Low water cement ratio kerb precast block and method of production thereof

Abstract

This invention discloses a precast curbstone block and its production method, belonging to the field of road construction technology. The precast curbstone block consists of a bottom layer and a top layer; the bottom layer is composed of the following raw materials in parts by weight: 250-300 parts cement, 50-80 parts fly ash, 850-920 parts machine-made medium sand, 600-650 parts 3-5mm gravel, 300-320 parts 5-10mm gravel, and 60-80 parts water; the top layer is composed of the following raw materials in parts by weight: 1500-1700 parts river sand, 550-650 parts cement, and 140-160 parts water. This invention abandons the conventional model casting and one-piece molding process, and adopts dry hard concrete with low water-cement ratio. It uses a layered mixing and multi-layer integrated extrusion molding construction process, which makes the precast curb blocks more economical in terms of material usage and significantly increases their strength. It only needs to go through the production steps of mixing, pressing and curing, and the curing can be carried out at 50℃ for 8 hours, which improves the production efficiency. The precast curb blocks produced are of stable quality, high efficiency and low failure rate.

Description

Technical Field

[0001] This invention belongs to the field of road construction technology, specifically relating to a low water-cement ratio precast curb block and its production method. Background Technology

[0002] As a fundamental building material in road engineering, curbstones are mainly used to separate functional areas such as carriageways, sidewalks, and green belts, while also playing core roles in drainage, roadbed protection, and traffic flow guidance. Traditional curbstone construction often employs on-site casting, which suffers from drawbacks such as long construction cycles, susceptibility to weather conditions, and dependence on manual labor for quality. With the promotion of prefabricated building concepts in municipal engineering, precast curbstones, with their advantages of standardized production, high construction efficiency, and stable quality, are gradually becoming the mainstream solution in the industry.

[0003] Conventional precast block production uses a mold-casting process, also known as the casting method. The material used is uniformly produced and mixed concrete, typically with a water-cement ratio of 0.4 or higher. The construction process includes mixing, mold cleaning, applying release agent, pouring, vibration, demolding, and curing. It takes approximately 14 days from production to curing of one precast block. Problems during production, such as excessively dry materials or concrete segregation, can lead to issues in the finished precast blocks, affecting both cost and quality. Most construction processes are performed by a combination of machinery and manual labor, requiring a significant workforce; the experience of the workers directly impacts the quality of the finished product. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a precast curb block and its production method. It abandons the conventional model casting and one-piece molding process, and adopts dry hard concrete with low water-cement ratio. The process involves layered mixing and production, and multi-layer one-piece extrusion molding, which makes the precast slabs more economical in terms of material usage, significantly increases strength, reduces curing time, and improves production efficiency.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a precast curbstone block, comprising a bottom layer and a top layer; The bottom layer is composed of the following raw materials in parts by weight: 250-300 parts cement, 50-80 parts fly ash, 850-920 parts machine-made medium sand, 600-650 parts 3-5mm gravel, 300-320 parts 5-10mm gravel, and 60-80 parts water; The surface layer is composed of the following parts by weight of raw materials: 1500-1700 parts river sand, 550-650 parts cement, 10-15 parts water-reducing agent, and 140-160 parts water.

[0006] Furthermore, the bottom layer is composed of the following raw materials in parts by weight: 280 parts cement, 70 parts fly ash, 900 parts machine-made medium sand, 630 parts 3-5mm gravel, 315 parts 5-10mm gravel, and 70 parts water; The surface layer is composed of the following parts by weight of raw materials: 1631 parts river sand, 619 parts cement, 13.5 parts water-reducing agent, and 155 parts water.

[0007] Furthermore, the cement is PP. O 42.5 cement.

[0008] Furthermore, the bottom and top layer materials also include a water-reducing agent, wherein the amount of water-reducing agent added to the bottom layer is 0.4~0.5% of the bottom layer solid mass, and the amount of water-reducing agent added to the top layer is 0.5~0.6% of the top layer solid mass.

[0009] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent.

