Strength of SIFCON- Ferrocement One-Way Ribbed Slabs Contain Steel Fibers

Slurry infiltrated fiber concrete” composites (SIFCON) are a novel type of concrete with improved strength, ductility, and crack resistance. In this study, infiltrating fibers (SIFCON) were used to reinforce of specimens of ferrocement one way ribbed slabs. The laboratory work consists of cast and testing of eight specimens with dimensions of 750 mm in length, 500 mm in width and 50 mm in depth. These samples have the same wire mesh reinforcement and the same shape as the ferrocement slabs. Two reference ferrocement slab without ribs contains SIFCON and six ferrocement slabs with ribs contains SIFCON. The variables were the volumetric ratio of fibers in the ribs, which were (2, 4 and 6)% and type of steel fiber (hook-end and hybrid fiber). Hybrid fibers contain two type of steel fiber (hook-end and micro steel fiber) with equal ratio. All samples were tested under line load up to failure with mid deflections for each test with simple supported. The results of the test showed that the presence of steel fibers in the ferrocement ribs, for both types of steel fibers, improves the resistance to the final loads and the ability to reduce deflection and increases the ductility and stiffness significantly.

Morphometric and Immunohistochemical Characteristics of the Adult Human Soft Palate Muscles

The soft palate is the only structure that reversibly separates the respiratory and gastrointestinal systems. Most species can eat and breathe at the same time. Humans cannot do this and malfunction of the soft palate may allow food to enter the lungs and cause fatal aspiration pneumonia. Speech is the most defining characteristic of humans and the soft palate, along with the larynx and tongue, plays the key roles. In addition, palatal muscles are involved in snoring and obstructive sleep apnea. Considering the significance of the soft palate, its function is insufficiently understood. The objectives of this study were to document morphometric and immunohistochemical characteristics of adult human soft palate muscles, including fiber size, the fiber type, and myosin heavy chain (MyHC) composition for better understanding muscle functions. In this study, 15 soft palates were obtained from human autopsies. The palatal muscles were separated, cryosectioned, and stained using histological and immunohistochemical techniques. The results showed that there was a fast type II predominance in the musculus uvulae and palatopharyngeus and a slow type I predominance in the levator veli palatine. Approximately equal proportions of type I and type II fibers existed in both the palatoglossus and tensor veli palatine. Soft palate muscles also contained hybrid fibers and some specialized myofibers expressing slow-tonic and embryonic MyHC isoforms. These findings would help better understand muscle functions.

Multifunctional Gelatin/Chitosan Electrospun Wound Dressing Dopped with Undaria pinnatifida Phlorotannin-Enriched Extract for Skin Regeneration

The similarities of electrospun fibers with the skin extracellular matrix (ECM) make them promising structures for advanced wound dressings. Moreover, infection and resistance in wounds are a major health concern that may be reduced with antibacterial wound dressings. In this work, a multifunctional wound dressing was developed based on gelatin/chitosan hybrid fibers dopped with phlorotannin-enrich extract from the seaweed Undaria pinnatifida. The intrinsic electrospun structure properties combined with the antimicrobial and anti-inflammatory properties of phlorotannin-enrich extract will enhance the wound healing process. Electrospun meshes were produced by incorporating 1 or 2 wt% of extract, and the structure without extract was used as a control. Physico-chemical, mechanical, and biological properties were evaluated for all conditions. Results demonstrated that all developed samples presented a homogenous fiber deposition with the average diameters closer to the native ECM fibrils, and high porosities (~90%) that will be crucial to control the wound moist environment. According to the tensile test assays, the incorporation of phlorotannin-enriched extract enhances the elastic performance of the samples. Additionally, the extract incorporation made the structure stable over time since its in vitro degradation rates decreased under enzymatic medium. Extract release profile demonstrated a longstanding delivery (up to 160 days), reaching a maximum value of ~98% over time. Moreover, the preliminary antimicrobial results confirm the mesh’s antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus. In terms of biological characterization, no condition presented cytotoxicity effects on hDNF cells, allowing their adhesion and proliferation over 14 days, except the condition of 2 wt% after 7 days. Overall, the electrospun structure comprising phlorotannins-enriched extract is a promising bioactive structure with potential to be used as a drug delivery system for skin regeneration by reducing the bacterial infection in the wound bed.

