Development and Performance Study of Composite Protein Foaming Agent Based on Human Hair Residue

Abstract

The instability and collapse of boreholes during coal seam gas extraction significantly affect the effectiveness of gas extraction. In response, this study selected human hair residue as the base material for composite protein foaming agents, leveraging the high protein content of animal hoof and hair materials to develop a high-strength, high-permeability, and environmentally friendly new type of foam concrete. This research found that the optimal ratio of foaming agent base solution to water is 1:4 when sodium hydroxide is used for protein hydrolysis. Comparing the foaming effects of sodium dodecyl sulfate (K12), α-sodium alpha-alkenyl sulfonate (AOS), sodium lauryl polyoxyethylene ether sulfate (SLS), and sodium dodecyl benzene sulfonate (LAS), sodium lauryl polyoxyethylene ether sulfate (SLS) exhibited the best foaming performance, while α-sodium alpha-alkenyl sulfonate (AOS) had the best foam stability. The optimal foam performance was achieved by mixing 2.0 g per liter of sodium lauryl polyoxyethylene ether sulfate and 0.3% calcium stearate. The experimental results showed that this foam concrete, with 25 mL of foaming agent, has a high strength exceeding 11 MPa and a high permeability with an average of 2.13 MD. This paper utilizes environmentally friendly materials and preparation processes. By using renewable resources such as human hair residue as raw materials, it helps reduce the dependence on natural resources and promotes sustainable development. This research demonstrates significant sustainability and provides the mining industry with an eco-friendly and efficient solution, with the potential to achieve positive economic and environmental benefits in practical applications.

1. Introduction

Deep coal seams typically exhibit the “three high, two strong, and one low” characteristics, namely high gas pressure, high geothermal temperature, high geostress, strong disturbance, strong time effect, and low permeability. During drilling and extraction, the collapse of the borehole wall is a common occurrence [1,2] leading to the blockage of gas extraction channels and affecting the drilling utilization rate, the service cycle of extraction, and the total gas extraction volume [3,4,5,6]. Current common casing techniques for soft coal seams often encounter problems such as coal dust clogging the casing [7] and high stress flattening the casing [8]. As a common casing material for soft coal extraction, foamed concrete not only serves as a protective casing but also provides a seepage effect for gas extraction behind the protected section [9]. The development of high-performance drilling protection materials is crucial for improving gas extraction effectiveness.

Foaming agents are key materials for preparing foamed concrete, and their quality directly influences the performance of the foamed concrete. Chemical and physical foaming agents are the two main types of foaming agents. In terms of chemical foaming agents, Zhang Chao [10] selected aluminum powder as an expansion agent, where the aluminum powder reacts with water in an alkaline solution to generate hydrogen gas, achieving an expansion effect. Zhang Chao used calcium oxide as an expansion agent, similarly generating gas through a reaction to form foam. Liu Runqing [11] and Yue Wenping [12] used hydrogen peroxide as a foaming agent, which decomposes under alkaline conditions to produce oxygen, thereby forming the pore structure in the cement after curing. Tian Li [13] chose a mixture of aluminum nitrate and sodium bicarbonate as the foaming agent, with the generated carbon dioxide gas forming small holes in the cement. However, these studies have shown deficiencies in foam stability and uniformity, with foam size being affected by various conditions, making precise control difficult. For physical foaming agents, Li Hou [14] used sodium dodecyl sulfate (SDS) as an anionic surfactant and chose cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, studying the impact of the foaming agent on the performance of fresh and hardened foamed concrete. S S Sahu [15] found that foam produced by compressed air has better quality than foam produced by a mixer. Alassane Compaoré [16] prepared animal protein foaming agents through fermentation to obtain an alkaline hydrolysate-containing protein. Manan Hashim [17] analyzed and compared the effects of protein foaming agents and composite foaming agents on the performance of foamed concrete. Shi Xingbo [18] and Huang Fengqi [19], respectively, used NaOH and Ca(OH)₂ as the alkaline hydrolysis catalyst to hydrolyze discarded pig trotters or cow hair, adding a certain amount of different types of surfactants and foam stabilizers for compounding, after which the foam stability of the compounded liquid was noticeably improved. Bai Yinghua [20,21] et al. used ionic surfactants α-olefin sulfonate sodium (AOS), sodium dodecylbenzenesulfonate (LAS), and sodium dodecyl sulfate (K12) to modify the mother liquor of animal protein foaming agents, preparing composite (triple-blend) modified foaming agents. However, existing studies mostly focus on single-function foaming agents, with uneven foam distribution in the cement slurry and low compressive strength, resulting in poor performance of the formed foamed concrete [22].

