Photovoltaic cast-in-place pile concrete taking composite activated chromium slag as admixture and preparation method of photovoltaic cast-in-place pile concrete

Abstract

The invention discloses photovoltaic cast-in-place pile concrete taking composite activated chromium slag as an admixture. The concrete is prepared from the following raw materials in parts by mass: 46 to 185 parts of activated chromium slag, 276 to 415 parts of P.O 42.5 cement, 140 to 175 parts of water, 512 to 542 parts of medium sand, 1206 to 1252 parts of stone and 4 to 9 parts of a water reducing agent. The preparation method of the active chromium slag comprises the following steps: performing microwave activation treatment on the chromium slag and an antidote, namely waste cane molasses, and then performing ball milling with solid Na2SiO3 for chemical activation to prepare the microwave-chemical composite activated chromium slag. The prepared concrete is high in compressive strength, the amount of consumed chromium slag is large, large-scale comprehensive utilization of the chromium slag is effectively achieved, and remarkable economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization and concrete materials, and particularly relates to photovoltaic cast-in-place pile concrete with composite activated chromium slag as an admixture and a preparation method thereof. Background Art

[0002] Chromium slag is metallurgical waste slag discharged during the production of chromium salts from chromite. The annual chromium slag discharge in my country reaches 600,000 tons. At present, the main disposal methods of chromium slag are storage and landfill, which not only causes serious waste of land resources, but also the unstable Cr(VI) in chromium slag will penetrate into the environment and cause pollution. It is urgent to adopt a more environmentally friendly way to efficiently utilize chromium slag.

[0003] The main chemical components of chromium slag are Fe2O3, SiO2, Al2O3, CaO, MgO and Cr2O3, which are similar to cement components, but the content is different. Therefore, using chromium slag as a concrete mineral admixture is an important way to achieve its large-scale application. However, chromium slag itself has low activity and is an inactive admixture, which leads to a small amount of it in concrete, greatly limiting its application in concrete.

[0004] The Chinese patent application with publication number CN110627448B discloses a method for preparing high-strength concrete using ferrochromium slag powder as an admixture, wherein a ferrochromium slag powder admixture activated by sodium carbonate and sodium sulfate as activators is disclosed, and cement, fly ash, fine aggregate, coarse aggregate and mineral powder are fully mixed to obtain a premix, and then an aqueous solution containing an admixture is added to the premix, and after fully mixing, the active ferrochromium slag powder is added to obtain a high-strength concrete material. Although this patent discloses a method for preparing high-strength concrete using ferrochromium slag powder as an admixture, the amount of ferrochromium slag powder is less than 10% of the amount of cement used, and the single chemical means does not fully activate the activity of the ferrochromium slag powder, and a large amount of chemical reagents are consumed, resulting in complex composition and increased cost, which restricts its large-scale promotion and application.

[0005] The Chinese patent application with publication number CN103979870A discloses a method for preparing concrete using chromium slag as a concrete mineral admixture. The method only grinds the chromium slag to a specific surface area of ​​300 to 600 m 2 / kg, an admixture capable of replacing 20% ​​of cement binder in concrete can be obtained. Although the invention has a simple process, the activation degree of chromium slag by a single grinding method is limited, so it is difficult to further increase its admixture in concrete. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a photovoltaic support base concrete material prepared by microwave-chemically activated chromium slag.

[0009] To solve the above technical problems, the present invention provides the following technical solutions: a photovoltaic bracket base concrete material prepared by microwave-chemically activated chromium slag, characterized in that the photovoltaic bracket base concrete material comprises the following raw materials in mass proportions: 46 to 185 parts of activated chromium slag, 276 to 415 parts of PO 42.5 cement, 140 to 175 parts of water, 512 to 542 parts of medium sand, 1206 to 1252 parts of gravel, and 4 to 9 parts of water reducer.

