Homogeneous Flow Performance of Steel-Fiber Reinforced Self-Consolidating Concrete for Repair Application: A Biphasic Approach

In this study, fiber-reinforced self-consolidating concrete (FR-SCC) was considered as a diphasic suspension of fiber and coarse aggregate (F-A ≥ 5 mm) skeleton in mortar suspension with solid particles finer than 5 mm. The coupled effect of the volumetric content of fibers, coarse aggregate particle-size distribution, and rheological properties of the mortar on the passing ability and dynamic stability of various FR-SCC mixtures was investigated. Nine high-strength and 10 conventional-strength FR-SCC mixtures for repair application were proportioned with water-to-binder ratios (W/B) of 0.35 and 0.42, respectively, and macro steel fibers of 0.1%–0.5% volumetric contents. The dosages of high-range water-reducer (HRWR) admixture were optimized to achieve a targeted slump flow of 680 ± 20 mm. The yield stress and plastic viscosity of the mortar mixtures varied between 4.6-17.7 Pa and 2.8–8.2 Pa s, respectively. Flow performance of the investigated mixtures were evaluated in terms of flowability (slump-flow test), passing ability (J-Ring and L-Box set-ups), and dynamic stability (T-Box test). According to the established correlations, the main influencing parameters on homogeneous performance of FR-SCC include W/B, paste volume, volumetric content-to-packing density of F-A (φ/φmax), HRWR dosage, fiber content, mortar rheology, and volume of excess mortar. The robustness analyses results revealed that homogeneous flow performance of FR-SCC is more sensitive due to variations of the φ/φmax and paste volume rather than mortar rheology, W/B, and HRWR dosage. The characteristics of the mixture constituents for FR-SCC mixtures with different strength levels were finally recommended to ensure acceptable homogeneous performance under restricted flow conditions of repair application

Homogenous Flow Performance of Steel Fiber-Reinforced Self-Consolidating Concrete for Repair Applications: Developing a New Empirical Set-Up

In this study, a new empirical Square-Box test was employed to evaluate the homogeneous flow performance of fiber-reinforced self-consolidating concrete (FR-SCC) under confined-flow conditions that are typical of repair applications. The Square-Box set-up consisted of a closed-circuit box, providing 2.4-m flow distance and a closed-surface cross section of 100-mm width and 200-mm height, equipped with 0 and 4 rows of reinforcing bar grids with 45-mm clear spacing. The flow performance was assessed in terms of dynamic stability and passing ability. The investigated mixtures were considered as diphasic suspensions of fiber-coarse aggregate (F-A \u3e 5 mm) in suspending mortars containing particles finer than 5 mm. According to the experimental results, the dynamic segregation and blocking indices of the investigated mixtures were found in good agreements with characteristics of F-A combination and rheology of mortar. The investigated mixtures exhibited significantly higher blocking indices through the Square-Box set-up compared to those obtained using the L-Box test. Furthermore, the characteristics of F-A and rheology of mortar showed opposite effects on dynamic segregation assessed using Square-Box and conventional T-Box set-ups. Under confined flow conditions, higher dynamic segregation led to more dissimilar compressive strength values at different flow distances through the proposed Square-Box set-up. A new filling ability classification was established based on the experimental dynamic stability and passing ability results of the proposed empirical test

Coupled Effect of Fiber and Granular Skeleton Characteristics on Packing Density of Fiber-Aggregate Mixtures

The addition of fiber to cementitious materials enhances mechanical performance but can reduce workability of the fiber-reinforced concrete (FRC) mixtures. This can be due to the negative effect of fibers on packing density (PD) of the fiber-coarse aggregate (F-A) combination. The performance of FRC, as a diphasic suspension, is dependent on the characteristics of both F-A (suspended-solid skeleton) and mortar (suspending liquid) phases. PD can reflect the voids within the F-A skeleton to be filled with mortar. An adequate optimization of the characteristics of the F-A skeleton can modify the performance of FRC in fresh and hardened states. The F-A skeleton can be characterized in terms of particle-size distribution, volumetric content, and morphology of the coarse aggregate, as well as size, rigidity, and content of fibers. In this study, a comprehensive investigation was undertaken to identify the coupled effect of the characteristics of fibers and coarse aggregate on the PD of F-A combination used without any cement paste/mortar. The solid components play a key role in the overall performance of the concrete produced. This study was carried out to optimize the F-A combination and enhance the workability design of FRC. Various types of steel, polypropylene, and polyolefin fibers having different sizes and rigidities were investigated. Moreover, four combinations of three different classes of coarse aggregate were used to proportion F-A mixtures. Test results showed that shorter length, smaller diameter, and more flexible fibers can lead to higher PD of F-A systems. Moreover, the coarser aggregate skeleton with larger interparticle voids led to more available length for fibers to be deformed, hence improving the PD of F-A mixtures. New empirical models were proposed to predict the packing density of F-A combinations given the characteristics of coarse aggregate and fibers, as well as the level of compaction. The established models were employed to propose a new proportioning approach for fiber-reinforced self-consolidating concrete mixtures to achieve the targeted workability

