Industrial solid waste-based iron tailings road base material and application method thereof

Abstract

The invention discloses an industrial solid waste-based iron tailings road base material and an application method thereof, wherein the mass percentage of each component is: 35-60% iron tailings, 10-20% iron tailings coarse sand, 5-16% cement, 0-7% steel slag, 0-10% slag powder, and 15-25% water. The subbase is firstly sprinkled with water to moisten it, and then the road base material is transported to the top layer of the roadbed and paved, and a large-tonnage double steel wheel roller, a vibrating roller and a rubber wheel roller are used for combined rolling to ensure that the compaction degree reaches more than 98%. The invention can not only consume a large amount of iron tailings, reduce the environmental problems and safety hazards caused by the storage of tailings ponds, but also alleviate the problem of tension and contradiction of traditional road engineering materials, and has better mechanical strength and compressive strength, which meets the standard value of unconfined compressive strength of cement stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015).

Description

Technical Field

[0001] The invention relates to the field of solid waste resource utilization and road engineering construction, and in particular to an iron tailings road surface base material based on industrial solid waste and its application. Background Art

[0002] In recent years, with the rapid development of the economy, the demand for mineral products has increased day by day, and most iron ore resources are of low grade, which determines the output of a large amount of iron tailings. At the beginning of the rise of the mining industry, due to the limitation of technical level, a large amount of iron tailings were usually disposed of by the simplest landfill, which not only occupied land resources and polluted the environment, but also had to pay land acquisition fees, transportation fees and landfill fees, increasing the production cost of the mining economy. Therefore, the disposal and utilization of iron tailings has always been a difficult problem for mining companies and environmental departments.

[0003] In my country, the use of semi-rigid materials for roadbed base is becoming more and more widespread in highway construction. That is, cement, lime, fly ash and other binders are mixed with soil, sand and gravel and other materials and stirred with water as roadbed filling base materials. Since the semi-rigid material base has high strength, rigidity, good water stability, frost resistance and other road advantages, its large-scale use leads to the consumption of a large amount of sand and gravel materials. Excessive exploitation of sand and gravel will cause serious land sandification and soil erosion, collapse and surface cracks, causing environmental pollution, soil erosion, and easily causing disasters such as mudslides and flash floods. Therefore, if iron tailings are used instead of sand and gravel materials in road base, it can not only consume a large amount of tailings, reduce the occupation of land resources and environmental pollution caused by tailings storage, but also reduce the exploitation of sand and gravel and protect the ecological environment.

[0004] Cement is a common curing agent in road engineering, and its construction cost is quite high. In addition, with global warming, the greenhouse effect leads to an increase in CO2 emissions. The corrosion caused by the carbonization reaction of CO2 in the atmosphere and cement-based materials will lead to a reduction in the service life of cement-based materials. At the beginning of the carbonization reaction of cement-based materials, the CaCO3 generated in the process will be deposited on the pore grid in the cement matrix, making the pores of the carbonized layer finer. The finer pores will enhance the strength of hydrated cement, reduce porosity and improve durability; however, over time, the excessive reaction of CO2 will cause the CSH structure to be destroyed, resulting in the decomposition of CSH and the loss of strength of cement-based materials.

[0005] Industrial solid waste solidified iron tailings are used to fill the road base. Due to the small particle size of iron tailings, the roadbed material made using traditional processes using only iron tailings has low strength and cannot meet the roadbed strength requirements.

[0006] Chinese patent application 202210643874.3 discloses an iron tailings road base material, a preparation method and its application. The iron tailings road base material contains the following components by weight: 0.05-0.3 parts of modified polymer, 5-10 parts of quicklime, 10-20 parts of fly ash, 0.5-1 parts of aluminum salt, 0.02-0.1 parts of magnesium salt, 0.02-0.05 parts of calcium salt, 12-15 parts of water, and 100 parts of iron tailings. The iron tailings roadbed material prepared in this patent application has high compressive strength after curing, good water stability and scour resistance, and can be used as the subbase of the road. However, the components of the iron tailings road base material are relatively complex, and modified polymers need to be added. Moreover, in the surrounding areas of road construction, it is difficult to obtain quicklime, fly ash, aluminum salt, magnesium, calcium salt, iron tailings and other raw materials at the same time, which requires long-distance transportation and high cost of use. Summary of the invention

[0007] The purpose of the present invention is to provide an industrial solid waste-based iron tailings pavement base material with high iron tailings consumption, strong carbonization resistance, strong water stability and high mechanical strength in order to solve the above problems existing in the prior art.

