Method for enhancing the performance of cement mortar by acidizing electric field pre-carbonization

Abstract

The application discloses a method for enhancing the performance of cement mortar by acidizing electric field pre-carbonization, which comprises the following steps: the cement mortar comprises standard sand, cement, mixing water and an acid reagent; 10% of the total amount of cement is mixed with 80% of the total amount of mixing water and the acid reagent to obtain acidized cement paste; direct current is applied to the acidized cement paste for 5-25 min, CO2 is introduced into the acidized cement paste and continuously stirred to complete pre-carbonization, and acidized pre-carbonized cement paste is obtained; and the standard sand, the remaining cement in the total amount of cement, the remaining mixing water in the total amount of mixing water and the acidized pre-carbonized cement paste are mixed and stirred for 3-5 min. After the acid reagent is added to the cement paste for acidizing treatment, CO2 is introduced into the cement mortar and direct current is applied to the cement mortar, so that the greenhouse gas CO2 can be absorbed in a large amount, the mechanical performance of the concrete is greatly improved, the source of CO2 is very extensive and the cost is low, and the production cost of the concrete can be saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a method for enhancing the performance of cement mortar by acidification electric field pre-carbonization. BACKGROUND

[0002] The cement production industry emits about 135 million tons of CO2 per year, accounting for 7% of greenhouse gases released into the environment, which brings a heavy burden to environmental protection.

[0003] Although the cement mortar product can reabsorb part of the carbon dioxide emitted in the production process through chemical reaction in the natural environment, this natural process is very slow and may take hundreds of years, and the carbonization process of absorbing carbon dioxide can cause corrosion of the steel bars in the cement mortar, reducing the mechanical properties of the cement mortar.

[0004] Therefore, a method is needed that can both absorb carbon dioxide and avoid reducing the performance of the cement mortar. SUMMARY

[0005] The present application provides a method for enhancing the performance of cement mortar by acidification electric field pre-carbonization to solve the above problems.

[0006] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A method for enhancing the performance of cement mortar by acidification electric field pre-carbonization, comprising the following steps:

[0008] S1: the cement mortar comprises total amount of standard sand, total amount of cement, total amount of mixing water and acid reagent;

[0009] 10% of the total amount of cement is mixed with 80% of the total amount of mixing water and the acid reagent to obtain an acidified cement paste, a direct current is applied to the acidified cement paste for 5-25 min, CO2 is introduced into the acidified cement paste and continuously stirred to complete pre-carbonization, and an acidified pre-carbonized cement paste is obtained;

[0010] S2: 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 acidified pre-carbonized cement paste are mixed and stirred for 3-5 min.

[0011] Further, the acid reagent is acetic acid, and the concentration thereof is 99.5%.

[0012] Further, in the cement mortar, the total amount of cement is 525 parts, the total amount of standard sand is 1312.5 parts, the total amount of mixing water is 257.5 parts, and the acid reagent is 5 parts by weight.

[0013] Further, the voltage of the direct current is 30V.

[0014] Further, the purity of the CO2 is 95%-99%, and the speed of the CO2 is 500 mL / min.

[0015] Further, in S1, the stirring mode is using a magnetic stirrer, and the rotating speed of the magnetic stirrer is 900 r / min.

[0016] Further, in S2, the stirring mode is using a cement mortar automatic stirrer, and the rotating speed of the cement mortar automatic stirrer is 1000-2000 rpm.

[0017] Further, the cement is ordinary portland cement, and the strength grade is 42.5, 42.5R, 52.5 or 52.5R.

