Pavement base material, preparation method and application

Abstract

The invention discloses a pavement base material, a preparation method and application, and relates to the technical field of building materials, the pavement base material comprises sludge and a curing agent; the mixing amount of the curing agent is 5-15% of the mass of the sludge; the curing agent comprises slag, charcoal and carbide slag; wherein the slag accounts for 45%-75% of the total mass of the curing agent, the charcoal accounts for 5%-35% of the total mass of the curing agent, and the carbide slag accounts for 20%-50% of the total mass of the curing agent. According to the invention, the curing agent with a specific ratio is adopted, and the sludge is cured by using the alkaline excitation effect of the carbide slag in the curing agent, the gelling effect of the slag and the multifunctional synergistic effect of the charcoal, so that the cured and stabilized sludge material has excellent compressive strength, splitting strength and durability; therefore, the cured sludge material can be used as a pavement base material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a pavement base material, a preparation method and application. BACKGROUND

[0002] Due to the characteristics of high water content, low strength and low cost, silt is usually used for roadbed filling in the research on road engineering regeneration application, but not used as pavement base material. The main reason is that the pavement base has strict requirements on the strength, crack resistance and water stability of the material, and the silt cannot meet the application requirements of low-grade pavement base material.

[0003] Therefore, cement and / or lime are usually used as solidifying agents for silt in the prior art. However, the silt solidified by cement and / or lime still does not have excellent compressive strength, splitting strength and durability, and cannot effectively inhibit the water loss and volume shrinkage of silt, resulting in the phenomenon of dry shrinkage cracks on the pavement. SUMMARY

[0004] The main purpose of the present application is to provide a pavement base material, a preparation method and application, which aims to solve the technical problem of poor compressive strength, splitting strength and durability of silt material in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides a pavement base material, which comprises silt and a solidifying agent; the mixing amount of the solidifying agent is 5% to 15% of the mass of the silt.

[0006] The solidifying agent comprises slag, biochar and carbide slag; wherein the slag accounts for 45% to 75% of the total mass of the solidifying agent, the biochar accounts for 5% to 35% of the total mass of the solidifying agent, and the carbide slag accounts for 20% to 50% of the total mass of the solidifying agent.

[0007] In an embodiment, the mixing amount of the solidifying agent is 5%, 10% or 15% of the mass of the silt; and / or

[0008] The mass ratio of the slag, the biochar and the carbide slag in the solidifying agent is 51.38%:16.66%:31.96%.

[0009] In an embodiment, the mixing amount of the solidifying agent is 15% of the mass of the silt; and

[0010] The mass ratio of the slag, the biochar and the carbide slag in the solidifying agent is 51.38%:16.66%:31.96%.

[0011] In an embodiment, the biochar comprises one or more of plant type agricultural straw, forestry waste, municipal sludge and livestock and poultry solid waste.

[0012] In an embodiment, the particle size of the biochar is 1-30 microns; the density of the biochar is 0.48 g / cm 3 , the specific surface area is 45.88 m 2 / g, the pH is 9.13, and the ash content is 7.43%.

[0013] In addition, to achieve the above object, the application further provides a preparation method of a road base material.

[0014] The curing agent and the silt are mixed and stirred according to a target water content to obtain a mixture.

[0015] The mixture is pressed and formed.

[0016] In an embodiment, before the curing agent and the silt are mixed and stirred according to a target water content to obtain a mixture, the preparation method further comprises:

[0017] The silt is dried and dampened.

[0018] In an embodiment, the drying and dampening of the silt comprises:

[0019] The silt is dried in an environment of 60 DEG C for 120 min and then dampened with water for 24 h for standby.

[0020] In addition, to achieve the above object, the application further provides an application of a road base material, which is applied to a low-grade road base.

[0021] In an embodiment, the compressive strength of the road base material is 3.56-5.97 MPa, and the splitting strength is 0.37-0.62 MPa.

[0022] After the road base material is applied for 7 days, the water loss rate is stabilized at 14%, and the dry shrinkage is stabilized at 1 mm.

[0023] The one or more technical solutions provided by the application have at least the following technical effects:

[0024] The technical scheme of the present application realizes solidification of silt by using the alkaline activation of the carbide slag, the gelation of the slag and the multifunctional synergistic effect of the biochar in the curing agent with a specific ratio, so that the solidified silt material has better compressive strength, splitting strength and durability, so that the solidified silt material can be used as a road base material. In addition, since the curing agent contains biochar, the excellent water retention of the biochar can effectively inhibit the water loss of the road base material. At the same time, the biochar itself has a fiber-like structure and can form a network bonding system in the soil to improve the integrity and deformation resistance of the soil structure. The excellent water retention and the fiber-like structure of the biochar together effectively inhibit water loss and freeze-thaw damage, thereby effectively inhibiting the generation and expansion of dry shrinkage cracks, so that the road base material has good dry shrinkage performance and durability.

