A method for enhancing the compressive strength of cement mortar through electrostatic precarbonation

Abstract

This invention discloses a method for enhancing the compressive strength of cement mortar through electrostatic pre-carbonation, comprising the following steps: mixing 10% to 15% of the total cement with 80% of the total mixing water to obtain a cement paste; applying direct current to the cement paste for 5-25 minutes, while simultaneously introducing CO2 into the cement paste and continuously stirring to complete pre-carbonation, thereby obtaining a pre-carbonized cement paste; adding the total amount of standard sand, the remaining cement in the total amount of cement, the remaining mixing water in the total amount of mixing water, and the pre-carbonized cement paste to an automatic cement mortar mixer and stirring for 3-5 minutes. This method, by introducing CO2 into the cement mortar while applying direct current, not only absorbs a large amount of the greenhouse gas CO2, but also significantly improves the mechanical properties of concrete. Moreover, CO2 is widely available and inexpensive, thus saving costs while greatly improving the mechanical properties of concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for enhancing the compressive strength of cement mortar through electrostatic precarbonation. Background Technology

[0002] Concrete, using silicate cement as a binder, is the most widely used building material. Globally, concrete is second only to water in usage, accounting for 70% of all building and building materials. Although silicate cement has advantages such as ease of use and the global availability of raw materials, its production process releases significant amounts of the greenhouse gas CO2; one ton of cement clinker emits 0.98 tons of CO2 equivalent, and the cement industry accounts for 5% of global CO2 emissions.

[0003] Carbon dioxide emitted during the manufacture of silicate cement can be naturally absorbed by concrete products through natural chemical reactions. However, the natural process is too slow and may take hundreds of years to reabsorb all emitted carbon dioxide. In addition, carbonation is harmful to concrete, causing corrosion of steel bars and reducing the mechanical properties of concrete. Summary of the Invention

[0004] This invention provides a method for enhancing the compressive strength of cement mortar through electrostatic precarbonation, in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for enhancing the compressive strength of cement mortar through electrostatic precarbonation includes the following steps:

[0007] S1: Cement mortar includes the total amount of standard sand, the total amount of cement, and the total amount of mixing water;

[0008] Take 10% to 15% of the total cement and mix it with 80% of the total mixing water to obtain cement paste. Apply direct current to the cement paste for 5-25 minutes, and at the same time, introduce CO2 into the cement paste and stir continuously to complete the pre-carbonation and obtain pre-carbonized cement paste.

[0009] S2: Add the total amount of standard sand, the remaining cement in the total amount of cement, the remaining mixing water in the total amount of mixing water, and the pre-carbonated cement paste to the cement mortar automatic mixer and mix for 3-5 minutes.

[0010] Furthermore, the voltage of the DC power supply is set to 30V.

[0011] Furthermore, in S1, CO2 is introduced by using an air conditioner to directly blow CO2 into the cement slurry at a gas flow rate of 2L / min for 5-25 minutes.

[0012] Further, in S1, the cement mortar contains, by weight, 525 parts of cement, 1312.5 parts of standard sand, and 262.5 parts of mixing water.

[0013] Furthermore, in S1, the stirring method is to use a magnetic stirrer with a rotation speed of 900 r / min.

[0014] Furthermore, the purity of the CO2 is 95%-99%.

[0015] Furthermore, the cement is ordinary Portland cement with a strength grade of 42.5, 42.5R, 52.5 or 52.5R.

[0016] Furthermore, the rotation speed of the automatic cement mortar mixer is 1000-2000 rpm.

[0017] The beneficial effects of this invention are:

[0018] The present invention discloses a method for enhancing the compressive strength of cement mortar by electrostatic precarbonation. By introducing CO2 into the cement mortar while applying direct current, it can not only absorb a large amount of greenhouse gas CO2, but also significantly improve the mechanical properties of concrete. Moreover, CO2 is widely available and inexpensive, which saves costs while greatly improving the mechanical properties of concrete. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the device used in a method for enhancing the compressive strength of cement mortar through electrostatic precarbonation, as disclosed in an embodiment of the present invention.

