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Öğe An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete(PERGAMON-ELSEVIER SCIENCE LTD, 2010) Akcaozoglu, Semiha; Atis, Cengiz Duran; Akcaozoglu, KubilayIn this work, the utilization of shredded waste Poly-ethylene Terephthalate (PET) bottle granules as a lightweight aggregate in mortar was investigated. Investigation was carried out on two groups of mortar samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionally, blast-furnace slag was also used as the replacement of cement on mass basis at the replacement ratio of 50% to reduce the amount of cement used and provide savings. The water-binder (w/b) ratio and PET-binder (PET/b) ratio used in the mixtures were 0.45 and 0.50, respectively. The size of shredded PET granules used in the preparation of mortar mixtures were between 0 and 4 mm. The results of the laboratory study and testing carried out showed that mortar containing only PET aggregate, mortar containing PET and sand aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category in terms of unit weight and strength properties. Therefore, it was concluded that there is a potential for the use of shredded waste PET granules as aggregate in the production of structural lightweight concrete. The use of shredded waste PET granules due to its low unit weight reduces the unit weight of concrete which results in a reduction in the death weight of a structural concrete member of a building. Reduction in the death weight of a building will help to reduce the seismic risk of the building since the earthquake forces linearly dependant on the dead-weight. Furthermore, it was also concluded that the use of industrial wastes such as PET granules and blast-furnace slag in concrete provides some advantages, i.e., reduction in the use of natural resources, disposal of wastes, prevention of environmental pollution, and energy saving. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Artificial Intelligence Approach in Predicting the Effect of Elevated Temperature on the Mechanical Properties of PET Aggregate Mortars: An Experimental Study(Springer Heidelberg, 2021) Colak, Andac Batur; Akcaozoglu, Kubilay; Akcaozoglu, Semiha; Beller, GulhanIn this study, the effect of high temperature on the flexural and compressive strength of mortars containing waste PET aggregates was investigated experimentally. The mortar samples prepared in 5 different concentrations with a total of 2.5%, 5%, 10%, 20% and 30% PET aggregate substitution were heated up to 100, 150, 200, 250, 300 and 400 degrees C. After waiting for 1, 2 and 3 h at these temperatures, flexural and compressive strength tests were performed. It was observed that flexural strength and compressive strength values decreased with increasing temperature and PET aggregate amounts in all mixtures. An artificial neural network was designed to estimate flexural and compressive strength values using experimental data. It has been observed that the developed artificial neural network can predict flexural and compressive strengths with an average error of - 0.51%.Öğe Deterioration and conservation problems of historical fountains in Cappadocia-Nigde(Parlar Scientific Publications, 2020) Akcaozoglu, Semiha; Yavascan, Emel Efe; Gokce, Mehmedi VehbiHistorical artefacts, monuments and buildings are an integral part of the socio-cultural, architectural and aesthetic features of the past civilizations. Cultural heritage, which is accepted as the common property of humanity, reflects the feelings and thoughts of civilizations that have lived from past to present. Fountains that are an integral part of the historical and cultural environment of a city are one of the most outstanding structures, as they are built to reflect the architectural and socio-cultural characteristics of the city. They are considered to be a bridge between the past and the future, and thus it is extremely important to ensure their sustainability as well as their preservation. The aim of this study was to document the historical fountains found in the city center of Nigde within the Cappadocia Region, create a report on these structures and draw attention to the issues regarding their preservation. For this purpose, a total of 13 fountains which are located in the center of Nigde were examined. The material and construction techniques and typologies of these fountains were determined and finally their physical conditions and reasons for their deterioration were investigated. In general, among the reasons for the deterioration of the fountains were found to be long-term natural and human effects. Preserving these fountains which are in danger of destruction and loss of function is a must in order to transfer such historical and cultural assets to the future. From this point of view, it is considered that this study will contribute greatly to future preservation and restoration works on these historical fountains which once served for a substantial social need of urban life. © 2020 Parlar Scientific Publications. All rights reserved.Öğe DETERIORATION AND CONSERVATION PROBLEMS OF HISTORICAL FOUNTAINS IN CAPPADOCIA-NIGDE(Parlar Scientific Publications (P S P), 2020) Akcaozoglu, Semiha; Yavascan, Emel Efe; Gokce, Mehmedi VehbiHistorical artefacts, monuments and buildings are an integral part of the socio-cultural, architectural and aesthetic features of the past civilizations. Cultural heritage, which is accepted as the common property of humanity, reflects the feelings and thoughts of civilizations that have lived from past to present. Fountains that are an integral part of the historical and cultural environment of a city are one of the most outstanding structures, as they are built to reflect the architectural and socio-cultural characteristics of the city. They are considered to be a bridge between the past and the future, and thus it is extremely important to ensure their sustainability as well as their preservation. The aim of this study was to document the historical fountains found in the city center of Nigde within the Cappadocia Region, create a report on these structures and draw attention to the issues regarding their preservation. For this purpose, a total of 13 fountains which are located in the center of Nigde were examined. The material and construction techniques and typologies of these fountains were determined and finally their physical conditions and reasons for their deterioration were investigated. In general, among the reasons for the deterioration of the fountains were found to be longterm natural and human effects. Preserving these fountains which are in danger of destruction and loss of function is a must in order to transfer such historical and cultural assets to the future. From this point of view, it is considered that this study will contribute greatly to future preservation and restoration works on these historical fountains which once served for a substantial social need of urban life.