Polymer modified cement stabilized macadam mixture and preparation method thereof

Abstract

The invention relates to the technical field of cement mixtures, and provides a polymer modified cement stabilized macadam mixture and a preparation method thereof.The polymer modified cement stabilized macadam mixture is prepared from, by weight, 5-10 parts of cement, 3-6 parts of functional auxiliaries, 105-125 parts of aggregate and 3-6 parts of water; the functional auxiliary agent comprises dispersible latex powder, cellulose ether and 2-acrylamide-2-methylpropanesulfonic acid in a mass ratio of 0.5: 1: (1-2). According to the technical scheme, the problem that the cement stabilized macadam mixture in the prior art is easy to shrink and crack is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cement mixtures, and specifically, to a polymer-modified cement-stabilized macadam mixture and a preparation method thereof. Background Art

[0002] The semi-rigid base asphalt pavement is the most typical structure in highway construction, and more than 95% of expressways adopt the semi-rigid base asphalt pavement.

[0003] The semi-rigid base asphalt pavement composed of cement-stabilized macadam mixture has the characteristics of good stability, high overall strength, high stiffness, strong resistance to permanent deformation, resistance to fatigue failure of vehicle load, and can adapt to heavy traffic. Moreover, the cement-stabilized macadam mixture base is cheap in cost and convenient in material collection. Therefore, the cement-stabilized macadam mixture has become the most widely used semi-rigid base material in the construction of high-grade highways. However, the cement-stabilized macadam mixture base also has certain deficiencies. After the base construction is completed, adverse conditions such as inadequate maintenance and large changes in external temperature difference will cause the base to generate shrinkage cracks. Additionally, under the action of vehicle load at the crack, the dry shrinkage and temperature shrinkage cracks will further induce the cracking of the asphalt surface layer, generating reflective cracks penetrating the road surface, and ultimately leading to a reduction in the overall strength of the road and affecting the service life of the road. Therefore, the shrinkage cracking of the cement-stabilized macadam mixture is an urgent problem to be solved in current practical engineering. Summary of the Invention

[0004] The present invention provides a polymer-modified cement-stabilized macadam mixture and a preparation method thereof, which solve the problem of easy shrinkage cracking existing in the cement-stabilized macadam mixture in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a polymer-modified cement-stabilized macadam mixture, which comprises the following components in parts by weight: 5 - 10 parts of cement, 3 - 6 parts of functional additives, 105 - 125 parts of aggregate, and 3 - 6 parts of water; The functional additives include redispersible latex powder, cellulose ether, and 2-acrylamide-2-methylpropanesulfonic acid with a mass ratio of 0.5:1:1 - 2.

[0006] As a further technical solution, the redispersible latex powder includes ethylene-vinyl acetate copolymer latex powder.

[0007] In the present invention, the redispersible latex powder significantly improves the adhesion between cement and macadam, enabling the mixture to form a more compact overall structure. Among them, the redispersible latex powder includes ethylene-vinyl acetate copolymer latex powder, which is made by emulsion polymerization and spray drying of ethylene and vinyl acetate, and has excellent adhesion and dispersibility in the cement-stabilized macadam mixture.

[0008] As a further technical solution, the aggregate includes aggregate A and aggregate B with a mass ratio of 1:3 to 3:1; The aggregate A includes crushed stones with a particle size of 4.75 mm ≤ particle size ≤ 31.5 mm; The aggregate B includes crushed stones with a particle size of 0.075 mm ≤ particle size ≤ 2.36 mm.

[0009] In the present invention, the aggregate B is crushed stones with a particle size of 0.075 mm ≤ particle size ≤ 2.36 mm. The smaller particle size enables it to fill the voids between larger particles in the mixture, improving the overall density. The aggregate A includes crushed stones with a particle size of 4.75 mm ≤ particle size ≤ 31.5 mm. The larger particle size gives the mixture better skeleton support, enhancing its load-bearing capacity. Aggregate A and aggregate B are used together, and they interlock with each other to form a stable skeleton structure, effectively dispersing and bearing the vertical pressure, preventing the road surface from excessive deformation or damage under heavy pressure, and ensuring the load-bearing capacity of the polymer-modified cement stabilized macadam mixture when applied to roads.

[0010] As a further technical solution, the cellulose ether includes one or more of methyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.

[0011] As a further technical solution, the cellulose ether is a modified cellulose ether; The preparation method of the modified cellulose ether includes the following steps: A1. Mix the cellulose ether and the alkali solution to obtain a mixture; A2. Add halogenated decane to the mixture, filter, wash, and dry to obtain the modified cellulose ether.