[0008] Another object of the present invention is to provide an application method of the above-mentioned industrial solid waste-based iron tailings pavement base material.

[0009] In order to improve the carbonation resistance of cement-based materials, the present invention introduces mineral carbonation technology to select alkaline mineral components to replace part of the cement. This technology is environmentally friendly and is a good CO2 storage technology.

[0010] In order to achieve the above-mentioned object of the present invention, the technical solution adopted by the industrial solid waste-based iron tailings road base material of the present invention is:

[0011] The present invention discloses an industrial solid waste-based iron tailings road base material, which is configured by the following components, and the mass percentage of each component when the total mass of the components is 100% is: 35-60% iron tailings, 10-20% iron tailings coarse sand, 5-16% cement, 0-7% steel slag, 0-10% slag powder, and 15-25% water. The iron tailings and iron tailings coarse sand here refer to the products after the iron ore beneficiation tailings are graded and desludged, and are divided into iron tailings and iron tailings coarse sand according to different coarseness and fineness and different particle size classification. The particle size specifications of the iron tailings are: 70% < 0.3mm sieve hole pass rate < 85%, 50% < 0.075mm sieve hole pass rate < 75%; the particle size specifications of the iron tailings coarse sand are: 40% < 0.3mm sieve hole pass rate < 60%, 10% < 0.075mm sieve hole pass rate < 30%; the particle size specifications of the steel slag are: 50% < 0.3mm sieve hole pass rate < 70%, 15% < 0.075mm sieve hole pass rate < 35%.

[0012] Studies have shown that the preferred raw material composition ratios of the present invention are: iron tailings 40-60%, iron tailings coarse sand 12-20%, cement 8-13%, steel slag 1-3%, slag powder 1.6-6%, and water 17-22%.

[0013] In order to meet the bearing strength requirements of the road base material, the bearing ratio CBR of the iron tailings is 35-45, and the gradation particle size distribution of the iron tailings is:

[0014]

[0015] The gradation particle size distribution of the iron tailings coarse sand is:

[0016]

[0017] The present invention provides an application method of an industrial solid waste-based iron tailings road base material, which is implemented according to the following steps:

[0018] 1) Using sieves of different apertures to screen iron tailings, iron tailings coarse sand, and steel slag raw materials, the mass proportion of the raw materials is based on the mass total of 100%, and the mass percentage of each component is: iron tailings 35-60%, iron tailings coarse sand 10-20%, cement 5-16%, steel slag 0-7%, slag powder 0-10%, water 15-25%; the iron tailings particle size specification is: 70% < 0.3mm sieve hole pass rate < 85%, 50% < 0.075mm sieve hole pass rate < 75%; the iron tailings coarse sand particle size specification is: 40% < 0.3mm sieve hole pass rate < 60%, 10% < 0.075mm sieve hole pass rate < 30%; the steel slag particle size specification is: 50% < 0.3mm sieve hole pass rate < 70%, 15% < 0.075mm sieve hole pass rate < 35%;

[0019] 2) Weigh iron tailings, iron tailings coarse sand, cement, steel slag, and slag powder according to the mass ratio, put them into a mixer, stir and mix evenly, then add water and stir evenly;

[0020] 3) Extruding the mixed material prepared in step 2) with a press, demolding and curing the extruded mixed material, and testing the compressive strength to find that the unconfined compressive strength standard value of cement stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015) is met, thereby obtaining the industrial solid waste-based iron tailings pavement base material;

