A carbonized calcined coal gangue solid waste-based cementitious material and its preparation method

Abstract

This invention proposes a carbonized calcined coal gangue solid waste-based cementitious material and its preparation method, belonging to the technical field of coal gangue solid waste utilization. The raw materials for the carbonized coal gangue-based cementitious material of this invention include 30-70 parts of calcined coal gangue powder, 20-50 parts of premixed concrete waste, 10-20 parts of cement, 0-5 parts of gypsum, 0.5-1.0 parts of surfactant, and 0.1-0.5 parts of organic amine. First, the coal gangue solid waste is crushed, ground, and calcined. Then, it is mixed with premixed concrete waste, ordinary silicate cement, gypsum, surfactant, and organic amine. Finally, industrial carbon dioxide is introduced and the mixture is dried to obtain the final product. The performance indicators of the carbonized calcined coal gangue solid waste-based cementitious material of this invention are comparable to those of PO 42.5 grade cement, realizing the large-scale utilization of coal gangue solid waste and the preparation of low-carbon cementitious materials. The process is simple and has practical application value.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue solid waste utilization technology, and particularly relates to a carbonized and calcined coal gangue solid waste-based cementitious material and its preparation method. Background Technology

[0002] Coal gangue is a solid waste generated during coal production and processing. It is a symbiotic resource of coal, occurring alongside coal during coal formation. It is a carbonaceous rock with an ash content typically greater than 50% and a calorific value generally ranging from 3.5 to 8.3 mJ / kg. The main minerals in coal gangue are clay minerals such as kaolinite and chlorite, and α-quartz. Its main chemical components are SiO2, Al2O3, and Fe2O3. After activation treatment, the clay minerals decompose into amorphous SiO2 and Al2O3 substances, giving it a certain degree of activity. There are three main methods for activating coal gangue: thermal activation, chemical activation, and mechanical activation. The effects of calcining coal gangue are twofold: first, to remove carbon from the coal gangue; and second, to dehydrate and decompose the coal gangue after calcination, generating metakaolinite and amorphous silica and alumina, exhibiting pozzolanic activity.

[0003] While adding activated coal gangue powder to cement reduces carbon emissions and environmental pollution to some extent, the high porosity and impurities in coal gangue can affect the workability and mechanical properties of concrete. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a carbonized calcined coal gangue solid waste-based cementitious material and its preparation method. This invention involves carbonizing coal gangue, premixed concrete waste, gypsum, surfactants, and organic amines, then mixing them with ordinary silicate cement to prepare the carbonized calcined coal gangue solid waste-based cementitious material. This method can improve the activity of coal gangue, optimize its pore structure, and make the performance indicators of coal gangue solid waste as a cementitious material comparable to PO 42.5 grade cement.

[0005] To achieve the above objectives, the present invention provides a carbonized calcined coal gangue solid waste-based cementitious material, comprising the following raw materials in parts by weight: 30-70 parts of calcined coal gangue powder, 20-50 parts of premixed concrete waste residue, 10-20 parts of cement, 0-5 parts of gypsum (not zero in amount), 0.5-1.0 parts of surfactant, and 0.1-0.5 parts of organic amine.

[0006] Furthermore, the calcined coal gangue powder has a particle size of less than 75 μm and an apparent density of 2200-2500 kg / m³. 3 The water absorption rate is 2.10-4.40%.

[0007] Furthermore, the moisture content of the premixed concrete waste is less than 35%, and it comes from the filter residue during the washing of the concrete at the mixing plant. Its main components are calcium phase substances after cement hydration, such as Ca(OH)2 and CSH, which can be carbonized to generate calcium carbonate and highly polymerized amorphous silica-alumina gel.

[0008] Furthermore, the gypsum is dihydrate gypsum or industrial by-product gypsum, with phosphogypsum preferred, and its CaSO4 content is greater than 80%.

[0009] Furthermore, the cement is P·O42.5 grade ordinary Portland cement or PII42.5 grade Portland cement.

[0010] Furthermore, the surfactant is sodium lauryl sulfate or an alkyl sulfonate.

[0011] Furthermore, the organic amine is tributylamine or diethylbutylamine.