[0021] In the diagram: 1. DC power supply; 2. Power supply negative electrode steel rod; 3. Power supply positive electrode carbon rod; 4. Magnetic stirrer; 5. Air conditioner; 6. Carbon dioxide cylinder; 7. Beaker. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The principle involved in this method is as follows:

[0024] During the process of applying electricity to cement mortar and pre-carbonizing it using S1, carbon dioxide gas first dissolves in water to form carbonic acid, and then the carbonic acid dissociates into H2O. + and CO3 2- H + and CO3 2- Ca released from cement clinker 2+ When these particles meet, they form calcium carbonate precipitates ranging from nanometers to submicrometers. Adding more carbon dioxide to the cement mortar will dissolve some of the calcium carbonate, forming calcium bicarbonate, which dissolves in water (calcium bicarbonate has high solubility in water). Therefore, carbonated cement mortar will contain abundant calcium carbonate particles and Ca... 2+ HCO3 - and a small amount of CO3 2- The generated calcium carbonate precipitate fills the pores in the cement mortar, reducing porosity and thus improving the density and strength of the cement mortar, enhancing its compressive strength and durability. Furthermore, the electrolysis, acting as a catalyst, accelerates the reaction rate, potentially causing the water in the cement paste to electrolyze, generating more hydrogen and hydroxide ions, and further electrolyzing more calcium carbonate, a key raw material for calcium carbonate formation. 2+ This leads to the production of more subsequent products, thereby improving the mechanical properties of concrete.

[0025] When the pre-carbonated cement paste in S2 is mixed with other cement mortar, on the one hand, the Ca(OH)2 and HCO3 produced by cement hydration... - The in-situ generation of nano- to submicron CaCO3 particles during the reaction provides additional heterogeneous nucleation sites for cement hydration, thus significantly improving the hydration performance of cement. On the other hand, adding CO2 to the cement paste through pre-carbonation alters the hydration performance of C3A. The final reaction products are mainly determined by the molar ratios of CO2 / Al2O3 and C3A / SO3. For example, when the C3A / SO3 molar ratio of cement is close to 1, the hydration reaction formula for CO2-modified C3A is:

[0026]

[0027] If more CO2 is added, the hemicarbonate in the above reaction formula will be partially or completely replaced by monocarbonate. From the above reaction formula, it can be seen that adding CO2 to cement mortar will change the mineralogical characteristics of hydrated cement: 1) it produces and stabilizes more ettringite, 2) it produces more monocarbonate, and 3) it reduces or eliminates monosulfate. All three changes are beneficial to the strength and durability of cement mortar. The formation of ettringite produces more solid products, and because ettringite expands significantly, it reduces the porosity of hydrated concrete, thereby increasing the strength of the cement mortar.

[0028] Example

[0029] Example 1:

[0030] In a method for enhancing the compressive strength of cement mortar through electro-carbonation, step S1 (electro-carbonation) involves using... Figure 1 The apparatus shown includes a DC power supply 1, a negative electrode steel bar 2, a positive electrode carbon rod 3, a magnetic stirrer 4, an air conditioner 5, a carbon dioxide cylinder 6, and a beaker 7. The positive electrode of the DC power supply is electrically connected to the positive electrode carbon rod 3, and the negative electrode of the DC power supply 1 is electrically connected to the negative electrode steel bar 2. The ends of the positive electrode carbon rod 3 and the negative electrode steel bar 2 are submerged in the cement slurry in the beaker. A magnetic stirrer is provided at the bottom of the beaker. CO2 from the carbon dioxide cylinder 6 is blown into the cement slurry in the beaker through the air conditioner 5 and pipelines for pre-carbonization by electricity.

[0031] A method for enhancing the compressive strength of cement mortar through electrostatic precarbonation includes the following steps:

[0032] S1: Add 15% (78.75 parts by weight) of the total cement and 80% (210 parts by weight) of the total mixing water to a beaker and mix to obtain a cement slurry. Apply a 30V DC current to the cement slurry for 5 minutes, and simultaneously use an air conditioner to directly bubble CO2 into the cement slurry at a gas flow rate of 2L / min for 5 minutes. The purity of the CO2 is 95%. During this process, continuously stir with a magnetic stirrer at a speed of 900r / min. Pre-carbonation is completed, and a pre-carbonized cement slurry is obtained. In the cement mortar, by weight, the total amount of cement is 525 parts, the total amount of standard sand is 1312.5 parts, and the total amount of mixing water is 262.5 parts; the cement is 42.5 ordinary Portland cement.

[0033] S2: Add the total amount of standard sand, the remaining cement in the total amount of cement, the remaining mixing water in the total amount of mixing water, and the pre-carbonated cement slurry to the cement mortar automatic mixer. The speed of the cement mortar automatic mixer is 2000 rpm, and the mixing time is 3 minutes.

[0034] Example 2:

[0035] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the cement slurry is energized with DC for 10 minutes and CO2 is introduced into the cement slurry for 10 minutes.

[0036] Example 3:

[0037] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the cement slurry is energized with DC for 15 minutes and CO2 is introduced into the cement slurry for 15 minutes.

