A highway engineering cement prepared based on lead smelting slag

Abstract

The present application relates to solid waste resource utilization and building material technical field, particularly relates to a kind of highway engineering cement prepared based on lead smelting slag.The raw materials of highway engineering cement prepared based on lead smelting slag include: lead smelting slag 15-35 parts, slag 19-44 parts, cement clinker 25-40 parts and gypsum 4-6 parts by mass fraction.The present application carries out resource utilization to lead smelting slag and slag, improves the hydration activity of metallurgical slag by the synergistic excitation of Portland cement clinker and gypsum, can meet the mechanical strength needs of heavy, medium, light load grade highway surface layer cement;At the same time, the 28d dry shrinkage rate and setting time of the highway engineering cement all meet the industry index requirements.Finally, the utilization rate of lead smelting slag and slag in the present application is high, and the clinker content is small, which not only improves the resource utilization level of industrial solid waste, but also reduces the production cost of highway cement, has good environmental protection and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical fields of solid waste resource utilization and building materials, and particularly relates to a highway engineering cement prepared based on lead smelting slag. BACKGROUND

[0002] Lead smelting slag is a waste slag with certain hydration activity generated in the process of lead smelting by fire method, which can exhibit cementitious activity under the excitation of physical and chemical conditions, and can be used as cement active admixture or concrete admixture. According to statistics, the production of lead smelting slag has exceeded 2.5 million tons in 2022. However, the activity of lead smelting slag is much lower than that of slag, resulting in a low utilization rate, and a large amount of lead smelting slag is landfilled and stored, occupying land resources. In addition, lead smelting slag is rich in heavy metal elements such as manganese, zinc and lead, which can gradually leach into the ecological system under the erosion of the external environment, causing serious harm to environmental safety and residents' health.

[0003] At the same time, with the continuous development of the transportation industry, the proportion of cement concrete pavement is gradually increasing. The current road portland cement suitable for cement concrete pavement and the production cost of portland cement are high, which limits its application. Although the cost of ordinary portland cement is low, it is often difficult to meet the performance requirements of high flexural strength and low shrinkage required by road engineering. SUMMARY

[0004] Based on the above, the present application provides a highway engineering cement prepared based on lead smelting slag, which has excellent mechanical properties, low dry shrinkage and low cost, and at the same time, the utilization status of a large amount of lead smelting slag is relieved, the resource utilization level of non-ferrous metallurgical solid waste is improved, and the ecological protection plays a positive role.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0006] One of the technical solutions of the present application is a highway engineering cement prepared based on lead smelting slag, and the raw materials include, by mass fraction, 15-35 parts of lead smelting slag, 19-44 parts of slag, 25-40 parts of cement clinker and 4-6 parts of gypsum.

[0007] Further, the sum of the fractions of the lead smelting slag, the slag, the cement clinker and the gypsum is 100.

[0008] Further, the raw materials include, by mass fraction, 15-25 parts of lead smelting slag, 39-44 parts of slag, 30-40 parts of cement clinker and 6 parts of gypsum.

[0009] Further, the raw materials include, by mass fraction, 25-35 parts of lead smelting slag, 19-44 parts of slag, 25-40 parts of cement clinker and 6 parts of gypsum.

[0010] Furthermore, the content of the main elements in the lead smelting slag is, by mass percentage, CaO 10.0-12.0%, SiO2 12.0%-26.5%, Al2O3 5.0%-7.0%, Fe2O3 44.0%-46.8%, MgO 3.0%-7.0%, and ZnO ≤ 5.0%; the specific surface area of ​​the lead smelting slag is 350-450m 2 / kg or particle size D 50 It is 16.0~29.0μm.

[0011] The present invention specifically limits the ZnO content to ≤5.0%. This is because the Zn element is a valuable metal component remaining in the smelting process, is easily soluble in the alkaline atmosphere of cement clinker hydration, and slows down the early hydration reaction process, thereby reducing the early strength of the cementitious material.

[0012] The reason for limiting the specific surface area or particle size of lead smelting slag to the above ranges is that lead smelting slag itself has low activity. If the particle size of lead smelting slag is larger than the above range (the specific surface area is lower than the above parameter range), it is difficult to fully exert its secondary hydration effect, which in turn reduces the performance of the cementitious material. Furthermore, lead smelting slag is a difficult-to-grind material, with a grinding work index greater than that of cement clinker, slag, and steel slag. Obtaining lead smelting slag particles with a smaller particle size inevitably increases grinding energy consumption, which is not conducive to its industrial application. Therefore, considering the secondary hydration effect and energy loss, the specific surface area or energy consumption of lead smelting slag is limited to the above ranges.

