A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP and its preparation method

Abstract

This invention relates to the field of road engineering materials technology, and proposes a shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP and its preparation method. The SAP-added shrinkage-reducing and crack-resistant cement-stabilized crushed stone comprises the following components by weight: 100 parts crushed stone, 5 parts cement, 5-6 parts water, and 0.01-0.03 parts sodium polyacrylate; the sodium polyacrylate includes a first sodium polyacrylate and a second sodium polyacrylate, the first sodium polyacrylate having a particle size of 30-80 mesh, and the second sodium polyacrylate having a particle size of 90-150 mesh, with the mass of the first sodium polyacrylate being less than the mass of the second sodium polyacrylate. This technical solution solves the problem of easy shrinkage and cracking of cement-stabilized crushed stone base courses in related technologies.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, specifically to a shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP and its preparation method. Background Technology

[0002] Semi-rigid base course refers to an inorganic binder-stabilized base course with a certain tensile strength, laid during road construction. In the road structure, the semi-rigid base course lies below the pavement surface layer, effectively distributing the load from the surface layer, reducing subgrade settlement and deformation, thereby improving the overall stability and durability of the road.

[0003] Cement-stabilized crushed stone base course, as a type of semi-rigid base course, possesses advantages such as good water stability and high strength, and is widely used in road engineering. However, cement-stabilized crushed stone base course materials lack flexibility and are easily affected by humidity and temperature changes, making them prone to drying shrinkage cracks and temperature shrinkage cracks. These cracks can then lead to reflective cracking in cement-stabilized crushed stone base course asphalt pavements, disrupting the continuity and integrity of the pavement. Therefore, improving the shrinkage and crack resistance properties of cement-stabilized crushed stone base courses is of great significance for preventing cracking in cement-stabilized crushed stone base course asphalt pavements. Summary of the Invention

[0004] This invention proposes a shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP and its preparation method, which solves the problem of easy shrinkage and cracking of cement-stabilized crushed stone base layers in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, comprising the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 5-6 parts water, 0.01-0.03 parts sodium polyacrylate; The sodium polyacrylate includes a first sodium polyacrylate and a second sodium polyacrylate. The first sodium polyacrylate has a particle size of 30-80 mesh. The particle size of the second sodium polyacrylate is 90-150 mesh. The mass of the first sodium polyacrylate is less than the mass of the second sodium polyacrylate.

[0006] In this invention, two different particle sizes of sodium polyacrylate work synergistically, resulting in lower porosity after water release and improved density of cement-stabilized crushed stone. Compared with sodium polyacrylate of a single particle size, it can not only improve the 7-day and 28-day compressive strength of cement-stabilized crushed stone, but also improve the 3-day compressive strength, thus solving the problem of reduced 3-day compressive strength caused by adding sodium polyacrylate to cement-stabilized crushed stone in the prior art.

[0007] As a further technical solution, the mass ratio of the first sodium polyacrylate to the second sodium polyacrylate is 1:4~9.

[0008] In this invention, when the mass ratio of the first sodium polyacrylate to the second sodium polyacrylate is 1:4~9, the water loss rate and drying shrinkage strain of cement-stabilized crushed stone are further reduced.

[0009] As a further technical solution, the particle size of the first sodium polyacrylate is 50-80 mesh.

[0010] In this invention, when the particle size of the first sodium polyacrylate is 50-80 mesh, the 3d compressive strength of cement-stabilized crushed stone is further improved.

[0011] As a further technical solution, the particle size of the second sodium polyacrylate is 100~120 mesh.

[0012] In this invention, when the particle size of the second sodium polyacrylate is 100-120 mesh, the 3d compressive strength of cement-stabilized crushed stone is further improved.

[0013] As a further technical solution, the crushed stone, by mass percentage, consists of crushed stone of the following particle sizes: Crushed stone with a particle size ≤ 5mm: 25%~30%; crushed stone with a particle size of 5mm < ≤ 10mm: 20%~35%; crushed stone with a particle size of 10mm < ≤ 20mm: 25%~35%; crushed stone with a particle size of 20mm < ≤ 30mm: 10%~20%.

[0014] In this invention, the crushed stone is graded and a dense skeleton gradation is selected, which improves the uniformity of the mixture and gives the cement-stabilized crushed stone better mechanical properties.

