Vegetation type pervious concrete, preparation method thereof and vegetation pervious concrete composite structure body

Abstract

The invention belongs to the field of building materials, and relates to vegetation type pervious concrete, a preparation method thereof and a vegetation pervious concrete composite structural body. The vegetation type pervious concrete is prepared from the following components in parts by mass: 90 to 100 parts of cement, 500 to 600 parts of coarse aggregate and 4 to 15 parts of pretreated coffee grounds. The pretreated coffee grounds are obtained by washing coffee grounds, drying the coffee grounds to constant weight and then enabling the water content of the coffee grounds to be 75-85%. By doping the pretreated coffee grounds, the alkalinity of the concrete is effectively reduced, and the plant growth environment can be improved. Coffee grounds are complete in porous structure, the water retention and release capacity can be improved, and the water supply period is prolonged. In addition, the coffee grounds are rich in organic matters and nutrient elements, can continuously release nutrients, and support plant growth. The water content of the coffee grounds is 75-85%, so that the coffee grounds can be prevented from fighting for cement hydration water, and normal hydration and strength development of the concrete are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a plant-growing type of water-permeable concrete, a preparation method thereof and a plant-growing type of water-permeable concrete composite structure. BACKGROUND

[0002] Under the background of the accelerating urbanization process, ecological environment protection and sustainable development have become important goals of urban construction. As an ecological building material with both water permeability and plant growth support ability, the plant-growing type of water-permeable concrete is widely used in urban roads, slope protection engineering, and sponge city construction. Traditional plant-growing type of water-permeable concrete is mainly prepared by using cement, coarse aggregate and other materials, and has certain water permeability. However, there are still many problems in the practical application of the plant-growing type of water-permeable concrete. First, the alkalinity of the concrete matrix is strong, which is not conducive to the germination of most plant seeds and the growth of root systems. Second, although the plant-growing type of water-permeable concrete has a pore structure, its water retention capacity is poor, and water is easily lost quickly, resulting in unstable water supply for plant growth. Third, it lacks organic matter and nutrients, and cannot provide sustained nutrient support for plants, affecting vegetation coverage and long-term ecological stability.

[0003] In order to improve the above problems, in recent years, researchers have tried to introduce various types of organic waste as functional additives into the water-permeable concrete system. Among them, coffee grounds, as a widely available and organic-rich household waste, have attracted attention due to their porous structure, weak acidity, and the presence of nitrogen, phosphorus, potassium and other plant nutrients.

[0004] The patent application with publication number CN109608121A proposes a plant-growing type of sand-free macroporous concrete, but it uses fermented coffee grounds and a complex plant substrate infiltration process, which is complicated and costly. The patent application with publication number CN114349379A discloses a modified coffee ground water-permeable concrete, but it mainly focuses on heavy metal adsorption performance and does not solve the problem of optimizing the plant growth environment. In addition, some studies attempt to directly mix dry coffee grounds into the concrete mixture, but due to the strong water absorption and hydrophilicity of coffee grounds, a large amount of free water is quickly absorbed during the mixing process, seriously interfering with the normal hydration of cement, resulting in decreased workability and strength of the concrete, or even failure to form.

[0005] Therefore, it is necessary to provide a preparation method of a plant-growing type of water-permeable concrete that can effectively utilize the advantages of coffee grounds in water retention, nutrient release and pH adjustment, while avoiding negative effects on the hydration process of the concrete. SUMMARY

[0006] (I) Technical problems to be solved

[0007] In view of the above technical problems, in order to solve the problems of poor water retention, strong alkalinity and lack of nutrients of the existing vegetation type pervious concrete, the application provides a vegetation type pervious concrete, a preparation method thereof and a vegetation type pervious concrete composite structure.

[0008] (II) Technical solutions

[0009] In order to achieve the above-mentioned purposes, the main technical solutions adopted by the application include:

[0010] In a first aspect, the application provides a vegetation type pervious concrete, which comprises 90-100 parts of cement, 500-600 parts of coarse aggregate and 4-15 parts of pretreated coffee grounds in terms of mass fraction.

[0011] The pretreated coffee grounds are obtained by washing coffee grounds, drying to constant weight, and then making the moisture content 75-85%.

[0012] The vegetation type pervious concrete as described above, preferably, the cement is any one of Portland cement, slag Portland cement or composite Portland cement.

[0013] The coarse aggregate is limestone, gravel, granite or recycled aggregate.

[0014] The vegetation type pervious concrete as described above, preferably, the pretreated coffee grounds are obtained by soaking the coffee grounds dried to constant weight in water to make the moisture content >90%, and then dehydrating to a moisture content of 75-85%.

[0015] The vegetation type pervious concrete as described above, preferably, in the coarse aggregate, the particles with a particle size of 19-26.5 mm account for 30-40% of the weight of the coarse aggregate, the particles with a particle size of 16-19 mm account for 30-40% of the weight of the coarse aggregate, and the particles with a particle size of 10-16 mm account for 20-30% of the weight of the coarse aggregate.