[0025] Further, the present application provides a road base material with excellent road performance by a simple pressing molding preparation method. The preparation method has simple preparation process, easy operation and low raw material cost, so that the road base material can be widely applied to road base.

[0026] Further, since the road base material provided by the present application has excellent compressive strength, splitting strength and durability, it can be applied to the road base of secondary and below secondary roads, and thus fully meets the use requirements of low-grade road base materials. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0028] Figure 1 It is a flowchart of the preparation method of the road base material of the present application;

[0029] Figure 2 It is a particle size distribution curve of the biochar used in the present application;

[0030] Figure 3 It is a particle size distribution curve of the slag and carbide slag used in the present application;

[0031] Figure 4 It is an XRD diffraction pattern of the solidified silt of examples 1-3 and comparative example 4 at 7d curing age;

[0032] Figure 5 It is an XRD diffraction pattern of the solidified silt of examples 1-3 and comparative example 4 at 28d curing age;

[0033] Figure 6 Infrared spectrum of example 1 to 3 and comparative example 4;

[0034] Figure 7 Influence of different curing agent contents on the unconfined compressive strength of the material;

[0035] Figure 8 Influence of different curing agents on the tensile splitting strength of the pavement base material;

[0036] Figure 9 Analysis of the water loss and drying shrinkage characteristics of the examples and comparative examples;

[0037] Figure 10 Mass loss rate of the examples and comparative examples;

[0038] Figure 11 Unconfined compressive strength change rule of the examples and comparative examples after freeze-thaw cycles.

[0039] The purposes, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0041] It should be noted that if the present application involves directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between the components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0042] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, if "and / or" or "and / or" appears throughout the text, it means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection required by the present application.

[0043] In the present application, the numerical interval (i.e. the numerical range) is involved, and if no special instructions are given, the distribution of the selected values in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e. the minimum value and the maximum value) of the numerical interval, and each value between the two numerical endpoints. If no special instructions are given, when the numerical interval only points to the integer in the numerical interval, the two endpoint integers of the numerical range and each integer between the two endpoints are equivalent to directly listing each integer. When multiple numerical ranges are provided to describe the characteristics or properties, the numerical ranges can be combined. In other words, unless otherwise indicated, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows the percentage interval, the ratio interval, the ratio interval, etc. to be included in the quantitative interval.

[0044] The present application provides a pavement base material, which comprises silt and a solidifying agent; the content of the solidifying agent is 5% to 15% of the mass of the silt.

[0045] The solidifying agent comprises slag, biochar and carbide slag; wherein the slag accounts for 45% to 75% of the total mass of the solidifying agent, the biochar accounts for 5% to 35% of the total mass of the solidifying agent, and the carbide slag accounts for 20% to 50% of the total mass of the solidifying agent.

[0046] It should be noted that the silt used in the present embodiment belongs to low liquid limit clay. Specifically, the liquid limit of the silt is less than 50%.

[0047] Additionally, it should be noted that the biochar used in the present embodiment is a product of biomass pyrolysis conversion; the slag used provides the silico-alumina precursor material required for the solidification reaction of sludge solidification, and the carbide slag reacts to generate Ca(OH)2 when it comes into contact with water, providing alkaline reaction conditions for the solidification process.

[0048] It can be understood that, since the present application uses a specific ratio of solidifying agent, and utilizes the alkaline activation of carbide slag, the gelation of slag and the multifunctional synergy of biochar to solidify the sludge, the solidified sludge material has better compressive strength, splitting strength and durability, so that the solidified sludge material can be used as a road base material. In addition, since the solidifying agent contains biochar, its excellent water retention can effectively inhibit the water loss of the road base material. At the same time, biochar itself has a fiber-like structure and can form a network-like interlocking system in the soil to improve the integrity and deformation resistance of the soil structure. The excellent water retention and fiber-like structure of biochar can effectively inhibit water loss and freeze-thaw damage, thereby effectively inhibiting the generation and expansion of dry shrinkage cracks, and the road base material has good dry shrinkage performance and durability. In addition, the solidifying agent used in the present application is a solid waste, and thus the road base material obtained by the present application has the characteristics of low cost and green environmental protection.

[0049] Specifically, the carbide slag releases OH - to provide a strong alkaline environment, in which the glass structure of the slag is dissolved and releases active silicate, thereby activating the slag activity, promoting ion exchange and migration, accelerating the hydration of the slag to generate C-S-H gel, and promoting the strength development of the road base material.

