阅读说明：本技术 一种氯氧镁水泥改性剂及其制备方法和氯氧镁水泥 (Magnesium oxychloride cement modifier, preparation method thereof and magnesium oxychloride cement ) 是由 唐孝林 王东星 王少卿 蒲隆进 杨铎 于 2021-10-12 设计创作，主要内容包括：本发明公开了一种氯氧镁水泥改性剂及其制备方法和氯氧镁水泥,所述氯氧镁水泥改性剂的原料以质量分数计包括：柠檬酸18～25％、硫酸亚铁41～49％、脲醛树脂乳液28～38％和氯化铵0.1～0.5％。本发明中柠檬酸18～25％、硫酸亚铁41～49％、脲醛树脂乳液28～38％和氯化铵0.1～0.5％各组分协同配合,加入到氯氧镁水泥固化淤泥体系中,共同促使氯氧镁水泥固化淤泥体系形成更加致密的结构,增强结构稳定性。显著提高氯氧镁水泥固化淤泥体系强度和耐水性,延长其在极端条件下的使用寿命。(The invention discloses a magnesium oxychloride cement modifier, a preparation method thereof and magnesium oxychloride cement, wherein the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride. According to the invention, 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride are cooperatively matched, and the components are added into a magnesium oxychloride cement solidified sludge system to jointly promote the magnesium oxychloride cement solidified sludge system to form a more compact structure and enhance the structural stability. The strength and the water resistance of the magnesium oxychloride cement solidified sludge system are obviously improved, and the service life of the magnesium oxychloride cement solidified sludge system under extreme conditions is prolonged.)

1. The magnesium oxychloride cement modifier is characterized by comprising the following raw materials in parts by mass: 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride.

2. The magnesium oxychloride cement modifier of claim 1, wherein the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 25%, ferrous sulfate: 41% of urea-formaldehyde resin emulsion: 33.7%, ammonium chloride: 0.3 percent.

3. The magnesium oxychloride cement modifier of claim 1, wherein the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 18%, ferrous sulfate: 49% of urea-formaldehyde resin emulsion: 32.9%, ammonium chloride: 0.1 percent.

4. The magnesium oxychloride cement modifier of claim 1, wherein the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 19.5%, ferrous sulfate: 42% urea-formaldehyde resin emulsion: 38%, ammonium chloride: 0.5 percent.

5. The magnesium oxychloride cement modifier of claim 1, wherein the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 23.7%, ferrous sulfate: 48% of urea-formaldehyde resin emulsion: 28%, ammonium chloride: 0.3 percent.

6. The magnesium oxychloride cement modifier of any one of claims 1 to 5, wherein the citric acid is technical grade citric acid.

7. The magnesium oxychloride cement modifier of any one of claims 1 to 5, wherein the ferrous sulfate is ferrous sulfate heptahydrate.

8. The magnesium oxychloride cement modifier of any one of claims 1 to 5, wherein the urea-formaldehyde resin emulsion is a urea-formaldehyde resin having a solid content of 60% to 65%.

9. A method of preparing a magnesium oxychloride cement modifier according to any one of claims 1 to 8, wherein the method comprises: uniformly mixing the raw materials of the magnesium oxychloride cement modifier of any one of claims 1 to 8 according to the weight ratio to obtain the magnesium oxychloride cement modifier.

10. A magnesium oxychloride cement, wherein the magnesium oxychloride cement comprises, in weight fractions:

100 parts of silt soil;

5-7 parts of magnesium oxide;

3-5 parts of magnesium chloride;

0.15-0.5 part of magnesium oxychloride cement modifier.

Technical Field

The invention relates to the technical field of cement modification, in particular to a magnesium oxychloride cement modifier, a preparation method thereof and magnesium oxychloride cement.