[0016] In a second aspect, the application provides a preparation method of the above-mentioned vegetation type pervious concrete, which comprises the following steps:

[0017] S1: water is added to the coarse aggregate and cement, after stirring, pretreated coffee grounds and water are added, and continuous stirring is performed to obtain a concrete mixture;

[0018] S2: the concrete mixture is placed in a mold, and artificial vibration and static pressure forming are sequentially performed to obtain a test piece;

[0019] S3: the test piece obtained in step S2 is first subjected to natural curing, then subjected to steam curing, and then subjected to standard curing for 28 days to obtain a vegetation type pervious concrete.

[0020] Preferably, in step S1, the total amount of water added in two times is 25-35% of the mass of cement, wherein the first added water is 35-45% of the total amount of water, and the second added water is 55-65% of the total amount of water.

[0021] Preferably, in step S3, the natural curing time is 24-48h, the steam curing time is 10-12h, the temperature of standard curing is 20±3℃, the relative humidity is ≥95%, and the distance between the test pieces during curing is 30-50mm.

[0022] In a third aspect, the present application further provides a vegetation water-permeable concrete composite structure, comprising a vegetation water-permeable concrete matrix, a vegetation matrix, and a slope grass plant seed; the slope grass plant seed is selected from any one or several of the following: ryegrass, high wool, and alkali grass.

[0023] The vegetation water-permeable concrete matrix has a connected pore structure inside, the plant matrix is filled in the pore structure, and the slope grass plant seed is scattered on the surface of the concrete.

[0024] The vegetation water-permeable concrete matrix is prepared by the above-mentioned vegetation water-permeable concrete or the vegetation water-permeable concrete prepared by the above-mentioned preparation method.

[0025] Preferably, in the vegetation water-permeable concrete composite structure, the vegetation matrix comprises the slope grass plant seed, loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash, and ferrous sulfate; the slope grass plant seed is selected from any one or several of the following: ryegrass, high wool, and alkali grass.

[0026] The mass ratio of loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash, and ferrous sulfate is (55-65):(25-30):(2-3):(2-3):(3-7):(0.8-1.5):(0.8-1.5).

[0027] Preferably, in the vegetation water-permeable concrete composite structure, the scattering density of the slope grass plant seed is 50-70g / m 2 .

[0028] (III) Beneficial effects

[0029] First, the coffee grounds mixed in the vegetation water-permeable concrete of the present application have natural weak acidity, which can neutralize alkaline substances in the concrete, reduce the alkalinity of the pore liquid, alleviate the inhibition of high-alkali environment on the germination of plant seeds and the development of root systems, and significantly improve the survival rate of vegetation and ecological stability.

[0030] Secondly, the coffee grounds used by the present application are washed and dried, so that the internal micropore and channel structure is completely retained and not damaged, which can significantly improve the water retention and release capacity of the concrete. The complete porous structure of the coffee grounds can form a stable internal water storage network in the concrete, which can adsorb and hold a large amount of water and slowly release it when the environment is dry, achieving a dynamic balance of water absorption-storage-release, thereby prolonging the supply cycle of water available to plants and improving the drought resistance of the plant-growing system.

[0031] Thirdly, the pretreated coffee grounds are rich in organic matter and nutrients such as nitrogen, phosphorus and potassium, which can provide basic nutrient support for plant growth. During the use of the concrete, these nutrients can gradually migrate out with the water, providing sustained nutrient supply for plant seeds and root systems attached to the pore surface, reducing the dependence on external fertilization, and enhancing the self-sustaining ability of the ecological system.

[0032] Fourthly, due to the strong hydrophilicity and porous structure of the coffee grounds, if they are directly mixed into the concrete in a dry state, they will instantly adsorb a large amount of free water at the beginning of stirring, forming strong physical water absorption competition. The hydration reaction of cement is a slow chemical process, and its water consumption rate is much lower than the physical adsorption rate of coffee grounds, resulting in that even if the total water amount is added according to the design ratio, most of the water is still quickly locked by the coffee grounds and cannot effectively participate in the cement hydration, thereby causing the paste to dry too early, the workability to decrease, the hydration to be insufficient, and finally affecting the strength development and structural stability of the concrete. The present application adjusts the coffee grounds to a high water content of 75-85% in advance, so that the water absorption process is basically completed before the cement hydration, thereby avoiding the competition for free water in the cement hydration process, ensuring the normal progress of the cement hydration reaction, and being beneficial to the formation of early strength and the stability of long-term structural performance of the concrete. DETAILED DESCRIPTION

[0033] In order to better explain the present application and facilitate understanding, the present application will be described in detail below in conjunction with specific embodiments.

[0034] The present application provides a plant-growing type water-permeable concrete, which comprises 90-100 parts of cement, 500-600 parts of coarse aggregate, and 4-15 parts of pretreated coffee grounds in terms of mass fraction. The pretreated coffee grounds used by the present application are obtained by washing the coffee grounds, drying them to a constant weight, and then adjusting the water content to 75-85%.

