Wide source binder mixing process based on large aggregate

Abstract

The application provides a wide-source binder mixing process based on large-diameter aggregate, and the main steps are as follows: S1, screening sand and gravel raw materials containing large-diameter aggregate into coarse materials and fine materials, wherein the mesh size of the screen is 80-150 mm; S2, uniformly mixing cement, admixture, water, additive and the fine materials in S1; S3, adding the coarse materials in S1 into the mixture obtained in S2 and then loading the mixture into a vehicle, or adding the coarse materials in S1 into the mixture obtained in S2 during loading the mixture into the vehicle, transporting the mixture to a construction site for paving, rolling and curing, and completing the construction of the cemented sand and gravel. The application provides a cemented sand and gravel construction process based on large-diameter aggregate, which can break through the maximum particle size limit of sand and gravel, and the prepared cemented sand and gravel has higher strength, so that the generation of waste materials can be greatly reduced, and the process and cost can be saved.

Description

Technical Field

[0001] This invention belongs to the field of green building materials technology, specifically relating to a mixing process for Guangyuan cementitious materials based on large-particle-size aggregates. Background Technology

[0002] The "Technical Guidelines for Dam Construction with Cemented Granular Materials" (SL 678-2014) stipulates that the maximum particle size of cemented gravel should not exceed 150mm. This results in a large amount of waste material during construction, which is not conducive to reducing costs and making full use of raw materials.

[0003] Furthermore, SL 678-2014 only mentions natural sand and gravel, artificial sand and gravel, and excavated stone chips as raw materials for sand and gravel, without mentioning crushed stone and soil. Guangyuan cementitious building materials, however, are guided by green building principles, utilizing natural materials as much as possible to achieve minimal or zero waste. This inevitably leads to problems such as large variations in gradation and difficulties in mixing large particle sizes. Because the maximum particle size of domestically developed cementitious on-site mixing equipment systems and cemented sand and gravel mixing systems is 150mm, Guangyuan's efforts to minimize waste and achieve applications exceeding the maximum particle size of 150mm cannot be realized. This is the main reason why the production efficiency and practical application range of Guangyuan cementitious materials are limited.

[0004] To overcome this bottleneck, this invention studies the strength production mechanism of binders, identifies key factors affecting strength, and considers the skeletal role of coarse aggregates without their participation in the binder system. This allows for the pre-removal of coarse aggregates before mixing with fine aggregates, thus exceeding the maximum aggregate particle size required by specifications. Summary of the Invention

[0005] This invention provides a wide-source cementitious aggregate mixing process based on large-diameter aggregates, which can break through the maximum particle size limitation of sand and gravel, and the prepared cemented sand and gravel has higher strength, which can significantly reduce the generation of waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a cemented gravel construction process based on large-diameter aggregates, comprising the following steps:

[0007] S1. Screen the sand and gravel aggregate containing large particles to separate it into coarse and fine materials, with the screen mesh size being 80-150mm.

[0008] S2. Mix the cement, admixtures, water, additives and fine materials from S1 evenly;

[0009] S3. Add the coarse material from S1 to the mixture obtained in S2 and then load it onto the truck, or add the coarse material from S1 to the mixture obtained in S2 during the loading process. Transport it to the construction site for paving, compaction and curing to complete the construction of cemented gravel.

[0010] Furthermore, the large-diameter gravel has a particle size of less than 400 mm, and the maximum particle size is ≤ 2 / 3 of the cemented gravel paving thickness.

[0011] Furthermore, the large-diameter gravel includes natural gravel, artificial gravel, excavated stone chips, or crushed stone and soil.

[0012] Furthermore, during the screening process in S1, particles smaller than 80mm are classified as fine materials, while the rest are classified as coarse materials.

[0013] Furthermore, the mixing time in S2 is 2 to 3 minutes.

[0014] The present invention also relates to cemented gravel obtained by the aforementioned mixing process.

[0015] The present invention also relates to the application of the cemented gravel in cemented dams, cemented gravel enhancement zones, or roadbed structures.

