Skeleton dense type cement stable regenerated gravel structural layer

Abstract

The invention relates to the technical field of cement stabilized regenerated macadam, and relates to a skeleton compact type cement stabilized regenerated macadam structure layer, which comprises the following components by weight: 5-10 parts of modified cement, 100-150 parts of regenerated macadam, and 10-15 parts of limestone, the modified cement is prepared from Portland cement, sodium alginate and calcium chloride according to a molar ratio of 1: 5: 2-4, and the regenerated macadam is prepared from sodium alginate and calcium chloride according to a molar ratio of 1: 5: 2-4. Sodium alginate serves as a carrier, Portland cement is loaded, calcium chloride is added, a network structure is formed, under the interaction of sodium alginate and cement, cement and calcium chloride and calcium chloride and sodium alginate, the mechanical strength, durability and water resistance of cement are remarkably improved, and the service life of a road is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of cement-stabilized regenerated crushed stone, in particular to a dense-skeleton type cement-stabilized regenerated crushed stone structure layer. Background Art

[0002] Roads are infrastructure for various trackless vehicles and pedestrians to pass through. With the development of society, higher requirements are placed on roads. In my country's early days, roads were of low grade and had small traffic vehicle loads. The road surface was easily damaged, and a large amount of money was required for road maintenance. With the improvement of people's living standards and the increasing popularity of cars, the service life and strength of roads have become particularly important.

[0003] For traditional cement-stabilized recycled gravel, cement and recycled gravel (materials after crushing, screening, etc. of construction waste) are usually mixed in a certain proportion, and then water is added for mixing and compacting. The characteristics are simple construction method and low cost. However, its strength and durability are poor, and it cannot effectively withstand traffic loads and external stresses. It can only be used in places with low requirements for road surfaces. In view of this, a skeleton-dense cement-stabilized recycled gravel structure layer is provided. Summary of the invention

[0004] The purpose of the present invention is to provide a dense skeleton type cement stabilized regenerated crushed stone structure layer to solve the problem of poor strength and durability of the conventional cement stabilized regenerated crushed stone mentioned in the above background technology.

[0005] To achieve the above object, the present invention aims to provide a skeleton-dense cement-stabilized recycled gravel structure layer, comprising the following components in parts by weight: 5-10 parts by weight of modified cement, 100-150 parts by weight of recycled gravel, and 10-15 parts by weight of limestone, wherein the modified cement is prepared from silicate cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2-4.

[0006] As a further improvement of the technical solution, the preparation method of the modified cement is as follows:

[0007] S1.1. Prepare components: prepare sodium alginate solution and calcium chloride solution of a certain concentration;

[0008] S1.2. Preparation of modified cement: Add water to silicate cement and stir evenly, wherein the mass ratio of silicate cement to water is 1:1-1.5, then add sodium alginate solution to cement, set the stirrer speed to 600-800r / min and stir for 20 minutes, then add calcium chloride solution while stirring, and continue stirring for 10 minutes to obtain modified cement.

[0009] Portland cement is a common hydraulic cementitious material, mainly composed of calcium silicate minerals. These minerals are made by calcining a mixture of limestone and clay. When mixed with water, they can form a slurry, which can gradually harden in the air or harden underwater to form a hard solid. The hardened cement has high mechanical strength and can firmly bond sand, stone or other filling materials together to form mortar or concrete. Therefore, Portland cement has excellent mechanical properties, good compressive strength, appropriate setting time and good durability. Therefore, it is widely used in construction and civil engineering, such as concrete preparation, mortar mixing, prefabricated component manufacturing, structure casting, road paving, etc.

[0010] The main component of limestone is calcium carbonate, which will generate calcium oxide after calcination. Calcium oxide generates calcium hydroxide in water, which is a white solid that is slightly soluble in water. However, when the number of protons in the solution increases, calcium carbonate will react with protons to generate calcium chloride and water, which promotes the dissociation of calcium ions. Since sodium alginate can react with calcium ions, calcium ions are enriched on the surface of the porous structure layer. When the calcium ions saturate the surface of the structure layer, the hardness of the structure layer is greatly enhanced. At the same time, the free calcium ions in the solution will also react with the silicate ions in the porous structure layer, becoming an important role in providing mechanical strength to the cement structure, thereby significantly improving the compressive strength of the road.

[0011] As a further improvement of the technical solution, the molar concentration of the sodium alginate solution is 2.5-3.2 mol / L.

