Ardealite-based drainage base layer based on construction waste and application method of ardealite-based drainage base layer

Abstract

The invention discloses a construction waste-based ardealite-based drainage base layer and an application method thereof, and the construction waste-based ardealite-based drainage base layer comprises 120-200 parts by weight of modified recycled aggregate, 0-80 parts by weight of modified natural aggregate, 8-8.5 parts by weight of cement and 15-16 parts by weight of water, wherein the modified recycled aggregate is prepared from modified recycled aggregate with the particle size of 0-5mm, modified recycled aggregate with the particle size of 5-10mm and modified recycled aggregate with the particle size of 10-31.5 mm according to the mass ratio of (90-92): (30-32): (82-87). The resource utilization rate and the compressive strength of the drainage base layer are improved, the production cost is reduced, and the stockpiling pressure of the construction waste and the ardealite is relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of industrial waste, and particularly relates to a phosphogypsum-based drainage base course based on construction waste and an application method thereof. Background Art

[0002] Phosphogypsum is an industrial waste discharged during the wet production of phosphoric acid. Usually, 4.5 - 5 tons of phosphogypsum slag are produced for every 1 ton of wet-process phosphoric acid produced. At present, the annual phosphogypsum discharge in China is 75 million tons, and 30 million tons are comprehensively utilized, and the newly added stockpile still remains at about 45 million tons. Phosphogypsum is mainly used as a cement retarder, building gypsum, gypsum blocks, filling materials, etc. However, the impurities in phosphogypsum are numerous and the utilization cost is high, which limits the resource utilization of phosphogypsum and leads to an increasing annual stockpile of phosphogypsum.

[0003] Construction waste refers to the waste generated during construction activities such as construction, demolition, and decoration, including concrete, bricks and tiles, asphalt mixtures, etc. In recent years, with the booming development of the construction industry, the quantity of construction waste has also increased rapidly. The total amount of construction waste generated in China every year has exceeded 20 trillion tons. However, at present, most construction waste is still treated by traditional landfill or open-air stacking methods, which not only wastes a large amount of land resources but also may cause environmental pollution. Although the recycling of construction waste has been promoted in some areas, the overall utilization rate is still low. Currently, the main recycling scheme for construction waste is to classify and crush the construction waste and screen it to produce recycled aggregates that can partially or completely replace natural sand and gravel aggregates. Compared with natural sand and gravel aggregates, the surface of recycled aggregates is wrapped with a considerable amount of cement mortar. The strength of the cement mortar is low, the porosity is large, and there are many edges and corners. While reducing the strength of the recycled aggregates, it also makes the void ratio and water absorption rate of the recycled aggregates larger than those of natural sand and gravel aggregates during use, thus affecting the actual application effect and service life of the recycled aggregates.

[0004] Chinese Patent CN108569854A discloses a method for preparing recycled aggregates from construction waste. The main steps are as follows: The construction waste is pretreated and passed through a rolling screen to obtain waste solid materials and waste soil. The waste solid materials are decontaminated, and then the decontaminated waste solid materials are repeatedly crushed, magnetically separated, and screened to obtain materials with a particle size of less than 30 mm. Then the materials are crushed again to remove the surface coatings, and after being polished by a ball mill and screened again to obtain recycled aggregates with different particle sizes. This method can reduce the amount of cement mortar coated on the surface of the recycled aggregates by polishing the surface of the materials with a ball mill and make the shape of the recycled aggregates more regular.

[0005] Chinese Patent CN111318550B discloses a method for preparing recycled aggregate from construction waste. The construction waste is pre-crushed and screened, and then through separation and impurity removal, and vibration screening, the initial recycled aggregate and crushed materials are obtained. The initial recycled aggregate is subjected to secondary crushing and vibration screening to obtain secondary materials. The secondary materials are heated by introducing steam under closed conditions, ground, screened, and air-selected to obtain coarse recycled aggregate and fine recycled aggregate. This method can remove the cement mortar on the smooth and sunken surfaces of the recycled aggregate, improving the overall removal rate of the cement mortar on the surface of the recycled aggregate; the heat diffusion effect of using steam for heating is good, and there is no subsequent sewage treatment problem.

