Optimum Mixing Ratio Research Articles

Blended natural and synthetic coagulants for the COD and BOD removal from surface water; optimization by response surface methodology: The case of Gibe river

A novel wastewater treatment method is presented in this study. It combines natural coagulants derived from watermelon seeds with the commonly used synthetic coagulant alum. This research demonstrates a remarkable synergy between these two coagulants in removing nutrients from Gibe River wastewater. Combining natural and chemical coagulants often improves water treatment by enhancing particle destabilization, accelerating floc formation, and broadening the range of removable contaminants, resulting in lower chemical dosage requirements. The optimal mixing ratio, found to be 1 part watermelon seed coagulant to 3 parts alum, leads to improved treatment efficiency. At this ratio, the process achieves impressive removal rates: 98.26 % for total dissolved solids (TDS), 96.10 % for biochemical oxygen demand (BOD), and 95.26 % for chemical oxygen demand (COD). These findings not only validate the use of watermelon seeds as a coagulant but also highlight the combined approach's environmental and economic benefits. This integrated method offers a more sustainable and cost-effective solution for wastewater treatment.

Sustainable soil stabilization of expansive soil subgrades through lime-fly ash admixture

Expansive soils, known for their significant volume changes with moisture variation, pose severe challenges for construction and pavement integrity. This study investigates the stabilization of expansive subgrade soils using a lime-fly ash mixture, aiming to enhance engineering properties and reduce associated risks. Soil samples from Nashik, Maharashtra, India, were analyzed for their geotechnical properties, revealing high plasticity and expansive nature. The study utilized different proportions of lime-fly ash mixtures to assess improvements in the stabilized soils' Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). Laboratory tests, including granulometry, SEM, and XRF, indicated significant changes in the soil's physical and chemical composition. The stabilization process showed a marked reduction in the Free Swell Index (FSI) and swelling pressure attributed to flocculation. The optimum mix ratio of 1:4 (lime: fly ash) demonstrated the most substantial improvement, with UCS increasing to 224 kPa and CBR values reaching 8%. Additionally, the elastic modulus of the stabilized subgrade showed considerable enhancement, indicating better load-bearing capacity and durability. A flexible pavement design was implemented on both untreated and treated subgrades, demonstrating a 28% cost reduction for the stabilized section. This research underscores the effectiveness of using a sustainable lime-fly ash blend in mitigating the challenges posed by expansive soils, offering a cost-effective and environmentally friendly solution for road construction. The findings provide a robust framework for engineers to improve the stability and longevity of pavements on expansive soils.

The effects of processing parameters on the shape of particle size distribution and grinding rate in a stirred mill

The study of particle size distribution (PSD) of materials is a crucial aspect of mineral processing. It not only determines the appropriate beneficiation process and equipment but also has a significant impact on the grade and recovery of concentrate. This study utilizes a pin-stirred mill for the wet fine grinding of limonite to examine four different widths of PSD functions and compares their quantitative descriptions of the PSD. Skewness is a parameter introduced to quantitatively describe the asymmetry of the PSD. This study aims to investigate the effect of the stirrer speed, the density and the size of the grinding media on the shape of the PSD and on the grinding rate. The results show that a lower stirrer speed and a lower density of the grinding media result in a narrower and a more symmetrical PSD of the grinding products. Moreover, the time-dependent approach succeeds in simulating and proving the evolution behavior of the median particle size. It was found that the optimum mixing ratio of the grinding media can effectively adjust the shape of the PSD and improve the grinding efficiency.