[0018] The beneficial effects of the present application are:

[0019] The method for enhancing the performance of cement mortar by acidizing electric field pre-carbonization disclosed in the present application can not only absorb a large amount of greenhouse gas CO2, but also greatly improve the mechanical properties of the cement mortar, and the mechanical properties of the concrete prepared by using the cement mortar prepared by the method are also significantly improved. Moreover, the source of CO2 is very extensive and low in cost, so the mechanical properties of the cement mortar and the concrete are improved, and the cost is saved. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 The structural schematic diagram of the device used for the method for enhancing the performance of cement mortar by acidizing electric field pre-carbonization disclosed in the embodiments of the present application;

[0022] Figure 2 The flow chart of the method for enhancing the performance of cement mortar by acidizing electric field pre-carbonization disclosed in the embodiments of the present application;

[0023] Figure 3 The 7-day compressive strength results of the mortar test pieces prepared by the methods of the embodiments 1-5 and the comparative examples 1-7 of the present application;

[0024] Figure 428-day compressive strength results for mortar specimens prepared according to the methods of Examples 1-5 and Comparative Examples 1-7 of the present invention;

[0025] Figure 5 7-day flexural strength results for mortar specimens prepared according to the methods of Examples 1-5 and Comparative Examples 1-7 of the present invention;

[0026] Figure 6 28-day flexural strength results for mortar specimens prepared according to the methods of Examples 1-5 and Comparative Examples 1-7 of the present invention.

[0027] In the figure: 1, direct current power supply; 2, power supply negative steel; 3, power supply positive carbon rod; 4, magnetic stirrer; 5, air regulator; 6, carbon dioxide cylinder; 7, beaker. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] The present application relates to principles:

[0030] In the preparation of acidified cement solution (paste), acetic acid first reacts with calcium hydroxide in cement through acid-base neutralization reaction. The strong alkaline reaction environment is not conducive to the rapid dissolution of active substances, but the addition of acetic acid (HAc) can reduce the strong alkaline environment around the cement particles, thereby promoting the dissolution of active substances (such as tricalcium silicate and dicalcium silicate); at the same time, the carboxyl group (-COOH) in acetic acid can form a chelate with Ca 2+ , further accelerating the dissolution of active substances in cement. Although the introduction of acetic acid can temporarily reduce the pH value of the solution, the continuous dissolution of active substances can increase the pH value of the hydration reaction, gradually rebuilding the strong alkaline conditions conducive to the formation of calcium silicate hydrate (C-S-H gel), thereby eliminating the adverse effects brought by the addition of acetic acid. Therefore, the addition of an appropriate amount of acetic acid can accelerate the dissolution of active substances without affecting the strong alkaline environment required for the formation of C-S-H gel. As a weak acid, acetic acid can slowly release H + , which enables it to continuously promote the progress of the hydration reaction without significantly reducing the alkalinity of the reaction environment, which also enables the C-S-H gel content to increase, significantly improving the mechanical properties of cement mortar.

[0031] When the acidified cement paste is subjected to an electric field and CO2, acetic acid (HAc) first reacts with calcium hydroxide in the cement to form calcium acetate and water. Because the solubility of calcium acetate is significantly higher than that of calcium hydroxide, this process promotes the release of more Ca 2+ to the solution. After the application of an electric field, the solution temperature shows a linear upward trend (about 3°C / 5 min), and this thermal effect increases the solubility of calcium hydroxide, which in turn increases the Ca 2+ concentration in the solution. According to the Le Chatelier principle, the presence of acetic acid promotes the CO2dissolution equilibrium to move in the direction of generating carbonate ions, thereby significantly increasing the CO3 2- concentration in the solution; near the cathode, the continuous production of OH - by water electrolysis also effectively promotes the dissolution of CO2. At this time, there are a large number of free CO3 2- and Ca 2+ in the solution, which react with each other to form nanometer or submicron-sized calcium carbonate particles. Under the driving of the electric field, the directional migration of charged particles significantly increases the generation rate of calcium carbonate, and part of the calcium carbonate crystal form will gradually change to a prismatic shape. The prismatic calcium carbonate crystals generated have higher mechanical properties due to their more stable structure, and can enhance the overall strength of the cement mortar. The carboxyl functional groups in the system preferentially anchor calcium ions through coordination, not only shortening the nucleation induction period of calcium carbonate, but also achieving crystal form selection through interface energy regulation—while inhibiting the growth of conventional calcite, it promotes the formation of metastable amorphous calcium carbonate (ACC) and vaterite and other mesocrystalline products. These high specific surface area non-equilibrium crystals not only act as nanofillers to improve density in the pores of the cement, but also act as heterogeneous nucleation sites to accelerate the hydration and crystallization process of silicate minerals, ultimately forming a multi-scale synergistically reinforced composite material system.