[0006] The recycled aggregate prepared from construction waste has a high porosity due to which it is very suitable for the construction of permeable pavement structures or drainage systems. However, a high porosity will affect the actual application effect and service life. Moreover, how to adjust the particle size of the recycled aggregate so that it takes into account both water permeability and durability when applied in permeable pavement structures has become one of the urgent problems to be solved in the application of recycled aggregate in permeable pavement structures. Summary of the Invention

[0007] In view of the above technical problems, the present invention provides a phosphogypsum-based drainage base course based on construction waste and its application method, which improves the resource utilization rate and the compressive strength of the drainage base course, reduces the production cost, and alleviates the stacking pressure of construction waste and phosphogypsum.

[0008] To achieve the above object, the present invention provides a phosphogypsum-based drainage base course based on construction waste, comprising 120 - 20 parts by weight of modified recycled aggregate, 0 - 80 parts by weight of modified natural aggregate, 8 - 8.5 parts by weight of cement, and 15 - 16 parts by weight of water, wherein the modified recycled aggregate is composed of modified recycled aggregates with particle sizes of 0 - 5mm, 5 - 10mm, and 10 - 31.5mm in a mass ratio of 90 - 92:30 - 32:82 - 87.

[0009] Preferably, the preparation method of the modified recycled aggregate comprises the following steps: (1) Ball-mill phosphogypsum and add water to make phosphogypsum slurry; (2) Place the recycled aggregate in the phosphogypsum slurry and mix and impregnate for 1 - 3h; (3) After impregnation, filter and dry to obtain the modified recycled aggregate.

[0010] More preferably, the water content in the phosphogypsum slurry in step (1) is 30 - 50%.

[0011] More preferably, the recycled aggregate in step (2) is obtained by recycling and crushing waste concrete and bricks, and the particle size is 0 - 31.5mm.

[0012] Preferably, the preparation method of the modified natural aggregate comprises the following steps: (1) Mix phosphogypsum and an activator evenly; (2) Mix the activated phosphogypsum and fly ash evenly to obtain a composite modifier; (3) Mix the composite modifier and the natural aggregate evenly to obtain the modified natural aggregate.

[0013] More preferably, the mass of the activator in step (1) is 1-15% of that of the phosphogypsum; the activator is any one of sodium bicarbonate, sodium hydroxide, and lime.

[0014] More preferably, the mass ratio of the activated phosphogypsum to the fly ash in step (2) is 3-5:5-7.

[0015] More preferably, the mass of the composite modifier in step (3) is 18-25% of the mass of the natural aggregate; the natural aggregate is one or more of gravel, river sand, and manufactured sand.

[0016] The present invention also provides an application method of a phosphogypsum-based drainage base course based on construction waste, which is characterized in that it comprises the following steps: (1) Clean and level the construction site; (2) Lay an impermeable cloth and install a permeable pipe; (3) Mix the modified recycled aggregate, the modified natural aggregate, cement, and water to prepare a raw material for the phosphogypsum-based drainage base course, and spread and compact it; (4) Cure.

[0017] Preferably, the paving length during compaction in step (3) is 50-80 cm.

[0018] More preferably, during compaction, the principle of "first light then heavy, first slow then fast, first static then vibrating, first edge then middle, first low then high" is followed, and compaction is carried out twice: Initial compaction: Static compaction for 2 passes, light vibration for 1 pass, strong vibration for 3 passes; the speed is 1.5 km / h - 1.7 km / h, the length of one-time rolling is generally 50 m - 80 m, and the overlapping of the wheels during compaction by the roller should be 1 / 2; Final compaction: Static compaction for 1 pass, the speed is 1.8 km / h - 2.2 km / h, and the overlapping of the wheels during compaction by the roller should be 1 / 2.

[0019] The beneficial effects of the present invention are as follows: 1. By using construction waste to obtain recycled aggregate through crushing and screening, and then using the recycled aggregate as a raw material for the drainage base course, the treatment pressure of construction waste is reduced, the resource utilization efficiency is improved, and the cost of the drainage base course is reduced.

[0020] 2. The properties of recycled aggregates and natural aggregates are improved by modifying them with phosphogypsum. By means of surface modification, phosphogypsum is filled into the pores on the surface of recycled aggregates, reducing the water absorption of recycled aggregates and significantly increasing the compressive strength, thus improving the overall stability and durability of recycled aggregates, and enabling them to be widely used in the construction of road bases or sub-bases. The natural aggregates are modified by means of chemical modification. Alkaline activators such as sodium hydroxide are used to activate phosphogypsum, converting calcium sulfate therein into a more water-soluble form, and then it is mixed with fly ash to form a composite modifier, which is then mixed with natural aggregates to cause a chemical reaction on the surface of natural aggregates, changing the surface structure, thereby improving the overall properties of natural aggregates and ultimately increasing the compressive strength of natural aggregates. The modified natural aggregates and modified recycled aggregates are mixed as aggregates, significantly increasing the compressive strength of the drainage base course.

