Investigating the micro/macro-texture performance of roller-compacted concrete pavement under simulated traffic abrasion

Since the roller-compacted concrete pavement (RCCP) is almost smooth due to roller vi-brations in the construction process, the lack of macro-texture prevents it from being used as a final surface. This study has made efforts to improve the RCCP by proposing different scenarios to cre-ate new micro-/macro-texture surfaces and investigate their durability and skid resistance under traffic abrasion conditions. To prepare the micro-texture, eight RCCP specimens were cast using various 50–50% mixing proportions, and each of them alone in the form of siliceous and calcareous fine aggregates (natural and manufactured). For the macro-texture, each specimen was textured using such methods as seeding (three cases), stamping (two cases), and brooming (two cases). Since the durable texture should withstand the abrasive traffic flow, the RCCP-surface abrasion resistance was measured by the simulation method proposed in ASTM C944, and their skid resistance was evaluated by measuring the British pendulum test according to ASTM E303 before and after abrasion. The results showed that abrasion resistance of RCCP samples to changes in mixing design and skid resistance to changes in macro-texture have significant changes. In addi-tion, different siliceous-calcareous sand combinations not only made the concrete mix more eco-nomical but also improved its performance in case of abrasion and skid resistance. The more was the manufactured sand proportion, the higher the fracture rate was and, hence, the abrasion re-sistance. Different macro-textures created on RCCP specimens generally showed acceptable skid resistance. In this regard, stamping had the highest mean texture depth (MTD) as well as BPN, and seeding had the lowest

Experimental evaluation of tensile performance of aluminate cement composite reinforced with weft knitted fabrics as a function of curing temperature

Cement composites (CC) are among the composites most widely used in the construction industry, such as a durable waterproof and fire-resistant concrete layer, slope protection, and application in retaining wall structures. The use of 3D fabric embedded in the cement media can improve the mechanical properties of the composites. The use of calcium aluminate cement (CAC) can accelerate the production process of the CC and further contribute to improving the mechanical properties of the cement media. The purpose of this study is to promote the use of these cementitious composites by deepening the knowledge of their tensile properties and investigating the factors that may affect them. Therefore, 270 specimens (three types of stitch structure, two directions of the fabric, three water temperature values, five curing ages, with three repetitions) were made, and the tensile properties, absorbed energy, and the inversion effects were evaluated. The results showed that the curing conditions of the reinforced cementitious composite in water with temperature values of 7, 23, and 50 °C affect the tensile behavior. The tensile strength of the CCs cured in water with a temperature of 23 °C had the highest tensile strength, while 7 and 50 °C produced a lower tensile strength. The inversion effect has been observed in CC at 23 °C between 7 and 28 days, while this effect has not occurred in other curing temperature values. By examining three commercial types of stitches in fabrics and the performance of the reinforced cementitious composites in the warp direction, it was found that the structure of the “Tuck Stitch” has higher tensile strength and absorbed energy compared to “Knit stitch” and “Miss Stitch”. The tensile strength and fracture energy of the CC reinforced with “Tuck Stitch” fabric in the warp direction, by curing in 23 °C water for 7 days, were found to be 2.81 MPa and 1.65 × 103 KJ/m3, respectively. These results may be helpful in selecting the design and curing parameters for the purposes of maximizing the tensile properties of textile CAC composites

Influencia del coeficiente estructural de una base reciclada con cemento sobre la deformación permanente en la subrasante – una aproximación con el método Sudrafricano

Trabajo de investigaciónEn la investigación se diseñaron pavimentos con una base reciclada con cemento, variando el módulo resiliente de la subrasante y el espesor de la sub-base granular, en cada caso. Para cada uno de los diseños se determinó la respuesta estructural (esfuerzo y deformación en la subrasante) a través de un software y con los resultados obtenidos se determinó la relación entre la deformación permanente en la subrasante y el número de ejes equivalentes correspondientes.1. INTRODUCCIÓN 2. PLANTEAMIENTO DEL PROBLEMA 3. OBJETIVOS 4. MARCO TEÓRICO 5. ESTADO DEL ARTE 6. PREGUNTA DE INVESTIGACIÓN 7. ALCANCES Y LIMITACIONES 8. METODOLOGÍA 9. CÁLCULOS Y RESULTADOS 10. ANÁLISIS DE RESULTADOS 11. CONCLUSIONES Y RECOMENDACIONES 12. BIBLIOGRAFÍAPregradoIngeniero Civi