[0032] The addition of CO2 in OPC-based concrete or mortar by acidification-electricity pre-carbonation method changes the hydration degree of C3A. The final reaction products are mainly determined by the molar ratio of CO2 / Al2O3 and C3A / SO3. For example, if the molar ratio of C3A / SO3 of the cement is close to 1, the hydration of C3A modified by CO2 is:

[0033]

[0034] Continuous CO2 introduction leads to the partial or complete replacement of hemicarbonates by monocarbonates. According to the above equation, introducing CO2 into cement mortar alters the mineral properties of hydrated cement, promoting the formation and stabilization of more ettringite and increasing the formation of monocarbonates. These changes contribute to improving the strength and durability of cement mortar. The formation of ettringite results in the formation of more solid products, whose volume expansion characteristics can reduce the porosity of cement mortar, thereby enhancing its strength. Furthermore, the bulk modulus of monocarbonates is significantly higher than that of other hydration products; therefore, increasing the formation of monocarbonates may also improve the strength and hardness of cement mortar.

[0035] Simultaneously, the acidification-electrode pre-carbonization process generates a large amount of nano- and submicron-sized CaCO3. Before the nano- and submicron-sized calcium carbonate reaches a certain content, the porosity decreases with prolonged reaction time, thereby optimizing the pore structure. Furthermore, this process improves the morphology of CH crystals, refining them from hexagonal plates to prismatic shapes. The formation of nano-calcium carbonate also increases the CO3 content in the solution. 2- The content of CO3 2- It may replace SO4 in ettringite 2- This can prevent the transformation of ettringite, thereby stabilizing its structure and increasing the density of cement mortar.

[0036] Furthermore, acidification-electro-assisted precarbonation also compensates for the shortcomings of electro-assisted precarbonation and precarbonation methods to some extent. In electro-assisted precarbonation and precarbonation methods, excessively high reaction rates can cause some CSH gel to decalcify and generate CaCO3. Since CaCO3 has higher hardness and solid volume than CSH, the carbonization products of CaCO3 increase the strength of cement mortar in the early stages of the carbonization reaction. However, in the later stages of the precarbonization reaction, due to the consumption of CSH, the increase in later-stage strength compared to the early-stage strength is relatively small. Acidification-electro-assisted precarbonation, on the other hand, increases the CSH gel content due to the addition of acetic acid, which not only significantly improves early-stage strength but also substantially enhances later-stage strength.

[0037] Example

[0038] Example 1:

[0039] A method for enhancing the performance of cement mortar through pre-carbonation using an acidic electric field involves step S1 (electro-assisted pre-carbonation), which employs methods such as... Figure 1The device shown is carried out, the device includes a direct current power supply 1, power negative reinforcement 2, power positive carbon rod 3, magnetic stirrer 4, air conditioner 5, carbon dioxide cylinder 6 and beaker 7, direct current power supply positive and power positive carbon rod 3 electrically connected, direct current power supply 1 negative and power negative reinforcement 2 electrically connected, power positive carbon rod 3 and power negative reinforcement 2 end immerse in the cement paste in the beaker, the bottom of the beaker is provided with a magnetic stirrer, CO2 in carbon dioxide cylinder 6 is inflated into the acidified cement paste in the beaker through the air conditioner 5 and pipeline, and the pre-carbonization is carried out by power-on;

[0040] A method for enhancing the performance of cement mortar by acidification electric field pre-carbonization, comprising the steps of:

[0041] S1: take 10% of the total amount of cement (52.5 parts by weight), 80% of the total amount of mixing water (206 parts by weight), 5 parts by weight of acetic acid (concentration of 99.5%) into a beaker, mix to get acidified cement paste, apply 30V direct current to the acidified cement paste for 5min, at the same time use air conditioner to bubble CO2 directly into the acidified cement paste at a gas flow rate of 500mL / min, the time is 5min, the purity of CO2 is 95%, in this process, continuously stirring by magnetic stirrer, the speed of magnetic stirrer is 900r / min, pre-carbonization is completed, acidified pre-carbonized cement paste is obtained; in the cement mortar, 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 257.5 parts by weight; the cement is 42.5 ordinary portland cement;

[0042] 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 acidified pre-carbonized cement paste into the cement mortar automatic mixer, the speed of the cement mortar automatic mixer is 2000rpm, and the stirring time is 3min.

[0043] The flow chart of the method is shown in Figure 2 .

[0044] Example 2:

[0045] The difference between this embodiment and example 1 is only that in this embodiment, the acidified cement paste is subjected to 10min direct current, and 10min CO2 is introduced at the same time.

[0046] Example 3:

[0047] The difference between this embodiment and example 1 is only that in this embodiment, the acidified cement paste is subjected to 15min direct current, and 15min CO2 is introduced at the same time.

[0048] Example 4:

[0049] The difference between this example and Example 1 is that in this example, the acidified cement paste is subjected to direct current for 20 min while CO2is bubbled in for 20 min.

[0050] Example 5:

[0051] The difference between this example and Example 1 is that in this example, the acidified cement paste is subjected to direct current for 25 min while CO2is bubbled in for 25 min.

[0052] Comparative Example

[0053] Comparative Example 1:

[0054] The difference between this comparative example and Example 1 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0055] Comparative Example 2:

[0056] The difference between this comparative example and Example 2 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0057] Comparative Example 3:

[0058] The difference between this comparative example and Example 3 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0059] Comparative Example 4:

[0060] The difference between this comparative example and Example 4 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0061] Comparative Example 5:

[0062] The difference between this comparative example and Example 5 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0063] Comparative Example 6:

[0064] The difference between this comparative example and Example 1 is that in this comparative example, in S1, no acetic acid is added and the total amount of mixing water is 262.5 parts.

[0065] Comparative Example 7:

[0066] The difference between this comparative example and Example 1 is that in this comparative example, in S1, no CO2is bubbled into the cement paste, no direct current is applied, and no acetic acid is added, and the total amount of mixing water is 262.5 parts.

[0067] The cement mortar ingredient mixing ratio of Example 1-5 and Comparative Example 1-7 and the power-on and CO2 time are shown in Table 1 below:

[0068] Table 1 Cement mortar mixing ratio, acid amount, and power-on and CO2 time table of Example 1-5 and Comparative Example 1-7

[0069]

[0070] The compressive strength and flexural strength of the cement mortar after being stirred by the cement mortar automatic stirrer of Example 1-5 and Comparative Example 1-7 were tested:

[0071] (1) Compressive strength test method:

[0072] The cement mortar after being stirred by the cement mortar automatic stirrer was twice vibrated and placed into a three-cube mold with a side length of 70.7 mm, and six test blocks were prepared for each example and each comparative example. The average compressive strength and average flexural strength of the cement mortar were tested after 7 days and 28 days of water bath curing, and the test was performed in accordance with the JGJ / T+70-2009+ Building Mortar Basic Performance Test Method standard.

[0073] (2) The results are shown in Table 2 and Figures 3-6

[0074] Table 2 7-day compressive strength results of Example 1-5 and Comparative Example 1-7

[0075]

