Cleaner Materials最新文献

Phosphorus acts as a vital part in the improvement of environment, manufacturing and agriculture. However, it can also become a contaminant in water bodies, posing a danger to the human, animals and the ecosystems. To address this issue, different methods exist for removing phosphorus from water, with bio-sorption being a mainly effective and eco-friendly option. Plant leaf biosorbents offer different levels of effectiveness, depending on the taxonomic group and pre-treatment of the plant, among other factors. In this research, locally available plant leaf biosorbents, including neem, javapalm, guava, sapota, custard apple, and mango leaves, were measured for their capability to eliminate phosphorus from water. Results indicated that mango leaves were the most effective, followed by javapalm, sapota, custard apple, neem, and guava leaves. The optimal conditions for phosphorus removal were a normal pH of 4–8, 1.2 g quantity, 60 min of contact time, a temperature of 25 °C, and a rotation speed of 100 rpm. Regeneration and reapplication of the plant leaf biosorbents can further improve the efficiency of the process.

Fiber reinforced composites possess exceptional mass-specific properties and therefore offer a high potential for weight reduction in lightweight applications. However, the need to recover, remanufacture and recirculate polymer composites at lower temperatures is still an area to be addressed. For a cleaner and more sustainable reuse of polymer composites at their end-of-use (EoU) phase, a materials circularity strategy can be applied. This work describes a novel method and proof-of-concept to recover carbon-fiber (CF)/ polyether-ether-ketone (PEEK) composites. It is composed of three steps: i.) initiation of controlled interlaminar pre-cracks by power ultrasonics, ii.) propagation of the pre-cracks under peel-like loading, and iii.) ultrasonic reconsolidation of the separated layers. Microscopic and mechanical investigations on the composite materials before and after the separation and reconsolidation, shows near-identical fiber-bundle arrangements, with the reconsolidated composites retaining approximately 89 % of its mechanical properties compared to the original laminate.

One approach to decreasing the environmental footprint of the construction industry is to replace ordinary Portland cement (OPC) with recycled slag and fly ash activated using alkaline materials. This article presents the outcomes of an experimental study that evaluated water absorption characteristics and strength development of mortar that uses blends of alkali-activated ASTM class F slag and fly ash binders. Mortar mixes were developed using three binder combinations: 100% slag and no fly ash (S1F0), 75% slag + 25% fly ash (S3F1), and 50% slag + 50% fly ash (S1F1). Slag and fly ash binders were activated using NaOH solution with molarity ranging from 10 mol/L to 16 mol/L mixed with sodium silicate solution. Two sets of samples were created, one set was immersed in an acidic medium after casting, which represented a closed environment, and the second was left in the lab exposed to air until the test day. For mortar cured in a closed system, the highest strength development during the first seven days after casting occurred in S1F0 mortar followed by S3F1, then S1F1. The observation indicates strength development is dominated by the fast reactivity of slag during the first 7 days. The pattern is similar for all NaOH activator concentrations evaluated in this study. Mortar samples with high slag content (S1F0 and S3F1) that were cured in air experienced a decrease in strength during the 28–90 day curing phase as the strength at the age of 90 days decreased relative to the strength at 28 days. However, S1F1 gained strength during the 28–90 day phase when NaOH molarity was the highest (16 mol/L). This is due to the dissolution and activation of fly ash at high solution alkalinity which contributed to the continued increase in strength. A strong linear correlation between the square root of time (t^0.5) and water absorption existed in all activated mortars evaluated in the study, except for mortar samples prepared using NaOH with high concentration and the highest ratio of Na₂SiO₃/NaOH. Therefore, alkali-activated slag-based mortars share similar water capillary absorption characteristics with conventional cement-based mortar. It was found that increasing the NaOH concentration increases the global warming potential (gwp) and that the mix with the least environmental impact was the S1F1 developed using the lowest NaOH concentration of 10 mol/L and 50% fly ash.

