Lightweight concrete and preparation method thereof

Abstract

The lightweight concrete is prepared from the following raw materials in parts by weight: 350 to 500 parts of cement, 160 to 220 parts of water, 50 to 70 parts of ceramsite, 50 to 80 parts of slag powder, 1 to 3 parts of a water reducing agent, 15 to 20 parts of modified pineapple leaf fibers and 35 to 55 parts of modified rice hull ash, and the modified pineapple leaf fibers are prepared from pineapple leaf fibers by adopting chlorhexidine. The lightweight concrete is used for solving the technical problems of low breaking strength and low compressive strength of the lightweight concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to lightweight concrete and a preparation method thereof. Background Art

[0002] Lightweight concrete is a concrete material prepared with lightweight aggregate or foaming technology. It has the characteristics of low density, good thermal insulation performance, and light weight. It is widely used in construction, roads, bridges, civil engineering and other fields.

[0003] Lightweight concrete is achieved by using lightweight aggregates to reduce its own weight. There are many types of lightweight aggregates, with pumice, ceramsite, and slag being common. However, the addition of lightweight aggregates can introduce new challenges. The presence of pores within lightweight aggregates increases the interfacial strength between the aggregate and the cement paste, increasing the brittleness of the concrete and reducing its flexural strength. Furthermore, the inherent strength of lightweight aggregates is lower than that of traditional aggregates like crushed stone, resulting in a reduction in the concrete's compressive strength. Therefore, it is necessary to enhance the flexural and compressive strengths of lightweight concrete. Summary of the Invention

[0004] The invention provides a lightweight concrete and a preparation method thereof, which are used to solve the technical problem that the existing lightweight concrete has low flexural strength and compressive strength.

[0005] In view of this, the present invention provides a lightweight concrete, which includes the following raw materials in parts by weight: 350-500 parts of cement, 160-220 parts of water, 50-70 parts of ceramsite, 50-80 parts of slag powder, 1-3 parts of water reducer, 15-20 parts of modified pineapple leaf fiber, and 35-55 parts of modified rice husk ash. The modified pineapple leaf fiber is prepared by modifying the pineapple leaf fiber with hemoglobin.

[0006] Optionally, the modified pineapple leaf fiber is prepared by the following method:

[0007] A1: Grind pineapple leaf fibers, add them to a lithium chloride / dimethyl sulfoxide solution, and mix thoroughly to obtain a cellulose solution;

[0008] adding hemin to the dimethyl sulfoxide solution and mixing them evenly to obtain a hemin solution;

[0009] A2: Add the hemin solution to the cellulose solution, mix well, heat to increase the temperature, react, and after the reaction is completed, add water, mix well, centrifuge, take the solid, wash, and dry to obtain modified pineapple leaf fiber.

[0010] Furthermore, the modified pineapple leaf fiber is prepared by the following method:

[0011] A1: Grind pineapple leaf fibers, add them to an 8% lithium chloride / dimethyl sulfoxide solution, and mix thoroughly to obtain a cellulose solution;

[0012] Adding hemin to a 0.1% dimethyl sulfoxide solution and mixing well to obtain a hemin solution;

[0013] A2: Add the hemin solution to the cellulose solution, mix well, heat to 80-100°C, and react for 1-3 hours. After the reaction is complete, add water, mix well, and centrifuge. The solid is collected and washed 3-5 times with a 0.1% dimethyl sulfoxide solution, then 3-5 times with water, and dried to obtain modified pineapple leaf fiber.

[0014] In step A1, the amount of lithium chloride / dimethyl sulfoxide solution added to 1g of pineapple leaf fiber is 10-20mL, the amount of dimethyl sulfoxide solution added to 1g of oxidized hemoglobin is 10-20mL, and the amount of water added in step A2 is 4-6 times the total volume of the hemin solution and the cellulose solution.

[0015] Optionally, the weight ratio of the pineapple leaf fiber to hemin is 1:(0.3-0.6).

