Corrosion of reinforcement is a serious problem and is the main cause of concrete structures deterioration costing millions of dollars even though the majority of such structures are at the early age ...of their expected service life. This paper presents the experimental results of damaged/repaired reinforced concrete beams. The experimental program consisted of reinforced concrete rectangular beam specimens exposed to accelerated corrosion. The corrosion rate was varied between 5% and 15% which represents loss in cross-sectional area of the steel reinforcement in the tension side. Corroded beams were repaired by bonding carbon fiber reinforced polymer (CFRP) sheets to the tension side to restore the strength loss due to corrosion. Different strengthening schemes were used to repair the damaged beams. Test results showed detrimental effect of corrosion on strength as well as the bond between steel reinforcement and the surrounding concrete. Corroded beams showed lower stiffness and strength than control (uncorroded) beams. However, strength of damaged beams due to corrosion was restored to the undamaged state when strengthened with CFRP sheets. On the other hand, the ultimate deflection of strengthened beams was less than ultimate deflection of un-strengthened beams.
Herein, ternary composites from polypyrrole (PPy), Mn0.8Zn0.2Fe2O4 (MZF), and graphite oxide (GO) were prepared to remove acid red dye (AR1) from wastewater. MZF was synthesized using spent Zn–C ...batteries, acid leaching, and sucrose auto-combustion processes; GO was prepared via oxidation and exfoliation of graphite. The composites were prepared by adding MZF and GO during the in-situ polymerization of pyrrole. Different PPy/MZF/GO (PMG) composites were prepared by changing the weight ratios of the PPy, MZF, and GO. We investigated the prepared composites’ structural, magnetic, and electrical/dielectric properties. We evaluated different experimental conditions’ influences on dye removal performance, such as pH, dosage, dye concentration, temperature, and contact time. XRD, FT-IR, and magnetic properties indicated that PPy completely coated the other contents. The electrical/dielectric properties improved while increasing the GO ratio. The PMG at GO content 50 wt.% (PMG50) showed the most efficient ratio for better removing AR1 from wastewater.
This paper presents the results of a study that investigated the properties of concrete made with dune sand. Different control concrete mixtures using ordinary Portland cement (OPC) with a minimum ...design compressive strength of 40
N/mm
2 were prepared. The amount of fine aggregates constituted about 36% by weight of all the aggregates. The workability ranged from low of 16
mm to a high of 122
mm. For each control mix, other mixtures were prepared in which the fine aggregates were replaced by different percentages of dune sand ranging from 10% to 100%. The effect of dune sand on the workability, compressive strength, tensile strength, modulus of elasticity and initial surface absorption test (ISAT) was studied. Experimental results show an improvement in the workability of concrete when fine aggregates were partially replaced by dune sand. An increase in slump was measured with increase in dune sand content. However, at high dune sand contents (above 50%); the slump starts to decrease with an increase in dune sand. Generally, the strength values decrease with increase in dune sand replacement. The strength loss was not found considerable as the maximum reduction was less than 25% when fine aggregates were fully replaced by dune sand. The absorption characteristics of concrete made with OPC as measured by the (ISAT) generally increased with higher dune sand contents.
This study describes the use of banana peel (BPEs) and date seed extracts (DSEs) as waste products in the sustainable and eco-friendly biological synthesis of zinc oxide nanoparticles (ZnONPs). ...ZnONPs_BPE and ZnONPs_DSE were characterized using an ultraviolet-visible spectrophotometer (UV-VIS), Scanning (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential analysis, and Fourier transform infrared (FTIR) spectroscopy. Moreover, the biocompatibility of ZnONPs was analyzed against the normal human skin fibroblast (HSF) cell line. Peaks of UV spectra were 300 nm and 400 nm for ZnONPs-BPE and for ZnONP _DSE, respectively, confirming the ZnONPs’ formation. XRD revealed their hexagonal structure. SEM showed the nanocrystals of ZnONPs_BPE, which are interlinked to one another in a uniform shape, while ZnONPs_DSE appear as large and small chunky crystals. The mean size of ZnONPs_BPE and ZnONPs_DSE was 50 nm and 62 nm using TEM, respectively. On the contrary, their mean size was bigger using DLS with the zeta potential of ZnONPs_BPE = −12.7 mV and ZnONPs_DSE = −5.69 mV. The FTIR analysis demonstrated the presence of carboxyl, hydroxyl, and C–H of cellulose, hemicelluloses, and lignin polymers on ZnONPs surfaces that act as reducing, capping, and stabilizing agents. ZnONPs_BPE (IC50 > 100) have lower cytotoxic effects on HSF cells than ZnONPs_DSE (IC50 = 29.34 μg/mL). The present study indicates the successful synthesis of ZnONPs using agro-wastes that could help in waste management and recycling. Furthermore, ZnONPs_BPE is safe to use for further applications.
