A method for constructing a cement-treated base course using cement tailings as coarse and fine aggregates

Abstract

The present invention belongs to a method for constructing a water-stabilized base course using cement tailings as coarse and fine aggregates. The method includes steps such as proportioning of the cement-stabilized gravel base course, paving of the cement-stabilized gravel base course, rolling of the cement-stabilized gravel base course, and curing of the cement-stabilized gravel base course. Among them: the particle size ratio of graded gravel in the lower cement-stabilized gravel base course is: 20 - 31mm: 10 - 20mm: 3 - 10mm: 0.075 - 3mm = 18%: 32%: 30%: 20%; among which the proportion of the particle size of the cement tailings in the same particle size is 6% of 32%, 6% of 30%, and 3% of 20% respectively; the blending ratio of the cement tailings replacing the corresponding coarse and fine aggregates in the graded gravel in the cement-stabilized base course is 15%. The present invention can ensure that the use of cement tailings as the cement-stabilized gravel base course meets the requirements of excellent quality, and has the advantages of simple and practical method, low cost, saving construction period, good quality and long service life.

Description

Technical Field

[0001] The present invention belongs to a method for constructing a cement stabilized base course by using cement tailings as coarse and fine aggregates. Background Art

[0002] The expressway pavement is composed of a 15-cm-thick crushed stone subbase, a 34-cm-thick cement stabilized gravel base course is provided at the upper end of the subbase, and then an asphalt surface course with a total thickness of 19 cm for the lower, middle and upper layers is laid on the upper end of the cement stabilized gravel base course. Among them, the cement stabilized gravel base course plays a connecting role. The indexes of the integrity, strength and compaction degree of the cement gravel stabilized base course play a key role in the quality of the expressway.

[0003] Cement tailings are the solid substances remaining after the beneficiation of limestone, the raw material of cement. It is a mixed material with a particle size between 0.075 and 20 mm. Cement tailings belong to waste materials. A large amount of stacking not only occupies a large amount of land and buries plants, but more seriously, the stacked cement tailings waste will be discharged into rivers, valleys and depressions with rainwater, greatly polluting and damaging the human living environment. Therefore, the utilization of cement tailings is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing a cement stabilized base course by using cement tailings as coarse and fine aggregates, which can ensure that the use of cement tailings as a stabilized gravel base course meets the requirements of excellent quality, and has the advantages of simple and practical method, low cost, construction period saving, good quality and long service life.

[0005] To this end, a method for constructing a cement stabilized base course by using cement tailings as coarse and fine aggregates of the present invention includes the following steps:

[0006] (1) Select cement tailings, and conduct preliminary material selection on the stacked cement tailings to remove plant weeds, grass roots and tree roots in the cement tailings to obtain the preliminary selected cement tailings;

[0007] (2) Screen the preliminary selected cement tailings to obtain particle size batching of 0.075 - 3 mm, 3 - 10 mm, and 10 - 20 mm. Stack the particle size batching of different sizes separately, spray water on the surface of each stacked batching to make it moist, and then cover it with plastic cloth;

[0008] (3) Cement stabilized gravel base course batching: The cement stabilized gravel base course is divided into a lower base course and an upper base course. The lower base course is located at the lower part of the cement stabilized gravel base course with a thickness of 21 cm; the upper base course is located at the upper part of the cement stabilized gravel base course with a thickness of 13 cm;

[0009] (a) For the graded gravel in the lower base course of cement stabilized gravel, the particle size ratio is: 20 - 31 mm : 10 - 20 mm : 3 - 10 mm : 0.075 - 3 mm = 18% : 32% : 30% : 20%; among which, the particle size proportion of cement tailings in the same particle size is 6% of 32%, 6% of 30%, and 3% of 20% respectively;

[0010] In the lower base course of cement stabilized gravel, the weight ratio of each component is: graded gravel : cement : lime = 100 : 4.7 : 1; the maximum dry density is 2.47 g / cm 3 , and the water content is 4.6%;

[0011] (b) For the graded gravel in the upper base course of cement stabilized gravel, the particle size ratio is: 20 - 31 mm : 10 - 20 mm : 3 - 10 mm : 0.075 - 3 mm = 10% : 30% : 32% : 28%; among which, the particle size proportion of cement tailings in the same particle size is 2% of 30%, 8% of 32%, and 5% of 28% respectively;