[0021] 4) Sprinkling water on the road subbase to moisten it, then transporting the industrial solid waste-based iron tailings road base material obtained in step 3) to the top layer of the road base, and using a paver to spread the industrial solid waste-based iron tailings road base material in batches to ensure the elevation and flatness of the pavement;

[0022] 5) Use large-tonnage double steel wheel rollers, vibratory rollers and rubber wheel rollers for combined rolling to ensure that the compaction degree reaches more than 98%; the rolling construction can be divided into three stages: the first stage is the initial compaction, using double steel wheel rollers for rolling construction, the rolling form is static compaction, rolling 1 to 2 times; the second stage is the re-compacting, using vibratory rollers for rolling 3 to 4 times; the last stage is the final compaction, using rubber wheel rollers for rolling 1 to 2 times;

[0023] 6) After the compaction degree is tested by the sand filling method, the curing stage begins. After the compaction degree is qualified, the geotextile must be soaked first and then covered on the top surface of the base layer to keep the geotextile moist during the curing stage.

[0024] Furthermore, the curing time in step 3) is ≥ 7 days.

[0025] Furthermore, the amount of cement added to the raw materials is 10-13% of the total mass of the raw materials, the mass ratio of the added steel slag to the slag powder is 1:3-2:3, and the amount of steel slag and slag powder added accounts for 20-30% of the amount of cement added.

[0026] The present invention uses iron tailings instead of crushed stone for the preparation of road base materials. The first difficulty lies in the control of strength. It is difficult to achieve sufficient strength by using traditional curing agents such as cement and lime. The present invention uses mineral admixtures such as steel slag and slag powder to replace part of the cement, thereby ensuring the strength of the mixture. The second difficulty lies in the control of cracks. The present invention uses steel slag and slag powder, which not only effectively serve as the skeleton of the mixture, but also activate their potential activity through cement hydration reaction, making the structure denser, thereby effectively controlling the size of cracks. Compared with the prior art, the industrial solid waste-based iron tailings road base material and its application method of the present invention have the following advantages:

[0027] (1) The industrial solid waste-based iron tailings pavement base material of the present invention makes full use of the mine solid waste - iron tailings material, improves the resource utilization rate of iron tailings, turns waste into treasure and harm into benefit, and has important promoting significance for comprehensive resource utilization and environmental protection.

[0028] (2) The industrial solid waste-based iron tailings pavement base material in the present invention has better mechanical strength than the traditional inorganic binder stabilized base.

[0029] (3) The industrial solid waste-based iron tailings road base material of the present invention uses a small amount of coarse sand and steel slag as aggregate, which can save the use of sand and gravel and alleviate the shortage of sand and gravel in road engineering.

[0030] (4) The pavement base material of the present invention is added with coarse sand and steel slag, and compared with the pavement base prepared entirely with iron tailings materials, the pavement base has higher strength and can meet more road construction requirements.

[0031] (5) The industrial solid waste-based iron tailings road base material in the present invention is used for the construction of hydraulic pavement base. The mixture has good uniformity and compaction properties, and the compressive strength meets the standard value of unconfined compressive strength of cement-stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015), and can meet the transportation requirements of expressways and first-class highways under extremely heavy and extra-heavy traffic conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram of the application of an industrial solid waste-based iron tailings road base material in a construction site of the present invention;

[0033] Figure 2 This is a SEM picture of an industrial solid waste-based iron tailings road base material of the present invention without adding steel slag or slag powder (Example 2);

[0034] Figure 3 This is a SEM picture of an industrial solid waste-based iron tailings pavement base material of the present invention with steel slag and slag powder added (Example 9). DETAILED DESCRIPTION

[0035] To describe the present invention, an industrial solid waste-based iron tailings pavement base material and an application method thereof are further described in detail below in conjunction with embodiments, but the present invention is not limited to the embodiments.