[0015] As a further technical solution, the method also includes 0.002~0.02 parts of toughening agent, wherein the toughening agent comprises the following components in parts by weight: 5-15 parts polyacrylamide, 1-5 parts tartaric acid, 1-3 parts titanate coupling agent, and 30-50 parts sericite.

[0016] In this invention, a toughening agent is added to cement-stabilized crushed stone. The toughening agent, in combination with polyacrylamide, tartaric acid, titanate coupling agent, and sericite, further reduces the drying shrinkage strain of cement-stabilized crushed stone and also improves the 3d compressive strength, 7d compressive strength, and 28d compressive strength of cement-stabilized crushed stone.

[0017] As a further technical solution, the mass ratio of polyacrylamide, tartaric acid, titanate coupling agent, and sericite in the toughening agent is 10:2:1:40.

[0018] In this invention, when the mass ratio of polyacrylamide, tartaric acid, titanate coupling agent, and sericite in the toughening agent is 10:2:1:40, the 3-day compressive strength, 7-day compressive strength, and 28-day compressive strength of cement-stabilized crushed stone are further improved.

[0019] As a further technical solution, the mass ratio of the toughening agent to the sodium polyacrylate is 1:2~3.

[0020] In this invention, when the mass ratio of toughening agent to sodium polyacrylate is 1:2~3, the toughening agent and sodium polyacrylate work synergistically to further reduce the drying shrinkage strain of cement-stabilized crushed stone.

[0021] As a further technical solution, the toughening agent is prepared by mixing polyacrylamide, tartaric acid, titanate coupling agent and sericite to obtain the toughening agent.

[0022] This invention also proposes a method for preparing the aforementioned SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone, comprising the following steps: S1. Mix cement with sodium polyacrylate to obtain premix one; S2. Mix the crushed stone with the second sodium polyacrylate to obtain premix two; S3. Mix premix one and premix two with water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

[0023] In this invention, during the preparation of cement-stabilized crushed stone, cement is first mixed with a first sodium polyacrylate, and crushed stone is mixed with a second sodium polyacrylate to obtain two premixes. The two premixes are then mixed with water, which promotes the effectiveness of sodium polyacrylate and further reduces the water loss rate and drying shrinkage strain of cement-stabilized crushed stone.

[0024] The working principle and beneficial effects of this invention are as follows: In this invention, two types of sodium polyacrylate with different particle sizes are added to cement-stabilized crushed stone. Both types of sodium polyacrylate can retain moisture during mixing. During curing, the moisture in the cement-stabilized crushed stone continuously evaporates, while the two types of sodium polyacrylate continuously release water at different rates and degrees. This continuously moistens the interior of the dried cement-stabilized crushed stone, promoting cement hydration to form calcium carbonate and ettringite, thus increasing the strength of the cement-stabilized crushed stone. Furthermore, the hydration products can fill the micro-cracks generated during drying, effectively controlling the shrinkage and crack formation of the cement-stabilized crushed stone. Therefore, adding two types of sodium polyacrylate with different particle sizes significantly reduces the water loss rate and drying shrinkage strain of cement-stabilized crushed stone, solving the problem of easy shrinkage and cracking in cement-stabilized crushed stone base layers. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following examples and comparative examples, P·O42.5 cement was selected; The specifications for sodium polyacrylate are as follows: 30 mesh sodium polyacrylate, water absorption ratio (distilled water) 410 times; 50 mesh sodium polyacrylate, water absorption ratio (distilled water) 400 times; 80 mesh sodium polyacrylate, water absorption ratio (distilled water) 350 times; 90 mesh sodium polyacrylate, water absorption ratio (distilled water) 320 times; 100 mesh sodium polyacrylate, water absorption ratio (distilled water) 280 times; 120 mesh sodium polyacrylate, water absorption ratio (distilled water) 250 times; 150 mesh sodium polyacrylate, water absorption ratio (distilled water) 230 times. The polyacrylamide is an anionic polyacrylamide with a weight-average molecular weight of 8 million. The titanate coupling agent is model TM-7.

[0027] Example 1 A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, comprising the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 5 parts water, 0.004 parts sodium polyacrylate (first type), 0.006 parts sodium polyacrylate (second type). The first sodium polyacrylate has a particle size of 30 mesh, and the second sodium polyacrylate has a particle size of 90 mesh; By weight percentage, the crushed stone consists of crushed stone of the following particle sizes: Crushed stone with a particle size ≤ 5mm: 25%; crushed stone with a particle size of 5mm < ≤ 10mm: 20%; crushed stone with a particle size of 10mm < ≤ 20mm: 35%; crushed stone with a particle size of 20mm < ≤ 30mm: 20%.

