Strain Hardening Behavior of Engineered Geopolymer Composites: Effects of the Activator Combination

Fly ash-based engineered geopolymer composites (EGCs) exhibiting strain hardening behavior under uni-axial tension were developed employing two different sodium-based (Na-based) and potassium-based (K-based) activator combinations. The relatively brittle low calcium (Class F) fly ash-based geopolymer matrix was reinforced with randomly oriented short poly vinyl alcohol (PVA) fibers (2% v/v). Na-based activator combination was composed of 8.0 M NaOH solution (28.6% w/w) and Na2SiO3 solution (71.4% w/w) with a SiO2/Na2O ratio of 2.0; whereas, Kbased activator combination was composed of 8.0 M KOH solution (28.6% w/w) and K2SiO3 solution (71.4% w/w) with a SiO2/K2O ratio of 2.23. The matrix and composite properties of the developed fly ash-based EGCs including workability of the fresh matrix, density, compressive strength and uni-axial tensile behavior were evaluated. The experimental results revealed that the sodium-based EGC (EGC-Na) exhibited superior tensile strain capacity, compressive and uni-axial tensile strengths with significantly enhanced ductility

Derivation of extracts from Persian Gulf sea cucumber (Holothuria leucospilota) and assessment of its antifungal effect

Sea cucumber is presented as a potential marine source of antimicrobial compounds. The purpose of this study is to evaluate antifungal effects of sea cucumber, Holothuria leucospilota, extracts on Aspergillus niger and Candida albicans. Methanol and chloroform extracts of the body wall, gonad and intestine of sea cucumber, H. leucospilota, collected from Persian Gulf, were evaluated for their antifungal activity against A. niger and C. albicans. The activity was determined using serial dilution method. Antifungal activity, minimum inhibitory concentration and minimum fungicidal concentration were evaluated by the different concentrations. Results showed that each of the extracts had antifungal effect at specified concentrations on the A. niger. All examined concentrations of Gonad methanol and intestine chloroform extracts had no inhibitory effect on C. albicans. Chloroform extracts of gonad and intestine had more fungicidal effect against A. niger compared with C. albicans. Gonad chloroform extracts showed more fungicidal effect on the C. albicans at concentrations of 2.5, 5 and 10 mg/ml. Sea cucumber extract can be considered as an antifungal agent in various industries such as medicine and pharmaceutical industry

Multiscale description of carbon-supersaturated ferrite in severely drawn pearlitic wires

AbstractA multiscale simulation approach based on atomistic calculations and a discrete diffusion model is developed and applied to carbon-supersaturated ferrite, as experimentally observed in severely deformed pearlitic steel. We employ the embedded atom method and the nudged elastic band technique to determine the energetic profile of a carbon atom around a screw dislocation in bcc iron. The results clearly indicate a special region in the proximity of the dislocation core where C atoms are strongly bound, but where they can nevertheless diffuse easily due to low barriers. Our analysis suggests that the previously proposed pipe mechanism for the case of a screw dislocation is unlikely. Instead, our atomistic as well as the diffusion model results support the so-called drag mechanism, by which a mobile screw dislocation is able to transport C atoms along its glide plane. Combining the C-dislocation interaction energies with density-functional-theory calculations of the strain dependent C formation energy allows us to investigate the C supersaturation of the ferrite phase under wire drawing conditions. Corresponding results for local and total C concentrations agree well with previous atom probe tomography measurements indicating that a significant contribution to the supersaturation during wire drawing is due to dislocations

In vitro cytotoxic and anti-cancer effects of body wall for sea cucumber (Holothuria leucospilota)

In recent years efforts to find bioactive compounds from live organisms especially marine animals have been increased. In the present study, the anticancer and cytotoxic effects of sea cucumber body walls (Holothuria leucospilota) were investigated. For this purpose, sea cucumbers were collected from Larak Island at depths of 10 to 30 m and extraction process was done with methanol and diethyl ether solvent which then concentrated by rotary evaporator (40℃) following lyophilization with vacuum freeze dryer. XTT method was used to investigate anticancer and cytotoxic effects of body wall extracts. The results showed that the methanolic extract could prevent proliferation of human oral epidermoid carcinoma cells (KB) at concentrations of 100 and 500 μg/ml. The diethyl etheric extract also could prevent proliferation of KB at 500 μg/ml concentration. Overall result showed that sea cucumber body wall had a strong cytotoxic effect on normal cell line (Human embryonic kidney cell [HEK]) which can be used as potent cytotoxic material. However these extracts did not show significant therapeutic value against KB cells