[0036] Depend on Figure 1 As shown in the figure of the application of an industrial solid waste-based iron tailings road base material in the construction site of the present invention, the industrial solid waste-based iron tailings road base material and the application method thereof are implemented according to the following steps:

[0037] 1) Using sieves of different apertures to screen iron tailings, iron tailings coarse sand, and steel slag raw materials, the mass percentage of each component of the raw material mass ratio based on the total mass of 100% is: iron tailings 35-60%, iron tailings coarse sand 10-20%, cement 5-16%, steel slag 0-7%, slag powder 0-10%, water 15-25%; the iron tailings particle size specification is: 70% < 0.3mm sieve hole pass rate < 85%, 50% < 0.075mm sieve hole pass rate < 75%; the iron tailings coarse sand particle size specification is: 40% < 0.3mm sieve hole pass rate < 60%, 10% < 0.075mm sieve hole pass rate < 30%; the steel slag particle size specification is: 50% < 0.3mm sieve hole pass rate < 70%, 15% < 0.075mm sieve hole pass rate < 35%.

[0038] The bearing ratio CBR of the iron tailings is 35-45, and the gradation particle size distribution of the iron tailings is:

[0039]

[0040] The gradation particle size distribution of the iron tailings coarse sand is:

[0041]

[0042] 2) Weigh iron tailings, iron tailings coarse sand, cement, steel slag, and slag powder according to the mass ratio, put them into a mixer, mix them evenly, then add water and mix them evenly. The mixing time of the mixer is 1 to 2 minutes.

[0043] 3) The mixed material prepared in step 2) is extruded by a press, and the extruded mixed material is demolded and cured. After a curing time of ≥ 7 days, the compressive strength test is carried out and the unconfined compressive strength standard value of cement stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015) is met, and the industrial solid waste-based iron tailings road base material is obtained. In this step, the material must be left to stand for one day before demolding.

[0044] Table 1 shows the standard values ​​of unconfined compressive strength of cement-stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015).

[0045] Table 1 7d unconfined compressive strength standard Rd (MPa) of cement stabilized materials

[0046]

[0047] 4) Sprinkle water on the road subbase to moisten it, then transport the industrial solid waste-based iron tailings road base material obtained in step 3) to the top layer of the road base, and use a paver to spread the industrial solid waste-based iron tailings road base material in batches to ensure the elevation and flatness of the pavement. The paving distance is controlled at 2m / min. Use a paver to spread the industrial solid waste-based iron tailings road base material in batches, with the first paving test section being 100m and each operation section being 200m.

[0048] 5) Use large-tonnage double steel wheel rollers, vibratory rollers and rubber wheel rollers for combined rolling to ensure that the compaction degree reaches more than 98%; the rolling construction can be divided into three stages: the first stage is initial compaction, using double steel wheel rollers for rolling construction, the rolling form is static compaction, rolling 1 to 2 times; the second stage is repeated compaction, using vibratory rollers for rolling 3 to 4 times; finally, final compaction is carried out, using rubber wheel rollers for rolling 1 to 2 times.

[0049] 6) After the compaction degree is tested by the sand filling method, the curing stage begins. After the compaction degree is qualified, the geotextile must be soaked first and then covered on the top surface of the base layer to keep the geotextile moist during the curing stage.

[0050] Examples 1 to 10 are laboratory test results of an industrial solid waste-based iron tailings road base material of the present invention. The proportions and 7-day unconfined compressive strength of the industrial solid waste-based iron tailings road base material at different dosages are shown in Table 2.

[0051] Table 2 Industrial solid waste-based iron tailings pavement base materials and 7-day unconfined compressive strength at different dosages

[0052]

[0053] Mechanism research shows that steel slag is considered a potential mineral admixture because its main chemical components are similar to mineral phases and silicate cement, containing mineral components such as C2S, C3S, C4AF, and have potential gelling properties, so it is called inferior cement clinker. There are some obvious problems with steel slag as a mineral admixture. Steel slag contains a large number of components with low activity or inertness, such as RO phase (CaO-FeO-MgO-MnO solid solution), Fe3O4, etc. By using different mineral admixtures in combination, not only can the advantages of different mineral admixtures be brought into play, but also the mutual blending method can make up for some deficiencies of some mineral admixtures. Slag is a molten body with silicate and aluminosilicate as the main components, which is formed into granular active materials after cold quenching and rapid cooling by combining impurities such as SiO2 and AI2O3 in iron ore and ash in fuel with CaO and MgO decomposed from flux minerals during blast furnace ironmaking.