Utilizing human hair waste to produce composite protein foaming agents is an innovative method with potential advantages. Human hair waste is rich in protein, and through proper processing and modification, it can significantly enhance the material properties, mechanical behavior, and microstructure of foamed concrete. Studies have shown that adding an appropriate amount of protein foaming agent can increase the compressive strength and durability of foamed concrete while improving the uniformity of its pore structure and distribution. Utilizing human hair waste not only helps reduce production costs but also effectively decreases environmental pollution and achieves efficient resource utilization. Moreover, human hair waste, when used as a foaming agent for foamed concrete, demonstrates good foam stability and uniform distribution, helping to enhance the overall performance of foamed concrete. Therefore, the composite protein foam based on human hair waste has an important application potential and renewable ability in the field of drilling instability and collapse protection, which provides a feasible method for the development of energy-saving, environmentally friendly, sustainable, and cost-effective high-performance drilling casing materials.

In this paper, a high-performance drilling protection material with high strength, high permeability, and controllable setting time is developed. In view of the instability characteristics of cross-layer drilling, the grouting protection mode of cross-layer drilling and the collaborative protection mode of screen pipe protection and the grouting reinforcement of cross-layer drilling are proposed, respectively, which can effectively prevent the occurrence of mine accidents. The foam concrete developed in this paper has significant sustainable development and is expected to achieve positive economic and environmental benefits in engineering practice.

2. Materials Development and Experimental Method

2.1. Selection of Foaming Agents

Common chemical foaming agents currently used in the production of foamed concrete include aluminum powder, sodium bicarbonate, and hydrogen peroxide. These agents have poor bubble stability, and their bubble size can be influenced by various conditions, making precise control difficult. In contrast, physical foaming agents are added to the concrete during mixing in the form of pre-made foam, thereby forming a large number of uniform and stable micro-bubbles in the concrete to create foamed concrete. This method can effectively improve the performance and quality of the foamed concrete.

Physical foaming agents mainly include rosin, protein, synthetic surfactant, and composite protein agents. Composite protein foaming agents are prepared by adding a suitable amount of surfactants and foam stabilizers to protein-based foaming agents, essentially modifying them. Composite protein foaming agents have attracted attention because they not only possess excellent foaming properties but also foam stabilization capabilities. As they are composed of various components, composite protein foaming agents solve the problem of poor foaming performance of single-component agents and can precisely control the injected foam, thereby enhancing the performance and quality of the foamed concrete.

2.2. Preparation of Foaming Agent Mother Liquor

The preparation of foaming agent mother liquor is actually a protein hydrolysis process, where bubbles are formed through protein degradation. When the peptide bonds of large molecule proteins dissociate, smaller hydrophobic molecules form. This method not only reduces the surface tension of the solution but also creates hydrogen bonds between the molecular groups, helping to increase the adsorption strength between the bubbles. Furthermore, in protein-based foaming agents, the protein adsorbed at the interface establishes a viscoelastic layer, thereby generating stable bubbles.

Protein hydrolysis experiments mainly involve experimental raw materials such as protein, calcium hydroxide, sodium hydroxide, dilute hydrochloric acid, hydrogen peroxide, and water. When the hydrolysate of animal protein is used as the mother liquor of the foaming agent, it has good stability. For animal hair, the protein content ranges between 10% and 45%; for animal hooves and horns, the protein content ranges between 15% and 40%. Human hair serves as a protein carrier, with keratin accounting for approximately 65% to 95% of the total mass. As the protein content is high, and it possesses excellent biological characteristics and good mechanical properties, it can theoretically improve foam stability. Moreover, human hair waste is common in daily life and most of it is not effectively treated, representing waste. This experiment, however, enables waste utilization and keeps the experimental cost relatively low.

