A method for preparing ready-mixed concrete by wet carbon fixation of water slag

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a method for preparing ready-mixed concrete by wet carbon fixation of slag, and discloses a method for preparing ready-mixed concrete by wet carbon fixation of slag, comprising the following steps: feeding slag into a liquid phase grinding device and introducing CO2, heating in a water bath, wet carbon fixation for 1-2 hours, standing for 10-20 minutes, taking the upper clear liquid as a hydration promoter, and the lower solid as a carbon fixation type admixture; adding 250-280 parts of cement, 350-400 parts of sand, and 1000-1400 parts of crushed stone into a mixer, stirring at a low speed for 15-30 minutes, then adding 300-450 parts of carbon fixation type admixture, 40-80 parts of hydration promoter, 5-10 parts of concrete admixture, and 160-200 parts of water, stirring at a high speed for 20-40 minutes, and obtaining ready-mixed concrete. The method of preparing ready-mixed concrete by wet carbon fixation of slag directly utilizes the slag discharged during the smelting of pig iron to mineralize and seal CO2, thereby replacing more cement. The process is simple, low-cost, green and environmentally friendly, and has a short preparation cycle, and can achieve high added value utilization of solid waste and CO2.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a method for preparing ready-mixed concrete by wet carbon fixation of slag. Background Art

[0002] Slag is blast furnace slag. It is an industrial solid waste discharged from the blast furnace when iron ore is used to smelt pig iron. SiO2, Al2O3, CaO, MgO and other substances in the iron ore react to form silicate melts, which react with water and cool rapidly into granules to obtain slag with a relatively irregular pore structure. As the amount of iron produced by blast furnaces continues to increase, more and more slag is produced. For a long time, blast furnace slag has been thrown away as waste, piling up like mountains, encroaching on fertile farmland, obstructing traffic, and even restricting blast furnace production. Replacing cement with slag can not only bring considerable economic benefits, but also reduce CO2 emissions.

[0003] CO2 is the most important greenhouse gas in the atmosphere, with an average concentration of 405.5 ppm in 2017. CO2 has a heat-insulating effect and will gradually increase the temperature of the earth's surface. The rise in sea levels caused by the greenhouse effect will also have a huge impact on the human living environment. Increased CO2 emissions will also lead to an increase in extreme weather phenomena, which will in turn affect global agriculture.

[0004] Wet carbon fixation refers to the process in which CO2 dissolves in water to form carbonic acid in the reaction solution medium, and the ore gradually dissolves under the action of carbonic acid to form carbonate precipitates. The wet carbon fixation process can realize the resource utilization of solid waste and seal CO2. It can also play a role in material crushing and particle size homogenization when combined with liquid phase grinding technology.

[0005] Chinese patent CN201910682948.2 discloses a composite admixture based on the activation technology of waste residues in mixing stations, and its preparation method and application. Waste residues such as water residues are first dried, and then a modifier is added for grinding. The prepared composite admixture can achieve high value-added application of waste residues and green production of concrete; however, its drying and ball milling steps consume a lot of energy, the process is complicated, the cycle is too long, and CO2 emissions are only reduced by replacing cement. Therefore, a method for preparing ready-mixed concrete by wet carbon fixation of water residues is proposed to solve the above problems. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the shortcomings of the prior art, the present invention provides a method for preparing ready-mixed concrete by wet carbon fixation of slag, which has the advantages of simple process, low cost, green environmental protection, etc., and solves the problems of high energy consumption, complex process, long cycle, etc. in steps such as drying and ball milling, and only reduces CO2 emissions by replacing cement. In addition, the slag after carbon fixation can replace more cement than before carbon fixation, further reducing the cost of concrete.