Background

With the social progress and the development of science and technology, a large amount of dredged sludge is generated in industrial production and environmental protection engineering, and because the sludge has the characteristics of high water content, low strength, large compressibility, high organic matter content and the like, the sludge is generally difficult to be directly used as engineering filling in road engineering and defense engineering. With the rapid development of the building industry, a large amount of traditional portland cement is used to cause certain pollution to the environment, and the utilization rate of a large amount of industrial solid wastes is low, so that resource waste and environmental pollution are caused. In order to reduce environmental pollution and improve the utilization rate of industrial solid wastes, the research of developing novel cement from the industrial solid wastes for the field of sludge solidification becomes a key research point.

Magnesium oxychloride cement is a special cement invented in 1867 by sorel of the country, so it is also called sorel cement, which uses magnesium oxide as main component, and has the advantages of quick setting, low cost, little pollution, etc. and is widely used as building decorative material and roadbed concrete. However, the existing magnesium oxychloride cement has poor water resistance, and the durability fails in the using process, so that the service life is influenced; in addition, the strength of the existing magnesium oxychloride cement is not high. Therefore, the research and development of the magnesium oxychloride curing system with good water resistance can develop the engineering performance and expand the application field by overcoming the defects.

Therefore, how to prepare the magnesium oxychloride cement modifier capable of improving the water resistance and the strength of the magnesium oxychloride cement becomes a technical problem in the field.

Disclosure of Invention

The invention aims to provide a magnesium oxychloride cement modifier which can improve the water resistance and strength of magnesium oxychloride cement and prolong the service life of a magnesium oxychloride cement curing system under extreme conditions such as water immersion and the like.

The invention adopts the following technical scheme:

in a first aspect of the present invention, there is provided a magnesium oxychloride cement modifier, wherein the magnesium oxychloride cement modifier comprises the following raw materials by mass: 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride.

Further, the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 25%, ferrous sulfate: 41% of urea-formaldehyde resin emulsion: 33.7%, ammonium chloride: 0.3 percent.

Further, the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 18%, ferrous sulfate: 49% of urea-formaldehyde resin emulsion: 32.9%, ammonium chloride: 0.1 percent.

Further, the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 19.5%, ferrous sulfate: 42% urea-formaldehyde resin emulsion: 38%, ammonium chloride: 0.5 percent.

Further, the magnesium oxychloride cement modifier comprises the following raw materials in parts by mass: citric acid: 23.7%, ferrous sulfate: 48% of urea-formaldehyde resin emulsion: 28%, ammonium chloride: 0.3 percent.

Further, the citric acid is industrial grade citric acid.

Further, the ferrous sulfate is ferrous sulfate heptahydrate.

Further, the urea-formaldehyde resin emulsion is urea-formaldehyde resin with the solid content of 60 wt% -65 wt%.

In a second aspect of the present invention, there is provided a method for preparing a magnesium oxychloride cement modifier, the method comprising: uniformly mixing the raw materials of the magnesium oxychloride cement modifier according to the weight ratio to obtain the magnesium oxychloride cement modifier.

In a third aspect of the present invention, there is provided a magnesium oxychloride cement, comprising in weight fractions:

100 parts of silt soil;

5-7 parts of magnesium oxide;

3-5 parts of magnesium chloride;

0.15-0.5 part of magnesium oxychloride cement modifier.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

1. according to the magnesium oxychloride cement modifier, 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride are cooperatively matched and added into a magnesium oxychloride cement solidified sludge system to jointly promote the magnesium oxychloride cement solidified sludge system to form a more compact structure and enhance the structural stability. The strength and the water resistance of the magnesium oxychloride cement solidified sludge system are obviously improved, and the service life of the magnesium oxychloride cement solidified sludge system under extreme conditions is prolonged.

