Papermaking white mud mixture for road surface base and construction method thereof

Abstract

The present invention provides a papermaking mud mixture for a pavement base and a construction method thereof. The papermaking mud mixture comprises papermaking mud, crushed stone and a slag-based composite cementitious material; wherein the slag-based composite cementitious material comprises sulfonic slag, fly ash and volcanic ash. The present invention combines papermaking mud, crushed stone and a slag-based composite cementitious material into a papermaking mud mixture. Since the aluminum oxide tetrahedron and silicon oxide tetrahedron in the slag-based composite cementitious material are excited in an alkaline environment and undergo a hydration reaction with the papermaking mud, the hydration reaction will change the internal structure of the mud pavement base material, thereby improving the strength of the pavement base. At the same time, since the sulfonic slag in the slag-based composite cementitious material can provide heat during the hydration reaction, the occurrence of the hydration reaction is promoted, thereby accelerating the change of the internal structure of the mud pavement base material, and ultimately improving the strength of the pavement base.

Description

Technical Field

[0001] The invention relates to a papermaking white mud mixture for a road surface base and a construction method thereof. Background Art

[0002] Black liquor from alkaline pulping is a major source of pollution in the papermaking industry. Traditional alkali recovery technologies eliminate black liquor pollution and recover alkali, but this process also produces large amounts of alkaline waste residue: white mud. A medium-sized pulp mill produces hundreds of tons of white mud daily, causing serious secondary pollution.

[0003] Currently, to address the secondary pollution problem of white mud, a few large pulp mills (such as the Jiamusi, Jilin, and Qingzhou paper mills) use lime kiln calcination to regenerate the white mud and produce recycled lime for recycling in causticizing. However, most pulp and paper mills dispose of white mud by digging pits, landfilling, or stacking. This practice results in the white mud occupying a large amount of land and may cause soil and groundwater pollution. Therefore, there is a need to find more environmentally friendly and effective white mud treatment methods. Summary of the Invention

[0004] The invention aims to solve the problem that papermaking white mud occupies a large amount of land and may pollute soil and groundwater, and provides a papermaking white mud mixture for road surface base and a construction method thereof.

[0005] The technical method of the present invention is as follows:

[0006] A papermaking white mud mixture for a road surface base comprises papermaking white mud, crushed stone and slag-based composite cementitious material; wherein the slag-based composite cementitious material comprises sulfur furnace slag, fly ash and volcanic ash.

[0007] Optionally, the slag-based composite cementitious material sulfur slag comes from waste residue of sulfur refining, the fly ash comes from waste discharged from coal-fired power plants, and the volcanic ash comes from crushed rocks and mineral particles formed by volcanic eruptions.

[0008] Optionally, the mass ratio of papermaking white mud, crushed stone and slag-based composite cementitious material is 35-40:55-58:3-5.

[0009] Optionally, the crushed stones have three particle sizes, including 5-10 mm, 10-20 mm and 20-30 mm, and the mass ratio of the 5-10 mm crushed stones, 10-20 mm crushed stones and 20-30 mm crushed stones is 6-8:40-43:8-10.

[0010] The present invention also provides a construction method for a papermaking white mud mixture for a road surface base, which comprises: performing two-stage mixing, spreading, rolling and curing on the papermaking white mud mixture.

[0011] Optionally, two-stage mixing uses two mixing tanks connected in series.

[0012] Optionally, a crawler-type hydraulic fully automatic paver is used for paving; wherein, a reverse blade is installed in the middle of the spiral distributor of the crawler-type hydraulic fully automatic paver, and a rubber baffle is installed in front of the scraper of the crawler-type hydraulic fully automatic paver.

[0013] Optionally, rolling uses double steel wheels, single steel wheels, or rubber wheels.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention combines papermaking white mud, crushed stone and slag-based composite cementitious materials to form a papermaking white mud mixture. Since the aluminum oxide tetrahedron and silicon oxide tetrahedron in the slag-based composite cementitious material are excited in an alkaline environment, a hydration reaction occurs with the papermaking white mud. The hydration reaction will change the internal structure of the white mud pavement base material, thereby improving the strength of the pavement base. At the same time, the sulfonic slag in the slag-based composite cementitious material can provide heat during the hydration reaction, promoting the occurrence of the hydration reaction, thereby accelerating the change of the internal structure of the white mud pavement base material, and ultimately improving the strength of the pavement base.