[0035] Among them, the cement can provide cementation to form the basic framework of the concrete. The coarse aggregate is the main volume part of the concrete, which is used to provide strength and water permeability. The pretreated coffee grounds are an important component for water retention and release, pH adjustment, and nutrient provision.

[0036] The coffee grounds have natural weak acidity, which can neutralize the alkaline substances in the concrete, reduce the alkalinity of the pore solution, alleviate the inhibition of high-alkali environment on the seed germination and root development of plants, and significantly improve the survival rate and ecological stability of vegetation.

[0037] The internal micropore and channel structure of the coffee grounds are completely retained and not damaged after washing and drying treatment, which can significantly improve the water retention and release capacity of the concrete. Specifically, the complete porous structure of the coffee grounds can form a stable internal water storage network in the concrete, which can adsorb and hold a large amount of water and slowly release the water when the environment is dry, thereby prolonging the supply cycle of water available to plants and improving the drought resistance of the vegetation system.

[0038] The coffee grounds are rich in organic matter and nutrients such as nitrogen, phosphorus and potassium, which can provide basic nutrient support for plant growth. During the use of the concrete, these nutrients can gradually migrate out with the water, providing sustained nutrient supply for plant seeds and roots and enhancing the self-maintenance ability of the ecological system.

[0039] In addition, due to the strong hydrophilicity and porous structure of the coffee grounds, if they are directly mixed into the concrete in a dry state, they will instantly adsorb a large amount of free water at the beginning of stirring, forming strong physical water absorption competition. The hydration reaction of cement is a slow chemical process, and its water consumption rate is much lower than the physical adsorption rate of coffee grounds, resulting in that even if the total water amount is added according to the design ratio, most of the water is still locked by coffee grounds quickly and cannot effectively participate in the hydration of cement, thereby causing the paste to dry too early, the workability to decrease, the hydration to be insufficient, and finally affecting the strength development and structural stability of the concrete. In order to solve this problem, the coffee grounds are adjusted to a high water content of 75-85% in advance, so that the water absorption process is basically completed before the hydration of cement, thereby avoiding the competition for free water in the hydration process of cement and ensuring the normal progress of the hydration reaction of cement, which is beneficial to the formation of early strength of the concrete and the stability of long-term structural performance.

[0040] Preferably, the cement used in the application can be any one of Portland cement, slag Portland cement or composite Portland cement, preferably Portland cement. The coarse aggregate can be any one of limestone, gravel, granite or recycled aggregate.

[0041] Further preferably, the preparation method of the pretreated coffee grounds is as follows: the coffee grounds are washed multiple times to remove impurities, then dried to constant weight at 60-80℃, then soaked in water to have a water content of >90%, preferably 100%, and then dehydrated at 60-80℃ to have a water content of 75-85%.

[0042] The pre-treatment method of the application is relatively mild, aiming to retain the natural porous structure of the coffee grounds, so that it can maintain good water retention and release capacity. If the drying temperature is too high, for example, continuously higher than 200℃, it will cause pyrolysis of the organic components of the coffee grounds, resulting in shrinkage, softening and even collapse of the natural pore structure, thereby significantly weakening its water retention and release performance as an internal curing material for concrete.

[0043] The coffee grounds with a moisture content of 75-85% can act as a micro-reservoir during the hardening process of the concrete. When the surrounding cement paste tends to dry, it slowly releases the water it holds, providing un-hydrated cement particles with the opportunity to continue reacting, thereby playing an internal curing role. This helps to reduce autogenous shrinkage cracks, improve density and long-term strength. If the moisture content is less than 75%, the coffee grounds still have a strong water absorption potential and will rob free water during mixing, resulting in insufficient water for cement hydration, insufficient hydration, and affecting early strength and durability.

[0044] If the moisture content is higher than 85%, the excess water will become additional free water in the system, exceeding the designed water-cement ratio (water to cement ratio), resulting in increased porosity and decreased density of the concrete, and after evaporation, it is easy to leave connected channels, weakening the structural strength and possibly affecting the durability. Therefore, 75-85% is the optimal moisture content range, which can balance water retention and release function and concrete structural performance.

[0045] Further preferably, in the coarse aggregate of the application, the particles with a particle size of 19-26.5mm account for 30-40% of the weight of the coarse aggregate, preferably 37.5%, the particles with a particle size of 16-19mm account for 30-40% of the weight of the coarse aggregate, preferably 37.5%, and the particles with a particle size of 10-16mm account for 20-30% of the weight of the coarse aggregate, preferably 25%.

[0046] The particles with a particle size of 19-26.5mm can provide larger voids to enhance water permeability. The particles with a particle size of 16-19mm are used to balance strength and water permeability. The particles with a particle size of 10-16mm are used to fill smaller voids to improve density. The application can ensure water permeability and provide sufficient structural strength through reasonable particle size matching.

