Optimal Mixture Research Articles

Characterization and optimization of fresh and hardened properties of ultra-high performance geopolymer concrete

Due to the deterioration and environmental issues of cement-based ultra-high-performance concrete (UHPC), there is an increasing interest in utilizing geopolymer technology to develop UHPC. In this regard, a statistically based model using response surface methods is applied to predict the fresh and mechanical properties of ultra-high performance geopolymer concrete (UHPGC) mixtures. Twenty mixtures were designed and generated experimentally using the central composite design (CCD) concept. In this context, the effects of three principal factors—the effects of silica fume (SF), natural sand content, and different curing temperatures—on the flowability, setting times, bulk density, compressive, and flexural strengths were examined. The models presented herein reveal that all the inputs and outputs are perfectly correlated. Microscopic investigations were used to determine the morphological characteristics of the optimum mixture. The results revealed that the bulk density, flexural, and compressive strengths of the UHPGC ranged from 2461 to 2536 kg/m3, 6.48–9.39 MPa, and 104–152 MPa, respectively. According to the validated models and optimization findings, the optimum mixture of SF (22.5%) and sand content (1150 kg/m3) cured at 100 °C was found to develop the optimized UHPGC with the best microstructure performance. From the experimental results, the optimized UHPGC mixture possessed excellent mechanical properties (2521 kg/m3, 9.39 MPa and 152 MPa), and it had a non-porous structure primarily made of a dense geopolymer gel. Overall, the current study provides new insights into the design and production of UHPGC materials using the response surface method, which could contribute to the widespread use of this concrete in practical applications.

Exploration of Novel Antibacterial and Anti-adhesive Formulations from three Chemically Characterized Essential oils: Optimization using experimental design methodology

In this study, experimental design approach coupled with MIC assay were used to determine the combined treatment effect of three Moroccan essential oils (EOs) derived from Ammi visnaga (AVEO), Mentha suaveolens (MSEO) and Lavandula stoechas (LSEO), against S. aureus, E. coli and P. aeruginosa, as well as to predict the optimal formulations of these EOs to inhibit bacterial adhesion on the stainless steel (304L SS) surface. EOs were obtained via hydrodistillation and then, their volatile content was analyzed using Gas Chromatography-Mass Spectrometry (GC–MS). The antibacterial activity was evaluated using disc-diffusion, microdilution assays. Moreover, the anti-adhesive effect was assessed using two complementary methods, including contact angle measurements and scanning electron microscopy (SEM) analysis. The GC-MS analysis revealed the presence of various bioactive compounds in AVEO, MSEO and LSEO. The main identified components were piperitenone oxide (52.04%) and pulegone (19.78%) for MSEO; and camphor (23.97 %) and menthol (21.5%) for LSEO. Whereas, AVEO was mainly characterized by the presence of linalool (30.24 %). The antibacterial assays showed that all EOs are able to inhibit the bacterial growth at low concentration (MIC ranged from 0.015 to 4 v/v (%)). The optimization of mixtures antibacterial effect has demonstrated the synergistic effect between the three EOs. The optimal mixture predicted against E. coli, P. aeruginosa, and S. aureus corresponded to 30%/42%/28%, 50%/50%/0%, 43%/30%/27%, and AVEO, LSEO and MSEO, respectively. The contact angle assessment indicated that LSEO, MSEO, AVEO and their optimal mixtures remarkably inhibit bacterial adhesion by the alteration of the physico-chemical properties of 304L SS surface. These results are confirmed by SEM analysis, and proved that EOs formulation was able to inhibit more than 80% of bacterial adhesion to 304L SS surface. In light of these findings, EOs mixtures recommended here, can be applied as a promoting and eco-friendly agent for combating the formation of biofilms on stainless steel surface.

