Carbonized aerated concrete and preparation method thereof

Abstract

The carbonized aerated concrete is prepared from the following raw materials in parts by weight: 90 to 95 parts of steel slag, 5 to 10 parts of alkali activator, 25 to 30 parts of water, 0.05 to 0.1 part of water reducing agent, 0.1 to 0.2 part of sodium alpha-olefin sulfonate and 3 to 5 parts of aluminum sulfate solution. The carbonized aerated concrete takes the steel slag as a main raw material, has the advantages of light weight, high strength, good thermal insulation performance and shrinkage performance and the like, can realize resource utilization of various industrial wastes, and has remarkable economic and environmental benefits; and the related maintenance method is relatively simple, convenient to operate, relatively short in preparation period and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to carbonized aerated concrete and a preparation method thereof. Background Art

[0002] Aerated concrete can be generally divided into autoclaved aerated concrete and non-autoclaved aerated concrete according to the maintenance method. The strength of both comes from the hydration products such as hydrated calcium silicate, tobermorite, and ettringite generated by the reaction of calcareous materials and siliceous materials. Although carbonated aerated concrete belongs to the category of non-autoclaved aerated concrete, its strength mainly comes from calcium carbonate and silica gel generated by the reaction of carbonizable materials with carbon dioxide. Since the hydration product contains more gel pores, its apparent density is significantly lower than that of carbonization reaction products such as calcium carbonate and silica gel. Therefore, when the same mass of reaction products are generated, the volume of the hydration product is significantly higher than that of the carbonization product, and the contact between the hydration products is more sufficient, which is more conducive to the development of strength.

[0003] In order to improve the strength of carbonized aerated concrete, the current main research direction is to increase the amount of carbonizable materials in the mix design and put forward strict requirements on the mineral composition to ensure that enough carbonized products are generated during the curing process, and at the same time, a certain amount of hydraulic materials are used to ensure the normal hardening and molding of the green body. For example, patent CN113956070A discloses a cement kiln tail gas carbonized autoclave-free aerated concrete wall material product, the raw materials used include 5% to 10% silicate cement, 5% to 10% lime and 30% to 50% synthetic carbonized active cement. This solution requires the introduction of a relatively high amount of cement and lime, combined with a high amount of carbonized active cement, which not only increases the production cost, but also greatly increases the carbon dioxide emitted during the production process of its raw materials, which is not conducive to energy conservation and emission reduction. Summary of the invention

[0004] The main purpose of the present invention is to provide a carbonized aerated concrete with good light weight, high strength, thermal insulation performance and shrinkage performance under the premise of energy saving and emission reduction, in view of the problems and shortcomings of the prior art.

[0005] Another object of the present invention is to provide a method for preparing carbonized aerated concrete, which involves a simple curing method, is easy to operate, has a short preparation cycle, and is suitable for popularization and application.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A carbonized aerated concrete comprises raw materials and their weight proportions: 90-95 parts of steel slag, 5-10 parts of alkali activator, 25-30 parts of water, 0.05-0.1 parts of water reducing agent, 0.1-0.2 parts of α-olefin sodium sulfonate and 3-5 parts of aluminum sulfate solution.

[0008] In the above scheme, the main chemical composition and mass percentage of the steel slag include: C2S 40-60%, C3S5-15%, Ca(OH)2 0-1%, Ca2Fe2O5 0-20%, CaCO3 0-10%, SiO2 0-10%; specific surface area 350-650m 2 / kg.

[0009] In the above scheme, the alkali activator is preferably water glass, with a modulus of 2.0 to 2.5 and a concentration of 20 to 30 wt%.

[0010] In the above scheme, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent, and the water reduction rate is 35-45%.

[0011] In the above scheme, the effective component of the sodium α-olefin sulfonate is not less than 95wt%.

[0012] In the above scheme, the concentration of the aluminum sulfate solution is 20-25wt%.

[0013] The above-mentioned method for preparing carbonized aerated concrete comprises the following steps:

[0014] 1) Stir the steel slag, water reducing agent, alkali activator and water measured according to the proportion to obtain a clean slurry;

[0015] 2) stirring the clean slurry and sodium α-olefin sulfonate measured according to the ratio, and continuously introducing compressed air during stirring, and after the stirring is completed, a foam slurry is obtained;

[0016] 3) Under stirring conditions, the aluminum sulfate solution weighed according to the ratio is evenly added into the foam slurry, and the stirring process is continued to obtain a finished slurry;

[0017] 4) The obtained finished slurry is poured, allowed to harden by static gasification, demoulded, and a green body is obtained, and then carbonized and cured with carbon-containing gas to obtain a finished carbonized aerated concrete product.

[0018] Preferably, the stirring step in step 1) comprises: firstly stirring slowly at a speed of 60 to 120 r / min for 2 to 4 min, and then stirring quickly at a speed of 900 to 1200 r / min for 2 to 4 min.

[0019] In the above scheme, the stirring treatment in step 2) adopts a rotation speed of 200 to 500 r / min and a time of 5 to 10 min.

[0020] In the above scheme, in step 2), the rate of introduction of compressed air for each cubic meter of slurry (neat slurry) is 2 to 5 L / s.

[0021] In the above scheme, the air pressure of the compressed air is 0.2-0.3 MPa.

[0022] In the above scheme, the stirring rate used in step 3) is 90-150 r / min.

[0023] Furthermore, in step 3), the addition time of the aluminum sulfate solution is 45 to 60 seconds; and the stirring time after the addition is 90 to 120 seconds.

[0024] In the above scheme, the temperature used in the static gas hardening step is 45-55° C., the relative humidity is not less than 80%, and the static time is 3-4 hours.

[0025] In the above scheme, the carbonization curing step includes: first vacuuming to a vacuum degree of -0.04 to -0.06 MPa, then filling the kettle with carbon-containing gas until the pressure in the kettle is 0.3 to 0.5 MPa, and curing for 5 to 8 hours to obtain a carbonized aerated concrete product.

[0026] Furthermore, the carbon-containing gas has a temperature of 50-100° C., a carbon dioxide concentration of 10-100 vol%, and a relative humidity of 20-60%.

[0027] Furthermore, the carbon-containing gas includes but is not limited to cement kiln tail gas, metal smelter tail gas, etc., preferably with a temperature of 70-90° C., a carbon dioxide concentration of 20-50%, and a relative humidity of 30-40%.

[0028] The carbonized aerated concrete prepared according to the above scheme has a compressive strength of 3.5-4.5 MPa and a bulk density of 600-650 kg / m 3 The drying shrinkage is 0.21-0.26 mm / m, and the thermal conductivity is 0.11-0.13 W / (m·K).

[0029] The performance optimization mechanism of the carbonized aerated concrete of the present invention includes:

[0030] 1) The present invention firstly stirs steel slag, a water reducing agent, an alkali activator and water to obtain a clean slurry, then adds sodium α-olefin sulfonate for stirring, and introduces compressed air during the stirring process; the introduction of surface sodium α-olefin sulfonate can reduce the surface tension of water, and a large number of tiny bubbles can be formed by introducing compressed air into the clean slurry in combination with stirring conditions; in the obtained mixed system, the hydrophobic group of the surfactant is directional adsorbed to the air side, and the hydrophilic group is directional adsorbed to the water side, which is beneficial to increase the stability of the bubbles and maintain good foam stabilization performance in the mixed system that gradually releases a large amount of calcium ions; the stable existence of a large number of tiny bubbles can effectively reduce the sample bulk density and thermal conductivity, and reduce the stress concentration phenomenon at the pore wall when the obtained sample is subjected to force, which is beneficial to improve the performance.

[0031] 2) The calcium ions dissolved in the steel slag in the liquid phase react with aluminum sulfate to form hydration products such as calcium aluminate and calcium sulfonate, causing the slurry to coagulate rapidly, avoiding problems such as mold collapse and sinking caused by too long coagulation time, and solving the problem that the slurry is difficult to form in the absence of hydraulic materials (such as cement); in addition, the reaction product calcium sulfonate has a relatively obvious expansion effect, which can significantly reduce the drying shrinkage value of carbonized aerated concrete.

[0032] 3) Sodium α-olefin sulfonate forms lyotropic liquid crystals after dissolving in water, which have nano-sized hydrophilic regions. Since the hydrophilic groups of surfactants can strongly adsorb calcium ions in the liquid phase, the size of the carbonized product can be effectively reduced during the carbonization curing process, the specific surface area of ​​the carbonized product increases, and the mutual contact is more sufficient, which is conducive to improving the carbonization strength.

[0033] 4) Steel slag powder has a large specific surface area, and contains iron oxide, calcium oxide and other components with strong adsorption capacity on its surface. Water glass will form a negatively charged gel in the liquid phase and adsorb on the surface of steel slag, which is beneficial to reduce the adsorption of α-olefin sulfonate by steel slag and ensure the air entrainment effect during the molding process. In addition, aluminum ions will generate amphoteric hydroxide Al(OH)3 under alkaline conditions, and negatively charged calcium carbonate crystals will be generated during the carbonization process. Al(OH)3 is adsorbed on the surface of calcium carbonate crystals. Under the action of the charge, Al(OH)3 will adhere the negatively charged calcium carbonate crystals in a certain direction, and finally form chain-shaped and needle-shaped calcium carbonate, which is beneficial to the compressive strength and splitting tensile strength of carbonized aerated concrete.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The present invention uses industrial waste slag as the main raw material to prepare carbonized aerated concrete, with the amount of steel slag reaching more than 90%, and no cement needs to be introduced, which has a significant cost advantage and can also process a large amount of industrial waste.

[0036] 2) The present invention can effectively utilize carbon dioxide and heat in industrial waste gas during the curing process, which has significant economic and environmental benefits.

[0037] 3) The carbonized aerated concrete obtained by the present invention has good light weight, high strength, thermal insulation performance and shrinkage performance, and can provide a new idea for the preparation of high-performance aerated concrete. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the embodiments to facilitate a clearer understanding of the present invention, but they do not limit the present invention.

[0039] In the following examples and comparative examples, the main chemical composition of the steel slag used is C2S 56%, C3S 6%, Ca(OH)2 1%, Ca2Fe2O5 18%, CaCO3 8%, SiO2 9%; the specific surface area is 460m 2 / kg.

[0040] The alkali activator used is water glass, whose modulus is 2.0 and concentration is 25wt%.

[0041] The water reducing agent used is polycarboxylic acid water reducing agent, and its water reducing rate is 42%.

[0042] The α-olefin sodium sulfonate used was provided by Zhonghe Chemical (Shandong) Co., Ltd., and the active ingredient content was 96 wt%.

[0043] The aluminum sulfate solution used has a solid content (concentration) of 21 wt %, and an effective component content of 96 wt %.

[0044] Example 1

[0045] A carbonized aerated concrete, the preparation method of which comprises the following steps:

[0046] 1) Take 92 parts of steel slag, 8 parts of water glass, 0.1 parts of water reducer and 25 parts of water, stir slowly at 90r / min for 4 minutes, and then stir quickly at 900r / min for 2 minutes to obtain a clean slurry;

[0047] 2) The clean slurry and 0.1 part of sodium α-olefin sulfonate are stirred at a speed of 250 r / min for 5 min, and while stirring, 0.25 MPa compressed air is introduced at a rate of 3 L / s per cubic slurry to obtain a foam slurry after the stirring is completed;

[0048] 3) Under stirring conditions of 120 r / min, 4 parts of aluminum sulfate solution were evenly added to the foam slurry within 60 seconds, and stirring was continued for 120 seconds to obtain a finished slurry;

[0049] 4) Pour the obtained finished slurry into a mold frame and allow it to stand for hardening. The temperature in the standing room is 50° C. and the relative humidity is 85%. After standing for 3 hours, the slurry is hardened and demolded, and the green body is cut;

[0050] 5) Carrying out carbonization curing on the obtained green body, the specific steps include: first evacuating the body to a vacuum degree of -0.05MPa, then filling the kettle with carbon-containing gas until the pressure in the kettle is 0.4MPa, and curing for 8 hours to obtain a carbonized aerated concrete product; wherein the gas used for carbonization curing is cement kiln exhaust gas, the temperature is 75°C, the carbon dioxide concentration is 25vol%, and the relative humidity is 38%.

[0051] Example 2

[0052] A carbonized aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: in step 1), 92 parts of steel slag, 8 parts of water glass, 0.05 parts of water reducer, and 30 parts of water are taken, and the mixture is first slowly stirred at a speed of 90 r / min for 4 min, and then quickly stirred at a speed of 900 r / min for 2 min to obtain a pure slurry.

[0053] Example 3

[0054] A carbonized aerated concrete and a preparation method thereof, wherein the preparation method is substantially the same as that of Example 1, except that: in step 2), the clean slurry and 0.1 part of sodium α-olefin sulfonate are stirred at a speed of 500 r / min for 10 min, and while stirring, 0.25 MPa compressed air is introduced at a rate of 5 L / s per cubic meter of slurry, and foam slurry is obtained after the stirring is completed.

[0055] Comparative Example 1

[0056] A carbonized aerated concrete and a preparation method thereof, wherein the preparation method is substantially the same as that of Example 1, except that: under a stirring condition of 120 r / min, 4 parts of aluminum chloride solution (21 wt%) are uniformly added to the foam slurry within 60 s, and stirring is continued for 120 s to obtain the finished slurry.

[0057] Comparative Example 2

[0058] A carbonized aerated concrete and a preparation method thereof, wherein the preparation method is substantially the same as that of Example 1, except that: in step 2), the clean slurry and 0.1 part of sodium α-olefin sulfonate are stirred at a speed of 250 r / min for 5 min, and while stirring, 0.15 MPa compressed air is introduced at a rate of 3 L / s per cubic meter of slurry, and foam slurry is obtained after the stirring is completed.

[0059] Comparative Example 3

[0060] A carbonized aerated concrete and a preparation method thereof. The preparation method is substantially the same as that of Example 1, except that a fatty acid methyl ester sodium sulfate surfactant is used instead of the sodium α-olefin sulfonate of the present invention.

[0061] The carbonized aerated concrete obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was subjected to performance tests according to standard GB / T 11969-2008. The results are shown in Table 1.

[0062] Table 1 Carbonated aerated concrete performance test results

[0063]

[0064] The present invention is not limited to the above-mentioned embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A carbonized aerated concrete, characterized in that: The raw materials and their weight proportions include: 90-95 parts of steel slag, 5-10 parts of alkali activator, 25-30 parts of water, 0.05-0.1 parts of water reducing agent, 0.1-0.2 parts of sodium α-olefin sulfonate, and 3-5 parts of aluminum sulfate solution.

2. The carbonized aerated concrete according to claim 1, characterized in that: The main chemical components and their mass percentages in the steel slag include: C2S 40-60%, C3S 5-15%, Ca(OH)2 0-1%, Ca2Fe2O5 0-20%, CaCO3 0-10%, SiO2 0-10%; specific surface area 350-650m 2 / kg.

3. The carbonized aerated concrete according to claim 1, characterized in that: The alkaline activator is water glass, the modulus of which is 2.0-2.5 and the concentration is 20-30wt%.

4. The carbonized aerated concrete according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid high efficiency water reducing agent, and the water reducing rate is 35-45%.

5. The carbonized aerated concrete according to claim 1, characterized in that: The effective component of the sodium α-olefin sulfonate is not less than 95 wt %.

6. The carbonized aerated concrete according to claim 1, characterized in that: The concentration of the aluminum sulfate solution is 20-25 wt %.

7. The method for preparing carbonized aerated concrete according to any one of claims 1 to 6, characterized in that: The steps include: 1) Stir the steel slag, water reducing agent, alkali activator and water measured according to the proportion to obtain a clean slurry; 2) stirring the clean slurry and sodium α-olefin sulfonate measured according to the ratio, and continuously introducing compressed air during stirring, and after the stirring is completed, a foam slurry is obtained; 3) Under stirring conditions, the aluminum sulfate solution weighed according to the ratio is evenly added into the foam slurry, and the stirring process is continued to obtain a finished slurry; 4) The obtained finished slurry is poured, allowed to harden by static gasification, and demoulded to obtain a green body, which is then carbonized and cured using carbon-containing gas to obtain a finished carbonized aerated concrete product.

8. The preparation method according to claim 7, characterized in that: In step 2), the rate of introduction of compressed air per cubic meter of slurry is 2 to 5 L / s; the pressure of the compressed air is 0.2 to 0.3 MPa.

9. The preparation method according to claim 7, characterized in that: The carbonization curing step comprises: firstly evacuating the air to a vacuum degree of -0.04 to -0.06 MPa, then charging carbon-containing gas until the pressure in the kettle is 0.3 to 0.5 MPa, and curing for 5 to 8 hours to obtain a carbonized aerated concrete product.

10. The preparation method according to claim 7, characterized in that: The temperature of the carbon-containing gas is 50-100° C., the concentration of carbon dioxide is 10-100 vol%, and the relative humidity is 20-60%.

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