[0047] The application also provides a preparation method of the above-mentioned vegetation water-permeable concrete, comprising the following steps:

[0048] S1: water is added to the coarse aggregate and cement, and after stirring, pre-treated coffee grounds and water are added, and the stirring is continued to obtain a concrete mixture.

[0049] S2: the concrete mixture is placed in a mold, and artificial vibration and static pressure forming are sequentially performed to obtain a test piece.

[0050] S3: first, the test piece obtained in step S2 is naturally cured at room temperature, then steam curing is carried out, and then standard curing is carried out until the 28-day age, to obtain the vegetation permeable concrete.

[0051] Preferably, in the above step S1, the total amount of water added twice is 25-35% of the mass of cement, wherein the first added water is 35-45% of the total water amount, and the second added water is 55-65% of the total water amount. The present application adopts staged gradient water adding, which can optimize the mixing process, the first added small amount of water is used for wetting the powder material, avoiding local clumping, and realizing preliminary dispersion. The second added remaining most water is used for fully mixing and fluidizing on the basis of uniformly wetting the material, which is conducive to improving the mixing efficiency, improving the slurry uniformity, enhancing the hydration reaction degree, and finally improving the compactness and strength after hardening.

[0052] The above step S2 adopts the combined molding mode of manual vibration + static pressure molding, first, the internal bubbles of the mixture are removed through manual vibration to promote the cement paste to uniformly wrap the aggregates, and then the static pressure molding is used to enhance the interlocking action between the aggregates to improve the overall compactness and compressive strength. The combined mode is particularly suitable for dry vegetation permeable concrete, which can not only ensure the pore connectivity to maintain the water permeability function, but also optimize the mechanical properties to realize the synergy of structure and ecological function.

[0053] Step S3 adopts a multi-stage curing system of natural curing-steam curing-standard curing, wherein the natural curing can prevent early water loss cracking, the steam curing can accelerate the early hydration of cement and shorten the demolding cycle, and the standard curing can ensure that the 28-day strength and durability meet the standards. The curing mode of the present application not only improves the production efficiency, but also fully adapts to the influence of pretreated coffee residue on the hydration process, and guarantees the stability of long-term performance of the concrete.

[0054] Preferably, in the above step S3, the natural curing time is 24-48h, the steam curing time is 10-12h, the temperature of standard curing is 20±3℃, the relative humidity is ≥95%, the spacing of the test piece during the curing process is 30-50mm, the steam curing temperature is 55-80℃, and the steam curing is divided into three stages of temperature rising-constant temperature-temperature falling, wherein the temperature rising and falling rate is 8-12℃ / h.

[0055] The present application also provides a vegetation permeable concrete composite structure, which comprises a vegetation permeable concrete matrix, a vegetation substrate, and a slope protection herbaceous plant seed. The vegetation permeable concrete matrix has a connected pore structure inside, the vegetation substrate is filled in the pore structure, and the slope protection herbaceous plant seed is scattered on the surface of the concrete. The vegetation permeable concrete matrix is prepared by the above vegetation permeable concrete. The scattering density of the slope protection herbaceous plant seed is 50-70g / m 2 .

[0056] The water-permeable concrete serves as a framework to provide mechanical strength and rainwater infiltration channels. The internal interconnected pores provide space for plant root growth and water transport, and the plant-growing substrate fills the pores to provide growth medium for plants. The water-permeable concrete composite structure can realize the integration of structure and ecology, and is suitable for slope protection, urban green space, and sponge city construction. The concrete matrix can ensure long-term stability, and the plant-growing substrate can ensure rapid vegetation establishment. Rainwater can infiltrate through the pores to reduce surface runoff and realize a virtuous cycle of water permeation, water storage, and plant utilization.

[0057] Preferably, the plant-growing substrate comprises loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash, and ferrous sulfate.

[0058] The slope-protection herbaceous plant seeds are selected from any one or several of rye grass, tall fescue (i.e., tall fescue), and alkali grass. The rye grass germinates rapidly to achieve early coverage, the tall fescue has developed root systems, is resistant to trampling and erosion, the alkali grass is resistant to saline-alkali and drought, and can achieve rapid seedling emergence, dense sod formation, and long-term ecological stability under different climate and soil conditions through mixed seeding.

[0059] The components in the plant-growing substrate have the following functions:

[0060] The loess, as the main component of the plant-growing substrate, serves as a framework support, has certain cohesiveness and water retention capacity, and can effectively prevent the substrate from being washed away by rainwater. In addition, the loess is widely available and low in cost, which is conducive to reducing the overall material cost. The loess can also provide plants with essential mineral elements such as silicon, potassium, and calcium, and is a basic component to ensure the stability and long-term performance of the substrate structure.