[0038] Example 4:

[0039] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the cement slurry is energized with DC for 20 minutes and CO2 is introduced into the cement slurry for 20 minutes.

[0040] Example 5:

[0041] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the cement slurry is energized with DC for 25 minutes and CO2 is introduced into the cement slurry for 25 minutes.

[0042] Comparative Example

[0043] Comparative Example 1

[0044] The only difference between this comparative example and Example 1 is that in this comparative example, CO2 is introduced into the cement slurry, and no direct current is applied.

[0045] Comparative Example 2

[0046] The only difference between this comparative example and Example 2 is that in this comparative example, CO2 is introduced into the cement slurry, and no direct current is applied.

[0047] Comparative Example 3

[0048] The only difference between this comparative example and Example 3 is that in this comparative example, CO2 is introduced into the cement slurry, and no direct current is applied.

[0049] Comparative Example 4

[0050] The only difference between this comparative example and Example 4 is that in this comparative example, CO2 is introduced into the cement slurry, and no direct current is applied.

[0051] Comparative Example 5

[0052] The only difference between this comparative example and Example 5 is that in this comparative example, CO2 is introduced into the cement slurry, and no direct current is applied.

[0053] Comparative Example 6

[0054] The only difference between this comparative example and Example 1 is that in this comparative example, CO2 is not introduced into the cement paste, nor is direct current applied.

[0055] The cement mortar mix proportions and the times for applying electricity and CO2 in Examples 1-5 and Comparative Examples 1-6 are shown in Table 1 below:

[0056] Table 1. Cement mortar mix proportions and schedules for electricity and CO2 supply in Examples 1-5 and Comparative Examples 1-6

[0057]

[0058] The compressive strength of the cement mortar from Examples 1-5 and Comparative Examples 1-6 after being mixed by an automatic cement mortar mixer was tested.

[0059] (1) Method:

[0060] The cement mortar, after being mixed by an automatic cement mortar mixer, was vibrated a second time and placed into a triple cubic mold with a side length of 70.7 mm. Six test blocks were prepared for each example and each comparative example. After water bath curing for seven days, the average compressive strength of the cement mortar was tested in accordance with the JGJ / T+70-2009 standard for basic performance test methods of building mortar.

[0061] (2) The results are shown in Table 2

[0062] Table 2 Compressive strength results of Examples 1-5 and Comparative Examples 1-6

[0063]

[0064] As shown in Table 2, the compressive strength of the cement mortar in Examples 1-5 is significantly higher than that of the cement mortar in Comparative Example 6 (without direct current or CO2). Moreover, compared to the cement mortar in Comparative Examples 1-5 that was only pre-carbonized and not energized, the compressive strength of the cement mortar in Examples 1-5 that was pre-carbonized and energized is improved. Under the conditions of Example 2, namely, energization for 10 minutes and CO2 energization, the compressive strength after seven days is the highest, which can increase the compressive strength of cement mortar by 8.59%.

[0065] In summary, by introducing CO2 into cement mortar while applying direct current, the compressive strength of cement mortar is significantly improved. The method disclosed in this invention can not only absorb a large amount of greenhouse gas CO2, saving costs and promoting sustainable development, but also enable cement mortar to withstand greater loads during use, thereby improving the safety and durability of buildings.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for enhancing the compressive strength of cement mortar through electrostatic precarbonation, characterized in that, Includes the following steps: S1: Cement mortar includes the total amount of standard sand, the total amount of cement, and the total amount of mixing water; Take 10% to 15% of the total cement and mix it with 80% of the total mixing water to obtain cement paste. Apply direct current to the cement paste and introduce CO2 simultaneously within 5-25 minutes, while stirring continuously to complete pre-carbonation and obtain pre-carbonized cement paste. S2: Add the total amount of standard sand, the remaining cement in the total amount of cement, the remaining mixing water in the total amount of mixing water, and the pre-carbonated cement paste to the cement mortar automatic mixer and mix for 3-5 minutes.

2. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, The DC voltage is set to 30V.

3. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, In S1, CO2 is introduced by using an air conditioner to directly blow CO2 into the cement slurry at a gas flow rate of 2L / min.

4. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, In S1, the cement mortar contains, by weight, 525 parts of cement, 1312.5 parts of standard sand, and 262.5 parts of mixing water.

5. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, In S1, the stirring method is to use a magnetic stirrer with a speed of 900 r / min.

6. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, The purity of the CO2 is 95%. 99%.

7. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of 42.5, 42.5R, 52.5 or 52.5R.

8. The method for enhancing the compressive strength of cement mortar using an electrostatic precarbonation method according to claim 1, characterized in that, The automatic cement mortar mixer operates at a speed of 1000-2000 rpm.

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