[0012] This invention also provides a method for preparing the carbonized calcined coal gangue solid waste-based cementitious material, specifically including the following steps:

[0013] (1) Weigh each raw material according to the weight proportions, and after ball milling the premixed concrete waste residue for 20 minutes, mix it with calcined coal gangue powder to obtain solid mixture A;

[0014] (2) The solid mixture A was soaked in water, surfactant and organic amine for 30 min to obtain solid-liquid mixture B;

[0015] (3) Gas is introduced into the solid-liquid mixture B and stirred, and then dried to obtain solid mixture C;

[0016] (4) The solid mixture C is mixed and stirred with the gypsum and cement to obtain the carbonized calcined coal gangue solid waste-based cementitious material.

[0017] Furthermore, the calcined coal gangue powder is obtained by ball milling coal gangue for 60 minutes and sieving it after calcination. The calcination temperature is 700℃, the calcination time is 2 hours, and the heat preservation time after the calcination is completed is 30 minutes.

[0018] The functions of calcining coal gangue are twofold: first, to remove carbon from the coal gangue; and second, to dehydrate and decompose the coal gangue after calcination, generating metakaolinite, amorphous silica, and alumina, thereby giving the coal gangue a certain degree of pozzolanic activity.

[0019] Furthermore, in step (3), the gas is introduced and stirred for 4 hours.

[0020] Furthermore, in step (3), the gas is CO2 gas, and the CO2 gas is industrial-grade CO2 gas with a purity of 99%.

[0021] Introducing CO2 gas for stirring allows the calcium phase of the waste residue in ready-mixed concrete to carbonize with dissolved CO2, generating calcium carbonate and highly polymerized amorphous silica-alumina gel. This improves the activity of the waste residue powder, fills the pores of the coal gangue powder, and reduces the water absorption rate.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] (1) This invention first carbonizes coal gangue, then mixes premixed concrete waste residue with calcined coal gangue powder, and uses wet carbonization to react partially hydrated Ca(OH)2 and CSH with CO2 to obtain calcium carbonate and highly polymerized amorphous silica-alumina gel. This improves the activity of the waste residue powder and fills the pores of the coal gangue powder, reducing water absorption. In addition, the pozzolanic activity in the calcined coal gangue powder is activated, and the cementitious material prepared by mixing with cement has excellent properties (the activated coal gangue contains Al2O3 and SiO2, which have high pozzolanic activity, while the calcium carbonate generated from the carbonized waste residue has certain activity, which can not only provide crystal nuclei for the hydration growth of cement, but also react with C3A, CH and other substances in cement clinker to generate hydration products such as AFt and CO3-AFm, and the amorphous silica-alumina gel also has certain pozzolanic activity). Furthermore, the preparation method and construction process of this invention are simple, easy to operate, and have practical application value.

[0024] (2) This invention crushes, washes and screens the solid waste after coal mining to obtain clean and suitable coal gangue, and then processes it to make a cementitious material, which reduces the amount of cement used and thus reduces carbon dioxide emissions. It is a green and economical preparation method that is suitable for promotion.

[0025] (3) This invention uses coal gangue powder to replace part of the cement, which can alleviate the shortage of materials in the construction industry to a certain extent, thereby exploring a sustainable cementitious material preparation method; it has certain environmental protection significance.

[0026] (4) This invention utilizes solid waste generated during coal mining, solving some of the solid waste disposal problems, reducing environmental pollution, and turning waste into treasure. It has significant economic and environmental value. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] This invention provides a carbonized calcined coal gangue solid waste-based cementitious material, comprising the following raw materials in parts by weight: 30-70 parts of calcined coal gangue powder, 20-50 parts of premixed concrete waste residue, 10-20 parts of cement, 0-5 parts of gypsum (not zero in amount), 0.5-1.0 parts of surfactant, and 0.1-0.5 parts of organic amine.

[0033] In a preferred embodiment of the present invention, the calcined coal gangue powder has a particle size of less than 75 μm and an apparent density of 2200-2500 kg / m³. 3 The water absorption rate is 2.10-4.40%.

[0034] In a preferred embodiment of the present invention, the moisture content of the premixed concrete waste residue is less than 35%, which comes from the filter residue during the washing of concrete at the mixing plant. Its main components are calcium phase substances after cement hydration, such as Ca(OH)2 and CSH, which can be carbonized to generate calcium carbonate and highly polymerized amorphous silica-alumina gel.

[0035] In a preferred embodiment of the present invention, the gypsum is dihydrate gypsum or industrial by-product gypsum, with phosphogypsum preferred, and its CaSO4 content is greater than 80%.

[0036] In a preferred embodiment of the present invention, the gypsum and cement are P·O42.5 grade ordinary Portland cement or PII42.5 grade Portland cement.