Chemical treatments can remove waxes and sugar components from the surface of bio-fibres, increasing their compatibility with mineral binders. This paper investigates the effects of alkali solutions treatments on miscanthus shives. For 8, 24, and 48 h, fibres were immersed in NaOH solutions at 1.5, 2.5, and 5.0% concentrations, with and without a 2.5% sodium silicate solution, having a silica modulus (SiO₂/Na₂O) of 2.0. SEM and Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to investigate the effect of different treatments on the microstructure and surface chemistry of miscanthus. The SEM results show that the morphologies of miscanthus fibres were significantly altered in the case of 5.0% NaOH treatment, with a weakening of the inner cell structures in some locations. Furthermore, the ATR-FTIR patterns of raw and treated shives were analysed, suggesting that treating miscanthus with 2.5% NaOH and 2.5% sodium silicate results in the required chemical modifications while retaining the cellular structure of miscanthus fibres. For all treatments, the absorbance was reduced by 31 to 77% at 450 cm⁻¹ and 48–80% at 1035 cm⁻¹.

Ordinary Portland cement (OPC) mortar and concrete products are designed to withstand compressive loads. However, these products show low deformation before fracture because they are fragile materials, also showing low tensile strength in comparison to compressive strength. These limitations can be minimized by adding fibers, as reinforcement, to the cement matrix. Therefore, in this work the mechanical behavior of cement pastes reinforced with fiberglass waste and fly ash was studied. A 2 k factorial design was used and the experimental factors were the fiberglass waste content (0.2–0.8 mass %), fiberglass length (0.3–1 cm) and fly ash content (0–10 mass %). Fly ash was added to reduce the alkalinity of the cement paste and, therefore, to avoid the chemical attack on the glass fibers. Nine compositions were made, and their compressive strength, tensile strength, apparent density, and microstructure were determined. Type III Portland cement, class F fly ash, and type E fiberglass were used and characterized by XRF. The composites were characterized by XRD and optical microscopy. The ANOVA for compressive strength at 30 days shows that the combined effect of fiber addition and fiber length increased the strength of the samples by 27 % (30.3 MPa). At 60 days the fly ash raised the compressive strength by 32 % (37.4 MPa) regarding the reference sample, probably because the filling effect. The tensile strength at 60 days was influenced by the fiber length, with an increase of 71 % (6.31 MPa). The apparent density was reduced 19 % (1.50 g/cm³) with addition of fly ash and fibers. The fibers can reduce the crack propagation in the matrix, in a typical bridging effect. The cement hydration was not affected by the addition of fiberglass waste.

In the production and manufacturing stream, green supply chain management has attracted much attention from academicians and policy makers. It encompasses theoretical and practical models, ranging from macro-level institutional pressure to micro-level lean manufacturing, total quality management, and supplier relationship management. A rising number of corporations are embracing sustainable development strategies, either due to peer pressure or to fulfil their social responsibilities to society and the environment. Against this backdrop, although vast literature is available, it lacks a theoretical model and management strategy for effective implementation of the GSCM within the firms effectively. The latest literature has a limited vision from the management perspective. Despite such popularity, there is a requirement for a comprehensive framework that can investigate the effect of GSCM on financial, social, and environmental performance with environmental uncertainties and product complexities at the micro-level. Therefore, the purpose of this study is to examine previous research and develop a theoretical model that incorporates an excellent theory-building process between the three primary features of global supply chain management practises competitive advantage and organizational performance. The study employs bibliometric analysis to conduct a holistic review to explore GSCM research and evaluate its methodological design, publication trends and themes.

Regression analysis is commonly used to predict the compressive strength of soil-based materials to reduce the time and cost of construction projects. This study presents the results of multivariate regression analysis on the prediction of modulus of rupture and specific energy of cement-stabilised earth bricks reinforced with bamboo cellulose fibres as a function of cellulose fibre percentage, curing temperature and curing time. Statistical modelling is carried out on the experimental data of the four-point bending test of clay brick stabilised with 10 wt% Ordinary Portland Cement reinforced with 0, 5, 7.5 and 10 wt% organosolv bamboo pulp fibres. The water content of the unreinforced specimen was adopted at 25 wt% of the solid materials based on the plastic limit value of the soil, while the value of the water content of the samples with cellulose fibres was 35 wt% due to the affinity of the cellulose with water as well as to allow good extrudability of the pulp. The bricks were cured under different conditions (23 °C, 60% RH and 60 °C, 100% RH) and at different ages (14 and 28 days). Regression analysis and two-way ANOVA were studied to assess the accuracy, correlation and effect of each variable on the prediction of the random response variable. The results showed that non-linear regression analysis provides the best-fitting statistical model with an accuracy of 96%. In addition, the curing temperature and the percentage of cellulose fibres significantly affect the bricks bending performance, while the effect of curing time is the least visible. This non-linear model can be adopted as a suitable model to predict the flexural properties of cellulose pulp fibre-reinforced earth bricks for a sustainable building solution in developing countries. For better generalization and practical application of this method to predict the flexural performance of cellulose pulp fibre-reinforced earth bricks, a large data set of a broader range should be explored.