On mixtures as working fluids of air-cooled ORC bottoming power plants of gas turbines

The use of mixtures as working fluids of organic Rankine cycle (ORC) waste heat recovery (WHR) power plants has been proposed in the past to improve the matching between the temperature profile of the hot and the cold streams of condensers and evaporators, thus to possibly increase the energy conversion efficiency of the system. The goal of this study is to assess the benefits in terms of efficiency, environmental (GWP) and operational safety (flammability) that can be obtained by selecting optimal binary mixtures as working fluids of air-cooled ORC bottoming power plants of medium-capacity industrial gas turbines. Furthermore, two thermodynamic cycle configurations are analyzed, namely the simple recuperated cycle and the so-called split-cycle configurations. The benchmark case is a combined cycle power plant formed by an industrial gas turbine and an air-cooled recuperated ORC power unit with cyclopentane as the working fluid. The results of this study indicate that binary mixtures provide the designer with a wider choice of optimal working fluids, however, in the case of the recuperated-cycle configuration, no improvement in terms of combined cycle efficiency over the benchmark case can be achieved. The split-cycle configuration leads to an increase of combined cycle efficiency of the order of 1.5%, both in case of pure and blended working fluids. Furthermore, for this cycle configuration the use of Novec 649 as working fluid is advantageous because it is environmentally and operationally safe, and it does not involve any penalty in terms of combined cycle efficiency if compared to the benchmark case. Additionally, the use of this fluid would lead to a more compact turbine, as the corresponding thermodynamic cycle would determine a turbine volume flow ratio that is half of the value of the benchmark case and a specific enthalpy difference over the expansion that is one fifth.

Mechanical performance of geopolymer concrete with micro silica fume and waste steel lathe scraps

Environmental studies for solutions are among the most important agendas of the scientific world. Most of the new studies are taking into account environmental effects. However, it is interesting for the scientific world to find solutions for accumulated environmental problems, to reduce harmful production, and to turn wastes that cause environmental pollution into useful products. In addition to incorporating fly ash, a recognized environmentally friendly and sustainable material, geopolymer concrete, utilizes micro silica fume (micro silica) as a binding agent. Furthermore, waste lathe scraps are introduced to enhance and safeguard the concrete's mechanical properties. During the preparation phase, significant enhancements have been identified in the workability and setting time of concrete. A total of 16 test samples were prepared in this study. Micro silica of 0%, 5%, 10%, and 20%, and lathe scraps of 0%, 1%, 2%, and 3% were examined. Experimental findings revealed that incorporating 5% micro silica resulted in notable improvements in the compressive, flexural, and splitting tensile strengths, with the increases of 14.4%, 7.45%, and 6.18%, respectively. However, higher additions of 10% and 20% were found to decrease these strengths. In contrast, the inclusion of 1% lathe scraps led to considerable increases in the compressive, flexural, and splitting tensile strengths by 11.4%, 6.35%, and 8.23%, respectively. However, the addition of 2% and 3% lathe scraps resulted in the reduced capacity. The findings demonstrated that combining 5% micro silica with 1% lathe scraps provided the highest strength, with the improvements of 25.7%, 14.4%, and 12% in the compressive, flexural, and splitting tensile strengths, respectively. Considering the enhancements in the workability, setting time, and strengths observed in all the tests, the recommended optimal geopolymer mixture is 5% micro silica together with 1% lathe scraps.

Response surface methodology-based characterization and optimization of fibre reinforced cemented tailings backfill with Slag

ABSTRACT With the increasing depths of underground mines due to the scarcity of near-surface ores, the introduction of fibre-reinforced cemented paste backfill (F-CPB) has emerged as a novel solution to address the demanding geomechanical conditions in deep mining operations. However, the widespread adoption of F-CPB in mining and industrial backfill operations necessitates a comprehensive understanding of its key engineering properties, including strength, yield stress, modulus of elasticity, and cost. Moreover, it is crucial to investigate the influence of the constituent materials (water, fibres, binders, tailings) and their interactions on these properties. This research paper presents the application of response surface methodology (RSM) to model the effects of binder content (Portland cement/Slag), water content, fibre content, tailings and their interactions on the mechanical and rheological properties, as well as the cost of F-CPB. Central Composite Design (CCD) experiments were conducted, and a high degree of agreement was observed between the experimental and predicted responses. The RSM approach proves suitable for accurately estimating the responses and assessing the interactions between the model parameters and the properties of F-CPB. Furthermore, a combination of RSM and the desirability approach enables the development of an optimisation tool for F-CPB, facilitating the formulation of optimal backfill mixtures. The results obtained from this study highlight the effectiveness of the combined RSM and desirability approach in F-CPB mix proportioning, offering an advanced engineering approach to F-CPB mix design. The proposed design method has the potential to reduce the laboratory testing protocol required for determining the optimal mix composition.

