A low-carbon road base material doped with sewage plant sludge, and a preparation method and use thereof

Abstract

The application discloses a low-carbon road base material doped with waterworks sludge and a preparation method thereof, and takes waterworks sludge, a conditioning agent, an additive, engineering spoil, a soil solidifying agent and the like as raw materials, adjusts the moisture content, gradation and plasticity index of the system by using the additive, adjusts and controls the moisture content and environmental safety of the system by using the conditioning agent, and based on the synergistic effect of multiple solid wastes, Al2O3 and SiO2 in the soil solidifying agent react with Ca(OH)2 to generate C-A-S-H, C-S-H, C-A-H gel and Aft and the like, so that the low-carbon road base material has good compactness, mechanical properties, water stability and environmental safety. Meanwhile, the production cost is reduced, the resource utilization level of the solid wastes such as engineering spoil, waterworks sludge, steel slag powder and industrial by-product gypsum is improved, and the principles of maximizing resource utilization, optimizing performance and optimizing economic cost are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid waste resource utilization, specifically to the technical field of low-carbon road base material mixed with waterworks sludge, and particularly relates to a low-carbon road base material mixed with waterworks sludge prepared from engineering spoil, waterworks sludge, recycled fine aggregate, steel slag powder, industrial by-product gypsum and other solid wastes, and a preparation method and use thereof. BACKGROUND

[0002] The safe resource utilization of waterworks sludge is limited due to its high water content, high organic matter content and large performance difference. Considering the physicochemical properties of waterworks sludge, the application of low-carbon road base material mixed with waterworks sludge to road base not only solves the problems of waterworks sludge storage and land occupation, but also promotes the resource utilization of waterworks sludge, thereby creating significant social, economic and environmental benefits.

[0003] The water content, gradation and plasticity index of waterworks sludge are adjusted by the aid, the water content and environmental safety are regulated by the conditioning agent, and the components of Ca(OH)2, Al2O3 and SiO2 in the soil solidifying agent promote the improvement of the mechanical properties of the low-carbon road base material mixed with waterworks sludge. However, the following problems still need to be considered for the preparation of the low-carbon road base material mixed with waterworks sludge from multiple sources of solid waste: (1) the raw materials and their proportions used in the low-carbon road base material mixed with waterworks sludge; and (2) whether the low-carbon road base material mixed with waterworks sludge can meet the performance requirements of JTG / T F20-2015 “Technical Specifications for Highway Pavement Base Construction”, “Standard for Environmental Safety Testing of Cement-based Recycled Materials” (CECS 397-2015) and other standards.

[0004] In view of the above, there is an urgent need in the industry to develop a low-carbon road base material mixed with waterworks sludge and its preparation method, which can reduce resource consumption and production costs, improve the resource utilization level of engineering spoil, waterworks sludge, recycled fine aggregate, steel slag powder and industrial by-product gypsum and other solid wastes, solve the safety and environmental problems of waterworks sludge and engineering spoil, and have significant social, economic and environmental benefits. SUMMARY

[0005] In view of the above-mentioned defects in the prior art, the main purpose of the present application is to provide a low-carbon road base material mixed with sewage plant sludge, which is made of engineering spoil, sewage plant sludge, recycled fine aggregate, conditioning agent, Portland cement, steel slag powder, industrial by-product gypsum, composite admixture, pH regulator, surfactant, etc., improves the resource utilization level of solid waste such as engineering spoil, sewage plant sludge, recycled fine aggregate, steel slag powder, industrial by-product gypsum, etc., adjusts the water content, gradation and plasticity index of the system by using the additive, adjusts the water content and environmental safety of the system by using the conditioning agent, generates C-A-S-H, C-S-H, C-A-H gel and Aft, etc. by the reaction of Al2O3, SiO2 and Ca(OH)2 in the soil solidifying agent based on the synergistic effect of multi-source solid waste, so that the low-carbon road base material has good compactness, mechanical properties, water stability and environmental safety.

[0006] Another purpose of the present application is to provide a preparation method of the above-mentioned low-carbon road base material mixed with sewage plant sludge, which selects the raw materials and the ratio of the low-carbon road base material mixed with sewage plant sludge to prepare a low-carbon road base material mixed with sewage plant sludge that meets the standard performance requirements of JTG / TF20-2015 "Technical Specifications for Highway Pavement Base Construction", "Standard for Environmental Safety Testing of Cement-based Recycled Materials" (CECS397-2015) and the like, reduces the production cost, promotes the resource utilization of multi-source solid waste, and has significant social, economic and environmental benefits.