The main objective of this study is to determine the optimum size of systems able to fulfil the electrical energy requirements of remote sites located in Hajer Bani (HB) Hameed in the North of Oman, ...Masirah Island and the Mothorah area in the South of Oman. The methodology applied provides a useful and simple approach for sizing and analysing the hybrid systems using Hybrid Optimization Model for Electric Renewables (HOMER). The aim is to identify a configuration among a set of systems that meet the desired system reliability requirements with the lowest energy cost. The results of the analysis are a list of feasible power supply systems, classified according to their net present cost. Actual hourly load data are taken from these sites and are used in the model, and the meteorological readings are used either from the same site or from a nearby one. A comparison between the costs of electricity generated from renewable energy resources in these locations is done and the payback period for renewable energy components is calculated. Moreover, the effects of the temperature on the photovoltaic cells efficiency and energy cost are considered. The cost of energy was found to be 0.206, 0.361 and 0.327 $/kWh for Masirah Island, Mothorah and HB Hameed, respectively.
The Albian Kharfot Formation is preserved in the eastern margin of the Jeza-Qamar Basin which straddles across the Oman–Yemen border. This study addresses the sedimentological attributes of the ...formation and deduces its depositional setting, cyclicity and relative sea level changes in local (within the basin) and regional (Arabian) contexts. The interaction among siliciclastic influxes, in-situ carbonate production and tectono-climatic controls on the stacking nature of the various lithofacies that build-up the formation is discussed. In the study area, the formation lies unconformably over Barremian–Aptian Qishn Formation and conformably under late Albian–?Turonian Dhalqut Formation. The Kharfot Formation thickens from ~140m in the eastern side of the study area to ~300m at the Oman–Yemen border. It consists of eight lithofacies: Orbitolina-rich marls, peloidal bioclastic packstone, bioclastic mudstone to wackestone, argillaceous, bioclastic floatstone to rudstone, bioclastic rudstone, sandy, peloidal, bioclastic mudstone to packstone, peloidal, bioclastic grainstone and dolostone. The vertical arrangement of these lithofacies defines recurring meter- to decameter-scale, shallowing-upward units deposited on a westward-deepening inner- to outer-ramp setting. Tectonic rejuvenation of the siliciclastic source area was accompanied by warm, humid climatic conditions as suggested by high kaolinitic marls of the Kharfot Fm. and coeval quartz-rich sandstone units (Harshiyat Fm.). The shallowing-upward rhythmic sedimentation of the formation has close resemblance with cycles of the Nahr Umr Formation in northern Oman and partially comparable with the global sea level changes. The Kharfot basin was an intrashelf depression that was part of the much larger Arabian epeiric platform. The latter is defined by a rimmed margin in northern Oman where Al-Hassanat Formation represents platform margin deposits and Nahr Umr Formation representing back-rim intrashelf depression which received fine-grained siliciclastic influx from the land (westward). In southern Oman where Kharfot Formation accumulated, the platform was unrimmed ramp type basin with high fine clastic influx along with elevated carbonate production.
•Lithofacies and depositional environment of the Albian Kharfot Formation, Oman.•Concurrent siliciclastic and carbonate deposition within regional (Arabian) context.•Cyclicity, tectono-eustatic fluctuations and their effect on basin-fill architecture.
A controlled low strength material (CLSM) is a self-compacted, cementitious material used primarily as a backfill. It is also known as a flowable fill which is usually a mixture of fine aggregates, ...small amount of cement, fly ash, and water. To be classified as a CLSM, the mixture must have a compressive strength between 345 and 8400
kPa. This paper evaluates the potential use of cement by-pass dust, incinerator ash and copper slag as a CLSM. Mixtures were designed to produce a CLSM, with a low compressive strength (less than 1034
kPa), that can be excavated without using any mechanical equipment. Slump, unit weight and unconfined compressive strength tests were conducted on various mixtures. Cubical and cylindrical specimens were prepared and cured at room temperature and in sealed plastic bags. Results indicate that with a good mix design it is possible to produce a CLSM with good mechanical properties to meet design requirements. Mixing these materials with cement and sand produced better results than using them alone due to their low pozzolanic activity. Curing method and period can have considerable effects on the strength of a CLSM.
