Modified compressed hemp ash for ancient building foundation layer and preparation method thereof

Abstract

The application discloses a modified compressed hemp ash for ancient building ground layer and a preparation method thereof. The modified compressed hemp ash comprises a bonding main colloid, a composite toughening colloid and aggregate, and the mass ratio is 1:1.5-2.1:2-4. The bonding main colloid comprises lime milk, wheat starch and cooked tung oil, and the mass ratio is 1:1-2:2-3. The composite toughening colloid comprises soybean dry powder, sticky rice paste and water, and the mass ratio is 1:2.2-3.4:3-5. The mass fraction of the lime milk quality solute is 6-10%. In the application, the soybean dry powder and the sticky rice powder replace the pig blood material. After the soybean dry powder is crosslinked, a three-dimensional elastic network is formed, high-strength bonding toughness is provided, the sticky rice paste improves the water retention and the thick batch smoothness of the mortar, after drying and curing, the pH of the cured layer is stably kept at 7.0-8.0, the alkalinity of the system is greatly reduced, and the hydrolysis corrosion of the alkaline substances on the old wooden fibers and mineral color painting pigments is reduced.

Description

Technical Field

[0001] This invention relates to a restoration material, specifically to a modified pressed hemp ash for the ground layer of ancient buildings, and also to a method for preparing this modified pressed hemp ash. Background Technology

[0002] The complete process of traditional official ground application (one layer of hemp and five layers of ash) is as follows: filling the joints with ash → applying ash → applying hemp ash → pressing hemp ash → medium ash → fine ash; for example... Figure 1 As shown, the first thick layer of leveling mortar after the burlap is laid is called "pressed burlap mortar". Its core function is to compact and wrap the burlap fibers, fill the gaps in the burlap, and eliminate the unevenness after the burlap is laid, so as to lay a smooth base layer for the subsequent medium and fine mortar.

[0003] The traditional standard ratio of pressed hemp ash is 1:2:3.5 for oil-based ash, pig blood ash, and medium brick ash. This has multiple defects that damage the artifacts: 1. The fermented pig blood ash, which plays a strong binding role, is an animal-derived material. In high-temperature and high-humidity environments, it is prone to mold growth and emits a putrid odor. The fermentation process of pig blood produces trace amounts of organic acids, which slowly erode the old wood fibers and the remaining mineral pigments over a long period of time; 2. Oil-based ash has a high oil content, and the oil easily penetrates into the wood's ducts, causing permanent oil staining and discoloration of the wooden components. Later, when applying lacquer or painting Suzhou-style or spiral-patterned enamels, problems such as oil seepage at the bottom layer and blistering and peeling of the painted layer are likely to occur; 3. Traditional pressed hemp ash is generally highly alkaline, with a pH value of 8.6~9.3 after curing. Long-term continuous action accelerates the aging and decomposition of wood and corrodes the original pigments of murals and wooden components.

[0004] Existing improvement solutions mostly use chemical white latex and polyvinyl alcohol glue as a single substitute for pig blood. After the high-molecular chemical materials are cured, they are not breathable and are irreversible, which blocks the natural breathing of wood and easily causes the wooden components to rot and the ground layer to become hollow. In the later secondary repair of cultural relics, they cannot be removed without damage. Single glutinous rice glue and peach gum are not tough enough to meet the mechanical requirements of thick hemp fiber coating with hemp ash, and are prone to large-area cracking. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a modified pressed hemp ash with improved bonding strength and suitable pH value. This invention also provides a method for preparing this pressed hemp ash to further improve its performance.

[0006] Technical solution: The modified pressed hemp lime of the present invention comprises a main binder, a composite toughening colloid, and aggregate in a mass ratio of 1:1.5~2.1:2~4. The main binder comprises lime milk, wheat starch, and calcined tung oil in a mass ratio of 1:1~2:2~3. The composite toughening colloid comprises soybean powder, glutinous rice paste, and water in a mass ratio of 1:2.2~3.4:3~5. The mass fraction of the solute in the lime milk is 6~10%.

