CN115403333A

CN115403333A - Durable cement mortar

Info

Publication number: CN115403333A
Application number: CN202211048045.7A
Authority: CN
Inventors: 陈芳山
Original assignee: Jiangxi Jinye Industrial Co ltd
Current assignee: Tangshan Fengluan New Materials Co ltd
Priority date: 2022-08-30
Filing date: 2022-08-30
Publication date: 2022-11-29
Anticipated expiration: 2042-08-30
Also published as: CN115403333B

Abstract

The invention discloses durable cement mortar which comprises the following raw materials in parts by weight: 20 to 50 portions of cement, 60 to 150 portions of sand, 1 to 3 portions of modifier and 8 to 20 portions of water. According to the invention, magnesium oxide and stearic acid are mixed, a nonionic surfactant is added, and a magnesium stearate emulsion is prepared by using a simple chemical reaction and is used as a modifier of cement mortar, so that the hydrophobic properties of the inner and outer surfaces of the mortar are obviously improved; the cobaltosic oxide is added to further improve the hydrophobic property of the mortar, improve the mechanical strength, water resistance and chloride ion resistance of the mortar and improve the shrinkage property of the cement mortar.

Description

Durable cement mortar

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to durable cement mortar.

Background

At present, the higher content of carbon dioxide in the atmosphere has brought certain influence on the natural environment and the survival of human beings. Human activities such as the combustion of fossil energy, the production of cement, etc. are major sources of carbon dioxide emissions. Among them, the production and manufacture of cement is considered to be one of the most industries causing an increase in carbon dioxide emission. The cement mortar is prepared from cement, fine aggregate, water and other additives according to construction requirements, and is widely applied to the fields of masonry, plastering, decoration engineering and the like. Cement is the most used gel material. Therefore, functional substances are added into the cement mortar to modify the cement mortar, so that the durability of the cement mortar is improved, the utilization rate of resources is improved, and the environment is protected.

CN 113387667A discloses an impervious cement mortar, which is composed of the following raw materials by weight: 95-130 parts of quicklime, 50-82 parts of kaolin or modified kaolin, 260-295 parts of water, 3-6 parts of water reducing agent, 32-40 parts of aggregate and 10-23 parts of grinding aid, wherein the grinding aid consists of triisopropanolamine cyclic borate, coco oleic diethanolamide, borax, triethyl orthoacetate, modified Arabic gum, magnesium stearate and water in a mass ratio of (34-40), (10-16), (17-22), (3-5), (10-14), (0.7-1.5) and (48-53). The anti-permeability cement mortar disclosed by the invention has excellent mechanical properties, high compressive strength and high breaking strength, and meanwhile, the anti-permeability performance and the anti-cracking performance are good. However, the method has the disadvantages of various formula raw materials, complex preparation method and lack of evaluation on the durability and self-shrinkage performance of cement mortar.

CN 111960760A discloses a high-damping modified cement mortar and a preparation method thereof, which comprises the following components in parts by weight: 50-60 parts of cement, 100-120 parts of sand, 25-30 parts of water, 4-6 parts of styrene-acrylic emulsion, 0.2-0.5 part of water reducing agent, 0.1-0.3 part of defoaming agent, 1-3 parts of internal damping additive and 3-7 parts of external damping additive, wherein the internal damping additive is a stearic acid/butadiene rubber compound, and the external damping additive is an erucamide/steel fiber/butadiene rubber compound. The high-damping modified cement mortar provided by the invention has the effect of improving the poor damping effect of the cement mortar. The invention adds a plurality of organic modifiers, the mechanical strength of the mortar is not high, and the compatibility of the mortar is worthy of consideration.

Substances for promoting cement hydration are added into cement mortar, so that the compactness of a hydration product is enhanced, and the mechanical property and durability of the cement mortar are improved.

Disclosure of Invention

In view of the defects of the prior art, the technical problem to be solved by the invention is to provide durable cement mortar which has high mechanical strength, good dry shrinkage deformation performance and good durability.

