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The partial replacement of conventional natural coarse aggregate (NCA) with artificial light weight aggregate (LWA) manufactured from local clay and solid waste to develop a lightweight aggregate concrete (LWAC) for the structural use was studied in this paper. Red clay and Savar clay were used individually with solid wastes like rice husk ash (RHA) and waste glass to produce LWA. The suitability of raw materials and LWA was evaluated by investigating various properties. The mechanical, thermal and durability properties of manufactured LWAC were explored. The results of physical, chemical, thermal and geotechnical properties revealed that Red clay is better than Savar clay for the preparation of LWA. All the physical and mechanical properties of LWA prepared from Red clay are suitable for the preparation of LWAC compared to Savar clay. The test results demonstrated that the concrete manufactured by replacing 30 % of NCA with LWA produced a concrete of lightweight properties. The compressive strength of LWAC for 7 and 28 days was observed as 28 and 48 MPa, respectively. The results of modulus of elasticity, splitting tensile strength, flexural deformation, and creep test of LWAC revealed that these mechanical properties meet the requirements for the structural concrete. The RCP test proves that chlorine permeability of LWAC is comparable with NCA. It was observed that the superior performance of LWAC can be achieved only when the optimized mix designed is followed strictly. The suitability of the replacement of natural aggregate by LWA may be helpful for Bangladesh due to the scarcity of natural coarse aggregate and reusability of solid waste materials.

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Autotrophic microorganisms, the pivotal carbon fixers, exhibit a broad distribution across diverse environments, playing critical roles in the process of carbon sequestration. However, insights into their distribution characteristics in aquifers, particularly in those petroleum-hydrocarbon-contaminated (PHC) aquifers that were known for rich in heterotrophs, have been limited. In the study, groundwater samples were collected from red clay aquifers in the storage tank leakage area of a PHC site, a prevalent aquifer type in southern China and other regions. Metagenomics combined with hydrochemical and inorganic carbon isotope analyses were employed to elucidate the presence of microbial carbon fixation and its driving forces. Results showed that there were hundreds of autotrophic microorganisms participating in distinct carbon fixation processes in the red clay PHC aquifers. Reductive tricarboxylic acid (rTCA) and dicarboxylate/4-hydroxybutyrate (DC/4HB), as well as 3-hydroxypropionate (3HP or/and 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB)) were the predominant carbon fixation pathways. The abundances of carbon fixation genes and autotrophic microorganisms were significantly and positively correlated with hydrocarbon concentrations and δ13C of dissolved inorganic carbon (δ13C-DIC) values. This finding indicated that the petroleum hydrocarbon significantly promoted the proliferation of carbon fixation microorganisms, leading to a substantial uptake of inorganic carbon. Therefore, we deduce that this process holds considerable potential for carbon sequestration in PHC-contaminated aquifers.

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Pb-contaminated soil poses significant environmental and health risks as well as soil stability issues. Research on sandy soils highlights CO2-enhanced reactive MgO as a promising solution for improving the solidification of Pb-contaminated soils. However, carbonation effects can differ markedly between soil types owing to varying soil properties. In this study, we evaluated the effects of CO2-enhanced reactive MgO on the engineering and environmental characteristics of Pb-contaminated red clay and explored its mechanism of carbonation solidification. The results showed that CO2-enhanced reactive MgO increased the strength of Pb-contaminated red clay to over 3 MPa within 1 h, which was approximately 25 times the strength of untreated soil (0.2 MPa) and significantly higher than that of reactive MgO-treated, uncarbonated soil (0.8 MPa). The pH of the carbonated soil (9-10) facilitated Pb2+ immobilization, and the increase over the initial parameter elevated the electrical conductivity value. Moreover, CO2-enhanced reactive MgO reduced the Pb2+ leaching concentration to below 0.1 mg/L, even at high Pb concentrations (10,000 mg/kg). Pb2+ transformed into lead carbonates during the carbonation process, with the hydrated magnesium carbonates forming a dense internal structure. This solidification mechanism included chemical precipitation, physical adsorption, and encapsulation. Notably, the carbonation time should be controlled within 1 h to prevent soil expansion. Together, these findings support the potential of CO2-enhanced reactive MgO for efficient and low-carbon application in the solidification of Pb-contaminated red clay.