Mechanical properties and microstructure of red mud-coal metakaolin geopolymer concrete based on orthogonal tests

Red mud, an industrial solid waste, can be used as a raw material for geopolymer concrete to reduce its environmental damage and achieve resource utilization. Nonetheless, the performance of red mud-based geopolymer concrete is influenced by various factors, and its overall sustainability remains to be comprehensively evaluated, limiting its widespread application. For this reason, this study systematically investigated the effects of water-binder ratio, aggregate-binder ratio, curing conditions, and Na2O/H2O on the water absorption, mechanical properties, and efflorescence degree of geopolymer concrete using Taguchi's orthogonal method. The optimal mixture for maximization of mechanical properties was determined using Design-Expert software. Subsequently, the microscopic properties of the samples were evaluated. In addition, an AHP-CRITIC-TOPSIS model was used to construct a sustainable assessment framework for geopolymer concrete including environmental, social, and economic indicators. The results indicated that the water-binder ratio is the main influencing factor. Excessive water increases the length of interfacial transition zone, coarsens the pore structure, and hinders the condensation process, leading to a degradation of material properties. In terms of sustainability, both M30 and M40 grade geopolymer concretes obtained significantly higher scores than cement concrete, and therefore it is considered a greener alternative.

Stabilization of dune sand using crushed sand, silt and blast furnace slag for use in road field

Soil stabilization is a well-known technique to improve the mechanical properties of soils in road and railway construction by adding a grading corrector and/or hydraulic binders in the soil. In this work, dune treated sand is proposed to be used in pavement layers. For this, a series of tests, including sieve analysis, Proctor compaction, CBR, simple compressive strength, shear strength and compressibility tests are performed to evaluate the effectiveness of the adopted stabilization technique using dune sand, and to determine the optimal mixture for practical purpose. Our results show that for certain mixtures the lift (the CBR index) increases from ∼8% to ∼78% with the increase in resistance.

Enhancing Methane Production through Anaerobic Co-Digestion of Sewage Sludge: A Modified ADM1 Model Approach

The International Water Association’s (IWA) established Anaerobic Digestion Model No. 1 (ADM1) was created to serve as a backup for experimental findings regarding the actual anaerobic digestion process. The previous model idea was adjusted and used to simulate an anaerobic digestion process in this study. Testing procedures, such as benchmark tests and balance checks, were performed in order to verify the accuracy of the implementation. These measures worked in tandem to ensure that the model was implemented flawlessly and without inconsistencies. The primary objective of this article is to construct a method that is based on the ADM1 for evaluating co-digestion and predicting the performance of the digestion process or methane yield based on the analyzed substrates’ physicochemical properties. Additional equations and simulations have been added to the standard model to create tools for evaluating the feasibility of anaerobic co-digestion. The study’s two most intriguing aspects are the optimal mixture and parameter dependence. The adjusted ADM1 is accurate in predicting the measured values of effluent COD, pH, methane, and produced biogas flows with a reasonable degree of accuracy, according to the validation results. This research shows how to use ADM1 in a wastewater treatment plant and other settings where anaerobic digestion is of interest.

Enhancing the mechanical and environmental performance of engineered cementitious composite with metakaolin, silica fume, and graphene nanoplatelets

Engineering cementitious composites are designed to offer high ductility, enhanced strength, and enhanced impact resistance as rehabilitation materials for various support structures and equipment. ECC is an inventive material for construction with tensile strain hardened properties and multiple fracture behaviors, which is highly encouraged in the construction industry. The objective of this study was to create an eco-efficient engineered cementitious composite (ECC) with binary systems of cement with metakaolin (MK) and silica fume (SF) and an optimized dosage of graphene nanoplatelets (GNPs). To optimize mixture proportion, an experimental design was developed using the response surface method. We analyzed the compressive strength, split tensile strength, flexural strength, dried density, embodied carbon, and eco-strength efficiency of the optimal mixture proportion to determine its mechanical properties and low-carbon footprint. Results analysis showed a total of 10% content of SF and MK is optimum for an eco-friendly (low carbon profile) and mechanically strong ECC mixture. If it exceeds 10%, the mechanical strength of the composite decreases. Furthermore, 0.02%to 0.03% GNP concentration improved mechanical characteristics even further. According to the results of the multi-objective optimization, the optimal values for the variables Mk, SF, and GNPs are 9.19%, 4.83%, and 0.03%, respectively.

