Composite portland cement, method for its production and use

Abstract

The application discloses a composite Portland cement and a preparation method and application thereof. The preparation method of the composite Portland cement comprises the following steps: dispersing an additive in water, spraying the additive into nano fillers, adding low-activity solid waste powder, uniformly mixing, drying, adding the Portland cement into a ball mill together with the low-activity solid waste powder, ball milling, and obtaining the composite Portland cement. The water demand, setting time and mechanical properties of the composite Portland cement are not influenced under the condition that a large amount of low-activity solid waste is added, the low-activity solid waste can be well reused and treated, and the composite Portland cement is suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a composite silicate cement, its preparation method, and its application. Background Technology

[0002] The construction industry inevitably generates a large amount of solid waste, making its recycling and disposal technologies crucial. Highly reactive solid waste is easy to utilize and has high recycling value, and has already been processed into various industrial products (for example, the pozzolanic activity of most blast furnace slag is high, and it is usually ground finely and used as a mineral admixture to directly replace clinker or cement in the production of cement-based materials). In contrast, the pozzolanic activity of low-reactivity solid waste is low, and when used in cement-based materials, it typically only serves as a filler, leading to a significant decrease in the strength of the cement-based materials. Currently, ultrafine grinding is generally used to improve the activity of low-reactivity solid waste; however, ultrafine grinding consumes too much energy, and the powder produced from low-reactivity solid waste through ultrafine grinding also significantly increases the water demand of cement-based materials. Ultimately, this results in a low content of low-reactivity solid waste in cement-based materials, which is detrimental to the reuse and disposal of low-reactivity solid waste. Summary of the Invention

[0003] The purpose of this invention is to provide a composite silicate cement, its preparation method, and its application.

[0004] The technical solution adopted in this invention is:

[0005] A method for preparing composite silicate cement includes the following steps:

[0006] The additives are dispersed in water and then sprayed into the nanofiller. Low-activity solid waste powder is added and mixed evenly. After drying, it is added to a ball mill along with silicate cement and then ball-milled to obtain composite silicate cement.

[0007] Preferably, the mass ratio of the admixture, water, nanofiller, low-activity solid waste powder, and silicate cement is 0.01-1:10:1-3:40-60:37-59.

[0008] Preferably, the admixture is at least one of polycarboxylic acid water-reducing agents, alkanolamine compounds, chloride salts, and alkali metal salts.

[0009] More preferably, the additive is a complex of an alcohol amine compound and an alkali metal salt.

[0010] Preferably, the alkanolamine compound is at least one selected from triethanolamine, triisopropanolamine, diethanolamine, and N-methyldiethanolamine.

[0011] Preferably, the alkali metal salt is at least one selected from sodium sulfate, potassium aluminum sulfate, sodium carbonate, and sodium acetate.

[0012] Preferably, the nanofiller is at least one of nano-silica, nano-calcium carbonate, and nano-metakaolin.

[0013] Preferably, the particle size of the nano-silica is 15nm to 50nm.

[0014] Preferably, the SiO2 content of the nano-silica is ≥99.5%.

[0015] Preferably, the particle size of the nano-calcium carbonate is 10 nm to 100 nm.

[0016] Preferably, the particle size of the nano-kaolin is 50nm to 100nm.

[0017] Preferably, the low-activity solid waste powder is at least one of low-calcium fly ash, nickel-iron slag, limestone powder, and waste brick powder.

[0018] Preferably, the low-calcium fly ash has a CaO content of ≤4%, a spherical particle ratio of >80%, and a specific surface area of ​​≥400 m². 2 / kg, 7d activity index ≤70%, 28d activity index ≤80%.

[0019] Preferably, the nickel-iron slag is at least one of electric furnace nickel-iron slag and blast furnace nickel-iron slag, with a specific surface area ≥ 400 m². 2 / kg, 7d activity index ≤70%, 28d activity index ≤80%.