Deposition morphology and mechanical properties of lean cemented gangue backfill material: Laboratory test and field application

Backfilling mining technology provides an efficient and environmentally-friendly solution for treating additional products (such as tailings, coal gangue and other solid waste) in coal mining process, which are filled into the underground goaf area, thus reducing surface subsidence, roof strata damage, and associated geological disasters. In this study, a novel backfill material called lean cemented gangue backfill material (LCGBM) is introduced, and various experiments, including uniaxial compression tests, creep tests, CT-SEM scanning and reconstruction are carried out to evaluate its mechanical properties and engineering practicability. The test results indicate that the strength and volume fraction of self-compacting cement (SCC) slurry and solid waste aggregate jointly control the uniaxial compressive strength and failure mode of LCGBM, reflecting the bucket effect under the influence of two components. Although the volume fraction of aggregate and SCC slurry is intentionally reduced to control the cost, this cemented granular material shows excellent compressive strength, overall stiffness and long-term bearing capacity in laboratory and field tests. In the process of engineering application, the uniaxial compressive strength of the LCGBM reaches 14 MPa, and the initial setting time is 120 s, which reduces the consumption of gangue aggregate by 35 % and greatly reduces the construction time. In addition, a calculation method of the optimal mixing ratio of raw materials is proposed, which can adjust the strength and volume fraction of SCC slurry according to the optimal mixing range, so as to maximize the utilization of the strength of LCGBM, and reduce the construction time and aggregate of backfilling. The research findings emphasize the potential of the LCGBM in promoting clean and sustainable coal mining practice.

Hazelnut Protein and Sodium Alginate Complex Coacervates: An Effective Tool for the Encapsulation of the Hydrophobic Polyphenol Quercetin.

For valorization purposes of hazelnut byproducts, complex coacervation of hazelnut protein isolate (HPI) with sodium alginate (NaAlg) was investigated by turbidimetric analysis and zeta potential determination as a function of pH and protein/alginate mixing ratio. HPI-NaAlg complex coacervates were used as an encapsulating material of quercetin (QE) at different concentrations. The optimal pH and mixing ratio resulting in the highest turbidity and neutral charge were 3.5 and 6:1, respectively. The coacervation yield was 74.9% in empty capsules and up to 90.0% in the presence of QE. Under optimal conditions, HPI-NaAlg complex coacervates achieved an encapsulation efficiency higher than 99% in all coacervate/QE formulations. Fourier transform infrared spectroscopy (FTIR) results revealed the occurrence of electrostatic interactions between different functional groups within the ternary complex in addition to hydrogen and hydrophobic interactions between QE and HPI. HPI-NaAlg complex coacervates can serve as an alternative matrix for the microencapsulation of bioactive ingredients with low water solubility in food formulations, which adds an additional valorization of hazelnut byproducts.

Optimized Design of Low-Carbon Mix Ratio for Non-Dominated Sorting Genetic Algorithm II Concrete Based on Genetic Algorithm-Improved Back Propagation.

In order to achieve low-carbon optimization in the intelligent mix ratio design of concrete materials, this work first constructs a concrete mix ratio database and performs a statistical characteristics analysis. Secondly, it employs a standard back propagation (BP) and a genetic algorithm-improved BP (GA-BP) to predict the concrete mix ratio. The NSGA-II algorithm is then used to optimize the mix ratio. Finally, the method's accuracy is validated through experiments. The study's results indicate that the statistical characteristics of the concrete mix ratio data show a wide distribution range and good representativeness. Compared to the standard BP, the fitting accuracies of each GA-BP set are improved by 4.9%, 0.3%, 16.7%, and 4.6%, respectively. According to the Fast Non-Dominated Sorting Genetic Algorithm II (NSGA-II) optimization for meeting C50 concrete strength requirements, the optimal concrete mix ratio is as follows: cement 331.3 kg/m3, sand 639.4 kg/m3, stone 1039 kg/m3, fly ash 56 kg/m3, water 153 kg/m3, and water-reducing agent 0.632 kg/m3. The 28-day compressive strength, material cost, and carbon emissions show relative errors of 2.1%, 0.6%, and 2.9%, respectively. Compared with commercial concrete of the same strength grade, costs and carbon emissions are reduced by 7.2% and 15.9%, respectively. The methodology used in this study not only significantly improves the accuracy of concrete design but also considers the carbon emissions involved in the concrete preparation process, reflecting the strength, economic, and environmental impacts of material design. Practitioners are encouraged to explore integrated low-carbon research that spans from material selection to structural optimization.