Exploring the Feasibility of Using Recycled PET Strips with Palm Leaf Ash for Sustainable Soil Stabilization

This research paper addresses the urgent environmental concern of waste management by focusing on sustainable consumption by utilizing waste plastic and palm leaves to stabilize soil in geotechnical engineering. The study examines the impact of incorporating recycled polyethylene terephthalate (PET) strips and palm leaf ash (PLA) into clayey sand to enhance its engineering properties. The investigation involved mixing varying proportions of recycled PET strips (10 mm, 20 mm, and 30 mm in length) with clayey sand, ranging from 0% to 2% by weight of the soil with a 0.5% increment for PET strips. Similarly, PLA was mixed with the clayey sand at proportions ranging from 0% to 12% by weight of the soil with a 3% increment. The strength parameters of lateritic soil were analyzed through the execution of unconfined compressive strength (UCS), triaxial, and California bearing ratio (CBR) tests. The optimum mixture was determined to be 2% recycled PET strips with a length of 30 mm and 12% PLA by weight of the soil. This specific combination exhibited significantly improved strength parameters for the lateritic soil, highlighting its potential for sustainable soil stabilization in geotechnical applications.

D-OPTIMAL MIXTURE DESIGN: OPTIMIZATION, FORMULATION, AND EVALUATION OF BIOSYNTHESIS NANOGOLD GELS

Objective: The aim of this research is the Optimization, formulation, and evaluation of biosynthesis nanogold gels by using experimental design. Investigations were provided to optimize the biosynthesis of nanogold gels on a compound of two gelling agents and develop the biosynthesis of nanogold gels. Methods: The optimization of the formula of gels utilizing the D Optimum Mixture Design method to discover the optimum result with the ratio of carbopol (X1) and hydroxypropyl methylcellulose/HPMC (X2) as a gelling agent and responses in the form were particle size (Y1), zeta potential (Y2) and spreading capacity (Y3). The 8-run formula assessed the impact of carbopol (X1) and HPMC (X2). Results: The ANOVA results for particle size showed that the model is highly statistically significant (P<0.05). Both Carbopol and HPMC coefficients enhanced the particle size (+118.91 and+594.73). The interaction of Carbopol with HPMC has increased the particle size (+441.73). The HPMC has the most dominant effect in increasing the particle size, and exchanging the two gelling agents will increase the particle size. Both Carbopol and HPMC coefficients are negative (-7.94 and-10.96), which means that these components contribute to a decrease in the zeta potential. The interaction of Carbopol with HPMC does not affect both increasing or decreasing the zeta potential HPMC has the most dominant effect in reducing the zeta potential, and the exchange of the two gelling agents will not increase and decrease the zeta potential. Carbopol and HPMC coefficients are positive (+6.41 and+4.58), meaning these components enhance the spreading capacity. The interaction of Carbopol with HPMC has decreased (-1.58). The prediction value was obtained from a solution that has the highest desirability. The chosen desirability of certain balances was 0.572. Conclusion: This study has shown that a well-balanced mixture of matrix ingredients could improve nanogold biosynthesis gel. Optimization was possible by applying D optimal mixture design, which confirmed efficiency in designing the nanoparticles gels of gold dosage forms.

Formulation of pasta enriched with protein-rich lupine (Lupinus mutabilis Sweet) and wheat bran using mixture design approach.