[0037] In a preferred embodiment of the present invention, the surfactant is sodium lauryl sulfate or an alkyl sulfonate.

[0038] In a preferred embodiment of the present invention, the organic amine is tributylamine or diethylbutylamine.

[0039] This invention also provides a method for preparing the carbonized calcined coal gangue solid waste-based cementitious material, comprising the following steps:

[0040] (1) Weigh each raw material according to the weight proportions, and after ball milling the premixed concrete waste residue for 20 minutes, mix it with calcined coal gangue powder to obtain solid mixture A;

[0041] (2) The solid mixture A was soaked in water, surfactant and organic amine for 30 min to obtain solid-liquid mixture B;

[0042] (3) Industrial carbon dioxide gas was introduced into the solid-liquid mixture B and stirred, and then dried to obtain solid mixture C;

[0043] (4) The solid mixture C is mixed and stirred with the gypsum and cement to obtain the carbonized calcined coal gangue solid waste-based cementitious material.

[0044] In a preferred embodiment of the present invention, the calcined coal gangue powder is obtained by ball milling coal gangue for 60 minutes and sieving it after calcination treatment. The calcination treatment temperature is 700℃, the calcination time is 2 hours, and the heat preservation time after the calcination treatment is 30 minutes.

[0045] In step (3) of the preferred embodiment of the present invention, CO2 gas is introduced and stirred for 4 hours.

[0046] In step (3) of the preferred embodiment of the present invention, the CO2 gas is industrial-grade CO2 gas with a purity of 99%.

[0047] In the embodiments of this invention, unless otherwise specified, "parts" refers to "number of parts by weight".

[0048] The coal gangue used in this embodiment of the invention comes from solid waste coal gangue mined in Guizhou Province, with a carbon content of ≤8%. The ready-mixed concrete waste comes from solid waste recycled from a local commercial concrete mixing plant in Wuhan, with a moisture content of less than 35%.

[0049] The technical solution of the present invention will be further illustrated by the following embodiments.

[0050] Example 1

[0051] A carbonized calcined coal gangue solid waste-based cementitious material comprises the following raw materials in parts by weight: 50 parts calcined coal gangue powder, 30 parts premixed concrete waste residue, 15 parts PO42.5 grade silicate cement, 5 parts phosphogypsum, 0.5 parts alkyl sulfonate, and 0.5 parts diethylbutylamine. The material specifically includes the following steps:

[0052] (1) The coal gangue was placed in a quartz crucible and calcined in a muffle furnace. The temperature was set at 700℃ for 2 hours and held for 30 minutes. After completion, it was naturally cooled to obtain solid particles. Then, it was poured into a ball mill and ball-milled for 60 minutes. After passing through a 0.075mm sieve, the calcined coal gangue powder was obtained. The premixed concrete waste was poured into a ball mill and ball-milled for 20 minutes. Then it was added to the calcined coal gangue powder and mixed to obtain solid mixture A.

[0053] (2) Take the solid mixture A obtained in step (1) and transfer it to a basin. Add 200 parts of water, alkyl sulfonate and diethylbutylamine and soak for 30 minutes to obtain solid-liquid mixture B;

[0054] (3) In the solid-liquid mixture B obtained in step (2), industrial-grade CO2 gas with a purity of 99% was introduced and stirred for 4 hours. Then, the excess water was poured out and the mixture was dried in a forced-air drying oven for 24 hours to obtain solid mixture C.

[0055] (4) The solid mixture C obtained in step (3) is mixed with phosphogypsum and P·O42.5 grade ordinary silicate cement to obtain carbonized calcined coal gangue solid waste-based cementitious material.

[0056] Example 2

[0057] A carbonized calcined coal gangue solid waste-based cementitious material comprises the following raw materials in parts by weight: 30 parts calcined coal gangue powder, 50 parts ready-mixed concrete waste residue, 17 parts PO42.5 grade silicate cement, 3 parts phosphogypsum, 1 part sodium lauryl sulfate, and 0.5 parts tributylamine. The specific steps include:

[0058] (1) Coal gangue was placed in a quartz crucible and calcined in a muffle furnace at 700℃ for 2 hours and held for 30 minutes. After calcination, the mixture was allowed to cool naturally to obtain solid particles. These particles were then ball-milled for 60 minutes and passed through a 0.075mm sieve to obtain calcined coal gangue powder (apparent density 2200-2500 kg / m³). 3 (Water absorption rate 2.10-4.40%), the premixed concrete waste residue was poured into a ball mill and ball-milled for 20 minutes, then added to calcined coal gangue powder and mixed to obtain solid mixture A;

[0059] (2) Take the solid mixture A obtained in step (1) and transfer it to a basin. Add 200 parts of water, sodium lauryl sulfate and tributylamine and soak for 30 minutes to obtain solid-liquid mixture B;

[0060] (3) In the solid-liquid mixture B obtained in step (2), industrial-grade CO2 gas with a purity of 99% was introduced and stirred for 4 hours. Then, the excess water was poured out and the mixture was dried in a forced-air drying oven for 24 hours to obtain solid mixture C.