[0050] The slag is used to hydrate to generate C-S-H gel, and further the gel reacts with CO2 to generate CaCO3 and amorphous SiO2, which fills the pores of the material and strengthens its microstructure.

[0051] The biochar is used for multifunctional synergy to solidify the sludge: by adjusting the water supply through high specific surface area and pore structure, reducing fluidity, reducing evaporation and microcracks, thereby effectively inhibiting water loss and freeze-thaw damage, and effectively inhibiting the generation and expansion of dry shrinkage cracks; the surface functional groups of biochar and Ca 2+ complexation promotes C-S-H nucleation to improve the strength of C-S-H gel, and further the C-S-H gel generates CaCO3 and amorphous SiO2 to fill the pores to improve the density and deformation resistance, and finally forms a dense microstructure, improving the solidification effect.

[0052] Further, the particle size of the slag is 5-20 μm; the particle size of the carbide slag is 1-100 μm.

[0053] In an embodiment, the mixing amount of the solidifying agent is 5%, 10% or 15% of the mass of the silt; and / or

[0054] The mass ratio of the slag, the biochar and the carbide slag in the solidifying agent is 51.38%:16.66%:31.96%.

[0055] In an embodiment, the mixing amount of the solidifying agent is 15% of the mass of the silt; and

[0056] The mass ratio of the slag, the biochar and the carbide slag in the solidifying agent is 51.38%:16.66%:31.96%.

[0057] In an embodiment, the biochar comprises one or more of plant type agricultural straw, forestry waste, municipal sludge and livestock and poultry solid waste.

[0058] In the embodiment, the biochar is selected as one of the components of the solidifying agent. On the one hand, the source of the biochar is extensive, and the biochar is present in plant type agricultural waste, forestry waste, municipal sludge and livestock and poultry solid waste. On the other hand, the biochar is environmentally friendly and has the characteristics of sustainability.

[0059] In an embodiment, the particle size of the biochar is 1 μm-30 μm; the density of the biochar is 0.48 g / cm 3 , the specific surface area is 45.88 m 2 / g, the pH is 9.13, and the ash content is 7.43%.

[0060] In addition, in order to achieve the above-mentioned purposes, with reference to Figure 1 , Figure 1 the flowchart of the preparation method of the road surface base material, the application further provides a preparation method of a road surface base material. The preparation method comprises steps S200-S300.

[0061] In step S200, the solidifying agent and the silt are mixed and stirred by adding water according to the target water content to obtain a mixture.

[0062] In step S300, the mixture is compression molded.

[0063] It should be noted that the stirring time can be 15 min.

[0064] In the embodiment, the target water content is not specifically limited and can be adjusted according to actual application. The compression molding method, the compression molding pressure and the compression molding temperature are not specifically limited. For example, the compression molding method can be static pressure method.

[0065] The pavement base material with excellent road performance is prepared by a simple press forming method.

[0066] In an embodiment, before the mixing and stirring of the curing agent and the silt with water according to the target water content to obtain the mixture, the preparation method further comprises:

[0067] In step S100, the silt is dried and dampened.

[0068] In an embodiment, the drying and dampening of the silt comprises:

[0069] The silt is dried in an environment of 60℃ for 120 minutes, and then water is added for dampening for 24 hours.

[0070] It should be noted that the silt needs to be dried and dampened before the mixing of the raw materials, so as to control the liquid limit and plastic limit of the silt within a certain range. For example, after the drying and dampening of the silt, the liquid limit of the silt is 35.6%, and the plastic limit is 22.7%.

[0071] In an embodiment, after the press forming of the mixture, the prepared pavement base material is cured in step S400.

[0072] Specifically, after the press forming of the mixture, the specimen is wrapped and sealed with a preservative film after demolding, and then placed in a standard curing box for curing. The curing temperature is set to 20℃±2℃, and the relative humidity of the curing is ≥95%.

[0073] In addition, to achieve the above-mentioned purpose, the application further provides an application of the pavement base material.

[0074] The pavement base material provided by the application has excellent compressive strength, splitting strength and durability, and can be applied to the pavement base of secondary and below secondary highways, so that the pavement base material fully meets the use requirements of low-grade pavement base materials.

[0075] In an embodiment, the compressive strength of the pavement base material is 3.56MPa-5.97MPa, and the splitting strength is 0.37MPa-0.62MPa.

[0076] After the pavement base material is applied for 7 days, the water loss rate is stable at 14%, and the dry shrinkage is stable at 1mm.