[0028] After mixing crushed stone, cement, and water, sodium first and sodium second polyacrylate are added at a rate of 50 g / h to obtain shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP.

[0029] Example 2 A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, comprising the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 6 parts water, 0.012 parts first sodium polyacrylate, 0.018 parts second sodium polyacrylate. The first sodium polyacrylate has a particle size of 80 mesh, and the second sodium polyacrylate has a particle size of 150 mesh. By weight percentage, the crushed stone consists of crushed stone of the following particle sizes: 30% of the crushed stone has a particle size ≤ 5mm; 35% has a particle size ≤ 10mm; 25% has a particle size ≤ 20mm; and 10% has a particle size ≤ 30mm.

[0030] After mixing crushed stone, cement, and water, sodium first and sodium second polyacrylate are added at a rate of 60 g / h to obtain shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP.

[0031] Example 3 The only difference between this embodiment and Embodiment 1 is that the first sodium polyacrylate has a weight percentage of 0.0005 parts and the second sodium polyacrylate has a weight percentage of 0.0095 parts.

[0032] Example 4 The only difference between this embodiment and Embodiment 1 is that the first sodium polyacrylate has a weight percentage of 0.001 parts and the second sodium polyacrylate has a weight percentage of 0.009 parts.

[0033] Example 5 The only difference between this embodiment and Embodiment 1 is that the first sodium polyacrylate has a weight percentage of 0.002 parts and the second sodium polyacrylate has a weight percentage of 0.008 parts.

[0034] Example 6 The only difference between this embodiment and Example 1 is that the particle size of the first sodium polyacrylate is 50 mesh.

[0035] Example 7 The only difference between this embodiment and Example 1 is that the particle size of the second sodium polyacrylate is 100 mesh.

[0036] Example 8 The only difference between this embodiment and Example 1 is that the particle size of the second sodium polyacrylate is 120 mesh.

[0037] Example 9 A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, comprising the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 5 parts water, 0.004 parts first sodium polyacrylate, 0.006 parts second sodium polyacrylate, and 0.002 parts toughening agent; The first sodium polyacrylate has a particle size of 30 mesh, and the second sodium polyacrylate has a particle size of 90 mesh; The toughening agent is prepared by the following method: 5 parts polyacrylamide, 1 part tartaric acid, 1 part titanate coupling agent and 30 parts sericite are mixed and ground to a specific surface area of ​​500-550 m². 2 / kg; By weight percentage, the crushed stone consists of crushed stone of the following particle sizes: Crushed stone with a particle size ≤ 5mm: 25%; crushed stone with a particle size of 5mm < ≤ 10mm: 20%; crushed stone with a particle size of 10mm < ≤ 20mm: 35%; crushed stone with a particle size of 20mm < ≤ 30mm: 20%.

[0038] After mixing crushed stone, cement, and water, sodium polyacrylate and sodium polyacrylate are added at a rate of 50 g / h, and toughening agent is added at a rate of 50 g / h to obtain shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP.

[0039] Example 10 A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, comprising the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 6 parts water, 0.012 parts first sodium polyacrylate, 0.018 parts second sodium polyacrylate, and 0.02 parts toughening agent; The first sodium polyacrylate has a particle size of 80 mesh, and the second sodium polyacrylate has a particle size of 150 mesh. The toughening agent comprises the following components in parts by weight: 15 parts polyacrylamide, 5 parts tartaric acid, 3 parts titanate coupling agent, and 50 parts sericite. By weight percentage, the crushed stone consists of crushed stone of the following particle sizes: 30% of the crushed stone has a particle size ≤ 5mm; 35% has a particle size ≤ 10mm; 25% has a particle size ≤ 20mm; and 10% has a particle size ≤ 30mm.

[0040] After mixing crushed stone, cement, and water, sodium polyacrylate and sodium polyacrylate are added at a rate of 60 g / h, and toughening agent is added at a rate of 60 g / h to obtain shrinkage-reducing and crack-resistant cement-stabilized crushed stone with SAP.

[0041] Example 11 The only difference between this embodiment and Embodiment 9 is that the toughening agent is 0.003 parts by weight.

