LU600218B1

LU600218B1 - A magnesium phosphate adhesive and its application

Info

Publication number: LU600218B1
Application number: LU600218A
Authority: LU
Inventors: Tao Li
Original assignee: Univ Sanjiang
Priority date: 2025-02-12
Filing date: 2025-02-12
Publication date: 2025-08-12

Abstract

This invention provides a magnesium phosphate adhesive, which includes magnesium ammonium phosphate cement and aggregate. The weight ratio of magnesium ammonium phosphate cement to aggregate is 1:1 to 1:1.3. The invention also discloses the application of the magnesium phosphate adhesive. By utilizing retardation and plasticization techniques, the invention imparts good fluidity to the magnesium phosphate adhesive material, enabling self-leveling during construction, simplifying the construction process, and shortening the construction period.

Description

DESCRIPTION HU600218

A MAGNESIUM PHOSPHATE ADHESIVE AND ITS APPLICATION

TECHNICAL FIELD

This invention relates to the field of adhesives, specifically a magnesium phosphate adhesive and its application.

BACKGROUND

After a certain period of use, reinforced concrete structures will undergo corresponding structural strengthening based on different needs. Reinforced concrete slabs are essential load-bearing structures. Reasons for the reinforcement of concrete slabs include insufficient thickness of the floor slab, overly conservative load considerations during design, exposure to fire, and inadequate concrete strength. In maintaining the existing slabs, the first priority is ensuring the load- bearing capacity meets requirements after reinforcement. Secondly, it should meet the owner's clearance requirements for use. Finally, post-reinforcement should fulfill testing requirements, and the reinforcement construction process should be operable.

Traditional reinforcement methods include increasing cross-sectional area, external steel plate bonding, adding steel beams at the bottom of the slab, carbon fiber bonding, and complete replacement. Increasing cross-sectional area not only increases the floor's own weight but also sacrifices net space and affects functionality. External steel plate bonding and carbon fiber bonding can solve net space and structural stress issues, but their organic adhesive bonding with concrete is prone to aging and durability issues. Additionally, steel structures require rust removal, fireproofing, and anti-corrosion treatment, increasing construction complexity. Adding steel beams at the bottom of the slab changes the load transfer 0600818 path, indirectly enhancing load-bearing capacity but altering net floor height and functionality. Steel structures also face corrosion and fireproofing challenges, increasing construction processes. Complete replacement of concrete slabs can fully meet load-bearing, structural safety, and functional requirements but generates construction waste, increases material costs, and extends construction time.

Existing reinforcement methods have limitations. Therefore, reinforcing concrete slabs must not only meet net height requirements but also comply with durability standards, placing high demands on repair materials" mechanical properties (strength, cracking resistance, shrinkage, and bond with the base) and construction performance (high efficiency and short construction time).

SUMMARY

The invention provides a magnesium phosphate adhesive and its application to improve the durability of repair materials and shorten the construction period, addressing technical issues with existing technologies.

The magnesium phosphate adhesive provided by this invention includes ammonium magnesium phosphate cement and aggregate, with a weight ratio of 1:1- 1:1.3 for the ammonium magnesium phosphate cement and aggregate.

Preferably, by weight percentage, the magnesium phosphate cement includes: magnesium oxide powder 59-64%, ammonium dihydrogen phosphate 25-30%, composite retarder 10-11%; wherein the composite retarder comprises: borax 46- 56%, sodium dihydrogen phosphate 40-48%, organic acid 3-7%.

The magnesium oxide powder contains mineral admixtures, with the mineral admixture content being 10-30% of the magnesium oxide powder weight, including fly ash 0-100%, and metakaolin 0-100%.

Additionally, the magnesium phosphate adhesive may include a retarder plasticizer, with a content of 1-3% of the ammonium magnesium phosphate cement, where the retarder plasticizer is sodium silicate with a modulus of 2.8-4.0.

The aggregate is preferably quartz sand, with a weight percentage including: 2- 0600818 4mm particle size 50-70%, and 3-5mm particle size 30-70%.

The performance indicators of the raw materials involved in the above scheme are as follows:

The magnesium oxide powder is produced by calcining magnesite at temperatures above 1500°C, with a purity higher than 90%, a mesh size of 180- 220, providing magnesium ions for the adhesive.

Ammonium dihydrogen phosphate is a white shiny crystal, industrial grade with purity up to 98%, providing phosphate and ammonium ions for the adhesive.

Mineral admixture 1 (metakaolin) has a mesh size of 1250-3000, improving early strength and delaying initial setting time; mineral admixture 2 (fly ash) is industrial grade, improving fluidity and appropriately extending setting time.