[0008] (II) Technical solution

[0009] In order to achieve the above-mentioned purpose of simple process, low cost and green environmental protection, the present invention provides the following technical solution: comprising the following steps:

[0010] 1) The water slag is sent to the liquid phase grinding equipment and CO2 is introduced, heated in a water bath, wet carbon fixation for 1-2 hours, and left to stand for 10-20 minutes. The upper clear liquid is taken as the hydration accelerator, and the lower solid is taken as the carbon fixation admixture;

[0011] 2) Add 250-280 parts of cement, 350-400 parts of sand, and 1000-1400 parts of crushed stone into a mixer, stir at low speed for 15-30 minutes, then add 300-450 parts of fixed carbon admixture, 40-80 parts of hydration accelerator, 5-10 parts of concrete admixture, and 160-200 parts of water, stir at high speed for 20-40 minutes to obtain ready-mixed concrete.

[0012] Preferably, the slag is prepared by quenching blast furnace slag from pig iron in a slag pool, and the solid content of the slag is 0.2-0.8wt%, the CaO content is not less than 23%, the Al2O3 content is not less than 15wt%, the SO3 content does not exceed 2wt%, and the SiO2 content is not less than 40%.

[0013] Preferably, the CO2 gas rate is 5-20 L / min.

[0014] Preferably, the rotation speed of the liquid phase grinding equipment is 300-1000 rps.

[0015] Preferably, the water bath equipment is a digital constant temperature water bath, and the water bath heating temperature is 50-90°C.

[0016] Preferably, the median particle size of the hydration accelerator is 0.08-0.5 μm, and the median particle size of the carbon-fixing admixture is 1-10 μm.

[0017] Preferably, the cement is ordinary Portland cement, and the concrete admixture is one of a naphthalene-based water reducer or a polycarboxylate water reducer.

[0018] Preferably, the sand is mineral sand particles, and the fineness modulus of the sand is 2.0-3.0.

[0019] Preferably, the speed of the low-speed stirring is 800-1000 r / min, and the speed of the high-speed stirring is 1200-1500 r / min.

[0020] Preferably, the crushed stone is 5-10 mm continuously graded crushed stone.

[0021] The mechanism of the method of the present invention is as follows:

[0022] The strong mechanical force of wet grinding is used to ultra-fine the slag into submicron and nanometer particles. Since the mechanical force runs through the entire carbonization reaction process, new carbonization reaction surfaces always appear during the carbonization process, thereby improving the carbon fixation efficiency of the slag. The liquid phase grinding process is used to break the siliceous layer on the surface of the slag particles, promote the dissolution of Ca2+ and Mg2+ inside the slag particles, and the grinding environment temperature is regulated by the stirring rate of the circulating water and the vertical wet mill stirring rod to control the solubility of CO2 in the grinding aqueous solution and the carbonization reaction efficiency. Controlling the CO2 introduction rate and the grinding time of the vertical ball mill can effectively control the median particle size of the slag. At the same time, the rotation speed of the vertical ball mill can drive the particles in the aqueous solution to collide with each other, resulting in the stratification of submicron particles and nanoparticles, realizing the multi-scale resource utilization of the slag.

[0023] (III) Beneficial effects

[0024] Compared with the prior art, the present invention provides a method for preparing ready-mixed concrete by wet carbon fixation of water slag, which has the following beneficial effects:

[0025] 1. The method of preparing ready-mixed concrete by wet carbon fixation of slag directly utilizes the slag discharged during the smelting of pig iron to mineralize and seal CO2. The process is simple, low-cost, green and environmentally friendly, and has a short preparation cycle, and can achieve high added value utilization of solid waste and CO2.

[0026] 2. The method for preparing ready-mixed concrete by wet carbon fixation of slag reduces CO2 emission by mineralizing and sealing CO2 under wet grinding of slag and replacing part of cement with slag. On the one hand, the carbon-fixed slag is neutral and has a good effect when added to concrete, thereby reducing the amount of admixtures. On the other hand, the carbon-fixed slag can replace more cement than the slag before carbon fixation, thereby reducing the amount of cementitious materials. The synergistic effect of the two aspects effectively reduces the cost of ready-mixed concrete.

