A solid waste-based road base material and its preparation method

Abstract

This invention discloses a solid waste-based road base material, comprising the following components and their respective weight percentages: 50-300 parts of a solidifying component, 300-1000 parts of a skeleton component, and 5-80 parts of an activation component. The solidifying component includes high-calcium fly ash and waste slurry from a mixing plant; the skeleton component includes filter press material and aggregate undersize; and the activation component includes waste gypsum powder, water glass, and a silane coupling agent. This invention, while achieving resource utilization of various industrial waste residues, effectively balances the mechanical properties, durability, and water stability of the resulting road base material. Furthermore, the preparation process is relatively simple, has wide applicability, and offers significant economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of building materials and solid waste utilization technology, specifically relating to a pavement base material based on all-industrial solid waste and its preparation method. Background Technology

[0002] With the increasing demands for green production in concrete mixing plants, the pollution problem caused by waste slurry generated during concrete production urgently needs to be addressed. The cleaning of concrete production facilities, concrete transport vehicles, and sites generates significant amounts of wastewater, waste slurry, and solid waste. This waste slurry contains large amounts of alkaline substances, and a certain amount of Cl... - SO4 2_ Direct discharge of hazardous substances such as slurry from concrete mixing plants can severely pollute surrounding water and soil resources, and even clog nearby municipal pipe networks. Therefore, the resource-based recycling and reuse of waste slurry and solid waste from mixing plants is a focus of green building materials research.

[0003] The washing process for producing aggregates generates a large amount of tailings. These tailings are typically processed through hydrocyclone separation, flocculation sedimentation, and filter press dewatering to form filter cakes. Simultaneously, the aggregate production process, including crushing and screening, also produces a significant amount of aggregate undersize. These two types of waste resources account for up to 30% of aggregate production, and their disposal leads to substantial resource waste, land occupation, and environmental pollution. Current technologies primarily utilize filter presses and aggregate undersize in concrete and autoclaved brick production.

[0004] Currently, most road construction methods involve solidifying the soil with cement, sand, and gravel, consuming large amounts of cement and natural mineral resources, resulting in poor economic efficiency and a high carbon footprint. Furthermore, conventional water-stabilized base materials suffer from low strength, poor durability, high shrinkage, and susceptibility to cracking, leading to unstable road base layers. Many road surfaces even experience the phenomenon of "repairing this year and breaking down next year," significantly increasing road maintenance and repair costs. Therefore, further exploration of low-cost, high-performance, and environmentally friendly road base materials that meet the needs of practical road engineering is of significant research and application importance. Summary of the Invention

[0005] This invention addresses the problems and shortcomings of existing technologies by providing a solid waste-based road base material. The road base material is made from a variety of industrial wastes, turning waste into treasure and achieving recycling. Moreover, the prepared road base material has good mechanical properties, volume stability, and water stability, and can be widely used in various road engineering projects.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A solid waste-based road base material, comprising the following components and their respective weight percentages: 50-300 parts of a solidifying component, 300-1000 parts of a skeleton component, and 5-80 parts of an activation component; wherein the solidifying component includes high-calcium fly ash and waste slurry from a mixing plant; the skeleton component includes filter press material and aggregate undersize material; and the activation component includes waste gypsum powder, water glass, and a silane coupling agent.

[0008] Further, the solidification component includes: 100-200 parts of high-calcium fly ash and 100-150 parts of waste slurry from the mixing plant; the skeleton component includes: 300-550 parts of filter press material and 200-350 parts of aggregate undersize material; the activation component includes: 20-40 parts of waste gypsum powder, 10-20 parts of water glass, and 3-8 parts of silane coupling agent.

[0009] In the above scheme, the high-calcium fly ash contains 15-25 wt% CaO, ≥60 wt% Al2O3+SiO2, and has a specific surface area of ​​500-950 m². 2 / kg.

[0010] In the above scheme, the waste slurry from the mixing plant has a moisture content of 80-95%, a pH of 10-13, and an aging time of <24h.

[0011] Preferably, the waste slurry from the mixing plant has a moisture content of 85-95% and an aging time of <6 hours.