[0042] Example 12 The only difference between this embodiment and Embodiment 9 is that the toughening agent is 0.005 parts by weight.

[0043] Example 13 The only difference between this embodiment and Embodiment 9 is that the toughening agent is 0.01 parts by weight.

[0044] Example 14 The difference between this embodiment and Embodiment 12 is that the toughening agent includes the following components in parts by weight: 10 parts polyacrylamide, 2 parts tartaric acid, 1 part titanate coupling agent, 40 parts sericite; Example 15 The only difference between this embodiment and Embodiment 1 is that the preparation method of SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone includes the following steps: S1. Add sodium polyacrylate at a rate of 50g / h to the cement and mix evenly to obtain premix one. S2. Add the second sodium polyacrylate to the crushed stone at a rate of 50 g / h and mix evenly to obtain premix two; S3. Mix premix one and premix two with water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

[0045] Example 16 The only difference between this embodiment and Embodiment 1 is that the preparation method of SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone includes the following steps: S1. Add the second sodium polyacrylate at a rate of 50g / h to the cement and mix evenly to obtain premix one; S2. Add sodium polyacrylate at a rate of 50 g / h to the crushed stone and mix evenly to obtain premix two; S3. Mix premix one and premix two with water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

[0046] Example 17 The only difference between this embodiment and Embodiment 1 is that the preparation method of SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone includes the following steps: S1. Add the first sodium polyacrylate and the second sodium polyacrylate mixture to the cement at a rate of 50g / h and mix evenly to obtain premix one. S2. Mix premix 1 with crushed stone and water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

[0047] Example 18 The only difference between this embodiment and Embodiment 1 is that the preparation method of SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone includes the following steps: S1. Add the first sodium polyacrylate and the second sodium polyacrylate to the crushed stone at a rate of 50g / h and mix evenly to obtain premix one. S2. Mix premix 1 with cement and water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

[0048] Comparative Example 1 The only difference between this comparative example and Example 1 is that no second sodium polyacrylate was added, while the weight of the first sodium polyacrylate added was 0.01 parts.

[0049] Comparative Example 2 The only difference between this comparative example and Example 1 is that the first sodium polyacrylate was not added, and the weight of the second sodium polyacrylate was 0.01 parts.

[0050] Comparative Example 3 The only difference between this comparative example and Example 1 is that the weight of the first sodium polyacrylate added is 0.006 parts, and the weight of the second sodium polyacrylate added is 0.004 parts.

[0051] Comparative Example 4 The only difference between this comparative example and Example 1 is that the weight of the first sodium polyacrylate added is 0.005 parts, and the weight of the second sodium polyacrylate added is 0.005 parts.

[0052] Comparative Example 5 The only difference between this comparative example and Example 1 is that neither the first sodium polyacrylate nor the second sodium polyacrylate was added.

[0053] The following performance tests were conducted on the cement-stabilized crushed stone obtained in Examples 1-18 and Comparative Examples 1-5: 1. Mechanical property testing: The test methods specified in JTGE51-2009 "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering" were adopted to test the 3-day unconfined compressive strength, 7-day unconfined compressive strength and 28-day unconfined compressive strength of cement-stabilized crushed stone. 2. Durability test: The test method specified in JTGE51-2009 "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" was adopted. The monitoring period was set from 1 day to 28 days. The data was read once a day for the first 7 days and once every 2 days from 7 days to 28 days. The average drying shrinkage coefficient of cement stabilized crushed stone and the water loss rate on the 7th day were calculated.

[0054] The test results are shown in the table below: Table 1 Performance test results of cement-stabilized crushed stone in Examples 1-18 and Comparative Examples 1-5

[0055] Compared with Comparative Examples 1-5, the 3-day compressive strength, 7-day compressive strength, and 28-day compressive strength of cement-stabilized crushed stone in Examples 1-18 were all improved, while the water loss rate and average drying shrinkage coefficient were all reduced. This indicates that in the present invention, the addition of first sodium polyacrylate and second sodium polyacrylate can improve the compressive strength of cement-stabilized crushed stone while improving the cement's stability, shrinkage reduction, and crack resistance.