[0027] 3. The method for preparing ready-mixed concrete by wet carbon fixation of slag improves its activity by grinding the slag to nanometer and micrometer scales. Micrometer-level slag can improve the workability and durability of concrete, giving it a dense structure and excellent interface bonding properties; nanometer-level slag can have a good filling effect and nucleus induction effect, thereby promoting hydration. The combined use of the two not only improves the overall performance of concrete, but also realizes the multi-level utilization of slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a test result diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] (1) The slag is fed into a liquid phase grinding device and CO2 is introduced, heated in a water bath, and wet carbonized for 2 hours. The slag is left to stand for 20 minutes, and the upper clear liquid is taken as a hydration accelerator, and the lower solid is taken as a carbon-fixing admixture;

[0032] (2) Add 280 parts of cement, 400 parts of sand, and 1400 parts of crushed stone into a mixer and stir at a low speed for 30 minutes. Then add 450 parts of carbon-fixing admixture, 80 parts of hydration accelerator, 10 parts of concrete admixture, and 200 parts of water and stir at a high speed for 40 minutes to obtain ready-mixed concrete.

[0033] In this embodiment, the solid content of the slag is 0.5, the rotation speed of the liquid phase grinding equipment is 1000rps, the CO2 introduction rate is 20L / min, the water bath heating temperature is 80°C, the concrete admixture is polycarboxylic acid water reducer, and the low-speed stirring and high-speed stirring speeds are 1000r / min and 1500r / min respectively.

[0034] Embodiment 2:

[0035] (1) The slag was fed into a liquid phase grinding device and CO2 was introduced, heated in a water bath, and wet carbon was fixed for 1.5 hours. The supernatant was taken as a hydration accelerator, and the solid in the lower layer was taken as a carbon-fixing admixture;

[0036] (2) Add 250 parts of cement, 350 parts of sand, and 1000 parts of crushed stone into a mixer and stir at a low speed for 15 minutes. Then add 300 parts of carbon-fixing admixture, 40 parts of hydration accelerator, 5 parts of concrete admixture, and 160 parts of water and stir at a high speed for 20 minutes to obtain ready-mixed concrete.

[0037] In this embodiment, the solid content of the slag is 0.8, the rotation speed of the liquid phase grinding equipment is 800rps, the CO2 introduction rate is 15L / min, the water bath heating temperature is 70°C, the concrete admixture is a naphthalene-based water reducer, and the low-speed stirring and high-speed stirring speeds are 800r / min and 1200r / min respectively.

[0038] Embodiment three:

[0039] (1) The slag was fed into a liquid phase grinding device and CO2 was introduced, heated in a water bath, and wet carbon was fixed for 1 hour. The slag was left to stand for 15 minutes, and the upper clear liquid was taken as a hydration accelerator, and the lower solid was taken as a carbon-fixing admixture;

[0040] (2) Add 280 parts of cement, 350 parts of sand, and 1000 parts of crushed stone into a mixer and stir at a low speed for 25 minutes. Then add 400 parts of carbon-fixing admixture, 60 parts of hydration accelerator, 10 parts of concrete admixture, and 180 parts of water and stir at a high speed for 30 minutes to obtain ready-mixed concrete.

[0041] In this embodiment, the solid content of the slag is 0.6, the rotation speed of the liquid phase grinding equipment is 600rps, the introduction rate of C02 is 10L / min, the temperature of the water bath heating is 60°C, the concrete admixture is a naphthalene-based water reducer, and the speeds of low-speed stirring and high-speed stirring are 900r / min and 1300r / min respectively.

[0042] Embodiment 4:

[0043] (1) The water slag is sent to a liquid phase grinding device and CO2 is introduced, heated in a water bath, and wet carbon is fixed for 0.5 h. The upper clear liquid is taken as a hydration accelerator, and the lower solid is taken as a carbon-fixing admixture;

[0044] (2) Add 260 parts of cement, 380 parts of sand, and 1200 parts of crushed stone into a mixer and stir at a low speed for 25 minutes. Then add 350 parts of carbon-fixing admixture, 80 parts of hydration accelerator, 7 parts of concrete admixture, and 200 parts of water and stir at a high speed for 35 minutes to obtain ready-mixed concrete.

