Next Article in Journal
The Influence of CO2 Curing on the Properties of Coal Gangue Non-Fired Blocks
Previous Article in Journal
Scenarios of Progressive Pancake/Bending Collapse Considering Elastic/Plastic Reinforced Concrete Buildings
Previous Article in Special Issue
Design Approach on Bearing Capacity of the Cross-Bracing with Different Types of Joint Connection in Steel Lattice Transmission Towers
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Buildings
Volume 14
Issue 7
10.3390/buildings14071949
buildings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Experimental Study and Analysis of the Effects of Mud on the Compressive Strength of Unburned Brick Using Engineering Residue Soil

by
Xingzhong Nong
1,
Linren Zhou
2,*,
Yuehua Liang
1 and
Taojun Wang
2
1
Guangzhou Metro Design & Research Institute Co., Ltd., Guangzhou 510010, China
2
School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(7), 1949; https://doi.org/10.3390/buildings14071949
Submission received: 29 May 2024 / Revised: 20 June 2024 / Accepted: 22 June 2024 / Published: 27 June 2024
(This article belongs to the Special Issue Low-Carbon and Green Materials in Construction—2nd Edition)
Browse Figures
Versions Notes

Abstract

:
Engineering residue soil, a prominent type of construction solid waste, can offer considerable environmental and socioeconomic benefits if efficiently utilized. Unburned brick represents an environmentally friendly and high-value approach to reusing this residue soil. Mud, a primary constituent of residue soil, typically hinders the performance of unburned brick using cement-based materials. This study investigates the effects of mud on the performance of unburned brick made from engineering residue soil based on experimental tests and mechanism analysis. The residue soil is silty clay sourced from the alluvial soil layer in South China. A comprehensive analysis of the physical and chemical properties of the residue soil and mud is conducted to assess the feasibility of using them in unburned brick production. Using ordinary Portland cement as the cementitious material, the unburned residue soil bricks are produced via semi-dry static-press forming and natural curing. The influence of mud type and content on the compressive strength of the unburned brick made with engineering residue soil is investigated and discussed. This experimental study reveals that the influence of mud on unburned brick’s compressive strength is negligible. However, excessively low mud content reduces brick compactness, impairs brick formation, and leads to lower compressive strength. Within the range of solidification, unburned brick’s compressive strength initially increases and then decreases with increasing mud content, with an optimal mud content of approximately 25%. As engineering residue soil often contains a high mud content, reducing it effectively enhances the compressive strength of unburned bricks. Through experiments and mechanism analysis, this research clarifies the impact of mud on the strength and performance of unburned residue soil bricks, providing important theoretical insights and practical guidance for the production of unburned products and promoting the efficient and environmentally friendly resource utilization of engineering residue soil.

1. Introduction

Construction solid waste refers to the waste generated by urban construction, infrastructure development, land expansion, and industrial production. With rapid economic growth and urbanization over the past decades, the accumulated production of construction solid waste in China exceeded 3 billion tons by the end of 2020, with residue soil accounting for 30% to 40% of the total [1]. Engineering residue soil is the discarded soil from the excavation of foundations for various buildings, structures, and pipeline networks. The disposal of such extensive engineering waste presents a range of societal, environmental, and economic challenges. Presently, the primary methods for handling engineering residue soil are landfill-based approaches, including engineering backfill, low-lying landfill, and mine backfill [2]. These landfill methods offer advantages such as simplicity, directness, rapid processing, strong absorption capabilities, and cost-effectiveness; however, they are accompanied by numerous issues, such as resource waste, occupation of land area, environmental pollution, geological disasters, etc.
The resource utilization of construction waste is of considerable importance for the advancement of society and the economy [3]. The research and application of engineering waste resource utilization technology have received substantial encouragement and support. By employing suitable treatment methods and preparation processes, engineering residue soil can be transformed into reusable materials and building products. At present, methods for the resource utilization of construction residue soil include site backfill, subgrade filler, sintered ceramics [4], sintered bricks [5,6], and unburned bricks. Although a significant amount of residue soil is generated at construction sites, the quantity that can be effectively utilized for backfill and subgrade fill is very limited. Sintered bricks and sintered ceramics have the disadvantages of high energy consumption and substantial carbon emissions [7,8]. Fired clay bricks have been banned in many places in China. By contrast, unburned bricks offer a promising solution for solidifying residue soil using inorganic cementing materials. Unburned brick is one of the most potentially beneficial residue soil resource utilization methods, characterized by low energy consumption, low carbon emission, and low cost. Furthermore, the residue soil utilization rate of unburned brick is extremely high.
Currently, research on unburned bricks primarily revolves around the types of solid waste, cementitious materials, and manufacturing techniques utilized. Hsu et al. [9] employed sediments from reservoirs and ports as raw materials, using a pressing and forming method to create unburned bricks. Naganathan et al. [10] used bottom ash and dust from thermal power plants for their unburned bricks. These bricks had a compressive strength ranging from 5 to 10 MPa and a water absorption rate of 7% to 14%. Saeed Ahmari et al. [11] explored the feasibility of using copper tailings as raw materials to produce eco-friendly unburned bricks through geopolymerization technology. Seco et al. [12] used marl clay and silica sand as primary raw materials, employing cement, lime, slag, and magnesium oxide as cementing materials to create unburned bricks. Seco et al. [13] also used building solid waste, including waste concrete and ceramics, in combination with clay as the primary raw materials. They varied the types of cementing materials to manufacture unburned bricks and thoroughly examined the influence of these different cementing materials on the bricks’ properties. In another study, S. Spuelas et al. [14] used clay as the primary raw material and magnesium oxide as the cementing material. Their results highlighted how magnesium oxide enhanced the durability and mechanical properties of the bricks. Ye Chang et al. [15] investigated the effects of cement quantity and water–cement ratio on the compressive strength of unburned bricks made from construction excavation clay. Yao et al. [16] studied how the inclusion of various materials, such as cement and plant straw, affects the performance of unburned engineering residue soil bricks. Guo et al. [17] explored the impact of the ratio between cementing materials and residue soil on the performance of unburned engineering residue soil bricks and analyzed the underlying principles of unburned brick curing. Guo et al. [18] manufactured unburned engineering residue soil bricks by employing inorganic additives through a process involving pressing, forming, and steam curing, comparing and analyzing the effects of inorganic additives on unburned brick strength using compressive strength as the benchmark. Chen [19] studied the influence of forming pressure, moisture content, and the quantity of cementing material derived from engineering waste soil on the properties of unburned bricks. Overall, bricks produced from residue soil can meet requirements for load-bearing capacity, safety, and durability. Especially in terms of compressive strength, their quality and overall performance are comparable to traditional sintered bricks.
Unburned bricks made from residue soil have clear advantages, including good economic benefits, high utilization rates of residue soil, and low energy consumption and carbon emissions [20]. However, many factors substantially influence the performance of unburned bricks, and the raw material of residue soil is one of them [21,22]. The main components of engineering residue soil are sand, stone, and mud. The type and content of mud have a considerable impact on the physical and chemical properties of engineering residue soil. When engineering residue soil is utilized as a raw material for producing unburned bricks, the mud content within the engineering residue soil plays a crucial role in determining the performance of the unburned bricks. However, research in this specific area has been lacking.
This study investigates the influence of mud on the strength performance of unburned bricks made from engineering residue soil. The content and organization of this paper is shown in Figure 1. The research approach involves several key steps. Firstly, the physical and chemical properties of both residue soil and mud are rigorously tested and comprehensively analyzed. Secondly, the manufacturing process and techniques for producing unburned bricks from engineering residue soil are provided and discussed. Thirdly, ordinary cement is utilized as the cementing material and, through a single-factor experimental approach, the impact of different types of mud and varying mud contents on the compressive strength of unburned engineering residue soil bricks is thoroughly investigated. Based on the findings of these experiments, the governing rules and mechanisms behind the influence of mud on the strength properties of unburned bricks are analyzed and discussed. To mitigate the adverse effects of mud on unburned brick performance, three methods for controlling mud content are proposed, offering practical solutions for implementation in engineering projects. This study provides essential theoretical insights and practical guidance for the real-world application and large-scale production of unburned bricks using engineering residue soil.
This paper is organized as follows. The materials and their properties for unburned residue soil brick are provided in Section 2. Then, the production technique of unburned brick and the testing method for compressive strength are elaborated in Section 3. The influences of mud type and mud content on the compressive strength of unburned brick are experimentally studied and discussed in Section 4 and Section 5, respectively. The conclusions are drawn in the last section.