In the composite retarder, borax is industrial grade, a white odorless crystal and the main material of the retarder; sodium dihydrogen phosphate is industrial grade, a white odorless crystal regulating pH, fluidity, and providing heat absorption; the organic acid is industrial grade, mainly retarding and prolonging initial setting time while improving later strength.

The retarder plasticizer mentioned is industrial-grade sodium silicate (commonly known as water glass), with a modulus between 2.8 and 4. It mainly improves the toughness and compactness of the phosphate adhesive, thereby enhancing its strength and durability.

The aggregate primarily consists of quartz sand of different particle sizes, with all particle sizes being smaller than 5mm. The distribution includes 2-4mm particles at 50-70% and 3-5mm particles at 30-50%. Quartz sand is obtained from natural quartz ore, processed through crushing, washing, drying, and secondary screening to become a water treatment filter material. Its main component is silicon dioxide, which not only enhances the compressive strength of magnesium phosphate cement but also reduces internal porosity, making the cement denser.

The invention also provides an application of the magnesium phosphate 0600818 adhesive in reinforcing concrete floor slabs. The reinforcement process includes the following steps:

S1: Scarify the bottom surface of the concrete floor slab, remove surface dust, thoroughly wet the bottom surface with water to prevent absorption of moisture from the adhesive during construction.

S2: Nail test pieces of the corresponding casting thickness onto the bottom surface (to control casting thickness easily), support the formwork, apply a release agent on the formwork surface to aid in demolding, maintain absolute levelness during formwork support to avoid affecting the flowability of the phosphate adhesive.

The formwork is in strip form and arranged at spaced intervals on the bottom surface, with casting holes, observation holes, and air vents on the formwork.

S3: Use a hydraulic casting pump to pour the magnesium phosphate adhesive into the casting holes, accompanied by vibration, demold after 6-7 hours of casting.

The casting time should not exceed 20 minutes, and the temperature during casting should be below 35°C. Continuous vibration and construction are necessary, and ice water can be used if needed. For construction under negative temperatures, hot water is used for mixing to promote early hydration and improve early strength. Test specimens (40mmx40mmx160mm prism specimens, 70.7mmx70.7mmx70.7mm cube specimens) are prepared under the same conditions for strength testing at different ages during construction.

The magnesium phosphate adhesive, when poured, is mixed by first combining ammonium dihydrogen phosphate, borax, organic acid, retarder plasticizer, sodium dihydrogen phosphate, and 1/3 of the total weight of water, stirring for 2-3 minutes.

Then, magnesium oxide powder or a mixture of magnesium oxide powder and mineral admixture, along with another 1/3 of the total weight of water, is added and stirred for 2-3 minutes. Finally, quartz sand and the remaining water are added and stirred for another 2-3 minutes. The total weight of water used is 12-14% of the total weight of magnesium oxide powder or the mixture of magnesium oxide powder and mineral admixture.

Compared with existing technologies, this invention offers the following 0600818 beneficial effects: (1) By utilizing retarder and plasticizing techniques, the magnesium phosphate adhesive material gains excellent flowability, enabling self-leveling during construction, simplifying construction processes, and shortening construction periods. (2) Through modification techniques, this invention achieves high early strength and bonding strength with old concrete, with a close linear expansion coefficient, slight expansion during hardening, reducing the design thickness of repair materials to increase indoor space, and ensuring large-scale repairs without cracks. (3) Through modification techniques, the magnesium phosphate adhesive material exhibits excellent fire resistance and durability, thereby enhancing the carbonization resistance and fire resistance of repaired and reinforced concrete structures. (4) The invention utilizes structural measures such as placing reinforcement at the pouring holes to further enhance the bonding strength between the magnesium phosphate adhesive material and old concrete, forming a more integrated structure.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic diagram of the layout of the template for the bottom of the concrete slab in Example 1-3 of the present invention.

Figure 2 is a schematic diagram of the pouring of the bottom of the concrete slab in Example 1-3 of the present invention.

Figure 3 is a diagram of the positive tensile bond strength after the bottom of the slab is reinforced in Example 1-3 of the present invention, wherein, 1-AO, 2-A1, 3-A2.

Figure 4 is a diagram of the flexural strength after the bottom of the slab is reinforced in Example 1-3 of the present invention, wherein, 1-AQ, 2-A1, 3-A2.

Figure 5 is a diagram of the compressive strength after the bottom of the slab 0600818 is reinforced in Example 1-3 of the present invention, wherein, 1-A0, 2-A1, 3-A2.

In Figures 1 and 2, wherein, 1. test block; 2. template; 3. casting hole; 4. observation hole; 5. exhaust hole; 6. magnesium phosphate adhesive.

DETAILED DESCRIPTION OF THE INVENTION

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

Example 1

In this example, the magnesium phosphate adhesive includes ammonium magnesium phosphate cement and quartz sand in a 1:1 weight ratio.