[0012] In the lower base course of cement stabilized gravel, the weight ratio of each component is: graded gravel : cement : lime = 100 : 5.1 : 0.5; the maximum dry density is 2.43 g / cm 3 , and the water content is 4.7%;

[0013] (4) Paving of the cement stabilized gravel base course: It is divided into two - time forming paving for the upper base course and the lower base course;

[0014] (a) The paving of the lower base course is to use a large anti - segregation paver to achieve a one - time paving of the full thickness of 21 cm and the full width; once the paving of the lower base course of cement stabilized gravel is completed, immediately carry out the rolling of the cement stabilized gravel base course, or ensure that the rolling is carried out closely following the completion of the previous paving. Use the HD130 double - steel - wheel roller to carry out static rolling for 1 time, with a rolling speed of 1.5 - 1.7 km / h. After ensuring the flatness, then use the Yz36 single - steel - wheel roller to carry out strong vibration for 1 time and the YL37 rubber - tired roller to carry out kneading rolling for 1 time, with a rolling speed of 2.0 - 2.5 km / h;

[0015] (b) Before paving the upper base course, spray a layer of cement slurry on the upper end surface of the lower base course, and then immediately pave the upper base course; the paving of the upper base course is achieved by using a large anti-segregation paver to form a single-pass paving of the full thickness and full width with a thickness of 13 cm. Once the paving of the cement stabilized gravel upper base course is completed, immediately carry out the rolling of the cement stabilized gravel base course, or ensure that the rolling is carried out closely following the completion of the previous paving. Use an HD130 double-drum roller to roll statically for 1 pass at a rolling speed of 1.5 - 1.7 km / h. After ensuring the flatness, then use a Yz36 single-drum roller to vibrate strongly for 1 pass and a YL37 rubber-tyred roller to knead and roll for 1 pass at a rolling speed of 2.0 - 2.5 km / h; and the combination of using a Yz36 single-drum roller to vibrate strongly and a YL37 rubber-tyred roller to knead and roll at a rolling speed of 2.0 - 2.5 km / h forms a combined cyclic rolling; carry out 4 passes of combined cyclic rolling on the cement stabilized gravel base course that has passed the initial rolling section to ensure the compaction degree; finally, use an HD130 double-drum roller to roll statically for 3 passes at a rolling speed of 2.0 - 2.5 km / h for static finishing;

[0016] (5) Curing of the cement stabilized gravel base course: Once the rolling of the upper base course is completed, immediately carry out the curing of the cement stabilized gravel base course. First, use a water sprinkler to spray water on the surface of the cement stabilized gravel base course in a spray mode, with a water spraying amount of 10 - 15 liters / m 2 , and then spread a curing film on the surface of the cement stabilized gravel upper base course, and then cover a geotextile on the curing film. Environmental protection sand bags are pressed at intervals on the geotextile. The peripheries of the curing film and the geotextile are sealed and fixed with sand bags. After 5 - 7 days of the curing period, remove the curing film and the geotextile to complete the construction of the water stable base course using cement tailings as coarse and fine aggregates construction.

[0017] As a further description of the above technical solution: The mixing ratio of cement tailings replacing the corresponding coarse and fine aggregates in the graded gravel in the cement stabilized base course is 15%.

[0018] As a further description of the above technical solution: In the spraying of a layer of cement slurry on the upper end surface of the lower base course, the weight ratio of cement to water is 10:100.

[0019] As a further description of the above technical solution: The "immediately" mentioned refers to an interval time less than 5 minutes.

[0020] As a further description of the above technical solution: After the particle size batching of the cement tailings is mixed with the same particle size ratio, it must be evenly mixed.

[0021] As a further description of the above technical solution: The mixing time of the paving material of the water stable base course using cement tailings as coarse and fine aggregates is not less than 15 min.

[0022] The above method achieves the purpose of the present invention.

[0023] The present invention has the following advantages and positive effects compared with the prior art:

[0024] (1) The present invention can ensure that the use of cement tailings cement as a stabilized gravel base meets the requirements of excellent engineering quality. It has the advantages of simple and practical method, low cost, construction period saving, good quality and long service life. Comparative tests show that the cement stabilized gravel base of the present invention can meet the high-quality standard of engineering quality.

