Cleaner Materials最新文献

Reduction of CO₂ emissions and plastic waste are the main environmental problems that modern society is dealing with. Concrete industry is continuously investing in research and development aimed at producing sustainable cementitious materials. In the last decades, it has gained interest the possibility of reusing polymer waste (mainly PET or PP) in partial substitution of natural constituents (aggregates) or as fiber reinforcement. As a matter of fact, because of the poor mechanical characteristic of polymers compared to the one of natural aggregates, the final cementitious composite has reduced mechanical performance. In the aforesaid framework, the experimental research reported in this paper aims at verifying the feasibility of a pathway able to use fine polymer particles, in detail a Polyester resin (PE resin) which is a waste product of the coating industry, as a partial replacement of sand and, in case, of binder particles, upon a gamma irradiation process similar to the one used for the sanification of containers in food industry, also their effectiveness in performing as seeds of the cement hydration. Firstly, intrigued by a study performed by MIT researchers (in which exposure of PET waste particles to gamma irradiation has been investigated as a method to improve their mechanical performance), the influence of different gamma irradiation dosages (10 kGy or 100 kGy) on PE resin particles was investigated. However, results led to the conclusion that, even with a mere 5% by volume substitution of Portland Limestone Cement (PLC) in the mix, the process does not significantly improve the mechanical performance of cement-based composites. In a second stage, the non-irradiated particles have been employed as a replacement of the binder and/or of the sand at different volume replacement ratios (10% and 20% respectively) in mortar mix designs formulated from typical Self-Compacting Concrete (SCC) mixes. Finally, once identified the most suitable type and level of replacement as the best compromise between performance maintenance and volume of added particles, the scaling up to the concrete mix-design has been performed and the related performance thoroughly tested. The results have provided limited reduction in mechanical properties, with a 20% by volume level of substitution of cement by PE resin particles, highlighting the possibility of reusing economically viable quantities of PE resins into concrete while still being able to use the material for structural application.

High-performance ternary mixed nano-concrete has been extensively utilized in high-rise structures due to its desirable strength, durability, and thermal insulation ability. Additionally, nano-concrete usage is the most current area of research in concrete components. This research investigates the compressive strength, flexural behavior, and micro-structure behavior of nano-SiO₂ concrete specimens. This study also evaluates the strength development of mixes combining binary and ternary combinations of agricultural by-products (rice husk ash, corncob ash, and bagasse ash) and industrial by-products (fly ash, ground granulated blast furnace slag, and metakaolin). The cost-efficiency, energy-efficiency, and eco-efficiency of ternary blended nano-concrete with various additives were considered when evaluating their sustainability capabilities. This study aims to improve sustainable high-performance concrete without overutilizing or underutilizing additives. Based on the findings, nano-SiO₂ concrete can achieve greater compressive strength ranges of 51 to 70 MPa with binary and ternary admixtures. Furthermore, ternary nano-SiO₂ concrete performs more sustainably than other mixes regarding cost-effectiveness, energy use, and CO₂ emissions, as do mixes made of sugarcane bagasse ash and ground granulated blast furnace slag.

This study focuses on treating Acid Mine Drainage (AMD) using Recycled Concrete Aggregate (RCA) as a cost-effective and environmentally friendly material. RCA is utilized, considering its availability at low cost, to reduce heavy metal and sulfate concentration in AMD and neutralize its acidity in batch experimental mode. To that end, the adsorptive properties of RCA were characterized before and after adsorption by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), elemental mapping, Brunauer-Emmett-Teller (BET) surface area measurements, and X-ray Diffraction. Furthermore, the organic functional groups of the tested materials were identified by Fourier Transform Infrared Spectroscopy (FT-IR). Adsorption parameters such as dosage, contact time, the grain size distribution of adsorbent particles, and the solution pH, were optimized for enhancing the removal performance. The pH point of zero charges for the RCA sample was defined. The results revealed that RCA is a potential eco-friendly material for AMD treatment. The concentration of sulfate in the tested AMD water was reduced by approximately 84%, while that of the metal elements declined as follows: iron 100%, manganese 95%, copper 66%, zinc 97%, and lead 76%. Also, the pH value of AMD water increased rapidly and reached neutral by using small quantities of RCA (≤1g/L).