2. Materials

2.1. Raw Engineering Residue Soil

Unburned brick made from engineering residue soil is a type of construction material. It involves solidifying the residue soil using suitable cementing materials to produce building products that meet the requirements for strength and other performance criteria. The essential materials for the production of unburned residue soil bricks primarily include residue soil, cementing materials, and water. The materials for unburned bricks in this study are illustrated and discussed below.
In this study, three different types of engineering residue soil from South China were utilized. To facilitate clarity in the subsequent discussion, these engineering residue soils are identified as Residue Soil-A, Residue Soil-B, and Residue Soil-C. Residue Soil-A was obtained from the foundation pit soil of a major transportation project in Shenzhen City and is characterized as silty clay alluvial soil. Residue Soil-B consists of sandy clay with a residual layer and was collected from the foundation pit of a residential project in Zengcheng City, Guangzhou. Residue Soil-C, another silty clay with a residual layer, was sourced from the foundation pit of a building project in Zengcheng City, Guangzhou. Figure 2 shows the excavated and stacked samples of the three types of engineering residue soil at the construction site, highlighting the distinct color variations among the three types of soil.
The chemical and mineral compositions of these three engineering residue soils were tested and analyzed using X-ray fluorescence (XRF). The chemical compositions of these residue soils are presented in Table 1. Predominantly, all three engineering residue soils are characterized by SiO2 and Al2O3, accounting for more than 85% of the total mass of the soil samples. The loss on ignition (LOI) for Residue Soil-A and Residue Soil-B is approximately 5%, while Residue Soil-C exhibits a slightly higher LOI, just exceeding 10%. LOI can be affected by multiple aspects, including evaporation of absorbed water, removal of organic matter, decomposition of carbonate minerals, removal of bound water associated with interlayer cations of clay minerals, and dehydroxylation of clay minerals [23]. In general, the LOI levels are relatively low, suggesting that their material composition remains stable, making them suitable for the production of unburned bricks.
Mineral composition is a crucial material parameter indicator for engineering residue soil. Figure 3 presents the results of X-ray diffraction (XRD) analysis, highlighting the mineral compositions of the three engineering residue soil samples. For Residue Soil-A, the predominant mineral is quartz, accounting for 53.8% of the composition. In contrast, Residue Soil-B and Residue Soil-C are mainly composed of kaolin, constituting 61.5% and 66.1% of their respective mineral compositions.
In the residue soil, particles with a size smaller than 0.075 mm are classified as mud. To determine the mud content and sand particle size distribution of these three engineering residue soils, a combination of screening and washing methods was employed in accordance with the standard testing method of GBT14684-2022 Sand for construction [24]. The results are listed in Table 2. Residue Soil-A and Residue Soil-B exhibit relatively low mud content, around 30%, while Residue Soil-C has a higher mud content exceeding 50%. According to GBT14684-2022, Residue Soil-A and Residue Soil-B fall within Zone 2 for particle size distribution, while Residue Soil-C corresponds to Zone 3. Additionally, Residue Soil-B has fine particle sizes with coarser sand, Residue Soil-A is intermediate, and Residue Soil-C has the finest sand particles.

2.2. Types and Physicochemical Characteristics of Mud

(1)
Definition and composition of mud in residue soil
In general, according to particle size, the material composition of engineering residue can be divided into impurities and stones (particle size > 40 mm), gravel (particle size 5–40 mm), sand (particle size 0.075–5 mm), and mud (particle size < 0.0075 mm). In this study of residue soil, particles with a size smaller than 0.075 mm are classified as mud.
Minerals within residue soil can be categorized into primary minerals and secondary minerals. Primary minerals include quartz, feldspar (microcline), and mica, among others. Secondary minerals, often referred to as clay minerals, encompass 1:1 kaolin, 2:1 montmorillonite, 2:1 illite, and tridiaspore (Al2O3·H2O). Secondary minerals are the main components of mud. Mud, which lacks material reactivity, has an adverse effect on concrete. On the one hand, the existence of mud will hinder the bond between the cement hydration products and aggregate, which readily forms a weak area, resulting in a decline in the strength and elastic modulus of the concrete. On the other hand, due to the extremely small particle size and large specific surface area, the mud will absorb a large amount of free water, and after the free water evaporates, the volume will be greatly reduced, resulting in serious weak areas in the areas where the mud exists. As a result, the volume stability of the concrete decreases and the permeability resistance and chloride ion permeability become worse.
Similarly, mud is one of the primary factors influencing the properties of unburned bricks made from engineering residue soil. The mud content in residue soil is relatively high, and the chemical and mineral composition of the mud is notably complex. This complexity varies considerably among different residue soil types. To date, there has been a noticeable absence of research reports regarding the impact of the physical and chemical properties of mud on the performance of unburned bricks. This experimental study aims to investigate the influence of different mud types on the compressive strength of unburned bricks produced from residue soil.
(2)
Mud material for experiment of unburned brick
The primary engineering residue soil, following initial treatment, is subjected to drying and light grinding using an edge runner mill. Particles smaller than 0.075 mm are considered mud, sorted by utilizing a vibrating sieve screen. This process is applied to the three types of residue soil, resulting in the production of three distinct mud types, denoted as Mud-A, Mud-B, and Mud-C. Figure 4 illustrates the colors of these three mud types, demonstrating a noticeable difference. Mud from Residue Soil-B exhibits a whitish color, mud from Residue Soil-C has a reddish–brown color, and mud from Residue Soil-A falls in between, displaying a light reddish–brown color.
The XRF method is utilized to analyze the chemical composition of the three types of mud, and the results are presented in Table 3. The chemical compositions of the mud obtained from Residue Soil-A, B, and C exhibit considerable similarities. The primary oxides found in all three cases are SiO2 and Al2O3, with SiO2 being the predominant component, followed by Al2O3. The combined mass of these two oxides accounts for more than 80% of the total mass. Other oxide components have relatively small mass proportions, and their ordering differs slightly among the three types. Furthermore, the ignition loss for all three mud types is low, with the highest recorded at only 7.42%. This indicates a minimal presence of organic matter and ensures a stable chemical composition.
The mineral compositions of the three types of residue soil mud are analyzed using the XRD method, and the results are shown in Figure 5. These analyses reveal substantial disparities in the mineral compositions of the three types of mud. Each type of residue soil contains quartz, kaolin, and illite, but with varying proportions. Mud-A has more balanced mineral compositions of kaoline, quartz, and microcline, with proportions of 38.9%, 35%, and 21.8%, respectively. Kaolin is the primarily mineral of Mud-B and Mud-C, with a proportion of 77.8% and 75.25%, respectively. The proportion of quartz in Residue Soil-A and Residue Soil-C is 35% and 16.7%, respectively. However, in Residue Soil-B, the quartz content is considerably lower, accounting for only 5.3%. Furthermore, Residue Soil-A and Residue Soil-B contain microcline, which is absent in Residue Soil-C, constituting 21.8% and 6.5% of their respective compositions. This analysis demonstrates that mud minerals within residue soil are typically diverse and complex, rarely existing in isolation in nature. Moreover, the proportions of mud minerals vary between different types of residue soil.