[0077] In the embodiment, when the content of the curing agent is 5%, the unconfined compressive strength of the pavement base material reaches 3.56 MPa, and the tensile splitting strength reaches 0.37 MPa; when the content of the curing agent is 15%, the 28d unconfined compressive strength of the pavement base material reaches 5.97 MPa, and the tensile splitting strength reaches 0.62 MPa, which meet the strength requirements of the pavement base of the secondary and below highways and meet the engineering applicability.

[0078] The technical features in the technical solutions provided by the application will be further clearly and completely described in combination with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product manual is adopted. If the manufacturer of the reagent or instrument is not indicated, the reagent or instrument is a conventional product that can be obtained in the market.

[0079] The silt used in all the following embodiments is from a river of a construction site in Henan. The silt from the river of the construction site in Henan is dried and treated by steaming. The physical properties of the silt after the treatment are tested, and the test results are shown in Table 1. As shown in Table 1, the silt used in the embodiment belongs to low liquid limit clay.

[0080] Table 1 Main physical property parameters of silt

[0081] Soil sample name Natural moisture content (%) Liquid limit (%) Plastic limit (%) Plasticity index Maximum dry density (g / cm 3 )]]> Organic matter content (%) pH Silt 54.6 35.6 22.7 10.3 1.82 3.7 6.5

[0082] The particle size distribution curve of the biochar used in all the following embodiments is shown in Figure 2 , and the basic properties of the biochar are shown in Table 2.

[0083] Table 2 Basic properties of biochar

[0084] Index Density (g / cm 3 )]]> Specific surface area (m 2 / g) pH Ash content (%) Observed value 0.48 45.88 9.13 7.43

[0085] The slag and carbide slag used in all the following embodiments are provided by a certain environmental protection technology limited company in Henan. The particle size distribution curves of the slag and carbide slag are shown in Figure 3 ; the main chemical components and contents of the slag and carbide slag are shown in Table 3.

[0086] Table 3 Main chemical components and contents of slag and carbide slag

[0087] CaO SiO2 Al2O3 MgO Fe2O3 SO3 Na2O K2O Slag 34.8 35.2 17.40 5.88 1.61 1.35 0.64 0.46 Carbide slag 69.13 1.33 1.85 0.44 0.37 0.29 0.05 /

[0088] Embodiment one

[0089] A certain mass of silt is placed in an oven at 60℃ and dried for 120 min, then soaked for 24 h with water for standby; a curing agent and the silt are weighed and mixed with water and stirred for 15 min to obtain a mixture; wherein the mixing amount of the curing agent is 5%, and the mass ratio of slag, biochar and carbide slag in the curing agent is 51.38%:16.66%:31.96% (marked as BAS5% in the test result graph); the stirred mixture is added to a test piece mold, and a test sample is prepared by using a static pressure method; after the test sample is formed, it is demolded, then wrapped and sealed with a preservative film after demolding, and placed in a standard curing box for curing, the curing temperature is set to 20℃±2℃, and the relative humidity of the curing is ≥95%.

[0090] Example Two

[0091] The difference between this example and Example One is only that the mixing amount of the curing agent is 10% (marked as BAS10% in the test result graph).

[0092] Example Three

[0093] The difference between this example and Example One is only that the mixing amount of the curing agent is 15% (marked as BAS15% in the test result graph).

[0094] Example Four

[0095] The difference between this example and Example One is only that the mass ratio of slag, biochar and carbide slag in the curing agent is 45%:5%:50%.

[0096] Example Five

[0097] The difference between this example and Example One is only that the mass ratio of slag, biochar and carbide slag in the curing agent is 75%:5%:20%.

[0098] Example Six

[0099] The difference between this example and Example One is only that the mass ratio of slag, biochar and carbide slag in the curing agent is 45%:35%:20%.

[0100] Example Four

[0101] The difference between this example and Example One is only that the mass ratio of slag, biochar and carbide slag in the curing agent is 51.38%:16.66%:31.96%.

[0102] Comparative Example One

[0103] This comparative example is a prior art, and the only difference between this comparative example and Example Three is that the curing agent is different, and the curing agent only includes lime (marked as OL in the test result graph).

[0104] Comparative Example Two

[0105] This comparative example is prior art. The difference between this comparative example and Comparative Example 1 is that the solidifying agent only includes Portland cement (marked as OPC 15% in the test result graph).

[0106] The chemical composition of the Portland cement and lime and the content of each chemical component are shown in Table 4 below.

[0107] Table 4 is the chemical composition of the Portland cement and lime and the content of each chemical component

[0108] Chemical composition CaO SiO2 Al2O3 Fe2O3 MgO SO3 Silicate cement / % 51.42 24.99 8.26 4.03 3.71 2.52 Lime / % 87.3 0.09 0.13 0.05 2.35 0.11

[0109] Comparative Example 3

[0110] This comparative example is prior art. The difference between this comparative example and Comparative Example 3 is that the amount of Portland cement is different, which is 10% (marked as OPC 10% in the test result graph).