[0013] Furthermore, the specific surface area of ​​the cement clinker is 300 to 400 m 2 / kg or particle size D 50 The thickness is 18.0~30.0μm, and the 28d compressive strength is ≥50MPa.

[0014] When the fineness of cement clinker is too large (the particle size is too small), the cement hydration speed is too fast, which will lead to a large shrinkage value; and too large fineness will increase the grinding energy consumption; on the other hand, if the fineness of cement clinker is too small (the particle size is too large), the early strength of the cementitious material will be reduced. Therefore, the present invention preferably limits the particle size D of cement clinker to 50 18.0~30.0μm

[0015] Furthermore, the specific surface area of ​​the slag is 400 to 500 m 2 / kg or particle size D 50 The particle size is 8.0-18.0 μm, and the 7-day activity index is ≥95%, and the 28-day activity index is ≥105%.

[0016] The reason for limiting the specific surface area or particle size of the slag to the above range is that if the particle size of the slag is too small, energy consumption will increase, and if the particle size is too large, its secondary hydration effect will be affected. Therefore, the present invention preferably limits the specific surface area or particle size of the slag to the above range.

[0017] Furthermore, the gypsum is desulfurized gypsum, which is dried at 80-110° C. for 22-24 hours before being added as a raw material, and then ground using an SM-500 ball mill at a rotation speed of 45±3 r / min for 20 minutes.

[0018] Furthermore, the raw material further comprises 0 to 0.2 parts of triethanolamine solution by mass, and is not 0. Preferably, it is 0.005 to 0.2 parts, and more preferably, it is 0.1 to 0.2 parts.

[0019] Triethanolamine can promote the hydration of C3A in cement and its reaction with Al 3+ 、Fe 3+ Plasma generates complexes, shortening the latent period of cement hydration and thereby improving early strength. In the present invention, when the amount of triethanolamine solution added is greater than 0.2 parts, the triethanolamine does not exert an early strengthening effect, but instead delays hydration, adversely affecting early strength. When the amount of triethanolamine solution added is too low, for example, 0.005 parts, there is no significant change in the strength of the cementitious material.

[0020] Furthermore, the solid content of the triethanolamine solution is 7-20%.

[0021] The triethanolamine solution is obtained by diluting a triethanolamine mother liquor with a solid content of ≥70% by 5 to 10 times.

[0022] The second technical solution of the present invention is the use of the above-mentioned highway engineering cement prepared based on lead smelting slag in the preparation of heavy, medium and light load grade highway surface layers.

[0023] Furthermore, when the highway engineering cement prepared based on lead smelting slag is used for heavy-load grade highway pavement, the raw materials include, by mass: 15 to 25 parts of lead smelting slag, 39 to 44 parts of slag, 30 to 40 parts of cement clinker and 6 parts of gypsum.

[0024] Furthermore, when the highway engineering cement prepared based on lead smelting slag is used for medium and light load grade highway pavement, the raw materials include, by mass: 25 to 35 parts of lead smelting slag, 19 to 44 parts of slag, 25 to 40 parts of cement clinker and 6 parts of gypsum.

[0025] The present invention discloses the following technical effects:

[0026] The present invention provides a highway engineering cement prepared based on lead smelting slag, which improves the hydration activity of lead smelting slag and slag through the synergistic excitation of cement clinker and gypsum. - Gradually dissolve the surface of metallurgical waste slag particles, releasing active Al2O3 and active SiO2 therein. The active silicon-aluminum components react with the calcium hydroxide produced by clinker hydration to produce hydrated calcium silicate, hydrated calcium aluminate, ettringite and other products, forming gel strength.

[0027] The present invention prepares highway engineering cement with excellent mechanical properties, small drying size and low cost through the rational compounding of raw materials. This alleviates the current situation of large-scale storage and landfill of lead smelting slag, improves the resource utilization level of non-ferrous metallurgical solid waste, and plays a positive role in ecological protection.