[0012] In the above scheme, the filter press material comes from the tailings produced after the wet aggregate production slurry undergoes flocculation, filter pressing, dewatering and other processes, with a moisture content of 15-50% and a particle content of ≤25% for particles larger than 45μm.

[0013] Preferably, the moisture content of the filter press is 20-30%.

[0014] In the above scheme, the particle size of the aggregate undersize is 0-16 mm.

[0015] Preferably, the proportion of 0-5mm particles in the aggregate undersize is 20-50%, and the proportion of 5-16mm particles is 50-80%.

[0016] In the above scheme, the waste gypsum powder is one or a combination of two or more of desulfurized gypsum, phosphogypsum, and titanium gypsum, with a calcium sulfate dihydrate content >85% and a specific surface area of ​​200-400 m². 2 / kg.

[0017] In the above scheme, the modulus of the water glass is 1.8 to 3.4, and the water content is ≤55%.

[0018] In the above scheme, the silane coupling agent is a hydrolysate with a concentration of 40-80%, wherein acetic acid is used to adjust the pH to 4-6.5 to promote hydrolysis.

[0019] Furthermore, the silane coupling agent may be one or more of KH550, KH570, etc.

[0020] The above-mentioned method for preparing a solid waste-based road base material includes the following steps:

[0021] 1) Put the waste slurry, filter press material and aggregate screened material from the mixing plant into the mixer and mix for one time (5-30s);

[0022] 2) Then add high-calcium fly ash and stir a second time (20-60s);

[0023] 3) Finally, add the active activating component and stir evenly (30-60s) to obtain the road base material.

[0024] The all-solid waste pavement base material prepared according to the above scheme has the following properties: 7-day unconfined compressive strength > 2.2 MPa, 28-day unconfined compressive strength > 4.5 MPa, 28-day water stability coefficient > 80%, strength ratio after 5 freeze-thaw cycles > 70%, and 90-day drying shrinkage coefficient < 650 × 10⁻⁶. -6 At the same time, it can dispose of large quantities of industrial by-products such as aggregate filter press tailings, aggregate undersizes, mixing plant waste slurry, and waste gypsum, resulting in significant environmental and economic benefits.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) This invention utilizes water glass and waste slurry from mixing plants to provide a highly alkaline environment, which causes the Si-O and Al-O bonds in the glassy body of fly ash to break and reconstruct to form network structures such as CASH and NASH gels; at the same time, it promotes the further hydration of unhydrated cementitious materials in the waste slurry from mixing plants in an alkaline environment, with various hydration products intertwined, resulting in a denser microstructure and promoting a steady improvement in the mechanical properties of road base materials.

[0027] 2) The main chemical component of the introduced waste gypsum is calcium sulfate dihydrate, which can effectively regulate the hydration rate of cementitious materials and solve the problem of excessively rapid hydration and hardening in alkali-activated systems. At the same time, it can react with hydration products to generate ettringite with delayed expansion, which can effectively fill the internal pores of the material and inhibit the problem of large early shrinkage and easy cracking in alkali-activated systems, thereby improving the mechanical properties and volume stability of road base materials.

[0028] 3) During hydrolysis, the silane coupling agent forms a large amount of silanol, which couples with CSH and the silicate groups on the surface of cement particles, gradually undergoing a chemical bonding reaction to form fibrous silane polymers. The fibrous products are uniformly distributed inside the material, interpenetrating in the hydration products and acting as a bridge in the network structure. They form a cross-linked interpenetrating structure with the hydration products, making the skeleton of the road base material more dense and stable, thereby improving the mechanical properties and durability of the road base material. At the same time, the silane coupling agent component can improve the waterproofness of the material, inhibit the absorption and diffusion of water in the capillary of the material, and further improve the water stability of the road base material.

[0029] 4) The road base material described in this invention uses a variety of industrial waste residues as the main raw materials, and the solid waste resource utilization rate reaches more than 90%, providing an industrial waste residue disposal solution with significant economic and environmental benefits.

