Road base material based on sludge and construction waste, preparation method and application

Abstract

This invention provides a road base material based on sludge and construction waste, its preparation method, and its application. The road base material includes a base component and an admixture component. The base component includes: 45-55% recycled coarse aggregate, 20-35% recycled fine aggregate, 15-25% sludge, 4-6% cement, and 1-4% water. Both the recycled coarse and fine aggregates are derived from construction waste. The admixture component includes quicklime, sodium hydroxide, and zinc ricinoleate. The mass percentage of quicklime to sludge is 4-8%, the mass percentage of sodium hydroxide to sludge is 0.1-0.2%, and the mass percentage of zinc ricinoleate to sludge is 0.2-0.5%. This invention promotes the high-value utilization of urban solid waste such as sludge and construction waste, and yields a higher-performance road base material based on sludge and construction waste.

Description

Technical Field

[0001] This invention relates to road base materials, and more particularly to a road base material based on sludge and construction waste, its preparation method, and its application. Background Technology

[0002] Treating 10,000 tons of wastewater generates 5 to 10 tons of sludge (based on an 80% moisture content). The sludge has a complex composition, containing not only organic matter and heavy metals but also high moisture content, making it difficult to treat. With the increase in wastewater treatment facilities, sludge production is on the rise. Achieving sludge reduction, harmlessness, and resource utilization is a major challenge. Meanwhile, construction waste has a large stockpile, but its resource utilization rate and treatment level are generally low, resulting in low added value. Therefore, providing a low-cost, environmentally friendly, and large-scale applicable method for the co-utilization of sludge and construction waste is the best way to solve these problems.

[0003] Chinese invention patent CN115448655B discloses a road base material based on construction waste and its preparation method. The basic components of the road base material include construction waste, renovation waste, waste incineration fly ash, cement, slag, and water; the external admixtures include alkylphenol polyoxyethylene ether, sodium dodecyl sulfate, and glycerol. While this patent can improve the performance of road base materials and reduce the toxicity of waste based on construction waste, the performance of the road base material obtained from construction waste still needs further improvement in terms of strength and other properties. Moreover, this patent does not involve sludge, which is more difficult to treat due to its high toxicity and high water content. Therefore, this patent does not yield a higher-performance road base material based on sludge and construction waste.

[0004] Therefore, it is necessary to provide a road base material based on sludge and construction waste, its preparation method, and its application, in order to solve the technical problem of how to obtain a higher performance road base material based on sludge and construction waste. Summary of the Invention

[0005] The main objective of this invention is to provide a road base material based on sludge and construction waste, its preparation method, and its application, aiming to solve the technical problem of how to obtain a higher performance road base material based on sludge and construction waste.

[0006] To achieve the above objectives, the present invention provides a road base material based on sludge and construction waste, the road base material comprising a base component and an admixture component;

[0007] The basic components include: 45-55% recycled coarse aggregate, 20-35% recycled fine aggregate, 15-25% sludge, 4-6% cement, and 1-4% water; both the recycled coarse aggregate and the recycled fine aggregate are derived from construction waste.

[0008] The external admixtures include quicklime, sodium hydroxide, and zinc ricinoleate; the mass percentage of quicklime to sludge is 4-8%, the mass percentage of sodium hydroxide to sludge is 0.1-0.2%, and the mass percentage of zinc ricinoleate to sludge is 0.2-0.5%.

[0009] Furthermore, the recycled coarse aggregate is construction waste that has been sorted and crushed into particles with a size of 4.75~31.5mm;

[0010] The recycled fine aggregate is construction waste that has been sorted and crushed into particles with a size of less than 4.75 mm, and the content of particles with a size of less than 0.075 mm is less than 20%.

[0011] Furthermore, the sludge originates from a waterworks or sewage treatment plant; the sludge has a moisture content of 75% or higher.

[0012] Furthermore, the cement is PC42.5 composite silicate cement, with an initial setting time greater than 180 min and a final setting time greater than 360 min and less than 600 min;

[0013] The sodium hydroxide is industrial caustic soda flakes, a white flake substance with a purity of over 99%.

[0014] Furthermore, the quicklime contains more than 80% effective calcium oxide.

