A roadbed filling material and a method for preparing the same

Abstract

The application discloses a kind of roadbed filling material and preparation method thereof, belong to road laying material technical field.The material is made of the following mass percentage components: aerated concrete waste 10~20%, mine stripping soil 10~20%, cementing material 5~15%, tailings sand 45~75%.Cementing material includes high calcium oxide-bellyt cementing material 1~3%, sulphoaluminate cement clinker 2~5%, calcined mine stripping soil 70~80%, anhydrite 10~25%.When preparing, each raw material is mixed to obtain dry material according to the proportion, and dry material is uniformly mixed with water.The application uses aerated concrete waste and mine stripping soil as main raw materials, realizes the collaborative resource utilization of multiple solid wastes, and the obtained material has excellent early strength and frost resistance, effectively overcomes the defects such as shrinkage cracking and low early strength of traditional materials, and has low cost, convenient construction, and can be widely used in roadbed construction.

Description

Technical Field

[0001] This invention relates to the field of road paving materials technology, specifically to a roadbed filling material and its preparation method. Background Technology

[0002] As a new type of green wall material, autoclaved aerated concrete (AAC) is being used more and more widely. However, due to its relatively low strength, it is easily damaged during production or transportation, resulting in substandard products. At the same time, the amount of AAC waste generated from building demolition is also increasing daily. Currently, the reuse rate of this type of waste is low, existing applications are limited, and the added value is not high, necessitating the expansion of high-value application pathways.

[0003] In current road construction, the main roadbed materials are natural sand and gravel and ordinary cement-stabilized soil, which presents many challenges: First, natural sand and gravel resources are becoming increasingly scarce and their prices are rising, increasing construction costs; second, traditional roadbed materials suffer from severe shrinkage cracking, poor frost resistance, and low early strength, which can easily lead to roadbed settlement and damage; third, the production of traditional materials consumes a lot of energy and generates a lot of carbon emissions, which is inconsistent with the national low-carbon and environmental protection policy; and fourth, traditional materials are difficult to meet the requirements of lightweight and high strength for special scenarios such as soft soil foundations.

[0004] Limestone mine overburden is a major solid waste generated during mining, with an annual production exceeding 100 million tons. Currently, its resource utilization rate is low, and it is mostly used for mine revegetation and simple backfilling, with a severe lack of high-value applications. Using mine overburden for roadbed material preparation has advantages such as abundant resources, low cost, and good performance adaptability.

[0005] In summary, how to utilize aerated concrete waste and mine stripping soil to prepare high-performance, environmentally friendly, and low-carbon roadbed materials, and realize the synergistic resource utilization of multiple types of solid waste, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing and applying environmentally friendly roadbed materials. This method uses aerated concrete waste, mine stripping soil, low-carbon cementitious materials, and tailings sand as raw materials. By optimizing the raw material ratio and preparation process, it achieves the synergistic resource utilization of multiple types of solid waste. The resulting roadbed material can meet various requirements for road construction and has the characteristics of being environmentally friendly, low-carbon, low-cost, and highly practical.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, a roadbed filling material is provided, comprising the following components by mass percentage: Waste material from aerated concrete: 10-20%; Overburden from mines: 10-20%; Cementitious materials: 5~15%; Tailings: 45-75%; The cementitious material comprises the following components by weight percentage: 1-3% high-calcium oxide-belite cementitious material, 2-5% sulfoaluminate cement clinker, 70-80% calcined mine stripping soil, and 10-25% anhydrite.

[0008] Furthermore, after being crushed and ground, the waste material of aerated concrete is controlled with a particle size of 0.075~4.75 mm, of which fine powder with a particle size of 0.075~0.3 mm accounts for 5~30% and fine aggregate with a particle size of 0.3~4.75 mm accounts for 70~85%.

[0009] Furthermore, the mine overburden is the surface waste soil generated during the limestone mining process, and its chemical composition by mass percentage includes: SiO2 42.5%~45.1%, Al2O3 12.4%~14.2%, and CaO 1.8%~2.0%.

[0010] Furthermore, the tailings sand is one or more of the following: quartz tailings sand, graphite tailings sand, iron tailings sand, copper tailings sand, gold tailings sand, and tungsten tailings, with a moisture content ≤8% and a median particle size ≤0.1mm.

[0011] Furthermore, the specific surface area of ​​the calcined mine overburden is >420 m². 2 / kg.

[0012] Furthermore, the mineral composition of the high-calcium oxide-belite cementitious material, by mass percentage, includes: f-CaO 25~34%, 3~10%, C2S 25~35%, C3S 8~16%, CaSO4 3~7%.

[0013] Furthermore, the high-calcium oxide-belite cementitious material is calcined at 1300~1350℃.

