The Microstructural and Mechanical Characterization of Organo-Clay-Modified Bitumen, Calcareous Aggregate, and Organo-Clay Blends

Bitumen has been widely used as the binder of aggregate in road pavement due to its good viscoelastic properties, as a viscous organic mixture with various chemical compositions. Bitumen is a liquid at high temperature and it becomes brittle at low temperatures, and this temperature-sensitivity can cause the rutting and cracking of the pavement and limit its application. Therefore, the properties of existing asphalt materials need to be enhanced. The pavement with polymer modified bitumen exhibits greater resistance to rutting and thermal cracking, decreased fatigue damage, as well as stripping and temperature susceptibility; however, they are expensive and their applications have disadvantages. Bituminous mixtures are composed of very irregular aggregates bound together with hydrocarbon-based asphalt, with a low volume fraction of voids dispersed within the matrix. Montmorillonite (MMT) is a layered silicate with low cost and abundance, which consists of layers of tetrahedral silicate and octahedral hydroxide sheets. Recently, the layered silicates have been widely used for the modification of polymers, as well as in many different fields. However, there are not too much studies related with the preparation of the modified asphalt with MMT, currently. In this study, organo-clay-modified bitumen, and calcareous aggregate and organo-clay blends were prepared by hot blending method with OMMT, which has been synthesized using a cationic surfactant (Cetyltrymethylammonium bromide, CTAB) and long chain hydrocarbon, and MMT. When the exchangeable cations in the interlayer region of pristine MMT were exchanged with hydrocarbon attached surfactant ions, the MMT becomes organophilic and more compatible with bitumen. The effects of the super hydrophobic OMMT onto the micro structural and mechanic properties (Marshall Stability and volumetric parameters) of the prepared blends were investigated. Stability and volumetric parameters of the blends prepared were measured using Marshall Test. Also, in order to investigate the morphological and micro structural properties of the organo-clay-modified bitumen and calcareous aggregate and organo-clay blends, their SEM and HRTEM images were taken. It was observed that the stability and volumetric parameters of the prepared mixtures improved significantly compared to the conventional hot mixes and even the stone matrix mixture. A micro structural analysis based on SEM images indicates that the organo-clay platelets dispersed in the bitumen have a dominant role in the increase of effectiveness of bitumen - aggregate interactions

A Functional Analogy on Instructor-Learner Interaction and Reversible Work-Meaningful Learning

Analogies can be powerful teaching tools because they can make new material intelligible to students by comparing it to material that is already familiar. In assisting students to understand chemistry concepts, teachers occasionally use analogies. These analogies are believed to help the students to structure the new knowledge and they are considered to be especially useful for topics of an abstract or submicroscopic nature. However, analogies have also been identified as a factor in the students' misunderstanding of chemical concepts. By a functional analogical approach constructed onto the two fundamental concepts (learning and the work in thermodynamics) in this study, the presentation of the similarities between the interactive nature of learning and the requirements enabling a mechanical change such as the reversible expansion is aimed

Debating unamendability: deadlock in Turkey's constitution-making process

Constitutional Conciliation Commission (Anayasa Uzlaşma Komisyonu—AUK) of Turkey, established after the 2011 general elections but called off after the commission could not overcome an impasse on a number of issues, was nevertheless a significant step in Turkey’s constitutional development. One of the issues that led to the deadlock in the commission was the issue of unamendable articles. A point of divide among the four parties that made up the commission was whether the new constitution would maintain the eternal clauses of the present constitution that entrench the republic form of the state, its characteristics, and its language or whether it would not include any irrevocable articles. Except the republic’s first constitution of 1921, the three constitutions of modern Turkey included unamendable constitutional provisions, which had previously led to political and constitutional controversies. The subject of unamendable articles was one of the last issues that the commission discussed before the 25 months of enterprise was dissolved. This article traces the evolution of unamendable articles in Turkish constitutions, examines the political parties’ proposals for the draft constitution aand analyzes the debates conducted within AUK. It concludes that members of the AUK held irreconcilable positions with respect to unamendability and unamendable articles, which contributed to the breakdown of the negotiations