[0061] The nutrient soil is the main source of nutrients in the plant-growing substrate, and is usually made of humus soil or organic compost, rich in organic matter, humic acid, and available nutrients such as nitrogen, phosphorus, and potassium. Its function is to significantly improve the fertility of the substrate, promote seed germination and early growth of seedlings, shorten the vegetation establishment period, and construct a nutrient supply system of available + slow-release nutrients in cooperation with organic fertilizer to ensure the nutrient needs of plants in the early growth stage.

[0062] The perlite is a lightweight and porous structure formed by high-temperature expansion, and is mainly used to improve the air permeability of the substrate. Its closed pores do not absorb water, but can increase the number of large pores, effectively prevent the substrate from being hardened, promote plant root respiration, avoid root rot caused by water accumulation, especially under conditions of frequent rainfall or poor drainage. It also has important significance, and can reduce the weight of the overall substrate and the additional load on the concrete matrix.

[0063] Vermiculite is a kind of layered silicate mineral with strong water absorption and cation adsorption capacity. Its main function is to improve the water and fertilizer retention performance of the substrate, which can absorb a large amount of water and nutrient ions when wet, and slowly release them when dry, maintaining the water supply of plants under drought conditions, reducing irrigation frequency, and improving water resource utilization efficiency.

[0064] Organic fertilizer is used as a slow-release nutrient source to support long-term plant growth. It is composed of decomposed organic matter such as livestock and poultry manure, garden waste, etc., preferably fermented sheep manure, which can be gradually decomposed by microorganisms to continuously release nitrogen, phosphorus, potassium and trace elements, avoiding the risk of seedling burning caused by quick-acting chemical fertilizers. At the same time, organic fertilizer can help improve the structure of the substrate granules, enhance the air permeability and water retention, and achieve sustainable supply of nutrients to ensure the healthy growth of vegetation in the later stage.

[0065] Fly ash, as an industrial solid waste, is used to improve the physical properties of the substrate and realize resource utilization. Its micro-bead structure can fill fine pores, improve the compactness and anti-erosion of the substrate, and the active SiO2 and Al2O3 contained can cause weak pozzolanic reaction in alkaline environment, slightly enhancing the bonding force between concrete and substrate interface.

[0066] Ferrous sulfate is used to adjust the microenvironment of the substrate and supplement the essential iron elements for plants. Fe 2+ is a key component of chlorophyll synthesis, which is easily fixed and cannot be absorbed in alkaline or high calcium environment, leading to iron deficiency chlorosis in plants. By adding ferrous sulfate, the yellowing of ryegrass and other grass seeds can be effectively prevented, maintaining good green period and ornamental value.

[0067] The mass ratio of loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash and ferrous sulfate is (55-65):(25-30):(2-3):(2-3):(3-7):(0.8-1.5):(0.8-1.5).

[0068] Further, the method for preparing the vegetation substrate in the present application is as follows:

[0069] The required slope protection herbaceous plant seeds, loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash and ferrous sulfate are weighed according to the predetermined content, and water is added according to 1.8 times the total mass of the vegetation substrate. The loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash and ferrous sulfate are ground by a grinder before mixing. The ground vegetation substrate is mixed with water, and the water is poured into the pores of the concrete. In addition, during the actual planting process, a layer of soil can be spread on the surface of the concrete into which the vegetation substrate is poured, and then the seeds are sown.

[0070] Example 1

[0071] The embodiment provides a preparation method of the vegetation permeable concrete, and comprises the following steps:

[0072] S1: the coffee grounds are put into an oven after multiple washing, dried at 70 DEG C until constant weight, then the dried coffee grounds are soaked until saturated (water content is 100%), and then dehydrated at 70 DEG C until the water content is 80%, to obtain pretreated coffee grounds.

[0073] S2: the limestone and the ordinary Portland cement of P.042.5 are added into a stirrer, then the first water is added, stirred for 30s, then the pretreated coffee grounds and the second water are added, and stirring is continued for 1.5min, to obtain a concrete mixture. The total amount of the two times of added water is 30% of the cement mass, wherein the first time of added water is 40% of the total water, and the second time of added water is 60% of the total water. In the step, the particles with the particle size of 19-26.5mm account for 37.5% of the weight of the limestone, the particles with the particle size of 16-19mm account for 37.5% of the weight of the limestone, and the particles with the particle size of 10-16mm account for 25% of the weight of the limestone. In the step, 945 parts of cement, 5063.5 parts of limestone and 43.2 parts of pretreated coffee grounds are included.

[0074] S3: the concrete mixture is placed into a mold with the size of 150mm*150mm*150mm, and artificial vibration and static pressure forming are sequentially performed, to obtain a test piece.

[0075] S4: the test piece is naturally cured for 36h, then steam cured for 11h, and then standard cured under the condition of 22 DEG C and 95% relative humidity until 28 days of age, to obtain the vegetation permeable concrete. The distance between the test pieces in the curing process is 40mm.