[0111] Comparative Example 4

[0112] The difference between this comparative example and Example 3 is that no solidifying agent is added (marked as SILT in the test result graph).

[0113] In order to analyze the mechanism of the solidifying and stabilizing effect of the solidifying agent BAS on silt, micro tests were performed on Examples 1 to 3 and Comparative Example 4. The crystal structure and functional group structure of the BAS solidified and stabilized silt material were tested by using a D8 ADVANCE X-ray diffractometer (XRD) and a Thermo scientific Nicolet Is 50 Fourier transform infrared spectrometer (FTIR) respectively. The test results are shown in Figure 4 、 Figure 5 and Figure 6 Figure 4 is the XRD diffraction pattern of the solidified silt of Examples 1 to 3 and Comparative Example 4 at a curing age of 7d; Figure 5 is the XRD diffraction pattern of the solidified silt of Examples 1 to 3 and Comparative Example 4 at a curing age of 28d; Figure 6 is the infrared spectrum of Examples 1 to 3 and Comparative Example 4. The XRD test scanning angle 2θ° is set to 5°-75°, and the FTIR test scanning interval is set to 400cm -1 -4000cm -1 .

[0114] From Figure 4 ​It can be seen that with the increase of BAS stabilizer content, the intensity of quartz diffraction peak of stabilized silt material gradually decreases, indicating that SiO2 consumption increases and hydration reaction intensifies in the curing process; in addition, for the hydration silicate diffraction peak (27.5°), its intensity increases with the increase of BAS content, indicating that the increase of the generated cementitious products in the reaction process makes the pore filling effect of silt soil body enhanced, the main reason of which is that calcium carbide slag produces OH- when it meets water, which destroys the Si-O and Al-O bonds in the slag glass body, and the silicate and aluminate ions combine with Ca 2+ Combined with the generation of hydration calcium silicate and other products, the void structure of silt is filled. Under the same content, the decrease range of the quartz diffraction absorption peak of cement stabilized silt material is smaller than that of BAS stabilized silt, indicating that in the process of cement stabilized silt, SiO2 is consumed less in the early stage; and the intensity of the hydration silicate diffraction absorption peak is higher than that of BAS stabilized silt, indicating that the early hydration reaction of cement is faster, and the cementitious products are combined more closely with soil particles.

[0115] From Figure 5 It can be seen that the XRD pattern of the stabilized silt material at 28d curing age shows that the crystal composition of the stabilized silt material is similar to that at 7d age, but the diffraction peak intensity changes significantly. Specifically, with the increase of BAS content, the intensity of the quartz diffraction peak is further reduced than that at 7d, indicating that SiO2 is more fully consumed in the reaction process; in addition, the intensity of the hydration silicate diffraction absorption peak is significantly higher than that at 7d age, and is higher than that of cement stabilized silt material under the same content, indicating that the hydration reaction of BAS system is more sufficient under long-term curing, the cementitious products are rich, and the soil pores are fully filled, the density and strength are improved. For cement stabilized silt, the intensity of the quartz diffraction peak tends to be stable, and the decrease range is smaller than that of BAS system, reflecting that the consumption of SiO2 by cement is weakened in the later stage; the intensity of the hydration silicate diffraction peak increases compared with that at 7d, but is lower than that of BAS stabilized silt under the same content, indicating that the hydration rate of the cement system slows down in the later stage. In summary, with the increase of curing age, the hydration silicate in the BAS stabilized silt material increases, the pore filling is more dense, and the particle connection is more close, so the mechanical strength of the BAS stabilized silt material is stronger with the extension of the age.

[0116] From Figure 6 It can be seen that for the original silt (SILT), the FTIR spectrum shows strong and wide O-H vibration peaks at 3420cm -1 and 1624cm -1 , indicating that the original silt is rich in adsorbed water and free water. With the increase of BAS content, the O-H absorption peak intensity of the stabilized silt material is significantly weakened and narrowed, and the 3640cm -1No obvious Ca(OH)₂ peak was observed, indicating that the BAS curing agent fixes water through the CSH gel generated by slag hydration and participates in the pozzolanic reaction to form a CSH / CASH gel. In contrast, the OPC curing agent can also reduce the intensity of the OH absorption peak, but at a dosage of 15%, the FTIR spectrum of the OPC-stabilized sludge material is at 3640 cm⁻¹. -1 The presence of a distinct Ca(OH)₂ characteristic peak at the location indicates that OPC primarily solidifies the sludge through cement hydration, accompanied by a significant carbonization process. Furthermore, the two types of curing agents have different effects on the degree of polymerization of silicon-oxygen bonds and organic matter. Figure 6 (a) 1006cm -1 At the location, BAS significantly improves the order and polymerization degree of the silicon-oxygen network, and the calcium carbonate peak is weak, indicating that the volcanic ash reaction is dominant and the degree of carbonization is low. Figure 6 (b) 1360cm -1 At the position, although the OPC system also shifts the Si-O-Si peak to higher frequencies, the increase is relatively small. The calcium carbonate absorption peak intensity is significant under high OPC dosage, mainly due to the carbonation process of the hydration product Ca(OH)2. The strongly alkaline environment of OPC leads to a greater decrease in peak intensity, indicating a stronger decomposition effect on organic matter, while the effect of BAS is relatively stable. In summary, the clear differences in FTIR characteristic peaks characterize that the solidification process of sludge by BAS in this application is mainly based on pozzolanic reaction, while that of OPC is mainly based on hydration-carbonation reaction.