The process of hydrolyzing human hair waste to extract protein mother liquor for the foaming agent is shown in Figure 1. The preparation process is as follows: (1) wash and dry the hair residue, put the hair and water into the beaker according to the 1:8 weight ratio, pour 30% H₂O₂ and water into the beaker, and then add 30% calcium hydroxide powder (30% sodium hydroxide), mix, and stir; (2) the above two kinds of mixtures were heated in a constant temperature water bath set at 90 °C, during which the hydrolysis time was 60 min, and the hydrolysis rate of sodium hydroxide and calcium hydroxide was compared; (3) cooling and filtering the residue: add dilute hydrochloric acid to neutralize the mixture and adjust the PH value to 7–8; and (4) secondary filtration, drying, and concentration to obtain foaming agent mother liquor.

2.3. Modification and Compounding of Foaming Agents

The function of surfactants is to improve the wetting properties of the foaming agents, making bubble formation easier and enhancing the stability of the bubbles. Foam stabilizers, on the other hand, increase the strength and stability of the bubbles, preventing them from bursting and merging. Common modifiers for protein foaming agents include hydroxyethyl cellulose, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyvinyl alcohol/polyacrylamide (such as polyacrylamide), polyurethane (such as polyethylene glycol polyether), polyamide (such as polyacrylamide), polyether (such as polyethylene glycol), and more. Common foam stabilizers include gelatin, gum arabic, calcium stearate, and others. These surfactants and foam stabilizers can significantly improve the performance of the foaming agents, enhance the stability of the foam, and thereby enhance the performance of the foamed concrete.

In this study, taking into consideration the commonly used drugs at home and abroad and their cost, the selected surfactants are sodium dodecylbenzenesulfonate (LAS), α-olefin sulfonate sodium (AOS), sodium dodecyl sulfate (K12), and sodium laureth sulfate (SLS). The foam stabilizers are gum arabic and calcium stearate [23]. The concentration of the protein mother liquor foaming agent is set at 5 g/L. The four mixed foaming agent water solutions with a concentration of 5 g/L (30 mL each) are poured into four 1000 mL empty beakers, with LAS, AOS, SLS, and K12 added in amounts of 0.8 g, 0.9 g, 1.0 g, 1.5 g, 2.0 g, and 2.5 g for the compounding experiments. The optimal surfactant and its concentration are determined based on foam volume and foam settlement distance. After the surfactant is determined, gum arabic and calcium stearate are added separately to compare the foam stabilizer performance. Then, gum arabic and calcium stearate are added separately again to determine the foam stabilizer based on the comparison of foam stability.

The experimental process of compatibility improvement is as follows:

(1)

The concentration of the protein mother liquor foaming agent was fixed, and the best concentration was determined to be 2.0 g/L.

(2)

Four 30 mL foaming agent aqueous solutions with a mixed concentration of 2.0 g/L were poured into five 1000 mL empty beakers, respectively, and K12, LAS, AOS, and SLS were added successively to make their concentrations 0.8, 0.9, 1.0, 1.5, 2.0, 2.5 and 3.0 g/L, respectively, for the compound experiment.

(3)

The data were recorded, and the optimal surfactant and its concentration were determined according to the foam volume and foam settling distance.

3. Results and Analysis

3.1. Selection of Hydrolysis Drugs

As shown in Figure 2a, 5 g each of NaOH and Ca(OH)₂ are used for the hydrolysis of the protein mother liquor. After adding 50 mL of water and pouring it into a 1000 mL beaker, the selected model is a JJ-1B-type mixer, the set speed is 2000 r/min, and the stirring is 1 min. As shown in Figure 2b, the foaming volume of the foaming agent mother liquor prepared with NaOH as the hydrolysis drug is 600 mL, with a foam magnification of 12 times. The foaming volume of the foaming agent mother liquor prepared with Ca(OH)₂ as the hydrolysis drug is 380 mL, with a foam magnification of 7 times. After the foam is left to stand for 1 h, as shown in Figure 2c, the 1h settlement distance of the foaming agent mother liquor hydrolyzed by NaOH is 13 mm, and that of the foaming agent mother liquor hydrolyzed by Ca(OH)₂ is 22 mm.