[0028] The lead smelting slag and slag in the present invention have high utilization rates and low clinker content, which not only improves the resource utilization level of industrial solid waste, but also reduces the production cost of highway cement, and has good environmental protection and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 The XRD diffraction patterns of the highway engineering cement prepared in Example 1 and Comparative Example 2 at 3d and 28d hydration are shown;

[0031] Figure 2 This is the MIP diagram of the highway engineering cement prepared in Example 1 and Comparative Example 2 after hydration for 28 days. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The "parts" mentioned in the present invention are based on mass parts unless otherwise specified.

[0038] The lead smelting slag used in the examples and comparative examples of the present invention is the smelting waste slag produced by quenching the high-temperature melt in the pyrometallurgical lead smelting process. The main chemical components and contents thereof are: CaO 10.25%, SiO2 26.26%, Al2O3 6.51%, Fe2O3 44.55%, ZnO 1.07%, MgO 3.42%. It is obtained by grinding in an SM-500 ball mill, and the particle size is D 50 It is 28.3μm.

[0039] The composition of the cement clinker used in the examples of the present invention and the comparative examples is: CaO 67.20%, SiO2 18.40%, Al2O3 4.29%, Fe2O3 3.93%, ZnO 0.07%, MgO 3.88%. It was obtained by grinding in an SM-500 ball mill, with a particle size of D 50 The 28d compressive strength is 52.2MPa.

[0040] The particle size D of the slag used in the examples of the present invention and the comparative examples is 50 The particle size is 9.9μm and the slag activity grade is S105.

[0041] Example 1

[0042] (1) Weigh 15 parts of lead smelting slag, 39 parts of slag, 40 parts of cement clinker, and 6 parts of desulfurization gypsum by weight; dry the desulfurization gypsum at 105°C for 24h, and then place it in a SM-500 ball mill to grind for 20min at a speed of 48r / min to obtain desulfurization gypsum powder; mix the accurately weighed lead smelting slag, slag, cement clinker, and desulfurization gypsum powder for 3min to obtain heavy-load grade highway surface layer cement (powder).

[0043] (2) Add the mixed powder into a cement mortar stirring pot, and prepare cement mortar test blocks according to the molding standard of “GB / T 17671-2021 Cement Mortar Strength Test Method (ISO Method)”, and demold after 1d of curing in a curing room with a temperature of 20±1°C and a relative humidity of ≥90%, and continue to cure until the specified age to measure the 3d and 28d flexural and compressive strengths; measure the setting time according to “GB / T 1346-2011 Cement Standard Consistency Water Content, Setting Time, and Stability Test Method”; and measure the 28d drying shrinkage according to “JC / T 603-2004 Cement Mortar Drying Shrinkage Test Method”.

[0044] Examples 2-3 and Comparative Examples 1-3

[0045] The preparation processes of Examples 2-3 and Comparative Examples 1-3 are consistent with Example 1, except that the proportions of the raw materials are different, wherein Example 2 is used for medium-load grade highway surface layer, and Example 3 is used for light-load grade highway surface layer, as shown in Table 1.

[0046] Table 1

[0047]

[0048]

[0049] The 3d and 28d mechanical properties of Examples 1-3 and Comparative Examples 1-3 are detected, and the test results are shown in Table 2.

[0050] Table 2

[0051]

[0052] According to “JTG / T F30-2014 Technical Details for Construction of Highway Cement Concrete Pavement”, the required mechanical strength limit requirements of heavy, medium, and light traffic load grade highway surface layer cement are summarized. The results are shown in Table 3.

[0053] Table 3

[0054]

[0055] From Table 2, Table 3, it can be seen that Example 1, Example 2, Example 3 meet the mechanical strength requirements of heavy, medium and light load grade highway surface layer cement respectively; Comparative Example 1 meets the mechanical strength requirements of medium grade highway surface layer cement (close to the heavy grade highway index), Comparative Example 2 meets the mechanical performance requirements of light grade highway surface layer cement (close to the medium grade highway index), and Comparative Example 3 meets the performance requirements of light grade highway surface layer cement (the cement clinker and lead smelting slag contents are reduced by 15% and 10% respectively compared with Example 3). From Table 1, Table 2, it can be seen that, under the fixed clinker content, the strength of the cementitious material decreases with the increase of the lead smelting slag content. When the lead smelting slag content is ≤35%, the mechanical strength of the prepared cementitious material meets the performance requirements of heavy, medium and light load grade highway surface layer cement. Under the synergistic activation of cement clinker and desulfurization gypsum, the metallurgical slag system composed of lead smelting slag and slag can undergo secondary hydration and further produce cementing strength. Overall, the introduction of lead smelting slag reduces the system strength, but when the content is reasonably controlled, this loss in strength is still acceptable. Further, this moderate reduction in strength can be exchanged for the effective use of lead smelting slag, so from the perspective of environmental protection and resource conservation, this highway engineering cement prepared based on lead smelting slag has practical application significance.