[0117] This application also includes the following performance tests on the embodiments and comparative examples:

[0118] (1) Macroscopic mechanical property testing

[0119] Referring to the "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering", the unconfined compressive strength and splitting tensile strength of pavement base materials with different curing agent dosages were tested. Simultaneously, solidified and stabilized silt base materials with single-component cement (OPC) and single-component lime (OL) were used as control groups, and undisturbed silt (SILT) was also used as a control group. The curing ages for the unconfined compressive strength test were set at 3 days, 7 days, 14 days, and 28 days; the curing ages for the splitting tensile strength test were set at 7 days, 14 days, and 28 days.

[0120] Unconfined compressive strength refers to the ultimate strength of a material against axial compression without lateral restraint, and it is an important indicator for evaluating the mechanical strength of inorganic stable materials. The test results of the unconfined compressive strength of the pavement base material in this embodiment are as follows: Figure 7 As shown, Figure 7 A comparative graph showing the effect of different curing agent dosages on the unconfined compressive strength of the material.

[0121] From Figure 7 It can be seen that with the increase of the content of the curing agent, the unconfined compressive strength value of the pavement base material gradually increases, and the 7-day unconfined compressive strength of the pavement base material is ≥3.5 MPa. Specifically, the unconfined compressive strength of the pavement base material under the contents of 5%, 10%, and 15% is 3.56 MPa, 3.72 MPa, and 4.4 MPa, respectively, all of which meet the specification requirements, indicating that the pavement base material prepared in this embodiment can be used as a pavement base material for secondary and below secondary highways and fully has the potential to be applied to low-grade pavement bases.

[0122] In addition, for the silt material stabilized by single-doped lime (OL), the unconfined compressive strength value obviously does not meet the specification requirements, and for the silt material stabilized by single-doped cement (OPC), the 7d unconfined compressive strength value is also obviously higher than 3.5 MPa, but with the extension of the curing age, the unconfined compressive strength value is lower than that of the pavement base materials prepared in Examples One to Three; for example, at the age of 28d, the unconfined compressive strength of the pavement base material of Example Two is 2% higher than that of Comparative Example Three with the same content of single-doped cement (OPC), and the unconfined compressive strength of the pavement base material of Example Three (15% content) is 6% higher than that of Comparative Example Two with the same content of single-doped cement (OPC).

[0123] Thus, it is shown that compared with traditional cement materials, the pavement base material provided in this embodiment has a significant performance advantage.

[0124] The indirect tensile strength, also known as the splitting strength, is an important index for evaluating the anti-cracking performance of inorganic binder stabilized base materials and is a key evaluation standard for measuring whether the internal stress of the base material causes cracking. The test results of the splitting tensile strength of the pavement base material are shown in Table 2. Figure 8 Figure 8 is a comparison chart of the effects of different curing agents on the splitting tensile strength of the pavement base material.

[0125] From Figure 8 It can be seen that the change rule of the splitting tensile strength is consistent with that of the unconfined compressive strength, and the splitting tensile strength value of the pavement base material gradually increases with the increase of the content of the curing agent. At the contents of 5% and 15%, the 7d splitting tensile strength of the pavement base material is 0.19 MPa and 0.37 MPa, respectively; the 14d splitting tensile strength is 0.25 MPa and 0.53 MPa, respectively; and the 28d splitting tensile strength is 0.27 MPa and 0.62 MPa, respectively, all of which meet the specification requirements, indicating that the BAS stabilized silt material prepared in this embodiment has the potential to be applied to low-grade pavement bases. It can be seen that the splitting tensile strength of all the comparative examples at the content of 15% is obviously weaker than that of all the examples, thus indicating that the content of 15% of the curing agent can significantly improve the performance of the pavement base material. ​

[0126] In addition, it should be noted that the splitting tensile strength of the pavement base materials of the first to third embodiments of the present example under 7d curing age is less than that of the comparative example under the same conditions, and the splitting tensile strength of the pavement base materials of the first to third embodiments of the present example under 14d and 28d curing age is significantly higher than that of the comparative example, the reason is that the hydration reaction of the curing agent of the present example is slower, the early strength growth effect is less than that of cement, and in the later period, the biochar plays a role in fiber pulling and connecting in the soil, bears part of the tensile stress, and resists the external tensile force together with the hydration products, thereby reducing the cracking of the soil and enhancing the late splitting tensile strength of the silt.