[0012] In the present invention, the negatively charged cellulose ether after alkalization treatment can attack the carbon atom in the halogenated decane, and the halogen atom leaves as a leaving group, thereby introducing a decyl group into the cellulose ether molecular chain to achieve the modification of the cellulose ether and obtain the modified cellulose ether. After the reaction is completed, the generated modified cellulose ether solid is separated by filtration, and the impurities such as unreacted raw materials, by-products, and alkali solution adsorbed on the surface of the modified cellulose ether are removed by washing. Finally, the solvent remaining after washing is removed by drying. The finally prepared modified cellulose ether is added to the mixture, which is beneficial for the better dispersion of the cellulose ether in the macadam mixture system, improving its interaction with components such as cement particles. While reducing the shrinkage cracking of the cement stabilized macadam mixture, it also improves the strength of the cement stabilized macadam mixture.

[0013] As a further technical solution, the mass ratio of the cellulose ether to the alkali solution is 1 to 10:100.

[0014] As a further technical solution, the alkali solution comprises the following components in parts by weight: 100 parts of an alcohol solvent, 5-6 parts of an alkali metal hydroxide, and 1-3 parts of urea.

[0015] As a further technical solution, the alcohol solvent comprises one or more of ethanol and isopropanol.

[0016] As a further technical solution, the alkali metal hydroxide comprises one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0017] As a further technical solution, the halogenated decane comprises one or more of fluorinated decane, chlorinated decane, and iodinated decane.

[0018] As a further technical solution, the mass ratio of the cellulose ether to the halogenated decane is 10:3-5.

[0019] As a further technical solution, in step A1, the mixing time is 20-25 h, and the temperature is 18-20 °C.

[0020] As a further technical solution, in step A2, the mixing time is 6-8 h, and the temperature is 60-65 °C.

[0021] The present invention also provides a method for preparing the polymer-modified cement stabilized macadam mixture, comprising the following steps: Pre-mix the functional aid and the aggregate, and then mix with the remaining components of the polymer-modified cement stabilized macadam mixture to obtain the polymer-modified cement stabilized macadam mixture.

[0022] As a further technical solution, the pre-mixing time is 60-80 s, and the mixing time is 80-100 s.

[0023] In the present invention, the functional aid is fully pre-mixed with the aggregate to ensure that the functional aid is fully dispersed and evenly attached to the surface of the aggregate, enhancing the bonding effect between the two. After the pre-mixing is completed, it is further blended with the remaining components, which is beneficial to obtaining a homogeneous polymer-modified cement stabilized macadam mixture.

[0024] The working principle and beneficial effects of the present invention are as follows: In the present invention, cement is used as the basic cementitious material to form a strong skeleton structure with the aggregate. Among them, the functional aids are redispersible latex powder, cellulose ether, and 2-acrylamido-2-methylpropanesulfonic acid. During the hydration process of cement, the redispersible latex powder forms a polymer film between the particles, enhancing the bonding force between the particles. The cellulose ether improves the microstructure of the cement stone. The combination of redispersible latex powder, cellulose ether, and 2-acrylamido-2-methylpropanesulfonic acid compensates for the shrinkage deformation of the macadam mixture and inhibits the generation of cracks. Detailed implementation mode

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0026] In the following embodiments and comparative examples, the type of the redispersible latex powder is SWF-05, and the cement is Portland cement P.O42.5; Aggregate A is crushed stone with a particle size of 4.75~31.5mm. Among them, the passing rate of crushed stone with a sieve hole of 2.36mm is 0%, the passing rate of crushed stone with a sieve hole of 4.75mm is 27%, the passing rate of crushed stone with a sieve hole of 9.5mm is 48%, the passing rate of crushed stone with a sieve hole of 19mm is 77%, and the passing rate of crushed stone with a sieve hole of 31.5mm is 100%; Aggregate B is crushed stone with a particle size of 0.075~2.36mm. Among them, the passing rate of crushed stone with a sieve hole of 0.075mm is 10%, the passing rate of crushed stone with a sieve hole of 0.6mm is 35%; the passing rate of crushed stone with a sieve hole of 2.36mm is 100%.

