Cement material for improving self-healing performance in microbial mortar based on blue-green algae oxygenation technology and preparation method of cement material

Abstract

The invention discloses a cement material for improving self-healing performance in microbial mortar based on a blue-green algae oxygenation technology and a preparation method of the cement material, and belongs to the technical field of building materials. A bacillus pseudofirmus bacterial solution, a spirulina platensis solution and expanded perlite are used as self-healing agents for improving the cement material; the cement material added with the self-healing agent has excellent mechanical properties and high crack healing rate. Under artificial illumination and natural illumination, the self-healing capability of the crack of the microbial mortar test piece is improved to different degrees, and the method has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and in particular relates to a cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology and a preparation method thereof. Background Art

[0002] Concrete is the most commonly used building material. It has excellent compressive strength and durability and is widely used in the construction of various structures. In addition, its strong adaptability to various engineering environments has also been favored by civil engineers. However, concrete is prone to cracking under tensile loads, and when subjected to tensile stress, cracks will spread rapidly. The presence of these cracks will reduce the bearing capacity and sealing of the structure, thereby causing damage to the concrete structure, and ultimately leading to failure and disaster of the building structure.

[0003] At present, the traditional repair methods mainly include: surface sealing method, crack grouting method and steel reinforcement method. However, the traditional repair method requires manual monitoring of the development of cracks, the repair cost is high, and the chemical repair agent of concrete is usually toxic, which may pose a risk to the natural environment and people's health. Therefore, some scholars have proposed an active repair method, that is, adding materials with repair functions to concrete in advance. When cracks occur, the repair materials can sense and repair them, and the crack repair process does not require manual monitoring and intervention. Among them, the repair materials added to concrete include hollow glass fibers containing binders, microcapsules containing polymers, and shape memory alloy materials. However, most of the repair materials added to concrete are organic polymers, which have problems such as poor durability, high cost and incompatibility with the concrete matrix. Therefore, researchers began to use microbial induced calcium carbonate precipitation (MICP) technology to achieve the purpose of autonomously repairing concrete cracks.

[0004] Microbial self-healing concrete technology (MICP) mainly refers to the process in which bacteria consume nutrients through their own metabolism to produce mineralized products to heal cracks. However, as cement hydration continues, the concrete gradually becomes dense, and the living space and oxygen acquisition of bacteria will be greatly affected, thereby affecting the MICP effect. Zhou et al. (Y. Zhou, M. Elchalakani, L. Cheng, M. A Shahin, Impact of calcium content and pH value on MICP crack healing of geopolymer concrete, Cement and Concrete Composites 146 (2024) 105410.) confirmed through research that the alkaline environment of concrete will weaken the MICP effect. Therefore, adding some porous materials to concrete can achieve the purpose of protecting bacteria and improving survival rate. Zeolite, diatomaceous earth and biochar have been proven to effectively adsorb and protect bacterial spores and have a good healing effect.

[0005] In addition, the oxygen content is crucial to improving the MICP effect, because the MICP of microorganisms is based on respiration. Tan et al. (L. Tan, B. Reeksting, I. Justo-Reinoso, V. Ferrandiz-Mas, A. Heath, S. Gebhard, K. Paine, The effect of oxygen and water on the provision of crack closure in bacteria-based self-healing cementitious composites, Cement and Concrete Composites 142 (2023) 105201.) added calcium peroxide to the cement matrix and observed the healing of the cracks. It was proposed that calcium peroxide can provide additional oxygen during the healing process, resulting in an increase in the healing efficiency. Among them, cyanobacteria can achieve MICP through photosynthesis. It has the ability to metabolize inorganic carbon through the photosynthetic autotrophic mechanism of a multi-enzyme system. It can usually use carbon dioxide as a carbon source, fix it into the cyanobacteria, and produce oxygen. Another researcher Barra et al. (H. C.Ostojic, Torres-Aravena, M. Rivas, C. Vílchez, D. Jeison, Use of photosynthetic MICP to induce calcium carbonate precipitation: Prospecting the role of the microorganism in the formation of CaCO3 crystals, Algal Research 80 (2024) 103499.) proved that cyanobacteria can promote the realization of MICP through photosynthesis. The results show that when cyanobacteria are added to the cement matrix, due to the extracellular polymers of cyanobacteria, acidic groups with low acid dissociation constants (such as carboxyl-COOH), etc., which are negatively charged under alkaline conditions, they will attract calcium ions and eventually combine to form calcium carbonate to fill cracks. Therefore, adding cyanobacteria to biomass mortar can utilize the oxygen produced by photosynthesis of cyanobacteria to maintain the activity of microorganisms and promote microbial metabolism.