According to the national standard GB/T19274-2011 [24] “Foamed Concrete”, the foam magnification and 1 h settlement distance of the foamed concrete foaming agent should meet the following specifications: the foam magnification should be greater than 20 times; and the 1 h settlement distance should be less than 10 mm. Foam magnification refers to the ratio of the volume of gas produced by the foaming agent to the volume of the foaming agent. The foaming volume refers to the volume of the foaming agent water solution when it is left to stand after stirring at 2000 r/min for 1 min with a mixer. Foam settlement distance refers to the distance the foam column settles within 1 h.

During the experiment, the NaOH hydrolysis solution gradually turned light yellow, and the Ca(OH)₂ hydrolysis solution gradually formed a white precipitate during the heating process, producing white foam. The hydrolysis rate of NaOH was significantly higher than that of Ca(OH)₂. Based on the comparison of the foam performance prepared with only the foaming agent mother liquor without adding any surfactants, the performance of the sodium hydroxide hydrolysis solution is significantly better than that of the calcium hydroxide hydrolysis solution. Furthermore, considering the hydrolysis rate, the sodium hydroxide hydrolysis rate is higher than that of calcium hydroxide, and sodium hydroxide was selected for protein hydrolysis after comprehensive consideration. Through experimental measurements, the optimal ratio for foaming is found to be mother liquor/water = 1:4 for the best foaming effect.

3.2. The Selection and Dosage of the Active Agent Is Determined

According to the national standard GB/T19274-2011 “Foamed Concrete”, the foaming effect of the foaming agent mother liquor does not meet the requirements significantly, necessitating compositional improvement. By fixing the concentration of the protein foaming agent, K12, LAS, AOS, and SLS are successively added, making their concentrations 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, and 3.0 g/L, respectively, for the compounding experiment. The experimental results are shown in Figure 3 and

Table 1. Foam volume and 1 h settling distance of protein foaming agent combined with anionic surfactant.

	K12		LAS		AOS		SLS
	Foaming Volume	Subsidence Distance	Foaming Volume	Subsidence Distance	Foaming Volume	Subsidence Distance	Foaming Volume	Subsidence Distance
0.8 g/L	476 mL	7 mm	201 mL	——	582 mL	9 mm	831 mL	32 mm
0.9 g/L	503 mL	7 mm	212 mL	——	596 mL	9 mm	894 mL	37 mm
1.0 g/L	515 mL	9 mm	210 mL	——	600 mL	10 mm	900 mL	40 mm
1.5 g/L	800 mL	15 mm	211 mL	——	710 mL	13 mm	920 mL	51 mm
2.0 g/L	934 mL	36 mm	220 mL	——	947 mL	18 mm	955 mL	55 mm
2.5 g/L	910 mL	31 mm	215 mL	——	930 mL	17 mm	947 mL	55 mm
3.0 g/L	887 mL	29 mm	210 mL	——	820 mL	17 mm	942 mL	53 mm

, where the drug concentration in Figure 3 is 2.0 g/L, and the volume of the foaming agent is 30 mL.

As can be seen from Figure 4 and Figure 5, the foaming volume and 1 h settlement distance of the four composite systems all roughly form an inverted “V” shape with the change in dosage. When the amount of surfactant is less than 2.0 g/L, as the amount of surfactant increases, the surfactant molecules will form a layer of coverage at the liquid–air interface. This reduces the tension at the liquid–air interface, thereby increasing the amount of foam. When the amount of surfactant is 2.0 g/L, the foam amount reaches its peak. This is because, at this point, the surfactant molecules have sufficiently covered the liquid–air interface, making the foam more stable and finer. However, when the amount of surfactant exceeds 2.0 g/L, the excessive surfactant molecules will form multiple layers of coverage at the liquid–air interface. This causes the tension at the liquid–air interface to continue to decrease, which in turn leads to a decrease in foam stability and a reduction in the amount of foam. Therefore, when the amount of surfactant is too high, it will have a negative effect on the foam. In the process of foam generation, the main function of the surfactant is to reduce the surface tension of the liquid, thereby allowing gas to enter the liquid and form foam. However, if too much surfactant is added, the surface tension will be too low, reducing the attraction between liquid molecules, lowering the stability of the foam, shortening the time the foam can exist, and therefore reducing the amount of foam. Additionally, too much surfactant will cause an uneven distribution of air in the foam, forming large bubbles rather than small ones, which will also lead to a reduction in the amount of foam.