[0015] Furthermore, in the zinc ricinoleate, the zinc content is 10-12%, the free acid content is less than 2%, and the content of residue on a sieve larger than 0.075mm is less than 0.5%.

[0016] The present invention also provides a method for preparing a road base material as described above, comprising the steps of:

[0017] S1, the sludge, the sodium hydroxide and a portion of the quicklime are first stirred to obtain a first mixture;

[0018] S2, the remaining quicklime and the first mixture are stirred a second time, and then left to stand to obtain the second mixture;

[0019] S3, the zinc ricinoleate and the second mixture are stirred for the third time to obtain the third mixture;

[0020] S4, the recycled fine aggregate and the third mixture are stirred for the fourth time to obtain the fourth mixture;

[0021] S5, the coarse aggregate premix containing a portion of the water, the fourth mixture, the cement and the remaining water are mixed for the fifth time to obtain the road base material;

[0022] The method for obtaining the coarse aggregate premix includes: pre-stirring the recycled coarse aggregate and a portion of the water to obtain the coarse aggregate premix.

[0023] Further, the duration of the first stirring is 15-20 seconds; the duration of the second stirring is 20-30 seconds; the duration of the settling is 1.5-3 hours; the duration of the third stirring is 20-30 seconds; the duration of the fourth stirring is 30-40 seconds; the duration of the fifth stirring is 50-60 seconds; and the duration of the pre-stirring is 15-20 seconds.

[0024] Furthermore, a portion of the quicklime accounts for 50-70% of the total quicklime content; a portion of the water accounts for 60-80% of the total water content.

[0025] The present invention also provides an application of any of the road base materials described above in road construction.

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] This invention, based on sludge and construction waste, yields a high-performance road base material. Through specific component combinations and the synergistic effect of quicklime, sodium hydroxide, and zinc ricinoleate, the road base material exhibits a 7-day unconfined strength of 5.3–5.6 MPa, a 7-day splitting tensile strength of 0.44–0.48 MPa, a scour mass loss rate of 0.071–0.082%, and a 90-day drying shrinkage strain of 188.3 × 10⁻⁶ MPa. -6 ~226.9×10 -6 The water stability coefficient is 0.92~0.96, the Pb leaching concentration is 0.01~0.02 mg / L, the Zn leaching concentration is 1.23~2.29 mg / L, and the Cd leaching concentration is 0.02~0.04 mg / L.

[0028] This invention involves mixing sludge with recycled fine aggregate to ensure thorough mixing and reduce sludge adhesion to recycled coarse aggregate, thereby minimizing its impact on the bonding between cement and recycled coarse aggregate. Since the strength of the base course mixture primarily derives from the interlocking effect between recycled coarse aggregates, while recycled fine aggregates mainly function as fillers in the structure, this invention minimizes the impact of sludge on the base course structure. Furthermore, the recycled coarse aggregate content in this invention is greater than 45%, ensuring a robust skeletal structure and higher load-bearing capacity.

[0029] This invention involves mixing quicklime with sludge, which effectively kills bacteria in the sludge and reduces odor emissions. In this invention, after mixing quicklime, sludge, and recycled fine aggregate, the hardening effect of quicklime slaking and dehydration strengthens the mixed particles of sludge and recycled fine aggregate. Furthermore, the addition of sodium hydroxide promotes the reaction between zinc ricinoleate and sludge. Moreover, the incorporation of quicklime and sodium hydroxide effectively increases the alkalinity of the base material system, thereby enhancing the binding effect of the matrix on heavy metals in the sludge, reducing heavy metal leaching pollution to the external environment, and simultaneously stimulating the active components in the recycled aggregate to undergo hydration reactions, generating more cementing materials and increasing the overall strength of the material.

[0030] This invention incorporates zinc ricinoleate into a road base material based on sludge and construction waste. In an alkaline environment, zinc ricinoleate reacts with cement hydration products to form calcium zinc stone, which can fill the pores of recycled aggregate and strengthen the recycled water-stabilized matrix. At the same time, calcium zinc stone has micro-expansion properties, which can counteract the drying shrinkage caused by early water loss in the recycled water-stabilized matrix. Furthermore, zinc ricinoleate can also reduce the odor emission of sludge and inhibit the growth of microorganisms in sludge.