[0006] However, there are some problems in the above-mentioned public documents. For example, the addition of chemical substances such as calcium peroxide will lead to excessively high ion concentrations at local locations, which will produce certain toxicity to microorganisms and affect the MICP effect. In addition, if cyanobacteria are added to cement mortar alone, their limited carbon source will affect their MICP effect, and the addition of cyanobacteria will affect the fluidity of cement and be unfavorable for mixing. Therefore, it is urgent to provide a cement material and a preparation method thereof that can not only solve the lack of oxygen in the cement matrix but also have excellent self-healing properties. Summary of the invention

[0007] The present invention proposes a cement material and a preparation method thereof for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology. The purpose of MICP is achieved by using Spirulina platensis in the cement matrix, and the problem of insufficient oxygen in the cement matrix affecting the MICP effect of microorganisms is solved.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention:

[0010] A self-healing agent for improving cement materials, the raw materials include:

[0011] Bacillus pseudofirmus solution, Spirulina platensis solution and expanded perlite;

[0012] The mass ratio of the three is 50:50:34.

[0013] Beneficial effects: The expanded perlite in the present invention has a rich porous structure, which can provide sufficient attachment sites and oxygen for Bacillus pseudofirmus spores, and at the same time play a role in protecting the spores. The principle of Bacillus pseudofirmus promoting the healing of cement cracks is that it can produce spores in a harsh environment and enter a dormant state, and respond to the surrounding harsh conditions in an unactivated spore state. When the surrounding environmental conditions are suitable, the spores will be activated into bacteria, and carbon dioxide will be produced by metabolic consumption of calcium organic compounds (usually defined as nutrients) contained in the cement matrix. In an alkaline environment, part of CO2 reacts with water in the pore solution to form carbonate ions, which further combine with free calcium ions in the cement matrix to form CaCO3 to fill the cracks. Platen Spirulina is selected because it can survive under alkaline conditions, produce oxygen for activating microorganisms through photosynthesis, and can reproduce rapidly in the form of asexual binary fission. Therefore, in the self-healing agent for cement materials disclosed in the present invention, each raw material component interacts with each other and plays a role in improving the mechanical properties of cement materials and the crack healing rate.

[0014] Preferably, the concentration of the Bacillus pseudofirmus liquid is 3.5×10 9 ~4.0×10 9 / mL.

[0015] Preferably, the culture process of the Bacillus pseudofirmus bacterial liquid is:

[0016] The Bacillus pseudofirmus was transplanted into the culture medium and cultured in a shaking incubator at 25-30° C. and 120 r / min for 48 h.

[0017] Preferably, the culture medium comprises beef extract, peptone, sodium chloride and purified water;

[0018] Among them, the mass fraction of beef extract in pure water is 0.5%; the mass fraction of peptone in pure water is 0.3%; and the mass fraction of sodium chloride in pure water is 0.5%.

[0019] Preferably, the absorbance of the Spirulina platensis solution at 600 nm measured by a spectrophotometer is 0.6; wherein the Spirulina platensis is purchased from the National Aquatic Biological Germplasm Freshwater Algae Seed Bank.

[0020] Preferably, the expanded perlite has a particle size of 2-4 mm and a water absorption rate of 300%.

[0021] Preferably, the preparation process of the self-healing agent is:

[0022] The method is prepared by adding the Spirulina platensis solution and expanded perlite into a Bacillus pseudofirmus bacterial solution and soaking them for 24 hours.

[0023] The second technical solution of the present invention:

[0024] A cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology, comprising the following raw materials:

[0025] Water, calcium lactate, cement, standard sand and the self-healing agent.

[0026] Preferably, the cement material comprises the following raw materials in parts by weight:

[0027] 400-500 parts of water, 8-15 parts of calcium lactate, 900-1000 parts of cement, 50-150 parts of the self-healing agent and 1400-2000 parts of standard sand.

[0028] Preferably, the cement is ordinary Portland cement, and its main components are shown in Table 1.

[0029] Table 1

[0030]

[0031] The density of the standard sand is 2580kg / m 3 , the water absorption rate is 0.57%.

[0032] The third technical solution of the present invention:

[0033] The method for preparing the cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology comprises the following steps:

[0034] mixing the water and calcium lactate to form a calcium lactate solution;

[0035] The cement and standard sand are stirred once at a low speed to be evenly mixed, the calcium lactate solution is added and stirred twice at a low speed, and finally the self-healing agent is added and stirred at a high speed to obtain mortar;

[0036] The mortar is poured into a mold, cured, and demoulded to obtain the cement material.