[0056] The setting time and drying shrinkage performance of Examples 1-3 were detected, and the test results are shown in Table 4.

[0057] Table 4

[0058]

[0059] According to the “JTG / T F30-2014 Technical Specifications for Construction of Highway Cement Concrete Pavement”, the setting time and drying shrinkage rate limit requirements of heavy, medium and light traffic load grade highway surface layer cement are summarized. The results are shown in Table 5.

[0060] Table 5

[0061]

[0062] From Table 4, Table 5, it can be seen that Examples 1-3 all meet the setting time and 28d drying shrinkage rate limit requirements of heavy, medium and light load grade highway surface layer cement. The initial setting time of the cementitious material in Examples 1-3 is about 3.3h, the final setting time is about 4.2h, and it shows the characteristics of short initial and final setting interval. The maximum value of the 28d drying shrinkage rate of Examples 1-3 is 0.053% of Example 2, and the minimum value is 0.021% of Example 1, which are all less than the standard required 28d drying shrinkage rate limit.

[0063] Example 4

[0064] Example 4 is based on the addition of triethanolamine to improve the mechanical strength of cementitious materials, and finally meet the mechanical strength requirements of medium load highway pavement cement. The specific preparation steps are as follows:

[0065] (1) A certain mass of triethanolamine mother liquor (solid content 70%) was weighed, diluted 10 times with deionized water and shaken well for use. According to the weight, 35 parts of lead smelting slag, 24 parts of slag, 35 parts of cement clinker and 6 parts of desulfurization gypsum were weighed; The desulfurization gypsum was dried at 105℃ for 24h, and then placed in a SM-500 type ball mill at a speed of 48r / min for 20min to obtain desulfurization gypsum powder; The accurately weighed lead smelting slag, slag, cement clinker and desulfurization gypsum powder were mixed for 3min to obtain a mixed powder, which was used.

[0066] (2) According to the weight, 0.1 parts of diluted triethanolamine solution and 50 parts of tap water were weighed, respectively. First, the triethanolamine solution was added to the cement mortar stirring pot, then the container containing the triethanolamine solution was washed several times with the weighed tap water, and the washed solution was added to the stirring pot. Then, the mixed powder in step (1) was added, and the standard cement mortar test block was formed according to the “GB / T 17671-2021 Cement Mortar Strength Test Method (ISO Method)”. After demolding in a curing room with a temperature of 20±1℃ and a relative humidity of ≥90% for 1d, continue to cure until the specified age to measure the 3d and 28d flexural and compressive strength.

[0067] The mechanical property detection results of example 4 and comparative example 2 are shown in table 6.

[0068] Table 6

[0069]

[0070] As shown in Table 6, the addition of triethanolamine in Example 4 can meet the mechanical strength limit requirements of medium load grade highway pavement cement. After adding a certain mass of triethanolamine, the flexural and compressive strength of the cementitious material is improved to a certain extent, that is, an appropriate amount of triethanolamine is beneficial to improve the mechanical strength of the cementitious material.

[0071] Further analyze the reason why the highway engineering cement prepared based on lead smelting slag produces cementing strength from the microstructure.

[0072] X-ray diffractometer, MIP mercury intrusion porosimeter and SEM scanning electron microscope were used to analyze the hydration products, pore size distribution and microstructure of example 1 and comparative example 2, in order to explain the hydration mechanism of the cementitious material in the present application.