[0014] Furthermore, the specific surface area of ​​the high-calcium oxide-belite cementitious material is 380~420 m². 2 / kg.

[0015] Furthermore, in the mineral composition of sulfoaluminate cement clinker, Content > 45%, and The sum of its content with C2S is >70%.

[0016] On the other hand, a method for preparing the above-mentioned roadbed filling material is provided, comprising the following steps: weighing aerated concrete waste, mine stripped soil, cementitious material and tailings sand according to the proportion, and mixing them to obtain dry material; uniformly mixing the dry material with water to obtain roadbed filling material; The amount of water used accounts for 8% to 20% of the total dry material mass, including the moisture contained in the tailings sand itself.

[0017] It should be noted that the amount of water used in this invention refers to the total amount of water involved in the hydration reaction and molding process, including added water and the moisture already contained in the raw materials. Since raw materials such as tailings sand may contain a certain amount of free water, this water will participate in the hydration reaction of the cementitious material during mixing and affect the workability of the mixture. Therefore, the moisture contained in the tailings sand itself must be included in the total water usage during the preparation process.

[0018] In the specific preparation process, the raw materials are first weighed and mixed according to the formula to obtain dry material, and the actual moisture content of the tailings sand is measured. The total water consumption is calculated based on the total mass of the dry material, which is 8% to 20% of the total mass of the dry material. Based on the total water consumption and the actual moisture content of the tailings sand, the amount of additional water that needs to be added is calculated. The added water is then mixed evenly with the dry material until the total moisture content of the mixture reaches 8% to 20% of the total mass of the dry material, thus obtaining the roadbed material.

[0019] To ensure the quality of roadbed material preparation, the total moisture content of the mixture must be controlled within the target range. If the moisture content of the tailings sand is higher than 8%, it can be reduced beforehand by natural drying or other methods; or during subsequent mixing, the amount of water added should be reduced accordingly based on the actual moisture content of the tailings sand, so that the total water consumption is controlled within the range of 8% to 20% of the total dry material mass. If the moisture content of the tailings sand is lower than 8%, the total water consumption required should be calculated based on the total dry material mass, and after deducting the moisture content of the tailings sand itself, the amount of water added should be increased to the target range.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses industrial solid waste such as aerated concrete waste, mine stripping soil, and tailings sand as the main raw materials, with a total solid waste content of over 80%. It solves the problems of low resource utilization rate and limited application scenarios of aerated concrete waste and mine stripping soil in the existing technology, and reduces the ecological pollution caused by natural sand and gravel mining and solid waste landfill.

[0021] 2. To address the problems of severe shrinkage cracking, poor frost resistance, and low early strength in traditional cement-stabilized soil, this invention utilizes a specific ratio of cementitious material system (high calcium oxide-belite cementitious material, sulfoaluminate cement clinker, calcined mine stripping soil, and anhydrite) to activate solid waste activity and optimize the particle size distribution of aerated concrete waste (co-aggregate of fine powder and fine aggregate). This results in a roadbed filling material with high early strength and 28-day strength, and low strength and mass loss rates after freeze-thaw cycles. This effectively reduces the risk of roadbed settlement and damage, and extends the service life of roads.

[0022] 3. The aerated concrete waste, mine stripping soil, and tailings sand used in this invention are all industrial solid wastes, which are abundant and inexpensive, and can be sourced locally, greatly reducing the cost of raw material procurement. The preparation process is compatible with the traditional roadbed material construction process, and no new special equipment is required. It is only necessary to control the total mixing water (including the moisture content of the tailings sand itself) within the range of 8% to 20% to achieve large-scale construction. The promotion threshold is low, and it is especially suitable for roadbed construction in scenarios such as roads around mines and rural roads. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] The main raw material sources and processing methods used in the embodiments of the present invention are as follows: The waste material for aerated concrete is taken from demolished buildings or substandard products from factories. After crushing, grinding and screening, the particle size is controlled to be 0.075-4.75 mm, of which fine powder (0.075-0.3 mm) accounts for 5-30 wt.% and fine aggregate (0.3-4.75 mm) accounts for 70-85 wt.%.

[0025] The mine overburden is taken from the surface waste soil generated during the limestone mining stage. Its main chemical components include SiO4 2.5%~45.1%, Al2O3 12.4%~14.2%, and CaO 1.8%~2.0%. It is dried, crushed, and impurity removed before use.

[0026] The tailings sand is made of quartz tailings sand with a moisture content of ≤8% and a median particle size of ≤0.1mm.