Advanced data mining in field ion microscopy

Field ion microscopy (FIM) allows to image individual surface atoms by exploiting the effect of an intense electric field. Widespread use of atomic resolution imaging by FIM has been hampered by a lack of efficient image processing/data extraction tools. Recent advances in imaging and data mining techniques have renewed the interest in using FIM in conjunction with automated detection of atoms and lattice defects for materials characterization. After a brief overview of existing routines, we review the use of machine learning (ML) approaches for data extraction with the aim to catalyze new data-driven insights into high electrical field physics. Apart from exploring various supervised and unsupervised ML algorithms in this context, we also employ advanced image processing routines for data extraction from large sets of FIM images. The outcomes and limitations of such routines are discussed, and we conclude with the possible application of energy minimization schemes to the extracted point clouds as a way of improving the spatial resolution of FIM

Steel fiber reinforced concrete : a review

Concrete is one of the world most widely used construction material. However, since the early 1800’s, it has been known that concrete is weak in tension. Weak tensile strength combined with brittle behavior result in sudden tensile failure without warning. This is obviously not desirable for any construction material. Thus, concrete requires some form of tensile reinforcement to compensate its brittle behavior and improve its tensile strength and strain capacity to be used in structural applications. Historically, steel has been used as the material of choice for tensile reinforcement in concrete. Unlike conventional reinforcing bars, which are specifically designed and placed in the tensile zone of the concrete member, fibers are thin, short and distributed randomly throughout the concrete member. Fibers are commercially available and manufactured from steel, plastic, glass and other natural materials. Steel fibers can be defined as discrete, short length of steel having ratio of its length to diameter (i.e. aspect ratio) in the range of 20 to 100 with any of the several cross-section, and that are sufficiently small to be easily and randomly dispersed in fresh concrete mix using conventional mixing procedure. The random distribution results in a loss of efficiency as compared to conventional rebars, but the closely spaced fibers improve toughness and tensile properties of concrete and help to control cracking. In many situations it is prudent to combine fiber reinforcement with conventional steel reinforcement to improve performance. Fibre Reinforced Concrete (FRC) is defined as a composite material essentially consisting of conventional concrete or mortar reinforced by the random dispersal of short, discontinious, and discrete fine fibres of specific geometry. Since Biblical times, approximately 3500 years ago, brittle building materials, e.g. clay sun baked bricks, were reinforced with horse-hair, straw and other vegetable fibres. Although reinforcing brittle materials with fibers is an old concept, modern day use of fibers in concrete is only started in the early 1960s. Realizing the improved properties of the fiber reinforced concrete products, further research and development on fiber reinforced concrete (FRC) has been initiated since the last three decades. This paper presents an overview of the mechanical properties of Steel Fiber Reinforced Concrete (SFRC), its advantages, and its applications

Emissions from dryer vents during use of fragranced and fragrance-free laundry products

Fragranced laundry products emit a range of volatile organic compounds, including hazardous air pollutants. Exposure to fragranced emissions from laundry products has been associated with adverse health effects such as asthma attacks and migraine headaches. Little is known about volatile emissions from clothes dryer vents and the effectiveness of strategies to reduce concentrations and risks. This study investigates volatile emissions from six residential dryer vents, with a focus on d-limonene. It analyses and compares concentrations of d-limonene during use of fragranced and fragrance-free laundry products, as well as changes in switching from fragranced to fragrance-free products. In households using fragranced laundry detergent, the highest concentration of d-limonene from a dryer vent was 118g/m(3) (mean 33.34g/m(3)). By contrast, in households using only fragrance-free detergent, the highest concentration of d-limonene from a dryer vent was 0.26g/m(3) (mean 0.25g/m(3)). After households using fragranced detergent switched to using fragrance-free detergent, the concentrations of d-limonene in dryer vent emissions were reduced by up to 99.7% (mean 79.1%). This simple strategy of switching to fragrance-free products significantly and almost completely eliminated d-limonene emissions. Results from this study demonstrate that changing from fragranced to fragrance-free products can be a straightforward and effective approach to reduce ambient air pollution and potential health risks