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Ionizing radiation is valuable for healthcare, industry, and agriculture. However, excessive exposure to ionizing radiation is detrimental to humans and the environment. Radiation protection aims at protecting people and the environment from the harmful effects of ionizing radiation. This work aimed to study the effectiveness of composites of red clay and waste glass for ionizing radiation shielding. Five samples of different mix ratios of red clay to waste glass were fabricated into different dimensions using hand molding, dried, and burnt. The samples were characterized for ionizing radiation shielding. Monte-Carlo simulation was done using the GEANT4 toolkit and web-based NIST-XCOM photon attenuation database. The findings show that the measured half value layer (HVL) for the composite bricks showed a linear decrease from (6.13± 0.10) cm for the CNT sample that had 0 % waste glass to (4.62± 0.12) cm for the RCG11 sample that had 50 % waste glass. The GEANT4 simulated HVL values for CNT and RCG11 samples were (6.05±0.01) cm and (4.79±0.01) cm respectively. The NIST-XCOM values were (6.09±0.09) cm and (4.81± 0.01) cm for CNT and RCG11 respectively. The measured and simulated results were in good agreement. The findings of this study indicate an improvement in the shielding properties of red clay with the addition of waste glass and will promote radiation safety by providing an environmentally friendly alternative shielding material.•Proper shielding is key in promoting radiation safety and protection. There is a need for alternative shielding materials that can be used for walling during the construction of structures that house radioactive materials.•Red clay and waste glass composite bricks can provide alternative ionizing radiation shielding material.•This study will promote environmentally friendly practices in radiation safety and protection.

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This study involves the characterization and analysis of a Chinese red clay obtained from Hunan province to determine its suitability for manufacturing ceramic products. X-ray fluorescence analysis showed the clay has high silica (63.25 weight percent) and alumina (21.38 weight percent) content along with iron oxide, alkalis, and calcium acting as fluxes. X-ray diffraction (XRD) confirmed the presence of quartz, kaolinite, illite, and hematite as the major mineralogical phases. Scanning electron microscopy revealed loosely stacked, plate-shaped kaolinite particles exhibiting pseudohexagonal morphology. Particle size distribution shows a d50 of 12.7 µm and specific surface area is 21.3 m2/g. Differential thermal analysis-thermogravimetric analysis showed mass losses between 450-600°C and 950-1050°C corresponding to dehydroxylation and formation of a liquid phase, respectively. Dilatometry traced the onset of viscous flow sintering around 1000°C. Test bars produced from the clay were fired at 800°C, 900°C, 950°C, 1000°C, and 1050°C. The firing shrinkage increased from 2.5% at 800°C to 12.8% at 1050°C. Strength improved from 11.2 megapascals at 800°C to 42.3 megapascals at 1050°C due to densification and mullite formation. Hematite content caused the color to change from orange-red at 950°C to dark red at 1050°C. XRD analysis of fired specimens confirmed the presence of hematite and newly formed mullite and cristobalite phases. The results indicate the suitability of the clay for manufacturing bricks, roof tiles, and wall tiles using appropriate firing temperatures and cycles.

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The main objective of this research is to study the influence of partial replacement of calcined red clay by gypsum-bonded casting investment waste (GCIW) from precious metal casting process on geopolymerization reaction of a red clay-based geopolymer. Calcined red clay was partially replaced by GCIW powder with different contents before mixing with sodium-based alkali activator solution to produce the geopolymers. The results indicate that the GCIW significantly impacted the reaction of flesh geopolymers detected by Differential scanning calorimetry (DSC). The reaction products (hydration products and others) of 28-day geopolymers detected by Fourier transform Infrared spectroscopy (FTIR) and X-ray diffractometry (XRD) were employed to support the reaction results. Moreover, the relation between reaction products and compressive strength was discussed. This work concluded that the calcium sulfate compounds contained in GCIW play an important role on geopolymerization reaction, reaction products, and mechanical properties of geopolymer. Furthermore, the results could be employed to propose a reaction mechanism that occurred in geopolymers. The potential use of GCIW as an additive for red clay-based geopolymer bricks preparation was confirmed in this research.

