Basalt fiber reinforcement in polymer composites has recently become very competitive to the routinely used synthetic fiber reinforcements. In the present work, composite specimens were prepared with ...basalt fiber mat reinforcement in vinyl ester matrix along with varying quantity of the micro and nano silicon carbide (SiC) filler particle ranging from 1 to 5 wt% in combination. Tribological and water absorption properties of the developed hybrid composites were tested to ascertain its potential for commercial applications. The specimen made of SiC particle addictive combination of 3 wt% nano and 3 wt% micro particle exhibited better mechanical characteristics and this mechanical advantage declines beyond 3 wt% SiC filler addition due to agglomeration and poor dispersion of filler particles in the hybrid composite. The microstructural investigation done via scanning electron microscopy reveals the modes of failure, where better pull‐out resistance was displayed by the fiber bonding characteristics with the filler and vinyl ester matrix up to 3 wt% nano and 3 wt% micro SiC filler content. Similarly, the tribological characteristics of the composite specimen for the optimum filler content specimen were superior in comparison with other combinations. Moreover, the water absorption features of the developed hybrid composites were within the acceptable limits for marine and structural applications.
•Mine tailings could substitute silica powder and sand in UHPC.•Characteristics of UHPC were varied by the shape and size of tailings.•Leaching of toxic elements in tailings was highly controlled by ...UHPC matrix.
High production cost and scarcity of raw materials may hinder the application and accessibility of ultra-high performance concrete (UHPC). In the present study, mine tailings, mineral waste products from mining sites, were applied to mitigate these problems. Two types of quartz-based mine tailings produced in South Korea were used to substitute silica powder and silica sand by half and fully in UHPC. The characteristics of UHPC with the tailings, including the compressive strength, workability, water absorption, and leachability of toxic elements, were experimentally evaluated. The effects of the tailings on the characteristics of UHPC varied according to the shape and size of particles of the tailings. The leaching of toxic trace elements from the tailings was highly controlled due to the chemical and physical capsulation of UHPC.
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Bacterial cellulose (BC) produced by aerobic bacteria has the advantages of high purity, high porosity, strong water absorption, high water holding capacity, high mechanical strength ...and good biocompatibility. In this review, we briefly introduced the characteristics of BC and the production and modification methods of BC, and focused on the application of BC in skin tissue and bone tissue engineering. At the same time, we summarized the role of BC as a wound dressing and bone repair material in wound healing and bone repair, and prospects for the application of BC as a wound dressing and bone repair material.
•State of the art systematic review on the study of recycled aggregates for concrete production.•Statistical analysis of the main properties of recycled aggregates and comparison with those of ...conventional aggregates.•Proposal of a performance-based classification system for recycled aggregates meant for concrete production.
Arising from a systematic, as opposed to narrative, literature review of 236 publications published over a period of 38years from 1977 to 2014, the paper examines the factors affecting the physical, chemical, mechanical, permeation and compositional properties of recycled aggregates sourced from construction and demolition waste, intended for concrete production. Classifications based on their composition and contaminants have been studied. The data were collectively subjected to statistical analysis and a performance-based classification, mainly for use in concrete construction, is proposed. The results allowed producing a practical means of measuring the quality of recycled aggregates, which can be used to produce concrete with predictable performance.
Four kinds of agricultural wastes (oilseed rape straw (OS), rice straw (RS), wheat straw (WS) and corn stover (CS)) liquefied polyols were used to replace petroleum based polyol and prepare bio-based ...polyurethane (PU) foam successfully. The effect of NCO/OH ratio on PU foaming process and foams properties, such as density, compressive strength, elastic modulus, morphological structure, storage modulus (E’), glass transition temperature (Tg), water absorption ability and chemical structure, was investigated respectively. It is confirmed that CS based polyol appears the highest activity to react with pMDI, while reactivity of OS based polyol is the lowest. Foams made with NCO/OH ratio among 1.4–1.7 appear excellent morphological, physical, mechanical, water absorption and chemical properties, which are comparable with or even better than those of petroleum polyol based PU foams.