2.3. Recycled Sands of the Residue Soils

The portion of a residue soil’s particles with a particle size ranging from 0.075 mm to 4.75 mm is referred to as the recycled sand component of the residue soil. The cumulative screening results for the recycled sand portion of the three engineering residue soils are presented in Table 4. Analysis reveals that the recycled sand from Residue Soil-A and Residue Soil-B falls into the category of medium sand within Zone-2, with fineness moduli of MxA = 2.4 and MxB = 2.9, respectively. In contrast, the recycled sand from Residue Soil-C is categorized as fine sand within Zone-3, with a fineness modulus of MxC = 1.8. Following preliminary investigation and analysis, it is evident that these three types of engineering residue soil are representative of South China and are well-suited for experimental studies related to the production of unburned bricks. The findings of this study can provide practical and guiding significance for the large-scale production of unburned bricks based on residue soil.

2.4. Cementitious Material and Water

To facilitate engineering applications and reduce the complexity and cost of unburned residue soil bricks, this study utilizes ordinary Portland cement, designated as P∙O 42.5, as the cementing material and ordinary tap water for the preparation of unburned bricks based on residue soil.

3. Production and Strength Test of Unburned Brick Specimens

The preparation process of unburned bricks using engineering residue soil mainly involves raw material treatment, unburned brick production, and unburned brick curing.

3.1. Processing of Raw Material for Residue Soil

The engineering residue soil retrieved from construction sites is processed to obtain suitable materials for preparing unburned bricks. The engineering residue soil treatment process is illustrated in Figure 6. Initially, the original residue soil is passed through a 10 mm sieve to remove larger stones and other impurities. Subsequently, the residue soil with particle sizes finer than 10 mm is spread out on the ground and left to naturally air dry until the soil becomes loose and does not stick together when pinched by hand. This step enhances subsequent soil drying efficiency. The naturally air-dried soil is then transported to a drying machine and dried until it reaches a constant weight. Finally, the dried soil is screened again using a 5 mm sieve and the soil with particle sizes less than 5 mm constitutes the raw material required for preparing unburned bricks. Residual sand and gravel particles with particle sizes larger than 5 mm but less than 10 mm can be retained. They can serve as coarse sand and stone particles to reduce the soil content of unburned bricks and can also be used as recycled aggregates. Generally, the mass proportion of sand and stone particles within the 5 to 10 mm range is minimal, accounting for approximately 1% to 5% of the soil’s mass.
To quantitatively analyze the specific impact of mud content in engineering residue soil on the compressive strength of unburned bricks, it is essential to minimize the influence of other factors. Among these factors, controlling the characteristics of sand in the residue soil, including its composition, particle size, and grading, poses a considerable challenge. Preliminary investigations revealed that the coarseness and grading of the sand had a noticeable effect on the compressive strength of unburned bricks. To maintain the physical and chemical properties of the sand used in this experiment, all medium sand from Residue Soil A is blended according to a predefined fine grading for unburned brick production.
The process flow is outlined in Figure 7. Initially, the mud content in the recycled sand is removed through a water-washing process, yielding recycled sand material. Subsequently, the recycled sand material is dried, followed by screening using a vibrating screen machine to obtain recycled sand with varying particle size ranges. Finally, by employing the designed sand grading, sand with different particle sizes is weighed and mixed to obtain the necessary sand material for the preparation of unburned bricks. It is worth noting the following: (1) The washing of residual soil is a key factor for controlling mud content in this study. In actual production, if sand grading adjustments are needed, a dry screening method can be utilized to obtain recycled sand. (2) The sand gradation for all specimens is keep in a certain gradation zone, aimed at minimizing the effects of recycled sand on unburned brick strength. The sand gradation Zone 1 is utilized in this experiment study and the sand grading curve is shown in Figure 8.

3.2. Production of Unburned Brick

The production method for unburned engineering residue soil bricks proposed in this study is illustrated in Figure 9. The key steps are as follows: (1) Weigh all materials required for unburned bricks according to the specified mix ratio. Pre-mix the dry sand and clay. The moisture content of the bricks is maintained at 13%. (2) Thoroughly wet the mixing pot with water, then pour water into the mixing pot. Next, add the cementing material and cement and stir for 1 min to obtain a clean slurry. While stirring, slowly add the residue soil material and continue stirring for 2 min to achieve a uniform mixture of the slurry and residue soil, thus completing the raw material blending. (3) Load the thoroughly mixed unburned brick mixture into the pre-assembled steel mold. Use a hydraulic-controlled jack to apply pressure to the active surface of the mold. Maintain the load for 30 s after reaching 10 MPa of pressure, and then release the pressure. (4) Remove the mold to obtain the press-formed unburned brick. The pressed brick, having good compactness and initial strength, can retain its shape intact after demolding.