[0016] Optionally, the pineapple leaf fiber is pretreated by the following method before use:

[0017] B1: adding pineapple leaf fiber to the enzyme solution, adjusting the pH value, heating, allowing to stand, and removing the solid matter to obtain enzymatically hydrolyzed pineapple leaf fiber;

[0018] B2: adding the enzymatically hydrolyzed pineapple leaf fiber to the rinsing liquid, heating the solution again, allowing the solution to stand, taking the solution out, washing the solution, and drying the solution to obtain the pretreated pineapple leaf fiber.

[0019] Furthermore, the pineapple leaf fiber is pretreated by the following method before use:

[0020] B1: Add pineapple leaf fiber to an enzyme solution, adjust the pH to 4.5-5.5 with 30% hydrochloric acid solution, heat to 40-50°C, let stand for 4-5 hours, remove the solid matter, and obtain enzymatically hydrolyzed pineapple leaf cellulose;

[0021] B2: adding the enzymatically hydrolyzed pineapple leaf cellulose to the rinse solution, heating the solution to 80-90°C again, allowing the solution to stand for 60-90 minutes, taking the solution out, washing the solution with water 3-5 times, and drying the solution to obtain pretreated pineapple leaf fiber;

[0022] The amount of enzyme solution added to 1g of pineapple leaf fiber in step B1 is 40-50mL, and the amount of rinsing solution added to 1g of enzymatically hydrolyzed pineapple leaf fiber in step B2 is 20-40mL.

[0023] Optionally, the enzyme solution is prepared by adding pectinase and cellulase into water.

[0024] Furthermore, the enzyme solution is prepared by adding pectinase and cellulase into water and mixing them evenly; the weight ratio of pectinase to cellulase is 1:1, and the amount of water added is 10-30 mL per 1 g of the total weight of pectinase and cellulase.

[0025] Optionally, the rinsing liquid is prepared by adding sodium silicate, sodium hydroxide and hydrogen peroxide into water.

[0026] Furthermore, the rinsing liquid is prepared by adding sodium silicate, sodium hydroxide, and hydrogen peroxide into water and mixing them uniformly; and the weight ratio of sodium silicate, sodium hydroxide, and hydrogen peroxide is 1:(0.2-0.3):(1-3), and the amount of water added to each 1g of sodium silicate is 20-40mL.

[0027] Optionally, the modified rice husk ash is prepared by the following method: sieving the rice husk ash, performing acidification treatment, then calcining the rice husk ash at high temperature, and then performing ultrasonic treatment on the calcined rice husk ash to obtain the modified rice husk ash.

[0028] Furthermore, the modified rice husk ash is prepared by the following method: the rice husk ash is passed through an 80-120 mesh sieve, placed in a 3% hydrochloric acid solution for acidification for 0.5-1.5 hours, and then calcined in an air atmosphere with an air flow rate of 0.3-0.8 m 3 / h, the calcination temperature is 550-850°C, the calcination time is 2-5h, after the calcination is completed, the calcined rice husk ash is mixed with ice water, rapidly cooled, and then subjected to ultrasonic treatment for 20-40min to obtain modified rice husk ash;

[0029] The amount of hydrochloric acid solution added to every 1g of rice husk ash is 8-20mL, and the weight ratio of the calcined rice husk ash to ice water is 1:(80-120).

[0030] Optionally, the water reducer is any one of a naphthalene-based high-efficiency water reducer, a polycarboxylic acid high-efficiency water reducer, and a lignin sulfonate water reducer.

[0031] A method for preparing lightweight concrete comprises the following steps:

[0032] S1: adding modified pineapple leaf fiber to a portion of water, performing ultrasonic dispersion, and then adding modified rice husk ash to obtain a mixture;

[0033] S2: Mix cement, remaining water, ceramsite and slag powder evenly to obtain a mixing material;

[0034] S3: After the mixture, stirring material and water reducing agent are evenly mixed, they are poured into a mold and cured to obtain lightweight concrete.