[0061] (4) The solid mixture C obtained in step (3) is mixed with phosphogypsum and P·II42.5 grade ordinary silicate cement to obtain carbonized calcined coal gangue solid waste-based cementitious material.

[0062] Example 3

[0063] A carbonized calcined coal gangue solid waste-based cementitious material comprises the following raw materials in parts by weight: 45 parts calcined coal gangue powder, 35 parts ready-mixed concrete waste residue, 15 parts PO42.5 grade silicate cement, 5 parts phosphogypsum, 1 part sodium lauryl sulfate, and 0.5 parts tributylamine. The specific steps include:

[0064] (1) Coal gangue was placed in a quartz crucible and calcined in a muffle furnace at 700℃ for 2 hours and held for 30 minutes. After calcination, the mixture was allowed to cool naturally to obtain solid particles. These particles were then ball-milled for 60 minutes and passed through a 0.075mm sieve to obtain calcined coal gangue powder (apparent density 2200-2500 kg / m³). 3 (Water absorption rate 2.10-4.40%), the premixed concrete waste residue was poured into a ball mill and ball-milled for 20 minutes, then added to calcined coal gangue powder and mixed to obtain solid mixture A;

[0065] (2) Take the solid mixture A obtained in step (1) and transfer it to a basin. Add 200 parts of water, sodium lauryl sulfate and tributylamine and soak for 30 minutes to obtain solid-liquid mixture B;

[0066] (3) In the solid-liquid mixture B obtained in step (2), industrial-grade CO2 gas with a purity of 99% was introduced and stirred for 4 hours. Then, the excess water was poured out and the mixture was dried in a forced-air drying oven for 24 hours to obtain solid mixture C.

[0067] (4) The solid mixture C obtained in step (3) is mixed with phosphogypsum and P·II42.5 grade ordinary silicate cement to obtain carbonized calcined coal gangue solid waste-based cementitious material.

[0068] Comparative Example 1

[0069] Same as Example 3, except that the raw material coal gangue in step (1) is not calcined. Step (1) is as follows: the coal gangue is poured into a ball mill and ball-milled for 60 minutes, and then passed through a 0.075mm sieve to obtain coal gangue powder. The premixed concrete waste residue is poured into a ball mill and ball-milled for 20 minutes, and then added to the calcined coal gangue powder. The mixture is stirred to obtain solid mixture A.

[0070] Comparative Example 2

[0071] Same as Example 3, except that the premixed concrete waste residue in step (1) is not ball-milled. Step (1) specifically involves: loading coal gangue into a quartz crucible and placing it in a muffle furnace for calcination. The temperature is set at 700℃ for 2 hours and held for 30 minutes. After completion, the mixture is allowed to cool naturally to obtain solid particles. These particles are then poured into a ball mill and ball-milled for 60 minutes before being sieved through a 0.075mm sieve to obtain calcined coal gangue powder (apparent density of 2200-2500 kg / m³). 3 (Water absorption rate 2.10-4.40%), add premixed concrete waste to calcined coal gangue powder, mix and stir to obtain solid mixture A.

[0072] Comparative Example 3

[0073] Same as Example 3, except that air is introduced in step (3).

[0074] Performance testing

[0075] Concrete was prepared using the cementitious materials prepared in Examples 1-3 and Comparative Examples 1-3 as raw materials:

[0076] The concrete used 5-20mm continuously graded natural crushed stone, medium sand from river sand in Zone II, and a polycarboxylate superplasticizer with a water reduction rate of 20%-30%. The water used was tap water from Wuhan. The sand ratio and water-cement ratio were 54% and 0.40, respectively, and the superplasticizer dosage was 1.5%. The concrete was machine-mixed under forced mixing conditions. The feeding sequence was as follows: after the coarse and fine aggregates were mixed evenly, the cementitious material was added, and after further mixing, the mixing water with admixtures was added. The mixture was then mixed for another 3-5 minutes. After that, a consistency test of the mixture was conducted, and specimens were formed. After demolding for 24 hours, the specimens were cured according to standard to the specified age (28 days). Mechanical property tests were conducted on cubic specimens (100mm×100mm×100mm) and prism specimens (100mm×100mm×300mm) according to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The performance test results are shown in Table 1.