3.3. Curing Method of Unburned Brick

The pressed bricks are transferred to a simple curing chamber for natural curing. As illustrated in Figure 10, the curing chamber is a simple wooden cabinet covered with plastic film to maintain a moisture and humidity level no less than 80% within the enclosure, and a temperature higher than 10 °C. The natural curing method for unburned bricks involves a three-day period of surface wetting through watering after the specimens are placed inside the curing chamber. Subsequently, the curing chamber is sealed, allowing the unburned bricks to naturally cure for 14 or 28 days. Once the specified curing duration is achieved, the unburned residue soil bricks are ready for strength testing.

3.4. Test Method of Compressive Strength

According to the requirements outlined in the national standard GB/T 2542-2012 Test Method for Wall Bricks [25], compression tests were conducted on 70 mm cube specimens. These tests were performed in the national key laboratory at the South China University of Technology using a 200 kN electronic universal testing machine. Before testing, the length and width dimensions of each specimen’s compression surface were measured at two points, with an accuracy of 1 mm, and the average value was used for strength calculations. During the testing process, the load was applied to the relatively flat surface of the cube specimen.
The compressive strength testing of the unburned bricks is shown in Figure 11. The cube specimen was positioned centrally on the loading plate, and the load was applied evenly and smoothly, perpendicular to the compression surface. To ensure the precision and stability of the test data, any impact or vibration during loading was avoided. The force control method was employed for loading, with the specimens continuously loaded at a rate of 5 kN/s until they were damaged and no longer able to carry the load. The maximum failure load, denoted as P, was recorded for each specimen. The compressive strength of the unburned engineering residue soil brick specimens is calculated using Equation (1):
R P = P L × B
where Rp is the compressive strength of the specimen (MPa), P is the maximum failure load of the specimen (N), and L and B are the length and width of the compression or connection surface of the specimen (mm).

4. Influence of Mud Type on the Strength of Unburned Brick

4.1. Experimental Design and Implementation

The research design encompasses three sets of experiments, each focusing on the effect of distinct mud types on the compressive strength of these unburned bricks. Given the scarcity of singular secondary clay minerals in engineering residue soil, it is of limited value to explore the impact of single secondary clay minerals on brick strength. Therefore, this study utilizes mud directly screened from the engineering residue soil, aligning with real-world engineering scenarios.
The three mud types are specifically extracted from Residue Soil-A, Residue Soil-B, and Residue Soil-C. In these experiments, variations in mud type constitute the sole point of distinction, while all other parameters remain consistent. The particle gradation of recycled sand within the residue soil is shown in Figure 9. Each specimen, incorporating mud from Residue Soil-A, B, or C, weighs 0.86 kg, with 13% being water (0.112 kg) and 87% being solid (0.748 kg). The mass of the engineering residue soil comprises 90% of the solid mass. This engineering residue soil for unburned brick comprises recycled sand and mud, with the fixed mud content in this experiment being 25%. As a result, the masses of recycled sand and mud constitute 75% and 25% of the residue soil mass, corresponding to 0.505 kg and 0.168 kg for each specimen, respectively. The cementitious material, cement, accounts for 10% of the solid mass, equal to 0.075 kg per specimen. For each type of mud blended with Residue Soil-A, B, and C, six specimens are manufactured. The specimens are formed using a 10 MPa semi-dry static pressing method, and the curing process involves natural curing for 14 and 28 days.
As shown in Figure 12, the unburned brick specimens produced from engineering residue soil using three distinct types of mud exhibit noticeable variations in color. Comparing the brick color to that of the mud (Figure 4), it is evident that the color of the brick is primarily influenced by the color of the mud. Additionally, the surface of the unburned engineered residue soil brick appears flat, with regular dimensions, distinct water horns, and high molding quality.

4.2. Experimental Results and Discussion

Natural curing was carried out on unburned brick specimens of different mud types, and the compressive strength was tested at curing ages of 14 and 28 days, as shown in Figure 13. Among the 14-day compressive strength results for bricks made using the three different mud types, the highest strength was observed in bricks produced with Mud-C, measuring 14.49 MPa, while the lowest strength was recorded in bricks made with Mud-B, registering 13.11 MPa. The absolute difference between the two strengths was 1.38 MPa, with a relative difference of 10.5%. For the 28-day compressive strength tests, bricks mixed with Mud-B exhibited the highest strength at 21.9 MPa, while those mixed with Mud-A had the lowest strength at 20 MPa, resulting in a relative difference of 9.8%. Generally, the complex and uncertain nature of the basic material composition of bricks leads to low strength and considerable variability. Consequently, brick specifications allow for a higher acceptable error value in compressive strength, typically within 20%. Considering this criterion, the difference in compressive strength among bricks mixed with different mud types at 14 and 28 days is approximately 10%. It can be concluded that the variation in compressive strength among unburned bricks prepared with three different mud types is not remarkable, indicating that the mud type has a relatively minor influence on the strength performance of these bricks made from engineering residue soil.
A small proportion of different types of single secondary clay minerals present in aggregates can result in varying degrees of deterioration in the development of concrete compressive strength [26,27]. Most studies have indicated that the influence of montmorillonite on strength is more pronounced than that of kaolin and illite [26,27,28,29]. It can be concluded that the difference in the mineral composition of sifted mud in different residue soils can considerably impact the compressive strength of unburned bricks made from residue soil. However, the surface mud type identified above has a limited impact on the strength of unburned bricks made from residue soil. This may be attributed to the following reasons: (1) The mud screened from engineering residue is not comprised of a single, highly pure secondary clay mineral. It contains a certain proportion of fine particles of primary minerals. Literature [30] indicates that secondary clay minerals without high-temperature modification generally do not harden or contribute to strength. Additionally, XRD analysis has not found components in the residue that could react with the cement. (2) The semi-dry static pressing method used for unburned bricks made from residue soil necessitates the mixture possess a certain level of plasticity. This plasticity is provided by a higher mud content in the residue soil, resulting in a lower strength grade for these unburned bricks. Even if there is a weakening effect, it will not be as pronounced as the weakening effect of secondary clay minerals on the strength of concrete. Therefore, the three different types of mud used in this test have little influence on the compressive strength of residue brick. This also provides a certain reference for practical engineering.

5. Influence of Mud Content on Unburned Brick Strength

5.1. Experimental Design and Implementation

Engineering residual soils typically exhibit a relatively high mud content, which substantially impacts the strength of unburned bricks, normally leading to a reduction in compressive strength. This experimental study investigated the influence of mud content on the strength of unburned bricks made from residual soil. Using mud content as a single variable, eight groups of unburned brick specimens were prepared and tested, each incorporating different mud content levels of 0%, 10%, 20%, 25%, 30%, 40%, 50%, and 60% of the residue soil. Six specimens were prepared for each group, totaling 48 specimens for this experiment. The control specimens are the unburned bricks with a mud content of 0%. Detailed parameters and material compositions for these eight groups of specimens are presented in Table 5. The cementitious material used was P.O42.5 cement, which accounted for 10% of the total solid materials, and the moisture content of the mixture for specimen shaping was maintained at 13%. The specimen shape was a 70 mm cube, and a semi-dry static pressing method with 10 MPa pressure was utilized for unburned brick molding. Fresh bricks were subjected to curing periods of 14 days and 28 days for testing. The washed sand and mud extracted from Residue Soil-A were used for this experimental study, and the sand was mixed to meet the requirements of grading Zone-1 for all specimens.