[0035] Furthermore, a method for preparing lightweight concrete comprises the following steps:

[0036] S1: adding the modified pineapple leaf fiber into 1 / 5 of the total water volume, performing ultrasonic dispersion, and then adding the modified rice husk ash to obtain a mixture;

[0037] S2: Mix cement, remaining water, ceramsite and slag powder evenly to obtain a mixing material;

[0038] S3: After the mixture, stirring material and water reducing agent are evenly mixed, pour them into the mold and cure for 45-55 hours to obtain lightweight concrete.

[0039] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0040] 1. The present invention adopts hemin chloride to modify pineapple leaf fiber, obtains modified pineapple leaf fiber, can make pineapple leaf fiber surface grafted hemin chloride, improve the cleanliness of pineapple leaf fiber inside, make internal structure more dense and orderly, directly strengthen the mechanical property of pineapple leaf fiber, make it have higher tensile strength and toughness, can bear larger stress in concrete; In addition, the surface roughness of pineapple leaf fiber after modification increases, and the contact area with other components of concrete increases, so that chemical bonding is strengthened, and active groups such as hydroxyl, carboxyl and cement hydration products on the modified pineapple leaf fiber surface can chemically react, form stronger chemical bonding, further improve the bond strength of pineapple leaf fiber and matrix, thereby can further improve concrete flexural strength and the ultimate compressive strength.

[0041] 2. The present invention pre-treats pineapple leaf fiber before use, carries out enzymolysis and rinsing to pineapple leaf fiber, utilizes pectinase and cellulase to be used in combination, can remove the pectin in pineapple leaf fiber, can also decompose the cellulose in the cell wall, fully remove pineapple leaf fiber epidermis impurities, and do not damage the pineapple leaf fiber internal structure, rinsing can further remove the enzymolysis agent and other impurities remaining after the enzymolysis, makes pineapple leaf fiber purer, contributes to better play the effect in concrete, thereby is convenient to improve the compressive strength and the flexural strength of lightweight concrete.

[0042] 3. The present invention uses modified rice husk ash, which not only reuses agricultural waste, saves resources and protects the environment, but also can fill the pores of concrete to increase the density, thereby improving the compressive strength and flexural strength of concrete; the specific surface area of the modified rice husk ash is increased, which enhances its volcanic ash activity and facilitates better performance. DETAILED DESCRIPTION

[0043] In order to make those skilled in the art better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

[0044] The cement is P.042.5 silicate cement, the ceramsite particle size is 10-30mm, the slag powder is S95 grade slag powder, the pectinase activity is 15000U / mg, the cellulase activity is 400U / mg, and the water reducer is a polycarboxylic acid high-efficiency water reducer.

[0045] Preparation Example

[0046] Preparation Example 1

[0047] A modified pineapple leaf fiber is prepared by the following method:

[0048] A1: 2 kg of pineapple leaf fiber was crushed and added to 30 L of an 8% lithium chloride / dimethyl sulfoxide solution. The mixture was mixed to obtain a cellulose solution.

[0049] 0.6 kg of hemin was added to 9 L of 0.1% dimethyl sulfoxide solution and mixed well to obtain a hemin solution;

[0050] A2: Add the hemin solution to the cellulose solution, mix well, heat to 90°C, and react for 2 hours. After the reaction is completed, add water 5 times the total volume of the hemin solution and cellulose solution, mix well, centrifuge, collect the solid, wash it first with a 0.1% dimethyl sulfoxide solution 5 times, then wash it with water 5 times, and dry it to obtain modified pineapple leaf fiber.

[0051] Preparation Example 2

[0052] A modified pineapple leaf fiber is different from Preparation Example 1 in that the amount of hemin added is different. The amount of hemin added in Preparation Example 2 is 1 kg.

[0053] Preparation Example 3

[0054] A modified pineapple leaf fiber is different from Preparation Example 1 in that the amount of hemin added is different. The amount of hemin added in Preparation Example 3 is 1.2 kg.