Strategic human resource management practices, perceived organisational support and employee trust towards organisational commitment

The purpose of this research was to identify key SHRM practices that are used in oil and gas industry and the effect of these practices on employee trust perceived organisational support and organisational commitment. More specifically this research is intended to determine what influence do SHRM practices have on employee trust, perceived organisational support and organisational commitment. Oil companies in Libya have faced a structural problem, after the revolution that started in 2011. This structural problem led to a massive economic fall due to lack of HR strategies performed during the war by the oil companies. Changes in the oil and gas industry have increased the importance of employees towards the performance of the business. Oil and gas companies need to apply strategic human resource management (SHRM) practices to retain employee trust and commitment towards the organisation. Employee trust and perceived organisational support are the two measures of employee attitude that determines organisational commitment. The research was conducted using the quantitative method, and self-administered survey questionnaire was used to gather information from low and middle-level human resource managers. Three hundred and thirty-one managers with a response rate of 66.2% completed the survey that measured their use of SHRM practices and demographics. Structural equation modelling was used to examine the exploratory and confirmatory factor analysis of the instruments. The quantitative results revealed that SHRM practices are more significant to increase trust and commitment. The causal paths between the constructs of SHRM practices, employee trust and organisational commitment found significant indirect effect statistically. Employee trust and perceived organisational support were found to be partially mediating between SHRM practices and organisational commitment. This results concluded that firms with the less dynamic environment might possess a lack of SHRM practices. Development and motivation of the employees including their training and communication skills are required for the high competitive environment. The SHRM model validated in this research suggests that out of the seven variables (internal career ladders, training, appraisals, employment security, employee participation, job description, and pay for performance) only training and appraisals contribute directly to explain organisational commitment. This research thus confirms that training and appraisals lie in the strategic models and enables the SHRM policies to be in force. Social exchange theory (SET) explained the relationships between employees and managers very well in this study. SET from this research confirmed that the exchange of resources between the individuals is very important

Study on the effects of Polypropylene fibers on the splitting strength, strain capacity and energy absorption of rolled compacted semi-lightweight concrete with applicability in concrete blocks

This study aims at improving the tensile behavior of concrete blocks by adding polypropylene fibers to the concrete mixture. For this purpose, 84 cylindrical and cubic specimens were constructed and tested under tensile splitting and compressive force. Three variables of fiber dosage, cement content, and fiber type were taken into account to study the sensitivity of splitting strength, strain capacity, compressive strength, and energy absorption to these variables. The results show that the specimens without fibers experienced a sudden non-ductile failure, whereas this is not the case for the specimens with added fibers. All the considered response parameters were improved thanks to the addition of fibers. Generally, the improvement of specimens with micro fibers was better than that of the corresponding specimens with macro fibers, especially when larger cement content was included

A novel life prediction model based on monitoring electrical properties of self-sensing cement-based materials

Assessing the damage level in concrete infrastructures over time is a critical issue to plan their timely maintenance with proper actions. Self-sensing concretes offer new opportunities for damage assessment by monitoring their electrical properties and relating their variations to damage levels. In this research, fatigue tests were conducted to study the response of a self-sensing concrete under high-cycle dynamic loading. The concept of G-value was defined as the slope of the voltage response baseline of the self-sensing concrete over time that reflects the damage created under the fatigue-loading test. Based on this definition, log (G)–log (N) curves were obtained using a linear regression approach, with N representing the number of cycles during the fatigue tests. While traditional fatigue curves S-log (N) are used to estimate the remaining life under fatigue loading, log (G)–log (N) diagrams can be used to determine the damage level based on the voltage response of the self-sensing concrete as a function of the loading history. This finding can be useful for the estimation of the lifetime and remaining life of self-sensing concrete structures and infra-structure, eventually helping to optimize the related maintenance operations