[0031] Traditional sludge treatment methods typically involve resource utilization through processes such as precipitation and incineration, which suffer from high energy consumption, the generation of toxic substances, and excessive costs. The method of this invention treats sludge without requiring separate precipitation and heating, and the resulting recycled products meet national environmental protection requirements. Therefore, this invention can solve the problems of high energy consumption and high environmental risks in sludge treatment. The widespread application of this invention can promote the high-value utilization of urban solid waste such as sludge and construction waste, and obtain higher-performance road base materials based on sludge and construction waste. Simultaneously, this invention effectively alleviates the pressure of raw material shortages in road construction, laying the foundation for the sustainable development of the transportation industry. Furthermore, the main raw materials of this invention are cheaper than natural stone, resulting in better economic benefits; the main raw materials of this invention are sludge and construction waste, which can also reduce carbon emissions during road construction. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0034] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0035] This invention provides a road base material based on sludge and construction waste, the road base material comprising a base component and an admixture component.

[0036] In this invention, the basic components include: 45-55% recycled coarse aggregate, 20-35% recycled fine aggregate, 15-25% sludge, 4-6% cement, and 1-4% water; both the recycled coarse aggregate and the recycled fine aggregate are derived from construction waste; the total proportion of each raw material in the basic components is 100%.

[0037] Further, the basic components include: 45-55% recycled coarse aggregate, 22-23% recycled fine aggregate, 15-25% sludge, 4-6% cement, and 1-3% water. Further, the basic components include: 54-55% recycled coarse aggregate, 22-23% recycled fine aggregate, 15-16% sludge, 4-5% cement, and 2-3% water.

[0038] In this invention, the external admixtures include quicklime, sodium hydroxide, and zinc ricinoleate; the mass percentage of quicklime to sludge is 4-8%, the mass percentage of sodium hydroxide to sludge is 0.1-0.2%, and the mass percentage of zinc ricinoleate to sludge is 0.2-0.5%.

[0039] Further, the quicklime accounts for 5-7% of the mass percentage of the sludge, the sodium hydroxide accounts for 0.1-0.2% of the mass percentage of the sludge, and the zinc ricinoleate accounts for 0.3-0.5% of the mass percentage of the sludge. Further, the quicklime accounts for 5-5.5% of the mass percentage of the sludge, the sodium hydroxide accounts for 0.1-0.15% of the mass percentage of the sludge, and the zinc ricinoleate accounts for 0.3-0.35% of the mass percentage of the sludge.

[0040] In this invention, the recycled coarse aggregate is construction waste that has been separated and sorted, and then crushed into particles with a size of 4.75~31.5mm. In this example, the recycled coarse aggregate used is construction waste that has been processed through a separation and sorting process and then crushed into particles with a size of 4.75~31.5mm; it mainly includes concrete, brick slag, mortar, ceramic shards, tiles, etc., with a content of impurities such as sawdust, iron filings, and plastic less than 0.3%; and it is dried at 105±5℃.

[0041] In this invention, the recycled fine aggregate is construction waste that has been separated and sorted, then crushed into particles with a particle size of less than 4.75 mm, and the content of particles smaller than 0.075 mm is less than 20%. In this example, the recycled fine aggregate used is construction waste that has been separated and sorted, then crushed into particles with a particle size of less than 4.75 mm, and the content of particles smaller than 0.075 mm is less than 20%; it mainly includes fine particles such as concrete, brick slag, mortar, ceramic shards, and tiles, and the content of impurities such as sawdust, iron filings, and plastic is less than 0.3%; and it is dried at 105±5℃.

[0042] In this invention, the sludge originates from a waterworks or wastewater treatment plant; the sludge has a moisture content of 75% or higher, specifically 75-85%; the organic matter content in the dry weight of the sludge is 31-32%; the Pb leaching concentration is 0.5-0.6 mg / L, the Zn leaching concentration is 30-33 mg / L, and the Cd leaching concentration is 0.2-0.3 mg / L. In this example, the sludge used is wastewater treatment plant sludge with a moisture content of 81%; its dry weight contains 31.5% organic matter; and its main heavy metal leaching concentrations are: Pb 0.55 mg / L, Zn 31.3 mg / L, and Cd 0.22 mg / L.