2. According to the magnesium oxychloride cement provided by the invention, due to the addition of the modifier, the negative influence of a single modifier on an MOC curing system is weakened through series of physical and chemical effects, the strength development of the MOC curing system in a standard curing period is comprehensively promoted, and the problem of poor water resistance of a magnesium oxychloride material in a water-soaked and humid environment is solved. The strength development and the water resistance in a soaking and humid environment during standard curing of the curing system are obviously improved, the strength retention coefficient of a sample reaches 85 percent after the sample is continuously soaked for 28 days, the service life is prolonged, and the application range of the curing system is widened.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 shows that unconfined compressive strength of magnesium oxychloride cured sludge samples obtained in comparative example 1 and examples 1 to 3 is obtained after natural curing for 7 days and 28 days and soaking curing for 7 days and 28 days;

FIG. 2 shows the strength retention coefficients of samples of magnesium oxychloride cured sludge in the case of soaking in water for 7 days and 28 days in comparative example 1 and examples 1 to 3;

FIG. 3 is an SEM comparison of cured sludge of magnesium oxychloride after standard 28 days of curing and 28 days of soaking curing in water for comparative example 1 and example 1; wherein: FIG. 3(a) shows the results of standard curing of the sample of comparative example 1 for 28 days, FIG. 3(b) shows the results of immersion of the sample of comparative example 1 for 28 days, FIG. 3(c) shows the results of standard curing of the sample of example 1 for 28 days, and FIG. 3(d) shows the results of immersion of the sample of example 1 for 28 days.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be obtained by an existing method.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to a typical embodiment of the invention, a magnesium oxychloride cement modifier is provided, and the raw materials of the magnesium oxychloride cement modifier comprise, by mass: 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride.

In the invention, 18-25% of citric acid, 41-49% of ferrous sulfate, 28-38% of urea-formaldehyde resin emulsion and 0.1-0.5% of ammonium chloride are cooperatively matched and added into a magnesium oxychloride cement solidified sludge system to jointly promote the magnesium oxychloride cement solidified sludge system to form a more compact structure and enhance the structural stability. The strength and the water resistance of the magnesium oxychloride cement solidified sludge system are obviously improved, and the service life of the magnesium oxychloride cement solidified sludge system under extreme conditions is prolonged. Specifically, the method comprises the following steps:

18-25% of citric acid, and the citric acid ion group is adsorbed on the surface of magnesium oxide to form CAⁿ-→Mg(OH)(H₂O)_x-1The group plays a role in retarding coagulation, inhibits the early hydration reaction of magnesium oxide in a system, and reduces Mg (OH) in the system₂While affecting the transformation of the needle-like 5-phase structure into a plate-like structure, and [ CA ]^n-→Mg(OH)(H₂O)_x-1]The group can still generate 5-phase crystals, and the later strength of the system is improved. Therefore, the citric acid plays a role in retarding to inhibit strength development in the composite modifier, simultaneously enhances the strength development of the system at the later period of maintenance, and simultaneously improves the water resistance through the influence on the appearance of the 5 phase and the generation amount of the 5 phase in the system. If the mass fraction of the citric acid is less than 18%, the adverse effect of limited generation amount of coordination bonds and coordination structures participating in the reaction to generate 5-phase crystals is generated; if the mass fraction of the citric acid is more than 25 percent, the adverse effects of obviously prolonging the setting and hardening time and reducing the alkalinity of the system so as to inhibit the generation and development of 5 phases are caused;

41-49% of ferrous sulfate, wherein the ferrous sulfate generates Fe (OH) in the system₃The gel structure and M/C-S-H-Cl gel can block pores and capillary channels, and improve water resistance. The gel structure generated in the early stage of maintenance and the MOC hydration product play a role in improving the strength together, the influence of citric acid on the early strength development of the system can be reduced, the early strength development is enhanced, meanwhile, the generated gel structure fills pores through physical action, the permeation erosion channel of water is reduced, the water resistance of the system is further improved, but the generated gel structure consumes OH in the system^-Is not beneficial to the generation of 5-phase crystals in the later period and weakens the strength in the later period of maintenance. If the mass fraction of the ferrous sulfate is less than 41 percent, the gel generation amount is not enough to effectively seal pores and wrap crystals; if the mass fraction of the ferrous sulfate is more than 49%, the alkalinity of the system is deeply reduced, and MgO is wrapped to hinder the generation of 5 phases;