The composition of the cement includes 64% magnesium oxide powder, 25% ammonium dihydrogen phosphate, and 11% composite retarder. The composite retarder comprises 46% borax, 48% sodium dihydrogen phosphate, and 3% organic acid. The quartz sand consists of 70% 2-4mm particles and 30% 3-5mm particles.

The process for reinforcing concrete floor slabs with this adhesive involves the following steps, as depicted in Figures 1-2:

S1. Scarify the bottom surface of the concrete floor slab, remove surface dust, and thoroughly wet the bottom surface.

S2. Nail test pieces of the corresponding casting thickness onto the bottom surface, support the formwork, and apply a release agent on the formwork surface.

S3. Use a hydraulic casting pump to pour the magnesium phosphate adhesive into the casting holes, accompanied by vibration. Demold after 7 hours, wherein,

during pouring, the ammonium dihydrogen phosphate, borax, organic acid, retarder 0600818 plasticizer, sodium dihydrogen phosphate, and 1/3 of the total weight of water are mixed for 3 minutes. Then, magnesium oxide powder or a mixture of magnesium oxide powder and mineral admixture, along with another 1/3 of the total weight of water, is added and mixed for 2 minutes. Finally, quartz sand and the remaining water are added and mixed for 3 minutes. The total weight of water used is 12% of the total weight of magnesium oxide powder or the mixture of magnesium oxide powder and mineral admixture.

This example accelerates construction progress, increases formwork turnover rate, improves indoor space, and enhances the fire resistance and durability of materials.

Example 2

A magnesium phosphate adhesive comprises ammonium magnesium phosphate cement and quartz sand, with a weight ratio of 1:1.3 for the cement and sand.

By weight percentage, the ammonium magnesium phosphate cement includes: magnesium oxide powder (59%), ammonium dihydrogen phosphate (30%), and a composite retarder (10%). The composite retarder comprises borax (56%), disodium hydrogen phosphate (40%), and organic acid (7%). The magnesium oxide powder contains mineral admixture, with the admixture content being 10% of the magnesium oxide powder weight. The mineral admixture includes 60% fly ash and 40% metakaolin. The quartz sand consists of 50% with a particle size of 2-4mm and 70% with a particle size of 3-5mm.

The magnesium phosphate adhesive also includes sodium silicate with a modulus of 4.0, at a content of 1% of the ammonium magnesium phosphate cement.

Referring to Figures 1-2, the process of reinforcing the bottom of concrete floor slabs with the magnesium phosphate adhesive includes the following steps:

S1. Roughen the bottom of the concrete floor slab, remove surface dust, and thoroughly wet the bottom.

S2. Drive in test blocks of the corresponding pouring thickness on the bottom, 0600818 support the templates, and coat the template surfaces with a release agent. The templates are strip-shaped and spaced apart on the bottom; before supporting the templates, create pouring holes, observation holes, and exhaust holes on the templates.

S3. Use a hydraulic pouring pump to pour the magnesium phosphate adhesive into the pouring holes, simultaneously vibrating, and demold after 6 hours.

The pouring time is 18 minutes, and the pouring temperature is 30°C; wherein, during pouring of the magnesium phosphate adhesive, first mix the ammonium dihydrogen phosphate, borax, organic acid, retarding plasticizer, disodium hydrogen phosphate, and 1/3 of the total weight of water for 2-3 minutes.

Then add magnesium oxide powder or a mixture of magnesium oxide powder and mineral admixture, along with another 1/3 of the total weight of water, and mix for 3 minutes. Finally, add quartz sand and the remaining water, and mix for 2 minutes.

The total weight of water used is 14% of the total weight of magnesium oxide powder or the total weight of the mixture of magnesium oxide powder and mineral admixture.

This example speeds up the construction progress, improves the template turnover rate, increases the indoor clearance, and improves the fire resistance and durability of the material.

Example 3 LU600218

A magnesium phosphate adhesive comprises ammonium magnesium phosphate cement and quartz sand, with a weight ratio of 1:1.2 for the cement and sand.

By weight percentage, the ammonium magnesium phosphate cement includes 62% magnesium oxide powder, 27% ammonium dihydrogen phosphate, and 10.5% composite retarder. The composite retarder comprises 50% borax, 45% disodium hydrogen phosphate, and 5% organic acid. The magnesium oxide powder contains mineral admixture, with the admixture content being 30% of the magnesium oxide powder weight. The mineral admixture consists of 20% fly ash and 80% metakaolin.

The quartz sand comprises 60% with a particle size of 2-4mm and 50% with a particle size of 3-5mm.