[0043] In the case of this invention, the cement used is PC42.5 composite silicate cement, with an initial setting time greater than 180 min and a final setting time greater than 360 min and less than 600 min.

[0044] In the present invention, the sodium hydroxide used is industrial caustic soda flakes, a white flake substance with a purity of 99% or higher.

[0045] The quicklime of the present invention has an effective calcium oxide content of greater than 80%, more specifically 85-90%, and more specifically 88-90%. In the example of the present invention, the effective calcium oxide content of the quicklime used is 89%.

[0046] In the present invention, the zinc ricinoleate used is a light yellow powder with a zinc content of 10-12%, a free acid content of less than 2%, and a residue content of less than 0.5% on a sieve larger than 0.075mm.

[0047] This invention addresses the challenges of high-value and large-scale utilization of sludge and construction waste, as well as the technical bottlenecks in the co-utilization of sludge and construction waste. It provides a road base material with high mechanical properties, good durability, and is economical and environmentally friendly.

[0048] In this invention, the 7-day unconfined strength of the road base material is 5.3~5.6 MPa, the 7-day splitting tensile strength is 0.44~0.48 MPa, the scour mass loss rate is 0.071~0.082%, and the 90-day drying shrinkage strain is 188.3×10⁻⁶ MPa. -6 ~226.9×10 -6 The water stability coefficient is 0.92~0.96; the Pb leaching concentration is 0.01~0.02 mg / L, the Zn leaching concentration is 1.23~2.29 mg / L, and the Cd leaching concentration is 0.02~0.04 mg / L.

[0049] Furthermore, the 7-day unconfined strength of the road base material is 5.4~5.6 MPa, the 7-day splitting tensile strength is 0.45~0.48 MPa, the scour mass loss rate is 0.071~0.072%, and the 90-day drying shrinkage strain is 188.3×10⁻⁶ MPa. -6 ~190×10 -6 The water stability coefficient is 0.95~0.96; the Pb leaching concentration is 0.01~0.02 mg / L, the Zn leaching concentration is 1.23~1.5 mg / L, and the Cd leaching concentration is 0.02~0.03 mg / L.

[0050] The present invention also provides a method for preparing a road base material as described above, comprising the steps of:

[0051] S1, the sludge, the sodium hydroxide and a portion of the quicklime are first stirred to obtain a first mixture;

[0052] S2, the remaining quicklime and the first mixture are stirred a second time, and then left to stand to obtain the second mixture;

[0053] S3, the zinc ricinoleate and the second mixture are stirred for the third time to obtain the third mixture;

[0054] S4, the recycled fine aggregate and the third mixture are stirred for the fourth time to obtain the fourth mixture;

[0055] S5, the coarse aggregate premix containing a portion of the water, the fourth mixture, the cement, and the remaining water are mixed for the fifth time to obtain the road base material.

[0056] In this invention, the method for obtaining the coarse aggregate premix includes: pre-stirring the recycled coarse aggregate and a portion of the water to obtain the coarse aggregate premix.

[0057] In this invention, the duration of the first stirring is 15-20 seconds; the duration of the second stirring is 20-30 seconds; the duration of the settling is 1.5-3 hours, further 2-3 hours; the duration of the third stirring is 20-30 seconds; the duration of the fourth stirring is 30-40 seconds; the duration of the fifth stirring is 50-60 seconds; and the duration of the pre-stirring is 15-20 seconds.

[0058] In this invention, a portion of the quicklime accounts for 50-70% of the total quicklime content, more specifically 60-70%; and a portion of the water accounts for 60-80% of the total water content, more specifically 65-70%.

