An environment-friendly concrete and its preparation method

Abstract

The present application relates to the field of environmentally friendly high-performance building materials, and more specifically, it relates to an environmentally friendly concrete and a preparation method thereof. An environmentally friendly concrete, according to weight parts, includes the following raw materials: 140-160 parts of cement, 180-210 parts of admixtures, 600-700 parts of fine aggregate, 1000-1200 parts of coarse aggregate, 5-7 parts of admixtures, 140-160 parts of water, 10-20 parts of polyvinyl alcohol fibers, 20-30 parts of calcined attapulgite, and 100-200 parts of recycled aggregate. The environmentally friendly concrete provided in this application uses the environmentally friendly material of recycled aggregate, and overcomes the defects of recycled aggregate by cooperating with polyvinyl alcohol fibers, calcined attapulgite and recycled aggregate, thereby effectively improving the strength, fluidity and durability of environmentally friendly concrete.

Description

Technical Field

[0001] The present application relates to the field of environmentally friendly high-performance building materials, and more specifically, to an environmentally friendly concrete and a preparation method thereof. Background Art

[0002] With the increasing awareness of global environmental protection, the construction industry, as one of the main areas of resource consumption and waste generation, is facing tremendous environmental pressure. The traditional concrete production method relies on a large amount of natural aggregates, such as river sand, mountain rocks, etc., which not only consumes a large amount of natural resources, but also produces waste in the production process, which has a serious impact on the environment. Environmentally friendly concrete refers to concrete produced with environmentally friendly materials and technologies. Its production process has little negative impact on the environment and has good performance. With the continuous improvement of society's requirements for environmental protection, the demand for environmentally friendly concrete is also growing. Among them, the use of recycled aggregates is an important technology in the production of environmentally friendly concrete.

[0003] Recycled aggregate refers to the aggregate obtained by recycling and processing waste generated by construction waste, road widening, demolition of old buildings and highway reconstruction, after crushing and screening. This kind of aggregate has the advantages of wide source, low cost and excellent environmental performance, so it has been widely used in concrete production.

[0004] However, during the crushing process, the internal parts of the recycled aggregates will be damaged to varying degrees, resulting in many tiny cracks and irregular fragments. After being crushed, the recycled aggregates have irregular shapes and uneven surfaces, which leads to more voids or defects in the concrete using these recycled aggregates, reducing the overall strength of the concrete. Therefore, there is still room for improvement. Summary of the invention

[0005] In order to improve the performance of environmentally friendly concrete, the present application provides an environmentally friendly concrete and a preparation method thereof.

[0006] In the first aspect, the present application provides an environmentally friendly concrete, which adopts the following technical solution:

[0007] An environmentally friendly concrete comprises the following raw materials in parts by weight: 140-160 parts of cement, 180-210 parts of admixture, 600-700 parts of fine aggregate, 1000-1200 parts of coarse aggregate, 5-7 parts of admixture, 140-160 parts of water, 10-20 parts of polyvinyl alcohol fiber, 20-30 parts of calcined attapulgite, and 100-200 parts of recycled aggregate.

[0008] As a kind of polymer fiber, polyvinyl alcohol fiber has good toughness and tensile strength. Adding polyvinyl alcohol fiber to concrete can effectively improve the crack resistance and durability of concrete. At the same time, the network structure of polyvinyl alcohol fiber can increase the bonding force of concrete, making the concrete more compact. After high-temperature calcination, the surface of calcined attapulgite becomes uneven, with a large specific surface area and excellent adsorption capacity. This characteristic enables calcined attapulgite to well adsorb fine recycled aggregates and impurities in concrete, improving the purity and strength of concrete.

[0009] With the combined action of polyvinyl alcohol fiber and calcined attapulgite, the two are intertwined in concrete, forming a unique network structure. This structure can not only enhance the tensile strength and crack resistance of concrete, but also improve the density and durability of concrete. The combination of the adsorption capacity of calcined attapulgite and the network structure of polyvinyl alcohol fiber can be embedded into the cracks of recycled aggregates to fill the cracks and improve the density of the aggregates. At the same time, calcined attapulgite can also adsorb fine recycled aggregates, reduce the voids between aggregates, and further improve the density and strength of concrete. Moreover, when calcined attapulgite adsorbs on the surface of large recycled aggregates and fills the micro-cracks of recycled aggregates, due to the presence of polyvinyl alcohol fiber, the connection strength between adjacent filled calcined attapulgite can be enhanced, making the whole recycled aggregate better in integrity and the calcined attapulgite not easy to detach from the recycled aggregate.