Improving the scour-resistance performance of for offshore wind turbines: Experimental and computational fluid dynamics studies on macro and micro characteristics

To enhance the resistance to local scour around offshore wind turbine monopiles, 15 mixtures were designed based on Response Surface Methodology (RSM). Cement content, sodium silicate content, and rubber powder content were selected as independent variables. After determining their flowability, the compressive strength and shear strength were measured after curing in pure water and artificial seawater for 3 days, 7 days, 14 days, and 28 days. Experimental results indicate significant improvement in the mechanical properties of the modified soil, including increased Unconfined Compressive Strength (UCS), internal friction angle, and cohesion. The optimal mix ratio is identified as CSR40–10–15, consisting of 40 % cement, 10 % sodium silicate, and 15 % rubber powder. The strength variation mechanism is elucidated from both macroscopic and microscopic perspectives. Finally, numerical simulations using Computational Fluid Dynamics (CFD) software validate the scour resistance performance based on the optimal mix ratio of flowable solidified soil, offering a new approach for local scour protection around offshore wind turbine monopile.

Design and Microwave Absorption Performance Study of SiC-Fe3O4 Emulsified Asphalt Mixture.

To address the challenges of slow curing speed and suboptimal microwave absorption during the paving of cold-mixed and cold-laid asphalt mixtures, this study introduces SiC-Fe3O4 composite material (SF) into emulsified asphalt mixtures to enhance microwave absorption and accelerate curing via microwave heating. Initially, based on the maximum density curve theory, an appropriate mineral aggregate gradation was designed, and the optimal ratio of emulsified asphalt mixture was determined through mixing tests, cohesion tests, wet wheel wear tests, and load wheel sand adhesion tests. Subsequently, the influence of SF content on the mixing performance of emulsified asphalt mixtures was analyzed through mixing and consistency tests. Finally, the microwave absorption performance of the mixture was evaluated by designing microwave heating tests under different conditions, using temperature indicators and quality indicators. The experimental results indicate that when SF content ranges from 0% to 4%, the mixing performance of the emulsified asphalt mixture meets specification requirements. The dosage of SF, SF composite ratio, and microwave power significantly impact microwave absorption performance, whereas environmental temperature has a relatively minor effect. The optimal mix ratio for the emulsified asphalt mixture is mineral aggregate:modified emulsified asphalt:water:cement = 100:12.8:6:1. The ideal SF dosage is 4%, with an optimal SiC to Fe3O4 composite ratio of 1:1, and a suitable microwave power range of 600-1000 W.

Predictive modelling of HHV and LHV for sugar industry by-products: a study on sugarcane trash leaves, bagasse, and filter cake

ABSTRACT This study aimed to enhance the efficiency of by-product raw materials from the sugar industry for use as fuel. The approach involved developing an equation to calculate the higher heating value (HHV) for each type of raw material using a regression method. Additionally, a simplex-centroid mixture design (SCMD) was employed to estimate the lower heating value (LHV) based on the mixing ratios by weight of sugarcane trash leaves (SCL), sugarcane bagasse (SCB), and filter cake (FTC). The results demonstrated that the developed model accurately estimated the HHV for each raw material. The ultimate analysis showed high statistical appropriateness, with an R2 of 0.83. The standard error of estimation was 0.74 MJ/kg, and the mean absolute error was 0.76%. Furthermore, the SCMD effectively estimated the LHV of the SCL, SCB, and FTC mixture ratios, achieving an R2 of 99.77%. The evaluation and validation of the prediction equation revealed a mean absolute error of 7.57% and a mean bias error of 6.31%. The findings of this study can be used to enhance the combustion efficiency of sugar industry by-products for use as fuel by selecting the optimal mixing ratio for each type of raw material.