[0073] (1) XRD analysis of cementitious material hydration products

[0074] Figure 1The XRD diffraction patterns of the cementitious materials in Example 1 and Comparative Example 2 after curing for 3 days and 28 days are shown in FIG. Figure 1 As can be seen, the hydration products of highway engineering cement prepared from lead smelting slag are primarily mineral phases such as ettringite, portlandite, and calcite. The amorphous diffraction peaks between 25° and 40° represent the lead smelting slag, the glass within the slag, and the amorphous gel formed by hydration. The intensity of the portlandite diffraction peak changes significantly with increasing curing time. After 28 days of hydration, the intensity of the portlandite diffraction peak decreases significantly in Example 1 (L15-C40), indicating secondary hydration of the metallurgical slag system within the cementitious material. Compared to the 3-day hydration period, the diffraction pattern of Example 1 (L15-C40) shows a significant decrease in the intensity of the characteristic diffraction peak near 42°, representing magnesia or magnetite. This indicates that the mineral phases within the lead smelting slag participate in the hydration reaction, stimulated by the cement clinker and desulfurized gypsum. The intensity of the characteristic diffraction peaks of C3S and β-C2S decreases with increasing curing age, indicating continued hydration of the cement clinker. Compared with hydration for 3 days, the characteristic diffraction peak intensity of ettringite in Example 1 (L15-C40) is reduced to a certain extent. This may be due to the high cement clinker content in this example. After 28 days of curing, a large amount of CSH gel is generated, which occupies the pores in the hardened block, thereby affecting the crystallization and growth of ettringite.

[0075] (2) MIP analysis of hydration products of cementitious materials

[0076] The pore size distribution of the cementitious materials after curing for 28 days in Example 1 and Comparative Example 2 is as follows: Figure 2 The cumulative pore volume is shown in Table 7. The pores in cement and concrete can be divided into four categories according to their pore size: gel pores (<10nm), transition pores (10-100nm), capillary pores (100-1000nm), and macropores (>1000nm).

[0077] Table 7

[0078]

[0079] Depend on Figure 2 As can be seen from Table 7, the porosity of the cementitious materials in Example 1 and Comparative Example 2 increases after 28 days of hydration, and the most probable pore size of the hardened slurry gradually increases. Table 7 also clearly shows that with increasing lead smelting slag content and decreasing clinker content, the porosity of the cementitious materials increases from 21.8% to 27.4% after 28 days of hydration. Higher porosity reduces the mechanical properties of the hardened specimens, which is consistent with the mechanical property test results in Table 2.

[0080] In summary, it can be seen that the present invention, through the synergistic stimulation of cement clinker and desulfurized gypsum, successfully prepared heavy, medium, and light-load grade highway surface cement with setting time, shrinkage rate, and mechanical properties that meet industry standards at different lead smelting slag dosages (15% to 35%). The prepared standard cement mortar test blocks have a 28-day flexural strength of ≥10 MPa and a 28-day compressive strength of ≥49 MPa, which can be used for the construction needs of heavy, medium, and light-load grade roads and has good ecological and economic benefits. In addition, triethanolamine can further improve the mechanical strength of this highway engineering cement prepared based on lead smelting slag, thereby achieving higher environmental and economic benefits.

[0081] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A highway engineering cement prepared based on lead smelting slag, characterized in that: Calculated by weight, the raw materials include: 15 to 35 parts of lead smelting slag, 19 to 44 parts of slag, 25 to 40 parts of cement clinker and 4 to 6 parts of gypsum, and 0 to 0.2 parts of triethanolamine solution, which is not 0; The sum of the mass fractions of the lead smelting slag, slag, cement clinker and gypsum is 100; The specific surface area of ​​the lead smelting slag is 350 to 450 m 2 / kg or particle size D50 is 16.0 to 29.0 μm; The specific surface area of ​​the cement clinker is 300 to 400 m 2 / kg or particle size D50 is 18.0~30.0μm, 28d compressive strength ≥50MPa; The specific surface area of ​​the slag is 400 to 500 m 2 / kg or particle size D50 is 8.0-18.0 μm, and the 7-day activity index is ≥95%, and the 28-day activity index is ≥105%; The gypsum is desulfurized gypsum, which is dried at 80-110° C. for 22-24 hours before being added as a raw material, and then ground in a ball mill for 20 minutes.

2. The highway engineering cement prepared based on lead smelting slag according to claim 1, characterized in that: Calculated by mass, the raw materials include: 15 to 25 parts of lead smelting slag, 39 to 44 parts of slag, 30 to 40 parts of cement clinker and 6 parts of gypsum.

3. The highway engineering cement prepared based on lead smelting slag according to claim 1, characterized in that: Calculated by mass, the raw materials include: 25 to 35 parts of lead smelting slag, 19 to 44 parts of slag, 25 to 40 parts of cement clinker and 6 parts of gypsum.

4. The highway engineering cement prepared based on lead smelting slag according to claim 1, characterized in that: The solid content of the triethanolamine solution is 7-20%.

5. Use of the highway engineering cement prepared based on lead smelting slag as claimed in any one of claims 1 to 4 in the preparation of heavy, medium and light load grade highway pavements.

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