[0007] This invention utilizes a bonding agent and a composite toughening agent, completely eliminating heavy metal additives and significantly reducing oil penetration while retaining the natural waterproof and anti-corrosion properties of tung oil. Wheat starch colloid enhances the plasticity of the mortar and the adhesion of the hemp coating. Soybean powder and glutinous rice flour are both edible natural materials, replacing pig blood. After cross-linking, soybean powder forms a three-dimensional elastic network, providing high-strength bonding toughness. Glutinous rice paste improves the water retention and smoothness of thick mortar layers. After drying and curing, its deformation capacity is close to that of pig blood, allowing it to slightly stretch and deform with the hemp cloth, inhibiting large-area cracking of thick-layer pressed hemp mortar. The pH of the cured layer is stable at 7.0~8.0, significantly reducing the alkalinity of the system and minimizing the hydrolytic corrosion of old wood fibers and mineral pigments by alkaline substances.

[0008] Preferably, the mass ratio of the binder, the composite toughening colloid, and the aggregate is 1:1.7~1.9:3.3~3.7.

[0009] Preferably, the mass fraction of the lime milk solute is 7-9%. More preferably, the mass fraction of the lime milk solute is 7.5-8.5%.

[0010] Preferably, the mass ratio of lime milk, wheat starch, and tung oil is 1:1.3~1.7:2.3~2.7. More preferably, the mass ratio of lime milk, wheat starch, and tung oil is 1:1.4~1.6:2.4~2.6.

[0011] Preferably, in order to shorten the drying cycle, reduce the shrinkage and cracking rate, and improve the bonding strength, the mass ratio of soybean powder, glutinous rice paste, and water is 1:2.3~2.9:3.5~4.5. More preferably, the mass ratio of soybean powder, glutinous rice paste, and water is 1:2.4~2.6:3.8~4.2.

[0012] Preferably, the aggregate is medium brick ash with a moisture content of ≤2% and a mesh size of 20~40.

[0013] Preferably, the glutinous rice paste is made by cooking glutinous rice flour and water, with the glutinous rice flour accounting for 15-28% by weight. More preferably, the glutinous rice flour accounts for 23-27% by weight.

[0014] The aforementioned method for preparing modified pressed hemp ash is as follows:

[0015] (1) Prepare the main binder: Heat the tung oil to 40~70℃, add wheat starch and mix evenly, then add lime milk drop by drop; after the addition is complete, maintain a constant temperature and stir continuously for 30~40 minutes, filter, and cool to room temperature;

[0016] (2) Preparation of composite toughening colloid: Mix soybean powder with water at 30~45℃, add glutinous rice paste, stir evenly, seal, and let it mature at room temperature for 10~14h;

[0017] (3) Mix the main binder and the composite toughening binder, add the aggregate, and stir evenly to obtain modified pressed hemp ash.

[0018] Preferably, in order to reduce the drying shrinkage cracking rate, improve the bonding strength, and reduce the difficulty of removing the cured layer, the cooking temperature in step (1) is 55~65℃. More preferably, the cooking temperature is 60±2℃.

[0019] Preferably, in step (2), the water temperature is 35~45℃.

[0020] Preferably, in step (2), after stirring evenly, the consistency is adjusted with water so that it does not drip when applied in a single coat and the thickness of a single coat does not exceed 2 mm.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. Excellent mechanical properties: The composite toughened colloid has better toughness than traditional pig blood material, and the modified pressed hemp ash has a lower rate of drying shrinkage and cracking under thick hemp coating conditions. No surface cracks were found after dry and wet cycle testing. It can be used stably for a long time in both outdoor and high-humidity indoor ancient buildings; 2. Reversible and removable: It can be dissolved and removed non-destructively with warm water during the secondary repair of cultural relics; 3. Reduces the problem of grease seeping into wood and causing damage to cultural relics, does not block the wood ducts, and does not block the wood's breathability. Attached Figure Description