The improvement of the water resistance and the impermeability of the cement mortar is an important way for improving the durability of the cement mortar. Currently, the most common methods are classified into surface modification and additive modification. The surface hydrophobic modification method is to perform hydrophobic modification on the surface after the concrete is cured so as to form a hydrophobic protective layer on the surface of the concrete, and is generally realized by surface coating or dipping. The methods of surface hydrophobic modification have a number of disadvantages. When the concrete is exposed to the external environment, the surface coating tends to age, the concrete is easy to crack, the surface hydrophobic layer is cracked and peeled off, and the waterproof and anti-permeability performance of the concrete is rapidly reduced. Additive modification may be a more effective way than surface modification. The modifying of the additive is to add the modifier in the stirring process of the concrete, and improve the waterproof and anti-permeability performance of the surface and the interior of the concrete. Therefore, compared with the surface hydrophobic modification method, the concrete prepared by the hydrophobic additive method has better performance and longer service life. The hydrophobic agents currently used are mainly liquid silanes and siloxanes, silane emulsions, hydrophobic stearic acid. The inventor carries out optimization adjustment on the added hydrophobic agent on the basis of modification of the additive, and finds that the introduction of silane or siloxane inhibits the hydration of cement to a certain extent. This is probably because the hydrophobic nature of the silane somewhat weakens the interaction forces between the aggregate and the hydration products at the interface. Stearic acid or stearic acid derivatives are difficult to be uniformly dispersed in a cement mortar system. Therefore, the modification of the existing hydrophobing agent reduces the influence of the hydrophobing agent on cement hydration, improves the dispersion of the hydrophobing agent in mortar, and is an effective way for improving the overall performance of durable cement mortar. Stearic acid is less costly and derivatives are easier to prepare than silanes and siloxanes. According to the invention, stearic acid, magnesium oxide and a surfactant act together to prepare a high-performance modifier, and the high-performance modifier is added into cement slurry.

However, the modifier of the invention is a nano magnesium stearate emulsion formed by heating reaction of stearic acid, magnesium oxide and a surfactant, has good dispersion property and low surface tension when being added into cement slurry, and has a promoting effect on initially hydrated ettringite, so that the cement mortar is integrally hydrophobic and the mechanical property of the cement mortar is improved. But after the modifier is added, the hydration speed of the cement is accelerated, the release of hydration heat is accelerated, and the self-contraction performance of the cement mortar is improved. In order to solve the problem, the invention discovers that the added structured cobaltosic oxide can be used as a template formed by early ettringite through a large number of experiments, delays the release of hydration heat, stabilizes the structure of a hydration product, and reduces the influence of a modifier on the self-shrinkage of cement mortar.

In order to achieve the purpose, the invention provides durable cement mortar which comprises the following raw materials: cement, sand, modifier and water.

Preferably, the durable cement mortar comprises the following raw materials in parts by weight: 20 to 50 portions of cement, 60 to 150 portions of sand, 1 to 3 portions of modifier and 8 to 20 portions of water.

Preferably, the cement is one of ordinary portland cement, slag portland cement and fly ash portland cement.

The sand is common river sand with the grain size of 0.35-0.5 mm.

The preparation method of the modifier comprises the following steps:

(1) Dispersing magnesium oxide in water to form a suspension;

(2) Heating and melting stearic acid, adding a nonionic surfactant and water, then adding ammonia water, and stirring to form a system I; and (2) dropwise adding the turbid liquid obtained in the step (1) into the continuously stirred system I, continuing to react after dropwise adding, and adjusting the solid content after cooling to obtain the modifier.

Further, the preparation method of the modifier comprises the following steps in parts by weight:

(1) Mixing 3-5 parts of magnesium oxide with 20-30 parts of water, treating for 20-60 min under the ultrasonic power of 50-100W, and then continuously stirring to form suspension;

(2) Heating and melting 20-50 parts of stearic acid at 70-90 ℃, adding 1-3 parts of nonionic surfactant and 100-150 parts of water, and stirring for 30-60 min; then adding 0.3-1 part of ammonia water, and continuously stirring and reacting for 30-60 min to form a body system I; dropwise adding the suspension obtained in the step (1) into the system I which is continuously stirred, and continuously stirring and reacting for 30-60 min after completely dropwise adding; naturally cooling to 20-30 ℃, and adjusting the solid content to 20-30% by using water to obtain the modifier.