In recent years, as awareness of healthy diets has increased, consumers are becoming more aware of their food and are paying more attention to their diet. Nutritionists have recommended an increased consumption of dietary fiber in the daily diet to improve health. Within this context, this work aims to formulate "spaghetti" pasta enriched with lupin flour and wheat bran. For the formulation of the mixture of those flours, we used the NemrodW software to predict the optimal pasta formula. A physicochemical characterization, as well as the culinary quality of the pasta resulting from the different mixtures, was carried out to model each significant criterion and choose the optimal mixture that will be used in the pasta recipe. The evaluation of the physicochemical characteristics of the pasta showed that the addition of lupin flour and bran resulted in an improvement in the nutritional value of the enriched spaghetti. Following the results obtained, the software proposed an optimal mix and will be used for further study. This formula comprises 19.60% bran, 27.83% lupin flour, and 52.75% durum wheat semolina. The caloric value of the dough from the optimal mix was determined and compared to that of the standard dough. The results of our study indicated a significant improvement in the nutritional value of the enriched pasta compared to the standard pasta. The enriched pasta contained higher levels of protein, ash, lipids, polyphenols, and pigments and lower levels of sugars, which make it a more nutritious option for certain individuals, such as athletes or those following a protein or low-sugar diet. PRACTICAL APPLICATION: The proposed method of substituting wheat semolina with lupine flour and wheat bran in spaghetti formulation has demonstrated a potential for producing protein-rich and nutritionally enriched pasta. This approach can be useful for developing similar functional food products that cater to the dietary requirements of athletes or individuals following a protein or low-sugar diet.

Investigation on blending characteristics in asphalt mixtures with recycled asphalt and waste cooking oil as rejuvenator

ABSTRACT Reclaimed asphalt pavement (RAP) mixtures reduces environmental burden by utilising existing pavement material. However, RAP percent is limited due to performance issues at higher RAP content due to improper blending. The degree of blending can be improved using rejuvenator. Waste cooking oil (WCO) is gaining attention as a potential rejuvenator in recycled mixtures. However, past studies have shown contradictory results on WCO influence in asphalt mixture and have not investigated the influence of WCO on blending. This study is devised with a methodological approach to investigate the influence of WCO on blending in asphalt mixtures. Four blending approaches were formulated with four RAP and WCO contents resulting in a total of 148 mixture combinations. The blending characteristics were evaluated by assessing the workability and moisture damage resistance. The optimum mixtures were determined by Grey relational analysis, which were further investigated. The results showed the WCO doses determined from blending equation resulted in the higher dose than optimum WCO. The mixtures with medium dose and dry mixing of WCO showed the highest resistance to moisture damage. Further, for utilising higher than 30% RAP, higher binder content is required as compared to conventional mixture to increase the functional binder in the mixture.

Development of a functional beverage based on fermented whey, goldenberry (Physalis peruviana L.), and tumbo (Passiflora mollissima)

This study aimed to develop a beverage with functional and nutritional properties based on fermented whey and Andean fruit juices by using a simple-lattice mixture desing. The used proportions varied from 0.5 to 0.8 fermented whey, and from 0.1 to 0.4 for goldenberry (Physalis peruviana L.) and tumbo (Passiflora mollissima) juices, respectively. The influence of the mixture was analyzed on physicochemical and sensorial properties of beverages. It was evaluated that beverages contained protein, fat and acidity up to 1.92, 0.25, and 2.15%, respectively. Furthermore, the maximum bioactive compounds content was 343.54x10-5 kg(GA) kg-1 (total phenolics), 0.52x10-3 kg (CE) kg-1 (total flavonoids), 65.41x10-5 kg(AA) L-1 (Vitamin C), and 105x10-3 kg(Trolox) kg-1 (antioxidant capacity). Regarding sensorial evaluation results, the beverage with 55% fermented whey, 30% goldenberry juice, and 15% tumbo juice showed the best scores in taste regarding taste, colour and overall acceptability. It was observed that an increase in the percentage of fermented whey above 60% has negative effects, on the contrary, an increase in the percentage of goldenberry juice has a positive effect on sensorial properties. Finally, by optimization of both protein content and overall acceptability, the formulation with 50% fermented whey, 40% goldenberry juice, and 10% tumbo juice was the optimal mixture. Therefore, fermented whey, goldenberry, and tumbo juices can be used to obtain a beverage with high nutritional and functional value.

