Alkali-activated green superfine high-performance composite admixture, preparation method and application thereof

Abstract

The application provides an alkali-activated green superfine high-performance composite admixture, a preparation method and application, and belongs to the technical field of building materials. The alkali-activated green superfine high-performance composite admixture is obtained by selecting superfine converter slag as a main component, using a specific alkali-activator for activation, and using a surfactant. When the alkali-activated green superfine high-performance composite admixture is used to replace cement to prepare concrete, the early and later compressive strength of the concrete can be ensured, the heavy metal dissolution amount is lower, and the green environmental protection requirement of the contemporary industry on the concrete admixture is met.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to an alkali-activated green ultrafine high-performance composite admixture, its preparation method, and its application. 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] Current technologies typically combine converter steelmaking with other industrial waste, using activators to obtain cementitious materials to prepare concrete admixtures as a substitute for cement. However, existing technologies using converter slag usually only focus on the mechanical properties of the resulting concrete, without in-depth research on the leaching of heavy metals. With the increasing number of urban buildings, the consumption of building materials has also increased significantly. Concrete is a common raw material in building materials, and high levels of heavy metal leaching will pose a significant threat to the environment.

[0004] Therefore, there is an urgent need to provide an alkali-activated green ultrafine high-performance composite admixture with excellent mechanical properties and low heavy metal leaching, as well as its preparation method and application. Summary of the Invention

[0005] The purpose of this invention is to provide an alkali-activated green ultrafine high-performance composite admixture, its preparation method, and its application. The alkali-activated green ultrafine high-performance composite admixture provided by this invention not only has the advantage of partially replacing cement but also has the advantage of low heavy metal leaching.

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

[0007] This invention provides an alkali-activated green ultrafine high-performance composite admixture, comprising the following components in parts by weight: 50-90 parts ultrafine converter slag, 2-5 parts sodium hydroxide, 5-8 parts liquid water glass, 1-3 parts sodium chloride, and 0.1-0.5 parts surfactant.

[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 in the alkali-activated green ultrafine high-performance composite admixture is sodium dodecyl sulfate.

[0013] This invention provides a method for preparing the alkali-activated green ultrafine high-performance composite admixture described above, comprising:

[0014] Mix ultrafine converter slag, sodium hydroxide, liquid water glass, sodium chloride, and surfactant according to the required amount to obtain alkali-activated green ultrafine high-performance composite admixture.

[0015] Preferably, the mixing method is as follows: first, sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain a mixed system, and then the mixed system is added to the ultrafine converter slag.

[0016] The present invention also provides the application of the alkali-activated green ultrafine high-performance composite admixture described in the above-described scheme or the alkali-activated green ultrafine high-performance composite admixture prepared by the preparation method described in the above-described scheme in concrete.

[0017] Preferably, the alkali-activated green ultrafine high-performance composite admixture replaces 10-30 wt% of the cement required in concrete.

[0018] This invention provides an alkali-activated green ultrafine high-performance composite admixture, comprising the following components in parts by weight: 50-90 parts ultrafine converter slag, 2-5 parts sodium hydroxide, 5-8 parts liquid water glass, 1-3 parts sodium chloride, and 0.1-0.5 parts surfactant; 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 selects ultrafine converter slag with a high surface area as the main component. Due to its ultrafine particle size structure, it also has good fluidity. When applied to concrete, it can fill the fine pores in the concrete and improve the compactness of the concrete. By compounding sodium hydroxide, liquid water glass, and sodium chloride as alkali activators, this invention not only improves the early and late compressive strength of concrete obtained by replacing cement with alkali-activated green ultrafine high-performance composite admixture, but also reduces the leaching of heavy metal cadmium ions. This invention further reduces the leaching of heavy metals by adding surfactants to the formula. Experimental results show that when the alkali-activated green ultrafine high-performance composite admixture provided by this invention is used to replace cement to prepare concrete, the resulting concrete not only has high compressive strength, but also has the advantage of low heavy metal leaching. Detailed Implementation

[0019] This invention provides an alkali-activated green ultrafine high-performance composite admixture, comprising the following components in parts by weight: 50-90 parts ultrafine converter slag, 2-5 parts sodium hydroxide, 5-8 parts liquid water glass, 1-3 parts sodium chloride, and 0.1-0.5 parts surfactant.