[0056] Compared with Comparative Example 5, Comparative Examples 1-4 added only one type of sodium polyacrylate or added two types of sodium polyacrylate, but the mass of the first sodium polyacrylate was greater than or equal to that of the second sodium polyacrylate. As a result, the water loss rate and average drying shrinkage coefficient of the cement-stabilized crushed stone were reduced, but the 3-day compressive strength was also reduced. However, Examples 1-5 improved the shrinkage and crack resistance of cement-stabilized crushed stone by adjusting the mass ratio of the two types of sodium polyacrylate. In addition, they also improved the 3-day compressive strength, 7-day compressive strength and 28-day compressive strength of cement-stabilized crushed stone. Thus, they not only improved the shrinkage and crack resistance of the cement-stabilized crushed stone base layer, but also improved the mechanical properties of the cement-stabilized crushed stone base layer.

[0057] Compared with Examples 1 and 3, the cement-stabilized crushed stone in Examples 4 and 5 had lower water loss rate and average drying shrinkage coefficient, indicating that when the mass ratio of the first sodium polyacrylate to the second sodium polyacrylate was 1:4~9, the water loss rate and drying shrinkage strain of the cement-stabilized crushed stone were further reduced.

[0058] Compared with Example 1, the cement-stabilized crushed stone of Examples 6-8 has a higher 3d compressive strength, indicating that when the particle size of the first sodium polyacrylate is 50-80 mesh and the particle size of the second sodium polyacrylate is 100-120 mesh, the 3d compressive strength of the cement-stabilized crushed stone is further improved.

[0059] Compared with Example 1, the cement-stabilized crushed stone in Examples 9-14 has higher 3d compressive strength and 7d compressive strength, and lower average drying shrinkage coefficient, indicating that the addition of toughening agent to cement-stabilized crushed stone further reduces the drying shrinkage strain of cement-stabilized crushed stone and improves its mechanical properties.

[0060] Compared with Examples 1 and 16-18, the cement-stabilized crushed stone of Example 15 had the highest 3-day compressive strength and 7-day compressive strength, and the lowest water loss rate and average drying shrinkage coefficient. This indicates that the specific mixing sequence further reduced the drying shrinkage strain of the cement-stabilized crushed stone and improved its mechanical properties.

[0061] This is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shrinkage-reducing and crack-resistant cement-stabilized crushed stone with added SAP, characterized in that, Includes the following components in parts by weight: 100 parts crushed stone, 5 parts cement, 5-6 parts water, 0.01-0.03 parts sodium polyacrylate; The sodium polyacrylate includes a first sodium polyacrylate and a second sodium polyacrylate. The first sodium polyacrylate has a particle size of 30-80 mesh. The particle size of the second sodium polyacrylate is 90-150 mesh. The mass ratio of the first sodium polyacrylate to the second sodium polyacrylate is 1:4~9.

2. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 1, characterized in that, The first sodium polyacrylate has a particle size of 50-80 mesh.

3. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 2, characterized in that, The particle size of the second sodium polyacrylate is 100-120 mesh.

4. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 1, characterized in that, The crushed stone, by weight percentage, consists of crushed stone of the following particle sizes: Crushed stone with a particle size ≤ 5mm: 25%~30%; crushed stone with a particle size of 5mm < ≤ 10mm: 20%~35%; crushed stone with a particle size of 10mm < ≤ 20mm: 25%~35%; crushed stone with a particle size of 20mm < ≤ 30mm: 10%~20%.

5. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 1, characterized in that, It also includes the following components in parts by weight: toughening agent 0.002~0.02 parts, wherein the toughening agent comprises the following components in parts by weight: 5-15 parts polyacrylamide, 1-5 parts tartaric acid, 1-3 parts titanate coupling agent, and 30-50 parts sericite.

6. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 5, characterized in that, The toughening agent contains polyacrylamide, tartaric acid, titanate coupling agent, and sericite in a mass ratio of 10:2:1:

40.

7. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 6, characterized in that, The mass ratio of the toughening agent to the sodium polyacrylate is 1:2~3.

8. The SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to claim 6, characterized in that, The toughening agent is prepared by mixing polyacrylamide, tartaric acid, titanate coupling agent and sericite to obtain the toughening agent.

9. The method for preparing SAP-admixed, shrinkage-reducing, crack-resistant cement-stabilized crushed stone according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Mix cement with sodium polyacrylate to obtain premix one; S2. Mix the crushed stone with the second sodium polyacrylate to obtain premix two; S3. Mix premix one and premix two with water to obtain SAP-admixed shrinkage-reducing and crack-resistant cement-stabilized crushed stone.

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