Stabilization of flexible pavement layers using geogrids to improve the mechanical response of pavement layers is gaining importance over conventional stabilization techniques due to their low cost and superior performance. However, the lack of experimental data on quantifying the design input parameters of stabilized subgrades or granular layers limits the extensive use of geogrids in the field. Evaluation of design input parameters such as modulus improvement factor (MIF) or layer coefficient ratio (LCR) would promote the use of geogrids in the pavement, reducing the consumption of natural aggregates and the overall project cost. This study attempts to evaluate MIF and LCR due to geogrid stabilized soft subgrades considering different scenarios. All possible combinations of stabilization of pavement layers using biaxial and triaxial geogrids were considered. This involved stabilization of (a) the subgrade layer alone, (b) base layer alone, and (c) subgrade, subbase, and base layers. Accordingly, an extensive, systematic experimental program consisting of eighteen large-scale model pavement experiments (LSMPE) were conducted in five categories (designated as Series I through V). The stabilization of subgrade and granular layers was carried out using commercially available biaxial (BX1 and BX2) and triaxial (TX1) geogrids overlying soft and moderate subgrades with California bearing ratio (CBR) equal to 2.5 and 4%. Test results showed that stabilized subgrade prepared with existing and prepared subgrade material in conjunction with geogrid improved the effective CBR to as high as 10.9% from effective CBR = 7% corresponding to existing and prepared subgrade material without geogrid. The design inputs of geogrids (BX1/BX2/TX1) stabilized granular layers resulted in the MIF and LCR values ranging from 1.9 to 2.8 and 1.31 to 1.63, respectively, for the tested configuration considered in the study. Based on the findings of the study, inputs on resilient modulus of pavement layers were recommended for similar reinforcement and subgrade conditions considered.

The main objective of this study is to review the applicability of rapeseed straw (RSS) as a sustainable filler material in polylactic acid (PLA)-based biocomposites. The effect of different RSS particle sizes and concentrations (0–20 wt%) on the mechanical, morphological, thermal, and water absorption properties was investigated. The composites were fabricated by melt compounding using a twin-screw extruder followed by injection molding. The mechanical properties were analyzed through tensile and flexural tests and Charpy impact tests. The morphology of the samples was investigated by scanning electron microscopy (SEM). The thermal properties and the crystallinity of the composites were determined through differential scanning calorimetry (DSC). Mechanical properties revealed an increasing stiffness of PLA as a function of RSS loading, albeit at the cost of strength. SEM images have shown a limited interfacial adhesion between PLA and the straw, which was suggested to be responsible for the decreased strength values. Based on the DSC measurements, the RSS fibers facilitated the nucleation in the composites, thereby decreasing the cold crystallization temperature of PLA. The conducted experiments demonstrated that environmentally friendly and economically attractive biocomposites can be fabricated by substituting part of the PLA with RSS as a lignocellulosic by-product.

Se nanoparticles (NPs) with smaller size often exhibit higher antibacterial activity, thus size control of Se NPs is important to develop its application in the antibacterial field. In this study, Se NPs loaded attapulgite (APT) nanocomposites (Se/APT) were successfully prepared by a one-pot green method mediated by Aloe vera leaf extract, for which APT acts as a support to anchor Se NPs leading to the formation of small-sized and dispersed Se NPs. Structure characterization showed that the well-crystalline Se NPs with a size range of 1 ∼ 3 nm were uniformly distributed on the surface of APT nanorods. Antibacterial activities of the Se/APT nanocomposites were examined against S. aureus, and the result showed that the higher the Se loadings, the better the antibacterial activities of the nanocomposites, and the minimum inhibitory concentration of Se/APT-40% nanocomposite was up to 0.5 mg/mL. In addition, the green-synthesized nanocomposites have little cytotoxicity on mouse fibroblast cell L-929, and conversely promoted the growth and proliferation of the cells. The nanocomposites are expected to be candidates used in various antibacterial fields for preventing infections induced by S. aureus, such as suppuration of the wound.

The Government of Mauritius has come up with new regulations in an attempt to ban the use of petroleum based plastics bags so as to protect the environment. Hence it is important to find substitute materials to achieve this goal set by the government. Interestingly though, Mauritius being an island with a large Exclusive Economic Zone (EEZ), there is an abundancy of seaweeds, which is an interesting avenue to explore. The unexploited seaweed in the waters surrounding Mauritius remains a remarkably potential raw material for the manufacture of an alternative to petro-plastics, especially polypropylene non-woven bags, in the form of reusable and fully biodegradable bioplastic bags. This research attempts to investigate the use of algae, mainly Gracilaria Salicornia and Ulva lactuca as a potential; raw material for the production of reusable bioplastic bags through Taguchi optimisation method for the culling of optimum constituent wt.%. For the preparation of the biofilm to be solution casted, cassava starch, algae powder, glycerol and acetic acid were selected as controllable factors. The Taguchi L9 orthogonal array experimental design plan was considered for carrying out the experiments. The responses analysed were the tensile strength, water absorption, biodegradation and water vapour permeability. A maximum tensile strength and degradation of 7.325 MPa and 91.32% respectively were achieved from Taguchi optimal conditions. A maximum water absorption and minimum water vapour permeability of 60.3 % and 3.0181 g/h.m² respectively were evaluated from the experiments. Contribution of factors to the responses were determined through analysis of variance. Furthermore, regression models and contour plots were developed for predicting the best combination which was determined to be 8 % (w/v) starch, 3 % (w/v) algae, 1 % (w/v) glycerol and 8 % (w/v) acetic. An Ulva lactuca blend was experimented to act as substitute for cassava starch, achieving a tensile strength and water absorption of 3.578 MPa and 175.0 % respectively. Compared to other materials, used for bag production, available on the market, the mechanical properties of the developed algae-based material showed its potential as a replacement with some having much higher tensile strength confirming its successful usage.