[0010] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a photovoltaic support base concrete material, which is characterized by comprising:

[0011] The chromium slag and the detoxifier are mixed evenly, and treated for 30 to 60 minutes under the condition of microwave output power of 1 to 3 kW;

[0012] The chromium slag after microwave activation treatment is mixed with a chemical activator and then ball-milled to obtain microwave-chemical synergistically activated chromium slag;

[0013] Add activated chromium slag, PO 42.5 cement, water, medium sand, gravel and water reducing agent into a mixer according to the mass parts, mix and stir to obtain a homogeneous concrete slurry;

[0014] The concrete slurry is poured into a mold, vibrated into shape, and pre-cured for 24 hours before demolding. The concrete slurry is then covered and cured in an environment with a temperature of 15 to 30°C. After hardening, photovoltaic cast-in-place pile concrete with microwave-chemical composite activated chromium slag as an admixture is obtained.

[0015] As a preferred embodiment of the preparation method of the present invention, the chromium slag and the antidote are mixed evenly, wherein the mass ratio of the chromium slag to the antidote is 100:10-20.

[0016] As a preferred solution of the preparation method of the present invention, the main chemical components of the chromium slag and their mass percentages are: Al2O3 8-13%, SiO2 8-12%, CaO 7-10%, Fe2O3 30-45%, and Cr2O3 6-9%.

[0017] As a preferred embodiment of the preparation method of the present invention, the detoxifying agent is waste sugarcane molasses, and its main chemical components and their mass percentages are: sucrose 24-36%, glucose 8-12%, fructose 10%-15%, polysaccharide 7-12%, and colloid 8-16%.

[0018] As a preferred embodiment of the preparation method of the present invention, the chromium slag after microwave activation treatment is mixed with a chemical stimulant and then ball-milled, wherein the mass ratio of the chromium slag after microwave activation treatment to the chemical stimulant is 100:2-5.

[0019] As a preferred solution of the preparation method of the present invention, the chemical activator is solid Na2SiO3 with a purity of 98%.

[0020] As a preferred embodiment of the preparation method of the present invention, the rotation speed of the ball mill is 300 to 500 rpm, and the processing time is 10 to 30 min.

[0021] As a preferred embodiment of the preparation method of the present invention, the specific surface area of ​​the chromium slag after ball milling is 400 to 480 m 2 / kg.

[0022] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a photovoltaic support foundation concrete material.

[0023] Beneficial effects of the present invention:

[0024] (1) The microwave-chemical synergistic activation process of chromium slag in the present invention is simple, has high activation efficiency, low energy consumption, and low reagent input. While simultaneously achieving harmless treatment of chromium slag, an active admixture that can replace a large amount of cement is obtained, effectively realizing the maximization of chromium slag resource recycling;

[0025] (2) The activated chromium slag prepared by the present invention can replace cement to save natural raw materials and reduce costs, avoid the large-scale emission of CO2 in the production process of the cement industry, have significant economic and environmental benefits, and have broad market application prospects;

[0026] (3) The present invention uses waste sugarcane molasses as a detoxifier, which not only realizes waste utilization and reduces the cost of chromium slag treatment, but also converts high-molecular organic matter into activated carbon during microwave high-temperature treatment to fill the internal pores of concrete, increase the density, and thus improve the macroscopic mechanical properties of concrete;

[0027] (4) The present invention is particularly suitable for the field of solid waste resource utilization and concrete material technology, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0029] Figure 1 This is the basic flow chart of preparing photovoltaic cast-in-place pile concrete using microwave-chemical composite activated chromium slag as admixture. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0033] The calcium-free roasted chromium slag used in Examples 1 to 4 and Comparative Examples 1 to 4 was provided by a company in Hubei. The leaching toxicity of Cr(VI) in the calcium-free roasted chromium slag was 252.78 mg / L. The main chemical components and contents are shown in Table 1.

[0034] Table 1 Main chemical composition and content of calcium-free roasted chromium slag (%)

[0035] Element <![CDATA[Fe2O3]]> <![CDATA[Cr2O3]]> <![CDATA[Na2O]]> <![CDATA[Al2O3]]> CaO MgO <![CDATA[SiO2]]> content 41.2 7.64 8.98 12.08 6.36 3.71 9.89

[0036] The waste sugarcane molasses used in Examples 1 to 3 was provided by a sugar manufacturing company in Guangxi. The main chemical components and contents of the molasses are shown in Table 2.