Additionally, the magnesium phosphate adhesive includes sodium silicate with a modulus of 2.8, at a content of 3% of the ammonium magnesium phosphate cement.

S1. Perform roughening treatment on the bottom of the concrete floor slab, remove surface dust from the roughened areas, and thoroughly wet the bottom with water.

S2. Drive in test blocks 1 of the corresponding pouring thickness onto the bottom, support the templates 2, and coat the template surfaces 2 with a release agent. The templates 2 are strip-shaped and spaced apart on the bottom; before supporting the templates 2, create pouring holes 3, observation holes 4 , and exhaust holes 5 on the templates.

S3. Use a hydraulic pouring pump to pour the magnesium phosphate adhesive into pouring hole 3, while assisting with vibration, and demold after 6.5 hours of pouring.

The pouring time is 15 minutes, and the pouring temperature is 25°C;

wherein, during the pouring of the magnesium phosphate adhesive, first mix 0600818 the ammonium dihydrogen phosphate, borax, organic acid, retarding plasticizer, disodium hydrogen phosphate, and 1/3 of the total weight of water for 2.5 minutes.

Then add magnesium oxide powder or a mixture of magnesium oxide powder and mineral admixture, along with another 1/3 of the total weight of water, and mix for 2.5 minutes. Finally, add quartz sand and the remaining water, and mix for another 2.5 minutes. The total weight of water used is 13% of the total weight of magnesium oxide powder or the total weight of the mixture of magnesium oxide powder and mineral admixture.

This example accelerates construction progress, improves template turnover rates, enhances indoor air quality, and increases the fire resistance and durability of materials.

The flowability of the magnesium phosphate adhesive in Examples 1-3 is 190mm, 236mm, and 260mm, respectively. The test results for tensile bond strength, flexural strength, and compressive strength are shown in Figures 3-5, where AO represents Example 1, A1 represents Example 2, and A2 represents

Example 3.

Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the protection scope of the invention

Claims

CLAIMS LU600218

1.A magnesium phosphate adhesive, characterized in that the magnesium phosphate adhesive comprises magnesium ammonium phosphate cement and aggregate; the weight ratio of magnesium ammonium phosphate cement to aggregate is 1:1 to 1:1.3.

2. The magnesium phosphate adhesive according to claim 1, characterized in that, by weight percentage, the magnesium ammonium phosphate cement comprises. magnesium oxide powder 59-64%, ammonium dihydrogen phosphate 25-30%, composite retarder 10-11%; wherein, the composite retarder comprises: borax 46-56%, sodium dihydrogen phosphate 40-48%, organic acid 3-7%; the magnesium oxide powder contains mineral admixtures, with the content of the mineral admixtures being 10-30% of the weight of the magnesium oxide powder; the mineral admixtures comprise fly ash 0-100% and metakaolin 0-100%.

3. The magnesium phosphate adhesive according to claim 1, characterized in that the magnesium phosphate adhesive further comprises a retarder plasticizer, with the content of the retarder plasticizer being 1-3% of the magnesium ammonium phosphate cement; the retarder plasticizer is sodium silicate, with a modulus of 2.8-

4.0.

4. The magnesium phosphate adhesive according to any one of claims 1-3, characterized in that the aggregate is quartz sand; by weight percentage, the quartz sand comprises: 2-4mm particle size is 50-70%, 3-5mm particle size is 30-70%.

5. The application of the magnesium phosphate adhesive according to any one of claims 1-4 in the reinforcement of concrete floor slab bottoms; the reinforcement process comprises the following steps:

S1. roughen the concrete floor slab bottom, remove surface dust from the 0600818 roughened area, and thoroughly wet the bottom with water;

S2. nail test pieces of the corresponding casting thickness onto the bottom, set up formwork, and coat the surface of the formwork with a release agent; the formwork is strip-shaped and arranged in spaced rows on the bottom; before setting up the formwork, open casting holes, observation holes, and vent holes on the formwork;

S3. use a hydraulic casting pump to pour the magnesium phosphate adhesive into the casting holes, while vibrating, and demold after 6-7 hours of casting; the casting time is not more than 20 minutes, and the casting temperature is below 35°C; when pouring the magnesium phosphate adhesive, first mix ammonium dihydrogen phosphate, borax, organic acid, retarder plasticizer, sodium dihydrogen phosphate, and 1/3 of the total weight of water, stir for 2-3 minutes, then add magnesium oxide powder or a mixture of magnesium oxide powder and mineral admixtures, mix with 1/3 of the total weight of water for 2-3 minutes, and finally add quartz sand and the remaining water, mix for 2-3 minutes; the total weight of water used is 12-14% of the total weight of magnesium oxide powder or the total weight of the mixture of magnesium oxide powder and mineral admixtures.