Effect of Different Factors on the Service Life of Concrete Structures in Chloride Environments: A Parametric Study – Part One

This paper presents a comprehensive parametric study to determine the effect of different factors on the service life of reinforced concrete structures in chloride-laden environment. A model for corrosion initiation is selected and solved numerically by Finite Element Method for one-dimensional diffusion problem. It has been found that increase in water to cement ratio by 12.5%-50% in range of 0.20-0.40reduces the service life by 8%-35%, and by 7.35%-30.5% for the range 0.40-0.60. Also, the increase in concrete cover in the range of 20-35 mm by 14%-42%increases the service life by 8.1%-25.8%, and in the range of 35-60 mm by 7.7%-21.8%.Regarding mineral admixtures, the addition of fly ash and blast-furnace slag resulted in enhances the service life by 8%-70.7% due to increase of age factor by 25%-200%. Moreover,the addition of silica fume by 5%-15% increases the service life by 25.5%-80.6%.Finally, the rise of temperature by 25%-75% reduces the service life by 6.45%-18.7%, and the reduction of relative humidity by 25%-50% increases the life by 21.2%-89%. These values are based on a conservative approach and tend to guide the practice engineer on how these parameters affect service life of concrete structures

Effect of Different Factors on the Service Life of Concrete Structures in Chloride Environment: A Parametric Study - Part Two

In this paper, the effect of different factors on the service life of reinforced concrete structures in marine environments is investigated through a parametric study. The considered case for the study was the two- dimensional diffusion problem. By solving the selected model for corrosion initiation by Finite Element Method, it has been concluded that, corrosion initiates at corner bars before side bars. Also, concrete elements subjected to two-dimensional diffusion are more susceptible to corrosion initiation than elements subjected to one-dimensional diffusion. Moreover, increase in water to cement ratio by 12.5%-50% in range 0.20-0.40 reduces the service life by 6.2%-31%, and by 5.3%-16.9% for the range 0.40-0.60. And, the increase in concrete cover in the range of 20-40 mm by 12.5% - 50% increases the service life by 5.1%-18.8%, and in the range of 35-60 mm by 2.9%-10.3%. The addition of fly ash and blast-furnace slag increased the service life by 6.35%-69.7% due to increase of age factor by 25%-200%. Furthermore, the addition of silica fume by 5%-15% increases the service life by 21.7%-81.2%. Regarding the environmental factors, increasing of temperature by 25%-75% reduces service life by 4.7%-12.75%, and reducing of relative humidity by 25%-50% increases the life by 17.5%-90.4%.are also given

Effect of Changing Properties of Wythes in Precast Structural Sandwich Panels

This study investigates the effects of changing in the properties of face and core wythes in structural sandwich panels (with dimensions of 500 500 mm and 120 mm total height). Concrete face wythes of three grades (80, 70, 37) MPa, thicknesses of (25, 35, and 45) mm, and three types of core materials (high density foam, polyethylene foam, and palm bark) were used in the production of panels. Steel shear connectors were installed in the panels with angle of 45º. Three-point bending load test was carried out on all panels and results were compared with both of the theoretical extremes capacities of non- composite and fully-composite states and ANSYS software results. The degree of composite action (%) and the (strength/weight) ratio were the main parameters that judged the specimens. It was found that upgrading concrete increased overall strength of slabs especially in high strength concrete (80 MPa), however the use of lightweight concrete (70 MPa) caused high (strength/weight) ratio due to very lightweight. Results revealed that decreasing thickness of concrete face wythes had a positive effect on strength/weight ratio (although the ultimate loads decreased) that enhanced the performance of panels as lightweight structural panels. The optimum face wythe thickness is that of 2.5 cm and has high (strength/weight) ratio. It was noticed that adding polyethylene foam as a core material results in positive effect and high (strength/weight) ratio. Results revealed that high strength concrete (80 MPa) and light-weight concrete (37 MPa) are very successful in the production face wythes of precast light-weight sandwich panels that can obtain high (strength/weight) ratio and high percent of composite action