Enhancing compressive strength of phosphogypsum-based geopolymer cement with five alkaline activator combinations

Phosphogypsum (PG) is a bulk industrial solid waste generated during phosphoric acid manufacturing. This study investigated a novel phosphogypsum-based geopolymer (PBG) cement through L16(45) orthogonal experiments. The impact of five alkaline activators, including Portland cement clinker (PCC), sulfate alumina cement clinker (SACC), aluminate cement (AC), magnesium oxide (MgO), and calcium oxide (CaO), on the performance of PBG cement was analyzed, and the optimal mix ratio was determined. Results indicate that all four alkaline activators, excluding CaO, can enhance unconfined compressive strength (UCS) of PBG cement. Factor index analysis revealed that an optimal composition comprising 4 % PCC, 6 % SACC, 2 % AC, and 4 % MgO yielded the highest 28-day UCS of 45.63 MPa. PBG cement primarily consists of dihydrate gypsum (CaSO4·2H2O), ettringite (Ca6(Al(OH)6)2(SO4)3(H2O)25.7), and polymers. Of these constituents, the polymers accounted for 61.9 wt% of the total composition and provided most of the strength. This study provided a new approach for making better use of waste PG.

Applicability and chemical mechanism of lightweight cement composite containing fly ash and sand for sustainable embankment

Lightweight embankment is an effective method for soft foundation treatment, while decreasing its cement usage can protect environment, save resource and reduce cost. This study aims to develop a lightweight cement composite (LC) containing fly ash and sand to provide guidance for filling the sustainable embankment. The chemical mechanism, micro-morphology, mechanical strength and workability of lightweight cement composites were evaluated through macro-micro tests, as well as life cycle assessment was performed to analyze the sustainability, and determine the optimal mixing ratio. The results showed that the moderate amount of fly ash was beneficial to enhance the mechanical strength of LC, while adding sand further improved its ductility, toughness, workability and sustainability. When the replacement rate of fly ash and sand were 10 % and 20 %, the energy absorption and fluidity of LC increased by 57 % and 7 %, and its ductility index, carbon emission and construction cost decreased by 34 %, 46 % and 35 %, respectively. Fly ash reacted with calcium hydroxide produced by cement hydration to generate more calcium silicate gels, which reduced the large pore of LC and improved its internal structure, while sand played a certain skeleton role.

Mechanical Properties and Microanalytical Study of Concrete Reinforced with Blended Corn Straw and Scrap Steel Fibers.

Fiber concrete exhibits superior performance in various aspects compared to plain concrete and has been widely researched and applied worldwide. However, many industrially made fibers are expensive, and their cost has to be considered before use; thus, it would be economically valuable to find inexpensive fibers with excellent properties to make fiber concrete. Rural areas have many rich straw resources to be disposed of; at the same time, the rapid development of the automobile industry has introduced a large number of used tires containing steel wire with a very low reuse rate. These two low-cost materials can be processed to make fibers, making the study of mechanical properties regarding their incorporation into concrete practically significant for reducing the cost of fiber concrete. Based on this, a three-factor, three-level orthogonal test was conducted to investigate the effects of different dosages of corn straw fibers and scrap steel fibers, as well as the water-cement ratio, on the mechanical properties of concrete. The optimum level of each factor for blended straw-waste-steel-fiber concrete with different mechanical properties was obtained using the polar and ANOVA methods. It was found that the compressive strength, splitting tensile strength, flexural strength, and impact resistance of the specimens after fiber dosing were better than those of plain concrete specimens with the same water-cement ratio. The maximum improvement was 14.96% in cubic compressive strength, 42.90% in tensile strength, and 16.30% in flexural strength, while the maximum improvement in impact energy consumption at the final crack was 228.03%. Combined with SEM microanalysis, the two fibers formed a stronger whole with the C-S-H gel. When the specimen was subjected to load, the two fibers were able to withstand part of the load, thus enhancing the load-bearing capacity. Finally, the optimal mix ratio of blended straw-scrap-steel-fiber concrete was determined to be 0.8% corn straw fibers by volume, 0.6% scrap steel fibers by volume, and a 0.45 water-cement ratio by combining the weights of the levels of each factor under its four different mechanical properties through hierarchical analysis. This analysis of mechanical properties provides a reference for practical applications in future projects.