[0016] 2. The papermaking white mud of the present invention is waste material from papermaking, the sulfur furnace slag is waste residue from refining sulfur, and the fly ash is waste discharged from coal-fired power plants. The above waste materials, waste residues and waste are applied to the construction of road surface base, realizing the recycling of resources.

[0017] 3. The present invention adopts a new construction method. First, two-stage mixing is used to solve the physical properties of papermaking white mud that it is easy to clump and clump, and the problem that the white mud softens when it comes into contact with water and is difficult to disperse evenly in the mixture. Then, the paver is optimized to solve the problem of high paving coefficient of papermaking white mud base material. Finally, double steel wheels, single steel wheels, and rubber wheels are used to solve the problem that papermaking white mud cannot be effectively bonded, so that papermaking white mud can be used in first-class highways. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the experimental diagram of water addition for papermaking white mud in Example 1;

[0019] Figure 2 This is a graph showing the unconfined compressive strength test of papermaking white mud in Example 2. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] The present invention provides a papermaking mud mixture for road surface base, the papermaking mud mixture comprising papermaking mud, crushed stone and slag-based composite cementitious material, wherein the slag-based composite cementitious material comprises sulfur furnace slag, fly ash and volcanic ash.

[0022] In one embodiment, the main components of papermaking white mud are shown in Table 1.

[0023]

[0024]

[0025] It can be seen that the main component of papermaking white mud is calcium carbonate, with a small amount of sodium silicate, calcium silicate or silicon dioxide, and a very small amount of sulfur, potassium, iron, aluminum, magnesium, and other compounds. These components give it good gelling activity and strength. Therefore, slag-based composite cementitious materials are needed as modifiers in the future to reverse the hydration reaction. The hydration reaction will change the internal structure of the white mud pavement base material and improve the strength of the pavement base.

[0026] In one embodiment, the material has an 80μm mesh pass rate of 98.8%, exhibits low swelling in water, and has an activity coefficient of 27.58%. It is primarily used as an inert filler in road base materials. By combining papermaking mud, crushed stone, and a slag-based composite cementitious material, the slag-based composite cementitious material acts as a modifier to enhance the strength of the papermaking mud, thereby making the road surface smoother and more solid.

[0027] In one embodiment, the slag-based composite cementitious material, sulfur slag, is derived from waste residues from sulfur extraction, fly ash is waste discharged from coal-fired power plants, and volcanic ash is derived from crushed stone and mineral particles formed by volcanic eruptions. The papermaking white mud of the present invention is a waste material from papermaking, the sulfur slag is a waste material from sulfur extraction, and the fly ash is waste discharged from coal-fired power plants. These waste materials, residues, and wastes are used in the construction of road surface base layers, achieving resource recycling.

[0028] In one embodiment, the mass ratio of papermaking mud, crushed stone, and slag-based composite cementitious material is 35-40:55-58:3-5. Preferably, the mass ratio of papermaking mud, crushed stone, and slag-based composite cementitious material is 38:57:5. This ratio is intended to ensure the required strength of the pavement base. If the ratio is lower than this, the pavement base will not meet the standards of a first-class highway. If the ratio is higher than this, the pavement base will meet the standards of a first-class highway, but will result in unnecessary waste.

[0029] In one embodiment, for example, the mass ratio of sulfur slag, fly ash, and pozzolan may be 1-2:1-2:1-2. For example, the ratio may be 1:1:1, 1:1.5:1, 2:2:1.5, 1.5:2:2, etc.