Performance of Bio Concrete by Using Bacillus Pasteurii Bacteria

In concrete, cracking is a common phenomenon due to its relatively low tensile strength‎ ‎, which occurs due to external loads and imposed deformations‎‎. The main research objective is to create a kind of self-healing concrete by employing mineral producing bacteria Bacillus pasteurii‎ to locate the rift in the most favourable circumstances for autogenous healing to take place. Self-healing concrete containing bacteria has been generated for this study through the application of bacterial self-healing elements as ‎spores ‎and nutrients with different percentages of bacteria ranging from (10% - 25%) as a replacement of mixing water is added at the time of pouring. The bacteria influence was observed by Scanning Electron Microscope (SEM) and with Energy ‎Dispersive X-ray Spectrometer. The mechanical properties and durability of a thirty-five mixture were ‎examined. The optimal blending content proportion was ‎10SF20BC, which showed an increment in compressive strength and flexural strength compared to the control mixture ‎to ‎reach 79.16%, 50% respectively and 24.38% enhancement in sulfate resistance. The highest percentage of calcium carbonate precipitations was ‎9.49% of a weight of ‎mixtures ‎elements, which, in turn, revealed the highest area repair rate, which was able to fill the ‎crack with widths leads to 0.80 mm

Behavior of Beam to Column Cold-Formed Section Connections Subjected to Bending Moments

Cold formed sections are often used in the construction of mid-rise buildings due to their high strength weight ratios, and fast erection. In these buildings, the connections between joists and studs are mainly simple connections. However, application of these sections can be extended to moderate span frames where connections between members are subjected to bending moments. Strength and stability of such frames depends to large extent on the behaviour of the connections between their members. Over the last twenty years, several researchers undertake tests on cold formed section connections subjected to bending moments. Major of them classify the connections as semi-rigid, but some suggested that as we reach the maximum capacity of the connected sections so we can consider it rigid

Microbial Infections in Immunodeficient Children in Qena University Hospital with Special Reference to DNA Damage in Peripheral Blood Leucocytes

Background: Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual, Impair the immune system's ability to defend the body against foreign or abnormal cells that invade or attack it (such as bacteria, viruses, fungi, and cancer cells). As a result, unusual bacterial, viral, or fungal infections or lymphomas or other cancers may develop. Patients and methods: A study to detect blood stream infections was done using 100 blood cultures obtained from 100 immunocompromised children. Results and conclusions: The most commonly isolated are bacterial organism (40 %)the most common bacterial isolates are klebsiella species (17 | 40 ,42.5%). Estimation of DNA damage was done for 40 patients and 10 apparently healthy children as control subjects. The DNA damage was detected has took the smear shape on gel electrophoresis. This was found in (12|40, 30%), (P value < 0.001) with significant difference

Origin of Amphibole-Biotite-Fluorite-Rich Enclaves from Gabal El-Ineigi Fluorite-Bearing Granite, Central Eastern Desert of Egypt: Insights into Fluoride-Calcium and Silicate Liquid Immiscibility

Gabal El-Ineigi fluorite-bearing rare-metal granite with A-type affinity, located in the Central Eastern Desert of Egypt, is distinguished by its abundance of large fluorite-quartz veins and mafic enclaves. Plagioclase (labradorite to oligoclase), Mg-rich biotite, and Mg-rich hornblende are the main components of mafic enclaves, with significant amounts of fluorite as essential phases, and titanite and Fe-Ti oxides (Nb-free rutile and ilmenite-rutile solid solution) as the main accessories. These enclaves are monzodioritic in composition, Si-poor, and highly enriched in Ca, Fe, Mg, and F compared to the host alkali feldspar F-poor Si-rich granites. Given the conflicting evidence for a restitic, xenolithic, magma mixing/mingling, cumulate, or bimodal origin for these enclaves, we propose that the mafic enclaves and felsic host granites are two conjugate liquids, with contrasting compositions, of a single parental melt. This is inferred by the normalized REE patterns that are similar. As a result, liquid immiscibility is proposed as a probable explanation for this mafic&ndash;felsic rock association. These enclaves can be interpreted as transient melt phases between pure silicate and calcium-fluoride melts that are preserved from the early stages of separation before evolving into a pure fluoride (Ca-F) melt during magma evolution. Due to element partitioning related to melt unmixing, the enclaves are preferentially enriched in Ca, F, Li, Y, and REE and depleted in HFSE (such as Zr, U, Th, Ta, Nb, Hf, and Ga) in comparison to the host granites. Furthermore, mafic enclaves exhibit W-type tetrad effects, while host granites exhibit M-type tetrad effects, implying that the REE partitioning, caused by liquid immiscibility, is complementary