[0059] For example, in this invention, the required amounts of sludge, sodium hydroxide, and 50-70% quicklime are first added to a mixing pot and stirred for 15-20 seconds. The remaining quicklime is then added to the mixing pot and stirred for another 20-30 seconds, followed by standing for 1.5-3 hours. Next, the required amounts of zinc ricinoleate are added to the mixing pot and stirred for 20-30 seconds. Then, the required amounts of recycled fine aggregate are added and stirred for another 30-40 seconds. The resulting mixture is then poured out for later use. Next, the required amounts of recycled coarse aggregate and 60-80% water are added to the mixing pot and stirred for 15-20 seconds. Then, the previously obtained mixture, the required amounts of cement, and the remaining water are added to the mixing pot and stirred for another 50-60 seconds, finally yielding the desired road base material. In this invention, the mixing power of the mixing pot is 4-4.2 kW; in this example, the mixing power of the mixing pot is 4.1 kW.

[0060] The method for preparing the road base material in this invention is simple, economical and environmentally friendly, and the resulting product has excellent performance.

[0061] The present invention also provides an application of any of the road base materials described above in road construction.

[0062] The following are specific examples of the present invention:

[0063] The agitator used in the specimen molding process of this invention is the SJD 30 horizontal forced agitator manufactured by Shanghai Xiaoxiao Experimental Instrument Equipment Co., Ltd.

[0064] The sampling, molding, and curing of the test specimens for this invention are conducted in accordance with the relevant provisions of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG 3441-2024).

[0065] The test specimen performance test items of this invention include 7-day unconfined compressive strength, splitting strength, water stability test, 28-day scouring test, drying shrinkage test and heavy metal leaching test of the specimen.

[0066] Test specimens were cured for 6 days under standard curing conditions, then soaked in water for 1 day, and their unconfined compressive strength and splitting tensile strength were tested. The water stability test mainly involved testing the unconfined compressive strength of the specimen after 6 days of standard curing, followed by 1 day of water soaking; the ratio of the measured value to the strength value after 7 days without water soaking was the water stability coefficient. Test specimens were cured for 28 days under standard curing conditions, then soaked in water for 1 day, and then subjected to a scouring test. Test specimens were cured for 7 days under standard curing conditions, and then subjected to a drying shrinkage test. The methods for the unconfined compressive strength, splitting tensile strength, water stability test, and scouring test of the specimens were in accordance with the relevant provisions of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG 3441-2024).

[0067] The heavy metal leaching test involves curing the test specimens under standard conditions for 28 days, then removing them and drying them at room temperature for 2 days. The dried specimens are then crushed, ground finely using a ball mill, and sieved through a square-hole sieve to collect particles with a diameter of 0.125 mm to 0.25 mm as the test sample. The testing procedure for heavy metal leaching of the samples follows the relevant provisions of "Determination of Leachable Heavy Metals in Cement Mortar" (GB / T 30810-2014). The heavy metals tested include Pb, Zn, and Cd.

[0068] Example 1

[0069] This embodiment provides a road base material based on sludge and construction waste. The raw materials of the road base material consist of basic components and admixtures.

[0070] The base components, by mass percentage, are: 55% recycled coarse aggregate, 23% recycled fine aggregate, 15% sludge, 4% cement, and 3% water.

[0071] The external admixtures are: 5% quicklime (based on the sludge mass), 0.1% sodium hydroxide (based on the sludge mass), and 0.3% zinc ricinoleate (based on the sludge mass).

[0072] In this embodiment, the preparation method of the road base material includes the following steps:

[0073] S1. First, put the required amount of sludge, sodium hydroxide, and 2 / 3 of the quicklime into a mixing pot and stir for 15 seconds to obtain the first mixture.

[0074] S2, put the remaining quicklime into the mixing pot and continue to stir for 25 seconds, then let it stand for 2 hours to obtain the second mixture;

[0075] S3, then put the required amount of zinc ricinoleate into the mixing bowl and stir for 25 seconds to obtain the third mixture;

[0076] S4, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the fourth mixture, and then pour out the obtained fourth mixture for later use;

[0077] S5. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained fourth mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0078] Example 2

[0079] This embodiment provides a road base material based on sludge and construction waste. The raw materials of the road base material consist of basic components and admixtures.

[0080] The basic components, by mass percentage, are: 50% recycled coarse aggregate, 22% recycled fine aggregate, 20% sludge, 6% cement, and 2% water.

[0081] The external admixtures are: 6% quicklime (based on the sludge mass), 0.2% sodium hydroxide (based on the sludge mass), and 0.4% zinc ricinoleate (based on the sludge mass).