[0012] Sodium alginate is a natural linear anionic polysaccharide extracted from brown algae by the action of two bacteria, nitrogen-fixing bacteria and pseudomonas. It is composed of 1,4-linked β-d-mannuronic acid (M) and α-l-guluronic acid (G) residues. Sodium alginate is a viscous polymer compound. Unlike starch and cellulose, it has a carboxyl group and is a high-polysaccharide uronic acid formed by the aldehyde group of β-d-mannuronic acid with a glycosidic bond. Sodium alginate has a strong hydrophilicity and can be dissolved in both cold and warm water to form a very viscous solution. It is also because of its It has a certain viscosity, so it can enhance the interface bonding force between cement and the surface layer, base layer and cushion layer, ensure the close connection between the structural layers, prevent interlayer sliding and separation, effectively improve the mutual bonding between the road structural layers, and improve the durability of the road. At the same time, when the road surface is subjected to load, it can disperse the stress transmitted between layers, reduce stress concentration, and improve the integrity of the road. In addition, it can also prevent moisture from penetrating into the structural layer, avoid frost heave, erosion or chemical reactions caused by moisture, thereby protecting the road structure from damage and extending the service life of the road.

[0013] As a further improvement of the technical solution, the molar concentration of the calcium chloride solution is 1.8-2.0 mol / L.

[0014] When cement is introduced into sodium alginate, the sodium alginate will dissociate into alginate anions after dissolving in water, and the Ca2+ anions will react with the calcium oxide solution. 2+ Electrostatic interaction occurs and attracts each other, thus agglomerating and precipitating to form a porous structure layer, and calcium chloride reacts with cement in the porous structure layer to form calcium silicate hydrate (CSH), which is an amorphous, highly cross-linked structure. It is precisely because of its complex three-dimensional network structure and high-density hydrogen bonds and ionic bonds that the strength of the cement after curing is greatly improved. From a microscopic scale, small calcium silicate particles can form a dense structure and become a part of the cured cement, acting as a filler and reinforcing agent, limiting the expansion of cracks and increasing the density of the material, thereby increasing the compressive strength and flexural strength of the concrete, and significantly improving the mechanical strength of the road.

[0015] As a further improvement of the technical solution, the mass ratio of the silicate cement to the added water is 1:1 to 1.5.

[0016] As a further improvement of the technical solution, the agitator speed is 600-800 r / min, and the stirring time is 20 min.

[0017] As a further improvement of the technical solution, the stirring time after the calcium chloride solution is added is 10 minutes.

[0018] As a further improvement of the technical solution, the specific preparation method of the skeleton dense cement stabilized regenerated crushed stone structure layer is as follows:

[0019] The modified cement and recycled crushed stone are mixed with water, stirred evenly, and the pH value is adjusted to obtain a dense skeleton cement-stabilized recycled crushed stone structure layer.

[0020] As a further improvement of the technical solution, the ratio of the regenerated gravel to water is 100:3-5.

[0021] As a further improvement of the technical solution, the pH value is adjusted to 6-7 by a hydrochloric acid solution with a molar concentration of 10 mol / L.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the skeleton-dense cement-stabilized recycled gravel structure layer, sodium alginate is used as a carrier to load silicate cement to form a network structure. Sodium alginate is polymerized with calcium ions and enriched on the surface of sodium alginate to enhance the hardness of the cement. At the same time, calcium chloride is used to react with cement in the porous structure layer to generate hydrated calcium silicate. Through the three-dimensional network structure of hydrated calcium silicate, high-density hydrogen bonds and ionic bonds, the cross-linked network structure of sodium alginate, small calcium silicate particles acting as fillers and reinforcing agents, and sodium alginate acting as a binder, the mechanical strength, durability and water resistance are significantly improved, thereby extending the service life of the road. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The skeleton-dense cement-stabilized recycled crushed stone structure layer comprises the following components in parts by weight: 5-10 parts by weight of modified cement, 100-150 parts by weight of recycled crushed stone, and 10-15 parts by weight of limestone, wherein the modified cement is prepared from silicate cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2-4.

[0026] Example 1

[0027] In this embodiment, the specific preparation method of the dense skeleton cement-stabilized regenerated gravel structure layer is as follows:

[0028] S3.1. Configure and prepare components: configure a sodium alginate solution with a molar concentration of 3 mol / L and a calcium chloride solution with a molar concentration of 2.0 mol / L, prepare 5 parts by weight of modified cement, 100 parts by weight of recycled crushed stone, and 10 parts by weight of limestone. The modified cement is prepared from cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2.

[0029] S3.2. Preparation of modified cement: Add water to silicate cement and stir evenly, wherein the mass ratio of silicate cement to water is 1:1, then add sodium alginate solution to the silicate cement, set the stirrer speed to 800r / min and stir for 20 minutes, then add calcium chloride solution while stirring, and continue stirring for 10 minutes to obtain modified cement.

[0030] S3.3. Preparation of a dense skeleton type cement stabilized recycled gravel structure layer: Add water to the modified cement and recycled gravel and stir evenly, wherein the ratio of recycled gravel to water is 100:5, and adjust the pH value to 6, to obtain a dense skeleton type cement stabilized recycled gravel structure layer.

[0031] Example 2

[0032] In this embodiment, the specific preparation method of the dense skeleton cement-stabilized regenerated gravel structure layer is as follows:

[0033] S3.1. Configure and prepare components: configure a sodium alginate solution with a molar concentration of 3 mol / L and a calcium chloride solution with a molar concentration of 2.0 mol / L, prepare 7 parts by weight of modified cement, 100 parts by weight of recycled crushed stone, and 10 parts by weight of limestone. The modified cement is prepared from cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2.

[0034] S3.2. Preparation of modified cement: Add water to silicate cement and stir evenly, wherein the mass ratio of silicate cement to water is 1:1, then add sodium alginate solution to the silicate cement, set the stirrer speed to 800r / min and stir for 20 minutes, then add calcium chloride solution while stirring, and continue stirring for 10 minutes to obtain modified cement.

[0035] S3.3. Preparation of a dense skeleton type cement stabilized recycled gravel structure layer: Add water to the modified cement and recycled gravel and stir evenly, wherein the ratio of recycled gravel to water is 100:5, and adjust the pH value to 6, to obtain a dense skeleton type cement stabilized recycled gravel structure layer.

[0036] Example 3

[0037] In this embodiment, the specific preparation method of the dense skeleton cement-stabilized regenerated gravel structure layer is as follows:

[0038] S3.1. Configure and prepare components: prepare a sodium alginate solution with a molar concentration of 3 mol / L and a calcium chloride solution with a molar concentration of 2.0 mol / L, prepare 10 parts by weight of modified cement, 100 parts by weight of recycled crushed stone, and 10 parts by weight of limestone. The modified cement is prepared from cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2.

[0039] S3.2. Preparation of modified cement: Add water to silicate cement and stir evenly, wherein the mass ratio of silicate cement to water is 1:1, then add sodium alginate solution to the silicate cement, set the stirrer speed to 800r / min and stir for 20 minutes, then add calcium chloride solution while stirring, and continue stirring for 10 minutes to obtain modified cement.

[0040] S3.3. Preparation of a dense skeleton type cement stabilized recycled gravel structure layer: Add water to the modified cement and recycled gravel and stir evenly, wherein the ratio of recycled gravel to water is 100:5, and adjust the pH value to 6, to obtain a dense skeleton type cement stabilized recycled gravel structure layer.

[0041] Comparative Example 1

[0042] The method of Example 2 was adopted without adding modified cement.

[0043] Comparative Example 2

[0044] The method of Example 2 was adopted to reduce the concentration of calcium chloride to 1.8 mol / L.

[0045] The present invention prepares a skeleton-dense cement-stabilized regenerated gravel structure layer, which has good mechanical strength, durability and water resistance in the application field of cement-stabilized regenerated gravel, and prolongs the service life of the road. Specific tests are shown in the following table;

[0046] Refer to GB / T 18297-2008 "Technical Conditions for Use of Recycled Materials in Road Engineering", which stipulates the quality requirements, test methods and inspection rules for recycled materials. Since recycled gravel is used, the recycled gravel needs to be inspected according to this standard before being put into use.

[0047] Referring to GB / T 50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", although this standard is mainly for ordinary concrete, the unconfined compressive strength test method therein is also applicable to other types of compacted materials, including dense skeleton cement-stabilized crushed stone.

[0048] The unconfined compressive strength test is a test method used to determine the ultimate strength of a material against axial pressure without lateral pressure. First, a standard-sized specimen is prepared according to the test requirements. Then the specimen is placed on the specimen seat of the unconfined compression instrument to ensure that there is no restriction on both sides of the specimen. The axial pressure is slowly and evenly increased until the specimen is destroyed. The maximum axial pressure when the specimen is destroyed is the unconfined compressive strength. Finally, the average cross-sectional area of ​​the specimen is calculated based on the test data to calculate the unconfined compressive strength value.

[0049] The obtained data are shown in Table 1

[0050] Table 1 Performance data of the skeleton dense cement stabilized regenerated crushed stone structure layer of Examples 1-3 and Comparative Examples 1-2

[0051]

[0052] By comparing Example 1-3 with Comparative Example 1-2, it can be seen that adding modified cement to the dense skeleton cement-stabilized recycled crushed stone structure layer will have a significant impact on the mechanical properties of the pavement structure layer.

[0053] With the increase of modified cement content, the compressive strength of the skeleton dense cement stabilized recycled gravel structure layer is significantly improved. From the perspective of sodium alginate itself, sodium alginate is a viscous solution with a certain viscosity and can act as a binder. On the one hand, it can enhance the interface bonding force between cement and each structural layer to prevent interlayer sliding and separation. On the other hand, it can prevent moisture from penetrating into the underlying structure, avoiding frost heave, erosion or chemical reactions caused by moisture, thereby protecting the road structure from damage. It also helps to transfer the stress generated by vehicle loads between layers, evenly distribute pressure, reduce local stress concentration, and extend the service life of the road. From the perspective of sodium alginate, silicate cement and calcium chloride, sodium alginate can load silicate cement. The anions and cations ionized by calcium chloride and sodium alginate in aqueous solution combine with each other through the electrostatic effect of anions and cations to form a network structure. The internal void structure is filled with silicate cement. Because silicate cement contains silicate ions and calcium ions, it combines to form hydrated calcium silicate. Since hydrated calcium silicate is an amorphous, highly cross-linked structure, its complex three-dimensional network structure and high-density hydrogen bonds and ionic bonds greatly improve the strength of the cement after curing. From a microscopic scale, small calcium silicate particles can form a dense structure and become a part of the cement after curing, acting as a filler and reinforcing agent, limiting the expansion of cracks, and increasing the density of the material, thereby increasing the compressive strength and flexural strength of the concrete, and significantly improving the mechanical strength of the road.

[0054] According to the above test experiments, Example 3 is used as the optimal example and compared with Comparative Examples 1-2 respectively.

[0055] By comparing Example 3 with Comparative Example 1, it can be seen that when modified cement is not used, the compressive strength of the skeleton dense cement stabilized recycled crushed stone structure layer is significantly reduced. Due to the lack of sodium alginate acting as a binder, the various structural layers of the road cannot be bonded. When the road surface is subjected to load, the stress is concentrated at a certain point on the road surface, causing the road surface to be damaged, increasing the maintenance cost. At the same time, the various structural layers are easy to separate, which is not conducive to the integrity of the road and greatly reduces the durability and mechanical strength of the road. In addition, there is no sodium alginate-loaded silicate cement to interact with calcium chloride, which loses the binding force between sodium alginate and silicate, the binding force between silicate and calcium chloride, and the binding force between sodium alginate and calcium chloride, thereby greatly reducing the compressive strength of cement.

[0056] By comparing Example 3 with Comparative Example 2, it can be seen that as the concentration of calcium chloride decreases, the compressive strength of the dense skeleton type cement stabilized regenerated gravel structure layer decreases. This is because sodium alginate can react with calcium ions, so that calcium ions are enriched on the surface of the porous structure layer. When the calcium ion concentration does not reach the saturation of the structure layer surface, the hardness of the structure layer at this time will decrease. Therefore, choosing an appropriate calcium chloride concentration is also a key factor in enhancing the compressive strength of the dense skeleton type cement stabilized regenerated gravel structure layer.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. The skeleton-dense cement-stabilized recycled gravel structure layer is characterized by: The invention comprises the following components in parts by weight: 5-10 parts by weight of modified cement, 100-150 parts by weight of recycled crushed stone, and 10-15 parts by weight of limestone; The modified cement is prepared from silicate cement, sodium alginate and calcium chloride in a molar ratio of 1:5:2-4.

2. The dense skeleton cement-stabilized regenerated crushed stone structure layer according to claim 1 is characterized by: The preparation method of the modified cement is as follows: S1.

1. Prepare components: prepare sodium alginate solution and calcium chloride solution of a certain concentration; S1.

2. Preparation of modified cement: Add water to silicate cement and stir evenly, wherein the mass ratio of silicate cement to water is 1:1-1.5, then add sodium alginate solution to silicate cement, set the stirrer speed to 600-800r / min and stir for 20 minutes, then add calcium chloride solution while stirring, and continue stirring for 10 minutes to obtain modified cement.

3. The dense skeleton cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized in that: The molar concentration of the sodium alginate solution is 2.5-3.2 mol / L.

4. The skeleton-dense cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized in that: The molar concentration of the calcium chloride solution is 1.8-2.0 mol / L.

5. The dense skeleton cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized in that: The mass ratio of the silicate cement to the added water is 1:1 to 1.

5.

6. The dense skeleton cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized by: The stirring speed is 600-800 r / min, and the stirring time is 20 min.

7. The dense skeleton cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized by: The stirring time after the calcium chloride solution is added is 10 minutes.

8. The skeleton-dense cement-stabilized regenerated crushed stone structure layer according to claim 2 is characterized by: The specific preparation method of the skeleton dense cement stabilized regenerated crushed stone structure layer is as follows: The modified cement and recycled crushed stone are mixed with water, stirred evenly, and the pH value is adjusted to obtain a dense skeleton cement-stabilized recycled crushed stone structure layer.

9. The skeleton-dense cement-stabilized regenerated crushed stone structure layer according to claim 7 is characterized in that: The ratio of the regenerated crushed stone to water is 100:3-5.

10. The dense-frame cement-stabilized regenerated crushed stone structure layer according to claim 7, characterized in that: The pH value is adjusted to 6-7 by a hydrochloric acid solution with a molar concentration of 10 mol / L.

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