[0030] In one embodiment, the crushed stone has three particle sizes. Specifically, the particle sizes include 5-10 mm, 10-20 mm, and 20-30 mm. Here, the mass ratio of 5-10 mm crushed stone, 10-20 mm crushed stone, and 20-30 mm crushed stone is 6-8:40-43:8-10. Preferably, the mass ratio of 5-10 mm crushed stone, 10-20 mm crushed stone, and 20-30 mm crushed stone is 7:41:9. When paving a road surface, crushed stone of different particle sizes can form a compact structure through gradation design, thereby improving the road surface's load-bearing capacity and stability. For example, 5-10 mm crushed stone can provide better compactness and drainage, while 20-30 mm crushed stone can increase the thickness and strength of the road surface. Furthermore, mixing crushed stone of different particle sizes can create a more uniform mixture, reducing damage to the road surface caused by localized stress concentration. This mixture can better withstand vehicle loads and the effects of the natural environment, extending the service life of the road surface.

[0031] The present invention also provides a construction method of a papermaking white mud mixture for a road surface base, which comprises: performing two-stage mixing, spreading, rolling and curing on the papermaking white mud mixture.

[0032] A1. Two-stage mixing

[0033] In the present invention, due to the physical properties of papermaking white mud that it is easy to form agglomerates and clumps, and the problem that the white mud softens in water and is difficult to disperse evenly in the mixture, a two-stage mixing production process is adopted when mixing the mixture.

[0034] Specifically, the two-stage mixing uses two mixing tanks connected in series, thereby avoiding the problem that one mixing tank cannot mix the papermaking white mud evenly.

[0035] Optionally, the mixing time should be no less than 15 seconds to ensure uniform mixing of the mixture. Preferably, vibration stirring technology is used. It should be noted that any white mud residue that remains after mixing requires re-mixing. If severe sticking to the wall is encountered, the silo wall should be cleaned and struck to remove any adhered white mud mixture.

[0036] In one embodiment, before the two-stage mixing step, the papermaking white mud is dried in a constant temperature drying oven at 45°C ± 2°C for 4 hours. This is because the water content in the papermaking white mud is relatively high, and can reach a water content of up to 40%, so it needs to be dried. At the same time, after drying, the water content of each material on the site should be tested before construction every day to determine the amount of water added on that day. During the mixing production process, the amount of water added should be adjusted in a timely manner according to weather changes and the situation reflected by the foreground paving. For example, when the weather is hot or the transportation distance is long, the water content should be appropriately increased by 0.5-1 percentage points when the mixture is mixed, provided that the technical performance requirements are met.

[0037] In one embodiment, after the mixing step and before the paving step, a transportation step is further included.

[0038] Specifically, the transportation steps include: when the ambient temperature is higher than 30°C, the time from mixing to transportation to on-site paving shall not exceed 2 hours, and if the time exceeds 3 hours, it should be disposed of as waste; when the ambient temperature is lower than 30°C and higher than 15°C, the time from mixing to transportation to on-site paving of the mixture shall not exceed 3 hours, and if the time exceeds 4 hours, it should be disposed of as waste; when the ambient temperature is lower than 15°C, the time from mixing to transportation to on-site paving of the mixture shall not exceed 4 hours, and if the time exceeds 5 hours, it should be disposed of as waste.

[0039] A2. Paving steps:

[0040] Specifically, the papermaking white mud base material has a high paving coefficient and is not good at compacting, so multiple paving is adopted. If only one paving is performed according to the existing technology, the paving coefficient will be higher (reaching 1.5).

[0041] In one embodiment, paving is performed using a crawler-type hydraulic fully automatic paver.

[0042] Specifically, the crawler-type hydraulic fully automatic paver should be equipped with an automatic leveling system and measures to prevent material segregation.

[0043] Specifically, the paver's auger should be equipped with reverse blades in the middle to reduce longitudinal segregation. The auger should also be equipped with a rubber front baffle to reduce vertical segregation during paving.

[0044] Specifically, a rubber baffle is installed in front of the paver scraper (including the widened side plate), and the height of the bottom of the rubber baffle from the top surface of the underlying layer should not be greater than 10 mm.

[0045] Specifically, during the paving process, the paver is equipped with a vibrator and a rammer. The vibration frequency of the vibrator shall not be less than 30Hz, and the impact frequency of the rammer shall not be less than 20Hz, and the stroke shall not be less than 6mm.