[0027] The cementitious material is a compound made of high-calcium oxide-belite cementitious material, sulfoaluminate cement clinker, calcined mine overburden, and anhydrite in a specific ratio. The calcined mine overburden has a specific surface area >420 m². 2 / kg; The mineral composition of high calcium oxide-Beilite cementitious materials, by mass percentage, includes: f-CaO 25~34%, It contains 3-10% C2S, 25-35% C3S, 8-16% CaSO4, and is calcined at 1300-1350℃, with a specific surface area of ​​380-420 m². 2 / kg; in sulfoaluminate cement clinker Content > 45%, The sum of its content with C2S is >70%.

[0028] The raw material mixes for the roadbed filling materials in various embodiments and comparative examples of the present invention are shown in Table 1. The amounts of aerated concrete waste, mine stripping soil, cementitious materials, and tailings sand are all calculated as a percentage of their total weight; the amount of water (including the moisture content of the tailings sand itself) is 8% to 20% of the total dry material mass.

[0029] Table 2. Mix proportions of roadbed materials in the examples and comparative examples

[0030] The cementitious materials used in Examples 1, 2, 3, and 4 of this invention have the same composition, including the following components by mass percentage: 3% high-calcium oxide-belite cementitious material, 5% sulfoaluminate cement clinker, 80% calcined mine stripping soil, and 12% anhydrite.

[0031] The cementitious materials used in Examples 3 and 4 of this invention have the same composition, including the following components by mass percentage: 3% high-calcium oxide-belite cementitious material, 5% sulfoaluminate cement clinker, 75% calcined mine stripping soil, and 17% anhydrite.

[0032] The cementitious material used in Example 5 of this invention comprises the following components by mass percentage: 3% high-calcium oxide-belite cementitious material, 5% sulfoaluminate cement clinker, 78% calcined mine stripping soil, and 14% anhydrite.

[0033] The cementitious material used in Example 6 of this invention comprises the following components by mass percentage: 3% high-calcium oxide-belite cementitious material, 5% sulfoaluminate cement clinker, 82% calcined mine stripping soil, and 10% anhydrite.

[0034] The cementitious material used in Comparative Example 1 of the present invention comprises the following components by mass percentage: 1% high-calcium oxide-belite cementitious material, 7% sulfoaluminate cement clinker, 80% calcined mine stripping soil, and 12% anhydrite.

[0035] The cementitious material used in Comparative Example 2 of this invention comprises the following components by mass percentage: 7% high-calcium oxide-belite cementitious material, 1% sulfoaluminate cement clinker, 80% calcined mine stripping soil, and 12% anhydrite.

[0036] The preparation method of the roadbed material of the present invention is as follows: S1. Weigh out the aerated concrete waste material, mine stripped soil, cementitious material, and tailings sand according to the proportions in Table 1, and mix them evenly to obtain dry material. At the same time, determine the actual moisture content of the tailings sand.

[0037] S2. Calculate the required water amount based on the total mass of the dry material. The water amount should be 8% to 20% of the total mass of the dry material. Calculate the amount of additional water needed by deducting the water content of the tailings sand itself from the actual moisture content of the tailings sand.

[0038] The calculated added water is uniformly mixed with the dry material prepared in S1, so that the total moisture content of the mixture reaches 8% to 20% of the total mass of the dry material. The uniformly mixed material is then spread, compacted, and cured according to conventional roadbed construction methods.

[0039] The performance of the subgrade materials prepared in the above embodiments and comparative examples was tested according to the test methods specified in JTG E51-2009 "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering". The results are shown in Table 2.

[0040] Table 2 Test results of physical and mechanical properties of roadbed materials

[0041] As can be seen from Table 3: The roadbed filling materials prepared in Examples 1-6 have an unconfined compressive strength of 0.7-2.3 MPa at 7 days, an unconfined compressive strength of 2.1-3.6 MPa at 28 days, a strength loss rate of 7.8-10.9% after 10 freeze-thaw cycles, and a mass loss rate of 4.0%-4.9%. All performance indicators meet the basic requirements for roadbed filling materials in road construction.

[0042] Comparing Examples 1 and 2, 3 and 4, and 5 and 6, it can be seen that when the cementitious material content is reduced from 10% to 5%, the 7-day and 28-day strengths of the roadbed filling materials (Examples 2 and 4) decrease significantly, indicating that the cementitious material content has a significant impact on strength development. The 5% to 15% range specified in this invention can meet the requirements of different strength levels.