[0010] During the concrete preparation process, calcined attapulgite reacts with water, absorbs water and becomes thick and expands, forming a gel-like substance on the surface and cracks of recycled aggregates. The interpenetrating support of polyvinyl alcohol fiber makes the gel-like substance more stable. This gel-like substance can further fill the voids between aggregates, enhance the bonding force and density of concrete. At the same time, it can also make the shape of recycled aggregates regular, reduce the friction and collision between aggregates, thereby improving the fluidity and workability of concrete.

[0011] Through a series of special combinations of polyvinyl alcohol fiber, calcined attapulgite and recycled aggregates, the defects of low performance of concrete using recycled aggregates caused by the irregular shape and uneven surface of recycled aggregates are overcome, effectively improving the strength and durability of concrete, and realizing the concept of environmental protection and reuse.

[0012] Preferably, by weight, the polyvinyl alcohol fiber is 14 - 18 parts, the calcined attapulgite is 25 - 30 parts, and the recycled aggregate is 130 - 160 parts.

[0013] By adopting the above technical scheme, the weight matching relationship of polyvinyl alcohol fiber, calcined attapulgite and recycled aggregate is further defined, making the combination of the three more harmonious, which is beneficial to filling the cracks of recycled aggregates and improving their appearance.

[0014] Preferably, the preparation of the calcined attapulgite clay comprises the following steps: calcining the attapulgite clay at 400 - 450 °C for 1 - 2 h, and taking it out to obtain the calcined attapulgite clay.

[0015] By adopting the above technical solution, the calcination temperature and time of the attapulgite clay are further defined. Under this condition, the generated calcined attapulgite clay has better activity and can have a better cooperation effect with polyvinyl alcohol fibers and recycled aggregates.

[0016] Preferably, the preparation of the calcined attapulgite clay comprises the following steps:

[0017] Step 1: Calcining the attapulgite clay at 400 - 450 °C for 1 - 2 h, and taking it out to obtain the calcined product;

[0018] Step 2: Immersing the calcined product in an ammonium sulfate solution with a concentration of 0.3 - 0.8 mol / L for 1 - 2 h, and after separation, obtaining the calcined attapulgite clay.

[0019] By adopting the above technical solution, the addition of ammonium sulfate enhances the cation exchangeability on the surface of the attapulgite clay. This is because the ammonium ions (NH 4+ ) in ammonium sulfate have similar charges and ionic radii to the cations in the attapulgite clay, so they are prone to exchange with each other. Through this exchange process, the adsorption capacity of the calcined attapulgite clay for cations such as calcium ions and potassium ions is improved. When these ions come into contact with the calcined attapulgite clay, they are more likely to exchange with the cations in the attapulgite clay and thus be adsorbed on the surface or inside the pores of the attapulgite clay, enhancing the connection effect, and further improving the microscopic structure of the concrete and the later strength and durability of the concrete.

[0020] Preferably, the ratio of the ammonium sulfate solution to the calcined product is 15 - 25 mL / g.

[0021] Preferably, before calcining the attapulgite clay, soak it in water for 2 - 4 h.

[0022] There may be some impurities in the attapulgite clay, and the pores may also be blocked. By adopting the above technical solution, soaking the attapulgite clay in water can remove some impurities, making it more fully contact with the ammonium sulfate solution subsequently.

[0023] Preferably, the particle size of the calcined attapulgite clay is 25 - 75 μm.

[0024] By adopting the above technical solution, the particle size of the calcined attapulgite clay is further optimized. At this particle size, it can better fill the cracks on the surface of the recycled aggregates.

[0025] Preferably, the particle size of the recycled aggregate is 0.5 - 1.5 mm.

[0026] In a second aspect, the present application provides a method for preparing an environmentally friendly concrete, adopting the following technical solution:

[0027] A method for preparing an environmentally friendly concrete includes the following steps:

[0028] Step a: Mix the calcined attapulgite clay, polyvinyl alcohol fiber, and recycled aggregate evenly under the condition of 1500 - 2000 r / min to obtain a mixture.

[0029] Step b: Mix the mixture with admixtures and cement evenly to obtain a first mixture.

[0030] Step c: Mix water with the first mixture evenly to obtain a second mixture.

[0031] Step d: Mix the second mixture with fine aggregate, coarse aggregate, and additives evenly to obtain environmentally friendly concrete.