The experiment showed that when LAS was added for compounding, there was no significant foam-increasing phenomenon in the foaming volume, and the 1 h settlement distance could not be measured, so this drug was excluded. K12, AOS, and SLS have a very significant foaming effect on the protein mother liquor. Based on the foam volume, the foaming performance is ranked as SLS > AOS > K12, with SLS having the best foaming performance. Considering the 1 h settlement distance, i.e., the foam stability factor, the foam stabilization performance is ranked as AOS > K12 > SLS, with AOS having the best foam stabilization performance. Finally, AOS and SLS were selected for further combination with foam stabilizers for the compositional improvement experiment of protein foaming agents, where the best dosage for AOS was 2.0 g/L, and that for SLS was 2.0 g/L.

3.3. Selection and Determination of Dosage of Foaming Stabilizers

After the compounding of the protein foaming agent mother liquor and active agent had been completed, the foaming performance had significantly improved, but the foam was unstable. To further enhance foam stability, a foaming stabilizer was added to the compound system. The selected foaming stabilizers were gum arabic and calcium stearate, set at 0.1 g/L, as shown in Figure 6, Figure 7 and Figure 8.

As shown in Figure 6b, the addition of gum arabic as a foaming stabilizer severely affected the foaming ability, and the foam stabilization did not significantly improve. Gum arabic is a thickening agent, which made the mother liquor viscous after addition, improving the quality of the foam film, increasing the viscoelasticity of the film, reducing the foam’s permeability, and stabilizing the foam. If the added amount was small, it could not play the role of thickening. However, as the addition continued to increase, the viscosity continued to increase, the work to overcome the viscous resistance during foaming also increased, and the foam decreased. Moreover, with the increase in the added amount, the proportion of liquid in the liquid film also increased, and the action of gravity caused the foam to burst and dehydrate, thereby reducing stability.

This can be seen from

Table 2. Comparison of foam volume and 1 h settling distance after adding foam stabilizer.

	AOS		SLS
	Add Calcium Stearate	Calcium Stearate Is Not Added	Add Calcium Stearate	Calcium Stearate Is Not Added
Foaming volume	830 mL	920 mL	950 mL	930 mL
1 h Subsidence distance	7 mm	19 mm	9 mm	17 mm

, calcium stearate is a type of anionic surfactant. This study used anionic surfactants to compound the mother liquor, so the effect of using calcium stearate was better. It could reduce the surface tension of bubbles, thereby reducing the number of bubbles that burst due to surface tension. Also, calcium stearate has a hydrophobic effect and can play a waterproof role.

Zhao Chunxin [25] found through experiments that the foaming effect was significant when the amount of foaming stabilizer was between 0.3% and 0.65%, and the compressive strength was the highest when the addition amount was about 0.35%. In this study, the best result was obtained when the addition amount was 0.3%. After adding 0.3% calcium stearate, the foaming volume of AOS was significantly reduced, but the stability was enhanced, and the 1 h settlement distance significantly decreased. After adding 0.3% calcium stearate to SLS, it did not affect the foaming volume but did enhance the foam stability, conforming to the national standard GB/T19274-2011 “Foamed Concrete”. Therefore, the foaming agent experiment adopted 2.0 g/L SLS for compositional improvement and 0.3% calcium stearate as a foam stabilizer.

3.4. Study on Performance of Foamed Concrete Based on Human Hair Slag Composite Foaming Agent

A mixture was created by evenly mixing 100 g of ordinary Portland cement, 70 mL of water, 40 g of coal dust, 5 g of silica fume, and 0.2 g of polypropylene. After the slurry was prepared, 20 mL, 25 mL, and 30 mL of well-mixed foaming agent foam were, respectively, added to the prepared slurry, named A, B, and C. The compressive strength, permeability, and porosity were measured.

Determination method of compressive strength: For the uniaxial compression test, as shown in Figure 9a, the sample is placed on the RMT-150B rock mechanics testing system, and the loading speed and mode of the testing machine are set to start the uniaxial compression test. During the experiment, the compressive deformation and force of the sample are recorded. After the experiment, the uniaxial compressive strength of the sample is calculated based on the experimental data.