[0055] Preparation Example 4

[0056] A modified rice husk ash is prepared by the following method:

[0057] 2 kg of rice husk ash was passed through a 100 mesh sieve and placed in 30 L of 3% hydrochloric acid solution for acidification for 1 h, and then calcined in an air atmosphere with an air flow rate of 0.6 m 3 / h, the calcination temperature is 700℃, the calcination time is 3.5h, and after the calcination is completed, the calcined rice husk ash is mixed with ice water, rapidly cooled, and then ultrasonically treated for 30min to obtain modified rice husk ash, wherein the weight ratio of the calcined rice husk ash to ice water is 1:100.

[0058] Example

[0059] Example 1

[0060] A lightweight concrete, the raw material ratio of which is shown in Table 1.

[0061] A method for preparing lightweight concrete comprises the following steps:

[0062] S1: The modified pineapple leaf fiber prepared in Preparation Example 1 is placed in water with a volume of 1 / 5 of the total volume, and ultrasonically dispersed, and then the modified rice husk ash prepared in Preparation Example 4 is added to obtain a mixture;

[0063] S2: Mix cement, remaining water, ceramsite and slag powder evenly to obtain a mixing material;

[0064] S3: After the mixture, stirring material and water reducing agent are evenly mixed, pour them into the mold and cure for 50 hours to obtain lightweight concrete.

[0065] Examples 2-8

[0066] A lightweight concrete, which differs from Example 1 in that the raw materials of the concrete are different, and the raw material ratios are shown in Table 1.

[0067] Table 1 Weight of concrete raw materials (kg)

[0068]

[0069] Example 9

[0070] A lightweight concrete, which differs from Example 7 in that the modified pineapple leaf fiber has a different source and is prepared using Preparation Example 2.

[0071] Example 10

[0072] A lightweight concrete, which differs from Example 7 in that the modified pineapple leaf fiber has a different source and is prepared using Preparation Example 3.

[0073] Example 11

[0074] A lightweight concrete, which differs from Example 9 in that the pineapple leaf fibers in the modified pineapple leaf fibers are pretreated by the following method before use:

[0075] B1: Add pectinase and cellulase to water and mix well to prepare enzyme solution; the weight ratio of pectinase to cellulase is 1:1, and the amount of water added is 20 mL per the total weight of 1 g of pectinase and cellulase;

[0076] Add pineapple leaf fiber to the enzyme solution, adjust the pH value to 5 with 30% hydrochloric acid solution, heat to 45°C, let it stand for 4.5 hours, remove the solid matter, and obtain enzymatically hydrolyzed pineapple leaf cellulose;

[0077] B2: Sodium silicate, sodium hydroxide, and hydrogen peroxide are added to water and mixed uniformly; the weight ratio of sodium silicate, sodium hydroxide, and hydrogen peroxide is 1:0.25:2, and the amount of water added is 30 mL per 1 g of sodium silicate;

[0078] The enzymatically hydrolyzed pineapple leaf cellulose was added to the rinse solution, heated again to 85° C., allowed to stand for 70 minutes, taken out, washed with water 5 times, and dried to obtain pretreated pineapple leaf fiber;

[0079] The amount of enzyme solution added to each 1g of pineapple leaf fiber in step B1 is 45mL, and the amount of rinsing solution added to each 1g of enzymatically hydrolyzed pineapple leaf fiber in step B2 is 30mL.

[0080] Comparative Example

[0081] Comparative Example 1

[0082] A lightweight concrete, which differs from Example 1 in that modified pineapple leaf fiber is not added to the raw materials.

[0083] Comparative Example 2

[0084] A lightweight concrete, which differs from Example 1 in that an equal amount of modified pineapple leaf fiber in the raw materials is replaced by unmodified pineapple leaf fiber.

[0085] Comparative Example 3

[0086] A lightweight concrete, which differs from Example 1 in that modified rice husk ash is not added to the raw materials.

[0087] Comparative Example 4

[0088] A lightweight concrete, which differs from Example 1 in that an equal amount of modified rice husk ash in the raw materials is replaced by unmodified rice husk ash.

[0089] Comparative Example 5

[0090] A lightweight concrete, which differs from Example 1 in that modified pineapple leaf fiber and modified rice husk ash are not added to the raw materials.