28-38% of urea-formaldehyde resin emulsion, urea-formaldehyde resin polymer is activated by ammonium chloride, and is synergistically agglomerated and wrapped with a gel product generated by ferrous sulfate through excellent diffusion and uniform distribution performance to play a role in hardening and crosslinking, the strength of the system is jointly improved by 5 phases, and meanwhile, the urea-formaldehyde resin polymer can wrap 5 phases of crystals to form a hydrophobic protective layer, so that the contact of chloride ions and water is reduced, and the water resistance is improved. If the mass fraction of the urea-formaldehyde resin emulsion is less than 28%, the adverse effects of limited hardening effect and low 5-phase generation rate are caused; if the mass fraction of ammonium chloride is more than 38%, the water absorption of ammonium chloride lowers the free water content in the sample, thereby adversely affecting the continuation of the chemical reaction;

0.1-0.5% of ammonium chloride, and the ammonium chloride fully excites the activity of the urea-formaldehyde resin polymer to improve Mg in the system²⁺More 5 phases are generated by concentration, and additional chloride ions are provided for a magnesium oxychloride cement system to participate in complexation and hydroxylation reactions, so that the cross-lapping growth of crystals is promoted, and a network structure with stronger cohesive force and binding force is formed. If the mass fraction of the ammonium chloride is less than 0.1%, the adverse effect of limited quantity of the ions participating in the reaction is provided; if the mass fraction of the ammonium chloride is more than 0.5%, the alkalinity of the system is excessively reduced, so that the generation of a cementing product is influenced;

in conclusion, the components are cooperated and enhanced to increase the efficiency, and the strength and the water resistance of the magnesium oxychloride cement solidified sludge system are improved remarkably.

As an alternative embodiment, the raw materials of the magnesium oxychloride cement modifier comprise, by mass: citric acid: 25%, ferrous sulfate: 41% of urea-formaldehyde resin emulsion: 33.7%, ammonium chloride: 0.3 percent.

As an alternative embodiment, the raw materials of the magnesium oxychloride cement modifier comprise, by mass: citric acid: 18%, ferrous sulfate: 49% of urea-formaldehyde resin emulsion: 32.9%, ammonium chloride: 0.1 percent.

As an alternative embodiment, the raw materials of the magnesium oxychloride cement modifier comprise, by mass: citric acid: 19.5%, ferrous sulfate: 42% urea-formaldehyde resin emulsion: 38%, ammonium chloride: 0.5 percent.

As an alternative embodiment, the raw materials of the magnesium oxychloride cement modifier comprise, by mass: citric acid: 23.7%, ferrous sulfate: 48% of urea-formaldehyde resin emulsion: 28%, ammonium chloride: 0.3 percent.

In the technical scheme, the citric acid is industrial citric acid. The ferrous sulfate is ferrous sulfate heptahydrate. The urea-formaldehyde resin is 60-65 wt% of solid content. The starting materials are all commercially available.

According to another exemplary embodiment of the present invention, there is provided a method for preparing a magnesium oxychloride cement modifier, the method including: uniformly mixing the raw materials of the magnesium oxychloride cement modifier according to the weight ratio to obtain the magnesium oxychloride cement modifier.

According to another exemplary embodiment of the present invention, there is provided a magnesium oxychloride cement, comprising in weight fractions:

100 parts of silt soil;

5-7 parts of magnesium oxide;

3-5 parts of magnesium chloride;

0.15-0.5 part of magnesium oxychloride cement modifier.