[0032] By adopting the above technical solution, the calcined attapulgite clay, polyvinyl alcohol fiber, and recycled aggregate are pre - mixed at a higher rotation speed, promoting the firm interweaving of the calcined attapulgite clay and polyvinyl alcohol fiber and their adsorption and embedding onto the recycled aggregate, which is beneficial for subsequent cooperation with raw materials such as cement and water.

[0033] In summary, the present application has the following beneficial effects:

[0034] 1. With the combined action of polyvinyl alcohol fiber and calcined attapulgite clay, the two interweave with each other in the concrete, forming a unique network structure, which can enhance the strength and crack resistance of the concrete, and improve the density and durability of the concrete.

[0035] 2. The combination of calcined attapulgite clay and polyvinyl alcohol fiber can enhance the ability to embed into the cracks of the recycled aggregate, fill the cracks, and improve the density of the aggregate; reacting with water, it can also absorb water and become thick and expand, forming a gel - like substance on the surface and cracks of the recycled aggregate, improving the irregular shape of the recycled aggregate, and the interpenetrating support of the polyvinyl alcohol fiber makes the gel - like substance more stable, thus enhancing the performance of the concrete.

[0036] 3. The method of the present application pre - mixes the calcined attapulgite clay, polyvinyl alcohol fiber, and recycled aggregate at a higher rotation speed, promoting the firm interweaving of the calcined attapulgite clay and polyvinyl alcohol fiber and their adsorption and embedding onto the recycled aggregate, which is beneficial for subsequent cooperation with raw materials such as cement and water. Specific embodiments

[0037] The following further elaborates on the present application in conjunction with embodiments.

[0038] The raw materials used in the following examples and comparative examples are all commercially available products.

[0039] Preparation Example

[0040] Preparation Example 1

[0041] A kind of calcined attapulgite, the preparation includes the following steps:

[0042] Step 1: Immerse the attapulgite in clear water for 3 h, take it out and dry it to constant weight.

[0043] Step 2: Place the attapulgite in a muffle furnace and calcine it at 425 °C for 1.5 h, take it out to obtain the calcined product.

[0044] Step 3: Immerse the calcined product in a 0.5 mol / L ammonium sulfate solution for 1.5 h, and the ratio of the ammonium sulfate solution to the calcined product is 18 mL / g.

[0045] After the immersion is completed, perform solid-liquid separation, wash the solid part with clear water, and then dry it to constant weight to obtain the calcined attapulgite.

[0046] The attapulgite in this preparation example is commercially available and purchased from Baolei Mineral Products Co., Ltd., Lingshou County.

[0047] Preparation Example 2

[0048] A kind of calcined attapulgite, the preparation includes the following steps:

[0049] Step 1: Immerse the attapulgite in clear water for 2 h, take it out and dry it to constant weight.

[0050] Step 2: Place the attapulgite in a muffle furnace and calcine it at 400 °C for 2 h, take it out to obtain the calcined product.

[0051] Step 3: Immerse the calcined product in a 0.3 mol / L ammonium sulfate solution for 2 h, and the ratio of the ammonium sulfate solution to the calcined product is 15 mL / g.

[0052] After the immersion is completed, perform solid-liquid separation, wash the solid part with clear water, and then dry it to constant weight to obtain the calcined attapulgite.

[0053] The attapulgite in this preparation example is commercially available and purchased from Baolei Mineral Products Co., Ltd., Lingshou County.

[0054] Preparation Example 3

[0055] A kind of calcined attapulgite, the preparation includes the following steps:

[0056] Step 1: Immerse the attapulgite in clear water for 4 h, take it out and dry it to constant weight.

[0057] Step 2: Place the attapulgite in a muffle furnace and calcine it at 450 °C for 1 h. After taking it out, the calcined product is obtained.

[0058] Step 3: Immerse the calcined product in a 0.8 mol / L ammonium sulfate solution for 1 h. The ratio of the ammonium sulfate solution to the calcined product is 25 mL / g.

[0059] Step 4: After the immersion is completed, perform solid-liquid separation. Wash the solid part with clear water and then dry it to constant weight to obtain calcined attapulgite.

[0060] The attapulgite in this preparation example is commercially available and purchased from Baolei Mineral Products Co., Ltd., Lingshou County.

[0061] Preparation Example 4

[0062] A kind of calcined attapulgite, different from Preparation Example 1 in that the ammonium sulfate solution in Step 3 is replaced with clear water.