More preferably, the preparation method of the modifier comprises the following steps:

(1) Mixing soluble metal cobalt salt with an organic solvent, stirring to form a solution, carrying out thermal reaction on the solvent, collecting insoluble substances, washing, drying, calcining, crushing and sieving to obtain cobaltosic oxide;

(2) Dispersing magnesium oxide in water to form a suspension;

(3) Heating and melting stearic acid, adding a nonionic surfactant and water, then adding ammonia water, and stirring to form a system I; and (3) dropwise adding the turbid liquid obtained in the step (2) into the continuously stirred system I, adding the cobaltosic oxide obtained in the step (1) after dropwise adding, continuing to react, cooling, and adjusting the solid content to obtain the modifier.

In some preferred embodiments, the preparation method of the modifier comprises the following steps in parts by weight:

(1) Mixing 0.5-1 part of cobalt nitrate hexahydrate, 20-30 parts of isopropanol and 5-10 parts of glycerol, and stirring for 30-60 min to form a solution; carrying out solvothermal reaction on the solution at 160-180 ℃ for 6-8 h, naturally cooling, collecting insoluble substances, washing, drying, calcining, crushing and sieving to obtain cobaltosic oxide;

(2) Mixing 3-5 parts of magnesium oxide and 20-30 parts of water, treating for 20-60 min under the ultrasonic power of 50-100W, and then continuously stirring to form suspension;

(3) Heating and melting 20-50 parts of stearic acid at 70-90 ℃, adding 1-3 parts of nonionic surfactant and 100-150 parts of water, and stirring for 30-60 min; then adding 0.3-1 part of ammonia water, and continuously stirring and reacting for 30-60 min to form a body system I; dropwise adding the suspension obtained in the step (2) into the system I which is continuously stirred, completely dropwise adding 1-5 parts of cobaltosic oxide prepared in the step (1), and continuously stirring and reacting for 30-60 min; naturally cooling to 20-30 ℃, and adjusting the solid content to 20-30% by using water to obtain the modifier.

Most preferably, the preparation method of the modifier comprises the following steps in parts by weight:

(1) Mixing 0.5-1 part of cobalt nitrate hexahydrate, 0.05-0.1 part of 2-mercapto-1-methylimidazole, 20-30 parts of isopropanol and 5-10 parts of glycerol, and stirring for 30-60 min to form a solution; carrying out solvothermal reaction on the solution at 160-180 ℃ for 6-8 h, naturally cooling, collecting insoluble substances, washing, drying, calcining, crushing and sieving to obtain cobaltosic oxide;

Preferably, the nonionic surfactant in the step (3) is at least one of fatty alcohol-polyoxyethylene ether O-20, fatty alcohol-polyoxyethylene ether O-25 and fatty alcohol-polyoxyethylene ether AEO-9.

The invention has the beneficial effects that:

mixing magnesium oxide and stearic acid, adding a nonionic surfactant, preparing a magnesium stearate emulsion by using simple chemical reaction, and taking the magnesium stearate emulsion as a modifier of cement mortar to obviously improve the hydrophobic properties of the inner and outer surfaces of the mortar; the cobaltosic oxide is added to further improve the hydrophobic property of the mortar, improve the mechanical strength, water resistance and chloride ion resistance of the mortar and improve the shrinkage property of the cement mortar.

Drawings

FIG. 1 is a scanning electron micrograph of cobaltosic oxide prepared according to examples of the present invention and comparative examples;

fig. 1A shows comparative example 2, fig. 1B shows example 2, and fig. 1C shows example 3.

Detailed Description

Introduction of some materials in the examples of the present invention:

cement, ordinary portland cement PO 42.5, available from new cement limited, north of lake.

River sand, a common river sand belonging to grade i sand, was purchased from shijiazhuang zhou lin mineral products ltd.

Fatty alcohol-polyoxyethylene ether AEO-9, available from Shandong sanden New Material science and technology Co.

2-mercapto-1-methylimidazole, available from Shanghai Arlatin Biotechnology Ltd.