[0046] In one embodiment, the paving step includes:

[0047] (1) During the paving process, the speed of the paver should be kept uniform and constant, and the paving speed of the mixture should be controlled at 1.0-3.0m / min.

[0048] (2) When spreading the mixture, it should be kept continuous. If the interruption time exceeds 2 hours due to some reasons, a transverse joint should be set.

[0049] (3) Avoid longitudinal joints during paving. When paving in two sections, the longitudinal joints should be rolled more tightly. If longitudinal joints exist, they should be connected vertically. Slanting is strictly prohibited. When using multiple pavers for paving, the models and degree of wear of the pavers should be the same. During construction, the distance between the front and rear pavers should not exceed 10m, and adjacent construction sections should overlap by 30cm-40cm in the longitudinal direction.

[0050] (4) When the single-operation width of the stable layer is 11-12m, the length of each flow operation section is 300m; when the single-operation width of the stable layer is greater than 12m, the length of the operation section is shortened accordingly.

[0051] (5) A dedicated person should be assigned behind the paver to eliminate aggregate segregation and agglomeration, promptly remove segregated or agglomerated areas, and fill them with good mixed materials.

[0052] (6) For extra-wide road sections that cannot be paved mechanically, manual paving, finishing, and rolling should be used simultaneously.

[0053] (7) Paving residues and mixtures lost on site should be collected and disposed of in a centralized manner and should not be discarded at will.

[0054] Here, when the present invention adopts two-layer continuous paving, if the quality of the lower layer has problems, the upper layer should be processed at the same time. Before the construction of the upper structure, the maintenance materials used in the lower layer should be thoroughly cleaned. After the construction quality of the lower supporting layer is qualified, the upper structure layer can be paved.

[0055] A3. Rolling steps:

[0056] Since the base material of papermaking white mud pavement contains a high content of powder (more than 40%) and only 5% of cementitious materials, it cannot form effective bonding quickly, which may cause looseness; if the strong vibration is started too early, the water-stabilizing material has not yet been dense, which may cause segregation; the aggregate is not completely bonded, which may cause the roller to stick.

[0057] Therefore, the present invention adopts double steel wheels, single steel wheels, and rubber wheels for rolling. The steps of rolling include:

[0058] (1) First, double steel wheels are used for rolling. During the rolling process, the double steel wheels do not vibrate when moving forward and vibrate when moving backward.

[0059] (2) Then, a single steel wheel is used for rolling, during which the single steel wheel is vibrated;

[0060] (3) Then use a rubber wheel to rub and knead countless times, and the rubber wheel is larger than 30t;

[0061] (4) Finally, double steel wheels are used for finishing.

[0062] In one embodiment, the pressing should follow the principle of first the outside and then the inside. The outside rolling should exceed the paving surface by more than 10 cm, the longitudinal direction should be serrated (minimum staggered 0.5m), and the pressing joints should be staggered in a stepped manner in the transverse direction.

[0063] In one embodiment, a dedicated person should be assigned to direct the rolling process to prevent missed rolling and the formation of wheel marks. If soft and springy material occurs, the mixed material in that area should be promptly removed and replaced with a roadbed material with a moisture content that meets the design requirements for rolling. Alternatively, an appropriate amount of coarse aggregate or cement may be added, mixed evenly, and then compacted.

[0064] In one embodiment, during construction in hot summer weather, if the roadbed material becomes loose or shifts during the rolling process, it should be moistened by spraying water mist and stirred evenly to adjust its moisture content to the factory moisture content.

[0065] In one embodiment, side forms are set and secured during rolling. Initial compaction is performed using a small roller and plate compactor near the formwork on both sides of the roadbed, followed by compaction using a double steel-wheel roller and a rubber-wheel roller. Within a 30cm radius of manholes, curbstones, and other structures, where large rollers are difficult to compact, a high-powered plate compactor combined with a small roller can be used.