[0043] Comparing Examples 1, 3, and 5 with Comparative Examples 1 and 2, it is evident that when the ratio of high-calcium oxide-belite cementitious material to sulfoaluminate cement clinker deviates from the range defined in this invention (1-3% and 2-5%), the strength of the subgrade material significantly decreases, and the strength loss rate and mass loss rate after freeze-thaw cycles increase markedly. Specifically, the 28-day strength of Comparative Example 1 (1% high-calcium oxide-belite cementitious material and 7% sulfoaluminate cement clinker) is only 1.8 MPa, with a strength loss rate of 11.8%; the 28-day strength of Comparative Example 2 (7% high-calcium oxide-belite cementitious material and 1% sulfoaluminate cement clinker) is only 1.7 MPa, with a strength loss rate as high as 14.2% and a mass loss rate of 8.2%. This indicates that the synergistic effect of high-calcium oxide-belite cementitious material and sulfoaluminate cement clinker within a specific ratio range is key to achieving excellent performance in subgrade materials.

[0044] Comparing Example 1 with Comparative Example 3 (3% cementitious material content, lower than the lower limit of 5% of the present invention), it can be seen that the 7-day strength of Comparative Example 3 is only 0.2 MPa, and the 28-day strength is only 1.0 MPa, with a strength loss rate of 14.6%, which is much higher than that of Example 1. This indicates that when the cementitious material content is lower than the lower limit of the present invention, it cannot provide sufficient cementitious activity, resulting in insufficient strength and poor frost resistance of the roadbed material.

[0045] Comparing Example 1 with Comparative Example 4 (18% cementitious material content, higher than the upper limit of 15% in this invention), it can be seen that Comparative Example 4 has a 7-day strength of 3.5 MPa and a 28-day strength of 5.1 MPa, with a strength loss rate of only 7.0% and a mass loss rate of only 3.5%, which is superior to Example 1. However, excessively high cementitious material content will increase material costs. From the perspective of resource utilization, this invention aims to achieve the highest possible solid waste content while ensuring road performance. The limited range of 5% to 15% can achieve a balance between performance, cost, and environmental benefits.

[0046] In summary, this invention, through the synergistic compounding of a specific ratio of cementitious material system with aerated concrete waste, mine stripping soil, and tailings sand, achieves high-volume resource utilization of various solid wastes while giving the resulting roadbed material excellent mechanical properties and freeze-thaw resistance, effectively overcoming the performance shortcomings of traditional roadbed materials.

[0047] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. 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. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A roadbed filling material, characterized in that, The components include the following percentages by mass: Waste material from aerated concrete: 10-20%; Overburden from mines: 10-20%; Cementitious materials: 5~15%; Tailings: 45-75%; The cementitious material comprises the following components by weight percentage: 1-3% high-calcium oxide-belite cementitious material, 2-5% sulfoaluminate cement clinker, 70-80% calcined mine stripping soil, and 10-25% anhydrite.

2. The roadbed filling material according to claim 1, characterized in that, After being crushed and ground, the waste material of aerated concrete is controlled with a particle size of 0.075~4.75 mm, of which fine powder with a particle size of 0.075~0.3 mm accounts for 5~30% and fine aggregate with a particle size of 0.3~4.75 mm accounts for 70~85%.

3. The roadbed filling material according to claim 1, characterized in that, Overburden from mines is the surface waste soil generated during the mining of limestone. Its chemical composition, by mass percentage, includes: SiO2 42.5%~45.1%, Al2O3 12.4%~14.2%, and CaO 1.8%~2.0%.

4. The roadbed filling material according to claim 1, characterized in that, The tailings sand is one or more of the following: quartz tailings sand, graphite tailings sand, iron tailings sand, copper tailings sand, gold tailings sand, and tungsten tailings. Its moisture content is ≤8% and its median particle size is ≤0.1mm.

5. A roadbed filling material according to claim 1, characterized in that, The specific surface area of ​​calcined mine overburden is >420 m². 2 / kg.

6. The roadbed filling material according to claim 1, characterized in that, The mineral composition of high-calcium oxide-Beilite cementitious materials, by mass percentage, includes: f-CaO 25~34%, 3~10%, C2S 25~35%, C3S 8~16%, CaSO4 3~7%.

7. A roadbed filling material according to claim 1, characterized in that, High-calcium oxide-Beilite cementitious material is calcined at 1300~1350℃.

8. A roadbed filling material according to claim 1, characterized in that, The specific surface area of ​​high calcium oxide-Beilite cementitious materials is 380~420m². 2 / kg.

9. A roadbed filling material according to claim 1, characterized in that, In the mineral composition of sulfoaluminate cement clinker, Content > 45%, and The sum of its content with C2S is >70%.

10. A method for preparing the roadbed filling material as described in any one of claims 1 to 9, characterized in that, The process includes the following steps: Weigh out aerated concrete waste, mine stripping soil, cementitious materials and tailings sand according to the proportions, and mix them to obtain dry material; Mix the dry material with water evenly to obtain roadbed filling material; The amount of water used accounts for 8% to 20% of the total dry material mass, including the moisture contained in the tailings sand itself.

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