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This research was undertaken to optimize the phenolic compound removal from Olive Mill Wastewater (OMW) by sawdust and red clay as natural adsorbents. Fractional factorial experimental design at 25-1 was used in order to optimize the experimental conditions for high removal efficiency. Statistics ANOVA analysis, Fisher's test, and Student's test suggested that the adsorbent dose has the most significant influence on polyphenol removal for both adsorbents. The maximum removal of polyphenols by sawdust reached 49.6% at 60 °C by using 60 g/L of adsorbent dose, pH 2, reaction time of 24 h, and agitation speed of 80 rpm. Whereas, for red clay, 48.08% of polyphenols removal was observed under the same conditions for sawdust except the temperature of 25 °C instead of 60 °C. In addition, the thermodynamic parameters suggested spontaneous process for both adsorbents, endothermic for the sawdust and exothermic for red clay. Furthermore, the phytotoxicity effect of OMW on durum wheat (Triticum turgidum L. var. durum) and white bean (Phaseolus vulgaris L.) seed germination was investigated. The obtained results showed that the untreated OMW inhibited the seed germination of T. turgidum and P. vulgaris seeds. OMW treatment with red clay followed by dilution (95% water) resulted in 87 and 30% germination of P. vulgaris and T. turgidum, respectively. While, the treatment of OMW with sawdust and dilution at 95% resulted in 51 and 26% germination of P. vulgaris and T. turgidum, respectively.

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Tailings produced by mining engineering and metal smelting industries have become a major challenge to the ecological environment and human health. Environmental compatibility, mechanical stability, and economic feasibility have restricted the treatment and reuse of tailings. A novel solidification/stabilization technology using hydantoin epoxy resin (HER) and red clay for copper tailing treatment was developed, and the leaching behaviors of solidified/stabilized copper tailings were investigated in this paper. The leaching characteristics were analyzed by toxicity characteristic leaching procedure (TCLP) leaching tests. Besides, the influence of red clay content and acid rain on the permeability characteristics and leaching characteristics were investigated based on flexible-wall column tests and microstructure tests. The results showed that the copper tailings solidification/stabilization technology with HER and red clay had excellent performances in toxicity stabilization. The leaching concentration of Cu in TCLP tests and flexible wall column tests remained within the limit specified by the Chinese national standard, and the concentration of Cu decreased significantly with the increase of the red clay content. Moreover, acid rain leaching changed the mineral composition and microstructure of solidified tailings, and the porosity of the samples increased with the dissolution of soluble minerals. Additionally, the hydraulic conductivities decreased slightly with the increase in the pH value of acid rain, and the solidified sample with 5% red clay had the lowest hydraulic conductivity.

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Red clay, a widely distributed soil, weakens significantly when exposed to water. This poses challenges for using it as a foundation for urban infrastructure, as rainwater scouring, infiltration, and external loads can cause uneven settlement and landslides, compromising structural integrity. To address this issue, we propose the use of a green highly permeable water-soluble polyurethane material (PSP) as an alternative to conventional curing agents. We conducted a series of tests to evaluate the efficacy of PSP in improving the mechanical properties of red clay. Acoustic emission tests were used to examine the failure mode of PSP-stabilized red clay, while scanning electron microscopy provided microscopic insights into clay stabilization mechanisms. The triaxial test results establish empirical relationships between strength, stiffness, toughness, and control parameters (PSP content, moisture content, and confining pressure) of the stabilized clay. We found that PSP-stabilized soils exhibit ductile failure and strain hardening, with PSP curing agents effectively enhancing clay strength and stiffness within a 3-day curing period. Univariate analysis reveals positive correlations between peak energy absorption values, peak stress rates, and PSP content, while showing a negative correlation with moisture content. Confining pressure variations have relatively little effect on peak stress ratios of PSP soils, and PSP soil stiffness minimally influences confining pressure as PSP content increases. Importantly, PSP treatment significantly increases ductility compared to untreated clay soils, distinguishing PSP soils from hydric soils.

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Acyclovir (ACV) is a promising candidate for drug repurposing because of its potential to provide an effective treatment for viral infections and non-viral diseases, such as cancer, for which limited treatment options exist. However, its poor physicochemical properties limit its application. This study aimed to formulate and evaluate an ACV-loaded red clay nanodrug delivery system exhibiting an effective cytotoxicity. The study focused on the preparation of a complex between ACV and red clay (RC) using sucrose stearate (SS) (nanocomplex F1) as an immediate-release drug-delivery system for melanoma treatment. The synthesized nanocomplex, which had nanosized dimensions, a negative zeta potential and the drug release of approximately 85% after 3 h, was found to be promising. Characterization techniques, including FT-IR, XRD and DSC-TGA, confirmed the effective encapsulation of ACV within the nanocomplex and its stability due to intercalation. Cytotoxicity experiments conducted on melanoma cancer cell lines SK-MEL-3 revealed that the ACV release from the nanocomplex formulation F1 effectively inhibited the growth of melanoma cancer cells, with an IC50 of 25 ± 0.09 µg/mL. Additionally, ACV demonstrated a significant cytotoxicity at approximately 20 µg/mL in the melanoma cancer cell line, indicating its potential repurposing for skin cancer treatment. Based on these findings, it can be suggested that the RC-SS complex could be an effective drug delivery carrier for localized cancer therapy. Furthermore, the results of an in silico study suggested the addition of chitosan to the formulation for a more effective drug delivery. Energy and interaction analyses using various modules in a material studio demonstrated the high stability of the composite comprising red clay, sucrose stearate, chitosan and ACV. Thus, it could be concluded that the utilization of the red clay-based drug delivery system is a promising strategy to improve the effectiveness of targeted cancer therapy.