[0021] 3. By regulating the gradation of recycled aggregates and selecting the dosages of different modified recycled aggregates according to different particle size ranges, a void-type skeleton can be formed in the drainage base course, and recycled aggregates with smaller particle sizes are selected to form a larger void ratio, reducing the consumption of cement, thereby preparing a composite that is suitable for road surface conditions requiring a large amount of water permeability while ensuring its structural stability and durability requirements. Specific embodiments

[0022] The technical solutions of the present invention will be further explained and illustrated below in conjunction with specific embodiments. It should be noted that the following embodiments are only the preferred embodiments of the present invention and should not be construed as limiting the present invention. The protection scope of the present invention shall be subject to the content recorded in the claims. Modifications and substitutions made by those skilled in the art to the technical solutions of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Example 1 The modified recycled aggregates are prepared using phosphogypsum and construction waste, and the specific steps are as follows: (1) Collect construction waste, perform pre-crushing and pre-screening, remove sundries such as steel bars, wood, glass, plastics, and electric wires, to obtain materials with a particle size ≤ 200 mm; (2) Place the materials in a crusher for crushing and screening to obtain recycled aggregates with a particle size ≤ 31.5 mm; (3) Take phosphogypsum, add water and grind it into a phosphogypsum slurry with a water content of 40%; (4) Place the recycled aggregates in the phosphogypsum slurry, stir and mix evenly, and soak for 2 h; (5) After the soaking is completed, perform solid-liquid separation, and dry the solid to obtain the modified recycled aggregates.

[0024] Example 2 Prepare modified natural aggregate using phosphogypsum and natural aggregate - gravel. The specific steps are as follows: (1) Take 1 part by weight of phosphogypsum, add water and grind it into phosphogypsum slurry, where the water content of the phosphogypsum slurry is 80%; (2) Add 0.05 part by weight of sodium hydroxide to the phosphogypsum slurry, stir and mix for reaction for 10 min to obtain activated phosphogypsum; (3) Mix the activated phosphogypsum and fly ash in a mass ratio of 3:7, stir and mix evenly to obtain a composite modifier; (4) Stir and mix the composite modifier and gravel evenly to obtain modified natural aggregate; where the mass of the composite modifier is 20% of the mass of the gravel.

[0025] Example 3 A phosphogypsum-based drainage base course based on construction waste includes 120 parts by weight of the modified recycled aggregate prepared in Example 1, 80 parts by weight of the modified natural aggregate prepared in Example 2, 8 parts by weight of cement and 15 parts by weight of water; where the modified recycled aggregate is composed of modified recycled aggregates with particle sizes of 0 - 5 mm, 5 - 10 mm and 10 - 31.5 mm in a mass ratio of 91:31:85; The preparation method is to mix the above raw materials and stir to obtain the drainage base course material, and then spread and compact it to obtain the drainage base course.

[0026] Example 4 A phosphogypsum-based drainage base course based on construction waste includes 160 parts by weight of the modified recycled aggregate prepared in Example 1, 40 parts by weight of the modified natural aggregate prepared in Example 2, 8 parts by weight of cement and 15 parts by weight of water; the preparation method is the same as that of Example 3.

[0027] Example 5 A phosphogypsum-based drainage base course based on construction waste includes 200 parts by weight of the modified recycled aggregate prepared in Example 1, 8.5 parts by weight of cement and 16 parts by weight of water; the preparation method is the same as that of Example 3.

[0028] Example 6 A phosphogypsum-based drainage base course based on construction waste has the same formula as Example 3, only changing the mass ratio of different particle sizes of the modified recycled aggregate to 90:30:82.

[0029] Example 7 A phosphogypsum-based drainage base course based on construction waste has the same formula as Example 3, only changing the mass ratio of different particle sizes of the modified recycled aggregate to 92:32:87.

[0030] Comparative Example 1 A phosphogypsum-based drainage base course, with the formula and preparation method the same as in Example 3, except that the modified recycled aggregate is replaced by recycled aggregate prepared by crushing and screening construction waste.