The strength and the water resistance of the magnesium oxychloride cement solidified sludge system can be obviously improved by adopting the proportion, and the service life of the magnesium oxychloride cement solidified sludge system under extreme conditions is prolonged. The negative influence of a single modifier on an MOC curing system is weakened through series physical and chemical effects due to the addition of the composite modifier, the strength development of the MOC curing system in a standard curing period is comprehensively improved, and the problem of poor water resistance of the magnesium oxychloride material in a water-soaked and humid environment is solved. The strength development and the water resistance in a soaking and humid environment during standard curing of the curing system are obviously improved, the strength retention coefficient of a sample reaches 85 percent after the sample is continuously soaked for 28 days, the service life is prolonged, and the application range of the curing system is widened.

In a preferred embodiment, the magnesium oxychloride cement is 10 parts.

When in use, the components are uniformly mixed according to the proportion.

A magnesium oxychloride cement modifier of the present application will be described in detail with reference to examples, comparative examples and experimental data.

Example 1

Weighing 25% of citric acid, 41% of ferrous sulfate, 33.7% of urea-formaldehyde resin emulsion and 0.3% of ammonium chloride according to the weight ratio to prepare a modifier, sequentially adding the modifier into silt soil, fully and uniformly stirring, then adding magnesium oxychloride cement (including magnesium oxide and magnesium chloride, the same below) according to the ratio shown in Table 1 to cure, curing to a corresponding age to carry out an unconfined compressive strength test, carrying out a continuous soaking test after standard curing for 28 days, carrying out a strength test after the corresponding age and calculating a strength retention coefficient.

When the addition amount of the modifier is 3 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.45MPa in 7 days, and the strength of the standard curing is 1.70MPa in 28 days. The strength after soaking in water for 7 days was 1.47MPa, the strength retention coefficient was 86.5%, the strength after soaking in water for 28 days was 1.40MPa, and the strength retention coefficient was 82.3%.

When the addition amount of the modifier is 5 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.51MPa in 7 days, and the strength of the standard curing is 1.80MPa in 28 days. The strength after soaking in water for 7 days was 1.59MPa, the strength retention coefficient was 88.4%, the strength after soaking in water for 28 days was 1.54MPa, and the strength retention coefficient was 85.6%.

Example 2

Weighing 18% of citric acid, 49% of ferrous sulfate, 32.9% of urea-formaldehyde resin emulsion and 0.1% of ammonium chloride according to the weight ratio to prepare a modifier, sequentially adding the modifier into silt soil, fully and uniformly stirring, then adding magnesium oxychloride cement with the ratio shown in Table 1 to cure, curing to a corresponding age to carry out a non-lateral-limit compressive strength test, carrying out a continuous soaking test after standard curing for 28 days, carrying out a strength test after the corresponding age and calculating a strength retention coefficient.

When the addition amount of the modifier is 3 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.55MPa in 7 days, and the strength of the standard curing is 1.65MPa in 28 days. The strength after soaking in water for 7 days was 1.44MPa, the strength retention coefficient was 87.3%, the strength after soaking in water for 28 days was 1.37MPa, and the strength retention coefficient was 83.0%.

When the addition amount of the modifier is 5 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.60MPa in 7 days, and the strength of the standard curing is 1.73MPa in 28 days. The strength after soaking for 7 days was 1.55MPa, the strength retention coefficient was 89.6%, the strength after soaking for 28 days was 1.45MPa, and the strength retention coefficient was 83.8%.

Example 3

Weighing 19.5% of citric acid, 42% of ferrous sulfate, 38% of urea-formaldehyde resin emulsion and 0.5% of ammonium chloride according to the weight ratio to prepare a modifier, sequentially adding the modifier into the silt soil, fully and uniformly stirring, then adding magnesium oxychloride cement with the ratio shown in Table 1 to cure, curing to a corresponding age to carry out a non-lateral-limit compressive strength test, carrying out a continuous soaking test after standard curing for 28 days, carrying out a strength test after the corresponding age and calculating a strength retention coefficient.

When the addition amount of the modifier is 3 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.50MPa in 7 days, and the strength of the standard curing is 1.67MPa in 28 days. The strength after soaking for 7 days was 1.40MPa, the strength retention coefficient was 84%, the strength after soaking for 28 days was 1.30MPa, and the strength retention coefficient was 78.4%.