[0066] A4. Health care steps:

[0067] After the base layer of papermaking white mud pavement is rolled and passes the compaction inspection, it should be covered and cured within 2 hours. The construction unit should select the appropriate curing method based on the actual site conditions of the project. Film covering, impermeable geotextiles, wet sand, asphalt emulsion, or watering with a sprinkler truck can be used.

[0068] For example, watering for health preservation: the number of watering times per day should be determined according to the climate. During construction in high temperature periods, water should be sprinkled twice in the morning and afternoon. During the health preservation period, attention should be paid to keeping the surface of the stable material moist at all times.

[0069] For example, film covering and curing: (1) When the weather is hot and dry, the surface moisture of the papermaking white mud base layer should be observed before covering the film. If necessary, appropriate spraying and watering can be done, but the surface of the stabilization layer should not be eroded. Keep the base layer moist and do not frequently cycle between dry and wet. (2) For areas with large evaporation or projects with a curing time of more than 15 days, appropriate watering should be done during the curing process. (3) The films should be overlapped well to avoid leaks. After covering the film, sand and other materials should be used to form a grid-like cover. When the film is partially damaged, it should be replaced in time. (4) The film can be opened only after curing for 1-2 days before the construction of the upper structural layer.

[0070] For example, geotextile maintenance: (1) Use permeable geotextile to cover the entire section of the stabilizing material layer. Waterproof geotextile can also be laid. (2) During the laying process, pay attention to the overlap between the seams and do not leave any gaps. (3) After laying the geotextile, pay attention to watering. The number of watering times per day should depend on the climate. During high temperature periods, water once in the morning and once in the afternoon.

[0071] In one embodiment, the curing period should be no less than 7 days. During adverse weather conditions, such as when the average daily temperature falls below 10°C or during the rainy season, the curing period should be extended to 14 days. The total curing period should be extended to 2 days before the start of the upper layer formation. Except for sprinkler trucks and small commuter vehicles, no vehicles are allowed to pass during this period, and tracked construction vehicles are strictly prohibited from directly pressing.

[0072] In one embodiment, if cracks appear in the base layer during the curing process and deflection testing indicates that the structural layer's bearing capacity meets the design requirements, the asphalt surface layer can be paved. Alternatively, crack grouting can be employed to address the cracks. For example, crack grouting can be employed; fiberglass grids or single-sided singed polypropylene anti-cracking fabric can be laid at the cracks; or thermally modified asphalt can be applied.

[0073] The present invention is described in detail below by way of examples and experimental examples, which are merely illustrative and do not limit the present invention in any way.

[0074] Example 1 Papermaking white mud water addition experiment

[0075] Papermaking white mud (hereinafter referred to as white mud) was used as the stabilizing material, added to a cement-stabilized gravel mixture at an equal mass to replace fine aggregate. A cement-stabilized gravel mixture with 0% white mud served as a control group, while a cement-stabilized siliceous slag gravel mixture with 38% white mud served as a test group. Compaction tests were conducted using the white mud in the cement-stabilized gravel mixture to determine the optimal moisture content and maximum dry density. The material mix ratios are shown in Table 1.

[0076]

[0077] Table 1 Material ratio scheme for cement-stabilized siliceous slag crushed stone

[0078]

[0079] Table 2 Compaction test data of cement papermaking white mud gravel after modified mix ratio

[0080] Result analysis:

[0081] like Figure 1As shown in Table 1 and Table 2, when the white mud content is 50%, the optimal moisture content of cement-stabilized white mud crushed stone is 7%. When the heavy compaction method is used to determine the maximum dry density, the test result should be multiplied by a correction factor of 1.03 as the standard maximum dry density. Therefore, the maximum dry density after correction is 1.90g / cm 3 According to the compaction test results, the water content of white mud itself is relatively high, so a drying step is required during molding. The compaction test results can provide an effective reference for the amount of water to be added during mixture molding.