Production and in vitro analysis of catechin incorporated electrospun gelatin/ poly (lactic acid) microfibers for wound dressing applications

Nowadays, herbal materials are applied extensively in fibrous structures for application as a wound dressing. In this study, catechin (Cat) as the green tea extract with antibacterial characteristics has been loaded in gelatin (Gel)/poly (lactic acid) (PLA) fibrous structure by double-nozzle electrospinning technique. For this, PLA-Cat from one nozzle and Gel-Cat solution from another were injected, and fabricated Gel/PLA, Gel/PLA-Cat, Gel-Cat/PLA, and Gel-Cat/PLA-Cat hybrid fibers were gathered onto a rotating collector. In order to verify the application of these scaffolds in bio applications, the morphological, chemical, wettability property, and biological features of fibers were analyzed using SEM, contact angle analysis, antibacterial, and cell attachment tests. The viscosity of spinning solutions increased with the addition of Cat to them that resulted in an increase of fibers diameter. Fourier transform infrared spectroscopy highlighted the presence of PLA, Gel, and Cat in the final structure. The results exhibited that the presence of Cat improved the antibacterial activity. Furthermore, cell attachment studies with L929 fibroblast cells demonstrated that incorporation of catchin increased the cell viability without any toxicity.

Ballistic Impact Resistance of UHPC Plates Made with Hybrid Fibers and Low Binder Content

This study assesses the ballistic impact strength of thin plates made of ultra-high-performance concrete (UHPC) with low cement content (250 kg/m3) and volumes of 80% steel and 20% polypropylene (PP) hybrid fibers. The plates were prepared with thicknesses of 30, 50, and 70 mm and fiber volume ratios of 1.5% and 3.0%. Compressive strength, flexural tensile strength, residual strength, and ballistic impact strength were determined using experimental methods. Test results showed that regardless of fiber content, the UHPC specimens prepared with the hybrid fibers showed similar performance against ballistic impact, exerting relatively low impact energy below 1000 J. The UHPC3.0 mixture made with 3.0% hybrid fiber content exhibited the best performance in terms of energy absorption and spalling resistance at impact energy levels greater than 4000 J. Plate sections with thicknesses of 7 mm showed class III performance (highest level), as recommended for military-based applications.

Performance of Fiber Self Compacting Concrete at High Temperatures

The goal of this study is to assess the fresh and hardened properties of self-compacting concrete (SCC) prepared using locally available materials. This research includes also the impact of polypropylene (PP), steel and hybrid fibers on the same properties. In addition, the mechanical properties of SCC specimens (with and without fibers) at high temperatures, including as compressive, tensile, and flexural strengths, will be determined. Four different SCC mixtures (with and without fibers) are prepared, tested, and assessed in order to attain these goals. The specimens were heated to various temperatures (200, 400, 600, and 800) at a rate of 5 degrees Celsius per minute for each test. The temperature was remained constant at the target temperature for one hour before cooling to ensure a consistent temperature throughout the specimen. According to the test results, all of the mixes have good consistency and workability in terms of filling and passing ability. In addition, the inclusion of fibers lowered the workability of SCC slightly. Also, the compressive, tensile, and flexural strengths improved with increasing temperature up to 200 °C and dropped at temperatures over 200 °C, according to these findings. Within the SCC, the PP fibers lowered and removed the risk of spalling. Concrete mixtures containing steel fibers and hybrid fibers have the finest mechanical characteristics and spalling resistance as temperature rises. Weight losses were lower in SCC mixtures with PP and steel fibers than in those without PP and steel fibers. As the temperature rose, all SCC mixes lost mass and UPV decreased until the samples spalled (as in plain SCC and SCC with steel fibers) or were questionable (as in SCC with PP and SCC with hybrid fibers). Doi: 10.28991/cej-2021-03091779 Full Text: PDF

Study on Steel and polypropylene hybrid fiber reinforced concrete– A review

Increasing demand and inadequate materials availability leads the researchers to find alternate materials. In general, hybrid fiber is nothing but mixture of two or more fibers. In this review, various properties of steel fibers and polypropylene fibers were studied. In order to study the physical and mechanical properties of steel fiber, polypropylene fiber and other materials used in concrete, various tests such as Slump cone test, Compaction factor, Compressive strength , flexural strength etc., were used. Hybrid fibers have the tendency to control cracks at different levels. Workability of concrete get reduced due to more addition of steel fibers.The addition of steel fiber and polypropylene fiber results in an increase of 12 to 14.30% compressive strength, 33 to 36.6% increase in flexural strength and 9 to 10.16% increase in split tensile strength. Addition of most favorable amount 0.9 to 1% of steel fiber and 0.9 to 1% of polypropylene fiber gives maximum compressive strength up to 41.67 to 42.68%. Split tensile strength increases by increasing the fiber content in concrete but workability decreases when steel fiber content is increased in concrete.