[0082] In this embodiment, the preparation method of the road base material is the same as that in Example 1.

[0083] Example 3

[0084] This embodiment provides a road base material based on sludge and construction waste. The raw materials of the road base material consist of basic components and admixtures.

[0085] The base components, by mass percentage, are: 45% recycled coarse aggregate, 23% recycled fine aggregate, 25% sludge, 6% cement, and 1% water.

[0086] The external admixtures are: 7% quicklime (relative to the sludge mass), 0.2% sodium hydroxide (relative to the sludge mass), and 0.5% zinc ricinoleate (relative to the sludge mass).

[0087] In this embodiment, the preparation method of the road base material is the same as that in Example 1.

[0088] Comparative Example 1

[0089] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of quicklime is omitted, while other conditions remain the same as in Example 1.

[0090] In this comparative example, the preparation method of the road base material is as follows:

[0091] S1. First, put the required amount of sludge and sodium hydroxide into a mixing pot and stir for 40 seconds, then let it stand for 2 hours to obtain the first mixture.

[0092] S2, then put the required amount of zinc ricinoleate into the mixing bowl and stir for 25 seconds to obtain the second mixture;

[0093] S3, then put the required amount of recycled fine aggregate into the mixing pot and continue mixing for 30 seconds to obtain the third mixture, and then pour out the obtained third mixture for later use;

[0094] S4. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained third mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0095] Comparative Example 2

[0096] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of sodium hydroxide is omitted, while other conditions remain the same as in Example 1.

[0097] In this comparative example, the preparation method of the road base material is as follows:

[0098] S1. First, put the required amount of sludge and 2 / 3 of the quicklime into the mixing pot and stir for 15 seconds to obtain the first mixture.

[0099] S2, put the remaining quicklime into the mixing pot and continue to stir for 25 seconds, then let it stand for 2 hours to obtain the second mixture;

[0100] S3, then put the required amount of zinc ricinoleate into the mixing bowl and stir for 25 seconds to obtain the third mixture;

[0101] S4, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the fourth mixture, and then pour out the obtained fourth mixture for later use;

[0102] S5. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained fourth mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0103] Comparative Example 3

[0104] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of zinc ricinoleate is omitted, while other conditions remain the same as in Example 1.

[0105] In this comparative example, the preparation method of the road base material is as follows:

[0106] S1. First, put the required amount of sludge, sodium hydroxide, and 2 / 3 of the quicklime into a mixing pot and stir for 15 seconds to obtain the first mixture.

[0107] S2, put the remaining quicklime into the mixing pot and continue to stir for 25 seconds, then let it stand for 2 hours to obtain the second mixture;

[0108] S3, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 55 seconds to obtain the third mixture, and then pour out the obtained third mixture for later use;

[0109] S4. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained third mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0110] Comparative Example 4

[0111] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of quicklime and sodium hydroxide is omitted, while other conditions remain the same as in Example 1.

[0112] In this comparative example, the preparation method of the road base material is as follows:

[0113] S1, put the required amount of sludge and zinc ricinoleate into a mixing pot and stir for 25 seconds to obtain the first mixture;

[0114] S2, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the second mixture, and then pour out the obtained second mixture for later use;

[0115] S3, Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained second mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0116] Comparative Example 5

[0117] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of quicklime and zinc ricinoleate is omitted, while other conditions remain the same as in Example 1.

[0118] In this comparative example, the preparation method of the road base material is as follows:

[0119] S1. First, put the required amount of sludge and sodium hydroxide into a mixing pot and stir for 40 seconds, then let it stand for 2 hours to obtain the first mixture.

[0120] S2, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the second mixture. Then pour out the obtained second mixture for later use.

[0121] S3, Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained second mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0122] Comparative Example 6

[0123] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that the addition of sodium hydroxide and zinc ricinoleate is omitted, while other conditions remain the same as in Example 1.

[0124] In this comparative example, the preparation method of the road base material is as follows:

[0125] S1. First, put the required amount of sludge and 2 / 3 of the quicklime into the mixing pot and stir for 15 seconds to obtain the first mixture.