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In the present work, composites with non-toxic metal oxides, such as TiO2 and ZnO, and a natural red clay (taua) reach in hematite were used in the photocatalytic degradation of Fenthion. The composite TiO2/Taua (0.5:1 wt. ratio) and pure TiO2 were prepared by sol-gel method while ZnO/Taua (0.5:1 wt. ratio) and pure ZnO were prepared by Pechini method. The materials were characterized by XRD, SEM, EDX, and DRS. The anatase phase was formed in both pure TiO2 and TiO2/Taua, while the hexagonal phase was formed in pure ZnO and ZnO/Taua. The bandgap energies for the two composites were narrowed compared to the respective pure oxides as consequence of the hematite (α-Fe2O3, Eg = 2.1 eV) in the red clay, reaching 2.1 eV for TiO2/Taua and 2.0 eV for ZnO/Taua, while the bandgap energies for pure TiO2 and ZnO were 3.2 and 3.0 eV, respectively. Fenthion was not degraded in the dark, but the concentration droped 20% after 180 min under visible light irradiation without photocatalyst and 60% after 210 min in the presence of the pure red clay. Both TiO2/Taua and ZnO/Taua composites were also photocatalytic active to degrade Fenthion (λ > 420 nm), with degradation of 78% (in 180 min) and 85% (in 210 min) respectively. In the optimized conditions (pH 2, 100 mg L-1 of H2O2 and 30 mg L-1 of Fenthion), the ZnO/Taua composite was the most efficient, reaching 89% degradation in up to 30 min, with Fenthion sulfoxide as the degradation product.

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Globally, there is a growing concern about air pollution due to rapid industrialization and urbanization. Therefore, in this study, an experimental study was conducted to evaluate the performance of reducing nitrogen oxides, a precursor to fine dust, in mortars coated with a titanium dioxide (TiO2) photocatalyst, which has the effect of decomposing pollutants. In particular, in this study, zeolite and activated red clay were used as cement substitutes to improve the fine dust reduction performance of the TiO2 photocatalyst. A total of 14 different mixtures were designed, considering the substitution rates of zeolite and activated red clay (30%, 40%, and 50%) and the cement-fine aggregate ratio (1:2 and 1:3) as experimental variables. A TiO2 photocatalyst was employed in this study to evaluate the NOx reduction performance. As zeolite and activated red clay were added, the compressive strength and flexural strength of the mortars decreased by 15% to 60%, while the absorption rate increased by 5% to 16%. The NOx reduction efficiency of up to 67.4% was confirmed in the H50-3 specimen with the TiO2 catalyst. The NOx reduction performance of mortars with the TiO2 photocatalyst sprayed on their surface improved as the substitution ratio of zeolite and activated red clay increased. Additionally, it was confirmed that the NOx reduction effect of specimens using activated red clay was superior to those using zeolite. Therefore, through this study, it was confirmed that the NOx reduction performance of the TiO2 photocatalyst can be improved when zeolite and activated red clay are used as cement substitutes.