[0016] The present invention has the following beneficial effects:

[0017] This invention involves screening large-particle-size gravel raw materials, pre-removing coarse aggregates, and then mixing the fine aggregates. This ensures that the fine aggregates are more fully coated with the cementitious material, resulting in a denser filling within the overall framework and increased strength. On the other hand, the coarse aggregates themselves have good strength and do not require mixing, saving steps and costs. After the fine aggregates and cementitious material are evenly mixed, the coarse aggregates are added. Through spreading and compaction, the coarse aggregates achieve a uniform distribution with the mixture, thereby improving the overall strength of the cemented gravel and utilizing large-particle-size gravel to reduce waste generation. Detailed Implementation

[0018] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0019] Example 1:

[0020] The design parameters for cemented gravel in a certain project are: 90-day compressive strength of 6 MPa, strength guarantee rate of 80%; cement:fly ash ratio (reference value 4:6); the aggregate gravel raw material consists of natural gravel with a particle size of less than 300 mm, and its gradation is shown in Table 1; the raw material is screened with a screen aperture of 150 mm, and the gradation of the undersize fines is shown in Table 2. The mix proportion parameters of the cemented gravel are shown in Table 3.

[0021] Table 1. Proportions of different grades of gravel with a particle size of 300mm

[0022]

[0023] Table 2. Proportions of each grade of 150mm particle size gravel for mix proportioning test

[0024]

[0025] Table 3C 90 6 Recommended Cemented Gravel Mix Proportion Table

[0026]

[0027] Different types of gravel were used for mixing the cemented gravel, as detailed in Table 4. The gravel materials were as follows:

[0028] Option 1: The gravel smaller than 300mm in Table 1 is used directly as gravel material; it is mixed evenly with cement, admixture (fly ash), water and additive (water reducing agent). Due to the limitation that the particle size of the on-site mixing equipment cannot exceed 150mm, this option is to manually mix and cure in the laboratory, and then perform a full-grade compressive strength test after standard curing to the specified age, and compare it with options 2, 3 and 4.

[0029] Option 2: Use gravel smaller than 300mm from Table 1 as gravel material, but screen it before construction. The screen mesh size is 150mm. The undersize material is first mixed with cement, admixture (fly ash), water and additive (water reducing agent), and then the coarse material on the screen is added before spreading, rolling and curing.

[0030] Option 3: Use gravel smaller than 300mm from Table 1 as gravel material, but screen it before construction. The screen mesh size is 80mm. The undersize material is first mixed with cement, admixture (fly ash), water and additive (water reducing agent), and then the coarse material on the screen is added before spreading, rolling and curing.

[0031] Option 4: Use gravel smaller than 150mm from Table 2 as gravel material, mix it evenly with cement, admixture (fly ash), water and additive (water reducing agent), and then spread, compact and cure it.

[0032] Sampling and testing methods or refer to standard SL 678-2014. After on-site sampling, 600×600mm cubic compressive strength specimens are formed indoors and cured to the specified age. Full-gradient compressive strength test is then carried out. See Table 4 for details.

[0033] Table 4. Compressive strength of cemented gravel across different gradations under different fine-mixing and coarse-mixing schemes.

[0034]

[0035]

[0036] The results of the on-site core sample cutting test are shown in Table 5. Core sample 1 was sampled from the solid sample using the mixing process of Scheme 3; core sample 2 was sampled from the solid sample using the mixing process of Scheme 2. The core sample specimen size was 600mm×600mm. The two ends of the core sample specimen were ground flat on a grinding machine. Alternatively, cement paste, cement mortar, polymer cement mortar, epoxy putty, sulfur putty, or leveling material can be used. The cubic compressive strength test was performed on it, and the test method refers to SL352-2006 "Test Procedure for Hydraulic Concrete".