[0127] (2) Durability test

[0128] After the construction of the inorganic binder stabilized granular base is completed, the water in the material is continuously lost with the hydration and evaporation of the binder, and the loss of water causes dry shrinkage stress in the material, which is easy to cause the material to shrink and crack, and then produce reflection cracks and damage the pavement structure, so it is necessary to carry out dry shrinkage test on the pavement base material; the frost resistance of inorganic binder stabilized material is an important index affecting the stability of base material, and the frost resistance of solidified silt is evaluated by freeze-thaw test.

[0129] According to "Highway Engineering Inorganic Binder Stabilized Material Test Procedure", dry shrinkage test and freeze-thaw test are carried out on the examples and comparative examples respectively. In the dry shrinkage test, the water loss rate, dry shrinkage amount, dry shrinkage strain and dry shrinkage coefficient of the test piece are calculated according to formula (1) to formula (4):

[0130] Water loss rate: ω i = (m i -m i+1 ) / m p (1)

[0131] Dry shrinkage amount:

[0132] Dry shrinkage strain: ε i = δ i / l (3)

[0133] Dry shrinkage coefficient: α di = ε i / ω i (4);

[0134] In the formula, ω i is the water loss rate of the i th time (%); δ i is the dry shrinkage amount observed for the i th time (mm); ε i is the dry shrinkage strain of the test piece for the i th time (%); α di is the dry shrinkage coefficient of the test piece for the i th time (%); m j is the mass of the i th standard test piece (g); X i，jRi,j is the reading of the jth dial gauge at the ith test (mm); 1 is the length of the standard specimen (mm); m is the mass of the standard specimen after drying (g). p Ri,j is the reading of the jth dial gauge at the ith test (mm); 1 is the length of the standard specimen (mm); m is the mass of the standard specimen after drying (g).

[0135] The test results of the dry shrinkage test are shown in Figure 9 , Figure 9 The figure is a comparison of the water loss and dry shrinkage characteristics of the materials. As can be seen from Figure X , the water loss rate and dry shrinkage of Comparative Example Four are the highest, and the addition of the solidifying agent (biomass, slag and carbide slag) to Comparative Example Four can significantly improve the water loss characteristics and dry shrinkage performance of the silt. Although the pavement base material presents a large water loss rate and dry shrinkage change in the first 7 days, the change rate significantly slows down after 7 days, and eventually tends to be stable, indicating that the solidifying agent can effectively inhibit the water loss and volume shrinkage of the silt, and the improvement effect is most significant in the early stage.

[0136] In addition, the dry shrinkage strain of the test samples of Example Three, Comparative Example One and Comparative Example Two all presents the stage characteristics of "rapid growth within 7 days and tends to be stable in the later stage". However, by comparing the water loss rate, dry shrinkage and dry shrinkage strain, it is found that the indicators of Example Three are all better than those of Comparative Example One and Comparative Example Two, indicating that the solidifying agent (biomass, slag and carbide slag) proposed in the present application has the best solidification effect on the silt. The reason mainly lies in that the solidifying agent contains biomass, which effectively inhibits water loss due to its excellent water retention performance. At the same time, biomass itself has a fibrous structure, which can form a network bonding system in the soil body, improve the integrity and anti-deformation ability of the soil body structure, and inhibit the generation and expansion of dry shrinkage cracks. Both of them inhibit the development of dry shrinkage deformation, and thus it is indicated that the pavement base material of Example Three has good dry shrinkage performance.

[0137] In the freeze-thaw test, the test specimen is standard cured for 28 days, and then subjected to 1-5 freeze-thaw cycles, each cycle including 16 hours of freezing at -18℃ and 8 hours of thawing in water at 20℃. The anti-freezing performance is evaluated by the mass change rate and the loss rate of the unconfined compressive strength. The data is read once a day from the first day of being placed in the dry shrinkage room, and once every two days after 7 days. The test results of the freeze-thaw test of all examples and comparative examples are shown in Figure 10 and Figure 11 , Figure 10 is the mass loss rate of the material (wherein AS is Comparative Example Four); Figure 11 is the change law figure of the unconfined compressive strength of the material after freeze-thaw cycle.