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To investigate the influencing factors and mechanisms of shear strength of red clay with a high liquid limit, which was selected at different milepost locations based on the Nanning Bobai Nabu Section Project of the Nanning Zhanjiang Expressway, the basic physical properties of red clay were determined using a liquid plastic limit test, compaction test, inductively coupled plasma optical emission spectrometer (ICP-OES), and X-ray fully automatic diffractometer (XRD). Red clay with a high liquid limit was selected. Furthermore, the direct shear test was used to study the effect of different water contents and compaction degrees on the shear strength. The experimental results demonstrate that under the same compaction degree, the shear stress of the soil sample increases significantly with an increase in normal stress, and the greater the water content, the smaller the shear stress of the soil sample. At 200 kPa, the shear strength of soil samples with 24% water content is 57%, 46%, and 35% of the shear strength of soil samples with 15% water content under different compaction degrees(K) of 86%, 90%, and 93%, respectively. Under the same moisture content, the shear stress of the soil sample shows an increasing trend with an increase in the degree of compaction, and the greater the compaction degrees, the greater the shear stress of the soil sample. The cohesion c and internal friction angle φ of soil samples increase with an increase in the compaction degree, but the increase in cohesion c is also affected by the water content. Under the condition of low water content, the cohesion c of soil samples can be increased by 1.06 times when the water content is 15% and by 0.47 times when the water content is 18%. Under the condition of high water content, the cohesion c of soil samples with 21% water content only increases by 0.3 times, and that with 24% water content only increases by 0.35 times.

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In this research, the mechanical behavior of masonry mortars made with partial substitution of sand by recycled fine aggregates (RFAs) of mortar (MT) and recycled clay brick (RCB) was compared. Mortar specimens were built in two groups (MT and RCB) considering different replacement proportions by dry weight. To reduce the water absorption of RFAs during mortar making, the prewetting method was utilized. All the mixtures were assembled with a volumetric cement-to-aggregate ratio of 1:4 and a consistency of 175 ± 5 mm. The properties in the fresh and hardening state of mortars were analyzed separately. The experimental results showed that the properties of mortars in a fresh state (bulk density and air content) were affected if RFA was added to the mixture; however, mortars assembled with up to 40% and 50% of MT and RCB, respectively, accomplished a compressive strength value of reference for new mixtures. Both mortar groups showed good results in adhesive strength values, with the RCB mortars standing up as they achieved greater adherence than the control mortar with substitution percentages of up to 30%. Therefore, the reutilization of both RFAs is feasible, notably in rendering and bonding functions.

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Annual coffee consumption has increased to 10 million tons. Of the coffee consumed, 65% is discarded as spent coffee grounds (SCG). However, most SCG are buried in the ground as organic waste. The more coffee consumption increases, the more land is used for disposing of spent coffee. SCG recycling has gotten considerable attention as a solution involved in these issues. The construction community has studied means and methods to recycle SCG as construction materials, such as bricks, subgrade fillers, thermal insulators, etc. This paper presents a new method, which recycles SCG as a construction material, maximally using its acidity. The SCG were hardened with natural binders (i.e., animal glue (AG) and starch (S)) and red clay (RC). The SCG mixtures were pressed with 2 MPa in a cylindrical mold and cured for 7 days. Then, the strength, durability, and pH tests were measured. The AG- and RC-treated SCG sample, which outputs 1933 kPa of strength and a 4.9 pH value, is identified as the optimal sampling method among the acid materials produced in this study. The optimal sample decreases the pH to approximately 7 of water where 68% weight of Ordinary Portland cement was soaked in.

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In order to study the effect of cadmium ions on the mechanical properties and micro-structure characteristics of the red clay in Guilin, we have conducted triaxial test and the scanning electron microscope tests to analyze the effects of cadmium ion concentration and the number of dry and wet cycles on the mechanical properties and micro-structure changes of the red clay. The results showed the effects of cadmium ions and dry-wet cycles destroy the structure of red clay. The cohesive force of red clay decreases with the increase of cadmium ion concentration, and the internal friction angle first increases and then decreases. With the rise in the number of dry and wet cycles, the cohesive force of cadmium-contaminated red clay first increases and then decreases, and the angle of internal friction rises gradually. Under the action of different cadmium ion concentrations, the stress-strain curve is strain hardening. With the concentration of cadmium ions increases, the strain hardening becomes more apparent; the peak value reached faster. and the axial strain corresponding to the peak value of the line decreases. With the increase in the number of wet and dry cycles, the volume of cadmium-contaminated red clay shrinks and its compactness increases; it gets the peak shear strength faster during the shearing process, and its peak value becomes larger and larger. The main reason for the phenomenon is that cadmium ions destroy the cementation between the particles. The soil particles are mainly in point contact which loosens the structure of the soil; on the other hand, the thickness of the surface diffusion layer of the clay particles increases through chemical action, The exchange of cations increases the porosity of the soil and weakens its strength. The dry-wet cycle shrinks the volume of the red clay, and the soil particles are mainly in surface contact; as the number of dry-wet cycles increases, the soil particles connection is closer, the soil porosity decreases and the strength increases.