[0045] In this embodiment, the solid content of the slag is 0.4, the rotation speed of the liquid phase grinding equipment is 300rps, the CO2 introduction rate is 5L / min, the water bath heating temperature is 50°C, the concrete admixture is polycarboxylic acid water reducer, and the low-speed stirring and high-speed stirring speeds are 800r / min and 1200r / min respectively.

[0046] Embodiment five:

[0047] (1) The slag was fed into a liquid phase grinding device and CO2 was introduced, heated in a water bath, and wet carbon was fixed for 1 hour. The slag was left to stand for 15 minutes, and the upper clear liquid was taken as a hydration accelerator, and the lower solid was taken as a carbon-fixing admixture;

[0048] (2) Add 280 parts of cement, 400 parts of sand, and 1000 parts of crushed stone into a mixer and stir at a low speed for 30 minutes. Then add 300 parts of carbon-fixing admixture, 40 parts of hydration accelerator, 8 parts of concrete admixture, and 160 parts of water and stir at a high speed for 30 minutes to obtain ready-mixed concrete.

[0049] In this embodiment, the solid content of the slag is 0.2, the rotation speed of the liquid phase grinding equipment is 600rps, the CO2 introduction rate is 10L / min, the water bath heating temperature is 65°C, the concrete admixture is a naphthalene-based water reducer, and the low-speed stirring and high-speed stirring speeds are 900r / min and 1400r / min, respectively.

[0050] Experimental example:

[0051] Examples 1-5 were tested, including: compressive strength test and slump test of ready-mixed concrete, TG test of carbon fixation rate of water slag, and median particle size test of carbon fixation admixture and hydration accelerator. The specific results are shown in Figure 1 .

[0052] The beneficial effects of the present invention are: the ready-mixed concrete prepared by the above preparation method has excellent compressive strength, can effectively control the slump loss of concrete, reduce the amount of admixtures, and at the same time mineralize and seal a large amount of CO2, which can achieve high added value utilization of solid waste and CO2.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing ready-mixed concrete by wet carbon fixation of slag, characterized in that: The following steps are involved: 1) Feed the water slag into the liquid phase grinding equipment and introduce CO2, heat it in a water bath, wet carbon fix for 1-2 hours, let it stand for 10-20 minutes, take the upper clear liquid as the hydration accelerator, and the lower solid as the carbon fixation admixture; 2) Add 250-280 parts of cement, 350-400 parts of sand, 1000-1400 parts of crushed stone into a mixer, stir at low speed for 15-30 minutes, then add 300-450 parts of carbon-fixing admixture, 40-80 parts of hydration accelerator, 5-10 parts of concrete admixture, 160-200 parts of water, stir at high speed for 20-40 minutes to obtain ready-mixed concrete; The water slag is prepared by quenching the blast furnace slag from pig iron smelting in a slag pool, and the CaO content is not less than 23%, the Al2O3 content is not less than 15wt%, the SO3 content is not more than 2wt%, and the SiO2 content is not less than 40%; The median particle size of the hydration accelerator is 0.08-0.5 μm, and the median particle size of the carbon-fixing admixture is 1-10 μm.

2. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The CO2 gas flow rate is 5-20L / min.

3. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The rotation speed of the liquid phase grinding equipment is 300-1000rps.

4. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The water bath heating equipment is a digital display constant temperature water bath pot, and the water bath heating temperature is 50-90°C.

5. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The cement is ordinary Portland cement, and the concrete admixture is one of a naphthalene-based water reducer or a polycarboxylic acid water reducer.

6. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The sand is mineral sand particles, and the fineness modulus of the sand is 2.0-3.

0.

7. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The speed of the low-speed stirring is 800-1000 r / min, and the speed of the high-speed stirring is 1200-1500 r / min.

8. The method for preparing ready-mixed concrete by wet carbon fixation of slag according to claim 1, characterized in that: The crushed stone is a crushed stone with a continuous grade of 5-10 mm.

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