[0082] Example 2 Unconfined compressive strength test of papermaking white mud

[0083] For the white mud specimens, two mix ratios were designed. The cementitious materials of the specimens before the mix ratio modification were cement and fly ash, while the cementitious materials after the mix ratio modification were slag-based composite cementitious materials. The dosage of each component is shown in Table 3:

[0084]

[0085]

[0086] Table 3 Material ratio schemes in white mud gravel specimens

[0087]

[0088] Table 4 Unconfined compressive strength data of white mud gravel specimens

[0089] The 7d unconfined compressive strength data of all specimens in Table 4 were averaged and compared with the 7d unconfined compressive strength of cement-stabilized crushed stone specimens. The unconfined compressive strength data of crushed stone specimens with different mix ratios at 7d age were obtained, as shown in Table 5.

[0090]

[0091]

[0092] Table 5 7d unconfined compressive strength test results of white mud specimens and cement stabilized gravel specimens

[0093] Table 5 shows that the 7-day unconfined compressive strength of the modified white mud specimens was 1.5 MPa higher than that of the control cement-stabilized crushed stone specimens. For both white mud specimens, the modified mix significantly improved the 7-day unconfined compressive strength compared to the pre-modified mix. The two mixes differed in several aspects. First, the crushed stone gradations were different; second, the types of cementitious materials differed. The pre-modified mix primarily consisted of cement and fly ash, while the modified mix used a slag-based composite cementitious material; and finally, the ratio of white mud to crushed stone also differed slightly. The compressive strength results show that the 7-day unconfined compressive strength after the modified mix was significantly higher than that before the modification. This indicates that the combination of papermaking white mud and slag-based composite cementitious materials improves specimen strength and that white mud is not suitable for cement stabilization. Therefore, subsequent white mud specimens were formed using the modified mix.

[0094]

[0095] Table 6 Unconfined compressive strength of white mud specimens and cement-stabilized crushed stone specimens at different ages

[0096] Result Analysis

[0097] As shown in Table 6 and Figure 2 As can be seen, during the 7th to 28th day of curing, the compressive strength of the white mud specimens did not increase as significantly as that of the cement-stabilized gravel and siliceous slag specimens, and even showed a downward trend. However, their early strength, especially the 7th day strength, was significantly greater. This is because the combination of white mud and slag-based composite cementitious materials can rapidly activate the cementitious material. Its early hydration reaction is faster than that of cement, and strength development is also faster, resulting in a shorter time for strength development. Papermaking white mud and slag-based composite cementitious materials are also suitable for pavement construction where high early strength requirements are required.

[0098] According to Section 4.2.4 of JTG / T F20-2015 "Technical Specifications for Highway Pavement Base Construction", before the mix ratio was modified, the specimens were prone to falling off during molding, and their 7-day unconfined compressive strength was less than 2 MPa, which did not meet the strength requirements for the pavement base. After the mix ratio was modified, the 7-day unconfined compressive strength was 5.4 MPa-6 MPa, a 3-fold increase in strength, which can meet the requirements of expressways and first-class highways under extremely heavy and extra-heavy traffic conditions. If other performance indicators of the specimens meet the requirements, they can be considered for use in the base of expressways and first-class highways.

[0099] Example 3 Papermaking white mud water stability test

[0100] (1) Water stability under dry-wet cycles

[0101] The water stability test results of the white mud specimens under dry-wet cycles are shown in Table 7.

[0102]

[0103] Table 7 Dry-wet cycle test results

[0104] Result Analysis

[0105] Table 7 shows that the unconfined compressive strength of the white mud gravel specimens after five wet-dry cycles showed little change. The water-stability coefficients at 7 and 28 days were 1.09 and 1.07, respectively, showing no significant difference. The 7-day wet-dry cycle strength of the white mud specimens was greater than that of the standard curing specimens. This is due to the high fines content, large specific surface area, and numerous voids in the white mud, which enhances capillary action under the action of water. Furthermore, during the curing period, the slag-based composite cementitious material undergoes a continuous chemical reaction with the white mud and aggregate, improving the mixture's bonding properties and enhancing its water stability. The softening coefficient is greater than 85%, indicating good water stability.

[0106] (2) Water stability under full immersion

[0107] The water stability test results of the white mud specimens under full immersion are shown in Table 8.