5.2. Experimental Results and Discussion

The compressive strength of unburned brick specimens with different mud contents was tested at 14 and 28 days of curing, and the results are presented in Figure 14. At different curing ages, the compressive strength of unburned bricks made from residual soil initially increases and then decreases as the mud content in the residual soil increases. When the mud content ranges from 0% to 25%, there is a remarkable increase in the compressive strength of the unburned brick specimens. This increase is particularly notable, with a growth rate of 82.2% at 14 days and 140.2% at 28 days. However, when the mud content ranges from 25% to 60%, the compressive strength of the unburned brick specimens gradually decreases. The decrease amounts to 9.4% at 14 days and 19.8% at 28 days. The maximum compressive strength of the unburned brick specimens, 13.66 MPa at 14 days and 20 MPa at 28 days, is achieved when the mud content is 25%.
Based on the above test, it can be seen that 25% mud content makes the compressive strength of the unburned residue soil brick reach the maximum. When the clay content is less than 25%, the strength of the brick increases with the increase of the clay content. However, when the clay content is greater than 25%, the strength of the brick decreases with the increase of the clay content. As can be seen from Figure 14, the linearity of the relationship between mud content and compressive strength in these two stages is obvious. Therefore, with 25% mud content as the critical point, based on the test data, the relationship between the strength and mud content of 0–25% and 25–60% unburned residue soil bricks is linearly fitted, respectively. The fitted formulas are shown in Figure 13. The influence of mud content within 0–25% on the unburned brick is obviously greater than of that above 25%, and the influence of mud content on the late strength (28 days) is greater than that of the early strength (14 days). These fitted formulas can provide a reference for evaluating the influence of mud content in the actual production of unburned residue soil bricks.
China’s standard [31] has established relevant provisions regarding the mud content in aggregates used for construction projects. The higher the concrete strength grade, the lower the permissible mud content. For concrete strength grades less than C25, the corresponding mud content should not exceed 5%. In special cases, the mud content is further restricted to be below 3%. This emphasizes the desirability of minimizing mud content in concrete. In the context of the unburned residue soil brick tests, it is observed that when the mud content in the residue soil is low (0% and 10%), the compressive strength of the unburned residue soil bricks is considerably compromised. This phenomenon is attributed to the limited presence of cementitious material in the unburned residue soil bricks. In the absence of mud in the residue soil brick or when mud content is low, the mixture exhibits poor plasticity and cannot be compacted effectively under the same molding pressure. Furthermore, after pressure unloading and specimen demolding, unburned bricks with low mud content in the residual soil cannot be promptly moved to their designated curing positions, thereby introducing practical production challenges. During the experiment, it was observed that the samples from the Mud0%-A group exhibited disintegration upon removal. This can be attributed to the initial test pieces of the bricks being inadequately compacted, resulting in insufficient particle bonding, as illustrated in Figure 15.
The unburned residue soil bricks prepared with different mud contents are shown in Figure 16. The surface roughness of these bricks varies with different mud content levels. As the mud content increases from 0% to 60%, the surface of the bricks becomes progressively smoother and finer. The Mud0%-A unburned brick exhibits a pronounced granular texture and a notably rough surface. Reducing the mud content in the residue soil enhances the coarseness of the surface of the unburned residue soil bricks, thereby improving the bond strength between the bricks and mortar. Figure 17 presents the average density and average height of the unburned residue soil bricks with different mud contents. The observed trends in average density and compressive strength of the bricks with different mud contents are consistent, with an initial increase followed by a subsequent decrease. This trend underscores the principle that greater density corresponds to greater strength. Specifically, when the mud content is 25%, both the average density and strength of the unburned bricks reach their maximum values. In contrast, when the mud content is minimal at 0%, the density of the unburned bricks is at its lowest, resulting in the lowest strength. Under the same molding pressures, the average height of the pressed unburned bricks provides insights into the plasticity of the unburned brick mixture. Higher heights indicate reduced plasticity, while lower heights suggest greater plasticity. With increasing mud content in the residue soil, the average height of the unburned bricks initially decreases, followed by an increase. The unburned brick achieves the lowest average height when the mud content is 25%. For cases where the mud content is 0% and 10%, the heights of the unburned bricks measure 76.5 mm and 75 mm, respectively, representing a 2–5 mm elevation compared to other unburned brick samples. This demonstrates that the method of preparing unburned residue soil bricks through press molding can effectively utilize mud, which is considered the most unfavorable component for strength, and increase the required plasticity of the mixture.
Mud in concrete is generally considered to be an adverse component for the following reasons: (1) The clay contained in mud exhibits considerable water absorption properties. Due to its small particle size, large specific surface area, and high water absorption capacity, it affects compactness during the molding process. Furthermore, it may lead to an inadequate supply of water, which is required for cement hydration, thereby affecting strength formation; (2) The clay particles in mud also show strong adsorption capabilities [32,33,34]. Fine particles readily adhere to the surface of aggregates, directly and severely impairing the bond strength between aggregates and cementitious materials. This obstruction hinders the bonding between aggregates and cement, resulting in the formation of a weak bond interface transition zone and consequently affecting the strength of the specimens; (3) The clay particles in mud are prone to particle agglomeration. While a small amount of mud can play a role similar to a micro-aggregate filling, a higher mud content facilitates the aggregation of loose mud particles. This aggregation forms a weak “air space” within the cement hydration products [35,36], reducing their density and impeding cement hydration. Consequently, this further reduces the compressive strength of the concrete.
The mechanism of the presence of mud in residue soil brick and its influence on strength is as follows: When the mud content is below 25%, mud serves a dual role in providing the required plasticity for brick formation and filling voids. As mud content increases, the shape of the brick improves, enabling denser compaction and a corresponding increase in strength. When the mud content is 25%, the shape and filling effect of mud particles are optimized, resulting in superior compactness and maximum compressive strength. However, when the mud content exceeds 25%, the compressive strength of the unburned residue soil brick decreases with increasing mud content. This can be attributed to several factors: (1) Excessive mud fails to enhance the filling effect effectively; (2) A higher mud content exacerbates the challenges associated with residue soil molding, often leading to slurry emergence during the pressing process of production. The mud lost from the mold gaps can carry away a portion of the cementing material; (3) Increased mud content intensifies the agglomeration effect, where clumped mud creates cracks and voids within the brick structure, reducing compressive strength; (4) Excessive mud content, much like in concrete, adversely affects the bond between the cementitious material and aggregates. This results in the formation of weak transition zones within the unburned brick, affecting cement hydration and further reducing strength.
It is worth noting that within the limit of the optimal mud content, the adverse effect of insufficient mud content on the compressive strength of bricks is considerably greater than the negative impact of excessive mud content. This is primarily because inadequate mud content results in the formation of genuine voids within unburned bricks, which has the most adverse effect on the strength of the brick. In this study, the optimal mud content is 25%, and the compressive strength of unburned bricks with mud contents of 20% and 60% is essentially the same. Considering that engineering residue soil generally contains higher mud content, in cases where the optimal mud content cannot be exactly achieved, it is advisable to prioritize the production of unburned bricks with a relatively high mud content. In this test, when the mud content in the residue soil reaches 60%, the unburned residue soil bricks still maintain relatively high compressive strength. This is likely because the granularity of the residual recycled sand used has a large fineness modulus, and the grading area of the residual recycled sand is in Zone 1, with a coarser particle size, allowing for greater capacity to accommodate more mud. Moreover, the larger the fineness modulus of the recycled sand used, the slower the weakening of unburned brick due to the high mud content. Considering the presence of fine sand in the grading zone located in Zone 3 within engineering residue soil, where particle sizes tend to be small and fine, it is suggested that the mud content in the residue soil falls within the range of 25% to 40%.
In summary, when preparing unburned residue soil bricks using the semi-dry static pressing method, the function of mud exhibits a dual nature. Insufficient mud content leads to poor compactness and lower compressive strength of the bricks, while excessive mud content amplifies the softening effect of the mud, reducing brick compactness and the consolidating effect of the cementitious material, ultimately resulting in decreased compressive strength. There exists an optimal mud content, where the filling effect of the mud is maximized, resulting in the highest compressive strength of unburned bricks. If the optimal mud content cannot be achieved in actual production, it is recommended to prioritize the use of unburned bricks with higher mud content. In this study, the optimal mud content of the unburned brick is about 25%, and the optimal mud content may be influenced by the thickness and grading of the sand particles in the unburned brick. It is suggested that the mud content of the engineering residue soil should be maintained within the range of 25–40%.