[0010] In a second aspect, the present invention provides a method for producing the aforementioned precast curbstone blocks, comprising the following steps: (1) Mix the bottom layer material and the top layer material evenly; (2) Spread the mixed bottom material on the bottom of the mold, flatten it and then pre-press it; (3) Lay the mixed surface material on the pre-compressed bottom layer, flatten it and then press it down heavily; (4) After step (3) pressing, squeeze, vibrate and demold, and then cure after demolding.

[0011] Furthermore, the pre-compression pressure in step (2) is 10 MPa; the re-compression pressure in step (3) is 20 MPa.

[0012] Furthermore, the extrusion conditions in step (4) are as follows: extrusion is performed using an extrusion plate at a pressure of 20 MPa.

[0013] Furthermore, the curing conditions in step (4) are 40~60℃ in a steam curing room for 4~10 hours.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention abandons the conventional model casting and one-piece molding process, and adopts dry hard concrete with low water-cement ratio. It uses a layered mixing and multi-layer integrated extrusion molding construction process, which makes the precast curb blocks more economical in terms of material usage and significantly increases their strength. It only needs to go through the production steps of mixing, pressing and curing, and the curing can be carried out at 50℃ for 8 hours, which improves the production efficiency. The precast curb blocks produced are of stable quality, high efficiency and low failure rate. Detailed Implementation

[0015] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0017] In the following examples and comparative examples, the parts mentioned are by weight; the water-reducing agent is a polycarboxylate superplasticizer; the river sand is MX2.1; and the cement is P. O 42.5; The manufactured sand is medium sand with a bulk density of 1514 kg / m³. 3 The crushed stone comes in two sizes: 5-10mm and 3-5mm. The apparent density of the 5-10mm stones is 2736 kg / m³. 3 The bulk density is 1484 kg / m³. 3 The bulk density of 3-5mm particles is 1486kg / m³. 3 .

[0018] Example 1 The precast curbstone blocks consist of a bottom layer and a top layer. The bottom layer in Example 1 consists of the following raw materials in parts by weight: 280 parts cement, 70 parts fly ash, 900 parts machine-made medium sand, 630 parts 3-5mm gravel, 315 parts 5-10mm gravel, 70 parts water, and polycarboxylate superplasticizer (0.5% of the solid mass of the bottom layer). The surface layer is composed of the following raw materials in parts by weight: 1631 parts river sand, 619 parts cement, 155 parts water, and polycarboxylate superplasticizer (0.6% of the surface layer solid mass). The production method of precast curbstone blocks is as follows: (1) Mix the bottom layer material and the top layer material evenly; (2) Lay the mixed bottom material on the bottom of the mold, flatten it and then pre-press it with a pre-pressing pressure of 10 MPa; (3) Lay the mixed surface material on the pre-compressed bottom layer, flatten it and then press it down with a pressure of 20 MPa. (4) After step (3) pressing, extrusion (extrusion pressure is 20mPa), vibration and demolding are performed. After demolding, curing is carried out (steam curing at 50℃ for 8h). The surface layer thickness is 1cm and the bottom layer thickness is 1cm.

[0019] Example 2 The raw material composition of the bottom layer of the curbstone precast block in Example 1 was changed as shown in Table 1. The slump, apparent density, 28-day compressive strength, porosity, and interlayer bonding strength of the bottom layer were tested, and the results are shown in Table 2. Table 1. Raw material ratio for precast curbstone blocks produced from different base materials. Table 2 Performance Test Table of Curbstone Precast Blocks Produced from Different Base Materials As shown in Tables 1 and 2, the workability, density, compressive strength, and interlayer bonding of precast curbstone blocks are highly dependent on the total amount of cementitious material (cement + fly ash), water-cement ratio, and porosity. More cementitious material results in greater slump (better workability), higher apparent density, lower porosity, higher compressive strength, and better interlayer bonding. Lower porosity leads to higher 28-day compressive strength and higher interlayer bonding strength. Excessive water content can cause slight interlayer adhesion, reducing bonding reliability. Therefore, group D-01 represents the optimal bottom layer material mix.

