Glass waste is produced in considerable amounts annually. Due to the disadvantageous nature of its recycling process, its reuse gains importance. Given the high reactivity level of glass-incorporating mixtures, the reuse of waste glass as aggregate in polymer concrete was investigated. Polymer concrete mixtures, including unsaturated polyester resin, hardener and accelerator, waste glass aggregate (up to 8 mm) and glass fabrics, were prepared for the investigation of mechanical properties. The composite specimens were reinforced by means of glass fabrics in various types (woven or mat), amounts (single or double layer) and orientation (perpendicular or parallel to loading direction). The mechanical properties of polymer concretes were tested for flexural tensile strength and compressive strength. In addition, thermal conductivity and residual strength after elevated temperatures were determined. It was concluded that these composites with easy preparation techniques have superior mechanical and thermal insulation properties compared with their counterparts available for use and their mechanical properties were mainly affected by the amount, type and orientation of the glass fabric reinforcement.
In this study, the self healing capacity of mortars incorporating a natural polymer-based hydrogel (chitosan) as a healing agent is compared to control mortars without the healing agent. The hydrogels are placed into mortars after two different methods of encapsulation. The aim of encapsulating the healing agents is to provide water proofness during the fresh state of mortars. The chitosan macrospheres (diameter≈1 mm) were stabilized by lyophilizing and encapsulated by a synthetic polymer and cement based insulation material provided from the market. Pre-trials have shown that the encapsulated hydrogel macrospheres have shown a considerable expansion after the capsules were torn. The method for observing the self healing mechanism is as follows: control and test series were cast and cured for 7 days in water at standard conditions, and then, a controlled pre-load is applied at three-point bending. The pre-loading causes controlled cracking at the lower mid points of the mortar specimens. Just after the pre-loading, the microphotographs of the cracks were taken by stereomicroscope and their ultrasonic pulse velocity (UPV) values were determined. The specimens were then placed into air-tight containers and cured over water for a further 21 days. The UPV measurements were taken after curing and the microphotographs of the cured samples were taken. The difference between the UPV measurements compared to control samples before and after curing and leaking of hydrogels into the cracks are the confirmations of the healing mechanism. The findings obtained from this study reveal promising results for incorporation of the chitosan hydrogel as a self healing agent for cementitious mixtures.
Optimising high lime fly ash content by means of silica fume incorporation to control alkalisilica reaction and drying shrinkage of mortarsHarçların alkali-silis reaksiyonu ve kuruma büzülmesini kontrol etmek için silis dumanı ikamesi ile yüksek kirece sahip uçucu külün içeriğinin optimizasyonu Bu makaleye şu şekilde atıfta bulunabilirsiniz(To cite to this article): Gökçe H.S., Hosseinnezhad H., Üzüm O., Hatungimana D. and Ramyar K., "Optimising high lime fly ash content by means of silica fume incorporation to control alkali-silica reaction and drying shrinkage of mortars", Politeknik Dergisi, 23(1): 61-66, (2020).Erişim linki (To link to this article): http://dergipark.gov.tr/politeknik/archive ABSTRACT In this study, the effect of binary and ternary cementitious systems composed of portland cement, high-lime fly ash and silica fume on the compressive strength, alkali-silica reaction (ASTM C 1567) and drying shrinkage of mortar mixtures was researched. For this purpose, binary and ternary binders were prepared with partial replacement of cement with either fly ash (15wt% and 30wt%) or silica fume (5wt%) or both mineral admixtures (15wt+%5wt% and 30wt%+5wt%). An alkali reactive basalt aggregate was used in this study. It was found that partial replacement of cement with high-lime fly ash reduced the strength of mortar mixtures even up to 28-days. Besides, addition of 5% silica fume had not a significant effect on the early strength of fly ash-bearing mixtures. However, silica fume inclusion improved the 28-day strength of mixtures. In terms of alkali-silica reaction (ASR), the fly ash with lower lime content reduced the 14-day expansion more than that of fly ash with higher lime content. The opposite results were the case in 28-day ASR expansions. The ASR expansions of the fly ash-bearing mixtures were significantly reduced by the introduction of the additional 5% silica fume to these mixtures. However, silica fume incorporation remarkably increased the drying shrinkage values of the mixtures. Finally, fly ash with higher lime content was found to be more satisfactory in terms of compressive strength, alkali-silica reaction and drying shrinkage in the ternary binder system.
In this chapter, a deep analyse of a bio-inspired phenomenon starting with broad definitions of included mechanisms is provided. Since establishing an understanding starts with drawing the boundaries of a concept, foremost the definition of related terms are discussed in detail. Afterwards, the importance and history of self-healing phenomenon including the relevant concepts are presented. In order to facilitate the classification, the relevant sub-chapters present two main classes namely autogenic and autonomic healing. Nevertheless, the concepts and mechanisms under these two main topics are also discussed in detail. Finally, evaluation of self-healing mechanisms, tests conducted to determine whether self-healing took place, the indicators of measurement methods, using materials and test methods are given in full detail.
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