Experimental study of the optimal mixing ratio of metallic additives for improving the performance of the solar activated carbon-methanol adsorption refrigeration system

An activated carbon–methanol system can run on low heat (70–100°C). Methanol is dependable and works well with activated carbon because of several benefits, including an appropriate latent heat of evaporation, a low freezing point, and negligible copper corrosion and steel at temperatures below 100 °C. An experimental study of the thermal performance by increasing the adsorption bed thermal conductivity was conducted. Using0 10 % 20 and %30 % of metallic copper powder with activated carbon to improve the bed thermal conductivity. A sample is prepared with 20 % copper powder to find out the improvement of heat transfer characteristics to the cooling effect. The temperature gradient has been tested with two flow rates to examine the coolant performance and increase. Solar energy can be effectively utilized based on low-grade temperature consumption in such systems. This work aims to make an experimental investigation of the thermal performance of an activated carbon-methanol adsorption refrigeration system to study the effect of the enhanced thermal conductivity of the adsorbing bed. Using 0 %, 10 %, 20 %, 30 % of metallic copper powder with activated carbon to enhance the thermal conductivity of the bed, providing a significant improvement in the system efficiency, specific cooling power (SCP), and coefficient of performance of adsorption cooling. It is found that copper filing with a mass concentration of 20 % are appeared the optimal ratio metallic additive to enhance the thermal performance of the system. Moreover, the effect of the hot water flow rate is studied. Results indicated that the addition of 20 % metallic copper filings to the activated carbon lowered the evaporator temperature to reach -5 and -10 °C for heating water flow rates 3 and 2 LPM, respectively. Also, the addition of copper filing enhances the cycle COP of the system by 49 % and 46 % at hot water flow rates of 2and 3 LPM, respectively. The highest cycle COP of the current system reached was 0.92 for the condition 20 % additives at 3 LPM hot water flow rate. Owning the feature of great solar energy availability and the long daily sunny hours, solar-powered adsorption cooling systems have promising potential applications in Egypt. A mathematical model of the system performance is also studied.

Co-pyrolysis behavior of municipal solid waste and food waste residue: A thermogravimetric study to discern synergistic effect

Effective solid waste disposal necessitates suitable combination and clean conversion technologies to maximize resource utilization. Thus, this study investigates the behavior of co-pyrolysis in municipal solid waste (MSW) and food waste (FW) via thermogravimetric analysis, aiming to discern synergistic effects and optimize waste to energy conversion. The impacts of heating rate and blending ratios were evaluated under an inert N2 atmosphere, within a temperature range of 30–900℃, during single and combined pyrolysis processes respectively. Results revealed slight variations in weight loss patterns and thermal decomposition behavior. When heating rate increased from 10 to 30℃.min−1, decomposition process delayed, resulting in higher initial (Ti), peak (TP), and final (Tf) temperatures due to inadequate heat transfer. As food waste increased, mass loss rose and favorable synergistic effect was observed at 20 % FW during medium temperatures, while other blends showed inhibitory effects. The pyrolytic index (D) rose nonlinearly from 6.29 × 10−7 to 7.72 × 10−7 with a higher FW proportion, peaking at 20 % FW, suggesting an optimal MSW and FW mixing ratio. This blend also exhibited the lowest activation energy, indicating a more efficient thermal decomposition process. Those outcomes offer crucial insights for optimizing co-pyrolysis systems and provide essential information for co-disposal of MSW and FW, potentially reducing pollutant emissions and enhancing waste to energy conversion.

NON-FIRED LATERITE SOIL BRICKS WITH NA-BASED STABILIZER ADDITION FOR SUSTAINABLE DEVELOPMENT

Fired bricks are widely used, but they are energy-intensive and non-eco-friendly. Non-fired bricks with chemical stabilisers can be the alternative solution, which is a low-energy-intensive and environmentally friendly manufacturing product. Laterite soil can be the raw material for the synthesis of non-fired clay brick in sodium hydroxide solution and sodium silicate solution. However, it may have been mixed with other laterite soils with different optimum moisture contents and grain sizes during extraction. Thus, the mixing ratio of laterite soil, Na-based stabilisers, and water for non-fired brick production is determined. Besides, two types of laterite soil, LAT 1 and LAT 2, from different locations were prepared, and another type of laterite soil, LAT 3, was prepared by mixing LAT 1 and LAT 2. Both three are compared primarily in terms of compressive strength and water absorption, which are mixed with the Na2SiO3/NaOH ratio. As a result, the new mixing ratio with increased water content was determined based on the optimum moisture content of the soil. Besides, the optimum mixing ratio of each type of brick was determined. Overall, based on the Malaysian standard, all types of brick samples from each ratio could be used as load-bearing class 1 and internal wall bricks. Additionally, LAT 2 and LAT 3-based bricks with a ratio of 1.5 Na2SiO3/NaOH ratio can be used as load-bearing brick class 2.