[0020] 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.

[0021] The alkali-activated green ultrafine high-performance composite admixture provided by this invention, by weight, comprises 50-90 parts of ultrafine converter slag. 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%. 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 preparation method of the ultrafine converter slag is: first, the converter slag is ground to 0.1-1mm, and the iron in the converter slag is removed by magnetic separation to achieve an iron content ≤1wt%, and then further ground to obtain a specific surface area >400m². 2 The present invention yields ultrafine converter slag with an average particle size of <20μm, D50 <20μm, and D90 <35μm per kg. This invention controls the iron content in the converter slag to ≤1wt%, 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.

[0022] Based on 50-90 parts by weight of ultrafine converter slag, the alkali-activated green ultrafine high-performance composite admixture provided by this invention includes 2-5 parts, preferably 3-5 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.

[0023] Based on 50-90 parts by weight of ultrafine converter slag, the alkali-activated green ultrafine high-performance composite admixture provided by this invention includes 5-8 parts, preferably 6-8 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 as an alkali activator, this invention achieves a better activation effect on ultrafine converter slag, resulting in better early and late-stage strength in concrete applications.

[0024] Based on 50-90 parts by weight of ultrafine converter slag, the alkali-activated green ultrafine high-performance composite admixture 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 the alkali-activated green ultrafine high-performance composite admixture improved, but the leaching of heavy metal cadmium ions is also reduced.

[0025] Based on 50-90 parts by weight of ultrafine converter slag, the alkali-activated green ultrafine high-performance composite admixture provided by this invention includes 0.1-0.5 parts, preferably 0.2-0.4 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.

[0026] The alkali-activated green ultrafine high-performance composite admixture provided by this invention selects ultrafine converter slag with a high surface area as the main component, activates it under the action of a specific alkali activator, and uses surfactants to obtain an alkali-activated green ultrafine high-performance composite admixture that can not only improve the early and late compressive strength of concrete but also has the advantage of low heavy metal leaching.

[0027] This invention provides a method for preparing the alkali-activated green ultrafine high-performance composite admixture described above, comprising:

[0028] Mix ultrafine converter slag, sodium hydroxide, liquid water glass, sodium chloride, and surfactant according to the required amount to obtain alkali-activated green ultrafine high-performance composite admixture.

[0029] In this invention, the preferred mixing method is to first mix sodium hydroxide, liquid water glass, sodium chloride, and a surfactant to obtain a mixed system, and then add the mixed system to the ultrafine converter slag. This invention, through the above mixing method, can achieve simultaneous and thorough mixing of materials into the ultrafine converter slag, and the resulting alkali-activated green ultrafine high-performance composite admixture, when applied to concrete, exhibits good concrete mechanical properties and heavy metal leaching effects.

[0030] The present invention also provides the application of the alkali-activated green ultrafine high-performance composite admixture described in the above-described scheme or the alkali-activated green ultrafine high-performance composite admixture prepared by the preparation method described in the above-described scheme in concrete.

[0031] In this invention, the alkali-activated green ultrafine high-performance composite admixture preferably replaces 10-30 wt% of the cement required in concrete. By limiting the amount of the alkali-activated green ultrafine high-performance composite admixture within the above range, the resulting alkali-activated green ultrafine high-performance composite admixture, when applied to concrete, exhibits better concrete mechanical properties and heavy metal leaching effects.

[0032] 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.

[0033] 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; the modulus of liquid water glass is 1.6.

[0034] Example 1

[0035] In this embodiment, the alkali-activated green ultrafine high-performance composite admixture is composed of the following components in parts by weight: 80 parts ultrafine converter slag, 3 parts sodium hydroxide, 6 parts liquid water glass, 2 parts sodium chloride, and 0.2 parts sodium dodecyl sulfate.