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We prepared red clays by introducing different percentages of PbO, Bi2O3, and CdO. In order to understand how the introduction of these oxides into red clay influences its attenuation ability, the mass attenuation coefficient of the clays was experimentally measured in a lab using an HPGe detector. The theoretical shielding capability of the material present was obtained using XCOM to verify the accuracy of the experimental results. We found that the experimental and theoretical values agree to a very high degree of precision. The effective atomic number (Zeff) of pure red clay, and red clay with the three metal oxides was determined. The pure red clay had the lowest Zeff of the tested samples, which means that introducing any of these three oxides into the clay will greatly enhance its Zeff, and consequently its attenuation capability. Additionally, the Zeff for red clay with 10 wt% CdO is lower than the Zeff of red clay with 10 wt% Bi2O3 and PbO. We also prepared red clay using 10 wt% CdO nanoparticles and compared its attenuation ability with the red clay prepared with 10 wt% PbO, Bi2O3, and CdO microparticles. We found that the MAC of the red clay with 10 wt% nano-CdO was higher than the MAC of the clay with microparticle samples. Accordingly, nanoparticles could be a useful way to enhance the shielding ability of current radiation shielding materials.

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The use of nontraditional soil stabilizers increases. Various new soil binding agents are under study to augment renewability and sustainability of an earth structure. However, despite increasing interest involved in red clay, there is minimal research investigating the stabilizing red clay with polymer. This paper presents the findings obtained by applying the acrylic polymer and epoxy emulsion as binding agent for red clay and that for sand. The epoxy-hardener ratio, amount of epoxy emulsion, and amount of polymer aqueous solution were manipulated to quantify their effects on red clay and sand, respectively. After compacting a pair of cylindrical samples of which diameter and height are 5 cm and 10 cm, respectively, it is cured for 3 and 7 days in a controlled condition. Each pair is produced to represent the engineering performance at each data point in the solution space. An optimal composition of the binding agents for red clay and that for sand mixture are identified by experimenting every data point. In addition, given lime into each sample, the maximum unconfined compressive strength (UCS) endured by red clay sample and that by sand sample are 2243 and 1493 kPa, respectively. The UCS obtained by the sample mixed with clay and sand reaches 2671 kPa after seven days of curing. It confirms that the addition of lime remarkably improves the UCS. When the clay-sand mixture, of which the ratio is 70:30, includes 5% lime, the UCS of the mixture outperforms. Indeed, these findings, i.e., the optimal proportion of components, may contribute to the increase of initial and long-term strength of an earth structure, hence improving the renewability and sustainability of the earth construction method.

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 Existing rammed earth construction methods have disadvantages such as increased initial costs for manufacturing the large formwork and increased labor costs owing to the labor-intensive construction techniques involved. To address the limitations of the existing rammed earth construction methods, an autonomous rammed earth construction method was introduced herein. When constructing an autonomous rammed-earth construction method, an alternative means of assuring the performance at the initial age of the binder in terms of materials is needed. In this study, in order to satisfy the performance of the red clay binder, epoxy emulsion was added to analyze the compressive strength, water loosening, shrinkage, rate of mass change, and microstructure in the range of the initial age. As a result of the analysis, the applicability of the epoxy emulsion was confirmed as a new additive for application to an autonomous rammed-earth construction method.

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The leachate (pH = 14) from alumina production changes the mechanical properties of red clay, and the shear strength parameters of the system vary due to the multiple-dimensional interactions of the microscopic parameters. In this paper, the alumina production liquid and the concentrations of the NaOH solution were designed to contaminate the red clay during 80 days. The cohesion and friction angle of the alkaline-contaminated red clay were obtained from direct shear tests. Through qualitative and quantitative analyses using scanning electron microscopy (SEM), the microstructure was observed. Based on the rock engineering systems (RES) theory, interactions among microscopic parameters were analysed, and the relationships between shear strength parameters and microscopic parameters of alkaline-contaminated red clay were established. Results show that both of the cohesion and friction angle of alkaline-contaminated red clay are increased in general; the adsorption in alumina production liquid and dispersing effect of 0.7% NaOH concentration are noticeable, and the interactions of the microscopic parameters are intense; the ratio of the intra-aggregate pore number, the probability distribution index and the number of particles can significantly influence cohesion; the particle morphology fractal dimension, aspect and probability entropy have a severe effect on friction angle. This work is expected to serve as a reference for future research on the relationship between macroscopic properties and microcosmic structure of soil.

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