Flexural behavior of Steel-Fiber-Added-RC (SFARC) beams with C30 and C50 classes of concrete

Although conventional reinforced concrete (RC) is the most globally used building material; however, its detrimental structural characteristics such as brittle failure mechanism in tension need to be improved. Discrete and short steel fibers (SFs) can be added into the concrete mix to improve its brittleness. The effects of the addition of optimum percentage of SFs on flexural behavior of RC beams have been investigated in this paper. In this study, the optimum percentage of hooked-end SFs with the dimensions of 0.75mm in diameter and 50mm in length are added in RC beams with two different classes of concrete (i.e. two different compressive strengths of 30MPa (C30) and 50MPa (C50)). In order to determine the optimum percentage of SFs added to the concrete mix, 5 prisms and 30 cubes with 5 different percentages of SFs (i.e. 0%v/v, 0.5%v/v, 1%v/v, 1.5%v/v, and 2%v/v) from both C30 and C50 classes of concrete have been tested. Based on the results of the flexural strength and compressive strength tests, it is found that the optimum value is 1% of SFs by volume (i.e. 78.5 kg/m3). To investigate the flexural behavior of steel fiber added RC (SFARC) beams compared to conventional RC beams with no SFs, two RC beams with the dimensions of 170 mm in height, 120mm in width, and 2400mm in length, with SF percentages of 0 and 1%v/v and both having exactly the same steel reinforcement were tested under flexure using a four-point loading test setup for both C30 and C50 classes of concrete. The experimental results show that the SFARC beams with 1.0% by volume of SFs have higher first cracking strength, ultimate flexural strength, stiffness, and ductility compared to those conventional RC beams with no SFs. Furthermore, the addition of SFs has more effects on RC beams with higher compressive strength (50MPa) compared to lower concrete grade (30MPa)

Surficial and vertical distribution of heavy metals in marine and intertidal sediments in the Iranian sector of Gowatr bay

In order to identify natural and anthropogenic pollution in Gowatr bay (also gowadar bay), the distribution of heavy metals in the surface and different depths of marine and intertidal sediments was studied. For this purpose, 17 surficial sediment samples, and 5 sediment cores were collected, and compared with local background concentration. The results of surficial distribution of heavy metals indicate that maximum concentration of Copper and Zinc, Lead, and Nickel is related to Pasabandar harbor, sandy coast, and mudflats of Mangrove jungle, respectively. Calculated correlation coefficients indicate good positive correlation between Iron, clay fraction and potentially toxic metals, especially; Cu, Zn, Pb and Ni. Heavy metals distribution at depth was determined in five sediment cores. Sixty percent of sediment cores display surficial Pb enrichment, while Ni and Co are concentrated at depth. According to geo-accumulation factor (Igeo), zinc and copper show heavy contamination in Pasabandar harbor. Maximum PLI and RI are also related to Pasabandar harbor. Marine traffic, and ship yards activity at and close to Pasabandar harbor and mangrove jungle, along with weathering of ophiolites are apparently responsible for the observed elevated concentration of heavy metals in Gowatr bay

Effect of Polypropylene fibres on the Workability parameters of Extrudable Cementitious Material

Additive manufacturing in construction industry has been introduced as an aspiration for a more sustainable built environment and currently evolving with high demand amongst researches. This study is an investigation of the influence of polypropylene (PP) fibre addition on the workability parameters of a new extrudable concrete mixture. As the quality of final printed structure prominently depends on the fresh state properties of concrete, this investigation mainly focused on the rheological properties such as workability (flow), setting time, extrudability and buildability. These parameters were systematically investigated through a small scale experimental process with time after mixing. The selected control mix with Ground granulated blast furnace slag (GGBS) and Silica Fume (SF) was used in this analysis. The Control cementitious specimens without fibre inclusion and with fibre addition in different volume fraction of binder, ranging from 0.5% to 3% were printed. The results showed that the fibre addition of 0, 0.5 and 1.0% have the better flowability and extrudability compared to 1.5, 2 and 3%. Also, reduction in the print quality was assessed visually with increasing fibre percentage. However, results indicated that the initial setting time is comparatively low for those mixes with higher fibre inclusion which is required for better bond strength between layers. Moreover, higher fibre content caused better buildability and shape retention in the extruded samples