Novel Tri-Viscous Model to Simulate Pumping of Flowable Concrete through Characterization of Lubrication Layer and Plug Zones

In this study, computational fluid dynamics (CFD) was employed to simulate the pipe flow of 18 self-consolidating and four highly workable concrete mixtures in a 30-m long pumping circuit. Pressure loss (ΔP) in 100- and 125-mm diameter (DP) pipelines was measured under low (1.2–6.2 l/s) and high (8.1–16.4 l/s) flow rates (Q). The numerical simulation was successfully carried out using a two-fluid model and a new variable-viscosity single-fluid approach, namely double-Bingham and tri-viscous models, respectively. The radial variation of rheological properties of the concrete across the pipe section, representing the plug flow, sheared concrete, and lubrication layer (LL) zones was successfully simulated based on a total of 404 pipe flow experiments. The relative LL viscous constant (ηLL) values obtained using numerical simulations-to-those obtained experimentally using a tribometer ranged between 30% and 200%. Moreover, the coupled effect of the characteristics of different flow zones, DP, and Q on ΔP was evaluated

POSTPARTUM ELEVATED Β-HYDROXYBUTYRATE AND NON-ESTERIFIED FATTY ACIDS TOGETHER OR SEPARATELY AND THEIR ASSOCIATION WITH PLASMA METABOLITES, BODY CONDITION AND REPRODUCTIVE PERFORMANCE IN DAIRY COWS

This study aimed to assess post-partum elevated nonesterified fatty acids (NEFA) and β hydroxybutyrate (BHB), considered either togetheror separately,relative to the estrus cyclicity and first service pregnancy status of cows and their association withbody condition scores and some metabolites.Blood samples from 50 Montbéliarde dairy cowswere collected from 15 to 52 DIMto measure serum  BHB, NEFA,glucose, triglycerides, total cholesterol, urea nitrogen, total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyltransferase (γGT), calcium, magnesium, potassium, phosphorus, sodium;and progesterone concentrations.Body condition score (BCS) was assessed at calving and at each time when blood samples were taken.Cows were considered as having post-partum elevated NEFA (H-NEFA) concentration if the concentration was≥0.70 mM and post-partum elevated BHB (H-BHB) concentration if the concentration was≥1.20 mM at 30 DIM. Overall, 93.33 % of cows having an elevated BHB show an elevated of NEFA and 51.61% of cows having an elevated NEFA have not an elevated BHB. Indeed, considering postpartum elevated NEFA as a predictor of sub-clinical ketotic cows can overrateresults. Whereas, considering postpartum elevated BHB as a predictor of cows with NEB can underestimate results. Excessive BCS at calving results in increasing the risk of post-partum elevated BHB. Cholesterol, triglycerides, AST, ALT, and urea were increased in cows having elevated BHB and NEFA compared with those having elevated NEFA only or healthy cows. Further, the risk of estrus cyclicity and pregnancy rate at first insemination (P/AI) was decreased in cows having both elevated BHB and NEFA or NEFA only

Discrete-Element Modeling of Shear-Induced Particle Migration during Concrete Pipe Flow: Effect of Size Distribution and Concentration of Aggregate on Formation of Lubrication Layer

The Paper Seeks to Better Understand the Particulate Mechanics Giving Rise to the Lubrication Layer (LL) in Flows with Wide Particle-Size Distributions (PSD) Typical of Concrete Pumping Applications. the Study Uses a Soft-Sphere Discrete Element Method (DEM) to Simulate the Shear-Induced Particle Migration (SIPM) Mechanism of Formation of the LL. to Provide Realistic Understanding of SIPM and Rheological Heterogeneity of Concrete, Three Wide PSDs (Fine, Medium, and Coarse) and Three Different Concentrations (10 %–40 %) of Five Spherical-Particle Subclasses (1–17 Mm Diameter) Were Investigated. the Radial Evolution of Concentration and Particle Distribution Was Simulated over Time and the LL Formation Was Successfully Simulated. the Predicted LL Thicknesses Compared Well with Experimental Values. the Coupled Effect of PSD, Concentration, and Mean Diameter of Particles on Wall Effect, SIPM, and Rheological Heterogeneities Across the Pipe Was Evaluated. Higher Rheological Heterogeneity Across the Pipe Was Obtained for Higher Concentration and Coarser Particle Size Distributions