The preparation method of the cement mortar test piece comprises the following steps: putting the cement mortar prepared by the method into a stirrer, stirring for 2min at a stirring speed of 80r/min, then filling the cement mortar into a mold, vibrating for 15s while filling the mortar, and scraping the surface of the mold by using a lime cutter after filling; and then, placing the mould with the mortar in an environment with the temperature of 20 ℃ and the relative humidity of 90% for maintenance, demolding after 48 hours, and maintaining until the curing time is 28 days to obtain a cement mortar test piece.

The test piece of 40mm multiplied by 160mm is used for the strength test and the self-contraction test of the mortar; the test piece of 70.7mm multiplied by 70.7mm is used for testing the water absorption of the mortar; a cylindrical test piece having a diameter of 100mm and a height of 50mm was used for the chloride permeability test of the mortar.

Example 1

A durable cement mortar is prepared from cement (20 kg), river sand (60 kg), modifier (1 kg) and water (8.2 kg).

The preparation method of the modifier comprises the following steps:

(1) Mixing 3kg of magnesium oxide with 25kg of water, treating for 30min at an ultrasonic power of 50W and a frequency of 40kHz, and then stirring for 30min at a stirring speed of 350r/min to form a suspension;

(2) Heating and melting 3.5kg of stearic acid at the temperature of 80 ℃, adding 1kg of fatty alcohol-polyoxyethylene ether AEO-9 and 100kg of water, and stirring for 30min at the stirring speed of 350 r/min; then adding 0.5kg of ammonia water, and continuously stirring and reacting for 3min to form a body system I; dropwise adding the suspension obtained in the step (1) into the continuously stirred system I at the dropwise adding speed of 0.5kg/min, and continuously stirring and reacting for 30min after the suspension is completely dropwise added; naturally cooling to 25 ℃, and adjusting the solid content to 25% by using water to obtain the modifier.

Example 2

A durable cement mortar is composed of 20kg of cement, 60kg of river sand, 1kg of modifier and 8.2kg of water.

The preparation method of the modifier comprises the following steps:

(1) Mixing 0.8kg of cobalt nitrate hexahydrate, 25kg of isopropanol and 5kg of glycerol, and stirring at the stirring speed of 450r/min for 30min to form a solution; transferring the solution to a reaction kettle, carrying out solvothermal reaction for 8h at 180 ℃, naturally cooling to 25 ℃, collecting insoluble substances, washing with acetone and water for three times respectively, drying in a constant-temperature oven at 80 ℃ for 6h, transferring to a muffle furnace at 550 ℃ for calcining for 2h, naturally cooling to 25 ℃, crushing, and screening with a 325-mesh screen to obtain cobaltosic oxide;

(2) Mixing 3kg of magnesium oxide with 25kg of water, treating for 30min at an ultrasonic power of 50W and a frequency of 40kHz, and then stirring for 30min at a stirring speed of 350r/min to form a suspension;

(3) Heating and melting 3.5kg of stearic acid at the temperature of 80 ℃, adding 1kg of fatty alcohol-polyoxyethylene ether AEO-9 and 100kg of water, and stirring for 30min at the stirring speed of 350 r/min; then 0.5kg of ammonia water is added, and the mixture is continuously stirred and reacts for 3min to form a body system I; dropwise adding the suspension obtained in the step (2) into the continuously stirred system I at the dropwise adding speed of 0.5kg/min, after completely dropwise adding, adding 2kg of the cobaltosic oxide prepared in the step (1), and continuously stirring and reacting for 30min; naturally cooling to 25 ℃, and adjusting the solid content to 25% by using water to obtain the modifier.