[0126] S2, put the remaining quicklime into the mixing pot and continue to stir for 25 seconds, then let it stand for 2 hours to obtain the second mixture;

[0127] S3, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the third mixture. Then pour out the obtained third mixture for later use.

[0128] S4. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained third mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0129] Comparative Example 7

[0130] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that it omits the external admixtures (does not add quicklime, sodium hydroxide, and zinc ricinoleate), while other conditions remain the same as in Example 1.

[0131] In this comparative example, the preparation method of the road base material is as follows:

[0132] S1. First, put the required amount of sludge and recycled fine aggregate into the mixing pot and stir for 30 seconds to obtain a mixture. Then, pour out the mixture for later use.

[0133] S2, Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0134] Comparative Example 8

[0135] Regarding the raw material composition of the road base material, this comparative example differs from Example 1 only in that zinc ricinoleate is replaced with sodium dimethyl dithiocarbamate (SDD, a commonly used sludge heavy metal chelating agent), while other conditions remain the same as in Example 1.

[0136] In this comparative example, the preparation method of the road base material is as follows:

[0137] S1. First, put the required amount of sludge, sodium hydroxide, and 2 / 3 of the quicklime into a mixing pot and stir for 15 seconds to obtain the first mixture.

[0138] S2, put the remaining quicklime into the mixing pot and continue to stir for 25 seconds, then let it stand for 2 hours to obtain the second mixture;

[0139] S3, then put the required amount of sodium dimethyl dithiocarbamate into the mixing pot and stir for 25 seconds to obtain the third mixture;

[0140] S4, then add the required amount of recycled fine aggregate to the mixing pot and continue mixing for 30 seconds to obtain the fourth mixture, and then pour out the obtained fourth mixture for later use;

[0141] S5. Next, put the required amount of recycled coarse aggregate and 2 / 3 of the water into the mixing pot and stir for 15 seconds. Then, put the previously obtained fourth mixture, the required amount of cement and the remaining water into the mixing pot and continue stirring for 50 seconds to obtain the road base material.

[0142] Comparative Example 9

[0143] The raw material composition of the road base material is the same as that of Example 1.

[0144] In this comparative example, the preparation method of the road base material is as follows: the required amounts of recycled coarse aggregate, recycled fine aggregate, sludge, cement, water, quicklime, sodium hydroxide and zinc ricinoleate are all put into a mixing pot and stirred for 160 seconds to obtain the road base material.

[0145] Analysis example 1

[0146] As shown in Table 1, the strength of Examples 1-3 meets the design requirements of road base courses of various grades, and the water stability performance is excellent. In addition, the leaching concentrations of heavy metals all meet the relevant requirements of the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB16889-2008) (Pb < 0.25 mg / L, Zn < 100 mg / L, Cd < 0.15 mg / L); even more specifically, the leaching concentration of Pb does not exceed 0.02 mg / L, the leaching concentration of Zn does not exceed 2.3 mg / L, and the leaching concentration of Cd does not exceed 0.04 mg / L.

[0147] As can be seen from Example 1 and Comparative Example 1, the absence of quicklime leads to decreased strength, reduced durability, and increased leaching concentration of heavy metals.

[0148] As can be seen from Example 1 and Comparative Example 2, the absence of sodium hydroxide results in lower strength, reduced durability, and increased leaching concentration of heavy metals in the road base material.

[0149] As can be seen from Example 1 and Comparative Example 3, the absence of zinc ricinoleate significantly increases drying shrinkage, thereby increasing the risk of cracking in the road base material.

[0150] As can be seen from Example 1 and Comparative Example 4, the absence of quicklime and sodium hydroxide significantly reduces the strength of the road base material, increases drying shrinkage significantly, and reduces the binding effect on heavy metals significantly.

[0151] As can be seen from Example 1 and Comparative Example 5, the absence of quicklime and zinc ricinoleate significantly reduces the strength of the road base material, increases the drying shrinkage significantly, and reduces the binding effect on heavy metals significantly.

[0152] As can be seen from Example 1 and Comparative Example 6, the absence of sodium hydroxide and zinc ricinoleate significantly reduces the strength of the road base material, increases the drying shrinkage significantly, and reduces the binding effect on heavy metals significantly.