[0076] According to Table 2 and Figure 3Compared with the untreated control group (Comparative Example 7), the compressive strength of the mortar test piece prepared after acidizing and electrically pre-carbonizing for 5, 10, 15, and 20 minutes was increased by 31.36%, 38.26%, 51.73%, and 59.35%, respectively, and although the strength of the mortar test piece prepared after acidizing and electrically pre-carbonizing for 25 minutes decreased slightly, the strength was still increased by 49.73%, indicating that the acidizing and electrically pre-carbonizing method can significantly improve the compressive strength of the cement mortar. Compared with the mortar test piece prepared by adding acetic acid without electrically pre-carbonizing (Comparative Example 6), the compressive strength of the mortar test piece prepared by acidizing and electrically pre-carbonizing for 5, 10, 15, 20, and 25 minutes was increased by 8.51%, 14.20%, 25.33%, 31.63%, and 23.68%, respectively, further verifying the strengthening and promoting effect of the electrochemical effect on the acidizing effect. In addition, under the same electrically pre-carbonizing and CO2 treatment conditions, the compressive strength of the mortar test piece prepared by acidizing and electrically pre-carbonizing for 5, 10, 15, 20, and 25 minutes (Examples 1-5) was increased by 19.30%, 15.39%, 27.32%, 23.92%, and 30.98% compared with the mortar test piece prepared by electrically pre-carbonizing (Comparative Examples 1-5), indicating that the acidizing and electrically pre-carbonizing method can further improve the compressive strength of the cement mortar based on the electrically pre-carbonizing method.

[0077] Figure 4 The 28-day compressive strength results of the mortar test pieces prepared in Examples 1-5 and Comparative Examples 1-7 are shown in the graph, and it can be seen from the graph that the compressive strength of the mortar test piece prepared by the method is still higher than that of the concrete test piece prepared by the non-acidizing electrically pre-carbonizing method after 28 days of curing;

[0078] The 7-day flexural strength results of the mortar test pieces prepared in Examples 1-5 and Comparative Examples 1-7 are shown in the graph, and it can be seen from the graph that the 7-day flexural strength of the mortar test piece prepared by the acidizing and electrically pre-carbonizing method is significantly higher than that of the mortar test piece prepared by the electrically pre-carbonizing method, proving that the combination of acidizing and electrically pre-carbonizing can improve the flexural strength of the mortar test piece; Figure 5 The 28-day flexural strength results of the mortar test pieces prepared in Examples 1-5 and Comparative Examples 1-7 are shown in the graph, and it can be seen from the graph that the 28-day flexural strength of the mortar test piece prepared by the acidizing and electrically pre-carbonizing method is still higher than that of the mortar test piece prepared by the electrically pre-carbonizing method.

[0079] Figure 6 The 28-day flexural strength results of the mortar test pieces prepared in Examples 1-5 and Comparative Examples 1-7 are shown in the graph, and it can be seen from the graph that the 28-day flexural strength of the mortar test piece prepared by the acidizing and electrically pre-carbonizing method is still higher than that of the mortar test piece prepared by the electrically pre-carbonizing method.

[0080] ​It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for enhancing the performance of cement mortar through pre-carbonation using an acidic electric field, characterized in that, Includes the following steps: S1: Cement mortar includes total amount of standard sand, total amount of cement, total amount of mixing water, and acid reagent; Take 10% of the total cement and 80% of the total mixing water and acid reagent and mix them to obtain acidified cement slurry. Apply direct current to the acidified cement slurry for 5-25 minutes, and at the same time, introduce CO2 into the acidified cement slurry and stir continuously to complete the pre-carbonation and obtain acidified pre-carbonized cement slurry. S2: Mix 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 acidified precarbonated cement slurry, and stir for 3-5 minutes. The acid reagent is acetic acid.

2. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, The concentration of the acetic acid is 99.5%.

3. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, The cement mortar contains, by weight, 525 parts cement, 1312.5 parts standard sand, 257.5 parts mixing water, and 5 parts acid reagent.

4. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, The voltage of the DC power supply is 30V.

5. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, The purity of the introduced CO2 is 95%-99%, and the rate of CO2 introduction is 500 mL / min.

6. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, In S1, the stirring method is to use a magnetic stirrer with a rotation speed of 900 r / min.

7. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field according to claim 1, characterized in that, In S2, the mixing method is to use an automatic cement mortar mixer, and the speed of the automatic cement mortar mixer is 1000-2000 rpm.

8. The method for enhancing the performance of cement mortar through pre-carbonization using an acidified electric field 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.

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