Example 3

The preparation method of the modifier comprises the following steps:

(1) Mixing 0.8kg of cobalt nitrate hexahydrate, 0.05kg of 2-mercapto-1-methylimidazole, 25kg of isopropanol and 5kg of glycerol, and stirring at the stirring speed of 450r/min for 30min to form a solution; transferring the solution to a reaction kettle, carrying out solvothermal reaction for 8h at 180 ℃, naturally cooling to 25 ℃, collecting insoluble substances, washing with acetone and water for three times respectively, drying in a constant-temperature oven at 80 ℃ for 6h, transferring to a muffle furnace at 550 ℃ for calcining for 2h, naturally cooling to 25 ℃, crushing, and screening with a 325-mesh screen to obtain cobaltosic oxide;

(3) Heating 3.5kg of stearic acid for melting at 80 ℃, adding 1kg of fatty alcohol-polyoxyethylene ether AEO-9 and 100kg of water, and stirring for 30min at a stirring speed of 350 r/min; then 0.5kg of ammonia water is added, and the mixture is continuously stirred and reacts for 3min to form a body system I; dropwise adding the suspension obtained in the step (2) into the continuously stirred system I at a dropwise adding rate of 0.5kg/min, adding 2kg of cobaltosic oxide prepared in the step (1) after completely dropwise adding, and continuously stirring and reacting for 30min; naturally cooling to 25 ℃, and adjusting the solid content to 25% by using water to obtain the modifier.

Comparative example 1

The modifier is a suspension of 25wt.% magnesium stearate.

Comparative example 2

A durable cement mortar is prepared from cement (20 kg), river sand (60 kg), modifier (1 kg) and water (8.2 kg)

The modifier comprises the following steps:

(1) Mixing 0.8kg of cobalt nitrate hexahydrate, 0.2kg of urea and 30kg of water, and stirring at the stirring speed of 450r/min for 30min to form a solution; transferring the solution to a reaction kettle, carrying out solvothermal reaction for 8h at 180 ℃, naturally cooling to 25 ℃, collecting insoluble substances, washing with acetone and water for three times respectively, drying in a constant-temperature oven at 80 ℃ for 6h, transferring to a muffle furnace at 550 ℃ for calcining for 2h, naturally cooling to 25 ℃, crushing, and screening with a 325-mesh screen to obtain cobaltosic oxide;

(3) Heating and melting 3.5kg of stearic acid at the temperature of 80 ℃, adding 1kg of fatty alcohol-polyoxyethylene ether AEO-9 and 100kg of water, and stirring for 30min at the stirring speed of 350 r/min; then adding 0.5kg of ammonia water, and continuously stirring and reacting for 3min to form a body system I; dropwise adding the suspension obtained in the step (2) into the continuously stirred system I at a dropwise adding rate of 0.5kg/min, adding 2kg of cobaltosic oxide prepared in the step (1) after completely dropwise adding, and continuously stirring and reacting for 30min; naturally cooling to 25 ℃, and adjusting the solid content to 25% by using water to obtain the modifier.

Test example 1

The compressive strength of cement mortar test pieces of 40mm x 160mm was tested by reference to the test method for cement mortar strength of standard GB/T17671-1999 (ISO method), and the results are shown in Table 1. The components of the conventional mortars in the table are substantially the same as in example 1, with the only difference that no modifier is added.

TABLE 1 Strength test results of Cement mortar

From the results of Table 1, it can be seen that comparative example 1, in which magnesium stearate suspension was added as an improver, rather decreased the compressive strength with respect to the conventional mortar. This is probably due to the hydrophobic nature of magnesium stearate, which somewhat weakens the interaction of the aggregate with the cement in the interfacial transition zone. The compressive strength of example 1 to which the magnesium stearate composite emulsion was added was slightly higher than that of general mortar, probably because the magnesium stearate composite emulsion in the early stage can promote the forward progress of hydration reaction without consuming calcium hydroxide, thereby increasing cement hydration products and slightly improving the strength of cement mortar. In comparative example 2, example 2 and example 3, cobaltosic oxide is also added into the magnesium stearate composite emulsion, so that the compressive strength is further improved. The reason is probably that the cobaltosic oxide can be used as an initial template formed by ettringite to promote hydration products to form a more stable structure, and cobaltosic oxide particles with high mechanical properties can bear part of stress, so that the strength of the mortar test piece is improved. As shown in fig. 1, it can be seen that there is a significant difference in the structure of the cobaltosic oxide of comparative example 2, and example 3. Hydrothermally prepared cobaltosic oxide (fig. 1A, example 1) is in a lamellar aggregated structure; the cobaltosic oxide of example 2 (fig. 1B) appears spherical; example 3 (fig. 1C) is a structured multilayered sheet. Probably due to the structure of cobaltosic oxide, the cement mortar of example 3 has the best compressive strength.