[0091] Performance testing

[0092] The following tests were performed on the lightweight concrete in Examples 1-11 and Comparative Examples 1-4:

[0093] Take lightweight concrete samples of the same specification of 100mm×100mm×100mm, and after curing for 28 days, clean and dry the surface.

[0094] 28d compressive strength: The 28d compressive strength of the concrete specimens was measured in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)". The test results are shown in Table 2.

[0095] Flexural strength: The flexural strength of the concrete specimens was measured in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)". The test results are shown in Table 2.

[0096] Table 2 Test results

[0097] project 28d compressive strength (MPa) Flexural strength (MPa) Example 1 48.9 13.2 Example 2 51.7 15.1 Example 3 51.5 14.9 Example 4 53.6 16.6 Example 5 53.4 16.2 Example 6 53.3 16.3 Example 7 55.5 17.4 Example 8 55.2 17.1 Example 9 57.3 18.9 Example 10 57.1 18.5 Example 11 58.9 20.8 Comparative Example 1 31.4 6.8 Comparative Example 2 40.9 10.1 Comparative Example 3 35.6 8.6 Comparative Example 4 43.8 11.7 Comparative Example 5 28.5 4.3

[0098] As can be seen from Table 2, the lightweight concrete and preparation method thereof of the present invention improve the compressive strength and flexural strength of the concrete and enhance the mechanical properties through the synergistic effect of the raw materials. Among them, the lightweight concrete has a 28d compressive strength of 48.9-58.9 MPa and a flexural strength of 13.2-20.8 MPa.

[0099] In combination with Example 1 and Comparative Examples 1-5, it can be seen that the 28d compressive strength of concrete in Example 1 is 48.9 MPa, and the flexural strength is 13.2 MPa, which are better than Comparative Examples 1-5, indicating that it is more appropriate to add modified pineapple leaf fiber and modified rice husk ash to the raw materials of concrete. The surface of the modified pineapple leaf fiber can react chemically with the cement hydration product to form a stronger chemical bond, thereby improving the bonding strength between the pineapple leaf fiber and the matrix, thereby improving the flexural strength and compressive strength of the concrete. The modified rice husk ash can also be filled in the pores of the concrete, increasing the density, which is convenient for improving the compressive strength and flexural strength of the concrete.

[0100] It can be seen from Examples 1-3 that in Example 2, the 28d compressive strength of concrete is 51.7MPa, and the flexural strength is 15.1MPa, which is better than other embodiments. It shows that the addition of the modified pineapple leaf fiber in Example 2 is more suitable. The addition of the modified pineapple leaf fiber is too little and does not have a better effect. The addition of the modified pineapple leaf fiber is too much and easily produces self-agglomeration, affecting the dispersibility in concrete, and then affecting the performance of the effect, affecting the mechanical properties of concrete.

[0101] Combining Example 2 and Examples 4-5, it can be seen that the 28d compressive strength of the concrete in Example 4 is 53.6 MPa and the flexural strength is 16.6 MPa, which are better than those in other examples, indicating that the amount of modified rice husk ash added in Example 4 is more appropriate. If the amount added is too little, it will not have a better effect. If the amount added is too much, the normal hydration of cement will be inhibited. The modified rice husk ash has strong water absorption. Excessive addition may cause the concrete to shrink too much during the drying process, resulting in cracks, thereby affecting the mechanical strength of the concrete.

[0102] It can be seen from Examples 5-8 that, except for the modified pineapple leaf fiber and the modified rice husk ash, the other ingredients in the raw materials have little effect on the performance of the concrete.

[0103] It can be seen from Example 7 and Example 9-10 that in Example 9, the 28d compressive strength of concrete is 57.3MPa, and the flexural strength is 18.9MPa, which is better than other embodiments. It shows that it is more suitable to prepare the modified pineapple leaf fiber using Preparation Example 2, which means that the addition of the hemin in Preparation Example 2 is more suitable. The addition is too little and does not have a better effect. The addition is too much, which can cause the hemin to produce homopolymerization, hindering the reaction between it and the pineapple leaf fiber active group, which can affect the esterification efficiency, and can also reduce the mechanical properties of the pineapple leaf fiber, thereby affecting the compressive strength and flexural strength of concrete.