6. Conclusions

Mud is the main component of engineering residue soil and has a complex composition. Therefore, mud is an important factor affecting the strength and performance of unburned residue soil bricks. In this paper, the physicochemical properties of typical residue soils and their associated muds are tested and analyzed. The unburned residue soil bricks are made using the semi-dry static pressing method. The effects of mud type and mud content on the compressive strength of unburned bricks are investigated based on experiments. The main conclusions are as follows.
(1)
The primary residue soils of silty clay and sandy clay excavated in engineering construction are mainly composed of SiO2 and Al2O3, and the main mineral components are quartz and kaolin. These residue soils have low LOI, consistent chemical and mineral composition, and a mud content of 30–50%, making them suitable for the production of unburned residue soil bricks.
(2)
The chemical and mineral compositions of the three different types of mud used in this study vary considerably. However, they all consist of inert minerals which have a limited influence on the strength performance of unburned residue soil bricks. Therefore, if the composition of mud used is similar to that of the mud used in this paper, the influence of the type of mud on the compressive strength of unburned brick can be ignored in the actual production of unburned residual soil bricks.
(3)
The influence of mud content on the strength performance of unburned bricks is substantial and the mechanism is complex. When the mud content is low, it results in poor molding, impeding effective compaction. This leads to the presence of unfilled voids within the unburned bricks, which considerably weakens their compressive strength, ultimately diminishing the strength of the unburned bricks. Conversely, excessive mud content causes the bricks to soften during formation, reducing compactness. Moreover, the inactive nature of the mud also hinders the hydration consolidation of cementitious materials, further reducing the strength of unburned bricks. Optimal mud content ensures effective filling within the unburned bricks, resulting in well-shaped bricks with high compactness and maximum compressive strength. In this study, the optimal mud content of unburned bricks is 25%. It is recommended that the mud content of the engineering residue soil should be controlled within the range of 25–40%.
(4)
Considering the optimal mud content as the critical value, the weakening effect of insufficient mud content on the compressive strength of unburned bricks is greater than the adverse effect of excessive mud content. In this study, the optimal mud content is 25%, and the compressive strength of the unburned bricks with 20% and 60% mud content is the same. Considering the typically high mud content of residue soil in engineering, it is recommended to use high mud content for unburned bricks in actual production when the optimal mud content cannot be exactly determined and achieved.

Author Contributions

Conceptualization, X.N. and L.Z.; methodology, L.Z. and T.W.; formal analysis, T.W.; investigation, L.Z. and T.W.; resources, Y.L.; writing—original draft preparation, T.W.; writing—review and editing, Y.L.; visualization, Y.L.; supervision, L.Z.; project administration, X.N.; funding acquisition, X.N. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by the Housing and Urban-Rural Development Department Research and Development Program of Guangdong Province (2022-K2-254693) and the Ministry of Housing and Urban-Rural Development of Research and Development Program of the People’s Republic of China (2022-K-044).

Data Availability Statement

The authors believe that all relevant data are already included in the present article. However, if more details are needed, they are available on request from the corresponding author.