[0031] Comparative Example 2 A phosphogypsum-based drainage base course, with the formula and preparation method the same as in Example 3, except that the modified natural aggregate is replaced by unmodified gravel as the natural aggregate.

[0032] Comparative Example 3 A drainage base course, with the formula and preparation method the same as in Example 3, replacing the modified recycled aggregate with recycled aggregate prepared by crushing and screening construction waste, and replacing the modified natural aggregate with unmodified gravel as the natural aggregate.

[0033] Comparative Example 4 A phosphogypsum-based drainage base course, with the formula and preparation method the same as in Example 3, except that the mass ratio of different particle sizes of the modified recycled aggregate is changed to 1:1:1.

[0034] Comparative Example 5 A phosphogypsum-based drainage base course, comprising 60 parts by weight of the modified recycled aggregate prepared in Example 1, 140 parts by weight of the modified natural aggregate prepared in Example 2, 8 parts by weight of cement, and 15 parts by weight of water; the preparation method is the same as in Example 3.

[0035] Comparative Example 6 A phosphogypsum-based drainage base course, comprising 200 parts by weight of the modified natural aggregate prepared in Example 2, 8 parts by weight of cement, and 15 parts by weight of water; the preparation method is the same as in Example 3.

[0036] Comparative Example 7 A phosphogypsum-based drainage base course, with the formula and preparation method the same as in Example 3, except that the preparation method of the modified natural aggregate is changed to be the same as in Example 1.

[0037] Example 8 A phosphogypsum-based drainage base course, with the formula and preparation method the same as in Example 3, except that the preparation method of the recycled aggregate is changed to be the same as in Example 2.

[0038] Example 7 Take the drainage base courses prepared by paving and compaction from the above examples and comparative examples, with a thickness of 20 cm, and then normally cure for 7 - 28 d, and detect the water content and compressive strength of the drainage base courses. The results are shown in the following table: Table 1 Performance parameters of the drainage base course

[0039] As can be seen from Table 1, recycled aggregates prepared from construction waste can be used to prepare a drainage base course, construct a permeable pavement, reduce the consumption of natural aggregates, and increase the compressive strength of the drainage base course. Modifying the recycled aggregates and natural aggregates separately with phosphogypsum to form a layer of phosphogypsum on the surface of the aggregates can fill the micro-pores on the surface of the aggregates, reduce their water absorption rate, and significantly increase the compressive strength of the aggregates, thereby improving the durability of the drainage base course. Mixing the recycled aggregates according to different particle sizes facilitates the formation of a skeleton structure during the paving and compaction process, and then forms an appropriate void ratio with cement, facilitating the permeation of water while ensuring a relatively high compressive strength.

[0040] Example 9 Select a secondary urban road with a drainage project to be constructed at one end, with a width of 40.0 m and a length of 520 m. The width of 40.0 m consists of 3.5 m sidewalk, 1.5 m green belt, 3.5 m non-motor vehicle lane, 4.0 m motor-vehicle and non-motor vehicle separation green belt, 15.0 m motor vehicle lane, 4.0 m motor-vehicle and non-motor vehicle separation green belt, 3.5 m non-motor vehicle lane, 1.5 m green belt, and 3.5 m sidewalk. The pavement structure of the non-motor vehicle lane from top to bottom is as follows: 4 cm thick AC-13C type fine-grained asphalt concrete layer, 0.5 L / m 2 Tack coat layer, 6 cm thick PAC-20C medium-grained permeable asphalt concrete layer, 0.5 L / m 2 Tack coat, 32 cm thick drainage base course (rolled in two layers), 15 cm thick graded crushed stone layer containing drain pipes, Impermeable composite geotextile; For the pavement construction of the non-motor vehicle lane, the specific steps are as follows: (1) Clean the construction pavement to ensure that the surface of the pavement foundation is flat, dry, and free of debris. For uneven places, fill and correct them with sand and soil; (2) Lay an impermeable composite geotextile on the pavement foundation and fix it with rivets; (3) Spread 7 cm thick crushed stone on the impermeable composite geotextile, then install drain pipes, build overflow rainwater inlets, and at the same time install d300 reinforced concrete socket pipes and connect them to the municipal rainwater pipe network to form a complete pipeline system; finally, spread another 8 cm thick crushed stone; (4)Prepare the drainage base course material according to the formula and preparation method described in Example 3, and then spread the drainage base course material on the surface of the moist crushed stone layer for initial compaction. The thickness after initial compaction is 20.5 cm. After the initial compaction is completed, spread the drainage base course material again and then carry out final compaction. The thickness after final compaction is 32 cm. The methods of initial compaction and final compaction are as follows: Initial compaction: Static compaction for 2 passes, light vibration for 1 pass, strong vibration for 3 passes; speed: 1.5 km / h - 1.7 km / h, the general length of one-time rolling is 50 m - 80 m, and the overlapping of the staggered wheels during roller compaction should be 1 / 2; Final compaction: Static compaction for 1 pass, speed: 1.8 km / h - 2.2 km / h, and the overlapping of the staggered wheels during roller compaction should be 1 / 2; Among them, the drainage base course is paved and compacted in a segmented manner, that is, after paving and compacting a section of the road surface, then carry out the paving and compaction of the next section of the road surface. The length of each section of the road surface is 60 m; (5)Apply tack coat on the drainage base course, and then spread and compact a 6-cm-thick PAC-20C medium-sized permeable asphalt concrete layer; (6)Apply tack coat on the PAC-20C medium-sized permeable asphalt concrete layer, and then spread and compact a 4-cm-thick AC-13C fine-grained asphalt concrete layer; (7)Curing: After the construction is completed, moisten the permeable non-woven geotextile and then cover it on the road surface after the construction is completed, and then atomize and sprinkle water for normal curing to obtain a formed permeable road surface structure.