[0153] As shown in Example 1 and Comparative Example 7, the absence of quicklime, sodium hydroxide, and zinc ricinoleate resulted in lower strength, durability, and heavy metal binding capacity of the road base material. The above comparison demonstrates that the incorporation of quicklime, sodium hydroxide, and zinc ricinoleate significantly improves strength, durability, and water stability.

[0154] As can be seen from Example 1 and Comparative Example 8, replacing zinc ricinoleate with sodium dimethyl dithiocarbamate reduces the strength and durability of the road base material, affecting its service life as a base structure.

[0155] As can be seen from Example 1 and Comparative Example 9, using conventional mixing methods reduces the strength and durability of road base materials, and also reduces their binding effect on heavy metals.

[0156]

[0157] The results above show that the road base material based on sludge and construction waste in this invention has good mechanical properties, durability, and water stability, while the leaching concentration of heavy metals meets environmental protection requirements. The main raw materials of this invention are solid waste such as sludge and construction waste, resulting in low cost and saving a significant amount of crushed stone resources for transportation engineering construction. Furthermore, it should be noted that the environmental benefits of applying this invention far outweigh its economic benefits.

[0158] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a road base material based on sludge and construction waste, characterized in that, The road base material is composed of basic components and admixtures; The basic components are: 45-55% recycled coarse aggregate, 20-35% recycled fine aggregate, 15-25% sludge, 4-6% cement, and 1-4% water; both the recycled coarse aggregate and the recycled fine aggregate are derived from construction waste. In the basic components, the total proportion of each raw material is 100%; The external admixtures are quicklime, sodium hydroxide, and zinc ricinoleate; the mass percentage of quicklime to sludge is 4-8%, the mass percentage of sodium hydroxide to sludge is 0.1-0.2%, and the mass percentage of zinc ricinoleate to sludge is 0.2-0.5%. The method for preparing the road base material includes the following steps: S1, the sludge, the sodium hydroxide, and a portion of the quicklime are first stirred to obtain a first mixture; the portion of the quicklime accounts for 50-70% of the total quicklime content; S2, the remaining quicklime and the first mixture are stirred a second time, and then left to stand to obtain the second mixture; S3, the zinc ricinoleate and the second mixture are stirred for the third time to obtain the third mixture; S4, the recycled fine aggregate and the third mixture are stirred for the fourth time to obtain the fourth mixture; S5, the coarse aggregate premix containing a portion of the water, the fourth mixture, the cement and the remaining water are mixed for the fifth time to obtain the road base material; The method for obtaining the coarse aggregate premix includes: pre-stirring the recycled coarse aggregate and a portion of the water to obtain the coarse aggregate premix. The water in question accounts for 60-80% of the total water volume.

2. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The recycled coarse aggregate is construction waste that has been sorted and crushed into particles with a size of 4.75~31.5mm; The recycled fine aggregate is construction waste that has been sorted and crushed into particles with a size of less than 4.75 mm, and the content of particles with a size of less than 0.075 mm is less than 20%.

3. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The sludge originates from a waterworks or sewage treatment plant; the sludge has a moisture content of 75% or higher.

4. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The cement is PC42.5 composite silicate cement, with an initial setting time greater than 180 min and a final setting time greater than 360 min and less than 600 min; The sodium hydroxide is industrial caustic soda flakes, a white flake substance with a purity of over 99%.

5. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The quicklime contains more than 80% effective calcium oxide.

6. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The zinc ricinoleate contains 10-12% zinc, less than 2% free acid, and less than 0.5% residue on a sieve larger than 0.075mm.

7. The method for preparing road base material based on sludge and construction waste according to claim 1, characterized in that, The first stirring time is 15-20 seconds; the second stirring time is 20-30 seconds; the settling time is 1.5-3 hours; the third stirring time is 20-30 seconds; the fourth stirring time is 30-40 seconds; the fifth stirring time is 50-60 seconds; and the pre-stirring time is 15-20 seconds.

8. The application of a road base material prepared by the method for preparing road base material based on sludge and construction waste as described in any one of claims 1-7 in road construction.

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