[0108]

[0109] Table 8 Water stability test results under full immersion

[0110] Result Analysis

[0111] As can be seen from Table 8, the water stability coefficients of the white mud specimens under full immersion for 7 days and 28 days are 0.82 and 0.94 respectively, and the softening coefficient is greater than 82%, indicating good water stability.

[0112] Example 4 Frost resistance of papermaking white mud

[0113] The freeze-thaw cycle test results of white mud specimens are shown in Table 9.

[0114]

[0115] Table 9 Freeze-thaw cycle test results

[0116] Result Analysis

[0117] The data in Table 9 show that the two white mud gravel specimens showed significant differences in mass loss after freeze-thaw cycles. This is because specimen 6.25-3 already had some surface damage before freeze-thaw cycles, resulting in a more pronounced mass loss after freeze-thaw cycles. Regarding strength after freeze-thaw cycles, the two white mud specimens experienced strength loss rates of 29.6% and 63.0%, respectively. This indicates that both specimens experienced significant strength loss, particularly specimen 6.25-3. This is because freeze-thaw cycles promote the growth of surface cracks in the white mud gravel specimens, disrupting the bond between the materials and thus compromising the specimen's strength. Finally, the freeze-thaw cycle test results indicate that white mud has poor frost resistance and is unsuitable for use in low-temperature regions.

[0118] Example 5: Anti-scour performance of papermaking white mud

[0119] As precipitation increases, the water stored in the pavement's void structure gradually increases until it reaches saturation. Once water enters the pavement structure, if no vehicles pass through, it falls under the water stability of the pavement material discussed in the previous section, a static state. However, when vehicles pass by, dynamic loads create pore water pressure on the pavement structure, and this water pressure is high enough to scour the base material. Repeated scouring removes some of the base material, and over time, the base material is gradually washed away, forming mud, which eventually penetrates existing cracks in the pavement, causing slurry pumping. Therefore, it is crucial to test base materials for this dynamic water damage.

[0120] The results of the anti-scouring test are shown in Table 10.

[0121]

[0122] Table 10 Anti-scour test results of white mud base specimens

[0123] Result Analysis

[0124] Table 10 shows that when comparing the scour mass loss rates of the two mixtures after 30 minutes, the white mud gravel specimen exhibits a lower scour mass loss rate than the cement-stabilized gravel. This is because white mud, used as the stabilizing material, replaces 0-5 mm fine aggregate. Compared to 0-5 mm fine aggregate, white mud has a greater fineness, making it easier to compact into a denser mass, thus providing better resistance to dynamic water scour. White mud gravel exhibits excellent water stability under dynamic water pressure and is expected to achieve the same scour resistance as traditional cement-stabilized gravel in actual construction.

[0125] Example 6 Papermaking white mud splitting strength

[0126] Splitting strength is the ability to withstand vertical tension in the longitudinal section of a specimen by applying pressure along its diameter until the specimen fails. Therefore, splitting strength is also called indirect tensile strength. Cement-stabilized gravel is a semi-rigid base material. Its splitting resistance primarily stems from the interlocking of the gravel and the bonding effect of cement hydration. When subjected to tension, even the slightest deformation can cause cracking and failure.

[0127] The splitting strength test was carried out on two mixtures of cement stabilized crushed stone and white mud crushed stone. The splitting strength of different mixtures at 28 years old can be obtained through the test. The splitting strength of the two mixtures in the test is shown in Table 11.

[0128]

[0129] Table 11 Splitting strength test results

[0130] Result Analysis

[0131] During the splitting process, it was discovered that the white mud gravel specimen failed as a single crack, rather than splitting in two. This indicates that the specimen underwent particle shear failure, lacking interlocking friction. Due to the powdery structure of white mud, the white mud mixture has a larger specific surface area. This results in a thinner adsorption layer at a consistent cementitious material content. At the same cementitious material content, the cementitious material cannot fully coat the fine aggregate, resulting in insufficient bonding between some fine aggregates and, consequently, low splitting strength.