[0138] From Figure 10As can be seen, the examples using biochar, slag, and carbide slag as curing agents exhibited significantly lower mass loss rates than comparative examples one to three. This is because the curing agents (biochar, slag, and carbide slag) can fill the pores of the biochar in the sludge during the hydration reaction, forming a denser structure that effectively prevents water intrusion and reduces the degree of soil particle shedding during freeze-thaw cycles, demonstrating excellent freeze-thaw resistance. In contrast, although cement-cured sludge has a dense surface, its internal hydration reaction is insufficient, making it prone to cracks and allowing water to seep in, thus increasing the mass loss rate. Lime-cured sludge also has lower density, and water intrusion causes stronger structural damage, resulting in a higher mass loss rate. Furthermore, increasing the amount of curing agent (biochar, slag, and carbide slag) can significantly improve the freeze-thaw cycle stability of sludge. In Example 2, with a curing agent content of 10%, the mass loss rate increased from 0.72% to 1.06% after 5 freeze-thaw cycles. When the curing agent content (biochar, slag, and carbide slag) was increased to 15%, the increase in the mass loss rate of the material slowed down, rising only from 0.51% to 0.89%.

[0139] from Figure 11 The results for BAS 5%, BAS 10%, and BAS 15% show that the residual compressive strength of the solidified sludge increased to varying degrees with the increase of curing agent dosage. After five freeze-thaw cycles, the unconfined compressive strength of all solidified sludge decreased. After five freeze-thaw cycles, the compressive strength decrease for Examples 1 to 3 at 5%–15% dosage was between 1.67 MPa and 1.81 MPa; the compressive strength decrease for cement (OPC) solidified sludge at 10%–15% dosage was between 1.79 MPa and 1.80 MPa.

[0140] Therefore, it can be seen that the compressive strength of Examples 1 to 3 decreased relatively less, demonstrating that their compressive strength was more stable after freeze-thaw cycles and their resistance to freeze-thaw damage was stronger. Although the unconfined compressive strength of lime (OL) stabilized sludge decreased less after 5 freeze-thaw cycles, its frost resistance index was lower and could not meet the requirements for the stability of base materials.

[0141] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A road base material, characterized in that, The road base material includes silt and a curing agent; the amount of curing agent is 5% to 15% of the mass of the silt. The curing agent comprises slag, biochar, and carbide slag; wherein the slag accounts for 45% to 75% of the total mass of the curing agent, the biochar accounts for 5% to 35% of the total mass of the curing agent, and the carbide slag accounts for 20% to 50% of the total mass of the curing agent.

2. The road base material as described in claim 1, characterized in that, The amount of the solidifying agent is 5%, 10%, or 15% of the mass of the sludge; and / or The mass ratio of the slag, biochar, and carbide slag in the curing agent is 51.38%:16.66%:31.96%.

3. The road base material as described in claim 2, characterized in that, The amount of the solidifying agent is 15% of the mass of the sludge; and The mass ratio of the slag, biochar, and carbide slag in the curing agent is 51.38%:16.66%:31.96%.

4. The road base material as described in claim 1 or 2, characterized in that, The biochar includes one or more of the following: plant-based agricultural straw, forestry waste, municipal sludge, and livestock and poultry solid waste.

5. The road base material as described in claim 4, characterized in that, The biochar has a particle size of 1 μm to 30 μm and a density of 0.48 g / cm³. 3 The specific surface area is 45.88 m². 2 / g, pH 9.13, ash content 7.43%.

6. A method for preparing a road base material according to any one of claims 1-5, characterized in that, The preparation method includes: The curing agent and sludge are mixed with water according to the target moisture content to obtain a mixture; The mixture is pressed into shape.

7. The method for preparing road base material as described in claim 6, characterized in that, Before mixing the curing agent and sludge with water according to the target moisture content to obtain the mixture, the preparation method further includes: The sludge is dried and then subjected to a curing process.

8. The method for preparing road base material as described in claim 7, characterized in that, The drying and curing process of the sludge includes: The sludge was dried in an environment of 60°C for 120 minutes, and then water was added and left to stand for 24 hours before use.

9. An application of the road base material according to any one of claims 1-5, characterized in that, The road base material is used in low-grade road base courses.

10. The application of the road base material as described in claim 9, characterized in that, The compressive strength of the road base material is 3.56 MPa to 5.97 MPa, and the splitting tensile strength is 0.37 MPa to 0.62 MPa. After 7 days of application of the road base material, its water loss rate stabilized at 14% and its shrinkage stabilized at 1 mm.

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