[0077] Table 1. Statistical results of concrete performance tests.

[0078]

[0079] As shown in Table 1, the compressive strength of the concrete in all three examples exceeded 35 MPa, reaching a maximum of 44 MPa, and the splitting tensile strength exceeded 3.0 MPa, reaching a maximum of 3.5 MPa. Examples 3 and 1 show that incorporating calcined coal gangue can improve the compressive and splitting tensile strengths of the composite cementitious material; grinding the stirred waste residue can also improve these properties; and introducing carbon dioxide can enhance the calcined coal gangue-based solid waste cementitious material. This indicates that calcining coal gangue, mixing it with finely ground stirred waste residue, and then carbonizing it can improve the mechanical properties of calcined coal gangue-based solid waste cementitious materials.

[0080] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A carbonized calcined coal gangue solid waste-based cementitious material, characterized in that, The raw materials include the following components in parts by weight: calcined coal gangue powder 30-70 parts, pre-mixed concrete waste residue 20-50 parts, cement 10-20 parts, gypsum 0-5 parts, surfactant 0.5-1.0 parts, and organic amine 0.1-0.5 parts; The surfactant is sodium lauryl sulfate or alkyl sulfonate; The organic amine is tributylamine or diethylbutylamine; The preparation method of the carbonized calcined coal gangue solid waste-based cementitious material includes the following steps: (1) The raw materials are weighed in parts by weight, and the pre-mixed concrete waste residue is ball milled and mixed with the calcined coal gangue powder to obtain a solid mixture A; (2) The solid mixture A is soaked with water, surfactant, and organic amine to obtain a solid-liquid mixture B; (3) The gas is introduced into the solid-liquid mixture B and stirred, and then dried to obtain a solid mixture C; (4) The solid mixture C is mixed and stirred with the gypsum and cement to obtain the carbonized calcined coal gangue solid waste-based cementitious material; In step (3), the industrial carbon dioxide gas is introduced and stirred for 4 hours.

2. The carbonized calcined coal gangue solid waste-based cementitious material according to claim 1, characterized in that, The particle size of the calcined coal gangue micro powder is less than 75 μm, the apparent density is 2200-2500 kg / m 3 , and the water absorption is 2.10-4.40%.

3. The carbonized calcined coal gangue solid waste-based cementitious material according to claim 1, characterized in that, The pre-mixed concrete waste residue has a water content of less than 35%.

4. The carbonized calcined coal gangue solid waste-based cementitious material of claim 1, wherein, The cement is P·O42.5 grade ordinary portland cement or PII42.5 grade portland cement.

5. The carbonized calcined coal gangue solid waste based cementitious material as claimed in claim 1, wherein, The gypsum is dihydrate gypsum or industrial by-product gypsum.

6. The carbonized calcined coal gangue solid waste based cementitious material of claim 1, wherein, The solid mixture A is soaked with water, surfactant, and organic amine for 30 minutes. The surfactant is sodium lauryl sulfate or alkyl sulfonate; The organic amine is tributylamine or diethylbutylamine; The preparation method of the carbonized calcined coal gangue solid waste-based cementitious material includes the following steps: (1) The raw materials are weighed in parts by weight, and the pre-mixed concrete waste residue is ball milled and mixed with the calcined coal gangue powder to obtain a solid mixture A; (2) The solid mixture A is soaked with water, surfactant, and organic amine to obtain a solid-liquid mixture B; (3) The gas is introduced into the solid-liquid mixture B and stirred, and then dried to obtain a solid mixture C; (4) The solid mixture C is mixed and stirred with the gypsum and cement to obtain the carbonized calcined coal gangue solid waste-based cementitious material; In step (3), the industrial carbon dioxide gas is introduced and stirred for 4 hours. The pre-mixed concrete waste residue has a water content of less than 35%. The cement is P·O42.5 grade ordinary portland cement or PII42.5 grade portland cement. The gypsum is dihydrate gypsum or industrial by-product gypsum. The solid mixture A is soaked with water, surfactant, and organic amine for 30 minutes.

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