Determination method of porosity: For the saturation method for porosity determination, as shown in Figure 9b, the cement column is placed in distilled water for vacuum saturation treatment. First, the porosity of the standard sample is measured to establish a calibration relationship. Then, the porosity of the cement column is measured in the saturated state. Next, centrifugal force is applied to the cement column for 1 h. After removing the specimen, the porosity is measured again under centrifugal conditions to determine the final porosity.

Determination method of permeability: For the Darcy’s law method for permeability determination, as shown in Figure 9c, the flow pump is opened to allow water to flow into the device. The sample is subjected to confining pressure and axial pressure. When the pressure gauge shows that the axial pressure and confining pressure are both 7 MPa, the pressure application is stopped. After waiting for a period of time to allow gas to be discharged, when the reading of the flowmeter remains unchanged, the data are recorded as the flow rate of the sample under the given pressure. Finally, Darcy’s law is used to convert the obtained flow rate value into permeability.

From Figure 10 and Figure 11, the conclusions below can be drawn.

(1)

In terms of porosity, the higher the foam content, the smaller the pore size of the foamed concrete because the increase in foam content can generate more and smaller bubbles. These small bubbles can fill the gaps between cement and sand particles, thereby restricting the formation of larger bubbles and making the overall pore size distribution more uniform. As the foam content increased, the foamed concrete formed more pore structures, leading to an increase in porosity.

(2)

In terms of permeability, the permeability first increased and then decreased as the amount of foam increased. Among them, specimen A had the lowest permeability, and specimen B had the highest permeability. Adding foam caused the porosity of the concrete to increase, making it easier for gases to penetrate into the concrete. Simultaneously, as the foam content in specimen A was the smallest, its porosity was correspondingly smaller, leading to lower permeability. Specimen B had a moderate amount of foam, correspondingly larger porosity, and more formed interconnected pores, leading to higher permeability. Although the porosity of the C specimen is increased, it is basically small pores and poor connectivity, as shown in Figure 12. When the right amount of foam enters the concrete, some of it bursts, forming a network of interconnected pores. This connected porosity can promote the penetration of moisture and improve the permeability of concrete. However, the dispersion of excess foam in the concrete slows down, and the pores formed at the same time are no longer connected to each other, causing the pores in the concrete to become more isolated and disconnected, which means that the pores in the concrete cannot form a continuous channel, hindering the penetration of moisture and other substances. In this case, the permeability of the concrete will be reduced.

(3)

In terms of compressive strength, the larger the amount of foam, the lower the compressive strength of the foamed concrete. Among them, specimen A had the highest compressive strength, and specimen C had the lowest. Adding too much foaming agent foam reduced the density of the concrete, leading to a decrease in compressive strength. Since specimen A had the smallest amount of foam, its porosity was correspondingly smaller, leading to higher compressive strength. In contrast, specimen C, which had the largest amount of foam, had the largest porosity, leading to lower compressive strength. Hence, a negative correlation exists between porosity and compressive strength.

(4)

According to

Table 3. Comparison of specimen properties in this study with other specimens.

Researcher	Sample	Preparation Method	Foaming Agent	Compressive Strength (MPa)	Permeability (MD)	Porosity (%)
Yue Wenping	——	Chemical Foaming	H2O2	14	——	——
Guo Yisong	——	Chemical Foaming	Plant Protein	1.52	——	——
Gao Zhihan	——	Physical Foaming	——	16	——	——
This Study	Sample A	——	——	>11	——	——
This Study	Sample B	——	25 mL Compound Foaming Agent	13.665	2.48	18.141
This Study	Sample C	——	——	>11	——	——
Low-Rank Coal	——	——	——	——	10−3~10−5 MD	——
High-Rank Coal	——	——	——	——	10−7~10−9 MD	——