[0037] Beneficial effects: The present invention mixes calcium lactate with water first, which is beneficial to the full dissolution of calcium lactate and promotes the uniform distribution of calcium lactate in the mortar.

[0038] Preferably, the time for the low-speed stirring is 30 seconds, and the stirring speed is 60 revolutions per minute.

[0039] Preferably, the secondary low-speed stirring time is 1.5 min and the rotation speed is 60 rpm.

[0040] Preferably, the high-speed stirring time is 2 min and the rotation speed is 255 rpm.

[0041] Preferably, the standard curing conditions are 20±2°C and humidity>99%.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] (1) The Spirulina platensis solution used in the present invention has a simple preparation process, low material price, can survive in the cement matrix for a certain period of time, and can be mass-produced and applied to practical projects; on the other hand, due to its unique structural polysaccharides and proteins, it helps to improve the microstructure of cement. In addition, its extracellular polymers have a certain water retention capacity, which helps the secondary hydration of incompletely hydrated particles in cement, thereby producing more hydration products. Combining the above two reasons, the density of the cement mortar after adding it as a raw material to the self-healing agent, and the flexural and compressive strength of the final test piece are improved.

[0044] (2) The present invention adopts Bacillus pseudofirmus bacterial solution, Spirulina platensis solution and expanded perlite to form a self-healing agent. It can be found that in the crack healing process, under artificial lighting, the photosynthesis of Spirulina platensis is significant, and it preferentially generates calcium carbonate crystals and releases oxygen. The calcium carbonate crystals produced by Spirulina platensis attract BP (Bacillus pseudofirmus) spores and also produce oxygen for its metabolism, which is beneficial to the metabolism of BP bacteria, and finally generates calcium carbonate crystals with smoother surfaces, and finally the cracks can be healed in 14 days. Under natural lighting, since the photosynthesis of cyanobacteria is weak due to light reduction, more calcium carbonate cannot be produced, but the carbon dioxide produced by bacterial respiration can be used to promote photosynthesis to produce oxygen, to promote the MICP effect of bacteria, to produce calcium carbonate, fill the cracks, and finally heal the cracks in 28 days.

[0045] (3) The present invention uses Bacillus pseudofirmus liquid, Spirulina platensis solution and expanded perlite to form a self-healing agent, which improves the mechanical properties of the mortar specimen and the crack healing rate. Under artificial light and natural light, both improve the self-healing ability of the cracks of the microbial mortar specimen to varying degrees, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0047] Figure 1 This is a process flow chart for preparing a cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology according to Example 1 of the present invention;

[0048] Figure 2 It is a bar chart of the compressive and flexural strengths of the mortar specimens prepared in Example 1 and Control Groups 1-3 after curing for 28 days;

[0049] Figure 3 This is a bar chart of ultrasonic testing of mortar specimens prepared in Example 1 and Control Groups 1-3 after curing for 28 days;

[0050] Figure 4 This is a SEM microscopic image of the filling material at the crack of the cement-based material prepared by the control group 2 using Spirulina platensis as a self-healing agent alone, taken at a healing age of 28 days;

[0051] Figure 5 This is a SEM microscopic image of the filler at the crack of the microbial self-repairing cement-based material prepared in Example 1, taken when the healing age is 28 days;

[0052] Among them, (a) is the SEM image of the filling at the crack under artificial light, and (b) is the SEM image of the filling at the crack under natural light. DETAILED DESCRIPTION

[0053] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0054] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0055] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0056] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0057] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0058] The present invention discloses a cement material for improving the self-healing performance in microbial mortar based on blue algae oxygenation technology. The cement material comprises 400 to 500 parts of water, 8 to 15 parts of calcium lactate, 900 to 1000 parts of cement, 50 to 150 parts of self-healing agent and 1400 to 2000 parts of standard sand in parts by mass.

[0059] Also disclosed is a cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology and a preparation method thereof, comprising the following steps:

[0060] 1. Preparation of self-healing agent:

[0061] There are three types of self-healing agents: Mix the solution of Spirulina platensis and expanded perlite and soak them for 24 hours to obtain self-healing agent A; Mix the solution of Bacillus pseudofirmus and expanded perlite and soak them for 24 hours to obtain self-healing agent B; Mix the solution of Bacillus pseudofirmus, the solution of Spirulina platensis and expanded perlite and soak them for 24 hours to obtain self-healing agent C;

[0062] 2. Mixing and curing of mortar:

[0063] ① Weigh water, calcium lactate, cement, self-healing agent and standard sand according to mass proportion;

[0064] ② Mix the weighed water and calcium lactate to obtain a mixed solution;

[0065] ③ Stir the weighed cement and standard sand once at a low speed to mix them evenly, then add the mixed solution and stir them at a low speed for a second time, and finally add the self-healing agent and stir them at a high speed to obtain mortar. Curing the mortar under standard curing conditions, thus obtaining a cement material based on cyanobacteria oxygenation technology to improve the self-healing properties of microbial mortar.

[0066] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0067] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0068] The raw materials used in the present invention are all purchased from the market.

[0069] The technical solution of the present invention is further illustrated by the following embodiments.

[0070] Example 1

[0071] like Figure 1 As shown, a method for preparing a cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology comprises the following steps:

[0072] (1) Raw material weighing:

[0073] The following raw materials are weighed and set aside according to their weight: 400 parts of water, 8 parts of calcium lactate, 1000 parts of cement, 134 parts of the self-healing agent and 1390 parts of standard sand;

[0074] (2) Preparation of self-healing agent C:

[0075] Beef extract, peptone, sodium chloride, distilled water, sodium bicarbonate and sodium carbonate were used to prepare a bacterial liquid culture medium, wherein the mass fraction of beef extract in pure water was 0.5%, the mass fraction of peptone in pure water was 0.3%, the mass fraction of sodium chloride in pure water was 0.5%, and the mass fraction of sodium bicarbonate and sodium carbonate in pure water was 0.05% and 0.0675% respectively. The strain was transplanted into the culture medium and cultured in a shaker at 25°C and 120 rpm for 48 hours to obtain a bacterial liquid concentration of 3.6×10 9 cells / mL of Bacillus pseudofirmus;

[0076] Mix 50g of Spirulina platensis solution, 34g of expanded perlite and 50g of bacterial solution, and soak for 24 hours to form a self-healing agent for later use.

[0077] (3) Preparation of cement materials:

[0078] First, mix water and calcium lactate into a solution;

[0079] Then, the weighed cement and standard sand were stirred once at a low speed (the speed was 60 rpm and the stirring time was 30 seconds) to mix evenly, and then the calcium lactate solution was added and stirred twice at a low speed (the speed was 60 rpm and the stirring time was 1 minute and 30 seconds), and finally the self-healing agent was added and stirred at a high speed (the speed was 255 rpm and stirred for 2 minutes) to obtain mortar;

[0080] Finally, the mortar is poured into a mold and cured under standard curing conditions (20±2°C, humidity>99%), and after demolding, a microbial self-repairing cement-based material containing cyanobacteria is obtained.

[0081] Example 2

[0082] The difference from Example 1 is that the weight proportions of raw materials are: 500 parts of water, 8 parts of calcium lactate, 1000 parts of cement, 1390 parts of standard sand, and 34 parts of expanded perlite; other preparation conditions are the same as Example 1.

[0083] Example 3

[0084] The difference from Example 1 is that the weight portions of raw materials are: 450 parts of water, 8 parts of calcium lactate, 1000 parts of cement, 84 parts of self-healing agent A (50 parts and 34 parts of Spirulina platensis solution and expanded perlite, respectively) and 1390 parts of standard sand; other preparation conditions are the same as in Example 1.

[0085] Example 4

[0086] The difference from Example 1 is that the weight proportions of raw materials are: 450 parts of water, 8 parts of calcium lactate, 1000 parts of cement, 84 parts of self-healing agent B (50 parts of Bacillus pseudofirmus liquid and 34 parts of expanded perlite, respectively) and 1390 parts of standard sand; other preparation conditions are the same as in Example 1.

[0087] Control group 1

[0088] The difference from Example 1 is that

[0089] Step (1) does not contain a self-healing agent component, and the components are only composed of water, calcium lactate, cement and standard sand. Other preparation steps and conditions are consistent with Example 1.

[0090] Control group 2

[0091] The difference from Example 1 is that

[0092] The microbial self-healing agent prepared in step (1) contains only the Spirulina platensis solution. The other preparation steps and conditions are the same as those in Example 1.

[0093] Control group 3

[0094] The difference from Example 1 is that

[0095] Step (1) prepares a microbial self-healing agent containing only a solution of Bacillus pseudofirmus. Other preparation steps and conditions are the same as those in Example 1.

[0096] Figure 2 The bar charts of the compressive and flexural strengths of the mortar specimens prepared in Example 1 and Control Groups 1-3 after curing for 28 days show that the mechanical properties of the specimens are improved after adding the self-healing agent, and the mechanical properties of the mortar specimens are significantly enhanced under the synergistic effect of Spirulina platensis and microorganisms. Therefore, the cement-based material based on the self-healing performance of microorganisms enhanced by cyanobacteria in Example 1 has good mechanical properties.

[0097] Figure 3 This is a bar chart of ultrasonic testing of the mortar specimens prepared in Example 1 and control groups 1-3 after curing for 28 days; this experiment can detect the density inside the test specimen, that is, the higher the value, the better the density.

[0098] Figure 4This is a microscopic picture of the cement material when the control group 2 used only platensis as a self-healing agent; under artificial light, the photosynthesis of platensis is relatively active, and the enzymes in the cyanobacteria catalyze the reaction of carbon dioxide in the air with water to form more bicarbonate ions. There is an ion dissolution equilibrium in the pore solution in the cement matrix, producing carbonate ions, which eventually combine with calcium ions in the pore solution to form calcium carbonate crystals, causing a certain degree of healing of the cracks.

[0099] Figure 5 The SEM microscopic image of the filler at the crack of the microbial self-repairing cement-based material prepared in Example 1 was taken at a healing age of 28 days; wherein, (a) is a SEM image of the filler at the crack under artificial light, and (b) is a SEM image of the filler at the crack under natural light. Under artificial light, the photosynthesis of cyanobacteria significantly increases the formation of calcium carbonate crystals and releases oxygen. The calcium carbonate crystals produced by cyanobacteria attract BP spores and also produce oxygen for their metabolism, which is beneficial to the metabolism of BP bacteria, and finally produces calcium carbonate crystals with smoother surfaces. Under natural light, the photosynthesis of cyanobacteria is limited due to insufficient carbon source and weak light intensity, but the CO2 produced by bacteria can promote the photosynthesis of cyanobacteria, produce oxygen and then promote bacterial metabolism, and this process can continue, so more hyphae were observed at 28 days of healing, and they were still respiring.

[0100] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A self-healing agent for improving cement materials, characterized in that: Ingredients include: Bacillus pseudofirmus solution, Spirulina platensis solution and expanded perlite; The mass ratio of the three is 50:50:

34.

2. A self-healing agent for improving cement materials according to claim 1, characterized in that: The concentration of the Bacillus pseudofirmus liquid is (3.5-4.0)×10 9 / mL.

3. A self-healing agent for improving cement materials according to claim 1, characterized in that: The culture process of the Bacillus pseudofirmus liquid is as follows: The Bacillus pseudofirmus was transplanted into the culture medium and cultured in a shaking incubator at 25-30° C. and 120 r / min for 48 h.

4. A self-healing agent for improving cement materials according to claim 1, characterized in that: The preparation process of the self-healing agent is: The self-healing agent is prepared by adding the Spirulina platensis solution and expanded perlite into a Bacillus pseudofirmus bacterial solution and soaking the solution for 24 hours.

5. A cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology, characterized in that: Including the following ingredients: Water, calcium lactate, cement, standard sand and the self-healing agent according to any one of claims 1 to 4.

6. The cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology according to claim 5 is characterized in that: The cement material includes the following raw materials in parts by weight: 400-500 parts of water, 8-15 parts of calcium lactate, 900-1000 parts of cement, 50-150 parts of self-healing agent and 1400-2000 parts of standard sand.

7. A method for preparing a cement material for improving the self-healing performance of microbial mortar based on cyanobacteria oxygenation technology according to claim 5 or 6, characterized in that: The following steps are involved: mixing the water and calcium lactate to form a calcium lactate solution; The cement and standard sand are stirred once at a low speed to be evenly mixed, the calcium lactate solution is added and stirred twice at a low speed, and finally the self-healing agent is added and stirred at a high speed to obtain mortar; The mortar is poured into a mold, cured and demoulded to obtain the cement material.

8. The preparation method according to claim 7, characterized in that: The time of the low-speed stirring is 30 seconds, and the stirring speed is 60 revolutions per minute.

9. The preparation method according to claim 7, characterized in that: The secondary low-speed stirring lasts for 1.5 min and the rotation speed is 60 rpm.

10. The preparation method according to claim 7, characterized in that: The high-speed stirring time is 2 minutes and the rotation speed is 255 revolutions per minute.

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