Test example 2

The water contact angle of the test piece may reflect the hydrophilicity of the test piece. And wetting the surface of the object to be detected with water, wherein the contact angle is more than 90 degrees and is hydrophobic. The cement mortar test pieces of 40mm × 40mm × 160mm were cut, and the water contact angles of the inner and outer surfaces of the cement mortar were measured, with the results shown in table 2.

TABLE 2 Water contact Angle of the inner and outer surfaces of the test pieces

	Inner surface water contact angle (°)	Outer surface water contact angle (°)
			Ordinary mortar	26	35
Example 1	83	119
			Example 2	93	128
Example 3	101	134
			Comparative example 1	61	113
Comparative example 2	88	123

As can be seen from the test results of Table 2, both the inner and outer surfaces of the cement mortar without the modifier are hydrophilic. The addition of magnesium stearate in comparative example 1 improves the hydrophilicity of the mortar and reverses the wetting of the outer surface. The hydrophilicity of the mortar test pieces of example 1 to which the magnesium stearate emulsion was added was further improved, but the interior of the mortar was still hydrophilic. The same is true of comparative example 2. The mortars of example 2 and example 3 were both hydrophobic on both the inner and outer surfaces. This may be related to the structure of the cobaltosic oxide. The mortar of comparative example 3 has the best hydrophobicity, which is probably because the addition of 2-mercapto-1-methylimidazole not only improves the structure of cobaltosic oxide, but also enhances the dispersibility thereof in an emulsion system, so that a hydrophobic membrane is more easily formed.

The water absorption of a mortar sample of 70.7mm × 70.7mm × 70.7mm was tested with reference to standard JC 474-2008 mortar and a concrete waterproofing agent. Drying the standard mortar sample and the mortar sample to be tested in a constant-temperature oven at 80 ℃ to constant weight, and respectively weighing and recording the weight m at the moment _t1 And m ₁ (ii) a Then placing the sample into a tank with two steel bars at the bottom, immersing the standard mortar sample and the mortar sample to be tested into water for 35mm in height, keeping the water surface constant, keeping the sample in an environment with the temperature of 20 ℃ and the relative humidity of 90% for 48 hours, taking out the sample, wiping off the water on the surface of the sample, and respectively weighing the recorded weights m of the standard mortar sample and the mortar sample to be tested _t1 And m ₂ (ii) a Calculated Water absorption = (m) ₂ -m ₁ )/(m _t2 -m _t1 ). The results are shown in Table 3.

TABLE 3 Water absorption results for the test pieces

	Water absorption (%)
		Ordinary mortar	4.5
Example 1	2.6
		Example 2	2.1
Example 3	1.8
		Comparative example 1	4.3
Comparative example 2	2.4

As can be seen from the test results of the above table, the cement mortar test piece prepared in example 3 of the present invention has the lowest water absorption, because the inside and outside of the mortar are hydrophobic, water drops are repelled from the surface and are difficult to penetrate into pores, and the water absorption is significantly reduced; the cobaltosic oxide has a certain water retention effect, so that the free water content in the new mortar is reduced, micropores and capillary holes in the hydration and maintenance processes of the cement mortar are reduced, and the passing way of water in the mortar is reduced.

Test example 3

According to the standard of the test method of the long-term performance and the durability of the standard GB/T50082-2009 common concrete, the chloride ion penetration resistance of a cylindrical cement mortar test piece with the diameter of 100mm and the height of 50mm is tested by adopting a rapid chloride ion migration coefficient method. The results are shown in Table 4. The lower the penetration depth, the lower the permeability coefficient, the better the chloride ion resistance.

TABLE 4 results of chloride ion penetration resistance of cement mortar test pieces

From the results in Table 4, it can be seen that the mortar prepared in example 3 of the present invention has the best impermeability, probably because the mortar matrix has a compact structure and good strength, and reduces the chloride ion diffusion channel, significantly reducing the permeability coefficient of chloride ions.