, Yue Wenping et al. [12] found that the compressive strength of foamed concrete prepared with hydrogen peroxide as a chemical foaming agent was generally 14 MPa. Guo Yisong [26] found that the compressive strength of foamed concrete prepared using plant protein as a foaming agent was 1.52 MPa. Gao Zhihan et al. [27] found that the compressive strength of four different density foamed concretes prepared using physical foaming methods was 16 MPa. The compressive strength of the A, B, and C specimens prepared in this study all exceeded 11 MPa, demonstrating excellent support effects. For low-rank coals, the permeability generally ranged from 10⁻³ to 10⁻⁵ MD, while the permeability of high-rank coals ranged from 10⁻⁷ to 10⁻⁹ MD. The permeability of specimens A, B, and C far exceeded that of coal permeability. An experimental analysis showed that when the amount of foaming agent added was 25 mL, specimen B had the best performance with a compressive strength of 13.665 MPa, a permeability of 2.48 MD, and a porosity of 18.141%. The cross-sectional image of specimen B is shown in Figure 13. The foam size is relatively uniform, the overall shape is spherical, the compressive strength is high, and the pores are well connected with good permeability, demonstrating that it is a new type of high-performance drilling protection material.

4. Conclusions

(1)

Human hair waste has not been effectively treated and utilized. As a composite protein foaming agent mother liquor material, human hair waste can be used as a low-cost and environmentally friendly raw material through waste utilization. Comparing the hydrolysis effects of sodium hydroxide and calcium hydroxide, the foaming volume of the foaming agent prepared with sodium hydroxide as the hydrolysis agent was 600 mL, with a foaming ratio of 12, and a 1 h settling distance of 13 mm. The performance of the sodium hydroxide hydrolysis solution was significantly better than that of calcium hydroxide. Therefore, sodium hydroxide was selected as the hydrolysis agent for the protein.

(2)

Through the experiment of compounding and improvement, it was found that the foaming capacity was ranked as SLS > AOS > K12 > LAS, and the stabilizing capacity was ranked as AOS > K12 > SLS > LAS. SLS showed the best foaming performance, and AOS showed the best stabilizing performance. LAS did not show significant modification effects. The variations in foaming volume and 1 h settling distance in the four compounding systems followed a roughly inverted “V” shape. The foam volume reached its peak when the surfactant dosage was 2.0 g/L. Comparing the stabilizing agents arabic gum and calcium stearate, calcium stearate as an anionic stabilizing agent showed better results when compounded with anionic surfactants. The optimal compounding scheme for foam performance was determined as 2 g/L sodium lauryl ether sulfate (SLS) + 0.3% calcium stearate.

(3)

The foam content showed a negative correlation with compressive strength and a positive correlation with porosity. As the foam content increased, the porosity of the foamed concrete increased, leading to a decrease in compressive strength. The permeability initially increased and then decreased with increasing foam content. A higher foam content generally resulted in a higher porosity and better permeability of the foamed concrete. However, as the foam content continued to increase, the formed pores in the concrete became predominantly closed small pores with poor connectivity. Therefore, when the foam content was 25 mL, the permeability of the foamed concrete reached 2.48 MD, with optimal internal pore connectivity, a compressive strength of 13.665 MPa, and a porosity of 18.141%. This indicates that it is a new type of drilling protection material with high compressive strength, high permeability, and environmental friendliness.

The high-performance extraction borehole protection material prepared in this paper has certain reference significance in the field of coal mine filling. In the future, the following two points can be combined for further research:

(1)

The steps of preparing compound protein blowing agents are too complicated, and the site is not easy to construct, which needs to be further optimized. In the future, it can be considered to optimize the process flow of hydrolyzed protein, reduce cumbersome operations and steps, and achieve a more efficient and simplified hydrolyzed human hair process by controlling reaction conditions. As for the compound foaming agent, the price of the improved compound drugs and foam stabilizers is high, which leads to high production costs. In the formulation design of compound foaming agents, alternative drugs and foam stabilizers can be sought to reduce costs and maintain performance.

(2)

Currently, commonly used grouting materials mainly include concrete, polymer materials, etc. Future research can explore new materials, such as high-strength fiber materials, composite materials, etc., to improve strength and durability. Future research can explore a more efficient and accurate grouting process, including the optimization of injection pressure and speed control, in order to improve the grouting effect and construction efficiency. Combined with intelligent technology, such as sensors and data acquisition and analysis, real-time monitoring and an evaluation of the screen and grouting collaborative protection system is carried out to achieve dynamic monitoring and early warning of borehole stability and improve the safety of the protection system.