[0037] Table 2 Main chemical components and contents of waste sugarcane molasses (%)

[0038] Element sucrose fructose glucose Polysaccharides colloid content 25.0 8.0 9.0 13.6 16.0

[0039] Example 1

[0040] The method for preparing photovoltaic cast-in-place pile concrete using microwave-chemical composite activated chromium slag as an admixture provided in this embodiment comprises the following steps:

[0041] (1) The chromium slag and the detoxification agent waste sugarcane molasses were mixed uniformly in a mass ratio of 100:12 and treated in an industrial microwave oven with a microwave output power of 3 kW for 30 minutes;

[0042] (2) The chromium slag after microwave activation treatment in step (1) and solid Na2SiO3 with a purity of 98% were added into a ball mill at a mass ratio of 100:5, and ball milled at a speed of 500 rpm for 20 minutes to obtain a specific surface area of ​​418±15 m 2 / kg of microwave-chemical synergistic activated chromium slag.

[0043] The microwave-chemical synergistic activation chromium slag described in step (2) was subjected to a leaching toxicity test according to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T 299). The results showed that the leaching toxicity of total chromium was less than 0.15 mg / L, and the leaching toxicity of Cr(VI) was less than 0.05 mg / L, which met the standards for using chromium slag as a concrete material in the "Technical Specifications for Environmental Protection of Chromium Slag Pollution Control" (HJ / T 301-2007).

[0044] (3) adding 46 parts of activated chromium slag, 415 parts of PO 42.5 cement, 160 parts of water, 542 parts of medium sand, 1206 parts of gravel and 7 parts of water reducing agent into a mixer and mixing them thoroughly to prepare concrete slurry;

[0045] The concrete slurry was poured into the mold, and the mold was removed after pre-curing for 24 hours. The film was covered and cured in an environment with a temperature of 15-30°C. After forming and hardening, the photovoltaic cast-in-place pile concrete prepared by microwave-chemical composite activated chromium slag was obtained. The macroscopic mechanical properties of the concrete samples cured for 3d, 7d and 28d were tested in accordance with GB / T50081-2019 "Standard for Experimental Methods of Mechanical Properties of Ordinary Concrete" and GB / T 50107-2010 "Standard for Inspection and Evaluation of Concrete Strength". Non-standard specimens of 100mm×100mm×100mm were selected for basic mechanical properties testing, and the results are shown in Table 3.

[0046] Example 2

[0047] The method for preparing photovoltaic cast-in-place pile concrete using microwave-chemical composite activated chromium slag as an admixture provided in this embodiment comprises the following steps:

[0048] (1) The chromium slag and the detoxification agent waste sugarcane molasses were mixed uniformly in a mass ratio of 100:20 and treated in an industrial microwave oven with a microwave output power of 1 kW for 40 minutes;

[0049] (2) The chromium slag after microwave activation treatment in step (1) and solid Na2SiO3 with a purity of 98% were added into a ball mill at a mass ratio of 100:3, and ball milled at a speed of 400 rpm for 30 minutes to obtain a specific surface area of ​​456±22 m 2 / kg of microwave-chemical synergistic activated chromium slag.

[0050] The microwave-chemical synergistic activation chromium slag described in step (2) was subjected to a leaching toxicity test according to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T 299). The results showed that the leaching toxicity of total chromium was less than 0.15 mg / L, and the leaching toxicity of Cr(VI) was less than 0.05 mg / L, which met the standards for use as concrete materials in the "Technical Specifications for Environmental Protection of Chromium Slag Pollution Control" (HJ / T 301-2007).

[0051] (3) adding 92 parts of activated chromium slag, 369 parts of PO 42.5 cement, 175 parts of water, 512 parts of medium sand, 1252 parts of gravel and 5 parts of water reducing agent into a mixer and mixing them thoroughly to prepare concrete slurry;

[0052] The concrete slurry was poured into the mold, and the mold was removed after pre-curing for 24 hours, and the mold was covered and cured in an outdoor environment with a temperature of 15 to 30°C. The test method for the macroscopic mechanical properties of the concrete samples cured for 3d, 7d and 28d was the same as in Example 1, and the results are shown in Table 3.