•Four kinds of bio-polyols are used to prepare bio-based polyurethane foams.•Effect of NCO/OH ratio on foaming process and foams properties are investigated.•Influence of polyol species and properties on foam performance is discussed.•These bio-based foams show comparable/better property than petroleum based foams.•Confirmed a universally proper NCO/OH ratio range to get excellent bio-based foam.
This paper presents an experimental study on a new mixture scheme of mortar. Unlike most of existing work, the present study investigates nano-CuO (NC), and its combined effects with cement ...replacement i.e., rice husk ash (RHA) on durability performance, as well as strength and permeability properties of mortars. Comprehensive observations of both the performance and properties improvements on RHA-containing mortar specimens were determined with the addition of NC. To this end, a series of tests for examining the strength both directly (compressive strength) and indirectly (Ultrasonic Pulse Velocity), electrical resistivity, chloride permeability, water absorption and microstructure characteristics (i.e., SEM micrographs, Mercury intrusion porosimetry (MIP) & capillary analyses) of mortar specimens were performed. A relationship between the Rapid chloride permeability test (RCPT) and electrical resistivity was also studied in order to recommend an alternative method for quality control in the presence of RHA and NC. Finally, a mixture scheme which provides relatively satisfactory properties improvement with positive environment credential is suggested.
•Both single and combine effects of NC and RHA on mortar properties are reported.•Binary combination of NC and RHS markedly improves performance and properties of mortar.•A relationship between the RCPT and electrical resistivity was studied for quality control.•The opposite effects caused by RHA and nano-CuO on porosity and sorptivity are quantitatively discussed.•RHA20NC3 provides satisfactory properties improvement with positive environment credential.
Invisible orthodontic aligners (IOAs) have been introduced in the orthodontic field as an innovative alternative for fixed brackets, in relation to their ability to be easily inserted/removed from ...the oral cavity without affecting the chewing ability and the aesthetic of the patients. The paper provides a complete physicochemical and mechanical characterization of thermoplastic materials in the form of disks used for commercial IOAs. A wide palette of specific techniques is considered, from tensile tests and dynamic-mechanical analysis, to X-Ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR-ATR) analyses and water absorption tests. The disks are investigated before and after immersion into staining beverages (red wine, coffee, nicotine and artificial saliva), in terms of colour variations, transparency, and microscopic surface modifications by means of colorimetry, UV-VIS absorbance and scanning electron microscopy (SEM). Among all the samples, polyurethane (PU) exhibited the highest crystallinity and the highest values of mechanical and thermal resistance, while the poly(ethylene terephthalate)-glycol (PETG) samples presented better transparency and less ability to absorb water. Moreover, red wine and coffee give noticeable colour variations after 14 days of immersion, together with a slight reduction of transparency.
Cement is the most important binding agent used in soil stabilization and significantly improves the strength and compressibility of soils. However, owing to the significant environmental and ...socio-economic impact of cement production, alternative, low-carbon binders are increasingly being sought. Among them, waste-based inorganic additives used in construction provide sustainable soil treatment materials and reduce the need for landfills. Effective mud stabilization depends on the type of stabilizers and their mineralogical setup, as well as an understanding of their water absorption capacity. Therefore, this study investigated the factors influencing the water absorption characteristics of waste-based additives, including paper sludge ash (PSA), palm kernel shell ash (PKSA), rice husk ash (RHA), coal fly ash, hemihydrate gypsum, limestone powder, and basalt rock powder (BRP). The water absorption capacity (Wab) of each additive represents the amount of water absorbed per gram evaluated via the suction filtration method. The long-term water absorption capacities of the waste additives were compared with a conventional additive, blast furnace cement class B (BFCB). Although PSA, PKSA, and RHA absorbed more water than BFCB under short-term curing, BFCB exhibited the highest Wab under long-term curing. PSA, PKSA, and RHA had a water absorption capacity at 4 h (Wab)t = 4h of 74.5%, 107.3%, and 62.9%, respectively, whereas that of BFCB was 37.4%. In contrast, after 168 h, the water absorption capacity of BFCB increased to 126.1%. These evaluated water absorption capacities were categorized into immediate and time-dependent stages. Mercury intrusion porosimetry, X-ray diffraction (XRD), and scanning electron microscopy investigations were conducted to investigate the influence of factors such as porosity and hydration of the different additives on water absorption capacity. The results showed that porosity characteristics affect the immediate water absorption capacity, and hydrate formation contributes to increased water absorption during curing. The waste additives PSA, PKSA, and RHA with irregular surfaces and pores were highly porous and exhibited a high immediate water absorption capacity (Wab)t = 4h, unlike the additives with flat surfaces and less irregularities with lower (Wab)t = 4h. The XRD investigation revealed that the presence of ettringite and calcite contributed to increased water absorption during curing for PSA, PKSA, and BFCB. The generation of needle-like ettringite could promote a denser microstructure in PSA, PKSA, and BFCB, thus further improving Wab during curing. Finally, using cone index strength, we explored the effective application of waste-based additives as soil stabilizers, attempting to predict the effect of water absorption capacity on the properties of treated soil. The stabilizer addition ratio (A) and Wab of the waste additives were found to be essential indicators for predicting the strength development of treated clays. A clear correlation was observed between the cone index (qc) and parameter β(t), which is derived from Wab and A, of the treated clays.