Effect of chitosan bio-polymer stabilization on the mechanical and dynamic characteristics of marl soils

The strength of marl soils decreases drastically in the variation of the water content. This has caused such soil to be introduced as problematic soil in geotechnical projects. In the present study, the effect of chitosan biopolymer on the static and dynamic properties of marl soil was investigated. To this end, different amounts of chitosan (up to 0.16%) were mixed with marl soil. Then samples were cured for 7, 28 and 90 days and finally subjected to 0, 1, 4 and 8Freeze-Thaw (F-T) cycles. Unconfined compressive strength (UCS), direct shear, Ultrasonic Pulse Velocity (UPV) and bender element tests were performed on the samples. The results showed that the UCS of the samples stabilized with 0.16% chitosan (as the optimal composition) increased by 227% after 7 days compared to that of unstabilized soil. Moreover, the values of cohesion and internal friction angle for the optimum mixture after 7 days of curing were equal to 38.76 kPa and 21.07°, which was much higher than 21 kPa and 18.26° related to the unstabilized marl soil. Chitosan was able to increase dynamic characteristics such as shear wave velocity and maximum shear modulus of samples by about 51 and 128% after 7 days of curing even after 8F-T cycles compared to those of unstabilized samples. Finally, chitosan exhibited that it can be a suitable alternative to traditional additives as an environmentally-friendly material, as confirmed by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses.

Research on Water Stability and Crack Resistance of Waste Cellulose Acetate–Reinforced Asphalt Mixtures Based on Response-Surface Methodology

The objective of this study was to explore the engineering application potential of waste cigarette butts and to investigate the effect of waste cellulose acetate (WCA) as reinforcement material on the performance of asphalt mixtures. A performance prediction model was also constructed to explore the optimal mixture preparation scheme. In this study, a scanning electron microscope (SEM) was used to visually characterize the surface morphology of WCA. The elemental composition of the cellulose surface was determined semiquantitatively using an energy dispersive spectrometer (EDS). The experimental design was carried out following the face-centered central composite design (FCCD) of the response-surface methodology (RSM), taking WCA shearing time, WCA content, and asphalt-aggregate ratio as variable factors, and the splitting strength (Rdry), freeze–thaw splitting strength (Rsaturated), and tensile strength ratio (TSR) of the mixtures as response variables. The software Design-Expert was adopted to construct and optimize the model under multiple responses. The road performance was verified by rutting test, low-temperature bending test, and water immersion Marshall test. The results showed that WCA is a kind of organic cellulose with a smooth surface and cloverlike cross section, which can significantly improve the mixture’s crack resistance and water stability. The performance prediction models all achieved a fit of 90% or higher. The best parameters recommended by Design-Expert were WCA content of 0.201%, WCA shearing time of 11.847 min, and asphalt-aggregate ratio of 5.683%, and the WCA-reinforced asphalt mixture Rdry, Rsaturated, and TSR values were 1.38 MPa, 1.24 MPa, and 89.86%, respectively, all of which were within the 95% prediction interval of the model predicted values. In addition, the road performance tests showed that WCA significantly improved the mixture’s flexural strength and water stability, but harmed the high-temperature rutting resistance. WCA has a significant reinforcing effect on asphalt mixture, which has a certain reference value for recycling waste cigarette butts and developing green road materials. In addition, the FCCD model has high accuracy and can effectively guide the road material preparation process.

Development of a novel ultra-high performance concrete (UHPC) suitable for underwater operation: Design and performance evaluation

This study has developed a new type of ultra-high performance concrete (UHPC) with excellent performance that can be used for underwater operations. Firstly, the sulfur aluminate cement(C S‾ A)-gypsum(CS‾)-silicate cement(OPC) ternary system is used as the cementitious material, and the optimal mixture ratio of underwater non-dispersive ultra-high performance concrete (UN-UHPC) is designed by the D-optimal design method. Then, the macroscopic properties, hydration process, and microscopic structure of the developed UHPC are evaluated. The experimental results show that UN-UHPC has excellent performance and good anti-dispersion properties, with a cement loss rate of 4.8% and a total porosity of 3.39%. Besides, due to the incremental effect of water, UN-UHPC has better mechanical properties and lower porosity than the one formed on land. In general, the developed UN-UHPC in this study further demonstrates the excellence and feasibility of D-optimal design in advanced building materials area and provides technical support for rapid underwater repair projects and the development of ocean resources.