[0053] Example 3

[0054] The method for preparing photovoltaic cast-in-place pile concrete using microwave-chemical composite activated chromium slag as an admixture provided in this embodiment comprises the following steps:

[0055] (1) The chromium slag and the detoxification agent waste sugarcane molasses were mixed uniformly in a mass ratio of 100:16 and treated in an industrial microwave oven with a microwave output power of 2 kW for 30 minutes;

[0056] (2) The chromium slag after microwave activation treatment in step (1) and solid Na2SiO3 with a purity of 98% were added into a ball mill at a mass ratio of 100:4, and ball milled at a speed of 400 rpm for 40 minutes to obtain a specific surface area of ​​445±16 m 2 / kg of microwave-chemical synergistic activated chromium slag.

[0057] The microwave-chemical synergistic activation chromium slag described in step (2) was subjected to a leaching toxicity test according to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T 299). The results showed that the leaching toxicity of total chromium was less than 0.15 mg / L, and the leaching toxicity of Cr(VI) was less than 0.05 mg / L, which met the standards for use as concrete materials in the "Technical Specifications for Environmental Protection of Chromium Slag Pollution Control" (HJ / T 301-2007).

[0058] (3) adding 138 parts of activated chromium slag, 323 parts of PO 42.5 cement, 145 parts of water, 525 parts of medium sand, 1230 parts of gravel and 9 parts of water reducing agent into a mixer and mixing them thoroughly to prepare concrete slurry;

[0059] The concrete slurry was poured into a mold, and after pre-curing for 24 hours, the mold was removed and cured under a film in an outdoor environment at a temperature of 15 to 30° C. The testing method for the macroscopic mechanical properties of the concrete samples cured for 3d, 7d and 28d was the same as in Example 1, and the results are shown in Table 3.

[0060] Example 4

[0061] The method for preparing photovoltaic cast-in-place pile concrete using microwave-chemical composite activated chromium slag as an admixture provided in this embodiment comprises the following steps:

[0062] (1) The chromium slag and the detoxification agent waste sugarcane molasses were mixed uniformly in a mass ratio of 100:16 and treated in an industrial microwave oven with a microwave output power of 2 kW for 40 minutes;

[0063] (2) The chromium slag after microwave activation treatment in step (1) and solid Na2SiO3 with a purity of 98% were added into a ball mill at a mass ratio of 100:5, and ball milled at a speed of 500 rpm for 40 minutes to obtain a specific surface area of ​​487±25 m 2 / kg of microwave-chemical composite activated chromium slag.

[0064] The microwave-chemical composite activated chromium slag described in step (2) was subjected to a leaching toxicity test according to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method" (HJ / T 299). The results showed that the leaching toxicity of total chromium was less than 0.15 mg / L, and the leaching toxicity of Cr(VI) was less than 0.05 mg / L, which met the standards for use as concrete materials in the "Technical Specifications for Environmental Protection of Chromium Slag Pollution Control" (HJ / T 301-2007).

[0065] (3) adding 185 parts of activated chromium slag, 276 parts of PO 42.5 cement, 175 parts of water, 525 parts of medium sand, 1230 parts of gravel and 5 parts of water reducing agent into a mixer and mixing them thoroughly to prepare concrete slurry;

[0066] The concrete slurry was poured into a mold, and after pre-curing for 24 hours, the mold was removed and cured under a film in an outdoor environment at a temperature of 15 to 30° C. The testing method for the macroscopic mechanical properties of the concrete samples cured for 3d, 7d and 28d was the same as in Example 1, and the results are shown in Table 3.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 4 is that the amount of activated chromium slag replacing cement in step (3) is increased to 50%, that is, the amount of activated chromium slag and cement are both 230.5 parts, and the remaining steps are the same as Example 4.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 4 is that the microwave activation treatment in step (1) is not performed, and the remaining steps are the same as Example 4.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 4 is that the ball milling treatment in step (2) is not performed, and the remaining steps are the same as Example 4.

[0073] Comparative Example 4

[0074] The difference between this comparative example and Example 4 is that in step (2), no chemical activator Na2SiO3 is added for ball milling, and the remaining steps are the same as Example 4.

[0075] Comparative Example 5

[0076] The difference between this comparative example and Example 4 is that the treatment processes of step (1) and step (2) are not carried out, the original chromium slag is directly used as a concrete admixture, and the remaining steps are the same as those of Example 4.