[0036] The preparation method of the alkali-activated green ultrafine high-performance composite admixture is as follows:

[0037] Sodium hydroxide, liquid water glass, sodium chloride and sodium dodecyl sulfate are first mixed to obtain a mixed system. Then the mixed system is added to ultrafine converter slag to obtain alkali-activated green ultrafine high-performance composite admixture.

[0038] Example 2

[0039] In this embodiment, the alkali-activated green ultrafine high-performance composite admixture is composed of the following components in parts by weight: 50 parts ultrafine converter slag, 2 parts sodium hydroxide, 5 parts liquid water glass, 1 part sodium chloride, and 0.1 parts sodium dodecyl sulfate.

[0040] The preparation method of the alkali-activated green ultrafine high-performance composite admixture is as follows:

[0041] Sodium hydroxide, liquid water glass, sodium chloride and sodium dodecyl sulfate are first mixed to obtain a mixed system. Then the mixed system is added to ultrafine converter slag to obtain alkali-activated green ultrafine high-performance composite admixture.

[0042] Example 3

[0043] In this embodiment, the alkali-activated green ultrafine high-performance composite admixture is composed of the following components in parts by weight: 90 parts ultrafine converter slag, 5 parts sodium hydroxide, 8 parts liquid water glass, 3 parts sodium chloride, and 0.5 parts sodium dodecyl sulfate.

[0044] The preparation method of the alkali-activated green ultrafine high-performance composite admixture is as follows:

[0045] Sodium hydroxide, liquid water glass, sodium chloride and sodium dodecyl sulfate are first mixed to obtain a mixed system. Then the mixed system is added to ultrafine converter slag to obtain alkali-activated green ultrafine high-performance composite admixture.

[0046] Comparative Example 1

[0047] The only difference from Example 1 is that sodium chloride is replaced with sodium carbonate; otherwise, they are the same as in Example 1.

[0048] Comparative Example 2

[0049] The only difference from Example 1 is that sodium dodecyl sulfate is omitted; otherwise, they are the same as in Example 1.

[0050] Comparative Example 3

[0051] The only difference from Example 1 is that sodium chloride is omitted; otherwise, they are the same as in Example 1.

[0052] Concrete was prepared using the alkali-activated green ultrafine high-performance composite admixtures provided in Examples 1-3 and Comparative Examples 1-3, and its performance was tested.

[0053] 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 5-16mm continuously graded crushed stone, 600 parts of river sand with an average particle size of 0.3-0.5mm, 166 parts of water, and 4.5 parts of polycarboxylate-based high-efficiency water-reducing agent.

[0054] Application Example 1

[0055] The concrete is composed of the following components by weight: 210 parts P.O42.5 cement, 90 parts alkali-activated green ultrafine high-performance composite admixture provided in Example 1, 80 parts fly ash, 1000 parts 5-16mm continuously graded crushed stone, 600 parts river sand with an average particle size of 0.3-0.5mm, 166 parts water, and 4.5 parts polycarboxylate-based high-efficiency water-reducing agent. In this case, the alkali-activated green ultrafine high-performance composite admixture replaces 30 wt% of the cement.

[0056] Application Example 2

[0057] 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 alkali-activated green ultrafine high-performance composite admixture provided in Example 1; the rest are the same as in Application Example 1. In this case, the alkali-activated green ultrafine high-performance composite admixture replaces 10 wt% of the cement.

[0058] Application Example 3

[0059] The only difference from Application Example 1 is the change of the following raw materials: 240 parts of P.O42.5 cement and 60 parts of the alkali-activated green ultrafine high-performance composite admixture provided in Example 1; the rest are the same as in Application Example 1. In this case, the alkali-activated green ultrafine high-performance composite admixture replaces 20 wt% of the cement.