[0022] Figure 1 A schematic diagram of the layering positions in the five-step process of pressing hemp ash in the existing technology;

[0023] Figure 2 Photograph of the cured layer formed by the modified pressed hemp ash prepared in Example 1;

[0024] Figure 3 Photograph of the cured layer formed by the modified pressed hemp ash prepared in Comparative Example 1;

[0025] Figure 4 Photograph of the cured layer formed by the modified pressed hemp ash prepared in Comparative Example 2;

[0026] Figure 5 Photograph of the cured layer formed by the modified pressed hemp ash prepared in Comparative Example 3;

[0027] Figure 6 This is a photograph of the cured layer formed by the modified pressed hemp ash prepared in Comparative Example 4. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0029] Example 1: Preparation of Modified Pressed Hemp Ash

[0030] 1. Prepare the main binder (10kg): Take 5kg of boiled tung oil and heat it to 60℃. Add 3kg of edible wheat starch and stir thoroughly until there is no dry powder clumping. Slowly add 2kg of 8% lime milk. After all the lime milk has been added, stir at a constant temperature for 35 minutes and cool to room temperature for later use.

[0031] 2. Preparation of composite toughening colloid (18kg):

[0032] Glutinous Rice Paste: Mix 1.2 kg of glutinous rice flour with 4.8 kg of water, place in a 100℃ water bath, and stir continuously at a speed not exceeding 80 r / min until gelatinized. Keep warm for 60–90 minutes until gelatinized. During the cooking process, add water in small amounts several times to maintain the stability of the total mass of the glutinous rice paste and prevent large fluctuations in concentration. After gelatinization, stop heating and allow it to cool naturally to room temperature for later use. Take 2.4 kg of food-grade dried soybean powder, add 9.6 kg of 40℃ warm water to dissolve completely and stir evenly. Add 6 kg of cooked and cooled glutinous rice paste, stirring evenly at a speed not exceeding 80 r / min. Seal and let it mature at room temperature for 12 hours for later use.

[0033] 3. Prepare a homogeneous bonding substrate: Mix 10 kg of the bonding agent and 18 kg of the composite toughening agent at room temperature, and stir continuously for 5 minutes until the system is homogeneous and free of stratification.

[0034] 4. Mixing the finished pressed hemp ash: Add 35kg of 20~40 mesh brick ash, dried to a moisture content of ≤2%, to the bonding base in batches. Add water in small amounts several times to adjust the consistency until a thick layer does not drip when applied, and the finished modified pressed hemp ash is obtained.

[0035] Comparative Example 1: The preparation process and the amount of other raw materials used in this comparative example are exactly the same as those in Example 1. The difference is that no composite toughening colloid was added. Only the main adhesive colloid and the brick ash in the blue brick were used to prepare the pressed hemp ash.

[0036] Comparative Example 2: The preparation process and the distribution ratio of the remaining groups in this comparative example are completely consistent with those in Example 1. The lime milk parameters of the main binder are adjusted, and 4 kg of 4% low-concentration lime milk is used to replace 2 kg of the original 8% lime milk.

[0037] Comparative Example 3: The raw material ratio and other preparation processes of this comparative example are completely consistent with those of Example 1, except that the constant temperature for cooking the binder colloid is adjusted to 40℃.

[0038] Comparative Example 4: The preparation process and the proportions of each component except for the glutinous rice paste in this comparative example are completely consistent with those in Example 1. The difference is that the amount of glutinous rice paste in the composite toughening colloid is adjusted from 6 kg to 8 kg.

[0039] The modified pressed hemp ash prepared in Examples 1 and Comparative Examples 1 to 4 was spread on the surface of hemp cloth, and the thickness of the ash layer was controlled to be 3.0 mm (the sample thickness is consistent in Figures 2 to 6). After spreading, the samples were placed in the shade to dry for 28 days under the conditions of 23±2℃ and 50±5% relative humidity, avoiding direct sunlight and strong winds, and no heating was used for drying. After curing, the samples were completely dried, and performance tests were carried out on each sample. The test parameters and surface structure are shown in Table 1 and Figures 2 to 6.