Conflicts of Interest

Authors Xingzhong Nong and Yuehua Liang were employed by the company Guangzhou Metro Design & Research Institute Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Chen, Z.; Zeng, H. The current situation of China’s urban construction sludge disposal and countermeasures. J. Nanjing Xiaozhuang Coll. 2003, 19, 84–88. [Google Scholar]
  2. Wang, L.; Xu, B.; Qin, F. China’s construction waste disposal status and analysis. Environ. Health Eng. 2009, 17, 53–56. [Google Scholar]
  3. Weil, M.; Jeske, U.; Schebek, L. Closed-Loop Recycling of Construction and Demolition Waste in Germany in View of Stricter Environmental Threshold Values. Waste Manag. Res. 2006, 24, 197–206. [Google Scholar] [CrossRef]
  4. Zhang, Z.F.; Li, M.D.; Tian, A.G.; Gu, B.W. The properties and feasibility for sintering materials of construction waste residue in lianyungang. J. Jiangsu Constr. 2015, 30, 104–107. [Google Scholar]
  5. Lu, H.X.; Zhang, L.; Gao, K.; Cai, F.Y.; Guo, C.; Zhai, J.M. Preparation of new-type sintered bricks by construction wastes and blast furnace slag. J. New Build. Mater. 2019, 46, 133–137. [Google Scholar]
  6. Guo, C.; Kong, J.; Wang, Z.; Meng, X.; Zhao, Y.; Wu, W.; Quan, H. Study on Preparation and Properties of Sintered Brick from Multi-Source Solid Waste. Appl. Sci. 2022, 12, 10181. [Google Scholar] [CrossRef]
  7. Muñoz, P.; Letelier, V.; Munoz, L.; Gencel, O.; Sutcu, M.; Vasic, M. Assessing technological properties and environmental impact of fired bricks made by partially adding bottom ash from an industrial approach. Constr. Build. Mater. 2023, 396, 132338. [Google Scholar] [CrossRef]
  8. Wang, S.; Gainey, L.; Baxter, D.; Wang, X.; Mackinnon, I.D.; Xi, Y. Thermal behaviours of clay mixtures during brick firing: A combined study of in-situ XRD, TGA and thermal dilatometry. Constr. Build. Mater. 2021, 299, 124319. [Google Scholar] [CrossRef]
  9. Hsu, Y.-S.; Lee, B.-J.; Liu, H. Mixing Reservoir Sediment with Fly Ash to Make Bricks and Other Products. In International Ash Utilisation Symposium; Center for Applied Energy Research, University of Kentucky: Lexington, KY, USA, 2003; Volume 89. [Google Scholar]
  10. Naganathan, S.; Subramaniam, N.; Nasharuddin, B.M.K. Development of Brick Using Thermal Power Plant Bottom Ash and Fly Ash. Asian J. Civ. Eng. (Build. House) 2012, 13, 275–287. [Google Scholar]
  11. Ahmari, S.; Zhang, L. Production of Eco-Friendly Bricks from Copper Mine Tailings through Geopolymerization. Constr. Build. Mater. 2012, 29, 323–331. [Google Scholar] [CrossRef]
  12. Seco, A.; Urmeneta, P.; Prieto, E.; Marcelino, S.; García, B.; Miqueleiz, L. Estimated and Real Durability of Unfired Clay Bricks: Determining Factors and Representativeness of the Laboratory Tests. Constr. Build. Mater. 2017, 131, 600–605. [Google Scholar] [CrossRef]
  13. Seco, A.; Omer, J.; Marcelino, S.; Espuelas, S.; Prieto, E. Sustainable Unfired Bricks Manufacturing from Construction and Demolition Wastes. Constr. Build. Mater. 2018, 167, 154–165. [Google Scholar] [CrossRef]
  14. Espuelas, S.; Omer, J.; Marcelino, S.; Echeverría, A.M.; Seco, A. Magnesium Oxide as Alternative Binder for Unfired Clay Bricks Manufacturing. Appl. Clay Sci. 2017, 146, 23–26. [Google Scholar] [CrossRef]
  15. Ye, C.; Yan, X.; Shi, B.; Zhang, B. Study on the preparation of no-burn bricks using excavated clay from civil engineering works. Nonmet. Ore 2014, 37, 25–27. [Google Scholar]
  16. Yao, Q.; Cai, K.; Liu, C.; Ling, F.; Wang, S. Research on the proportioning and mechanical properties of no-burn bricks of pit residue in pulverised clay strata. Tunn. Constr. 2020, 40, 145–151. [Google Scholar]
  17. Guo, X.; Chen, Z.; Pei, L.; Li, J.; Fan, C. Preparation and property characterisation of modified slag cement-slag free bricks. New Build. Mater. 2020, 47, 75–79. [Google Scholar]
  18. Guo, A.; Wei, X.; Wang, Y.; Fang, J.; Zeng, L. Research on the preparation and properties of no-burn bricks made of residual soil. Nonmet. Ore 2021, 44, 99–102. [Google Scholar]
  19. Chen, R. Resourceful Application of Engineering Waste Soil in New Type of Raw Soil-Based Thermal Insulation Hollow Bricks. Ph.D. Thesis, Huaqiao University, Quanzhou, China, 2021. [Google Scholar]
  20. Wang, P.Z. Preliminary Study on the Preparation and Performance of No-Burn Bricks Made of Engineering Residue. Master Thesis, South China University of Technology, Guangzhou, China, 2022. [Google Scholar]
  21. Wu, X.; Zhou, L.R.; Xia, T.; Xu, Y.Q. Experimental study on material mix ratio of engineering residue unburned brick. Ind. Constr. 2023, 53 (Suppl. S2), 739–744. [Google Scholar]
  22. Bian, L.B.; Zha, Y.; Zhang, Z.; He, L.C.; Hu, X.B. Study on Preparation and Properties of Non- Fired Bricks by Shield Muck. J. Beijing Univ. Civ. Eng. Archit. 2023, 39, 62–69. [Google Scholar]
  23. Wang, S.; Gainey, L.; Marinelli, J.; Deer, B.; Wang, X.; Mackinnon, I.D.; Xi, Y. Effects of vermiculite on in-situ thermal behaviour, microstructure, physical and mechanical properties of fired clay bricks. Constr. Build. Mater. 2022, 316, 125828. [Google Scholar] [CrossRef]
  24. GB/T 14684-2022; Construction Sand 2022. Standards Press of China: Beijing, China, 2022.
  25. GB/T 2542-2012; Test Method for Wall Bricks 2012. Standards Press of China: Beijing, China, 2012.
  26. Lai, G.; Fang, Y.; Zhang, W.; Liu, M.; Lai, H. Influence of clay on the properties of glued sand and concrete with polycarboxylic acid water reducing agents. New Build. Mater. 2016, 43, 23–26. [Google Scholar]
  27. Zhou, Y. A review of the effect of clayey fine particles in aggregates on concrete properties and control methods. Silic. Bull. 2015, 34, 433–437+443. [Google Scholar]
  28. Yool, A.I.G.; Lees, T.P.; Fried, A. Improvements to the Methylene Blue Dye Test for Harmful Clay in Aggregates for Concrete and Mortar. Cem. Concr. Res. 1998, 28, 1417–1428. [Google Scholar] [CrossRef]
  29. Wang, Y.; Wang, Z.; Hu, Q.; Li, Y.; Liu, C. Clayey mud in aggregates and its effect on concrete properties. Silic. Bull. 2012, 31, 599–603. [Google Scholar]
  30. Fernandes, V.A.; Purnell, P.; Still, G.T.; Thomas, T.H. The Effect of Clay Content in Sands Used for Cementitious Materials in Developing Countries. Cem. Concr. Res. 2007, 37, 751–758. [Google Scholar] [CrossRef]
  31. JGJ 52-2006; Standard for Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel) for Ordinary Concrete. China Building Industry Press: Beijing, China, 2006.
  32. Winnefeld, F.; Böttger, K.G. How Clayey Fines in Aggregates Influence the Properties of Lime Mortars. Mater. Struct. 2006, 39, 433–443. [Google Scholar] [CrossRef]