Review of the utilization of HEEPF – competitive projects for educational enhancement in the Egyptian medical sector

In Egypt, the medical sector has been facing the same problems that challenged the system of higher education in the past decades, mainly an increasing student enrollment, limited resources, and old governance and bylaws. These constraints and the escalating paucity of resources have had a major negative influence on quality of education. Consequently, thoughts of educational reform came forward in the form of competitive projects, which have attracted several institutes from the health sector to improve their educational performance. The aim of this paper is to review the share of the medical sector in the higher education enhancement project fund (HEEPF), its outcomes, sustainability, and to provide recommendations for keeping the momentum of reform pursuit in the future. The methodology included obtaining statistics pertaining to the medical sector in Egypt as regards colleges, students, and staff. We also reviewed the self-studies of the medical sector colleges, HEEPF projects reports, performance appraisal reports, and World Bank reports on HEEPF achievements in order to retrieve the required data. Results showed that medical sector had a large share of the HEEPF (28.5% of projects) as compared to its size (8% of student population). The projects covered 10 areas; the frequency distribution of which ranged between 4.4% (creation of new programs) to 97.8% (human resource development). In conclusion, educational enhancement in the medical sector in Egypt could be apparently achieved through the HEEPF competitive projects. A study of the long-term impact of these projects on the quality of education is recommende

Investigation of the Ameliorating Effect of Copper Albumin Complex on Lysyl oxidase in monosodium iodoacetate -Induced Knee Osteoarthritis in Rats

Knee osteoarthritis (KOA) is a common type of joint degeneration which causes progressive damage of the joint structure and has less therapeutic options. It has been found that oral consumption of Copper Albumin Complex as anti-inflammatory drug has a positive effect on the treatment of joint deterioration. The present study aimed to investigate the effect of oral administration of Copper Albumin Complex (cu-albumin complex) on Lysyl oxidase (LOX) which acts as a protective factor in KOA. Fifty adult albino rats were divided into 3 groups: negative control (10 normal rats); positive control (20 rats with KOA which left without induction treatment); and treated group (20 rats with KOA which treated with administration of copper albumin complex). Treated and untreated arthritic groups were subdivided equally into mild and severe groups (10 rats for each) according to the severity of clinical signs. KOA was induced by intra-articular injection of monosodium iodoacetate (MIA). At the experimental end, the joints were examined histopathologically and immunohistochemically after cervical dislocation of rats. It was observed that the treatment with CU- was effective in reducing disease severity and in improvement of Lysyl oxidase KOA. It was concluded that Copper albumin complex has a positive effect in the improvement of LOX of Knee joint cartilages of rats affected by osteoarthritis (OA)

In ovo protective effects of chicoric and rosmarinic acids against Thiacloprid-induced cytotoxicity, oxidative stress, and growth retardation on newly hatched chicks

Thiacloprid (TH) is a neonicotinoid insecticide employed in agriculture to protect fruits and vegetables against different insects. It showed different deleterious effects on the general health of non-target organisms including birds and animals, however, its developmental toxicity has yet to be fully elucidated. Chicoric (CA) and rosmarinic (RA) acids are polyphenolic compounds with a wide range of beneficial biological activities. In this study, the possible protective effects of CA and RA were investigated in chick embryos exposed in ovo to TH (1mg/egg) with or without CA (100 mg/egg) or RA (100 mg/egg) co-exposure. TH reduced the hatchling body weight, body weight/egg weight, and relative weight of bursa of Fabricius in the one-day-old hatchlings. Examination of the 7-day-old chicks revealed a decline in feed intake, daily weight gain, feed conversion ratio (FCR), and plasma levels of T3, T4, and growth hormone. Serum ALT, AST activities, and total cholesterol levels showed significant elevations. Hepatic MDA was increased with a reduction in SOD activity and GSH level and downregulation of the liver SOD and GST gene expression pattern. Serum IgG and IgM levels were reduced, and various histopathological alterations were noticed in the liver. Co-administration of CA or RA with TH mitigated the toxic effects on hatchlings. When both CA and RA are combined, they present a synergistic protective effect. CA and RA can be used as protective agents against TH toxicity as they improve growth performance and have hepatoprotective and immunostimulant effects in newly hatched chicks