Gypsum-Enhanced Red Mud Composites: A Study on Strength, Durability, and Leaching Characteristics

The strong alkalinity of red mud and the heavy metals it contains pose a serious threat to the environment. This study investigated the possibility of applying red mud as a solid waste material in road construction to mitigate the problem of red mud accumulation. Red mud was modified using titanium gypsum and phosphogypsum as curing agents. The effects of varying gypsum types and mixing ratios on the mechanical properties and heavy metal leaching of the resulting red mud-based materials were assessed using percussion tests, unconfined compressive strength measurements, scanning electron microscopy (SEM), and continuous heavy metal leaching tests. The results showed that the optimal moisture content for titanium gypsum–cement-stabilized red mud (RTC) exceeds that of phosphogypsum–cement-stabilized red mud (RPC), with RTC exhibiting a lower maximum dry density compared to RPC. When the gypsum admixture was within 10%, the strength of the RPC was higher than that of the RTC at the same and curing time. The reticulation in RPC-10 was denser. The cumulative heavy metal releases from both RTC and RPC were within the permissible limits for Class III groundwater discharge standards. Based on the comprehensive test results, RPC is identified as the superior modified red mud material, with an optimal mix ratio of red mud/phosphogypsum/cement of 87:5:8.

Nutritional Evaluation of Almond Protein-Whey Protein Double System and Its Effect on Lipid Metabolism in HepG2 Cells

Almond protein (AP) and whey protein (WP) as single animal and plant proteins have certain limitations in nutrition, but the AP-WP dual protein can play a role in nutritional complementarity, and have a certain regulatory effect on lipid metabolism. This study investigated the amino acid composition of AP-WP system and its effect on FFA induced lipid metabolism in HepG2 cells. Results showed that, using the FAO/WHO model and whole egg protein model as reference values for essential amino acid content, the optimal mixing ratio of AP-WP was determined to be 3:5. The amino acid ratio coefficient scores under this ratio were 74.20 and 81.57 for the two models respectively. Additionally, this ratio of AP-WP showed the best antioxidant activity. The FT-IR spectroscopy indicated that there is interaction between AP and WP. The study found that AP-WP improved oxidative stress and lipid accumulation in HepG2 cells by reducing ROS and TG levels. Western blot analysis showed that AP-WP inhibits the expression of SREBP-1, FAS, and ACC, regulating lipid metabolism in HepG2 cells and leading to a certain lipid-lowering effect. The combination of almond protein and whey protein can improve the nutritional value of food and give full play to the physiological regulation of different proteins to promote human health. The research aims to lay the theoretical foundation for the application of double-protein system in the fields of nutritional food processing and lipid metabolism regulation.

Experimental study on the road performance of molybdenum tailings sand stabilized with cement and fly ash

The large accumulation of molybdenum tailings (MoT) has resulted in a series of hazards, including environmental pollution, damage to water resources, and increased risk of geological disasters. This study employs ordinary Portland cement (OPC) and fly ash (FA) stabilization of MoT sand and seeks the optimal mix ratio through experimentation. The strength properties of MoT sand stabilized with different proportions of OPC and FA are studied and analyzed through unconfined compressive strength tests, splitting tensile strength tests, and splitting rebound modulus tests. Additionally, the microstructure of MoT sand stabilized with OPC and FA is analyzed using scanning electron microscopy (SEM). The results indicate that with an increase in OPC content, the compressive strength, splitting tensile strength, and splitting rebound modulus all increase. With an increase in FA content, the compressive strength gradually increases, while the splitting tensile strength and splitting rebound modulus show a trend of initially increasing and then decreasing. The results show that the optimal mix proportion for OPC and FA-stabilized MoT sand is 7 % OPC content and 15 % FA content. This mixture is suitable for a heavy traffic base of expressways and class I highways, as well as for an extra heavy traffic base of class II and below highways. The research results can provide reference for using OPC and FA stabilized MoT sand as roadbed material.