This paper presents an experimental study of the strength and suction development of cemented paste backfill (CPB), which is an innovative cementitious construction material for mining (made by recycling mine waste into a construction material), and modified with nanoparticle (NP) additives. The effects of different amounts of four types of NP additives, including nano-silica (SiO₂), nano-calcium carbonate (CaCO₃), nano-iron oxide (Fe₂O₃), and nano-aluminum oxide (Al₂O₃), on the key engineering properties of CPB are investigated. An ether-based polycarboxylate superplasticizer (SP) is added to the backfill to help the NPs to better disperse in the mixture. Ordinary Portland cement is used as the binder in the CPB mixture. Uniaxial compressive tests (UCS) are conducted to determine the strength of the CPB, while suction monitoring experiments are performed to evaluate changes in suction with time. To understand the effects of the NP additives, different microstructural analyses and tests, including thermal analyses (thermogravimetry (TG), differential thermogravimetry (DTG)), mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD) are conducted on the nano-CPB and the cement paste of nano-CPB. The results indicate that the addition of NP additives in the absence of SP results in lower strength due to high likelihood of agglomeration. In contrast, samples with SP and NP additives show a higher UCS and more suction than the control sample at the early ages of curing. It has been observed that the addition of NP additives results in the generation of more hydration products which enhance the interparticle friction and packing density of the CPB structure. Higher strength is obtained by increasing the SP content (0.25%) with the same NP content (1%). Enhancement of the strength of CPB and increase in suction, particularly at early ages, can have great importance in speeding up the mining cycle and thus increasing mining productivity, which is obviously associated with financial benefits to the mine.

Waste management is becoming increasingly important around the world, and incorporating agro-waste into the pavement industry represents a promising strategy for achieving sustainability while improving mixture properties. In this study, we optimize and determine the optimum asphalt binder content of asphalt concrete mixtures modified with waste palm oil clinker powder (WPOCP) and waste rice straw ash (WRSA) to improve their engineering properties. To optimize the interactions between three independent variables (asphalt binder, WPOCP, and WRSA content) on mixture bulk unit weight (BUW), void in the total mix (VTM), Marshall stability, and flow values, the Marshall mix design approach and response surface methodology (RSM) with a Box-Behnken design were used. WPOCP samples containing 2%, 4%, 6%, and 8% by weight of asphalt mixtures were prepared, as were WRSA samples containing 25%, 50%, 75%, and 100% by weight of filler, with asphalt binder content ranging from 4 to 6% by weight of the mix. The statistical model results show that all responses were significant, with high coefficients of correlation (R2) of 0.9840, 0.9971, 0.9920, and 0.9891 for the BUW, VTM, Marshall stability, and flow, respectively. Individual effects of the input variables and synergistic interactions between the three variables were observed to influence all of the responses. Numerical optimization produced optimum WPOCP, WRSA, and asphalt content values of 8%, 74%, and 5%, respectively. The mean error for all responses was less than 5%, indicating that predicted values agree well with experimental data and that generated models accurately reflect experimental results. Based on the findings of the study, it can be concluded that RSM is an effective method for determining the optimal asphalt binder and modifier content in asphalt mixtures. It enables the identification of the most important variables influencing the response of the asphalt mixture and enables mixture optimization for improved performance. Furthermore, incorporating WPOCP and WRSA into asphalt mixtures was found to improve both volumetric and Marshall properties, resulting in a more sustainable approach in the pavement industry.

The high cost and recycling issues of common separators as the main components of Microbial fuel cells (MFCs) have slowed down the development of MFCs recently. In this paper, a polypropylene membrane is proposed as an inexpensive membrane that can be recycled with lower environmental impacts. An experiment is performed in a dual-chamber microbial fuel cell to investigate and compare the proposed membrane effectiveness to Nafion117. The dual-chamber MFC was used because of its ease of use. A mixture of microbes and glucose was fed to the cell during the experiment. The internal resistance and coulombic efficiency are calculated by measuring the circuit voltage, power density, and open-circuit voltage to monitor the performance. The maximum output voltage of 500 mV was attained at a resistance of 380 kΩ. Furthermore, the maximum output power density was 0.7 mW.m⁻², which occurred for 3.3 mA.m⁻².