[0027] Example 1 The polymer-modified cement stabilized macadam mixture comprises the following components in parts by weight: 5 parts of cement, 3 parts of functional additives, 105 parts of aggregate, and 3 parts of water; the aggregate is aggregate A and aggregate B with a mass ratio of 1:3; The functional additive is a redispersible latex powder, hydroxypropyl methylcellulose, and 2-acrylamide-2-methylpropanesulfonic acid with a mass ratio of 0.5:1:1; The preparation method of the polymer-modified cement stabilized macadam mixture comprises the following steps: After premixing the functional additive and the aggregate for 60s, mix them with the remaining components of the polymer-modified cement stabilized macadam mixture for 80s to obtain the polymer-modified cement stabilized macadam mixture.

[0028] Example 2 The polymer-modified cement stabilized macadam mixture comprises the following components in parts by weight: 10 parts of cement, 6 parts of functional additives, 125 parts of aggregate, and 6 parts of water; the aggregate is aggregate A and aggregate B with a mass ratio of 3:1; The functional additive is a redispersible latex powder, hydroxypropyl methylcellulose, and 2-acrylamide-2-methylpropanesulfonic acid with a mass ratio of 0.5:1:2; The preparation method of the polymer-modified cement stabilized macadam mixture comprises the following steps: After premixing the functional additive and the aggregate for 80 s, mix them with the remaining components of the polymer-modified cement stabilized macadam mixture for 100 s to obtain the polymer-modified cement stabilized macadam mixture.

[0029] Example 3 The polymer-modified cement stabilized macadam mixture comprises the following components in parts by weight: 8 parts of cement, 5 parts of functional additive, 118 parts of aggregate, and 5 parts of water; the aggregate is aggregate A and aggregate B with a mass ratio of 2:1; The functional additive is redispersible latex powder, hydroxypropyl methylcellulose, and 2-acrylamide-2-methylpropanesulfonic acid with a mass ratio of 0.5:1:1; The preparation method of the polymer-modified cement stabilized macadam mixture comprises the following steps: After premixing the functional additive and the aggregate for 70 s, mix them with the remaining components of the polymer-modified cement stabilized macadam mixture for 90 s to obtain the polymer-modified cement stabilized macadam mixture.

[0030] Example 4 The difference between this example and Example 3 is only that the hydroxypropyl methylcellulose is modified hydroxypropyl methylcellulose, and the preparation method of the modified hydroxypropyl methylcellulose comprises the following steps: A1. Mix hydroxypropyl methylcellulose and an alkali solution at a mass ratio of 1:100 at 18 °C for 25 h to obtain a mixture; A2. Add 1-chlorodecane to the above mixture and mix at 65 °C for 6 h, filter, wash, and dry to obtain modified hydroxypropyl methylcellulose; the mass ratio of hydroxypropyl methylcellulose to 1-chlorodecane is 10:3; Among them, the alkali solution comprises the following components in parts by weight: 100 parts of ethanol, 5 parts of sodium hydroxide, and 1 part of urea.

[0031] Example 5 The difference between this example and Example 3 is only that the hydroxypropyl methylcellulose is modified hydroxypropyl methylcellulose, and the preparation method of the modified hydroxypropyl methylcellulose comprises the following steps: A1. Mix hydroxypropyl methylcellulose and an alkali solution at a mass ratio of 10:100 at 20 °C for 20 h to obtain a mixture; A2. Add 1-bromodecane to the above mixture and mix at 60 °C for 8 h, filter, wash, and dry to obtain modified hydroxypropyl methylcellulose; the mass ratio of hydroxypropyl methylcellulose to 1-chlorodecane is 2:1; Among them, the alkali solution comprises the following components in parts by weight: 100 parts of isopropanol, 6 parts of potassium hydroxide, and 3 parts of urea.

[0032] Example 6 The difference between this example and Example 5 is only that 1-bromodecane is replaced by 1-bromododecane.

[0033] Example 7 The difference between this example and Example 5 is only that 1-bromodecane is replaced by 1-bromooctane.

[0034] Comparative Example 1 The difference between this comparative example and Example 3 is only that the functional additive is redispersible latex powder and 2-acrylamido-2-methylpropanesulfonic acid with a mass ratio of 0.5:1.

[0035] Comparative Example 2 The difference between this comparative example and Example 3 is only that the functional additive is redispersible latex powder and hydroxypropyl methylcellulose with a mass ratio of 0.5:1.

[0036] Comparative Example 3 The difference between this comparative example and Example 3 is only that the functional additive is hydroxypropyl methylcellulose and 2-acrylamido-2-methylpropanesulfonic acid with a mass ratio of 1:1.