[0063] Preparation Example 5

[0064] A kind of calcined attapulgite, different from Preparation Example 1 in that the concentration of the ammonium sulfate solution is 2 mol / L.

[0065] Examples

[0066] Example 1

[0067] An environment-friendly concrete, comprising the following raw materials: cement, admixture, fine aggregate, coarse aggregate, admixture, water, polyvinyl alcohol fiber, calcined attapulgite, recycled aggregate.

[0068] The cement is commercially available 42.5 Portland cement; the admixture is fly ash and blast furnace slag; the fine aggregate is commercially available manufactured sand; the coarse aggregate is commercially available crushed stone; the admixture is polycarboxylate water reducer; the polyvinyl alcohol fiber is commercially available, purchased from Taian Songze Composite Materials Co., Ltd. in this example, with a diameter of 0.2 mm and a length of 6 mm; the recycled aggregate is commercially available, purchased from Tianjin Xinying Technology Co., Ltd. in this example, with a particle size of 0.5 - 1.5 mm.

[0069] The calcined attapulgite is from Preparation Example 1 and is screened or ground to a particle size of 50 μm.

[0070] The specific dosages of each raw material are shown in Table 1.

[0071] This application also provides a preparation method of the environment-friendly concrete, comprising the following steps:

[0072] Step a: Mix the calcined attapulgite, polyvinyl alcohol fiber, and recycled aggregate at 1500 - 2000 r / min and stir until uniform to obtain a mixture.

[0073] Step b: Mix the mixture with admixtures and cement, and stir until uniform to obtain the first mixture.

[0074] Step c: Mix water with the first mixture, and stir until uniform to obtain the second mixture.

[0075] Step d: Mix the second mixture with fine aggregate, coarse aggregate, and admixture, and stir until uniform to obtain the environmentally friendly concrete.

[0076] Example 2

[0077] An environmentally friendly concrete, which is different from that of Example 1 in that

[0078] the calcined attapulgite clay is from Preparation Example 2 and is screened or ground to a particle size of 25 μm.

[0079] The specific dosages of each raw material are different, as shown in Table 1 for details.

[0080] Example 3

[0081] An environmentally friendly concrete, which is different from that of Example 1 in that

[0082] the calcined attapulgite clay is from Preparation Example 3 and is screened or ground to a particle size of 75 μm.

[0083] The specific dosages of each raw material are different, as shown in Table 1 for details.

[0084] Example 4

[0085] An environmentally friendly concrete, which is different from that of Example 1 in that the polyvinyl alcohol fiber is 14 kg, the calcined attapulgite clay is 25 kg, and the recycled aggregate is 230 kg.

[0086] Example 5

[0087] An environmentally friendly concrete, which is different from that of Example 1 in that the polyvinyl alcohol fiber is 18 kg, the calcined attapulgite clay is 30 kg, and the recycled aggregate is 260 kg.

[0088] Table 1

[0089]

[0090] Example 6

[0091] An environmentally friendly concrete, which is different from that of Example 1 in that the calcined attapulgite clay is from Preparation Example 4.

[0092] Example 7

[0093] An environmentally friendly concrete, which is different from that of Example 1 in that the calcined attapulgite clay is from Preparation Example 5.

[0094] Comparative Example

[0095] Comparative Example 1

[0096] An environmentally friendly concrete, which is different from that of Example 1 in that the polyvinyl alcohol fiber is replaced with polypropylene fiber of the same weight. The polypropylene fiber is commercially available and this comparative example is purchased from Tai'an Senyang Composite Materials Co., Ltd., with a length of 6 mm.

[0097] Comparative Example 2

[0098] An environmentally friendly concrete, which is different from that of Example 1 in that the calcined attapulgite is replaced with attapulgite of the same weight. The attapulgite is commercially available and is purchased from Baolei Mineral Products Co., Ltd., Lingshou County.

[0099] Comparative Example 3

[0100] An environmentally friendly concrete, which is different from that of Example 1 in that the polyvinyl alcohol fiber and the calcined attapulgite are omitted.

[0101] Comparative Example 4

[0102] An environmentally friendly concrete, which is different from that of Example 1 in that the polyvinyl alcohol fiber is 26 kg and the calcined attapulgite is 15 kg.

[0103] Performance Detection Test

[0104] 1. Compressive strength: The 28-day compressive strength of the environmentally friendly concretes of Examples 1-7 and Comparative Examples 1-4 was detected in accordance with the Standard for Test Methods of Physical and Mechanical Properties of Concrete (GB / T50081-2019), and the results were recorded in Table 2.