•Enormous heat rejection by ARS is utilized to drive an MED desalination unit.•Techno-economic analysis is conducted to explore the combined system potential.•A parametric analysis is performed to ...study the sensitivity of the system performance.•Fresh water produced increases as COP of ARS decreases.
This paper investigates the opportunities for integrating single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) via cascade of rejected heat. Cooling capacity and hourly water production are calculated from thermodynamic properties of the working fluids at different operating conditions using simple models for each of the constituent systems. Additionally, the second law of thermodynamics is applied with the aim of examining the total exergy destruction of the entire stand-alone and combined systems. A cost model is developed as well in order to estimate the total annual cost of the system and the unit production cost (UPC) of both fresh water and cooling. The results indicate that the total exergy destruction of the combined systems, which consist of an MED unit driven by either a single- or double-stage NH3–H2O refrigeration system, decreases by an average of 55% compared to stand-alone NH3–H2O and MED systems. Relative to stand-alone systems, although water production decreases by 30% and 9% when an MED unit is integrated with single- and double-stage NH3-H2O absorption systems, respectively, cooling capacity remains unchanged for the double-stage NH3-H2O–MED system, and only decreases by 16% for the single-stage NH3-H2O–MED system. Moreover, the UPC of cooling decreases significantly by an average of 43% for both coupled systems, whereas the UPC of the produced water increases by only 19% and 3% for single- and double-stage NH3H2O–MED systems, respectively.
•Water/binder ratio can affect the optimal fiber content.•Full curves of water absorption were obtained.•Pore size or porosity characteristics of hardened concrete were analyzed.
This paper presents ...the results of a comprehensive experimental work investigating the effect of glass fiber (GF) and polypropylene fiber (PPF) on the mechanical and microstructural properties of concrete as a function of the water/binder ratio and fiber content. Different water/binder ratios (0.30 and 0.35), GF and PPF contents (0.45, 0.90, and 1.35% by volume fractions), and curing times (7 and 28 d) were used during the experiment to prepare the concrete specimens. The compressive, four-point flexural, and splitting tensile strengths and the full curves of water absorption of the glass-fiber-reinforced concrete (GFRC) and polypropylene-fiber-reinforced concrete (PPFRC) were obtained. The strength differences and water absorption properties of GFRC/PPFRC were analyzed in depth. Scanning electron microscope observation was undertaken to analyze the mechanism of the water/binder ratio and fiber effects. The results showed that the water/binder ratio can affect the optimal fiber content. When discussing the effect of fibers on the improvement of concrete mechanical or microstructural properties, the influence of the water/binder ratio should be considered. The improvement effect of GF on water absorption was significantly superior to that of PPF. When the water/binder ratio was 0.30, the water absorption of GFRC and PPFRC tended to be stable as the test proceeded, while when the water/binder ratio increased to 0.35, the water absorption of the GFRC and PPFRC with the highest fiber dosage still increased with the prolongation of testing time.
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