Claims

1. A phosphorus gypsum-based drainage base course based on construction waste, characterized in that: It includes 120 - 200 parts by weight of modified recycled aggregate, 0 - 80 parts by weight of modified natural aggregate, 8 - 8.5 parts by weight of cement, and 15 - 16 parts by weight of water. Among them, the modified recycled aggregate is composed of modified recycled aggregates with particle sizes of 0 - 5mm, 5 - 10mm, and 10 - 31.5mm in a mass ratio of 90 - 92:30 - 32:82 - 87.

2. The phosphogypsum-based drainage base course based on construction waste according to claim 1, wherein: The preparation method of the modified recycled aggregate includes the following steps: (1) Grind phosphogypsum and add water to make phosphogypsum slurry; (2) Place the recycled aggregate in the phosphogypsum slurry and mix and impregnate for 1 - 3h; (3) After the impregnation ends, filter and dry to obtain the modified recycled aggregate.

3. The phosphogypsum-based drainage base course based on construction waste according to claim 2, wherein: The water content in the phosphogypsum slurry in step (1) is 30 - 50%.

4. A phosphogypsum-based drainage base course based on construction waste according to claim 2, characterized in that: The recycled aggregate in step (2) is obtained by recycling and crushing waste concrete and bricks, and the particle size is 0 - 31.5mm.

5. A phosphogypsum-based drainage base course based on construction waste according to claim 1, characterized in that: The preparation method of the modified natural aggregate includes the following steps: (1) Mix phosphogypsum and activator evenly; (2) Mix the activated phosphogypsum and fly ash evenly to obtain a composite modifier; (3) Mix the composite modifier and natural aggregate evenly to obtain the modified natural aggregate.

6. The phosphogypsum-based drainage base course based on construction waste according to claim 5, characterized in that: The mass of the activator in step (1) is 1 - 15% of the phosphogypsum; the activator is any one of sodium bicarbonate, sodium hydroxide, and lime.

7. A phosphogypsum-based drainage base course based on construction waste according to claim 5, characterized in that: The mass ratio of the activated phosphogypsum to fly ash in step (2) is 3 - 5:5 - 7.

8. A phosphogypsum-based drainage base course based on construction waste according to claim 5, characterized in that: The mass of the composite modifier in step (3) is 18 - 25% of the mass of the natural aggregate; the natural aggregate is one or more of gravel, river sand, and manufactured sand.

9. A method for applying a phosphogypsum-based drainage base course based on construction waste as described in claim 8, characterized in that: It includes the following steps: (1) Clean and level the construction site; (2) Lay the anti-seepage cloth and install the drain pipe; (3) Mix the modified recycled aggregate, modified natural aggregate, cement, and water to make the raw material of the phosphogypsum-based drainage base course, spread and compact it; (4) Cure.

10. The application method according to claim 9, characterized in that: The paving thickness during compaction in step (3) is 50 - 80cm.

Images