[0077] Comparative Example 6

[0078] The difference between this comparative example and Example 4 is that the detoxifying agent waste cane molasses is replaced by sucrose with a purity of 99%, and the remaining steps are the same as those of Example 4.

[0079] Comparative Example 7

[0080] The difference between this comparative example and Example 4 is that the detoxifying agent waste cane molasses is replaced by brown sugar (sucrose content is 88-95%), and the remaining steps are the same as Example 4.

[0081] The performance test results of the concrete materials prepared in Examples 1 to 4 and Comparative Examples 1 to 7 are shown in Table 3.

[0082] Table 3 Concrete material properties prepared in Examples 1 to 4 and Comparative Examples 1 to 7

[0083]

[0084]

[0085] As can be seen from the above table, the photovoltaic cast-in-place pile concrete prepared by using microwave-chemical composite activated chromium slag as admixture has good mechanical properties, and the 28d compressive strength can reach more than 25MPa, which meets the requirements of the "Technical Specification Standard for Solar Power Station Support Foundation" (GB 51101-2016) and the Technical Specification for Building Piles (JGJ 94-2008) for the strength grade of cast-in-place pile concrete to be not less than C25. As can be seen from comparative examples 1 to 4, microwave, ball milling, chemical activator and chromium slag dosage are the main factors affecting the strength of concrete, so they are the key optimization objects during the operation. The amount of composite activated chromium slag replacing cement is as high as 40%, and the concrete has a high absorption capacity for chromium slag. Therefore, the present invention has good development prospects in the harmless treatment of chromium slag and large-scale resource utilization.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A photovoltaic cast-in-place pile concrete with composite activated chromium slag as admixture, characterized in that: The photovoltaic cast-in-place pile concrete material comprises the following raw materials in parts by weight: 46-185 parts of activated chromium slag, 276-415 parts of PO 42.5 cement, 140-175 parts of water, 512-542 parts of medium sand, 1206-1252 parts of gravel, and 4-9 parts of water reducing agent.

2. The method for preparing photovoltaic cast-in-place pile concrete according to claim 1, characterized in that: include, The chromium slag and the detoxifier are mixed evenly, and treated for 30 to 60 minutes under the condition of microwave output power of 1 to 3 kW; The chromium slag after microwave activation treatment is mixed with a chemical activator and then ball-milled to obtain microwave-chemical synergistically activated chromium slag; Add activated chromium slag, PO 42.5 cement, water, medium sand, gravel and water reducing agent into a mixer according to the mass parts, mix and stir to obtain a homogeneous concrete slurry; The concrete slurry is poured into a mold, vibrated into shape, and pre-cured for 24 hours before demolding. The concrete slurry is then covered and cured in an environment with a temperature of 15 to 30°C. After hardening, photovoltaic cast-in-place pile concrete with microwave-chemical composite activated chromium slag as an admixture is obtained.

3. The preparation method according to claim 2, characterized in that: The chromium slag and the detoxifier are mixed evenly, wherein the mass ratio of the chromium slag to the detoxifier is 100:10-20.

4. The preparation method according to claim 3, characterized in that: The main chemical components of the chromium slag and their mass percentages are: Al2O3 8-13%, SiO2 8-12%, CaO 7-10%, Fe2O3 30-45%, and Cr2O3 6-9%.

5. The preparation method according to claim 3, characterized in that: The detoxifying agent is waste sugarcane molasses, and its main chemical components and their mass percentages are: sucrose 24-36%, glucose 8-12%, fructose 10%-15%, polysaccharide 7-12%, and colloid 8-16%.

6. The preparation method according to claim 2, characterized in that: The chromium slag after microwave activation treatment is mixed with a chemical stimulant and then ball-milled, wherein the mass ratio of the chromium slag after microwave activation treatment to the chemical stimulant is 100:2-5.

7. The preparation method according to claim 6, characterized in that: The chemical activator is solid Na2SiO3 with a purity of 98%.

8. The preparation method according to claim 6, characterized in that: The rotation speed of the ball mill is 300-500 rpm, and the processing time is 10-30 minutes.

9. The preparation method according to claim 6, characterized in that: The specific surface area of ​​the chromium slag after ball milling is 400-480m 2 / kg.

10. Application of photovoltaic cast-in-place pile concrete prepared by the preparation method according to any one of claims 2 to 9.

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