When the addition amount of the modifier is 5 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.56MPa in 7 days, and the strength of the standard curing is 1.78MPa in 28 days. The strength after soaking for 7 days was 1.51MPa, the strength retention coefficient was 84.8%, the strength after soaking for 28 days was 1.43MPa, and the strength retention coefficient was 80.3%.

Example 4

Weighing 19.5% of citric acid, 42% of ferrous sulfate, 38% of urea-formaldehyde resin emulsion and 0.5% of ammonium chloride according to the weight ratio to prepare a modifier, sequentially adding the modifier into silt soil, fully and uniformly stirring, then curing magnesium oxychloride cement with the ratio shown in Table 1, curing to a corresponding age to carry out a non-lateral-limit compressive strength test, carrying out a continuous soaking test after standard curing for 28 days, carrying out a strength test after the corresponding age and calculating a strength retention coefficient.

When the addition amount of the modifier is 3 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.52MPa in 7 days, and the strength of the standard curing is 1.65MPa in 28 days. The strength after soaking in water for 7 days was 1.42MPa, the strength retention coefficient was 84.1%, the strength after soaking in water for 28 days was 1.35MPa, and the strength retention coefficient was 78.6%.

When the addition amount of the modifier is 5 percent of the mass of magnesium oxide in the curing agent, the strength of the standard curing is 1.54MPa in 7 days, and the strength of the standard curing is 1.71MPa in 28 days. The strength after soaking for 7 days was 1.50MPa, the strength retention coefficient was 84.3%, the strength after soaking for 28 days was 1.41MPa, and the strength retention coefficient was 80.1%.

Comparative example 1

In the comparative example, the magnesium oxychloride cement modifier is not added, and specifically comprises the following components: and adding magnesium oxychloride cement with the soil silt mass of 10% to the mixture, fully and uniformly curing the mixture, curing the mixture to a corresponding age to perform an unconfined compressive strength test, performing a continuous soaking test 28 days after standard curing, performing a strength test after the corresponding age, and calculating a strength retention coefficient.

The strength of the standard curing is 1.37MPa after 7 days, and the strength of the standard curing is 1.54MPa after 28 days. The strength after soaking in water for 7 days was 1.21MPa, the strength retention coefficient was 78.5%, the strength after soaking in water for 28 days was 1.00MPa, and the strength retention coefficient was 64.9%.

Comparative example 2

In this comparative example, a magnesium oxychloride cement modifier is provided that does not include citric acid; the other steps were the same as in example 1.

Comparative example 3

In this comparative example, a magnesium oxychloride cement modifier is provided that does not include ferrous sulfate; the other steps were the same as in example 1.

Comparative example 4

In this comparative example, a magnesium oxychloride cement modifier is provided that does not include a urea formaldehyde resin emulsion; the other steps were the same as in example 1.

Comparative example 5

In this comparative example, a magnesium oxychloride cement modifier is provided that does not include ammonium chloride; the other steps were the same as in example 1.

Comparative example 6

In the comparative example, the magnesium oxychloride cement modifier comprises the following components in percentage by mass: 30% of citric acid, 30% of ferrous sulfate, 39% of urea-formaldehyde resin emulsion and 1% of ammonium chloride.

Comparative example 7

In the comparative example, the magnesium oxychloride cement modifier comprises the following components in percentage by mass: 13% of citric acid, 65% of ferrous sulfate, 21.95% of urea-formaldehyde resin emulsion and 0.05% of ammonium chloride.

Experimental example 1

And curing the magnesium oxychloride cured sludge samples in the embodiments and the various proportions to corresponding ages to carry out unconfined compressive strength tests, carrying out continuous soaking tests 28 days after standard curing, carrying out strength tests after corresponding ages, and calculating strength retention coefficients. And respectively measuring the compressive strength of the magnesium oxychloride cured sludge sample which is soaked for 7 days and 28 days after natural curing for 7 days and 28 days and is soaked for 28 days after natural curing for 28 days. A WDW-50kN microcomputer is adopted to control an electronic universal tester, and the loading rate is set to be 1mm/min for testing.

