickel slag was purchased from Jiangsu Delong Nickel Industry Co., Ltd.

[0019] The mineral admixture used in this invention is a mixture of steel slag, nickel slag, and fly ash in a weight ratio of 1:(2-4):(1-2). Its preparation method includes the following steps: adding a composite powder of steel slag, nickel slag, and fly ash, along with 0.03-0.05% (by weight) of triethanolamine (a grinding aid), to a ball mill. The mixture is then ball-milled for 2-3 hours at a ball-to-material ratio of 3-4:1 and a rotation speed of 400-600 r / min, followed by drying to obtain a specific surface area of ​​380 m². 2 The mixture contains 12.2% residue on a 45-micron square-hole sieve. Furthermore, the mineral admixtures contain ≥10% MgO in steel slag, ≥30% total MgSiO3 and Mg2SiO4 content in nickel slag, and ≥75% total silica and alumina content in fly ash.

[0020] The magnesium oxide used in this invention is magnesite calcined and ground at 1500-1800℃, with a particle size of 2-60μm and a specific surface area of ​​360m². 2 / kg.

[0021] The potassium dihydrogen phosphate used in this invention has a particle size of 2-30 μm; the quartz sand has a particle size distribution of 0.5-2.0 mm.

[0022] Example 1

[0023] The component contents of the water-resistant magnesium phosphate repair mortar in Example 1 are shown in Table 1 below.

[0024] Table 1. Component content of repair mortar in Example 1

[0025]

[0026] The preparation method of this repair mortar includes the following steps:

[0027] (1) Mix potassium dihydrogen phosphate, retarder, and mixing water and stir at a low speed of 140 r / min for 1-2 min;

[0028] (2) Add magnesium oxide, organosilicon gel and mineral admixture in sequence and stir rapidly at 285 r / min for 1-2 min;

[0029] (3) Finally, add quartz sand and stir rapidly at a speed of 285r / min for 2-3 minutes to obtain the water-resistant magnesium phosphate repair mortar.

[0030] Example 2

[0031] The component content of the water-resistant magnesium phosphate repair mortar in Example 2 is shown in Table 2 below.

[0032] Table 2. Component content of repair mortar in Example 2

[0033]

[0034] The preparation method of Example 2 is the same as that of Example 1.

[0035] Example 3

[0036] The component contents of the water-resistant magnesium phosphate repair mortar in Example 3 are shown in Table 3 below.

[0037] Table 3. Component content of repair mortar in Example 3

[0038]

[0039] The preparation method of Example 3 is the same as that of Example 1.

[0040] Example 4

[0041] The component contents of the water-resistant magnesium phosphate repair mortar in Example 4 are shown in Table 4 below.

[0042] Table 4. Component content of repair mortar in Example 4

[0043]

[0044] The preparation method of Example 4 is the same as that of Example 1.

[0045] Example 5

[0046] The component contents of the water-resistant magnesium phosphate repair mortar in Example 5 are shown in Table 5 below.

[0047] Table 5. Component content of repair mortar in Example 5

[0048]

[0049] The preparation method of Example 5 is the same as that of Example 1.

[0050] Example 6

[0051] The component contents of the water-resistant magnesium phosphate repair mortar in Example 6 are shown in Table 6 below.

[0052] Table 6. Component content of repair mortar in Example 6

[0053]

[0054]

[0055] The preparation method of Example 5 is the same as that of Example 1.

[0056] Comparative Example 1

[0057] The basic raw materials for Comparative Example 1 are the same as those for Example 6, except that the magnesium oxide was not ground. The specific components are shown in Table 7.

[0058] Table 7 shows the component content of the repair mortar in Comparative Example 1.

[0059]

[0060] The preparation method of Comparative Example 1 is the same as that of Example 6.

[0061] Comparative Example 2

[0062] The basic raw materials for Comparative Example 2 are the same as those for Example 6, except that a single fly ash component is used instead of mineral admixtures. The specific components are shown in Table 8.

[0063] Table 8. Component content of repair mortar in Comparative Example 2

[0064]

[0065]

[0066] The preparation method of Comparative Example 2 is the same as that of Example 6.

[0067] Comparative Example 3

[0068] The basic raw materials for Comparative Example 3 are the same as those for Example 6, except that boric acid is used instead of retarder. The specific components are shown in Table 9.

[0069] Table 9 shows the component content of the repair mortar in Comparative Example 3.