[0007] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0008] The first aspect of the present application provides a low-carbon road base material mixed with sewage plant sludge, which comprises the following components in terms of weight percentage: conditioning agent 0.5-4%, sewage plant sludge 2-20%, additive 0.01%-30%, engineering spoil 50%-95%, and soil solidifying agent 5%-15%.

[0009] As a preferred technical solution, the low-carbon road base material mixed with sewage plant sludge comprises the following components in terms of weight percentage: conditioning agent 2 parts, sewage plant sludge 10 parts, additive 10 parts, engineering spoil 70 parts, and soil solidifying agent 8 parts.

[0010] As a preferred technical solution, the low-carbon road base material mixed with sewage plant sludge comprises the following components in terms of weight percentage: conditioning agent 1 part, sewage plant sludge 10 parts, additive 5 parts, engineering spoil 78 parts, and soil solidifying agent 6 parts.

[0011] As a preferred technical scheme, the low-carbon road base material mixed with the waterworks sludge comprises the following components in parts by weight: 1 part of a conditioning agent, 5 parts of the waterworks sludge, 10 parts of an auxiliary agent, 79 parts of construction waste soil, and 5 parts of a soil solidifying agent.

[0012] As a preferred technical scheme, the low-carbon road base material mixed with the waterworks sludge comprises the following components in parts by weight: 2 parts of a conditioning agent, 10 parts of the waterworks sludge, 20 parts of an auxiliary agent, 60 parts of construction waste soil, and 8 parts of a soil solidifying agent.

[0013] As a preferred technical scheme, the low-carbon road base material mixed with the waterworks sludge comprises the following components in parts by weight: 1 part of a conditioning agent, 10 parts of the waterworks sludge, 10 parts of an auxiliary agent, 74 parts of construction waste soil, and 5 parts of a soil solidifying agent.

[0014] The soil solidifying agent comprises the following components in percentage by weight: 15-30% of Portland cement, 15-30% of steel slag powder, 20-30% of industrial by-product gypsum, 30-50% of a composite admixture, 1-5% of a pH regulator, and 0.01-0.8% of a surfactant.

[0015] Preferably, the surfactant is one or more of lignosulfonate, triethanolamine.

[0016] Preferably, the construction waste soil has a natural water content of 15-50%, a plasticity index of 7-25%, and an organic matter content of <5%.

[0017] Preferably, the waterworks sludge has a water content of 40-80%, a pH of 6-8, an organic matter content of <25%, a mercury content of 0.02-0.08 mg / kg, an arsenic content of 10-80 mg / kg, a lead content of 10-120 mg / kg, a copper content of 30-90 mg / kg, and a nickel content of 10-80 mg / kg.

[0018] Preferably, the auxiliary agent is recycled fine aggregate, which is processed from concrete, mortar, stone, bricks, and the like in construction waste, has a particle size of <4.75 mm, a water absorption rate of 6-15%, an apparent density of 2100-2500 kg / m 3 , a stone powder content of 0-1%, and a crushing index of 20-38%.

[0019] Preferably, the conditioning agent is selected from quicklime and / or lime calcium, and has an effective calcium oxide content of >70%.

[0020] Preferably, the steel slag powder has CaO: 35-50%, Fe2O3: 20-35%, SiO2: 5-10%, and f-CaO≤15%.

[0021] Preferably, the industrial by-product gypsum comprises one or more of phosphogypsum, desulfurization gypsum, with a purity of > 80%, a pH of 5-12, and a fineness (80 μm square hole screen residue) of < 5%.

[0022] Preferably, the composite admixture is prepared by compounding, grinding and mixing fly ash, slag powder, limestone powder and activator; wherein, according to the weight percentage, the fly ash is 20-50%, the slag powder is 50-80%, the limestone powder is 0.01-10%, and the activator is 0.01-2%; wherein the activator is selected from CaO, NaOH or gypsum, preferably CaO.