[0060] Application Example 4

[0061] The only difference from Application Example 1 is the change of the following raw materials: 195 parts of P.O42.5 cement and 105 parts of the alkali-activated green ultrafine high-performance composite admixture provided in Example 1; all other materials are the same as in Application Example 1. In this case, the alkali-activated green ultrafine high-performance composite admixture replaces 35 wt% of the cement.

[0062] Application Example 5

[0063] 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 alkali-activated green ultrafine high-performance composite admixture provided in Example 1; all other materials are the same as in Application Example 1. In this case, the alkali-activated green ultrafine high-performance composite admixture replaces 40 wt% of the cement.

[0064] Application Examples 6-10

[0065] The only difference between Application Examples 6-10 and Application Example 1 is that the alkali-activated green ultrafine high-performance composite admixture is replaced with the alkali-activated green ultrafine high-performance composite admixture provided in Examples 2-3 and Comparative Examples 1-3, respectively.

[0066] 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.

[0067] Table 1 shows the concrete compressive strength test results provided in Application Examples 1-10.

[0068]

[0069] As shown in Table 1, when the amount of alkali-activated green ultrafine high-performance composite admixture replacing cement does not exceed 30 wt%, the resulting concrete has strength comparable to P.O42.5 cement in both early and late stages. It can also be seen that omitting either sodium chloride or sodium dodecyl sulfate in the formula leads to a decrease in concrete strength. However, as shown in Application Example 8, when sodium chloride is replaced by sodium carbonate, the early and late stages of concrete strength even exceed those of cement.

[0070] 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.

[0071] Table 2 shows the test results of heavy metal leaching from concrete provided in Application Examples 1-10.

[0072]

[0073] As shown in Table 2, omitting sodium chloride or sodium dodecyl sulfate resulted in an increase in the leaching of heavy metals lead, cadmium, and chromium compared to before replacing P.O42.5 cement. Combined with Table 1, it can be seen that although replacing sodium chloride with sodium carbonate improves cement strength, the leaching of heavy metals increased. This may be because the leaching of heavy metals is related not only to cement strength but also to the substances ultimately formed in the activating system; specific material compositions exert a binding effect on heavy metals.

[0074] In summary, when the alkali-activated green ultrafine high-performance composite admixture provided by this invention replaces cement, the resulting concrete not only exhibits better compressive strength but also reduces the leaching of heavy metals such as lead, cadmium, and chromium. Therefore, the alkali-activated green ultrafine high-performance composite admixture provided by this invention has the advantages of being green and environmentally friendly.

[0075] 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. An alkali-activated green ultrafine high-performance composite admixture, comprising the following components in parts by weight: 50-90 parts ultrafine converter slag, 2-5 parts sodium hydroxide, 5-8 parts liquid water glass, 1-3 parts sodium chloride, and 0.1-0.5 parts surfactant; The specific surface area of ​​the ultrafine converter slag is >400m². 2 / kg, average particle size <20μm, D50<20μm, D90<35μm; The Fe2O3 content in the ultrafine converter slag is ≤1wt%. The modulus of the liquid water glass is 1.5 to 1.8; The surfactant includes sodium dodecyl sulfate.

2. The preparation method of the alkali-activated green ultrafine high-performance composite admixture according to claim 1, comprising: Mix ultrafine converter slag, sodium hydroxide, liquid water glass, sodium chloride, and surfactant according to the required amount to obtain alkali-activated green ultrafine high-performance composite admixture.

3. The preparation method according to claim 2, characterized in that, The specific mixing method is as follows: first, sodium hydroxide, liquid water glass, sodium chloride and surfactant are mixed to obtain a mixed system, and then the mixed system is added to the ultrafine converter slag.

4. The application of the alkali-activated green ultrafine high-performance composite admixture according to claim 1 or the alkali-activated green ultrafine high-performance composite admixture prepared according to any one of claims 2 to 3 in concrete.

5. The application according to claim 4, characterized in that, The alkali-activated green ultrafine high-performance composite admixture replaces 10-30 wt% of the cement required in concrete.

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