[0037] Table 5. Results of field sampling performance tests on cemented gravel

[0038]

[0039] The test results above show that the strength of the fully graded concrete, which is formed by mixing fine and coarse aggregates without the inclusion of aggregates larger than 80mm in the mixture, meets the design requirements and is higher than that of the fully graded concrete formed by mixing coarse and fine aggregates in one go and without the inclusion of aggregates larger than 150mm in the mixture. The strength obtained from core sampling also meets the design requirements. Therefore, it is evident that for low-strength cemented gravel, the strength is primarily determined by the coarse skeleton, rather than the interfacial strength between the aggregate and the cementitious material. The construction process described in this invention is feasible.

[0040] Example 2

[0041] For a certain project, the cemented crushed stone soil has an artificial crushed stone particle size of less than 400mm and a design strength grade of C. 180 6. Cement:fly ash ratio (reference value 5:5), its gradation is shown in Table 6; the raw materials are screened, and the gradation of the fine material under a 150mm sieve is shown in Table 7. The mix proportion parameters of cemented sand and gravel are shown in Table 8.

[0042] Table 6. Proportions of various grades of crushed stone soil with a particle size of 400mm

[0043]

[0044] Table 7. Proportions of each grade of gravel with a particle size of 150mm used in the mix proportion test.

[0045]

[0046] Table 8C 180 6 Recommended Mix Proportions for Cemented Crushed Stone Soil

[0047]

[0048] The mixture was divided into four groups. Group 2-1 was sieved using a 200mm sieve to separate fine and coarse materials; Group 2-2 was sieved using a 150mm sieve; Group 2-3 was sieved using a 100mm sieve; and Group 2-4 was sieved using an 80mm sieve. Group 2-5 was mixed and molded according to the current standard, removing materials larger than 150mm and using a different proportion for materials smaller than 150mm.

[0049] In the specific implementation of the indoor test, the cement, admixtures, water, additives, and fine materials in S1 were first mixed evenly; then the coarse materials were added to the aforementioned mixture to form 800×800mm specimens. After curing to the specified age, the full-gradient compressive strength test was carried out. The specific test results are shown in Table 9.

[0050] Table 9 Compressive strength of binders across different fine and coarse mixing schemes.

[0051]

[0052]

[0053] The experimental results from the above schemes show that the compressive strength of the fully graded cubic materials formed by using 200mm, 150mm, 100mm, and 80mm materials to differentiate between coarse and fine aggregates and employing a "fine mixing and coarse blending" process all meet the design C. 180 The mixing process meets the requirements of 6 and has minimal impact on strength, making it highly feasible on-site.

[0054] The construction process of this invention involves pre-removing coarse aggregates, mixing fine aggregates, and then incorporating the coarse aggregates into the paving process after the mixture is fully mixed. This "fine-mix, coarse-blending" or "mix-before-blending" process overcomes the limitation on the maximum particle size of cemented sand and gravel aggregates, and the prepared cemented sand and gravel meets relevant technical requirements. This method can expand the sources of raw materials and reduce production costs.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cemented sand gravel blending process based on large size aggregate, characterized in that, Includes the following steps: S1. Screen the sand and gravel aggregate containing large-diameter particles to separate it into coarse and fine materials. The screen mesh size is 80~150mm. The particle size of the large-diameter sand and gravel is less than 400mm, and the maximum particle size is ≤2 / 3 of the thickness of the cemented sand and gravel. The large-diameter sand and gravel includes natural sand and gravel, artificial sand and gravel, excavated stone chips or crushed stone and soil. S2. Mix the cement, admixtures, water, additives and fine materials from S1 evenly. S3. Add the coarse material from S1 to the mixture obtained in S2 and then load it onto the truck, or add the coarse material from S1 to the mixture obtained in S2 during the loading process. Transport it to the construction site for paving, compaction and curing to complete the construction of cemented gravel.

2. The mixing process of claim 1, wherein: During screening in S1, particles smaller than 80mm are considered fine materials, while the rest are considered coarse materials.

3. The mixing process according to claim 1, characterized in that: The mixing time in S2 is 2-3 minutes.

4. Cemented gravel obtained by the mixing process described in any one of claims 1 to 3.

5. The application of the cemented gravel as described in claim 4 in cemented dams, cemented gravel enhancement zones, or roadbed structures.

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