[0020] Preferably, the specific surface area of ​​the limestone powder is ≥400m². 2 / kg, 7d activity index ≤70%, 28d activity index ≤80%.

[0021] Preferably, the specific surface area of ​​the waste brick powder is ≥400m². 2 / kg, 7d activity index ≤65%, 28d activity index ≤75%.

[0022] Preferably, the mixing equipment used for mixing is at least one of a fluidized bed mixer, a V-type mixer, and a vertical mixer.

[0023] Preferably, the ball milling time is 5 min to 30 min.

[0024] A composite silicate cement, which is prepared by the above-described method.

[0025] A cement-based material comprising the aforementioned composite silicate cement.

[0026] The beneficial effects of the present invention are: the composite silicate cement of the present invention does not affect its water demand, setting time and mechanical properties when a large amount of low-activity solid waste is added, and can effectively realize the reuse and treatment of low-activity solid waste, making it suitable for large-scale promotion and application.

[0027] Specifically:

[0028] 1) This invention utilizes the filling and nucleation effect of nanofillers to improve the initial bulk density of composite cement, increase the free water content and particle coordination number, reduce water demand while providing more active sites, accelerate the hydration reaction rate, and only require a small amount of hydration products to achieve setting and hardening. Therefore, it is not necessary to deliberately increase the specific surface area of ​​low-activity solid waste, avoid the high energy consumption caused by excessive grinding, and reduce the problem of strength reduction caused by the large introduction of low-activity solid waste in the early stage. The early strength of the obtained composite silicate cement can reach more than 85% of that of ordinary silicate cement.

[0029] 2) This invention fully utilizes the skeletal role of low-activity solid waste. Cement particles and nanofillers fill the gaps between the particles of the previous stage in a reasonable gradation, which shortens the particle spacing, reasonably increases the particle coordination number, and improves the contribution of particle packing to the mechanical properties of the paste. With the introduction of nanofillers, the 28-day compressive strength of the obtained composite silicate cement decreases by less than 15%.

[0030] 3) This invention fully utilizes the charge regulation and steric hindrance effects of the admixtures, avoids the agglomeration of nanofillers during the mixing process, promotes their filling and nucleation effects, and achieves a 3-day and 28-day strength of composite cement with a large amount of low-activity solid waste to reach more than 85% of that of ordinary Portland cement. Detailed Implementation

[0031] The present invention will be further explained and described below with reference to specific embodiments.

[0032] Example 1:

[0033] A composite silicate cement, the preparation method of which is as follows:

[0034] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture onto 1 part by weight of nano-silica (particle size 15nm~50nm, SiO2 content ≥99.5%), and then transfer the mixture into a vertical mixer, adding 40 parts by weight of waste brick powder (specific surface area ≥400m²). 2After mixing the cement (7-day activity index ≤ 65%, 28-day activity index ≤ 75%) with 59 parts by weight of P·Ⅰ42.5 silicate cement, the mixture is dried into a block mixture and then transferred to a ball mill. After adding the mixture, the mixture is ball-milled for 10 minutes to obtain composite silicate cement.

[0035] Example 2:

[0036] A composite silicate cement, the preparation method of which is as follows:

[0037] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture onto 1.5 parts by weight of nano-silica (particle size 15nm~50nm, SiO2 content ≥99.5%), and then transfer the mixture into a vertical mixer, adding 40 parts by weight of waste brick powder (specific surface area ≥400m²). 2 After mixing the cement (7d activity index ≤ 65%, 28d activity index ≤ 75%) evenly, the mixture is then transferred to a dryer to dry into a block mixture. The mixture is then transferred to a ball mill, and 58.5 parts by weight of P·Ⅰ42.5 silicate cement are added. The mixture is then ball-milled for 10 minutes to obtain composite silicate cement.