[0023] The second aspect of the present application provides a preparation method of the low-carbon road base material mixed with sewage plant sludge, comprising the following steps:

[0024] (1) Engineering spoil pretreatment: the natural moisture content of the engineering spoil is 15-50%, which needs to be dried and treated to control the moisture content of the engineering spoil to be less than 15%.

[0025] (2) Pretreatment of sewage plant sludge: the sewage plant sludge has a moisture content of 40-80%, a predetermined amount of conditioning agent and auxiliary agent are mixed therein to uniformly control the moisture content and grading, and drying treatment is performed; the moisture content of the mixture A is tested and controlled to be less than 15%.

[0026] (3) Preparation of soil solidifying agent: the weighed silicate cement, steel slag powder, industrial by-product gypsum, composite admixture, pH regulator and surfactant are sequentially added to the mixer in the order of feeding and stirred for 2-3 min to uniformly mix and discharge, thereby obtaining the soil solidifying agent.

[0027] (4) The optimum moisture content and maximum dry density of the low-carbon road base material mixed with sewage plant sludge are determined by the compaction test, and the water addition amount of the low-carbon road base material mixed with sewage plant sludge is calculated according to the optimum moisture content and maximum dry density.

[0028] (5) The pretreated engineering spoil and the mixture A are added to the mixer and stirred for 2-3 min to uniformly mix, water (about 2% of the reserved water according to the predetermined water addition amount) is added and stirred for 2 min to uniformly mix, and then the mixture is sealed and soaked for 12-36 h; within 1 h before the specimen is formed, a predetermined amount of the soil solidifying agent of step (4) and the reserved water of about 2% are added and uniformly mixed to form and demold, thereby obtaining the low-carbon road base material mixed with sewage plant sludge.

[0029] The third aspect of the present application provides the application of the above-mentioned low-carbon road base material mixed with sewage plant sludge in the road base, which can be used in the base material of heavy, medium and light traffic of expressway and first-class highway, and secondary and below secondary highway.

[0030] Compared with the prior art, the present application has the beneficial effects that:

[0031] (1) The present application selects the components of the low-carbon road base material mixed with sewage plant sludge, uses engineering spoil, sewage plant sludge, conditioning agent, additive, portland cement, steel slag powder, industrial by-product gypsum, composite admixture, pH regulator and surfactant, and prepares the low-carbon road base material mixed with sewage plant sludge that meets the performance requirements of JTG / T F20-2015 “Technical Specifications for Highway Pavement Base Construction”, “Standard for Environmental Safety Testing of Cement-based Recycled Materials” (CECS 397-2015) and other standards by formula adjustment, thereby reducing production cost and improving the resource utilization level of solid waste such as engineering spoil, sewage plant sludge, steel slag powder and industrial by-product gypsum.

[0032] (2) The additive adjustment system of the present application adjusts the water content, gradation and plasticity index, and the conditioning agent regulation system regulates the environmental safety, and at the same time, Al2O3 and SiO2 in the soil solidifying agent react with Ca(OH)2 to generate C-A-S-H, C-S-H, C-A-H gel and Aft and other hydration products, thereby improving the mechanical properties of the low-carbon road base material mixed with sewage plant sludge; and through physical wrapping, precipitation, adsorption and ion replacement, heavy metal ions are solidified / stabilized to achieve the principles of maximum resource utilization, optimal performance and optimal economic cost. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the drawings needed in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0034] Figure 1 Performance test chart of the low-carbon road base material mixed with sewage plant sludge prepared in Examples 1 to 5, wherein G1, G3 to G5 are engineering spoil in Shanghai, and G2 is engineering spoil in Shandong. DETAILED DESCRIPTION

[0035] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0036] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0037] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0038] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0039] If a number or other numerical value or parameter is expressed in a range, a preferred range, or a series of upper and lower limits, it is to be understood that all ranges formed by any pair of the upper and lower limits of that range, or the preferred range, are expressly stated to be included, even if the ranges are not separately disclosed. In addition, if a range of values is stated herein, unless otherwise stated, the range is to be construed as including the endpoints and all integers and fractions within the range.

[0040] In this document, numerical values are to be construed in a manner consistent with the description set out in the detailed description section entitled "Understanding Numerical Values." For example, the number 40.0 is to be understood as encompassing the range from 39.50 to 40.49.