Utilization of accelerated weathering of limestone captured carbon dioxide (CO2) with cement kiln dust to produce building material

The accelerated weathering of limestone (AWL) process is an inexpensive and eco-friendly carbon dioxide (CO2) capture process with comparable performance to amine-based systems. However, the generated calcium bicarbonate (Ca(HCO3)2) solution lacks an effective utilization alternative. Aside from that, the current solid waste utilization alternatives (i.e., carbon mineralization and partial replacement of conventional binders) lack the capability to effectively curb the tremendous production rate of solid waste (i.e., cement kiln dust (CKD)). To address both gaps, this study developed a novel Ca(HCO3)2 solution utilization alternative with CKD as the sole binder to produce a building material termed CKD-bicarbonate lime mortar (BLM). This work aims to identify the optimal mix ratio for CKD-BLM to achieve maximum compressive strength via a series of studies; (i) liquid medium, (ii) Ca(HCO3)2 solution volume, and (iii) sand:CKD mix ratio. From the findings, it was found that CKD-BLM at the optimal CKD:sand:Ca(HCO3)2 mix ratio of 1:0.45:0.29 exhibits the highest compressive strength of 2.09 MPa, surpassing the compressive strength standard of 1.70 MPa set by the ASTM C141 while having acceptable workability of 118 % which is within the standard workability range of 105–155 % set by ASTM C270. However, the CKD-BLM sample exhibits high leaching of Ca, Si, Na and Cl which does not meet the environmental regulation. This was resolved by applying a waterproof coating that effectively curbed the leaching by 28.84–99 %. Overall, this study successfully developed a building material with industrial wastes (i.e., Ca(HCO3)2 solution and CKD) that surpasses the performance of conventional lime mortar while utilizing up to 0.22 kg CO2.kg CKD-BLM_1:0.45:0.29−1.

A novel cement-based interface functional material for application onto shotcrete-rock interface of tunnel in cold regions

In cold regions, the “natural weak zone”+“frost heave cracking” problems at the interface between shotcrete and rock will superimpose damage to the shotcrete-surrounding rock support system structure. However, there is no direct and effective technique to improve the bond strength and frost resistance of shotcrete for infrastructure such as tunnels in cold regions. Based on this, this study innovatively proposes the pretreatment technology of the interface between shotcrete and surrounding rock in tunnels in cold regions, and tries to investigate the fracture evolution of the binary and the distribution characteristics of the interface transition zone (ITZ) in cold regions under the action of interface functional material (IFM) by relying on the techniques of mechanical strength test, morphology analysis, and microstructure test. The study showed that: (1) the optimal mix ratio of IFM was designed as cement (10)+water (4)+calcium acrylate(1.5 %)+bamboo liquefied binder (4 %)+acrylate laminating adhesive (8 %)+ICA (2 %). At room temperature, the shear strength of the binary sample pretreated with the IFM was elevated by 1.56 MPa compared with that of the normal sample, and this increase could be raised to 1.64 MPa under freeze-thaw cycles (FTC). (2) As the freeze-thaw effect intensifies, the number of sandstone particles adhering to the failure surface of the binary increases correspondingly, and the morphology of the failure surface also becomes more undulating. This is due to the fact that after a certain FTC, more cracks are deflected towards the sandstone side due to the higher degradation of the sandstone compared to the ITZ. (3) Under FTC, the application of IFM will lead to an increase in the proportion of sandstone adhering to the failure surface and the fractal dimension of the failure surface, and this phenomenon becomes more pronounced with the intensification of FTC. (4) In the ITZ space, the hydration products and pore structure of the area closer to the sandstone are worse, the use of IFM can optimize this phenomenon. The new idea of utilizing the surrounding rock surface pretreatment technology to improve the bond strength and frost resistance of shotcrete proposed in this study has good application prospects in the construction of tunnels and other infrastructures in cold regions.