Green high performance mineral admixture for concrete and method of making

Abstract

The application provides a green high-performance mineral admixture for concrete and a preparation method, and belongs to the technical field of building materials. In the application, superfine converter slag and silica fume are used in combination, and in the case that sodium hydroxide, liquid water glass and sodium chloride are used as alkali activators, the formation of calcium silicate, a hydration product, is promoted, so that a cementing material is formed; meanwhile, PE fibers are used, so that the impermeability of the cementing material is improved; and by adding hydroxypropyl methyl cellulose in the formula, the obtained green high-performance mineral admixture is ensured to have a heavy metal elution amount when used in concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a green, high-performance mineral admixture for concrete and its preparation method. Background Technology

[0002] Converter slag, also known as converter steel slag, is a waste residue generated during the converter steelmaking process. It mainly comes from oxides formed after the oxidation of elements contained in molten iron and scrap steel, impurities brought in by the metal furnace charge, added slag-forming agents (such as limestone, fluorite, and silica), oxidants, desulfurization products, and corroded furnace lining materials, etc. It is a type of industrial waste.

[0003] In existing technologies, steelmaking processes in converters are typically combined with other industrial wastes and activated using activators to obtain cementitious materials, which are then used to prepare concrete admixtures to replace cement. However, experiments have shown that when these materials are used as the main raw material to prepare mineral admixtures for concrete, the maximum amount that can replace cement, while ensuring the compressive strength of the concrete and strictly controlling the leaching of heavy metals, is only about 30 wt%.

[0004] Therefore, there is an urgent need to provide a green, high-performance mineral admixture and its preparation method that can further increase the cement substitution rate while strictly controlling the amount of heavy metal leaching. Summary of the Invention

[0005] The purpose of this invention is to provide a green, high-performance mineral admixture for concrete and its preparation method. When used in concrete, the green, high-performance mineral admixture provided by this invention not only has the advantage of low heavy metal leaching, but also can replace up to 60 wt% of cement.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a green high-performance mineral admixture for concrete, comprising the following components in parts by weight: 50-90 parts of ultrafine converter slag, 10-15 parts of silica fume, 5-8 parts of sodium hydroxide, 8-15 parts of liquid water glass, 1-3 parts of sodium chloride, 3-8 parts of PE fiber, 0.1-0.5 parts of surfactant, and 0.1-0.5 parts of hydroxypropyl methylcellulose;

[0008] The specific surface area of ​​the ultrafine converter slag is >400m². 2 / kg, average particle size <20μm, D50<20μm, D90<35μm.

[0009] Preferably, the Fe2O3 content in the ultrafine converter slag is ≤1wt%.

[0010] Preferably, the modulus of the liquid water glass is 1.5 to 1.8.

[0011] Preferably, the surfactant comprises sodium dodecyl sulfate and / or sodium stearate.

[0012] Preferably, the surfactant is sodium dodecyl sulfate.

[0013] Preferably, the particle size of the silica fume is 0.1 to 1.0 μm.

[0014] Preferably, the PE fiber has the following specifications: length of 10-30 mm, diameter of 15-35 μm, aspect ratio of 650-750, and strength of 2500-3500 MPa.

[0015] Preferably, the green high-performance mineral admixture for concrete replaces 10-60 wt% of the cement required in the concrete.

[0016] The present invention also provides a method for preparing the green high-performance mineral admixture for concrete described in the above-mentioned scheme, comprising:

[0017] The ultrafine converter slag, silica fume, sodium hydroxide, liquid water glass, sodium chloride, PE fiber, surfactant and hydroxypropyl methylcellulose are mixed according to the required weight proportions to obtain a green high-performance mineral admixture for concrete.

[0018] Preferably, it includes the following steps:

[0019] (1) Mix ultrafine converter slag and silica fume to obtain mixture A;

[0020] (2) Sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain mixture B;

[0021] (3) Add the mixture B obtained in step (2) to the mixture A obtained in step (1), and then add PE fiber and hydroxypropyl methylcellulose to obtain a green high-performance mineral admixture for concrete;

[0022] The preparation of steps (1) and (2) is not in any particular order.

[0023] This invention provides a green, high-performance mineral admixture for concrete, comprising the following components in parts by weight: 50-90 parts ultrafine converter slag, 10-15 parts silica fume, 5-8 parts sodium hydroxide, 8-15 parts liquid water glass, 1-3 parts sodium chloride, 3-8 parts PE fiber, 0.1-0.5 parts surfactant, and 0.1-0.5 parts hydroxypropyl methylcellulose; wherein the specific surface area of ​​the ultrafine converter slag is >400 m². 2 / kg, average particle size <20μm, D50 <20μm, D90 <35μm. This invention utilizes ultrafine converter slag and silica fume in combination, with sodium hydroxide, liquid water glass, and sodium chloride as alkali activators, to further promote the formation of calcium silicate, a hydration product, thereby forming a cementitious material. Simultaneously, the use of PE fibers improves the impermeability of the gel material. Furthermore, the addition of hydroxypropyl methylcellulose to the formulation reduces the leaching of heavy metals from the obtained green high-performance mineral admixture when used in concrete. Experimental results show that the green high-performance mineral admixture provided by this invention, when used as a cement substitute in concrete preparation, not only has the advantage of low heavy metal leaching but also allows for a cement replacement dosage of up to 60wt%. Detailed Implementation

[0024] This invention provides a green high-performance mineral admixture for concrete, comprising the following components in parts by weight: 50-90 parts of ultrafine converter slag, 10-15 parts of silica fume, 5-8 parts of sodium hydroxide, 8-15 parts of liquid water glass, 1-3 parts of sodium chloride, 3-8 parts of PE fiber, 0.1-0.5 parts of surfactant, and 0.1-0.5 parts of hydroxypropyl methylcellulose.

[0025] Unless otherwise specified, the present invention does not have any special limitation on the source of the components, and commercially available products well known to those skilled in the art can be used.

[0026] The green high-performance mineral admixture for concrete provided by the present invention, by weight, includes 50 to 90 parts of ultrafine converter slag, preferably 55 to 85 parts.

[0027] In this invention, the specific surface area of ​​the ultrafine converter slag is >400 m². 2 / kg, average particle size <20μm, D50 <20μm, D90 <35μm. In this invention, the Fe2O3 content in the ultrafine converter slag is preferably ≤1wt%. This invention does not specify the source of the converter slag; waste slag collected during conventional converter steelmaking can be used. In this invention, the main chemical composition of the converter slag, by weight percentage, is preferably: SiO2 10.0-18.0%, Al2O3 1.0-5.0%, Fe2O3 2.5-12%, CaO 45.0-55.0%, MgO 5.0-1.0%, TiO2 0.85-3.85%, and the balance being impurities. In this invention, the preferred method for preparing the ultrafine converter slag is: first, grinding the converter slag to 0.1-1mm, removing the middle iron in the converter slag by magnetic separation to achieve an iron content ≤1wt%, and then further grinding to obtain a specific surface area >400m². 2The present invention yields ultrafine converter slag with an average particle size of <20 μm, D50 <20 μm, and D90 <35 μm per kg. This invention controls the iron content in the converter slag to ≤1 wt%, which facilitates subsequent grinding and thus obtains ultrafine converter slag. In this invention, the specific surface area of ​​the ultrafine converter slag is preferably 400–500 m² / kg. 2 / kg, average particle size <20μm, D50 <20μm, D90 <35μm. Due to the high hardness of converter slag, further refining it places significant demands on equipment and causes considerable wear. Therefore, from a comprehensive economic perspective, in actual operation, this invention only requires grinding the converter slag to the above specifications. In this invention, the ultrafine converter slag possesses high activity and fluidity, which can fill the fine pores in concrete and improve its density.

[0028] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 10-15 parts, preferably 8-15 parts, of silica fume. In this invention, the particle size of the silica fume is 0.1-1.0 μm. This invention promotes the formation of calcium silicate, a hydration product, under the activation of an alkali activator by using ultrafine converter slag and silica fume in combination, thereby forming a cementitious material.

[0029] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 5-8 parts, preferably 6-8 parts, of sodium hydroxide. In this invention, the sodium hydroxide acts as an alkali activator, which can accelerate the hydration reaction and improve the early strength of concrete.

[0030] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 8-15 parts, preferably 9-15 parts, of liquid water glass. In this invention, the modulus of the liquid water glass is preferably 1.5-1.8. By selecting liquid water glass with the above-mentioned modulus and Baume degree as an alkali activator, this invention achieves a better activating effect on ultrafine converter slag, resulting in better early and late-stage strength in concrete applications.

[0031] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 1-3 parts, preferably 2-3 parts, of sodium chloride. In this invention, by adding a small amount of sodium chloride to the common alkali activator sodium hydroxide and liquid water glass, not only is the early and late compressive strength of concrete obtained by replacing cement with alkali-activated green ultrafine high-performance composite admixture improved, but the leaching of heavy metal cadmium ions is also reduced.

[0032] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 3-8 parts, preferably 4-8 parts, of PE fiber. In this invention, the preferred specifications of the PE fiber are: length 10-30 mm, diameter 15-35 μm, aspect ratio 650-750, and strength 2500-3500 MPa. By selecting PE fibers of the above specifications, this invention not only improves the compressive strength of concrete but also enhances its impermeability, thereby achieving controllable heavy metal leaching at higher strength.

[0033] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 0.1-0.5 parts, preferably 0.2-0.5 parts, of surfactant. In this invention, the surfactant preferably includes sodium dodecyl sulfate and / or sodium stearate, more preferably sodium dodecyl sulfate. By adding surfactant to the raw materials, this invention not only increases the strength of concrete but also further reduces the leaching of heavy metals.

[0034] Based on 50-90 parts by weight of ultrafine converter slag, the green high-performance mineral admixture for concrete provided by this invention includes 0.1-0.5 parts of hydroxypropyl methylcellulose, preferably 0.2-0.5 parts. By adding hydroxypropyl methylcellulose to the formulation, this invention ensures the reduction of heavy metal leaching during the use of the obtained green high-performance mineral admixture in concrete.

[0035] Preferably, the green high-performance mineral admixture for concrete replaces 10-60 wt% of the cement required in the concrete.

[0036] The green high-performance mineral admixture for concrete provided by this invention further promotes the formation of calcium silicate, a hydration product, by using ultrafine converter slag and silica fume in combination, with sodium hydroxide, liquid water glass and sodium chloride as alkali activators, thereby forming a cementitious material. At the same time, the use of PE fiber improves the impermeability of the gel material. Furthermore, by adding hydroxypropyl methylcellulose to the formula, the leaching of heavy metals when the obtained green high-performance mineral admixture is used in concrete is also reduced.

[0037] The present invention also provides a method for preparing the green high-performance mineral admixture for concrete described in the above-mentioned scheme, comprising:

[0038] The ultrafine converter slag, silica fume, sodium hydroxide, liquid water glass, sodium chloride, PE fiber, surfactant and hydroxypropyl methylcellulose are mixed according to the required weight proportions to obtain a green high-performance mineral admixture for concrete.

[0039] In this invention, the method for preparing the green high-performance mineral admixture for concrete preferably includes the following steps:

[0040] (1) Mix ultrafine converter slag and silica fume to obtain mixture A;

[0041] (2) Sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain mixture B;

[0042] (3) Add the mixture B obtained in step (2) to the mixture A obtained in step (1), and then add PE fiber and hydroxypropyl methylcellulose to obtain a green high-performance mineral admixture for concrete;

[0043] The preparation of steps (1) and (2) is not in any particular order.

[0044] By selecting the above-mentioned feeding sequence, the present invention obtains a green high-performance mineral admixture for concrete. When used in concrete, the resulting concrete exhibits good compressive strength and low heavy metal leaching.

[0045] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] In each embodiment: the specific surface area of ​​the ultrafine converter slag is 400-500 m². 2 / kg, average particle size <20μm, D50<20μm, D90<35μm; silica fume particle size is 0.1~1.0μm; liquid water glass modulus is 1.6; PE fiber specifications are: length 15~18mm, diameter 20~22μm, aspect ratio 720~750, strength 3000~3100MP.

[0047] Example 1

[0048] The green high-performance mineral admixture used in concrete in this embodiment consists of the following components in parts by weight: 80 parts ultrafine converter slag, 13 parts silica fume, 7 parts sodium hydroxide, 13 parts liquid water glass, 2 parts sodium chloride, 7 parts PE fiber, 0.4 parts sodium dodecyl sulfate, and 0.4 parts hydroxypropyl methylcellulose.

[0049] The preparation method of the green high-performance mineral admixture for concrete is as follows:

[0050] (1) Mix ultrafine converter slag and silica fume to obtain mixture A;

[0051] (2) Sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain mixture B;

[0052] (3) Add the mixture B obtained in step (2) to the mixture A obtained in step (1), and then add PE fiber and hydroxypropyl methylcellulose to obtain a green high-performance mineral admixture for concrete.

[0053] Example 2

[0054] The only difference from Example 1 is that the weight composition of the raw materials used is as follows: 50 parts of ultrafine converter slag, 10 parts of silica fume, 5 parts of sodium hydroxide, 8 parts of liquid water glass, 1 part of sodium chloride, 3 parts of PE fiber, 0.1 parts of sodium dodecyl sulfate and 0.1 parts of hydroxypropyl methylcellulose.

[0055] Example 3

[0056] The only difference from Example 1 is that the weight composition of the raw materials used is as follows: 90 parts of ultrafine converter slag, 15 parts of silica fume, 8 parts of sodium hydroxide, 15 parts of liquid water glass, 3 parts of sodium chloride, 8 parts of PE fiber, 0.5 parts of sodium dodecyl sulfate and 0.5 parts of hydroxypropyl methylcellulose.

[0057] Comparative Example 1

[0058] The only difference from Example 1 is that silica fume is replaced with ultrafine converter slag; all other aspects are the same as in Example 1.

[0059] Comparative Example 2

[0060] The only difference from Example 1 is that the PE fiber is omitted; otherwise, they are the same as in Example 1.

[0061] Comparative Example 3

[0062] The only difference from Example 1 is that hydroxypropyl methylcellulose is omitted; otherwise, they are the same as in Example 1.

[0063] Concrete was prepared using the alkali-activated green ultrafine high-performance composite admixtures provided in Examples 1-3 and Comparative Examples 1-3, respectively, and its performance was tested.

[0064] In the experiment, the control group: the concrete consisted of the following components by weight: 300 parts of P.O42.5 cement, 80 parts of fly ash, 1000 parts of 5-16 continuously graded crushed stone, 600 parts of river sand with an average particle size of 0.3-0.5 mm, 166 parts of water, and 4.5 parts of polycarboxylate-based high-efficiency water-reducing agent.

[0065] Application Example 1

[0066] The concrete is composed of the following components by weight: 120 parts P.O42.5 cement, 180 parts green high-performance mineral admixture provided in Example 1, 80 parts fly ash, 1000 parts 5-16 continuously graded crushed stone, 600 parts river sand with an average particle size of 0.3-0.5 mm, 166 parts water, and 4.5 parts polycarboxylate-based high-efficiency water-reducing agent. The green high-performance mineral admixture replaces 60 wt% of the cement required in the concrete.

[0067] Application Example 2

[0068] The only difference from Application Example 1 is the change of the following raw materials: 270 parts of P.O42.5 cement and 30 parts of the green high-performance mineral admixture provided in Example 1; all other materials are the same as in Application Example 1. The green high-performance mineral admixture replaces 10 wt% of the cement required in the concrete.

[0069] Application Example 3

[0070] The only difference from Application Example 1 is the change of the following raw materials: 180 parts of P.O42.5 cement and 120 parts of the green high-performance mineral admixture provided in Example 1; all other materials are the same as in Application Example 1. The green high-performance mineral admixture replaces 40 wt% of the cement required in the concrete.

[0071] Application Example 4

[0072] The only difference from Application Example 1 is the change of the following raw materials: 105 parts of P.O42.5 cement and 195 parts of the green high-performance mineral admixture provided in Example 1; all other materials are the same as in Application Example 1. The green high-performance mineral admixture replaces 65 wt% of the cement required in the concrete.

[0073] Application Example 5

[0074] The only difference from Application Example 1 is the change of the following raw materials: 90 parts of P.O42.5 cement and 210 parts of the green high-performance mineral admixture provided in Example 1; all other materials are the same as in Application Example 1. The green high-performance mineral admixture replaces 70 wt% of the cement required in the concrete.

[0075] Application Examples 6-10

[0076] The only difference between Application Examples 6-10 and Application Example 1 is that the raw material green high-performance mineral admixture is replaced with the green high-performance mineral admixtures provided in Examples 2-3 and Comparative Examples 1-3, respectively.

[0077] The compressive strength of concrete provided in test cases 1 to 10 of the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2011) was tested at 3d, 7d and 28d. The test results are shown in Table 1.

[0078] Table 1 shows the concrete compressive strength test results provided in Application Examples 1-10.

[0079]

[0080] As can be seen from Table 1, when the amount of green high-performance mineral admixtures that replace cement does not exceed 60 wt% (Application Examples 1-5), the resulting concrete has comparable early and late strengths to P.O42.5 cement, and even exceeds P.O42.5 cement when the replacement amount is small. As can be seen from Application Examples 8-10, omitting any one of silica fume, silica fume, or hydroxypropyl methylcellulose in the formula leads to a decrease in concrete strength.

[0081] The heavy metal leaching content of the obtained concrete was tested according to the test method in Appendix A of GB5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification". The test results are shown in Table 2.

[0082] Table 2 shows the test results of heavy metal leaching from concrete provided in Application Examples 1-10.

[0083]

[0084]

[0085] As can be seen from Table 2, when hydroxypropyl methylcellulose is omitted (Application Example 9), the leaching of heavy metals lead, cadmium, and chromium increases compared to before replacing P.O42.5 cement.

[0086] In summary, when the green high-performance mineral admixture provided by this invention is used to replace cement, it not only reduces the leaching of heavy metals such as lead, cadmium, and chromium, but also allows for the replacement of up to 60 wt% of cement. Therefore, the green high-performance mineral admixture provided by this invention has the advantages of being green and environmentally friendly.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A green, high-performance mineral admixture for concrete, comprising the following components in parts by weight: The ingredients are: 50-90 parts ultrafine converter slag, 10-15 parts silica fume, 5-8 parts sodium hydroxide, 8-15 parts liquid water glass, 2-3 parts sodium chloride, 3-8 parts PE fiber, 0.1-0.5 parts surfactant and 0.1-0.5 parts hydroxypropyl methylcellulose; The specific surface area of ​​the ultrafine converter slag is >400m². 2 / kg, average particle size <20μm, D50<20μm, D90<35μm; the surfactant is sodium dodecyl sulfate.

2. The green high-performance mineral admixture for concrete according to claim 1, characterized in that, The Fe2O3 content in the ultrafine converter slag is ≤1wt%.

3. The green high-performance mineral admixture for concrete according to claim 1, characterized in that, The modulus of the liquid water glass is 1.5 to 1.

8.

4. The green high-performance mineral admixture for concrete according to claim 1, characterized in that, The particle size of the silica fume is 0.1~1.0μm.

5. The green high-performance mineral admixture for concrete according to claim 1, characterized in that, The specifications of the PE fiber are: length 10~30mm, diameter 15~35μm, aspect ratio 650~750, and strength 2500~3500MPa.

6. The green high-performance mineral admixture for concrete according to claim 1, characterized in that, The green high-performance mineral admixtures used in concrete replace 10-60 wt% of the cement required in concrete.

7. The method for preparing the green high-performance mineral admixture for concrete according to any one of claims 1 to 6, comprising: The ultrafine converter slag, silica fume, sodium hydroxide, liquid water glass, sodium chloride, PE fiber, surfactant and hydroxypropyl methylcellulose are mixed according to the required weight proportions to obtain a green high-performance mineral admixture for concrete.

8. The preparation method according to claim 7, characterized in that, Includes the following steps: (1) Mix ultrafine converter slag and silica fume to obtain mixture A; (2) Sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain mixture B; (3) Add the mixture B obtained in step (2) to the mixture A obtained in step (1), and then add PE fiber and hydroxypropyl methylcellulose to obtain a green high-performance mineral admixture for concrete; The preparation of steps (1) and (2) is not in any particular order.

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