[0076] In step S1, a standard vibration sieve machine of shock type developed by the Building Material Institute of China Academy of Building Research is used, the model is ZBSX92A, the vibration frequency is 221 times / min, the swing stroke is 25mm, the shock frequency is 147min, and the motor power is 0.37Kw. The limestone with different particle size ranges is obtained by screening according to the sieve hole size (mm).

[0077] Example 2

[0078] The embodiment provides a preparation method of the vegetation permeable concrete, and comprises the following steps:

[0079] S1: the coffee grounds are put into an oven after multiple washing, dried at 60 DEG C until constant weight, then the dried coffee grounds are soaked until the water content is 90%, and then dehydrated at 60 DEG C until the water content is 75%, to obtain pretreated coffee grounds.

[0080] S2: Add gravel and slag Portland cement into a mixer, then add first portion of water, stir for 30s, then add pretreated coffee grounds and second portion of water, continue to stir for 1.5min, to obtain a concrete mixture. The total amount of water added in two times is 25% of the mass of cement, wherein the first portion of water is 35% of the total amount of water, and the second portion of water is 65% of the total amount of water. In this step, the particles with a particle size of 19-26.5mm account for 30% of the weight of the gravel, the particles with a particle size of 16-19mm account for 40% of the weight of the gravel, and the particles with a particle size of 10-16mm account for 30% of the weight of the gravel. This step includes 90 parts of cement, 500 parts of gravel, and 4 parts of pretreated coffee grounds.

[0081] S3: Place the concrete mixture into a mold with a size of 150mmx150mmxl50mm, and sequentially perform manual vibration and static pressure forming to obtain a test piece.

[0082] S4: First, naturally cure the test piece for 24h, then steam cure for 10h, and then standard cure under the condition of 20℃ and relative humidity of 95% for 28 days of age, to obtain the vegetation permeable concrete. The distance between the test pieces during the curing process is 30mm.

[0083] In step S1, a standard vibration sieve machine with a model of ZBSX92A developed by the Building Materials Institute of China Academy of Building Science is used, the vibration frequency is 221 times / min, the swing stroke is 25mm, the shock frequency is 147min, and the motor power is 0.37Kw. The gravel with different particle size ranges is obtained by screening according to the sieve hole size (mm).

[0084] Example 3

[0085] The embodiment provides a preparation method of vegetation permeable concrete, including the following steps.

[0086] S1: After the coffee grounds are washed for multiple times, the coffee grounds are placed into an oven, dried at 80℃ until a constant weight is obtained, then the dried coffee grounds are soaked to have a water content of 95%, and then dehydrated at 80℃ until the water content is 85% to obtain pretreated coffee grounds.

[0087] S2: granite and composite portland cement were added into a mixer, then the first portion of water was added, after stirring for 30 s, the pretreated coffee grounds and the second portion of water were added, and stirring was continued for 1.5 min to obtain a concrete mixture. The total amount of water added in two portions was 35% of the mass of the cement, wherein the first portion of water was 45% of the total amount of water, and the second portion of water was 55% of the total amount of water. In this step, the particles with a particle size of 19-26.5 mm accounted for 40% of the weight of the granite, the particles with a particle size of 16-19 mm accounted for 30% of the weight of the granite, and the particles with a particle size of 10-16 mm accounted for 30% of the weight of the granite. This step included 100 parts of cement, 600 parts of granite, and 15 parts of pretreated coffee grounds.

[0088] S3: the concrete mixture was placed in a mold with a size of 150 mm x 150 mm x 150 mm, and manual vibration and static pressure forming were sequentially performed to obtain a test piece.

[0089] S4: the test piece was first naturally cured for 48 h, then steam cured for 12 h, and then standard cured at 23°C and a relative humidity of 98% for 28 days to obtain the vegetation permeable concrete. The distance between the test pieces during the curing process was 50 mm.

[0090] In step S1, a standard sieve shaking machine developed by the Building Materials Institute of China Academy of Building Research was used, the model was ZBSX92A, the vibration frequency was 221 times / min, the swing stroke was 25 mm, the shaking frequency was 147 min, and the motor power was 0.37 Kw. The granite with different particle size ranges was obtained by sieving according to the sieve hole size (mm).

[0091] Example 4

[0092] This example provides a preparation method of vegetation permeable concrete, which is different from example 1 in that the coarse aggregate is recycled aggregate, and in step S2, the particles with a particle size of 19-26.5 mm account for 40% of the weight of the limestone, the particles with a particle size of 16-19 mm account for 40% of the weight of the limestone, and the particles with a particle size of 10-16 mm account for 20% of the weight of the limestone.

[0093] Example 5

[0094] This example provides a preparation method of vegetation permeable concrete, which is different from example 1 in that 10 parts of pretreated coffee grounds are used in step S2.

[0095] Comparative Example 1

[0096] This comparative example provides a preparation method of vegetation permeable concrete, which is different from example 1 in that in step S1, the coffee grounds are washed multiple times and then placed in an oven, dried at 60°C to constant weight to obtain pretreated coffee grounds.