Test example 4

The self-contraction performance of the mortar test piece is tested according to the standard JGJ/T70-2009 building mortar basic performance test method. The results are shown in Table 5.

TABLE 5 self-shrinkage results for cement mortars

	Self-contraction (mu epsilon)
		Ordinary mortar	-536
Example 1	-628
		Example 2	-486
Example 3	-432
		Comparative example 2	-601

From the test results in the table above, it can be seen that the self-shrinkage rate of the test piece prepared by adding the magnesium stearate emulsion in example 1 is increased, which is probably because the hydrophobicity of the mortar test piece is enhanced, the magnesium stearate promotes the hydration reaction, and the self-drying effect in the mortar is more obvious due to the consumption of water. Comparative example 2 also added hydrothermally prepared cobaltosic oxide, the self-shrinking property was improved, probably because the cobaltosic oxide acts as an ettringite template to refine the pore structure. Example 3, which incorporates 2-mercapto-1-methylimidazole modified cobaltosic oxide and magnesium stearate emulsion, has the best self-shrinking properties, probably due to the good dispersibility, overall mortar hydrophobicity, refined pore structure, enhanced capillary pressure and internal stress, thus significantly improving the self-shrinking properties of the mortar.

Claims

1. The durable cement mortar is characterized by comprising the following raw materials: cement, sand, modifier and water.

2. The durable cement mortar of claim 1, comprising the following raw materials: 20-50 parts of cement, 60-150 parts of sand, 1-3 parts of modifier and 8-20 parts of water.

3. The durable cement mortar of claim 2, wherein said cement is one of ordinary portland cement, portland slag cement, and portland fly ash cement.

4. The durable cement mortar of claim 2, wherein the sand is general river sand having a particle size of 0.35 to 0.5mm.

5. The durable cement mortar of claim 2, wherein said modifier is prepared by a process comprising the steps of:

(1) Dispersing magnesium oxide in water to form a suspension;

(2) Heating and melting stearic acid, adding a nonionic surfactant and water, then adding ammonia water, and stirring to form a system I; and (3) dropwise adding the suspension obtained in the step (1) into the continuously stirred system I, continuing to react after dropwise adding, and adjusting the solid content after cooling to obtain the modifier.

6. The durable cement mortar of claim 5, wherein the modifier is prepared by the following steps in parts by weight:

(1) Mixing 3-5 parts of magnesium oxide and 20-30 parts of water, treating for 20-60 min under the ultrasonic power of 50-100W, and then continuously stirring to form suspension;

7. The durable cement mortar of claim 2, wherein said modifier is prepared by a process comprising the steps of:

(2) Dispersing magnesium oxide in water to form a suspension;

(3) Heating and melting stearic acid, adding a nonionic surfactant and water, then adding ammonia water, and stirring to form a system I; and (3) dropwise adding the suspension obtained in the step (2) into the system I which is continuously stirred, adding the cobaltosic oxide obtained in the step (1) after dropwise adding, continuing to react, cooling, and adjusting the solid content to obtain the modifier.

8. The durable cement mortar of claim 7, wherein said modifier is prepared by a method comprising the steps of, in parts by weight:

(3) Heating and melting 20-50 parts of stearic acid at 70-90 ℃, adding 1-3 parts of nonionic surfactant and 100-150 parts of water, and stirring for 30-60 min; then adding 0.3-1 part of ammonia water, and continuously stirring and reacting for 30-60 min to form a body system I; dropwise adding the suspension obtained in the step (2) into the continuously stirred system I, completely dropwise adding 1-5 parts of cobaltosic oxide prepared in the step (1), and continuously stirring for reaction for 30-60 min; naturally cooling to 20-30 ℃, and adjusting the solid content to 20-30% by using water to obtain the modifier.

9. The durable cement mortar of any one of claims 5 to 8, wherein said nonionic surfactant is at least one of fatty alcohol-polyoxyethylene ether O-20, fatty alcohol-polyoxyethylene ether O-25, fatty alcohol-polyoxyethylene ether AEO-9.