[0105] 2. Fluidity: The fluidity of the environmentally friendly concretes of Examples 1-7 and Comparative Examples 1-4 was detected in accordance with the Standard for Test Methods of Properties of Ordinary Concrete Mixtures (GB / T50080-2002), and the slump results were recorded in Table 2.

[0106] 3. Durability: The chloride ion penetration resistance of the environmentally friendly concretes of Examples 1-7 and Comparative Examples 1-4 was detected by the RCM method in accordance with the Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete (GB / T50082-2009), and the chloride ion diffusion coefficient results were recorded in Table 2.

[0107] Table 2

[0108]

[0109] Comparative Examples 1 and 2 are concretes prepared by replacing polyvinyl alcohol fibers and calcined attapulgite with other raw materials on the basis of Example 1. Comparative Example 3 is prepared by omitting polyvinyl alcohol fibers and calcined attapulgite simultaneously on the basis of Example 1. Comparative Example 4 is prepared by keeping the recycled aggregate unchanged on the basis of Example 1 and changing the dosage combination effect of polyvinyl alcohol fibers, calcined attapulgite and it.

[0110] According to the test data in Table 2, the compressive strengths of Comparative Examples 1-4 all have varying degrees of difference from the concrete of Example 1, and the compressive strengths of Comparative Examples 1-4 are lower than that of Example 1; it can be seen from the slump data that the fluidity of the concrete in Comparative Examples 1-4 is also significantly inferior to that of Example 1; in terms of the chloride ion diffusion coefficient comparison, the chloride ion diffusion coefficients of Comparative Examples 1-4 are higher than that of Example 1, and the durability is poor. It shows that there is a special cooperation effect among polyvinyl alcohol fibers, calcined attapulgite and recycled aggregate. Arbitrarily changing the raw materials or destroying the dosage combination relationship will prevent the formation of a special structure and cannot alleviate the influence of the recycled aggregate itself on the concrete, thereby resulting in poor concrete performance.

[0111] Example 6 is prepared without using ammonium sulfate solution to soak the calcined product on the basis of Example 1. Example 7 is prepared by using an ammonium sulfate solution with too high a concentration to soak the calcined product on the basis of Example 1. The concretes prepared in Examples 6 and 7 have a significant decrease in all aspects, especially in terms of durability. It shows that only by using ammonium sulfate solution and limiting its concentration to treat the calcined product can a proper reaction occur with attapulgite to form calcined attapulgite with a special structure.

[0112] This specific embodiment is only an interpretation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. An environmentally friendly concrete, characterized in that: According to weight proportions, the raw materials include: 140-160 parts of cement, 180-210 parts of admixture, 600-700 parts of fine aggregate, 1000-1200 parts of coarse aggregate, 5-7 parts of admixture, 140-160 parts of water, 14-18 parts of polyvinyl alcohol fiber, 25-30 parts of calcined attapulgite, and 130-160 parts of recycled aggregate; The preparation of the calcined attapulgite comprises the following steps: Step 1: calcining attapulgite at 400-450° C. for 1-2 hours, and obtaining a calcined product; Step 2: Soak the calcined product in a 0.3-0.8 mol / L ammonium sulfate solution for 1-2 hours, and obtain calcined attapulgite after separation.

2. The environmentally friendly concrete according to claim 1, characterized in that: The ratio of the ammonium sulfate solution to the calcined product is 15-25 mL / g.

3. The environmentally friendly concrete according to claim 1, characterized in that: Before calcining the attapulgite, it is soaked in water for 2-4 hours.

4. The environmentally friendly concrete according to claim 1, characterized in that: The particle size of the calcined attapulgite is 25-75 μm.

5. The environmentally friendly concrete according to claim 1, characterized in that: The particle size of the recycled aggregate is 0.5-1.5 mm.

6. A method for preparing the environmentally friendly concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step a: mixing calcined attapulgite, polyvinyl alcohol fiber and recycled aggregate uniformly at 1500-2000 r / min to obtain a mixture; Step b: mixing the mixture, admixture and cement until uniform to obtain a first mixture; Step c: mixing water and the first mixture until uniform, to obtain a second mixture; Step d: The second mixture is mixed with fine aggregate, coarse aggregate and admixture until they are uniformly mixed to obtain environmentally friendly concrete.

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