Shear Strength of Self-compacting Concrete Containing Different Fillers and Coarse Aggregates

An experimental investigation was conducted to evaluate the shear strength provided by different self-compacting concrete mixes proportioned using different fillers and coarse aggregates. A total of 28 simple beams without web reinforcement were tested in flexure. The test parameters included the use of gravel versus crushed dolomite as coarse aggregates, the amount of longitudinal reinforcement and the composition and percentage of fillers. Dolomite stone powder with either silica fume or fly ash were used as fillers replacing cement aiming at reducing the cost of the mix and obtaining better performance. The test results indicated that the overall structural performance in terms of cracking pattern and shear strength was comparable in all mixes. The potentials of developing shear strength and post cracking shear resistance were better when gravel was used as coarse aggregate and when relatively high fractions of dolomite powder were used as cement replacement

Behaviour of Fiber Reinforced Concrete Beams with Spliced Tension Steel Reinforcement

The aim of the current work is to describe the flexural and bond behaviour of simply supported concrete beams with tension reinforcement spliced at mid-span. The parameters included in the study were the type of the concrete, the splice length and the configuration of the hooked splice. Fifteen beams were cast using an ordinary concrete mix and two fiber reinforced concrete mixes incorporating steel and polypropylene fibers. Each concrete mix was used to cast five beams with continuous, spliced and hooked spliced tension steel bars. A test beam was reinforced on the tension side with two 12-mm bars with a splice length of 20 and 40 times the bar diameter. The hooked bars were spliced along 20 times the bar diameter and provided with 45-degree and 90-degree hooks. The test results in terms of cracking and ultimate loads, cracking patterns, ductility, and failure modes are reported. The results demonstrated the consequences due to short splices and the improvement in the structural behaviour due to the use of hooks and the confinement provided by the steel and polypropylene fibers

Influence of Different Drying Conditions on High Strength Concrete Compressive Strength

The influence of different drying conditions on the compressive strength and strength development rates of high strength concrete up to an age of 28 days was evaluated. Two HSC mixes with and without silica fume addition were used to cast cubes of 10 cm size. The cubes were stored in different drying conditions until the age of testing at 3, 7, 28 days

Experiments with Externally Prestressed Continuous Composite Girders

Steel-concrete composite girders have attractive potentials when applied in bridge construction. The serviceability performance of continuous composite girders is becoming more and more a deterministic parameter in the design of this type of structures. An effective method for improving this performance is to apply prestressing to control or completely eliminate concrete deck cracking caused by static and time dependent actions. Little literature has been found addressing the experimental analysis of continuous girders prestressed by means of external deviated tendons. The current research aims to investigate the behavior of a double-span steel composite beam externally prestressed by means of continuous tendons in terms of cracking characteristics, load deflection response, and load carrying capacity. The efficiency of prestressing is evaluated by comparing the results to those of a non-prestressed beam with similar cross sections and spans

The role of varicocele sclerotherapy in men with severe oligo-astheno-teratozoospermia

The aim of this study was to verify the role of antegrade scrotal sclerotherapy for the treatment of varicoceles in infertile men with severe oligo-astheno-teratozoospermia (OAT). The 59 patients with severe OAT in this study underwent antegrade scrotal sclerotherapy for the treatment of varicoceles. The outcome was assessed in terms of improvement in semen parameters and spontaneous conception rate. Semen parameters and reproductive hormones were evaluated before antegrade sclerotherapy (AS) and 6 months after AS. After an average follow-up time of 34.83.2 months, significant improvement was noted in the mean sperm concentration, motility and morphology in 36 patients (61%). Spontaneous pregnancy occurred in nine couples (15%). Six months after treatment, inhibin B levels were significantly higher (P<0.04), whereas follicle-stimulating hormone (FSH) levels were significantly lower (P<0.001) than before treatment. Antegrade internal spermatic vein sclerotherapy can significantly improve seminal parameters and hormonal parameters in men with severe OAT and may even result in spontaneous pregnancy in couples who would otherwise be candidates for intracytoplasmic sperm injection (ICSI)

Experimental Evaluation of Steel–Concrete bond Strength in Low-cost Self-compacting Concrete

The main objective of this research was to evaluate the potentials of self-compacting concrete (SCC) mixes to develop bond strength. The investigated mixes incorporated relatively high contents of dolomite powder replacing Portland cement. Either silica fume or fly ash was used along with the dolomite powder in some mixes. Seven mixes were proportioned and cast without vibration in long beams with 10 mm and 16 mm steel dowels fixed vertically along the concrete flow path. The beams were then broken into discrete test specimens. A push-out configuration was adopted for conducting the bond test. The variation of the bond strength along the flowing path for the different mixes was evaluated. The steel-concrete bond adequacy was evaluated based on normalized bond strength. The results showed that the bond strength was reduced due to Portland cement replacement with dolomite powder. The addition of either silica fume or fly ash positively hindered further degradation as the dolomite powder content increased. However, all SCC mixes containing up to 30% dolomite powder still yielded bond strengths that were adequate for design purpose. The test results demonstrated inconsistent normalized bond strength in the case of the larger bar diameter compared to the smaller one

Reductive Precipitation of Selenite in Water Using Sodium Sulfide

Selenium (Se) is an essential trace element to humans and animals due to its function as an antioxidant and catalyst for the production of active thyroid hormone. However, it is toxic at high concentrations, which can cause diseases and death to humans. Selenium is released to the environment from sewage sludge and industrial facilities such as mining, oil and gas processing, power generation, coal combustion, metals and petrochemical industries. Selenium removal from contaminated wastewaters is necessary due to its toxicity and potential harm to human health and the environment. Selenium can be removed from wastewaters using biological or chemical/physical processes. However, each of these processes has its own limitation. For example, biological treatment of selenium requires several hours of hydraulic residence time and chemical/physical processes either produces unstable selenium-bearing residuals or concentrated liquid waste byproduct. Reductive precipitation of selenium is an attractive process because it can convert the soluble forms of selenite and selenate to insoluble elemental selenium. This study investigates selenite (Se(IV)) removal from water via reductive precipitation using sodium sulfide at neutral pH. Also, this study investigates the effect of UV light irradiation as an activation method to enhance Se(IV) reduction. Analysis of precipitated solids using XPS, SEM, and XRD indicated that Se(IV) was reduced to elemental Se or solids composing of Se and sulfur (S) (e.g. SenS8-n). High-resolution S 2p spectra suggested the presence of sulfur oxyanions, monosulfide (S^2-), polysulfides (Sn^2-), and elemental sulfur. SEM images showed large irregular aggregates that were dominant at acidic pH than neutral pH, and they were more noticeable in the presence of UV light. Additionally, it was observed from XRD patterns that elemental selenium (layered plate shape) was dominant in the absence of UV light. Whereas, cyclic Se-S precipitates (Se3S5) with orange color were dominant in the presence of UV light. Selenite was effectively removed at neutral pH, regardless of the presence of UV light. UV light did not enhance Se(IV) removal at tested conditions, but it affected the solid morphology and its composition. Complete removal of selenite was achieved in less than five minutes at sulfide dose to initial Se(IV) molar ratios above 11.5