Ferrochrome slag (FCS) possesses promising properties that promote its use as an alternative to natural aggregates in concrete production. Still, there is a concern about the effect of ...high-temperature exposure on the properties of concrete containing FCS aggregate. Therefore, due to durability and structural fire safety, it is necessary to evaluate the properties of FCS concrete after being exposed to elevated temperatures. The present study investigates the effect of FCS fine aggregate on the physical and mechanical properties of concrete at room and elevated temperatures (i.e., 200−1000 °C). Microstructural properties at high temperatures were also evaluated using SEM-EDS analysis. The results showed an improvement in the mechanical properties of concrete with FCS fine aggregate compared to conventional concrete. After being exposed to high temperatures, the concrete containing FCS fine aggregate showed less reduction in strength properties and mass than conventional concrete. Such improvements in mechanical and physical properties are achieved due to the chemical composition and surface texture of the FCS aggregate. Microstructural observation and ultrasonic pulse velocity confirmed that FCS concrete suffered less damage upon exposure to high temperatures. Furthermore, the effect of high temperatures on the strength properties of FCS concrete is consistent with the recommendations of the codes (Eurocode 2 and ACI 216.1).
The World Health Organization estimated that in 2011 worldwide 1.6 billion adults were overweight, and 400 million were obese. The obesity epidemic is a documented phenomenon and Oman is no ...exception. The aim of this study was to determine the effect of obesity on pregnancy and its prenatal and neonatal outcomes. Methods: A prospective cohort study was carried out among pregnant Omani women attending antenatal clinics in their first trimester in the Seeb province of Muscat, Oman. Results: A total of 700 pregnant women were enrolled in the study and were categorized according to their body mass index: 245 (35%) were normal weight, 217 (31%) were overweight, and 238 (34%) were obese. The relative risk (RR) of cesarean section among obese women compared to women of normal weight was 2.1 (95% confidence interval (CI) 1.2-3.2) and of overweight women was 1.4 (95% CI 0.9-2.3). The risk of elective cesarean section increased to 7.5 (95% CI 1.7-32.8) in obese women and was statistically significant in the obese group. In this study, 100 women (15.7%) developed gestational diabetes (11.8% of normal weight women, 17.8% of overweight women, and 17.9% of obese women). Miscarriages were more common among obese women 11.9% (n = 27) compared to the normal weight and overweight groups (6.7% and 9.4%, respectively). There was a weak yet statistically significant correlation between birth weight and body mass index. The risk of macrosomia was significantly higher in obese women compared to normal weight women. To evaluate the sensitivity of the oral glucose challenge test (OGCT), the oral glucose tolerance test (OGTT) was measured in 203 participants (29%) who had a normal OGCT result. It was found that 14.5% of overweight women and 13.5% of normal weight women had an abnormal OGTT result even when their OGCT result was normal. Conclusions: Obesity is associated with an increased risk of cesarean section (especially elective cesarean), gestational hypertension, macrosomia, and miscarriage. It also increases the risk of gestational diabetes.
Presence of antibiotic resistant bacteria as bio-indicators of pollution was monitored in fish (colons and gills) and in sewage treated effluent (STE) in two marine sites in the Gulf of Oman, Muscat. ...One site was polluted as the sewage effluent STE was directly discharged into the sea while the unpolluted site was 10
km away. A total of 42 water samples (250
mL each) were collected from both sites. In the polluted site, 14 samples were taken directly from the STE discharge point and 14 from the surrounding area near the STE discharging point (7–10
m). Water and fish samples were collected from polluted and unpolluted sites. Chlorine and nitrate levels were significantly higher in STE samples. A significant difference (
P
<
0.005) was found in total bacterial count of fish colon and gills in the two sites. Most probable number (MPN) was significantly higher in STE and polluted seawater over unpolluted. Coliforms were detected in the polluted site only. A total of 320 target enteric normal flora of animals and pathogenic species were isolated from 10 genera taken from water and fish samples. The isolates were exposed to 14 antibiotics. Most of the isolates were resistant to at least one antibiotic with ampicillin was the dominant antibiotic. This is a clear indication that sewage effluent causes contamination of marine wildlife along coastal lines.
PDF