[0025] (2) The present invention uses cement tailings to replace coarse and fine aggregates in the construction of the water-stable base, which can not only reduce production costs, but also reduce carbon emissions, effectively relieve environmental pressure, and greatly improve the utilization rate of waste mineral resources. Preliminary calculations show that the present invention can generally save 28% of the construction cost and shorten the construction period by 10%, with good economic benefits.

[0026] (3) The present invention greatly strengthens the cement stabilized gravel base and increases the weight-bearing area, significantly extending the service life of the highway. Comparative tests show that for two adjacent sections of the highway, the service life of the present invention is extended by 2 to 3 times compared with the prior art, and there are no phenomena such as loss, pavement cracking, collapse, and hollowing. Specific Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all belong to the protection scope of the present invention. The construction methods in the following embodiments are all conventional methods unless otherwise specified. The materials, devices, equipment, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0028] Embodiment 1: A method for constructing a water-stable base using cement tailings as coarse and fine aggregates, comprising the following steps:

[0029] (1) Select cement tailings, and conduct preliminary material selection on the piled-up cement tailings to remove plant weeds, grass roots, and tree roots in the cement tailings to obtain the preliminary selected cement tailings;

[0030] (2) Screen the preliminary selected cement tailings to obtain particle size mixtures of 0.075 - 3 mm, 3 - 10 mm, and 10 - 20 mm. Stack the particle size mixtures of different sizes separately, spray water on the surface of each stacked mixture to make it moist, and then cover it with plastic sheeting;

[0031] (3) Mix proportioning of cement stabilized gravel base course: The cement stabilized gravel base course is divided into the lower base course and the upper base course. The lower base course is located at the lower part of the cement stabilized gravel base course with a thickness of 21 cm; the upper base course is located at the upper part of the cement stabilized gravel base course with a thickness of 13 cm;

[0032] (a) The particle size ratio of graded gravel in the lower base course of cement stabilized gravel is: 20 - 31 mm : 10 - 20 mm : 3 - 10 mm : 0.075 - 3 mm = 18%:32%:30%:20%; among which the particle size proportion of cement tailings in the same particle size ratio accounts for 6% of 32%, 6% of 30%, and 3% of 20% respectively;

[0033] The weight ratio of each component in the lower base course of cement stabilized gravel is: graded gravel : cement : lime = 100 : 4.7 : 1; the maximum dry density is 2.47 g / cm 3 , and the water content is 4.6%;

[0034] (b) The particle size ratio of graded gravel in the upper base course of cement stabilized gravel is: 20 - 31 mm : 10 - 20 mm : 3 - 10 mm : 0.075 - 3 mm = 10%:30%:32%:28%; among which the particle size proportion of cement tailings in the same particle size ratio accounts for 2% of 30%, 8% of 32%, and 5% of 28% respectively;

[0035] The mixing ratio of cement tailings replacing the corresponding coarse and fine aggregates in the graded gravel of the cement stabilized base course is 15%.

[0036] The weight ratio of each component in the lower base course of cement stabilized gravel is: graded gravel : cement : lime = 100 : 5.1 : 0.5; the maximum dry density is 2.43 g / cm 3 , and the water content is 4.7%;

[0037] After the particle size proportion of the said cement tailings is mixed with the same particle size ratio, it must be evenly mixed. The mixing time of the paving material of the cement tailings as the coarse and fine aggregates for the construction of the water stable base course is not less than 15 minutes.

[0038] (4) Paving of cement stabilized gravel base course: It is divided into two - time forming paving of the upper base course and the lower base course;

[0039] (a) The paving of the lower base course is to use a large anti - segregation paver to achieve a one - time paving and forming of the full thickness of 21 cm and the full width; once the paving of the lower base course of cement stabilized gravel is completed, immediately carry out the rolling of the cement stabilized gravel base course, or ensure that the rolling is carried out immediately after the front paving is completed. Use the HD130 double - steel - wheel roller to roll statically for 1 time with a rolling speed of 1.5 - 1.7 km / h. After ensuring the flatness, then use the Yz36 single - steel - wheel roller to vibrate strongly for 1 time and the YL37 rubber - tired roller to knead and press for 1 time with a rolling speed of 2.0 - 2.5 km / h.