[0132] When designing actual roads, it is necessary to combine the splitting strength of the siliceous slag pavement base material and adjust the pavement structure design so that the tensile stress at the bottom of the pavement base layer meets the design index requirements.

[0133] Example 6 Papermaking white mud environmental risk assessment experiment

[0134] The comparison of important test indicators of leachate of papermaking white mud pavement base material with current specifications is shown in Table 12:

[0135]

[0136] Table 12 Index data of leachate from papermaking white mud pavement base material

[0137] Note: Groundwater quality standard Class IV - groundwater chemical composition is relatively high, based on the quality requirements of agricultural and industrial water and a certain level of human health risks. It is suitable for agricultural and some industrial water use and can be used as drinking water after proper treatment.

[0138] As can be seen from the table, only a small number of sensory properties and general chemical indicators of the white mud-based pavement base material exceeded the standards, and no toxicological indicators, radioactive indicators, or unconventional indicators exceeded the standards, and the environmental risks are controllable.

[0139] In summary:

[0140] (1) The particle size of the raw material of papermaking white mud is very fine, with a pass rate of 98.8% through an 80μm sieve. It is not easy to swell in water. The activity coefficient is 27.58%. It is mainly used as an inert filler in road base materials.

[0141] (2) (20% moisture content) Papermaking white mud pavement base material: The optimal moisture content is 7%; the 7-day unconfined compressive strength is 5.4MPa-6MPa, which meets all pavement base strength requirements and all subbase strength requirements except for expressways / first-class highways under extremely heavy and extra-heavy traffic; the 28-day water stability coefficient after 5 dry-wet cycles is 107%, and the 28-day water stability coefficient after 5 days of full immersion is 94%, and the water stability is basically the same as that of ordinary water-stabilizing layers; the scour mass loss is 0.03%, and the scour resistance is better than that of ordinary water-stabilizing layers; the residual compressive strength after freeze-thaw is 54%, and it is not recommended for use in low-temperature areas; when designing the pavement, it is necessary to combine the splitting strength of the papermaking white mud pavement base material to verify the tensile stress at the bottom of the pavement base layer.

[0142] (3) (20% moisture content) Only a small amount of sensory properties and general chemical indicators of the papermaking white mud pavement base material exceeded the standards, and no toxicological indicators, radioactive indicators, or unconventional indicators exceeded the standards, and the environmental risks were controllable.

[0143] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A papermaking white mud mixture for road surface base, characterized in that: The papermaking white mud mixture includes papermaking white mud, crushed stone and slag-based composite cementitious material; wherein the slag-based composite cementitious material includes sulfur slag, fly ash and volcanic ash; the sulfur slag of the slag-based composite cementitious material comes from the waste residue of sulfur refining, the fly ash comes from the waste discharged by coal-fired power plants, and the volcanic ash comes from the gravel and mineral particles formed by volcanic eruptions; the mass ratio of the papermaking white mud, crushed stone and slag-based composite cementitious material is 35-40:55-58:3-5.

2. The papermaking white mud mixture according to claim 1, characterized in that The crushed stones have three particle sizes including 5-10 mm, 10-20 mm and 20-30 mm.

3. The papermaking white mud mixture according to claim 2, characterized in that, The mass ratio of the 5-10 mm gravel, 10-20 mm gravel and 20-30 mm gravel is 6-8:40-43:8-10.

4. The construction method of the papermaking white mud mixture for road surface base according to any one of claims 1 to 3, characterized in that: The construction method comprises: performing two-stage mixing, spreading, rolling and curing on the papermaking white mud mixture.

5. The construction method according to claim 4, characterized in that: The two-stage mixing adopts two mixing tanks connected in series.

6. The construction method according to claim 4, characterized in that: The paving is carried out using a crawler-type hydraulic fully automatic paver; wherein, a reverse blade is installed in the middle of the spiral distributor of the crawler-type hydraulic fully automatic paver, and a rubber baffle is installed in front of the scraper of the crawler-type hydraulic fully automatic paver.

7. The construction method according to claim 4, characterized in that: The rolling adopts double steel wheels, single steel wheels and rubber wheels.

Images