[0038] Example 3:

[0039] A composite silicate cement, the preparation method of which is as follows:

[0040] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture onto 1.5 parts by weight of nano-silica (particle size 15nm~50nm, SiO2 content ≥99.5%), and then transfer the mixture into a vertical mixer, adding 60 parts by weight of waste brick powder (specific surface area ≥400m²). 2 After mixing the cement (7d activity index ≤ 65%, 28d activity index ≤ 75%) evenly, it is then transferred to a dryer to dry into a block mixture. Then it is transferred to a ball mill, and 38.5 parts by weight of P·Ⅰ42.5 silicate cement are added. After ball milling for 10 minutes, composite silicate cement is obtained.

[0041] Example 4:

[0042] A composite silicate cement, the preparation method of which is as follows:

[0043] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture onto 1 part by weight of nano-metakaolin (particle size 50nm~100nm), and then transfer it to a vertical mixer, adding 40 parts by weight of waste brick powder (specific surface area ≥400m²). 2After mixing the cement (7-day activity index ≤ 65%, 28-day activity index ≤ 75%) with 59 parts by weight of P·Ⅰ42.5 silicate cement, the mixture is dried into a block mixture and then transferred to a ball mill. After adding the mixture, the mixture is ball-milled for 10 minutes to obtain composite silicate cement.

[0044] Example 5:

[0045] A composite silicate cement, the preparation method of which is as follows:

[0046] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture onto 1 part by weight of nano-metakaolin (particle size 50nm~100nm), and then transfer it to a vertical mixer. Add 40 parts by weight of low-calcium fly ash (CaO content ≤4%, spherical particle ratio >80%, specific surface area ≥400m²). 2 After mixing the cement (7-day activity index ≤70%, 28-day activity index ≤80%) with 59 parts by weight of P·Ⅰ42.5 silicate cement, the mixture is dried into a block mixture and then transferred to a ball mill. After adding the mixture, the mixture is ball-milled for 10 minutes to obtain composite silicate cement.

[0047] Comparative Example 1:

[0048] A composite silicate cement, the preparation method of which is as follows:

[0049] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate, and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, and then spray the solution onto 40 parts by weight of waste brick powder (specific surface area ≥ 400 m²). 2 The mixture is then dried in a dryer into a block mixture (7d activity index ≤65%, 28d activity index ≤75%), and then transferred to a ball mill. After adding 60 parts by weight of P·Ⅰ42.5 silicate cement, the mixture is ball-milled for 10 minutes to obtain composite silicate cement.

[0050] Comparative Example 2:

[0051] A composite silicate cement, the preparation method of which is as follows:

[0052] Disperse 0.03 parts by weight of triethanolamine, 0.3 parts by weight of sodium sulfate and 0.1 parts by weight of potassium aluminum sulfate in 10 parts by weight of water, then spray the mixture into 100 parts by weight of P·Ⅰ42.5 silicate cement, dry it in a dryer, and then ball mill it for 10 minutes to obtain composite silicate cement.

[0053] Performance testing:

[0054] The performance test data of the composite silicate cements of Examples 1-5 and Comparative Examples 1-2 are shown in the table below:

[0055] Table 1. Performance test data of composite silicate cement in Examples 1-5 and Comparative Examples 1-2

[0056]

[0057]

[0058] Note:

[0059] Standard consistency water requirement, initial setting time, and final setting time: Tested in accordance with "GB / T 1346-2011 Standard Consistency Water Requirement, Setting Time and Soundness Test Methods for Cement".

[0060] Compressive strength: Tested according to "GB / T 17671-1999 Cement Mortar Strength Test Method".

[0061] As shown in Table 1:

[0062] 1) Compared with Comparative Example 2, the addition of 40% waste brick powder reduced the 3-day and 28-day compressive strength of P·Ⅰ42.5 silicate cement to 24.2 MPa and 45.1 MPa, respectively, with a reduction of 28.0% and 16.8%, indicating that the direct addition of waste brick powder will significantly deteriorate the mechanical properties of silicate cement.