[0020] Example 3 The raw material composition of the curbstone precast block surface layer in Example 1 was changed as shown in Table 3. The slump, apparent density, initial setting time, 28-day compressive strength, molding density, and surface layer thickness adaptability of the surface layer were tested, and the results are shown in Table 4 below. Table 3. Raw material ratio for precast curbstone blocks produced from different surface layer materials. Table 4 Performance Test Table of Curbstone Precast Blocks Produced from Different Surface Layer Raw Materials As shown in Tables 3 and 4, the raw material ratio determines the forming state of the surface layer. The curbstone precast block surface layer prepared by the raw material ratio shown in M-01 has a uniform thickness, is dense and smooth, and its strength meets the standard.

[0021] Comparative Example 1 The bottom and top layer materials from Example 1 were mixed, evenly spread in a mold, and pressed, but it was found that they could not be formed.

[0022] Performance testing of precast curb blocks The overall 28-day compressive strength, surface layer local strength, bottom layer local strength, surface layer thickness, dimensional deviation, surface smoothness, interlayer bond strength, flexural strength, water absorption, and the percentage of precast curbstone blocks produced in Example 1 that meet the design values ​​were tested. The results are shown in Table 5 below. Table 5 Performance Test Table of Curbstone Precast Blocks Produced in Example 1 As shown in Table 5, the precast curb blocks composed of the surface layer and the bottom layer of this application can meet the standard requirements in all aspects. This invention uses dry hard concrete with a low water-cement ratio, and adopts a multi-layer integrated extrusion molding construction process, which saves more materials, significantly increases strength, and has outstanding technical effects.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A precast curbstone block, characterized in that, It consists of a bottom layer and a top layer; The bottom layer is composed of the following raw materials in parts by weight: 250-300 parts cement, 50-80 parts fly ash, 850-920 parts machine-made medium sand, 600-650 parts 3-5mm gravel, 300-320 parts 5-10mm gravel, and 60-80 parts water; The surface layer is composed of the following parts by weight of raw materials: 1500-1700 parts river sand, 550-650 parts cement, 10-15 parts water-reducing agent, and 140-160 parts water.

2. The precast curb block according to claim 1, characterized in that, The bottom layer is composed of the following raw materials in parts by weight: 280 parts cement, 70 parts fly ash, 900 parts machine-made medium sand, 630 parts 3-5mm gravel, 315 parts 5-10mm gravel, and 70 parts water; The surface layer is composed of the following parts by weight of raw materials: 1631 parts river sand, 619 parts cement, 13.5 parts water-reducing agent, and 155 parts water.

3. The precast curb block according to claim 1 or 2, characterized in that, The cement mentioned is PP O 42.5 cement.

4. The precast curb block according to claim 1 or 2, characterized in that, The bottom and top layer materials also include a water-reducing agent. The amount of water-reducing agent added to the bottom layer is 0.4-0.5% of the bottom layer solid mass, and the amount of water-reducing agent added to the top layer is 0.5-0.6% of the top layer solid mass.

5. The precast curb block according to claim 4, characterized in that, The water-reducing agent mentioned above is a polycarboxylate water-reducing agent.

6. A method for producing precast curbstone blocks according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Mix the bottom layer ingredients and the top layer ingredients evenly; (2) Spread the mixed bottom material on the bottom of the mold, flatten it and then pre-press it; (3) Lay the mixed surface material on the pre-compressed bottom layer, flatten it and then press it down heavily; (4) After step (3) pressing, squeeze, vibrate and demold, and then cure after demolding.

7. The method for producing precast curbstone blocks according to claim 6, characterized in that, The pre-compression pressure in step (2) is 10 MPa; the pressure of the heavy compression in step (3) is 20 MPa.

8. The method for producing precast curbstone blocks according to claim 6, characterized in that, The extrusion conditions described in step (4) are to use an extrusion plate for extrusion and a pressure of 20 MPa.

9. The method for producing precast curbstone blocks according to claim 5, characterized in that, The curing conditions in step (4) are 40~60℃ in a steam curing room for 4~10 hours.

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