T Ü RK Bİ Y O K İM YA DE R N E Ğ İ D ERGİS İ 1976 ORJİNAL 1. ÖRNEK 2. ÖRNEK

ABSTRACT Objective: An important predictor for infant survival is birth weight. Normal fetal growth is related to various intrauterine factors. Low birth weight is thought to have relation with oxidative stress which plays an important role in reducing the birth weight. Among the paraoxonase family PON1 protects LDL and HDL from the lipid peroxidation. This is HDL associated enzyme having antioxidant property. We aimed to evaluate the arylesterase and lactonase activity of PON1 in cord blood in relation to birth weight. We hypothesized that cord blood PON1 arylesterase and lactonase activities will be compromised in neonates having low birth weight. Methods: We included 80 neonates born in our hospital irrespective of mode of delivery as 40 cases and 40 controls. PON1 arylesterase and lactonase activity were measured using spectrophotometer. Results: Serum arylesterase activity decreased significantly in low birth weight babies (p<0.05). Linear regression analysis (R=0.595) indicates significant correlation between arylesterase and birth weight. Serum lactonase activity of PON1 also gets reduced in low birth weight babies. Its linear regression analysis showed (R=0.716) suggesting significant correlation between lactonase and birth weight. Conclusion: Reduced PON1 activity can be explained on the basis of ER stress and atherogenic changes in the placental circulation. Ours is the first study in cord blood paraoxonase activities in relation to birth weight. As the sample in our study is cord blood, it is essentially a noninvasive one. Further studies are needed in this direction to assess the effect of the oxidative stress on fetus through cord blood in its long term prospective. Key Words: Paraoxonase1, arylesterase, lactonase, cord blood, low birth weight Conflict of Interest: There is no conflict of interest with any financial organization regarding the material discussed in the manuscript. ÖZE

T Ü RK Bİ Y O K İM YA DE R N E Ğ İ D ERGİS İ 1976 ORJİNAL 1. ÖRNEK 2. ÖRNEK

ABSTRACT Objective: Arterial hypertension is often associated with pathologies related with oxidative stress. Angiotensin converting enzyme (ACE) inhibitors have been used as a safe and effective treatment of hypertension and coronary heart disease. However, the significance of ACE inhibitor usage in hypertension-induced cerebrovascular and neurodegenerative diseases is still unknown. In this study, we aimed to investigate the effects of lisinopril, an ACE inhibitor, on oxidative stress and antioxidant enzyme activities in brain tissues of rats with L-NAME (N ω -Nitro-L-Arginine Methyl Ester hydrochloride) induced hypertension. Methods: Thirty-two Sprague-Dawley rats were divided into four groups: Control, L-NAME, L-NAME plus lisinopril, and only lisinopril. Hypertension was induced by oral administration of the L-NAME (75 mg/kg/day) in drinking water for 6 weeks. Rats were treated with Lisinopril (10 mg/kg/day) for six weeks. Systolic blood pressures were measured at the first, third and sixth weeks by using tail cuff method. Malondialdehyde (MDA), Superoxide dismutase (SOD), Catalase (CAT) and Glutathione peroxidase (GSH-Px) activity were measured from the brain tissue. Nitric oxide (NO) levels were measured from plasma. Results: Our results showed that L-NAME leads to an increase in systolic blood pressure of animals. The antihypertensive effect of lisinopril was observed. MDA level was significantly increased, and antioxidant enzymes activities were decreased in L-NAME given group (p<0.05). However, there was no statistically significant differences between the lisinopril given and other groups according to antioxidant enzymes activities (p>0.05). Conclusion: In our study, hypertension led to oxidative damage in brain tissues. Although lisinopril prevents the hypertension induced oxidative damage, direct antioxidant effect was not observed. Further studies are needed in order to gain certainty effect of lisinopril in brain tissue