[0063] 2) Compared with Comparative Example 1, the addition of 1% and 1.5% nano-silica in Examples 1 and 2 increased the 3-day compressive strength of the composite cement from 24.2 MPa to 31.9 MPa and 35.7 MPa, respectively, with increases of 31.8% and 47.5%. This indicates that the introduction of nano-silica effectively promoted the pozzolanic reaction of early waste brick powder and the hydration reaction of cement after its filling and nucleation effects, shortened the setting time of composite cement, and improved the mechanical properties of composite cement, but increased the standard consistency water consumption.

[0064] 3) Compared with Example 2, Example 3 kept the nano silica content unchanged at 1.5%, while the waste brick powder content increased from 40% to 60%. Although the 3-day and 28-day compressive strengths of the prepared composite cement decreased, they could still reach 28.9 MPa and 46.7 MPa, respectively, meeting the strength requirements of 42.5 strength grade composite cement. This shows that under the condition that the nano silica content remains unchanged and the index meets the national standard for 42.5 strength grade composite cement, the waste brick powder content can be further increased.

[0065] 4) As can be seen from Examples 1, 4 and 5, both nano-silica and nano-kaolin can effectively improve the early strength of composite cement. Moreover, the promoting effect of nano-kaolin on the early and late strength of composite cement is better than that of nano-silica. It can be seen that with the support of nanomaterials, low-calcium fly ash, waste brick powder and other low-activity solid wastes can also be added to composite cement in large quantities without deteriorating the mechanical properties of composite cement.

[0066] In summary, this invention effectively improves the early and late strength of composite cement by rationally introducing nanofillers, or significantly increases the amount of low-activity solid waste while meeting the mechanical performance standards, thus having good social and environmental benefits.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing composite silicate cement, characterized in that, The process includes the following steps: dispersing the admixture in water, spraying it onto the nanofiller, adding low-activity solid waste powder and mixing evenly, drying, and then adding it together with silicate cement into a ball mill for ball milling to obtain composite silicate cement; the mass ratio of the admixture, water, nanofiller, low-activity solid waste powder, and silicate cement is 0.01-1:10:1-3:40-60:37-59; the admixture is a complex of an alkanolamine compound and an alkali metal salt; the alkanolamine compound is at least one of triethanolamine, triisopropanolamine, diethanolamine, and N-methyldiethanolamine; the alkali metal salt is at least one of sodium sulfate, potassium aluminum sulfate, sodium carbonate, and sodium acetate; the nanofiller is at least one of nano silica, nano calcium carbonate, and nano metakaolin; the low-activity solid waste powder is at least one of low-calcium fly ash, nickel-iron slag, limestone powder, and waste brick powder.

2. The preparation method according to claim 1, characterized in that: The nano-silica has a particle size of 15nm to 50nm; the nano-calcium carbonate has a particle size of 10nm to 100nm; and the nano-kaolin has a particle size of 50nm to 100nm.

3. The preparation method according to claim 1, characterized in that: The low-calcium fly ash has a CaO content of ≤4%, a spherical particle ratio of >80%, and a specific surface area of ​​≥400 m². 2 / kg, 7-day activity index ≤70%, 28-day activity index ≤80%; the nickel-iron slag is at least one of electric furnace nickel-iron slag and blast furnace nickel-iron slag, with a specific surface area ≥400m². 2 / kg, 7-day activity index ≤70%, 28-day activity index ≤80%; the specific surface area of ​​the limestone powder is ≥400m². 2 / kg, 7-day activity index ≤70%, 28-day activity index ≤80%; the specific surface area of ​​the waste brick powder is ≥400m². 2 / kg, 7d activity index ≤65%, 28d activity index ≤75%.

4. The preparation method according to claim 1, characterized in that: The ball milling time is 5 min to 30 min.

5. A composite silicate cement, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. A cement-based material, characterized in that, It includes the composite silicate cement as described in claim 5.

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