[0040] Table 1:

[0041]

[0042] Test data and Figures 2 to 6 The results show that the modified hemp ash prepared in Example 1 has a curing pH of 7.2, indicating weak alkalinity, which helps protect the wood; the drying shrinkage and cracking rate is 0%, and the bonding strength is 1.2 MPa, effectively adhering to hemp fibers and preventing curing cracking and deformation; the softening coefficient is 0.92, indicating that it is not easily softened by long-term immersion in cold water and has strong durability; it is made entirely of natural hydrophilic organic materials such as glutinous rice, soybean powder, and lime milk, which can be dissolved and removed without damage during secondary restoration of cultural relics by prolonged immersion in warm water. The drying cycle is 5 days, which is suitable for construction needs.

[0043] Comparative Example 1 lacked a composite toughening colloid, Comparative Example 2 had unbalanced lime slurry parameters, Comparative Example 3 had insufficient boiling temperature, and Comparative Example 4 had excessive glutinous rice paste content; all of these factors led to a decrease in the final performance of the pressed lime. It is evident that the formulation of this invention has a reasonable combination of components and precise process parameters, effectively balancing the material's mechanical properties, crack resistance, water resistance, and construction efficiency. Furthermore, it is free of heavy metals and animal blood throughout the entire process, and its performance is significantly superior to traditional and improved formulations, meeting the standardized requirements for the restoration of ancient buildings and cultural relics.

Claims

1. A modified pressed hemp ash, characterized in that, The mixture comprises a binder, a composite toughening colloid, and aggregates in a mass ratio of 1:1.5~2.1:2~4. The binder comprises lime milk, wheat starch, and tung oil in a mass ratio of 1:1~2:2~3. The composite toughening colloid comprises soybean powder, glutinous rice paste, and water in a mass ratio of 1:2.2~3.4:3~5. The mass fraction of the lime milk solute is 6~10%.

2. The modified pressed hemp ash according to claim 1, characterized in that, The mass ratio of the binder, the composite toughening colloid, and the aggregate is 1:1.7~1.9:3.3~3.

7.

3. The modified pressed hemp ash according to claim 1, characterized in that, The mass fraction of the solute in the lime milk is 7-9%.

4. The modified pressed hemp ash according to claim 1, characterized in that, The mass ratio of lime milk, wheat starch, and boiled tung oil is 1:1.3~1.7:2.3~2.

7.

5. The modified pressed hemp ash according to claim 1, characterized in that, The mass ratio of soybean powder, glutinous rice paste, and water is 1:2.3~2.9:3.5~4.

5.

6. The modified pressed hemp ash according to claim 1, characterized in that, The aggregate is medium brick ash with a moisture content of ≤2% and a mesh size of 20~40.

7. The modified pressed hemp ash according to claim 1, characterized in that, Glutinous rice paste is made by boiling glutinous rice flour and water, with glutinous rice flour accounting for 15-28% of the total mass.

8. The method for preparing the modified pressed hemp ash according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Prepare the main binder: Heat the tung oil to 40~70℃, add wheat starch and mix evenly, then add lime milk drop by drop; after the addition is complete, maintain a constant temperature and stir continuously for 30~40 minutes, filter, and cool to room temperature; (2) Preparation of composite toughening colloid: Mix soybean powder with water at 30~45℃, add glutinous rice paste, stir evenly, seal, and let it mature at room temperature for 10~14h; (3) Mix the main binder and the composite toughening colloid, add the aggregate, and stir evenly to obtain the modified pressed hemp ash.

9. The manufacturing method according to claim 8, characterized in that, In step (1), the cooking temperature is 55~65℃.

10. The manufacturing method according to claim 8, characterized in that, In step (2), the water temperature is 35~45℃.

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