Etiology of viral meningitis in Aleppo-Syria: a retrospective study

Background: Viruses are the most common causative agents of aseptic meningitis syndrome. This study aimed to identify the most common causes of viral meningitis (VM) by polymerase chain reaction (PCR) and study its relationship with age and seasonal variations.Methods: During the study period, the records of 129 patients who had been discharged and diagnosed with VM were identified and reviewed. Cerebrospinal fluid (CSF) samples collected from these patients were tested by PCR using the Seeplex V1 AC meningitis detection kit that detects herpes simplex virus type 1 and type 2 (HSV1) and (HSV2), varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus type 6 (HHV6), and the Seeplex V2 AC meningitis detection kit that detects human enteroviruses (EV).Results: VM was confirmed by PCR in 79 cases (61.42%). Most of the VM cases were reported in children younger than 6 years (72.15%; 57/79). EV were detected at the highest incidence of 60 cases (75.9%), followed by HSV1and EBV in 6 cases for each (7.6%, each), CMV in 3 cases (3.9%), VZV and HHV6 were detected in 2 cases for each (2.5%, each). VM cases were found to be more frequent during the spring season (64.6%; 51/79) and the peak incidence of enteroviral meningitis cases was during the spring season (68.4%; 41/60).Conclusions: Our study showed that EV were the most common causative agent of VM in Aleppo-Syria. Genotype and serotype of identified viruses are recommended

Randomized Controlled Trial to Compare the Safety and Efficacy of Tamsulosin, Solifenacin, and Combination of Both in Treatment of Double-J Stent-Related Lower Urinary Symptoms

Purpose. We evaluated the effectiveness and safety of tamsulosin, solifenacin, and combination of both in reducing double-J stent-related lower urinary symptoms. Materials and Methods. A total of 338 patients with double-J ureteral stenting were randomly divided, postoperatively, into 4 groups. In group I (), no treatment was given (control group), group II () received tamsulosin 0.4 mg daily, group III () received solifenacin 10 mg daily, and group IV () received a combination of both medications. Before insertion and 2 weeks after, all patients completed the International Prostate Symptom Score (IPSS), quality of life component of the IPSS (IPSS/Qol), Overactive Bladder Questionnaire (OAB-q), and Visual Analogue Pain Scale (VAPS) questionnaire. Results. The demographics and preoperative questionnaires scores of all groups were comparable. There were statistically significant differences in all scores in favour of groups II, III, and IV as compared to control group ( value < 0.005). Group IV showed statistically significant differences in total IPSS, QoL score, and OAB-q score as compared to groups II and III ( value < 0.001). Conclusions. Combined therapy of tamsulosin and solifenacin significantly alleviated lower urinary symptoms associated with double-J stents as compared to either medication alone

Extension of the Reiner-Riwlin Equation to Determine Modified Bingham Parameters Measured in Coaxial Cylinders Rheometers

The Determination of the Exact Rheological Properties, in Fundamental Units, of Cementitious Materials Has Become Gradually a Necessary Step in the Domain of Concrete Science. Several Types of Rheometers and their Corresponding Transformation Equations Are Described in the Literature. in This Paper, the Reiner-Riwlin Transformation Equation, Valid for Coaxial Cylinders Rheometers, is Developed for the Modified Bingham Model, which is an Extension of the Bingham Model with a Second Order Term in the Shear Rate. the Established Transformation is Shown to Be Compatible with the Reiner-Riwlin Equation for the Bingham and Herschel-Bulkley Models. its Validation is Further Proven by Means of Numerical Simulations Applied on Experimental Data. the Yield Stress Values for the Three Rheological Models (Applied on the Same Experimental Data) Are Compared with the Yield Stress Calculated by Means of Slump Flow Values. Results Showed that the Modified Bingham Model Results in the Most Stable Yield Stress Values, Which Are Independent of the Non-Linear Behavior. © 2012 RILEM