The examples and the formula of the magnesium oxychloride cement modifier in each comparative example are shown in table 1, and the measured compressive strength and strength coefficient of the magnesium oxychloride cement in each example and each comparative example are shown in table 2. Wherein the intensity retention coefficient is calculated by:

in the formula: p_nThe softening coefficient of the test piece after being soaked in n d water

U₀The mean compressive strength (MPa) of the sample for standard maintenance for 28d

U_nIs the mean compressive strength (MPa) of a sample soaked in water n d

TABLE 1

TABLE 2

From the data in table 2, it can be seen that:

in comparative example 1, the compressive strength and water resistance of the test sample are low without adding the magnesium oxychloride cement modifier of the invention;

in the comparative example 2, the magnesium oxychloride cement modifier is not added with citric acid, so that the sample has the defect of low long-term strength;

in the comparative example 3, the magnesium oxychloride cement modifier does not add ferrous sulfate, and the sample has the defect of low early strength;

in comparative example 4, the magnesium oxychloride cement modifier does not contain urea-formaldehyde resin emulsion, and the sample has the defect of poor water resistance;

in comparative example 5, the magnesium oxychloride cement modifier does not contain ammonium chloride, and the sample has the defects of slow strength development and low water resistance;

in comparative example 6, the proportion of each component of the magnesium oxychloride cement modifier is out of the range of the invention, and the sample has the defects of lower strength and poor water resistance;

in comparative example 7, the proportion of each component of the magnesium oxychloride cement modifier is out of the range of the invention, and the sample has the defects of lower strength and poor water resistance;

the compressive strength of the magnesium oxychloride cured sludge samples immersed for 7 days and 28 days after natural curing and immersed for 7 days and 28 days after natural curing of examples 1-4 are all higher than that of the comparative example, and the strength retention coefficient is all higher than that of the comparative example 1, which shows that the water resistance can be obviously improved by using the modifier of the example.

In conclusion:

compared with the example 1 of the invention, the components of citric acid, ferrous sulfate, urea-formaldehyde resin emulsion and ammonium chloride are cooperated and added into the solidified sludge system of the magnesium oxychloride cement, so that the strength and the water resistance of the solidified sludge system of the magnesium oxychloride cement are obviously improved, and the synergistic effect is generated.

Comparative examples 6 to 7 compared with example 1 of the present invention, it is found that the ranges of any one of the citric acid, ferrous sulfate, urea-formaldehyde resin emulsion and ammonium chloride are not within the ranges of the examples of the present invention (18 to 25% of citric acid, 41 to 49% of ferrous sulfate, 28 to 38% of urea-formaldehyde resin emulsion and 0.1 to 0.5% of ammonium chloride), and it is difficult to produce a good synergistic effect.

Description of the drawings:

FIG. 1 shows compressive strengths of samples of magnesium oxychloride cured sludge immersed in water for 7 days and 28 days after natural curing for 7 days and 28 days and after natural curing for 28 days in comparative example 1 and examples 1 to 3. The compressive strength of the modified samples obtained from FIG. 1 is higher than that of comparative example 1.

FIG. 2 shows the strength retention coefficients of samples of magnesium oxychloride cured sludge prepared in comparative example 1 and examples 1 to 3, and it can be observed that the water resistance of examples 1 to 3 is higher than that of comparative example 1, indicating that the use of the composite modifier can obviously improve the water resistance.

FIG. 3 is SEM comparison of standard curing for 28 days and soaking curing for 28 days of magnesium oxychloride cured sludge in comparative example 1 and example 1, and it can be seen from FIG. 3 that the modified sample generates more crystals during curing and has well-developed and robust appearance; after soaking, the modified sample has relatively less crack structure, retains more flaky 5-phase crystals, and thus shows a good strength retention coefficient.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.