[0030] 5) The road base material prepared by this invention has good mechanical properties, volume stability and water stability, and can be widely used in various road engineering projects. Detailed Implementation

[0031] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0032] In the following examples, the fly ash used is Class III C, with a CaO content of 18%, an Al2O3+SiO2 content of 75%, and a specific surface area of ​​600 m². 2 / kg; the waste slurry from the mixing plant has a moisture content of 88%, a pH value of 12.5, and an aging time of 3 hours; the filter press has a moisture content of 26%; the aggregate undersize particle size is 0–16 mm, with 0–5 mm accounting for 25% and 5–16 mm accounting for 75%; the waste gypsum powder is desulfurized gypsum with a calcium sulfate dihydrate content of 90% and a specific surface area of ​​350 m² / kg. 2 / kg; the water glass is commercially available water glass with a modulus of 2.0 and a water content of 45%; the silane coupling agent is a hydrolysate of γ-aminopropyltriethoxysilane (KH550) (with the pH adjusted to 5.5 by acetic acid) and a concentration of 55%.

[0033] In the following embodiments, the sampling, molding, curing, mechanical properties, frost resistance and drying shrinkage properties of the specimen raw materials were tested in accordance with the relevant provisions of the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG E51-2009).

[0034] Water stability coefficient test: Φ100mm×100mm specimens were formed, cured for 28 days, and then immersed in water for 28 days. The compressive strength of the specimens after 28 days of immersion was tested, and the corresponding water stability coefficient was calculated.

[0035] The calculation formula is:

[0036] K w -R t / R0

[0037] In the formula:

[0038] Kw—Water stability coefficient of the specimen (%);

[0039] Rt—Unconfined compressive strength (MPa) of the specimen when soaking time is t;

[0040] R0—Unconfined compressive strength (MPa) of a standard cured specimen after 28 days.

[0041] Example 1

[0042] A type of industrial solid waste road base material, comprising the following raw materials and their respective weight proportions: 110 parts high-calcium fly ash, 120 parts waste slurry from mixing plants; 500 parts filter press material, 330 parts aggregate undersize material, 22 parts waste gypsum powder, 12 parts water glass, and 3 parts silane coupling agent; the specific preparation method includes the following steps:

[0043] 1) Add the waste slurry from the mixing plant, filter press material, and aggregate undersize material into the mixer and mix for 10 seconds each time;

[0044] 2) Then add fly ash and stir again for 30 seconds;

[0045] 3) Finally, add the active activating component and stir evenly for 60 seconds to obtain the road base material.

[0046] Example 2

[0047] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 160 parts of high-calcium fly ash, 135 parts of mixing plant waste slurry, 450 parts of filter press material, 300 parts of aggregate undersize material, 30 parts of waste gypsum powder, 15 parts of water glass, and 5 parts of silane coupling agent.

[0048] Example 3

[0049] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 190 parts high-calcium fly ash, 140 parts waste slurry from mixing plants, 450 parts filter press material, 300 parts aggregate undersize, 30 parts waste gypsum powder, 18 parts water glass, and 8 parts silane coupling agent.

[0050] Comparative Example 1

[0051] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 2, except that the raw materials and their weight proportions are as follows: 160 parts of high-calcium fly ash, 94.5 parts of water, 550 parts of filter press, 200 parts of aggregate undersize, 30 parts of waste gypsum powder, 15 parts of water glass, and 5 parts of silane coupling agent.

[0052] Comparative Example 2

[0053] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 2, except that the raw materials and their weight proportions are as follows: 160 parts of high-calcium fly ash, 135 parts of waste slurry from mixing plants, 450 parts of filter press material, 300 parts of aggregate undersize material, 0 parts of waste gypsum powder, 15 parts of water glass, and 5 parts of silane coupling agent.

[0054] Comparative Example 3

[0055] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 2, except that the raw materials and their weight proportions are as follows: 160 parts of high-calcium fly ash, 135 parts of waste slurry from mixing plants, 450 parts of filter press material, 300 parts of aggregate undersize material, 30 parts of waste gypsum powder, 15 parts of water glass, and 0 parts of silane coupling agent.