  33. Norvell, J.K.; Stewart, J.G.; Juenger, M.C.; Fowler, D.W. Influence of Clays and Clay-Sized Particles on Concrete Performance. J. Mater. Civ. Eng. 2007, 19, 1053–1059. [Google Scholar] [CrossRef]
  34. Courard, L.; Michel, F.; Pierard, J. Influence of Clay in Limestone Fillers for Self-Compacting Cement Based Composites. Constr. Build. Mater. 2011, 25, 1356–1361. [Google Scholar] [CrossRef]
  35. Yao, J.; Zhou, Z.; Li, B. Effect of Sand Clay Content on Concrete Properties. Commer. Concr. 2014, 5, 67–69. [Google Scholar]
  36. Xiao, H.; Zeng, H.; Huang, L.; Liu, L.; Li, B.; Yuan, Z.; Zhong, Z. Experimental Investigation on the Influence of Strength Grade on the Surface Fractal Dimension of Concrete under Sulfuric Acid Attack. Buildings 2024, 14, 713. [Google Scholar] [CrossRef]
Buildings 14 01949 g001
Figure 1. Flowchart of this study.
Figure 1. Flowchart of this study.
Buildings 14 01949 g001
Buildings 14 01949 g002
Figure 2. Three kinds of engineering residue soil.
Figure 2. Three kinds of engineering residue soil.
Buildings 14 01949 g002
Buildings 14 01949 g003
Figure 3. XRD spectra and mineral compositions of the three engineering residue soils.
Figure 3. XRD spectra and mineral compositions of the three engineering residue soils.
Buildings 14 01949 g003
Buildings 14 01949 g004
Figure 4. Three different types of mud.
Figure 4. Three different types of mud.
Buildings 14 01949 g004
Buildings 14 01949 g005
Figure 5. Mineral composition and proportion of three kinds of mud.
Figure 5. Mineral composition and proportion of three kinds of mud.
Buildings 14 01949 g005
Buildings 14 01949 g006
Figure 6. Process flow of the raw residue soil material processing.
Figure 6. Process flow of the raw residue soil material processing.
Buildings 14 01949 g006
Buildings 14 01949 g007
Figure 7. Recycled sand from the residue soil.
Figure 7. Recycled sand from the residue soil.
Buildings 14 01949 g007
Buildings 14 01949 g008
Figure 8. Particle gradation of the recycled sand from residue soil.
Figure 8. Particle gradation of the recycled sand from residue soil.
Buildings 14 01949 g008
Buildings 14 01949 g009
Figure 9. Production process of unburned engineering residue soil brick.
Figure 9. Production process of unburned engineering residue soil brick.
Buildings 14 01949 g009
Buildings 14 01949 g010
Figure 10. Natural curing of the unburned brick specimens.
Figure 10. Natural curing of the unburned brick specimens.
Buildings 14 01949 g010
Buildings 14 01949 g011
Figure 11. Compressive strength testing of unburned bricks.
Figure 11. Compressive strength testing of unburned bricks.
Buildings 14 01949 g011
Buildings 14 01949 g012
Figure 12. Unburned residue soil bricks made using different mud types.
Figure 12. Unburned residue soil bricks made using different mud types.
Buildings 14 01949 g012
Buildings 14 01949 g013
Figure 13. Effect of mud type on the compressive strength of unburned residue soil brick.
Figure 13. Effect of mud type on the compressive strength of unburned residue soil brick.
Buildings 14 01949 g013
Buildings 14 01949 g014
Figure 14. Effect of mud content on compressive strength of unburned residue soil brick.
Figure 14. Effect of mud content on compressive strength of unburned residue soil brick.
Buildings 14 01949 g014
Buildings 14 01949 g015
Figure 15. Unburned brick without mud.
Figure 15. Unburned brick without mud.
Buildings 14 01949 g015
Buildings 14 01949 g016
Figure 16. Surface characteristics of unburned bricks with different mud contents.
Figure 16. Surface characteristics of unburned bricks with different mud contents.
Buildings 14 01949 g016
Buildings 14 01949 g017
Figure 17. Compaction degree of unburned residue soil bricks with different mud contents.
Figure 17. Compaction degree of unburned residue soil bricks with different mud contents.
Buildings 14 01949 g017
Table 1. Chemical compositions of the three engineering residue soils.
Table 1. Chemical compositions of the three engineering residue soils.
MaterialsComposition Ratio (Mass Fraction %)
SiO2Al2O3K2OFe2O3TiO2CaOMgOMnOOtherLOI
Residue Soil-A73.1915.953.401.750.150.130.110.060.245.02
Residue Soil-B67.0520.713.801.750.210.030.100.160.255.94
Residue Soil-C61.8118.700.348.351.370.030.030.050.179.15
Table 2. Particle size distributions and mud contents of the three kinds of engineering residue soil.
Table 2. Particle size distributions and mud contents of the three kinds of engineering residue soil.
MaterialsParticle Size Distribution (Mass Fraction %)
>4.75 mm4.75~2.36
mm		2.36~1.18
mm		1.18~0.6 mm0.6~0.3 mm0.3~0.15
mm		0.15~0.075 mmMud Content
(<0.075 mm)
Residue Soil-A08.27.213.923.210.57.529.5
Residue Soil-B010.617.59.015.66.25.935.3
Residue Soil-C01.04.14.520.012.26.951.2
Table 3. Chemical components of the three types of mud.
Table 3. Chemical components of the three types of mud.
MaterialsComposition Ratio (wt. %)Loss on Ignition
SiO2Al2O3K2OFe2O3TiO2CaOMgOMnOOther
Mud-A66.7921.923.942.750.280.310.210.070.223.51
Mud-B50.7035.452.792.490.230.030.270.090.537.42
Mud-C58.8022.451.289.682.190.070.140.060.295.05
Table 4. Particle gradations of recycled sand from engineering residue soils.
Table 4. Particle gradations of recycled sand from engineering residue soils.
MaterialsCumulative Square Screen Balance (Mass Fraction /%)
4.75 mm2.36 mm1.18 mm0.6 mm0.3 mm0.15 mm
Residue Soil-A011.721.841.574.489.3
Residue Soil-B016.343.357.381.490.9
Residue Soil-C02.110.519.760.885.8
Table 5. Mixing ratio of materials for each specimen group.
Table 5. Mixing ratio of materials for each specimen group.
Group Number Mud ContentWater
(kg)		Solid Mass (kg)
SandMudCement
10%0.112 0.673 0.000 0.075
210%0.112 0.606 0.067 0.075
320%0.112 0.539 0.135 0.075
425%0.112 0.505 0.168 0.075
530%0.112 0.471 0.202 0.075
640%0.112 0.404 0.269 0.075
750%0.112 0.337 0.337 0.075
860%0.112 0.269 0.404 0.075
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Nong, X.; Zhou, L.; Liang, Y.; Wang, T. Experimental Study and Analysis of the Effects of Mud on the Compressive Strength of Unburned Brick Using Engineering Residue Soil. Buildings 2024, 14, 1949. https://doi.org/10.3390/buildings14071949

AMA Style

Nong X, Zhou L, Liang Y, Wang T. Experimental Study and Analysis of the Effects of Mud on the Compressive Strength of Unburned Brick Using Engineering Residue Soil. Buildings. 2024; 14(7):1949. https://doi.org/10.3390/buildings14071949

Chicago/Turabian Style

Nong, Xingzhong, Linren Zhou, Yuehua Liang, and Taojun Wang. 2024. "Experimental Study and Analysis of the Effects of Mud on the Compressive Strength of Unburned Brick Using Engineering Residue Soil" Buildings 14, no. 7: 1949. https://doi.org/10.3390/buildings14071949

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop