Biomass shrinkage reducing agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of concrete admixtures, and particularly discloses a biomass shrinkage reducing agent as well as a preparation method and application thereof. The biomass shrinkage reducing agent comprises mycelium pellets of fungi with the particle size of 0.5 mm to 4 mm. According to the invention, mycelium pellets of fungi are creatively provided as a shrinkage reducing agent, the mycelium pellets can adjust the internal moisture state of a cementing material and play a role in internal curing, and polysaccharide substances wrapping the surfaces of the mycelium pellets have a retarding effect on hydration reaction of Portland cement, so that the problem of shrinkage cracks on the surface of concrete can be reduced; the long-term stable reduction effect and volume stability are maintained; meanwhile, the surfaces of the mycelium pellets contain a large number of tough mycelia, the mycelia can play a role of fibers, and the compressive strength of the cementing material is improved; in addition, the mycelium pellets can be infinitely propagated in a proper environment, and compared with a chemical shrinkage reducing agent, the mycelium pellets are more economical, have less influence on the environment and have remarkable advantages in cost effectiveness and environmental friendliness.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, and in particular to a biomass shrinkage reducing agent and a preparation method and application thereof. Background Art

[0002] Concrete has become the world's largest building material due to its low cost, high compressive strength, and simple production process. However, cement concrete has low tensile strength and is very brittle. In addition, in actual service environments, concrete structures are prone to cracking and form many cracks under the stress caused by drying shrinkage and chemical shrinkage. In addition, the shrinkage cracking problem of alkali-activated concrete is even more serious. Its shrinkage value is 4 to 5 times that of cement-based materials, which can easily cause material cracking, resulting in strength shrinkage, reduced durability, and other problems, which greatly limits the application of alkali-activated gel materials. The presence of cracks can cause a variety of corrosive ions to invade the interior of the concrete, seriously weakening the durability of the structure. Therefore, how to effectively reduce the drying shrinkage rate of various types of concrete and improve the stability of its product structure is a problem that needs to be solved urgently.

[0003] For various concrete drying shrinkage problems, the mitigation measures currently adopted mainly include: adjusting aggregate size, using internal curing materials to maintain the internal humidity of the matrix, adding expansive cement to compensate for volume shrinkage, adding chemical shrinkage reducers to slow down water evaporation and weaken the shrinkage pressure of capillaries due to drying, etc. Each of the above methods has its own advantages and disadvantages and scope of application. For example, super absorbent resin (SAP) has excellent water absorption and release properties. As an internal curing material, it can effectively control the internal humidity of concrete and effectively improve the shrinkage cracking of concrete. However, after SAP releases water, it produces large pores that reduce the strength of concrete and increase the later drying shrinkage. At present, the literature reports an adduct of a polyetheramine and a compound containing an epoxy group as a drying-reducing agent. This method can weaken the effect of shrinkage reducers on the early strength of cement-based concrete, but this method is complicated to operate, costly, and cannot maintain a long-term stable shrinkage reduction effect. Another shrinkage reducer with water-reducing effect is generated by catalysis, oxidation, copolymerization and other chemical reactions of dipropylene glycol monomethyl ether. It makes cement-based concrete have good early strength, but its shrinkage reduction effect is small, the synthesis process is complicated, and large-scale use significantly increases construction costs. In general, the existing concrete shrinkage reducer synthesis steps are cumbersome, the cost is high, and it is impossible to maintain long-term stable shrinkage reduction effect and volume stability, which affects the mechanical properties of concrete. How to effectively solve the problem of concrete, especially the self-shrinkage problem of alkali-activated concrete materials, is a problem that needs to be solved urgently in the current concrete field. Summary of the invention

[0004] In view of the problems that the preparation steps of concrete shrinkage reducers in the prior art are cumbersome, costly, and unable to maintain long-term stable shrinkage reduction effect and volume stability, the present invention provides a biomass shrinkage reducer and its preparation method and application. The present invention utilizes the water absorption and release characteristics of mycelial balls to adjust the internal moisture state of cementitious materials and effectively control the drying shrinkage of concrete. The polysaccharide substances wrapped on the surface of mycelial balls have a retarding effect on the hydration reaction of silicate cement, which is beneficial to reduce the occurrence of shrinkage cracks on the concrete surface and maintain long-term stable shrinkage reduction effect and volume stability; at the same time, the surface of mycelial balls contains a large number of tough hyphae, which can play the role of fibers, thereby improving the strength of cementitious materials, providing a new type of shrinkage reducer with excellent performance in the field of concrete, and having broad application prospects.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, the present invention provides a biomass shrinkage reducing agent, comprising fungal mycelium pellets, wherein the moisture content of the mycelium pellets is ≥99%.

[0006] Compared with the prior art, the present invention creatively proposes to use fungal mycelium balls as shrinkage reducing agents. The polysaccharides coated on the surface of the mycelium balls have a retarding effect on the hydration reaction of silicate cement, which is beneficial to reducing the occurrence of shrinkage cracks on the concrete surface and maintaining long-term stable shrinkage reduction effect and volume stability. At the same time, the surface of the mycelium balls contains a large number of tough hyphae, which can act as fibers, thereby improving the strength of cementitious materials. In addition, the mycelium balls can reproduce indefinitely under suitable conditions, which is more economical than chemical shrinkage reducing agents. Moreover, the mycelium balls are a renewable resource with less impact on the environment. They are a sustainable green building material with significant advantages in cost-effectiveness and environmental friendliness.

[0007] It should be noted that the mycelium ball is a small ball formed by the mycelium of the fungus tightly entwined together.

[0008] Furthermore, the fungus is of the genus Aspergillus.

[0009] Furthermore, the fungus is at least one of Aspergillus niger, Aspergillus oryzae, Monascus, Aspergillus niger or Mucor.

[0010] Furthermore, the particle size of the mycelium ball is 0.5mm~4mm.

[0011] The hydroxyl groups of polysaccharides coated on the surface of mycelial balls are adsorbed on the surface of cement particles and the O 2-The formation of hydrogen bonds, while other hydroxyl groups are associated with water molecules through hydrogen bonds, so that a stable solvent film is formed on the surface of cement particles, thereby inhibiting the hydration process of cement. At the same time, it can also play a role in moisturizing, which is beneficial to slow down the hydration reaction and prevent the occurrence of shrinkage cracks on the concrete surface. At the same time, mycelium balls have good water absorption and release characteristics. The added mycelium balls are in a saturated state (water content ≥ 99%). In the early stage of the hydration reaction, the water absorbed by the mycelium balls is slowly released, which effectively slows down the hydration reaction. The mycelium balls can also play the role of fibers, which is beneficial to the improvement of the strength of cementitious materials.

[0012] In a second aspect, the present invention also provides a method for preparing a biomass shrinkage reducing agent, comprising the following steps: The fungal spores are inoculated into a sterilized liquid culture medium, cultured, sterilized, and mycelium balls are filtered out to obtain a biomass shrinkage reducing agent.

[0013] The shrinkage reducing agent provided by the present invention belongs to a biomass water reducing agent, is renewable and degradable, and has an environmentally friendly production process. Using mycelium pellets as a shrinkage reducing agent can reduce the use of chemical reagents, which meets the requirements of sustainable development.

[0014] Furthermore, the liquid culture medium includes: 1 g of dipotassium hydrogen phosphate, 0.1 g of magnesium sulfate, 0.5 g of potassium chloride, 0.06 g of ferrous sulfate, 30 g of sucrose, 3 g of sodium nitrate, and 1000 mL of distilled water.

[0015] Furthermore, the concentration of fungal spores in the culture medium after inoculation was 10 6 / mL~10 12 Pieces / mL.

[0016] Furthermore, the culture temperature is 25°C to 35°C, the rotation speed is 150r / min to 170r / min, and the culture time is 3d to 10d.

[0017] Exemplarily, the blank culture medium and the mycelial pellets after the culture are sterilized by high pressure sterilization at 121° C. for 20 min.

[0018] In a third aspect, the present invention further provides a concrete comprising any of the biomass shrinkage reducing agents described above.

[0019] Furthermore, the concrete also includes cementitious materials, sand, gravel and water.

[0020] Furthermore, the amount of the biomass shrinkage reducer added is 5% to 7% of the total mass of the cementitious material, wherein the biomass water reducer is a mycelium ball in a saturated state.

[0021] The amount of biomass shrinkage reducing agent added in the present invention is small, which can not only reduce the cost of concrete materials, but also the micropores generated after water loss will not have a negative impact on the performance of concrete materials, but will improve the freeze-thaw stability of concrete. At the same time, since the mycelium balls can play the role of fibers, the crack resistance of concrete can be improved, thereby further improving the anti-freeze performance of concrete.

[0022] Furthermore, the concrete includes alkali-activated concrete or cement-based concrete.

[0023] Furthermore, the alkali-activated concrete comprises the above-mentioned biomass shrinkage-reducing agent, siliceous and aluminous solid waste, alkali activator, sand, gravel and water. The cement-based concrete comprises the above-mentioned biomass shrinkage-reducing agent, cement, sand, gravel and water.

[0024] Furthermore, the siliceous and aluminous solid waste includes one or more of fly ash, slag, steel slag or phosphogypsum.

[0025] Furthermore, the alkaline activator includes one or both of sodium hydroxide solution and sodium silicate solution.

[0026] Furthermore, the modulus of the sodium silicate solution is 1-2.

[0027] Before use, the modulus of the sodium silicate solution (modulus 3.25) was adjusted to 1-2 using sodium hydroxide particles.

[0028] Furthermore, the amount of the alkali activator added is 10% to 50% of the total mass of the gelling material.

[0029] Furthermore, the water-to-binder ratio is 0.2-0.5.

[0030] It should be noted that cementitious materials refer to the total amount of solid materials other than sand and gravel in the concrete system. In the alkali-activated system, cementitious materials refer to the total mass of silicoaluminous solid waste and sodium hydroxide solid or sodium silicate solid contained in the alkali activator solution. In the cement system, cementitious materials refer to cement.

[0031] Applying fungal mycelium balls to alkali-activated concrete materials that are prone to cracking can not only effectively reduce the drying shrinkage of concrete, but also improve the mechanical properties of concrete. It is easy to operate, easy to construct, low in cost, and suitable for large-scale application. In addition, it can reduce dependence on chemical reagents and reduce the adverse effects of chemical reagents on the environment. It is in line with the concept of green, environmental protection and sustainable development, has high economic, environmental and social benefits, can meet the construction industry's demand for high-performance, environmentally friendly materials, and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is the morphology of the Aspergillus niger mycelium ball; Figure 2 This is a diagram showing the dispersion state of Aspergillus niger mycelium pellets in the mortar material in Example 2; Figure 3 This is a diagram showing the dispersion state of ceramsite in the mortar material in Comparative Example 1; Figure 4 This is a diagram showing the dispersion state of the super absorbent resin (SAP) in the mortar material in Comparative Example 2. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] In order to better illustrate the present invention, further examples are given below.

[0035] The composition of the modified Czapek liquid culture used in the following examples and comparative examples is: 1 g of dipotassium hydrogen phosphate, 0.1 g of magnesium sulfate, 0.5 g of potassium chloride, 0.06 g of ferrous sulfate, 30 g of sucrose, 3 g of sodium nitrate, and 1000 mL of distilled water.

[0036] Example 1 The embodiment of the present invention provides a biomass shrinkage reducing agent, and the preparation method comprises the following steps: The modified Czapek medium was sterilized at 121°C for 20 min, cooled, and the spores of Aspergillus niger were inoculated into the sterilized modified Czapek liquid medium using a microbial inoculation loop to make the spore concentration in the medium 10 8 / mL, cultured in a shaker at 30℃ and 160r / min for 4d, filtered to obtain mycelial balls with a diameter of 0.5-2mm, and sterilized by high pressure at 121℃ for 20min to obtain mycelial balls with an overall moisture content of ≥99%, i.e., the biomass shrinkage reducer.

[0037] The above-mentioned biomass shrinkage reducer is used to prepare alkali-activated mortar material, and the amount of mycelium balls added is 5% of the total amount of cementitious material. Since the moisture content of the mycelium balls is ≥99%, the mass of the mycelium balls themselves is negligible; the selected silicoaluminous solid waste is slag, and the composite alkali activator is a mixture of sodium hydroxide solution and sodium silicate solution. The modulus of the sodium silicate solution is 2 (the modulus of the sodium silicate solution with a modulus of 3.25 is adjusted to 2 with sodium hydroxide), the concentration of the sodium hydroxide solution is 10 mol / L, the amount of sodium hydroxide solution added is 20% of the total amount of the composite activator, and the amount of the composite alkali activator solution is 50% of the mass of the slag, wherein the mass of the cementitious material is the sum of the masses of the slag, the sodium hydroxide in the composite activator solution, and the total mass of the sodium silicate solid; the total water-cement ratio is 0.35.

[0038] Example 2 This embodiment provides an alkali-activated mortar material, which is different from the embodiment 1 only in that the amount of mycelium balls added is 6% of the total amount of cementitious materials, and the rest is exactly the same and will not be repeated here.

[0039] Example 3 This embodiment provides an alkali-activated mortar material, which is different from the embodiment 1 only in that the amount of mycelium balls added is 7% of the total amount of cementitious materials, and the rest is exactly the same and will not be repeated here.

[0040] Example 4 This embodiment provides an alkali-activated mortar material, which is different from Embodiment 2 only in that the diameter of the mycelial balls is 2-4 mm and the number of culture days is 6 days. The rest is exactly the same and will not be repeated here.

[0041] Example 5 This embodiment provides an alkali-activated mortar material, which is different from Example 2 only in that the Aspergillus niger mycelium balls are replaced with Aspergillus oryzae mycelium balls with the same diameter, and the dosage of the mycelium balls is 6% of the total amount of cementitious materials. The rest is exactly the same and will not be repeated here.

[0042] Example 6 This embodiment provides an alkali-activated mortar material, which is different from Example 2 only in that the Aspergillus niger mycelium balls are replaced with Monascus mycelium balls with the same diameter, and the dosage of the mycelium balls is 6% of the total amount of cementitious materials. The rest is exactly the same and will not be repeated here.

[0043] Example 7 This embodiment provides an alkali-activated mortar material, which is different from Example 2 only in that the Aspergillus niger mycelium balls are replaced with Aspergillus koji mycelium balls of the same diameter, and the dosage of the mycelium balls is 6% of the total amount of cementitious materials. The rest is exactly the same and will not be repeated here.

[0044] Example 8 This embodiment provides an alkali-activated mortar material, which is different from Example 2 only in that the Aspergillus niger mycelium balls are replaced with Mucor mycelium balls with the same diameter, and the dosage of the mycelium balls is 6% of the total amount of cementitious materials. The rest is exactly the same and will not be repeated here.

[0045] Example 9 This embodiment provides a cement mortar material, which is prepared in the same manner as the shrinkage reducing agent in Embodiment 2, using P·O42.5 cement, a total water-binder ratio of 0.5, and a mycelium pellet dosage of 6%.

[0046] Comparative Example 1 This comparative example provides an alkali-activated mortar material, which is different from Example 2 only in that the mycelium pellet shrinkage reducer is replaced with ceramsite with a diameter of 2 to 4 mm, and the ceramsite content before water absorption is 6% of the total mass of the cementitious material, and the rest is exactly the same, which will not be repeated here. The optimal diameter and optimal content of ceramsite can be selected for comparison.

[0047] Among them, the expanded clay is soaked in water of the same mass as the amount of water introduced into the mycelium ball in advance, so that the expanded clay absorbs water in advance.

[0048] Comparative Example 2 This comparative example provides an alkali-activated mortar material, which is different from Example 2 only in that the mycelium pellet shrinkage reducer is replaced with a super absorbent resin (SAP) with a diameter of 0.5-2 mm and the added amount is 0.6% of the total amount of the cementitious material. The rest is exactly the same and will not be repeated here.

[0049] The polymer water-absorbing resin is soaked in advance with water of the same mass as the amount of water introduced into the mycelial balls.

[0050] Comparative Example 3 This comparative example provides an alkali-activated mortar material, which is different from Example 2 only in that no shrinkage reducing agent is added.

[0051] Comparative Example 4 This comparative example provides a cement mortar material, which is different from Example 9 only in that no shrinkage reducing agent is added.

[0052] The specific formulas of the alkali-activated mortar cementitious material and the cement-based mortar cementitious material in Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 1.

[0053] Table 1 Unit: g

[0054] Note: NaOH solution and sodium silicate solution are not mixed, but added to the powder separately.

[0055] Performance Testing In order to demonstrate the performance of the alkali-activated slag cementitious materials and cement-based cementitious materials prepared in the embodiments and comparative examples of the present invention, the mortars in the embodiments 1 to 9 and comparative examples 1 to 4 were tested for performance, and the tests were as follows: The drying shrinkage of the specimens was determined according to GB / T 29417-2012 Test method for drying shrinkage and cracking performance of cement mortar and concrete; the compressive strength of the test block was determined according to GB / T 17671-1999 Test method for strength of cement mortar (ISO method); the fluidity of the test block was determined according to GB / T 2419-2005 Test method for fluidity of cement mortar; the setting time was determined according to GB / T 1346-2001 Test method for water consumption, setting time and stability of cement at standard consistency. The results are shown in Table 2.

[0056] Table 2

[0057] It can be seen from Table 2 that compared with the control group (Comparative Example 3) without adding any shrinkage reducing agent, the biomass shrinkage reducing agent (Examples 1-8) was added to the alkali-activated slag mortar. Except that the final setting time and the 7d and 28d compressive strength of Example 4 were slightly reduced, the shrinkage rate of the alkali-activated slag mortar was reduced to varying degrees, and its initial setting time, final setting time and compressive strength were increased to varying degrees. In addition, it can be seen from Example 2 and Comparative Example 3 that when 6% of Aspergillus niger mycelium balls with a diameter of 0.5 to 2 mm are added to the alkali-activated slag mortar, the shrinkage rate of the alkali-activated mortar is the lowest, and the shrinkage rates of 7d and 14d are 0.112% and 0.364% respectively. Compared with Comparative Example 3, the shrinkage rates of 7d and 14d are reduced by 52.54% and 36.14% respectively, and the initial setting time and final setting time are increased by 76.47% and 46.43% respectively, and the 7d and 28d compressive strengths are increased by 8.35% and 7.07% respectively, which shows that under this condition, the slow setting effect of Aspergillus niger mycelium balls is the best. This may be because when the diameter of the Aspergillus niger mycelium balls is small, its specific surface area is large, and the surface of the mycelium balls can carry more metabolites such as polysaccharides. These polysaccharide metabolites have a certain slow setting effect, which slows down the hydration reaction, makes the hydration reaction more sufficient, and has higher compressive strength.

[0058] It can be seen from Comparative Examples 1, 2 and 3 that the 14d shrinkage of the alkali-activated slag cementitious material with ceramsite and SAP is reduced by 24.56% and 22.98% respectively compared with that of Comparative Example 3, but its 7d and 14d shrinkage are higher than those of Example 2. Adding fungal mycelium balls such as Aspergillus oryzae (Example 5), Monascus (Example 6), Koji (Example 7) and Mucor (Example 8) to the alkali-activated slag mortar also has a good effect of reducing shrinkage, and has different improvements in compressive strength, but all are lower than Example 2.

[0059] As shown in Table 2, compared with Comparative Example 3, the addition of SAP will reduce the shrinkage rate of alkali-activated slag mortar, but it will also cause the compressive strength, fluidity, initial setting and final setting time of alkali-activated slag mortar to decrease to varying degrees (Comparative Example 2); although the addition of ceramsite will reduce its 14d shrinkage rate, its 7-day shrinkage rate will increase slightly, and it will also reduce the compressive strength and final setting time of alkali-activated slag cementitious material mortar (Comparative Example 1). According to the literature, the reason for the reduction in compressive strength is mainly related to the pores formed after the water absorbed by SAP is released into the matrix; the addition of ceramsite will also reduce the compressive strength of the alkali-activated system, because the ceramsite itself has a loose structure and low compressive strength.

[0060] It can be seen from Table 2 that, compared with Comparative Example 3, the addition of mycelium pellets does not have a significant adverse effect on the fluidity of the alkali-activated slag mortar, except for Example 3. For Example 3, when the amount of Aspergillus niger mycelium pellets is relatively large, at 7%, the fluidity of the alkali-activated slag mortar is reduced by 8.02% compared with Comparative Example 3. This is because when too many mycelium pellets are added, the water in the mycelium pellets replaces the external free water, and the free water content in the fresh slurry is reduced, thereby reducing the fluidity of the alkali-activated cementitious material to a certain extent.

[0061] It can be seen from Example 9 and Comparative Example 4 that, in the cement mortar material, by adding 6% of Aspergillus niger mycelium balls with a diameter of 0.5~2 mm, the 14d shrinkage rate is reduced by 58.62% compared with Comparative Example 4, and the shrinkage reduction effect is excellent. The 28d compressive strength is increased by 4.69%, and the setting time is also increased, and it also has a certain retarding effect.

[0062] In summary, adding mycelium balls with a diameter of 0.5-2 mm to the alkali-activated system and cement-based system has a significant effect on reducing shrinkage. Compared with traditional shrinkage-reducing materials such as ceramsite and SAP, mycelium balls of a certain size and dosage can also improve the compressive strength of the test block within a certain range, increase the setting time of the mortar, and are more conducive to engineering construction.

[0063] In summary, the present invention is a biomass shrinkage reducing agent developed by utilizing the property of biomaterials to regulate the internal moisture of concrete, which is both environmentally friendly and efficient. The use of fungal mycelium balls not only reduces drying shrinkage, but also improves the overall performance of concrete, such as enhancing crack resistance and mechanical properties. In addition, the method is low-cost, easy to implement, and suitable for various construction projects, with broad application prospects.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A biomass shrinkage reducing agent, characterized in that: The invention comprises a mycelium ball of fungi, wherein the moisture content of the mycelium ball is ≥99%.

2. The biomass shrinkage reducing agent according to claim 1, characterized in that The fungus is of the genus Aspergillus.

3. The biomass shrinkage reducing agent according to claim 2, characterized in that The fungus is at least one of Aspergillus niger, Aspergillus oryzae, Monascus, Aspergillus niger or Mucor.

4. The biomass shrinkage reducing agent according to any one of claims 1 to 3, characterized in that The particle size of the mycelium ball is 0.5mm~4mm.

5. A method for preparing the biomass shrinkage reducing agent according to any one of claims 1 to 4, characterized in that: The steps include: The fungal spores are inoculated into a sterilized liquid culture medium, cultured, filtered, and sterilized to obtain a biomass shrinkage reducing agent.

6. The method for preparing the biomass shrinkage reducing agent according to claim 5, characterized in that: The liquid culture medium comprises: 1 g of dipotassium hydrogen phosphate, 0.1 g of magnesium sulfate, 0.5 g of potassium chloride, 0.06 g of ferrous sulfate, 30 g of sucrose, 3 g of sodium nitrate, and 1000 mL of distilled water; and / or The concentration of fungal spores in the culture medium after inoculation was 10 6 / mL~10 12 / mL; and / or The culture temperature is 25° C. to 35° C., the rotation speed is 150 r / min to 170 r / min, and the culture time is 3 d to 10 d.

7. A concrete, characterized in that: The invention comprises the biomass shrinkage reducing agent according to any one of claims 1 to 4.

8. The concrete according to claim 7, characterized in that It also includes cementitious materials, sand, gravel and water.

9. The concrete according to claim 8, characterized in that The amount of the biomass shrinkage reducing agent added is 5% to 7% of the total mass of the gelling material.

10. The concrete according to any one of claims 7 to 9, characterized in that: The concrete includes alkali-activated concrete or cement-based concrete.

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