[0040] (b) Before paving the upper base course, a layer of cement slurry is sprayed on the upper end surface of the lower base course. The weight ratio of cement to water in the cement slurry is 10:100. Then, the paving of the upper base course is immediately carried out. The paving of the upper base course is achieved by using a large anti-segregation paver to form a one-time paving of the full thickness of 13 cm and the full width at one time. Once the paving of the cement-stabilized gravel upper base course is completed, the compaction of the cement-stabilized gravel base course is immediately carried out, or the construction is carried out to ensure that the compaction follows closely after the completion of the previous paving. First, use an HD130 double-drum roller to statically roll once at a rolling speed of 1.5 - 1.7 km / h. After ensuring the flatness, then use a Yz36 single-drum roller to vibrate strongly once and a YL37 rubber-tyred roller to knead and roll once at a rolling speed of 2.0 - 2.5 km / h. The combination of using a Yz36 single-drum roller to vibrate strongly and a YL37 rubber-tyred roller to knead and roll at a rolling speed of 2.0 - 2.5 km / h forms a combined cyclic compaction. The cement-stabilized gravel base course that has passed the initial compaction section is then subjected to 4 combined cyclic compactions to ensure the compaction degree. Finally, use an HD130 double-drum roller to statically roll 3 times at a rolling speed of 2.0 - 2.5 km / h for static finishing.

[0041] (5) Curing of the cement-stabilized gravel base course: Once the compaction of the upper base course is completed, the curing of the cement-stabilized gravel base course is immediately carried out. First, use a sprinkler truck to spray water on the surface of the cement-stabilized gravel base course in a spray manner, with a water spraying amount of 10 - 15 liters / m 2 , and then spread a curing film on the surface of the cement-stabilized gravel upper base course, and then cover a geotextile on the curing film. Environmental protection sand bags are pressed at intervals on the geotextile. The peripheries of the curing film and the geotextile are sealed and fixed with sand bags. After 5 - 7 days of the curing period, the curing film and the geotextile are peeled off to complete the construction of the water-stabilized base course using cement tailings as coarse and fine aggregates. The film and the geotextile are products sold on the market.

[0042] Inspect and test the cement-stabilized gravel base course, conduct compaction degree detection on the cement-stabilized gravel base course, and deal with the unqualified points detected until they reach the qualified standard.

[0043] The so-called "immediately" means that the interval time is less than 5 minutes.

[0044] The test results of the present invention are as follows:

[0045] (1) Through test detection, the technical indexes of the cement tailings graded gravel meet the design and specification requirements. The test results are shown in Table 1-1:

[0046] Table 1-1 Technical indexes of the quality of cement tailings graded gravel

[0047]

[0048] (2) Technical indicators of the selected cement. Huaxin or Gezhouba brand cement is selected, and after test detection, all technical indicators meet the requirements of the design and specifications. The test results are shown in Table 1-2:

[0049] Table 1-2 Technical indicators of cement quality

[0050]

[0051] (3) Unconfined compressive strength test results of the cement-tailings stabilized base containing 15% cement are shown in Table 1-3

[0052] Table 1-3: Unconfined compressive strength test results of the cement-tailings stabilized base with 15% cement admixture

[0053]

[0054] After test detection, all technical indicators of the unconfined compressive strength test results of the cement-tailings stabilized base with 15% cement admixture meet the requirements of the design and specifications.