[0054] from Figure 2 From the SEM picture of an industrial solid waste-based iron tailings pavement base material of the present invention without the addition of steel slag or slag powder (Example 2), it can be seen that when no steel slag or slag powder is added, cement hydration reaction mainly occurs to generate a large amount of needle-shaped product hydrated calcium sulfoaluminate (ettringite) and white flocculent - hydrated calcium silicate gel (CSH).

[0055] from Figure 3 The SEM picture of an industrial solid waste-based iron tailings road base material of the present invention with steel slag and slag powder added (Example 9) shows that by adding industrial solid waste-steel slag and slag powder to replace part of the cement to composite stabilize the iron tailings, not only cement hydration reaction occurs, but also hydrolysis reaction occurs to produce more divalent calcium ions (Ca 2+) so as to carry out ion exchange so that the particles are closely connected. At the same time, mineral admixtures such as steel slag and slag powder also have an improvement mechanism for the mixture. The reaction of steel slag has a strong independence. The hydration of its main gelling phase and the Ca(OH)2 generated by cement hydration do not chemically react, and it mainly acts as a skeleton. The Ca(OH)2 generated by the cement hydration reaction can stimulate the potentially active mineral powder, so that the slag powder undergoes a hydration reaction to generate hydrated calcium silicate, which fills the pores of the mixture, thereby improving the strength of the mixture.

[0056] The construction method of the industrial solid waste-based iron tailings road base material of this embodiment is: first sprinkle water on the base layer to moisten it, then transport the road base material to the top layer of the roadbed and spread it. According to the actual engineering situation of this embodiment, the paving distance is controlled at 2m / min. The industrial solid waste-based iron tailings road base material is spread in batches using a paver. The first paving test section is 100m, and each operation section is 200m to ensure the elevation and flatness of the pavement.

[0057] The gradation particle size distribution of the iron tailings used in the embodiment is:

[0058]

[0059] The coarse sand gradation particle size distribution used in the embodiment is:

[0060]

[0061] A large-tonnage double steel wheel roller, vibratory roller and rubber wheel roller are used for combined rolling to ensure that the compaction degree reaches more than 98%. The rolling construction can be divided into three stages. The first stage is the initial rolling, using a double steel wheel roller for rolling construction, the rolling form is static rolling, rolling 1 to 2 times. The second stage is the re-rolling, rolling 3 to 4 times. Finally, the final rolling is carried out, using a rubber wheel roller for rolling 1 to 2 times.

[0062] After using a vibratory roller to test the compaction degree using the sand filling method, it enters the curing stage. After the compaction degree is qualified, the geotextile must be soaked first and then covered on the top surface of the base layer. The geotextile must be kept moist during the 7-day curing period.

[0063] On-site industrial test verification shows that when the mass percentage of each component in the raw materials is "iron tailings 40-60%, iron tailings coarse sand 12-20%, cement 8-13%, steel slag 1-3%, slag powder 1.6-6%, water 17-22%" and at the same time meets the requirements of "the amount of cement added in the raw materials is 10-13% of the total mass of the raw materials, the mass ratio of the added steel slag to the slag powder is 1:3-2:3, and the amount of steel slag and slag powder added accounts for 20-30% of the amount of cement added", the 7-day unconfined compressive strength of the prepared industrial solid waste-based iron tailings pavement base material is ≥6.5Mpa, which can meet the transportation requirements of expressways and first-class highways under extremely heavy and extra-heavy traffic conditions, and the comprehensive cost of raw materials is also low, and the effect is extremely significant.

