Sürdürülebilir Kalkınma Amaçları

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• MakaleAçık Erişim2023/r/gumushane/12771
  Engineering Properties of Cemented Paste Backfill with Full-Range Water-Reducing Admixture

  Cavusoglu, Ibrahim; Fall, Mamadou

  This paper presents the effects of a full-range water-reducing (FRWR) admixture on the key engineering properties of cemented paste backfill (CPB). CPB samples with a certain slump are prepared with 4.5% cement by mass of the tailings and different dosages of an FRWR admixture (superplasticizer contents of 1%, 3%, and 5%) to evaluate their water demand during hydration, rheological properties, self-desiccation ability, and microstructural and mechanical properties. Moreover, cement paste samples with a high water-to-cement ratio (w/c = 2) which are used to model the cement matrix of the CPB are prepared for x-ray diffraction (XRD) scanning and thermal analyses (TAns). The results show that the addition of an FRWR admixture to the studied CPB can reduce its water demand by up to 23% and significantly increase its strength from 1.0 MPa to 2.38 MPa (by approximately 2.4 times) at 28 days. The pore volume of the CPB samples is also significantly reduced from 27.17 to 18.27% due to the capability of the FRWR admixture to reduce water demand. Also, the addition of an FRWR admixture to the CPB results in a substantial decrease (up to 83%) of its yield stress, thereby improving its flowability. The CPB samples with an FRWR admixture are found to have a higher negative pore water pressure, i.e., higher self-desiccation, than the CPB sample without an FRWR admixture. The microstructural analysis also shows that the FRWR admixture has an increasing effect on the hydration products in the CPB mixture.

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• MakaleYalnız künye2019/r/gumushane/14787
  Performance Comparison of Various Chicane Types: A Driving Simulator Study

  Aydin, Metin Mutlu; Gunay, Banihan; Akgol, Kadir

  Urban streets are becoming noisy, less safe and unattractive places due to high traffic volumes and vehicular speeds. Especially, high speeds causes many problems such as traffic accidents, noise, etc. To prevent these problems and negative effects of speeding, traffic calming measures have been widely used in many developed countries. In this study, the effectiveness of ten most common chicane types on speed limit compliance were examined by comparing and ranking chicanes according to their performance. For this purpose, a “Safety Index” was developed and an Ordinary Least Square Regression analysis was performed to identify safest chicane types for undivided two-lane and divided four-lane roads by using various parameters. Additionally, statistical tests were conducted to determine the most important driver characteristics of drivers before and inside the chicanes. For the analyses, all necessary data were obtained from the driving tests of 106 volunteers using a driving simulator. For the simulation scenarios, Akdeniz University’s (Antalya/Turkey) campus roads were selected as a case area. The results showed that Chicane Types 2 (CT-2) and 7 (CT-7) have the highest Safety Index values (0.69 and 0.98) and they were found to be the most proper CTs for the undivided and divided roads, respectively. From the statistical tests, it was also found that education level, gender and driving license duration were found to be the statistically significant parameters on speed choice for the most proper chicane types. Additionally, it was concluded that the most important driver characteristics are determined as age (has a negative effect) and gender (to be male has a positive effect) of drivers before and inside the chicanes. All these findings show that the investigation of different CTs has a great potential to reduce speeds and ensure safety in urban minor roads to limit vehicle speeds.

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