[0041] The raw materials used in the following examples include engineered soil, waterworks sludge, conditioning agent, additive, soil solidifying agent (including Portland cement, steel slag powder, industrial by-product gypsum, composite admixture, and surfactant); wherein the natural water content of the engineered soil is 15% to 50%, the plasticity index is 7% to 25%, and the organic matter content is <5%; the waterworks sludge has a water content of 40% to 80%, a pH of 6 to 8, an organic matter content of <25%, a mercury content of 0.02 to 0.08 mg / kg, an arsenic content of 10 to 80 mg / kg, a lead content of 10 to 120 mg / kg, a copper content of 30 to 90 mg / kg, and a nickel content of 10 to 80 mg / kg; the recycled fine aggregate as the additive is processed from construction waste heavy concrete, mortar, stone, bricks, etc., and the recycled aggregate with a particle size of <4.75 mm has a water absorption rate of 6% to 15%, an apparent density of 2100 to 2500 kg / m 3 , a stone powder content of 0 to 1%, and a crushing index of 20% to 38%; the conditioning agent is quicklime, calcium lime, etc., and has an effective calcium oxide content of >70%; the steel slag powder has CaO: 35% to 50%, Fe2O3: 20% to 35%, SiO2: 5% to 10%, and f-CaO≤15%; the industrial by-product gypsum is one or more of phosphorus gypsum and desulfurization gypsum; the composite admixture is ground after compounding fly ash, slag powder, limestone powder, and an activator; and the surfactant is one or more of lignosulfonate and triethanolamine. More specifically, the engineered soil is, for example, Shanghai Pudong New Area foundation pit soil and Shandong Heze foundation pit soil; the waterworks sludge is a waterworks sludge of a waterworks in Shanghai; the recycled fine aggregate is a recycled fine aggregate of demolition waste in Shanghai Yangpu District; the quicklime is an industrial-grade quicklime in Shanghai; the Portland cement is Hailuo P·O 42.5 cement; the industrial by-product gypsum is desulfurization gypsum: Shanghai power plant desulfurization gypsum; phosphorus gypsum: Guizhou phosphorus gypsum; and the composite admixture is self-made in the laboratory and includes the following components: fly ash 30 parts; slag powder 64.8 parts; limestone powder 5 parts; and calcium oxide 0.2 parts. Unless otherwise specified, the reagents and instruments used are commercially available products.

[0042] The low-carbon road base material mixed with the waterworks sludge in the following examples is subjected to performance testing, and the steps are as follows:

[0043] (1) Pretreatment of construction waste soil;

[0044] (2) Pretreatment of waterworks sludge;

[0045] (3) Preparation of raw materials according to the components of the low-carbon road base material mixed with the waterworks sludge;

[0046] (4) Preparation of soil solidifying agent;

[0047] (5) Obtaining the optimum water content and the maximum dry density through compaction test;

[0048] (6) Unconfined compressive strength test according to the test results of the optimum water content and the maximum dry density.

[0049] Example 1

[0050] The low-carbon road base material mixed with the waterworks sludge in this example is prepared by the following method:

[0051] (1) Pretreatment of construction waste soil: the natural water content of the construction waste soil is 25%, and the water content of the construction waste soil is controlled to be less than 15% through air drying treatment.

[0052] (2) Pretreatment of waterworks sludge: the water content of the waterworks sludge is 70%, and the water content, gradation, and air drying treatment of the mixture A are controlled to be less than 15% by adding a conditioning agent and an auxiliary agent, and the water content of the mixture A is tested.

[0053] (3) Preparation of raw materials: the raw materials are weighed according to the components of the low-carbon road base material mixed with the waterworks sludge, and the components of the raw materials are weighed as follows in 1000 parts of the low-carbon road base material mixed with the waterworks sludge:

[0054]

[0055]

[0056] (4) Preparation of soil solidifying agent: the silicate cement, steel slag powder, desulfurization gypsum, composite admixture, and calcium hydroxide weighed in step (3) are sequentially added to the mixer in the order of feeding, and stirred for 2-3 minutes, and then the mixture is uniformly mixed and discharged to obtain the soil solidifying agent.

[0057] (5) Preparation of solidified soil: the soil solidifying agent is added to the mixture of the construction waste soil and the waterworks sludge, and the mixture is uniformly mixed to obtain the low-carbon road base material mixed with the waterworks sludge.