[0104] It can be seen from Example 9 and Example 11 that in Example 11, concrete 28d compressive strength is 58.9MPa, and flexural strength is 20.8MPa, which is better than Example 9. It is more suitable to show that pineapple leaf fiber carries out pre-treatment before use, the pectin in pineapple leaf fiber can be removed, the cellulose in the cell wall can also be decomposed, the pineapple leaf fiber epidermis impurity is fully removed, and the pineapple leaf fiber internal structure is not damaged, and rinsing can further remove the enzymolysis agent and other impurities remaining after the enzymolysis, making pineapple leaf fiber purer, helping to better perform the effect in concrete, thereby being convenient to improving the compressive strength and the flexural strength of lightweight concrete.

[0105] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lightweight concrete, characterized by: The method comprises the following raw materials in parts by weight: 350-500 parts of cement, 160-220 parts of water, 50-70 parts of ceramsite, 50-80 parts of slag powder, 1-3 parts of water reducer, 15-20 parts of modified pineapple leaf fiber, and 35-55 parts of modified rice husk ash. The modified pineapple leaf fiber is prepared by modifying the pineapple leaf fiber with hemoglobin.

2. The lightweight concrete according to claim 1, characterized in that: The modified pineapple leaf fiber is prepared by the following method: A1: Grind pineapple leaf fibers, add them to a lithium chloride / dimethyl sulfoxide solution, and mix thoroughly to obtain a cellulose solution; adding hemin to the dimethyl sulfoxide solution and mixing them evenly to obtain a hemin solution; A2: Add the hemin solution to the cellulose solution, mix well, heat to increase the temperature, react, and after the reaction is completed, add water, mix well, centrifuge, take the solid, wash, and dry to obtain modified pineapple leaf fiber.

3. The lightweight concrete according to claim 2, characterized in that: The weight ratio of the pineapple leaf fiber to the hemin is 1:(0.3-0.6).

4. The lightweight concrete according to claim 2, characterized in that: The pineapple leaf fiber is pretreated by the following method before use: B1: adding pineapple leaf fiber to the enzyme solution, adjusting the pH value, heating, allowing to stand, and removing the solid matter to obtain enzymatically hydrolyzed pineapple leaf fiber; B2: adding the enzymatically hydrolyzed pineapple leaf fiber to the rinsing liquid, heating the solution again, allowing the solution to stand, taking the solution out, washing the solution, and drying the solution to obtain the pretreated pineapple leaf fiber.

5. The lightweight concrete according to claim 4, characterized in that: The enzyme solution is prepared by adding pectinase and cellulase into water.

6. The lightweight concrete according to claim 4, characterized in that: The rinsing liquid is prepared by adding sodium silicate, sodium hydroxide and hydrogen peroxide into water.

7. The lightweight concrete according to claim 1, characterized in that: The modified rice husk ash is prepared by the following method: sieving the rice husk ash, performing acidification treatment, then performing high-temperature calcination, and then performing ultrasonic treatment on the calcined rice husk ash to obtain the modified rice husk ash.

8. The lightweight concrete according to claim 1, characterized in that: The water reducer is any one of a naphthalene-based high-efficiency water reducer, a polycarboxylic acid high-efficiency water reducer, and a lignin sulfonate-based water reducer.

9. A method for preparing lightweight concrete according to any one of claims 1 to 8, characterized in that: The steps include: S1: adding modified pineapple leaf fiber to a portion of water, performing ultrasonic dispersion, and then adding modified rice husk ash to obtain a mixture; S2: Mix cement, remaining water, ceramsite and slag powder evenly to obtain a mixing material; S3: After the mixture, stirring material and water reducing agent are evenly mixed, they are poured into a mold and cured to obtain lightweight concrete.

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