[0037] Experimental Example 1 According to the standard JTG 3441-2024 "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering", the shrinkage cracking performance tests were carried out on the polymer modified cement stabilized macadam mixtures prepared in Examples 1 to 7 and Comparative Examples 1 to 3 respectively. Among them, the thermal shrinkage coefficient is the average thermal shrinkage coefficient in the temperature shrinkage range of -25 to 60 °C. The temperature shrinkage range of -25 to 60 °C is divided into -25 to -10 °C, -10 to 0 °C, 0 to 15 °C, 15 to 30 °C, 30 to 45 °C, and 45 to 60 °C. The results are shown in Table 1 below.

[0038] Table 1 Test Results of Shrinkage Cracking Performance

[0039] Compared with Comparative Examples 1 to 3, the dry shrinkage coefficient and thermal shrinkage coefficient of the polymer modified cement stabilized macadam mixtures prepared in Examples 1 to 7 are lower, indicating that the compounding of redispersible latex powder, cellulose ether and 2-acrylamido-2-methylpropanesulfonic acid, and the modified cellulose ether can reduce the shrinkage of the polymer modified cement stabilized macadam mixture.

[0040] Experimental Example 2 According to the standard JTG 3441-2024 "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering", the compressive strength and splitting strength tests were carried out on the polymer modified cement stabilized macadam mixtures prepared in Examples 3 to 7 respectively. The results are shown in Table 2 below.

[0041] Table 2 Test Results of Strength

[0042] Compared with Example 3 and Examples 6-7, the unconfined compressive strength and splitting strength of the polymer-modified cement stabilized macadam mixture prepared in Examples 4-5 are higher, indicating that the strength of the polymer-modified cement stabilized macadam mixture prepared by modifying cellulose ether with halogenated decane is more excellent.

[0043] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Polymer modified cement stabilized gravel mixture, characterized in that: The invention comprises the following components in parts by weight: 5-10 parts of cement, 3-6 parts of functional additives, 105-125 parts of aggregates, and 3-6 parts of water; The functional additives include dispersible latex powder, cellulose ether and 2-acrylamide-2-methylpropane sulfonic acid in a mass ratio of 0.5:1:1-2.

2. The polymer-modified cement-stabilized crushed stone mixture according to claim 1, characterized in that: The aggregate includes aggregate A and aggregate B in a mass ratio of 1:3 to 3:1; The aggregate A comprises crushed stone with a particle size of 4.75 mm ≤ ≤ 31.5 mm; The aggregate B includes crushed stones with a particle size of 0.075 mm ≤ ≤ 2.36 mm.

3. The polymer-modified cement-stabilized crushed stone mixture according to claim 1, characterized in that: The cellulose ether includes one or more of methyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl cellulose.

4. The polymer-modified cement-stabilized crushed stone mixture according to claim 1, characterized in that: The cellulose ether is a modified cellulose ether; The preparation method of the modified cellulose ether comprises the following steps: A1, mixing cellulose ether and an alkaline solution to obtain a mixture; A2. Add halogenated decane to the mixture, mix, filter, wash, and dry to obtain modified cellulose ether.

5. The polymer-modified cement-stabilized crushed stone mixture according to claim 4, characterized in that: The mass ratio of the cellulose ether to the alkaline solution is 1-10:

100.

6. The polymer-modified cement-stabilized crushed stone mixture according to claim 4, characterized in that: The alkaline solution comprises the following components in parts by weight: 100 parts of an alcohol solvent, 5 to 6 parts of an alkali metal hydroxide, and 1 to 3 parts of urea.

7. The polymer-modified cement-stabilized crushed stone mixture according to claim 4, characterized in that: The mass ratio of the cellulose ether to the halogenated decane is 10:3-5.

8. The polymer-modified cement-stabilized crushed stone mixture according to claim 4, characterized in that: In step A1, the mixing time is 20-25 hours and the temperature is 18-20°C.

9. The polymer-modified cement-stabilized crushed stone mixture according to claim 4, characterized in that: In step A2, the mixing time is 6-8 hours and the temperature is 60-65°C.

10. The method for preparing a polymer-modified cement-stabilized crushed stone mixture according to any one of claims 1 to 9, characterized in that: The following steps are involved: After the functional additive and aggregate are premixed, they are mixed with the remaining components of the polymer-modified cement-stabilized crushed stone mixture to obtain the polymer-modified cement-stabilized crushed stone mixture.

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