Effect of low-calcium fly ash inclusion on long-term mechanical properties and durability of ground granulated blast furnace slag-based cement-free mortars

The present study focused on fabricating cement-free mortar based on ground granulated blast furnace slag incorporating low-calcium fly ash as precursors in an alkaline solution of sodium hydroxide and sodium silicate. The main purposes of the study were not only to find the optimum mixture proportions to confirm the fly ash role in contributing to the long-term mechanical properties and durability but also to expand the use of fly ash in cement-free binders based on ground granulated blast furnace slag. The ground granulated blast furnace slag was replaced with fly ash in the cement-free mortar at various levels of 30, 40, 50, 60, and 70% by mass. The cement-based sample as a control sample was prepared for comparison purposes. Results showed that the cement-free mortar samples with fly ash had the more superior long-term mechanical properties (i.e. flexural and compressive strengths and volumetric compaction via ultrasonic pulse velocity test) and durability (i.e. total charge passed via rapid chloride penetration test and sulfate resistance via length change of samples exposed to sulfate solution), lower water absorption and porosity, and denser microstructure than the control sample up to 120 days. The 40% replacement of ground granulated blast furnace slag by fly ash as an auxiliary source of alumina and silica was the optimum ratio in enhancing the long-term mechanical properties and durability of the cement-free mortar samples, which is in agreement with reducing the porosity and water absorption. The results of the environmental analysis indicate that using cement-free mortar samples has much lower environmental impacts. The cement-free mortar sample using 60% ground granulated blast furnace slag and 40% fly ash is found as an optimal mixture in terms of technical and environmental features.

Synergistic behavioral antagonists of a sex pheromone reduce reproduction of invasive sea lamprey

Sex pheromones impart maximal attraction when their components are present at optimal ratios that confer balanced olfactory inputs in potential mates. Altering ratios or adding pheromone analogs to optimal mixtures may disrupt balanced olfactory antagonism and result in reduced attraction, however, tests in natural populations are lacking. We tested this hypothesis in sea lamprey (Petromyzon marinus), a fish whose male sex pheromone attracts females when two critical components, 3-keto petromyzonol sulfate (3kPZS) and petromyzonol sulfate (PZS), are present at certain ratios. Here, we report a pheromone analog, petromyzonol tetrasulfate (3sPZS), reduced female attraction to 3kPZS but not to PZS. 3sPZS mixed with additional PZS synergistically disrupted female attraction to the male pheromone and reduced spawning by 97% in a high-density population. Our results provide evidence of balanced olfactory antagonism in a vertebrate and establish a tactic to disrupt spawning of sea lamprey, a destructive invader of the Laurentian Great Lakes.

Performance prediction and design of CO2 mixtures with the PR-VDW model and molecular groups for the transcritical power cycle

Nowadays, CO2 mixture has been widely considered as the working fluid of power cycle. However, how to select appropriate fluid from the numerous organic fluids has to be solved, so as to achieve the high-efficient power cycle. Thus, in this work, PR-VDW and GCM-PR-VDW models are respectively developed to predict the properties of CO2 mixture. Under the given operating conditions, the prediction deviations of cycle performance are obtained and the influences of cycle temperature, pressure and mixing ratio on prediction accuracy are explored. The results show that PR-VDW model has high prediction accuracy for the thermal properties and cycle performance of CO2 mixtures. The prediction deviations of cycle efficiency and net work are 11.38% and 6.88%, respectively. For the GCM-PR-VDW model, cycle efficiency and net work have deviations 15.65% and 8.65%, respectively. On this basis, with the maximum output power as the optimization objective, the optimal organic working fluid and its ratio in CO2 mixture are determined by employing GCM-PR-VDW model. Under the given heat source conditions, it is found that CO2+R32 (0.23/0.78, molar ratio) is the optimal mixture for the transcritical power cycle, and the corresponding cycle efficiency and net work are 16.48% and 1148.04 kW, respectively.