[0058] The optimum water content and the maximum dry density are obtained by the compaction test; the unconfined compressive strength test is carried out according to the test results of the optimum water content and the maximum dry density, and the low-carbon road base material mixed with the sewage sludge, and the heavy metal leaching performance in the embodiment are respectively shown in G1 of Table 1 and Table 1. Figure 1

[0059] Example 2

[0060] The low-carbon road base material mixed with the sewage sludge in the embodiment is prepared by the following method:

[0061] (1) Engineering slag pretreatment: the natural water content of the engineering slag is 15%, and the engineering slag is treated by air-drying to control the water content of the engineering slag to be less than 10%.

[0062] (2) Pretreatment of sewage sludge: the water content of the sewage sludge is 70%, and the sewage sludge needs to be mixed with a conditioning agent and an additive to control the water content and the gradation, and is treated by air-drying to control the water content of the mixed material A to be less than 15%, and the water content of the mixed material A is tested.

[0063] (3) Batch: the raw materials are weighed according to the components of the low-carbon road base material mixed with the sewage sludge, and the components of the raw materials are weighed in the low-carbon road base material mixed with the sewage sludge in the following manner:

[0064]

[0065] (4) Preparation of soil solidifying agent: the silicate cement, steel slag powder, desulfurization gypsum, composite admixture and sodium lignosulfonate in step (3) are sequentially added to the mixer in the order of feeding, and stirred for 2-3 min, and then discharged after being uniformly mixed, to obtain the soil solidifying agent.

[0066] (5) Preparation of solidified soil: the soil solidifying agent is added to the mixed material of the engineering slag and the sewage sludge, and uniformly mixed to obtain the low-carbon road base material mixed with the sewage sludge.

[0067] The optimum water content and the maximum dry density are obtained by the compaction test; the unconfined compressive strength test is carried out according to the test results of the optimum water content and the maximum dry density, and the low-carbon road base material mixed with the sewage sludge, and the heavy metal leaching performance in the embodiment are respectively shown in G2 of Table 1 and Table 1. Figure 1

[0068] Example 3

[0069] The low-carbon road base material mixed with the sewage sludge in the embodiment is prepared by the following method:

[0070] (1) Engineering slag pretreatment: the natural water content of the engineering slag is 25%, and the engineering slag is treated by air-drying to control the water content of the engineering slag to be less than 15%.​​

[0071] (2) Waterworks sludge pretreatment: the water content of the waterworks sludge is 70%, and it is necessary to incorporate a conditioning agent, an auxiliary agent to control the water content, grading, and to carry out a drying treatment, to control the water content of the mixed material A to be less than 15%, and to test the water content of the mixed material A.

[0072] (3) batching: according to the components of the low-carbon road base material incorporating the waterworks sludge, the raw materials are weighed, wherein the components of the raw materials are weighed by weight parts in 1000 parts of the low-carbon road base material incorporating the waterworks sludge:

[0073]

[0074] (4) soil solidification agent preparation: according to the feeding sequence, the silicate cement, steel slag powder, phosphogypsum, composite admixture, and calcium hydroxide weighed in step (3) are fed into a mixer and stirred for 2-3 min, and after mixing uniformly, the material is discharged to obtain the soil solidification agent.

[0075] (5) preparation of solidified soil: the soil solidification agent is added to the construction waste soil and the mixed material incorporating the waterworks sludge, and uniformly mixed to obtain the low-carbon road base material incorporating the waterworks sludge.

[0076] The optimum water content and maximum dry density are obtained by compaction test; according to the test results of the optimum water content and maximum dry density, the unconfined compressive strength test is carried out, and in this embodiment, the low-carbon road base material incorporating the waterworks sludge and the heavy metal leaching performance are respectively shown in Table 1 and Table 1. Figure 1

[0077] Example 4

[0078] The low-carbon road base material incorporating the waterworks sludge of this embodiment is prepared by the following method:

[0079] (1) construction waste soil pretreatment: the natural water content of the construction waste soil is 25%, and a drying treatment is used to control the water content of the construction waste soil to be less than 15%.

[0080] (2) Waterworks sludge pretreatment: the water content of the waterworks sludge is 70%, and it is necessary to incorporate a conditioning agent, an auxiliary agent to control the water content, grading, and to carry out a drying treatment, to control the water content of the mixed material A to be less than 15%, and to test the water content of the mixed material A.

[0081] (3) batching: according to the components of the low-carbon road base material incorporating the waterworks sludge, the raw materials are weighed, wherein the components of the raw materials are weighed by weight parts in 1000 parts of the low-carbon road base material incorporating the waterworks sludge:

[0082]

[0083] ​(4) Soil solidification agent preparation: the silicate cement, steel slag powder, phosphogypsum, composite admixture and sodium lignosulfonate in step (3) are sequentially added to the mixer in the order of feeding and stirred for 2-3 min. After mixing uniformly, the material is discharged to obtain the soil solidification agent.

[0084] (5) Preparation of solidified soil: the soil solidification agent is added to the mixture of construction waste soil and sewage sludge, and uniformly mixed to obtain a low-carbon road base material mixed with sewage sludge.

[0085] The optimum water content and maximum dry density are obtained by compaction test. According to the test results of the optimum water content and maximum dry density, the unconfined compressive strength test is carried out. In this embodiment, the low-carbon road base material mixed with sewage sludge and the heavy metal leaching performance are shown in Table 1 and Table 4, respectively. Figure 1

[0086] Example 5

[0087] The low-carbon road base material mixed with sewage sludge in this embodiment is prepared by the following method:

[0088] (1) Construction waste soil pretreatment: the natural water content of the construction waste soil is 25%, and the water content of the construction waste soil is controlled to be less than 15% by air drying treatment.

[0089] (2) Pretreatment of sewage sludge: the moisture content of the sewage sludge is 70%, and the moisture content, gradation and air drying treatment of the mixture A are controlled by adding a conditioning agent and an additive, and the moisture content of the mixture A is tested.

[0090] (3) Ingredient preparation: the raw materials are weighed according to the components of the low-carbon road base material mixed with sewage sludge, wherein the components of the raw materials are weighed as follows in the low-carbon road base material mixed with 1000 parts of sewage sludge:

[0091]

[0092] (4) Soil solidification agent preparation: the silicate cement, steel slag powder, desulfurization gypsum, composite admixture and sodium lignosulfonate in step (3) are sequentially added to the mixer in the order of feeding and stirred for 2-3 min. After mixing uniformly, the material is discharged to obtain the soil solidification agent.

[0093] (5) Preparation of solidified soil: the soil solidification agent is added to the mixture of construction waste soil and sewage sludge, and uniformly mixed to obtain a low-carbon road base material mixed with sewage sludge.

[0094] ​The optimum moisture content and maximum dry density were obtained through compaction tests. Based on the results of the optimum moisture content and maximum dry density tests, unconfined compressive strength tests were conducted. In this embodiment, the low-carbon road subbase material incorporating water plant sludge and its heavy metal leaching performance are shown in [reference needed]. Figure 1 G5 and Table 1.

[0095] Table 1: Heavy Metal Leaching Toxicity of Low-Carbon Road Subbase Materials Incorporating Water Treatment Plant Sludge

[0096] Sample leach concentration / mg / L Cd Cr Ni Cu Zn As Hg Example 1 <0.01 0.11 0.03 0.12 <0.01 0.008 0.00004 Example 2 <0.01 0.10 <0.02 0.10 <0.01 0.008 0.00003 Example 3 <0.01 0.06 0.02 0.07 <0.01 0.005 0.00002 Example 4 <0.01 0.11 0.03 0.14 <0.01 0.008 0.00004 Example 5 0.01 0.12 0.04 0.15 <0.01 0.009 0.00005 CECS 397-2015 ≤0.1 ≤1.5 - ≤2.0 - ≤0.6 ≤0.02

[0097] (Note: Soil stabilizers reduce costs by 10-40% compared to cement, and CO2 emissions by 50-80%.)

[0098] Depend on Figure 1 It is known that the 7-day unconfined compressive strength of the low-carbon road subbase material mixed with water plant sludge is 2.1–4.1 MPa, which meets the 7-day unconfined compressive strength requirements (2.0–4.0 MPa) for subbase materials of expressways and Class I highways with medium and light traffic, as well as Class II and lower-class highways with heavy traffic. The system's moisture content, gradation, and plasticity index are adjusted using additives, and the environmental safety of the system is controlled by conditioning agents. Simultaneously, soil solidification agents are used to react and generate CASH, CSH, and CAH gels with low Ca-Si ratios (<0.8), providing strength to the low-carbon road subbase material mixed with water plant sludge while reducing the leaching of heavy metal ions.

[0099] Table 1 shows that the toxicity of heavy metal leachate from the low-carbon road subbase material mixed with water treatment plant sludge meets the standard requirements. During the solidification process, a large amount of CSH, CAH, AFt, and other products are generated, and the heavy metal ions are solidified / stabilized through physical encapsulation, precipitation, adsorption, and ion exchange. Especially for the heavy metal arsenic, the Ca generated during the hydration of the low-carbon composite cementitious material... 2+ It will react with free AsO4 in the pore fluid 3- ,HAsO4 2- Calcium and arsenic react to form Ca 2+ With HAsO4 2- It forms the less soluble CaHAsO4, when HAsO4 2- After dissociation, CaHAsO4 and Ca3(AsO4)2 are formed. In addition, As is co-precipitated with or adsorbed onto amorphous CaCO3, thereby achieving long-term stable arsenic fixation with an arsenic fixation rate of up to 99%.

[0100] It can be known from the embodiments 1-5 that the low-carbon road bottom base material mixed with the waterworks sludge is prepared by selecting the components of the engineering slag solidifying agent, using the engineering slag, the waterworks sludge, the conditioning agent, the additive, the portland cement, the steel slag powder, the industrial by-product gypsum, the composite admixture and the surfactant, and adjusting the engineering slag solidifying agent formula, satisfies the standard performance requirements of JTG / T F20-2015 “Technical Specification for Highway Pavement Base Construction”, “Standard for Environmental Safety Testing of Cement-based Recycled Materials” (CECS 397-2015) and the like, reduces the production cost of the low-carbon road bottom base material, and improves the resource utilization level of the engineering slag, the waterworks sludge, the steel slag powder, the industrial by-product gypsum and the like. The cost of the low-carbon road bottom base material mixed with the waterworks sludge is reduced by 30-80% compared with the traditional road bottom base material, and the CO2 emission is reduced by 30%-60% compared with the traditional road bottom base material.

[0101] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A low-carbon road subbase material doped with waterworks sludge, comprising the following components in percentage by weight: conditioner 0.5-4%, waterworks sludge 2-20%, auxiliary agent 0.01%-30%, construction waste soil 50%-95%, and soil solidifying agent 5%-15%; the conditioner is selected from quicklime and / or lime calcium, and the effective calcium oxide content thereof is > 70%; the waterworks sludge has a water content of 40%-80%, a pH of 6-8, an organic matter content of < 25%, a mercury content of 0.02-0.08 mg / kg, an arsenic content of 10-80 mg / kg, a lead content of 10-120 mg / kg, a copper content of 30-90 mg / kg, and a nickel content of 10-80 mg / kg; the construction waste soil has a natural water content of 15%-50% and a plasticity index of 7%-25%, and has an organic matter content of < 5%; and the soil solidifying agent comprises the following components: Portland cement 15%-30%, steel slag powder 15%-30%, industrial by-product gypsum 20%-30%, composite admixture 30%-50%, pH regulator 1-5%, and surfactant 0.01%-0.8%, wherein the composite admixture is obtained by compounding and grinding fly ash, slag powder, limestone powder, and an activator. The low-carbon road subbase material doped with waterworks sludge comprises the following components in parts by weight: conditioner 2 parts, waterworks sludge 10 parts, auxiliary agent 10 parts, construction waste soil 70 parts, and soil solidifying agent 8 parts. Alternatively, the low-carbon road subbase material doped with waterworks sludge comprises the following components in parts by weight: conditioner 1 part, waterworks sludge 10 parts, auxiliary agent 5 parts, construction waste soil 78 parts, and soil solidifying agent 6 parts. The auxiliary agent is recycled fine aggregate, which is recycled aggregate with particle size < 4.75 mm processed from concrete, mortar, stone blocks, bricks and tiles in construction waste, with water absorption of 6% to 15%, apparent density of 2100 to 2500 kg / m 3 , stone powder content of 0 to 1%, and crushing index of 20% to 38%; Alternatively, the low-carbon road subbase material doped with waterworks sludge comprises the following components in parts by weight: conditioner 1 part, waterworks sludge 5 parts, auxiliary agent 10 parts, construction waste soil 79 parts, and soil solidifying agent 5 parts. Alternatively, the low-carbon road subbase material doped with waterworks sludge comprises the following components in parts by weight: conditioner 2 parts, waterworks sludge 10 parts, auxiliary agent 20 parts, construction waste soil 60 parts, and soil solidifying agent 8 parts.