[0070] Serial Number raw material Number of weights 1 Mineral admixtures 8 2 Potassium dihydrogen phosphate 15 3 magnesium oxide 30 4 Quartz sand 44 5 Organosilicon gel 0.7 6 boric acid 0.8 7 Mixing water 9

[0071] The preparation method of Comparative Example 3 is the same as that of Example 6.

[0072] Comparative Example 4

[0073] The basic steps are the same as in Example 6, except that no silicone gel is added to the raw materials. The component contents are shown in Table 10 below.

[0074] Table 8. Component content of repair mortar in Comparative Example 2

[0075]

[0076]

[0077] The preparation method of Comparative Example 4 includes the following steps:

[0078] (1) Mix potassium dihydrogen phosphate, retarder, and mixing water and stir at a low speed of 140 r / min for 1-2 min;

[0079] (2) Add magnesium oxide and mineral admixture in sequence and stir rapidly at a speed of 285 r / min for 1-2 min;

[0080] (3) Finally, add quartz sand and stir rapidly at a speed of 285r / min for 2-3 minutes to obtain the water-resistant magnesium phosphate repair mortar.

[0081] Performance testing

[0082] The cured magnesium phosphate repair mortar was prepared according to the "Standard for Test Methods of Basic Performance of Building Mortar".

[0083] Setting time was tested according to JGJ / T70—2009. Flowability was tested according to GB / T2419—2005, "Determination of Flowability of Cement Mortar". 3-hour flexural and compressive strength and 3-day flexural and compressive strength were tested according to GB / T17671—2021, "Test Method for Strength of Cement Mortar". 1-day tensile bond strength was tested according to JC / T2537—2019, "Magnesium Phosphate Repair Mortar". The water resistance of the samples was characterized by measuring the water absorption ratio, denoted by W. A smaller W value indicates better water resistance, and vice versa. The test results are shown in Table 11.

[0084] Table 11 Performance tests of the repair mortars prepared in Examples 1-6 and Comparative Examples 1-4

[0085]

[0086]

[0087] As shown in Table 11, the repair mortar has a setting time of ≥23 min, which is controllable; a fluidity of ≥195 mm, indicating good fluidity; a 3-hour compressive strength of ≥25.2 MPa, a 3-day compressive strength of ≥47.4 MPa, a 3-hour flexural strength of ≥3.6 MPa, and a 3-day flexural strength of ≥6.1 MPa, indicating good strength stability; a 1-day tensile bond strength of ≥0.8 MPa, indicating good bonding performance; and a water absorption ratio of less than 0.15, indicating strong water resistance.

Claims

1. A water-resistant magnesium phosphate repair mortar based on industrial waste residue, characterized in that... The composition by weight is as follows: 8-10 parts mineral admixture, 15-22 parts potassium dihydrogen phosphate, 30-37 parts magnesium oxide, 44-52 parts quartz sand, 0.4-1.8 parts organosilicon gel, 0.8-1.1 parts retarder, and 8-15 parts mixing water; the magnesium oxide is magnesite calcined and ground at 1500-1800℃, with a particle size of 2-60μm and a specific surface area of ​​360m². 2 / kg; The method for preparing this water-resistant magnesium phosphate repair mortar includes the following steps: (1) Mix potassium dihydrogen phosphate, retarder, and mixing water and stir for 1-2 minutes; (2) Add magnesium oxide, organosilicon gel and mineral admixture in sequence and mix for 1-2 minutes; (3) Finally, add quartz sand and mix for 2-3 minutes to obtain the water-resistant magnesium phosphate repair mortar.

2. The water-resistant magnesium phosphate repair mortar based on industrial waste residue according to claim 1, characterized in that: The mineral admixture is made by mixing steel slag, nickel slag and fly ash in a weight ratio of 1:(2-4):(1-2), and then adding 0.03-0.05% of the grinding aid triethanolamine in weight and ball milling.

3. The water-resistant magnesium phosphate repair mortar based on industrial waste residue according to claim 2, characterized in that: The mineral admixtures contain ≥10% MgO in steel slag; ≥30% total MgSiO3 and Mg2SiO4 in nickel slag; and ≥75% total silica and alumina in fly ash.

4. The water-resistant magnesium phosphate repair mortar based on industrial waste residue according to claim 1, characterized in that: The retarder is a mixture of boric acid and sucrose in a weight ratio of (1-3):

1.

5. The water-resistant magnesium phosphate repair mortar based on industrial waste residue according to claim 1, characterized in that: The potassium dihydrogen phosphate has a particle size of 2-30 μm; the quartz sand has a particle size distribution of 0.5-2.0 mm.

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