In cold regions, air entrained concrete has been widely used against freeze–thaw deterioration. This paper studied the influence of curing conditions on the strength and durability of air entrained ordinary portland cement (OPC) and fly ash (FA) concrete. Four different curing conditions including standard curing (SC), air curing (AC), mild temperature curing (MC), and elevated temperature curing (EC) were utilized to cure the cast specimens. The compressive strength at 3, 7, 14, and 28 days was measured respectively. Also, the water absorption, sorptivity, air void system, as well as freeze–thaw durability after 28 days of curing were investigated. Test results suggested that AC condition impeded the strength gain of both concrete, but it affected FA concrete more than OPC concrete. EC condition improved the early-age strength while compromised the later-age strength of OPC concrete, whereas EC condition improved the compressive strength of FA concrete at both early ages and later ages. AC condition has more adverse effects on water absorption as well as sorptivity of FA concrete than those of OPC concrete. EC condition increased the water absorption and sorptivity of OPC concrete, whereas reduced the water absorption and sorptivity of FA concrete. Although the air content in fresh OPC and FA concrete were comparable, FA concrete had less proportion of microvoids (air voids smaller than 300 μm), larger spacing factor but smaller specific surface, regardless of curing conditions. EC condition caused the reduction in air content, the increase of spacing factor, and decrease of specific surface. For both OPC concrete and FA concrete, the four curing conditions produced different freeze–thaw durability factor (DF), but all the specimens passed the failure limit of 60 %. The freeze–thaw test results based on specimens under SC condition may overestimate the DF.

In general, the use of ceramic waste powder (CWP) in concrete production is limited to few percentages (i.e., less than approximately 10–15% of Portland cement), given the resulting decrease in concrete strength and durability. This paper seeks to assess the relevance of blending CWP with blast furnace slag (BFS) to foster pozzolanic reactions and reinstate the drop in strength and structural performance of reinforced concrete (RC) members. Two categories of normal- and high-strength concrete (NSC and HSC) mixtures possessing 34 and 71 MPa compressive strengths are tested in this program. The RC beams measured 2-m in length and were differently configured by steel reinforcements to assess the flexural and shear strengths as well as the bond to embedded spliced rebars. Regardless of the steel configuration, results showed that the structural properties curtail when the concrete mixtures are prepared with 10% CWP replacement rate. This was attributed to a dilution effect and higher CWP porosity that detrimentally alter the concrete microstructure and strengths. The drop in flexural, shear, and bond strengths was found to be fully restored with the use of ternary binder composed of 55% cement, 35% BFS, and 10% CWP. Such results are in line with the improved concrete strength and durability, revealing the relevance of blending CWP with BFS to foster synergistic effects and reinstate the structural properties of NSC and HSC beams. Findings of this work can increase the CWP added-value for the construction industry, while reducing the cement carbon footprint.

The construction industry plays a key role in the economic development of countries. The industry faces challenges such as high energy consumption, long construction time, high manufacturing costs. 3D printing technology can solve many problems in this industry. The goal of this research is to find suitable materials for the 3D printing of an energy-efficient building with the least environmental impact. Magnesium potassium phosphate cement (MKPC) was selected for this study. In the next step, energy consumption in the building is simulated and different scenarios are considered to optimize energy consumption and reduce environmental impacts. Then, the life cycle assessment is done for the best scenario. Finally, this scenario is compared to the case where portland cement enters the composition. The simulation results show that PCM (phase change materials) has very little effect on reducing the energy consumption of the building. In contrast, insulation has almost halved energy consumption. Magnesium oxide and monopotassium phosphate have a significant share in the environmental effects of concrete walls. By adding 30% by volume of M20 concrete, the environmental impacts are reduced almost 28%.