[0055] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for constructing a cement-treated base course using cement tailings as coarse and fine aggregates, characterized in that, It includes the following steps: (1) Select cement tailings, conduct preliminary material selection on the piled-up cement tailings, remove plant weeds, grass roots, and tree roots from the cement tailings to obtain the preliminary selection of cement tailings; (2) Screen the preliminary selection of cement tailings to obtain particle size batching of 0.075 - 3mm, 3 - 10mm, and 10 - 20mm. Stack the particle size batching of different sizes separately, spray water on the surface of each stacked batching to make it moist, and then cover it with plastic sheeting; (3) Batching for the cement stabilized sand and gravel base: The cement stabilized sand and gravel base is divided into a lower base and an upper base. The lower base is located at the lower part of the cement stabilized sand and gravel base with a thickness of 21 cm; the upper base is located at the upper part of the cement stabilized sand and gravel base with a thickness of 13 cm; (a) The particle size ratio of graded sand and gravel in the lower base of the cement stabilized sand and gravel is: 20 - 31mm : 10 - 20mm : 3 - 10mm : 0.075 - 3mm = 18% : 32% : 30% : 20%; among which, the particle size batching of cement tailings accounts for 6% of 32%, 6% of 30%, and 3% of 20% respectively in the same particle size ratio; The weight ratio of each component in the lower base course of cement stabilized gravel is: graded gravel: cement: lime = 100: 4.7: 1; the maximum dry density is 2.47 g / cm 3 , and the water content is 4.6%; (b) The particle size ratio of graded sand and gravel in the upper base of the cement stabilized sand and gravel is: 20 - 31mm : 10 - 20mm : 3 - 10mm : 0.075 - 3mm = 10% : 30% : 32% : 28%; among which, the particle size batching of cement tailings accounts for 2% of 30%, 8% of 32%, and 5% of 28% respectively in the same particle size ratio; The weight ratio of each component in the lower base course of cement stabilized gravel is: graded gravel: cement: lime = 100:5.1:0.5; the maximum dry density is 2.43 g / cm 3 , and the water content is 4.7%; (4) Paving of the cement stabilized sand and gravel base: It is divided into two - time forming paving for the upper base and the lower base; (a) The paving of the lower base is to use a large anti - segregation paver to achieve a one - time paving and forming of the full thickness of 21 cm and the full width. Once the paving of the lower base of the cement stabilized sand and gravel is completed, immediately carry out the compaction of the cement stabilized sand and gravel base, or ensure that the compaction is carried out closely following the completion of the previous paving. Use an HD130 double - steel - wheel roller to apply static pressure once with a compaction speed of 1.5 - 1.7 km / h. After ensuring the flatness, then use a Yz36 single - steel - wheel roller to apply strong vibration once and a YL37 rubber - tired roller to apply kneading pressure once, with a compaction speed of 2.0 - 2.5 km / h; (b) Before paving the upper base course, a layer of cement slurry is sprayed on the upper end surface of the lower base course, and then the upper base course is immediately paved; the paving of the upper base course is achieved by using a large anti-segregation paver to complete a one-time paving of the full thickness of 13 cm and the full width. Once the paving of the cement-stabilized gravel upper base course is completed, the compaction of the cement-stabilized gravel base course is immediately carried out, or the construction is carried out to ensure that the compaction follows closely after the previous paving is completed. The HD130 double-drum roller is used for static compaction once at a rolling speed of 1.5 - 1.7 km / h. After ensuring the flatness, the Yz36 single-drum roller is used for strong vibration compaction once and the YL37 rubber-tired roller is used for kneading compaction once at a rolling speed of 2.0 - 2.5 km / h; the strong vibration compaction with the Yz36 single-drum roller and the kneading compaction with the YL37 rubber-tired roller at a rolling speed of 2.0 - 2.5 km / h form a combined cyclic compaction; the cement-stabilized gravel base course that has passed the initial compaction section is subjected to 4 combined cyclic compactions to ensure the compaction degree; finally, the HD130 double-drum roller is used for static compaction 3 times at a rolling speed of 2.0 - 2.5 km / h for static finishing; (5) Curing of the cement stabilized gravel base course: Once the upper base course is rolled, the curing of the cement stabilized gravel base course shall be carried out immediately. First, use a sprinkler truck to spray water on the surface of the cement stabilized gravel base course, with the water spraying volume being 10 - 15 liters / m 2 , and then spread the curing film on the surface of the upper base course of the cement stabilized gravel, and then cover the geotextile on the curing film. Environmental protection sand bags are pressed at intervals on the geotextile. The peripheries of the curing film and the geotextile are sealed and fixed with sand bags. After 5 - 7 days of the curing period, remove the curing film and the geotextile to complete the construction of the water stable base course with cement tailings as fine and coarse aggregates.

2. The method according to claim 1, wherein: In the described cement-stabilized base course, the mixing ratio of cement tailings replacing the corresponding coarse and fine aggregates in the graded gravel is 15%.

3. The method according to claim 1, characterized in that: In the described spraying of a layer of cement slurry on the upper end surface of the lower base course, the weight ratio of cement to water is 10:

100.

4. The method according to claim 1, characterized in that: The described "immediately" means that the interval time is less than 5 minutes.

5. The method according to claim 1, characterized in that: After the particle size batching of the described cement tailings is mixed with the same particle size ratio, it must be evenly mixed.

6. The method according to claim 1, wherein: The mixing time of the described cement tailings as the paving material for the coarse and fine aggregates in the construction of the water-stabilized base course is not less than 15 minutes.

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