2. The low carbon road base material incorporating water treatment plant sludge according to claim 1, characterised in that, Alternatively, the low-carbon road subbase material doped with waterworks sludge comprises the following components in parts by weight: conditioner 1 part, waterworks sludge 10 parts, auxiliary agent 10 parts, construction waste soil 74 parts, and soil solidifying agent 5 parts. The surfactant in the soil solidifying agent is one or more of lignosulfonate and triethanolamine. The steel slag powder has a CaO content of 35%-50%, a Fe2O3 content of 20%-35%, and a SiO2 content of 5%-10%, and the f-CaO content is ≤ 15%. The industrial by-product gypsum comprises one or more of phosphogypsum and desulfurization gypsum, has a purity of > 80%, a pH of 5-12, and a fineness of < 5% on an 80-μm square-hole sieve. The steel slag powder has a CaO content of 35%-50%, a Fe2O3 content of 20%-35%, and a SiO2 content of 5%-10%, and the f-CaO content is ≤ 15%. The industrial by-product gypsum comprises one or more of phosphogypsum and desulfurization gypsum, has a purity of > 80%, a pH of 5-12, and a fineness of < 5% on an 80-μm square-hole sieve. ​ ​ 3. The low carbon road base material incorporating sewage plant sludge according to claim 1 or 2, characterized in that, ​ 4. The low carbon road base material incorporating sewage plant sludge according to claim 1 or 2, characterized in that, ​ ​ The fly ash is 20-50% by weight percentage, the slag powder is 50-80% by weight percentage, the limestone powder is 0.01-10% by weight percentage, and the activator is 0.01-2% by weight percentage in the composite admixture; wherein the activator is selected from CaO, NaOH or gypsum.

5. The low-carbon road base material incorporating sewage plant sludge according to claim 4, characterized in that, The activator is CaO.

6. The method for preparing a low-carbon road subbase material mixed with sewage plant sludge according to any one of claims 1 to 5, comprising the following steps: (1) Engineering spoil pretreatment: the natural moisture content of the engineering spoil is 15-50%, and the engineering spoil needs to be dried to control the moisture content of the engineering spoil to be less than 15%; (2) Sewage plant sludge pretreatment: the sewage plant sludge has a moisture content of 40-80%, a predetermined amount of conditioning agent and auxiliary agent are mixed into the sewage plant sludge to control the moisture content and grading, and the mixture is dried to obtain a mixture A, and the moisture content of the mixture A is tested and controlled to be less than 15%; (3) Preparation of soil solidifying agent: the weighed silicate cement, steel slag powder, industrial by-product gypsum, composite admixture, pH regulator and surfactant are sequentially added to a mixer in the order of feeding and stirred for 2-3 min to obtain a soil solidifying agent; (4) The optimum moisture content and the maximum dry density of the low-carbon road subbase material mixed with sewage plant sludge are determined by a compaction test, and the water addition amount of the low-carbon road subbase material mixed with sewage plant sludge is calculated according to the optimum moisture content and the maximum dry density; (5) The pretreated engineering spoil and the mixture A are added to the mixer and stirred for 2-3 min, and then water is added, and the water is reserved by 2% of the predetermined water addition amount, and then stirred for 2 min, and then sealed for 12-36 h; within 1 h before the specimen is formed, a predetermined amount of the soil solidifying agent of step (4) and the reserved 2% water are added and uniformly mixed to form a specimen, and then demolded to obtain the low-carbon road subbase material mixed with sewage plant sludge.

7. The application of the low-carbon road subbase material mixed with sewage plant sludge according to any one of claims 1 to 5 in a road subbase, wherein the road subbase is the subbase of expressways and first-class highways, light traffic and heavy, medium and light traffic roads of secondary highways.

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