Claims

1. An industrial solid waste-based iron tailings road base material, characterized in that The composition is composed of the following components. When the total mass of the raw material components is 100%, the mass percentage of each component is: 35-60% iron tailings, 10-20% iron tailings coarse sand, 10-13% cement, 0-7% steel slag, 0-10% slag powder, and 15-25% water; the amount of steel slag and slag powder added in the raw materials accounts for 20-30% of the amount of cement added; The bearing ratio CBR of the iron tailings is 35-45, and the gradation particle size distribution of the iron tailings is: The gradation particle size distribution of the iron tailings coarse sand is: The steel slag particle size specifications are: 50% < 0.3mm sieve hole passing rate < 70%, 15% < 0.075mm sieve hole passing rate < 35%.

2. The industrial solid waste-based iron tailings road base material according to claim 1, characterized in that The mass percentage of each component is: iron tailings 40-60%, iron tailings coarse sand 12-20%, cement 8-13%, steel slag 1-3%, slag powder 1.6-6%, and water 17-22%.

3. An application method of industrial solid waste-based iron tailings road base material, characterized in that Follow these steps to implement: 1) Using sieves of different apertures to screen iron tailings, iron tailings coarse sand, and steel slag raw materials, the mass percentage of each component of the raw materials when the total mass is 100% is: iron tailings 35-60%, iron tailings coarse sand 10-20%, cement 10-13%, steel slag 0-7%, slag powder 0-10%, water 15-25%; the steel slag particle size specification is: 50% < 0.3mm sieve hole pass rate < 70%, 15% < 0.075mm sieve hole pass rate < 35%; the amount of steel slag and slag powder added in the raw materials accounts for 20-30% of the amount of cement added; The bearing ratio CBR of the iron tailings is 35-45, and the gradation particle size distribution of the iron tailings is: The gradation particle size distribution of the iron tailings coarse sand is: 2) Weigh iron tailings, iron tailings coarse sand, cement, steel slag, and slag powder according to the mass ratio, put them into a mixer, mix them evenly, then add water and mix them evenly; 3) Extruding the mixed material prepared in step 2) with a press, demolding and curing the extruded mixed material, and testing the compressive strength to find that the unconfined compressive strength standard value of cement stabilized materials specified in the "Technical Specifications for Highway Pavement Base Construction" (JTG / F20-2015) is met, thereby obtaining the industrial solid waste-based iron tailings pavement base material; 4) Sprinkle water on the road subbase to moisten it, then transport the mixed material prepared in step 2) to the top layer of the road base, and spread the mixture in batches using a paver to ensure the elevation and flatness of the pavement surface; 5) Use large-tonnage double steel wheel rollers, vibratory rollers and rubber wheel rollers for combined rolling to ensure that the compaction degree reaches more than 98%; the rolling construction can be divided into three stages: the first stage is the initial compaction, using double steel wheel rollers for rolling construction, the rolling form is static compaction, rolling 1 to 2 times; the second stage is the secondary compaction, using vibratory rollers for rolling 3 to 4 times; the last stage is the final compaction, using rubber wheel rollers for rolling 1 to 2 times; 6) After the compaction degree is tested by the sand injection method, the curing stage begins. After the compaction degree is qualified, the geotextile must be soaked first and then covered on the top surface of the base layer to keep the geotextile moist during the curing stage.

4. The method for applying the industrial solid waste-based iron tailings pavement base material as claimed in claim 3, characterized in that The mass percentage of each component when the total mass of the raw materials is 100% is: iron tailings 40-60%, iron tailings coarse sand 12-20%, cement 8-13%, steel slag 1-3%, slag powder 1.6-6%, and water 17-22%.

5. The method for applying the industrial solid waste-based iron tailings pavement base material as claimed in claim 4, characterized in that: The curing time in step 3) is ≥ 7 days.

6. The method for applying an industrial solid waste-based iron tailings pavement base material as claimed in claim 5, characterized in that: The mass ratio of the added steel slag to the slag powder is 1:3 to 2:3.

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