[0097] In step S2, after stirring for 30 s, the pretreated coffee grounds, the second portion of water, and the third portion of water are added, the mass of the third portion of water being equal to the mass of the moisture contained in the pretreated coffee grounds in Example 1.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a phytogenic pervious concrete, which differs from Example 1 in that the moisture content of the pretreated coffee grounds in step S1 is 60%.

[0100] Comparative Example 3

[0101] This comparative example provides a method for preparing a phytogenic pervious concrete, which differs from Example 1 in that the moisture content of the pretreated coffee grounds in step S1 is 92%.

[0102] Comparative Example 4

[0103] This comparative example provides a method for preparing a phytogenic pervious concrete, which differs from Example 1 in that, before being soaked, the coffee grounds are subjected to a heating treatment at 400°C under anaerobic conditions.

[0104] Comparative Example 5

[0105] This comparative example provides a method for preparing a phytogenic pervious concrete, which differs from Example 1 in that no coffee grounds are added.

[0106] Performance test:

[0107] ①: After the test pieces of Examples 1-5 and Comparative Examples 1-5 are cured to the specified age, their mass m1 under standard curing conditions is measured. Then the test pieces are placed in an oven at 60°C for 24 h and taken out, and their oven-dried mass m2 is measured. The natural water absorption A1 of the phytogenic concrete is calculated, the calculation method being as follows:

[0108] Wherein, A1 is the natural water absorption of the phytogenic concrete, the unit being %;

[0109] In the formula: A1 is the natural water absorption of the phytogenic concrete, the unit being %;

[0110] m1 is the mass of the test piece under standard curing conditions, the unit being g;

[0111] m2 is the oven-dried mass of the test piece, the unit being g.

[0112] Table 1 is a statistical table of the natural water absorption of the phytogenic pervious concrete prepared in Examples 1-5 and Comparative Examples 1-5.

[0113] Table 1 is a statistical table of the natural water absorption of the phytogenic pervious concrete prepared in Examples 1-5 and Comparative Examples 1-5.

[0114]

[0115] 2: The porosities of the test pieces of Examples 1-5 and Comparative Examples 1-5 were tested to obtain Table 2.

[0116] Table 2: Statistics of the porosities of the plant-growing water-permeable concrete prepared in Examples 1-5 and Comparative Examples 1-5

[0117]

[0118] Too low porosity will deprive the physical space required for plant root growth, the water and gas balance required for life, and the nutrient circulation channel, resulting in the growth stagnation or even death of plants due to limited root development, suffocation or malnutrition. As can be seen from Table 2, the concrete test pieces of Examples 1-5 have higher porosities than Comparative Examples 1-4, which are more conducive to plant root growth. Although Comparative Example 5 without the addition of coffee grounds has a higher porosity, it is alkaline as a whole, cannot provide nutrients, and has poor water retention and release performance, which is still not conducive to plant root growth.

[0119] 3: The test pieces of Examples 1-5 and Comparative Examples 1-5 were completely soaked in distilled water at 20℃±1℃ for 24h to simulate the natural water absorption process of the concrete, so as to unify the starting point of water absorption. After taking out, the surface water was wiped off, and the saturated mass m3 of the concrete was weighed.

[0120] The saturated test pieces were placed in a constant temperature and humidity chamber, where the temperature was 23℃±2℃ and the relative humidity was 30%±5%. At the 3rd, 12th, 24th and 48th hours of placement, the masses m t at each time point were weighed, the water retention rates R t at each time point were calculated, R t =[(m t -m2) / (m3-m2)]x100%, and Table 3 was obtained, wherein the higher the R t value, the better the water retention and release performance of the concrete.

[0121] Table 3: Statistics of the water retention rates of the plant-growing water-permeable concrete prepared in Examples 1-5 and Comparative Examples 1-5

[0122]

[0123] As can be seen from Table 1 and Table 3, the concrete test pieces of Examples 1-5 have better water retention and release capacity than Comparative Examples 1-5.

[0124] (4) In the test pieces prepared in Examples 1-5 and Comparative Examples 1-5, three parallel test pieces were taken from each example / comparative example. Ryegrass seeds, alkali grass seeds, tall fescue seeds with a purity of ≥95% were selected. The loess: nutrient soil: perlite: vermiculite: organic fertilizer: fly ash: ferrous sulfate were mixed in a mass ratio of 60:27:2.5:2.5:5:1:1 to obtain a vegetation substrate. The vegetation concrete test piece was placed horizontally, and then the vegetation substrate was mixed with an appropriate amount of water to form a slurry, which was used to fully fill the internal pores of each test piece. Then, on the surface of each test piece, 3 test pieces corresponding to each example and comparative example were uniformly sown with ryegrass, alkali grass or tall fescue seeds at a density of 60 g / m². After sowing, a layer of thin soil was covered on the surface of the seeds, and the seeds were slightly compacted to ensure that the seeds were in full contact with the substrate.