[0056] Comparative Example 4

[0057] A type of industrial solid waste road base material is prepared in a manner similar to that of Example 2, except that the raw materials and their weight proportions are as follows: 160 parts of high-calcium fly ash, 135 parts of waste slurry from mixing plants, 450 parts of filter press material, 300 parts of aggregate undersize material, 30 parts of waste gypsum powder, 15 parts of sodium carbonate, and 5 parts of silane coupling agent.

[0058] Comparative Example 5

[0059] A cement-stabilized soil pavement base material, wherein the raw materials and their weight proportions are: 200 parts of PO42.5 cement, 800 parts of clay, 10 parts of calcium chloride, and 170 parts of water; the pavement base material is obtained by mixing the above materials evenly.

[0060] Comparative Example 6

[0061] A type of lime-stabilized soil pavement base material, wherein the raw materials and their weight proportions are: 150 parts of PO42.5 cement, 50 parts of fly ash, 800 parts of clay, 10 parts of calcium chloride, and 170 parts of water; the pavement base material is obtained by mixing the above materials evenly.

[0062] The road base materials obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests such as mechanical properties, water stability coefficient, frost resistance and drying shrinkage. The results are shown in Table 1.

[0063] Table 1. Performance test results of the road base materials obtained in Examples 1-3 and Comparative Examples 1-5

[0064]

[0065] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A solid waste-based road base material, characterized in that, The components and their respective weight percentages include: 50-300 parts of solidification component, 300-1000 parts of skeleton component, and 5-80 parts of activation component; wherein the solidification component includes high-calcium fly ash and waste slurry from the mixing plant; the skeleton component includes filter press material and aggregate undersize material; and the activation component includes waste gypsum powder, water glass, and silane coupling agent. The high-calcium fly ash contains 15-25 wt% CaO, ≥60 wt% Al2O3+SiO2, and has a specific surface area of ​​500-950 m². 2 / kg; The waste slurry from the mixing plant has a moisture content of 80-95%, a pH of 10-13, and an aging time of <24h. The solidification component includes: 100-200 parts of high-calcium fly ash and 100-150 parts of waste slurry from the mixing plant; the skeleton component includes: 300-550 parts of filter press material and 200-350 parts of aggregate undersize material; the activation component includes: 20-40 parts of waste gypsum powder, 10-20 parts of water glass, and 3-8 parts of silane coupling agent. The silane coupling agent is a hydrolysate with a concentration of 40-80%; the pH is adjusted to 4-6.5 using acetic acid. The preparation method of the solid waste-based road base material includes the following steps: 1) The waste slurry from the mixing plant, the filter press material and the aggregate screened material are put into the mixer and mixed once for 5 to 30 seconds; 2) Then add high-calcium fly ash and stir again for 20-60 seconds; 3) Finally, add the active activating component, stir evenly, and after 30-60 seconds, the road base material is obtained.

2. The solid waste-based road base material according to claim 1, characterized in that, The filter press material is derived from the tailings produced after flocculation, filtration, and dewatering of the slurry from wet aggregate production. It has a moisture content of 15-50% and a particle content of ≤25% for particles larger than 45μm.

3. The solid waste-based road base material according to claim 1, characterized in that, The particle size of the aggregate undersize is 0–16 mm.

4. The solid waste-based road base material according to claim 1, characterized in that, The waste gypsum powder is one or a combination of two or more of desulfurized gypsum, phosphogypsum, and titanium gypsum, with a calcium sulfate dihydrate content >85% and a specific surface area of ​​200–400 m². 2 / kg.

5. The solid waste-based road base material according to claim 1, characterized in that, The water glass has a modulus of 1.8 to 3.4 and a water content of ≤55%.

6. A method for preparing the solid waste-based pavement base course material according to any one of claims 1 to 5, characterized in that, Includes the following steps: 1) The waste slurry from the mixing plant, filter press material, and aggregate undersize material are fed into the mixer for one mixing. 2) Then add high-calcium fly ash and mix again; 3) Finally, add the active activating component, stir evenly, and obtain the road base material.

Images