[0125] All the sown test pieces were placed in the same controllable greenhouse, and the environmental conditions were set as follows: day / night temperature 25°C / 18°C, relative humidity 60%, daily light 12h. A unified automatic spraying system was used for maintenance, and water was poured once a day, with consistent amount each time, to ensure that the substrate was moist but not waterlogged, without any additional fertilizer.

[0126] After a unified growth period of 45 days from the sowing date, data measurement was carried out. Ten well-grown plants were randomly selected on each test piece, and the vertical height from the substrate surface to the naturally stretched highest point of the leaf was measured with a tape measure, and the average value was calculated as the average maximum height of the grass seeds on the test piece, as shown in Table 4.

[0127] Table 4: Average maximum height of vegetation and water-permeable concrete of Examples 1-5 and Comparative Examples 1-5

[0128]

[0129] As can be seen from Table 4, the vegetation and water-permeable concrete prepared in Examples 1-5 can significantly promote the growth of plants compared to Comparative Examples 1-5, showing excellent ecological compatibility. Under the same maintenance conditions, the three types of slope protection grass plants in Examples 1-5 all grow vigorously, with average height significantly higher than all the comparative examples. The growth of plants in the comparative example group is generally severely inhibited, and the plants are short. In particular, the growth of plants in Comparative Example 4 and Comparative Example 5 is the worst, which directly proves that coffee grounds without proper pretreatment or completely missing the coffee grounds component cannot achieve the expected ecological function.

[0130] In addition, it should be noted that the concrete test piece of Comparative Example 1-3 is more difficult to form, and the compressive strength is significantly less than that of the concrete test piece of Example 1-5. In addition, the biochar made of coffee grounds is generally alkaline, which not only cannot neutralize the alkalinity of the concrete, but also makes the concrete more alkaline, which is not conducive to plant growth.

[0131] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A type of permeable concrete, characterized in that, By weight fraction, it includes 90-100 parts cement, 500-600 parts coarse aggregate, and 4-15 parts pretreated coffee grounds; The pretreated coffee grounds are obtained by washing coffee grounds, drying them to a constant weight, and then reducing their moisture content to 75-85%.

2. The vegetation-type permeable concrete according to claim 1, characterized in that, The cement is any one of silicate cement, slag silicate cement, or composite silicate cement. The coarse aggregate is limestone, gravel, granite, or recycled aggregate.

3. The vegetation-type permeable concrete according to claim 1, characterized in that, The pre-treated coffee grounds are obtained by soaking coffee grounds dried to constant weight in water to make their moisture content >90%, and then dehydrating them to a moisture content of 75-85%.

4. The vegetation-type permeable concrete according to claim 1, characterized in that, In the coarse aggregate, particles with a diameter of 19-26.5 mm account for 30-40% of the weight of the coarse aggregate, particles with a diameter of 16-19 mm account for 30-40% of the weight of the coarse aggregate, and particles with a diameter of 10-16 mm account for 20-30% of the weight of the coarse aggregate.

5. A method for preparing vegetated permeable concrete according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Add water to coarse aggregate and cement, stir, then add pretreated coffee grounds and water, continue stirring to obtain concrete mixture; S2: The concrete mixture is placed in a mold and then manually vibrated and statically pressed to obtain a specimen; S3: First, the specimens obtained in step S2 are naturally cured, then steam cured, and then standard cured for 28 days to obtain vegetation permeable concrete.

6. The preparation method according to claim 5, characterized in that, In step S1, the total amount of water added in the two additions is 25-35% of the cement mass, with the first addition being 35-45% of the total water volume and the second addition being 55-65% of the total water volume.

7. The preparation method according to claim 5, characterized in that, In step S3, the natural curing time is 24-48 hours, the steam curing time is 10-12 hours, the standard curing temperature is 20±3℃, the relative humidity is ≥95%, and the spacing between specimens during the curing process is 30-50 mm.

8. A plant-grown permeable concrete composite structure, characterized in that, It includes a permeable concrete substrate, a vegetation matrix, and seeds of slope protection herbaceous plants; the seeds of the slope protection herbaceous plants are selected from any one or more of ryegrass, tall wool, and alkali grass. The planted permeable concrete matrix has an interconnected pore structure inside, the plant matrix fills the pore structure, and the slope protection herbaceous plant seeds are sown on the concrete surface. The vegetation permeable concrete matrix is ​​prepared by the vegetation permeable concrete according to any one of claims 1-4 or by the preparation method according to any one of claims 5-7.

9. The vegetation-permeable concrete composite structure according to claim 8, characterized in that, The vegetation substrate includes loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash, and ferrous sulfate; The mass ratio of loess, nutrient soil, perlite, vermiculite, organic fertilizer, fly ash and ferrous sulfate is (55-65):(25-30):(2-3):(2-3):(3-7):(0.8-1.5):(0.8-1.5).

10. The vegetation-permeable concrete composite structure according to claim 8, characterized in that, The sowing density of the slope protection herbaceous plant seeds is 50-70 g / m². 2 .

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