Öğe Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates(ELSEVIER SCI LTD, 2011) Akcaozoglu, Semiha; Atis, Cengiz DuranIn this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)-binder ratio (WPLA/b) was 0.60; the water-binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural-tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural-tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Examination of mechanical properties and microstructure of alkali activated slag and slag-metakaolin blends exposed to high temperatures(Ernst & Sohn, 2022) Akcaozoglu, Semiha; Ciflikli, Murat; Bozkaya, Omer; Atis, Cengiz Duran; Ulu, CuneytThis paper reports an experimental study of the influence of elevated temperature on alkali activated slag (AAS) and slag-metakaolin (MK) systems. The residual compressive and flexural tensile strengths, ultrasonic pulse velocity (UPV) and porosity and water absorption ratios of AAS and AAS-MK composites after subjected to elevated temperatures of 200, 400, 600, 800, and 1000 degrees C were investigated. Two different procedures were applied for cooling the specimens. The changes in the microstructure of the composites after subjected to high temperature were examined with scanning electron microscope and X-ray diffraction. Test results reveal that depending on the increasing temperature, the residual compressive strength, flexural tensile strength, and UPV values of the specimens decreased, and porosity and water absorption ratios increased. The minimum strength results of AAS and AAS-MK specimens were observed at 800 and 600 degrees C, respectively. In particular, there have been significant changes in the internal structure of AAS and AAS-MK specimens exposed to 1000 degrees C and new reaction products were observed. Test results have shown that AAS specimens are a new alternative that can be developed for use in environments exposed to high temperatures. Since this new composite contains only slag binder and slag aggregate, it can be an economical product that use fully recycled material and these properties can increase the application areas of environmentally friendly material.Öğe Investigation of the bacterial modified waste PET aggregate VIA Bacillus safensis to enhance the strength properties of mortars(Elsevier Sci Ltd, 2021) Akcaozoglu, Semiha; Adiguzel, Ali Osman; Akcaozoglu, Kubilay; Deveci, Ece Ummu; Gonen, CagdasPolyethylene terephthalates (PET), which are highly resistant to degradation under natural environmental conditions due to their inert, hydrophobic and high molecular weights, are collected in landfills or dispersed as waste. Considering the increasing use of PET, the interest in multidisciplinary studies aimed to obtaining high value added products from PET wastes has increased. In this study, the potential of using waste plastics made of Polyethylene terephthalate (PET) treated with bacteria as an aggregate in the production of mortar was investigated. First, the bacterial strains, which secreted esterase or cutinase, were screened for their ability to attach to hydrophobic surfaces and biofilm formation. TH401, which showed potential for the modification of the PET aggregates, was identified as Bacillus safensis. To enhance the compatibility of the PET, the waste PET aggregates were treated with submerged fermentation via B. safensis TH401. The FTIR analyses conducted after the treatment showed that the chemical structure of the PET had been modified. Mortar samples were prepared by using the modified PET aggregates. The compressive and flexural tensile strength values of the samples were measured on days 7, 28 and 56. The compressive strength values of the bacteria modified samples were 4.87%, 7.51% and 13.13% higher than the non-bacterial samples at 22 degrees C, 30 degrees C and 50 degrees C, respectively. The increase in curing temperatures had a positive effect on compressive and flexural tensile strength values. The highest strength values were obtained in the samples cured at 50 degrees C. In the EDX spot of the mixtures, major peaks of C, O, Ca were detected indicating the presence of CaCO3 and bacteria. Stratification on the PET surface as a result of bacterial modification was clearly observed in the SEM images. The test results showed that bacterial modification contributed to the increase in the strength of the waste PET aggregate concrete. It can be said that mortars produced with bacteria modified PET aggregates can be used as an economical and environmentally friendly material alternative in the construction industry. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Microstructural examination of the effect of elevated temperature on the concrete containing clinoptilolite(ELSEVIER SCI LTD, 2014) Akcaozoglu, Kubilay; Fener, Mustafa; Akcaozoglu, Semiha; Ocal, RecepIn this study, the effect of elevated temperature on the properties of concrete containing clinoptilolite was investigated by microscopic analyses. For this purpose, seven different mixtures were prepared (the control mixture and six mixtures including 5%, 10%, 15%, 20%, 30% and 40% clinoptilolite by weight). The water binder (w/b) ratio used in the mixtures was 0.475. The dry unit weights, water absorption ratios, porosity ratios, compressive strengths and thermal conductivity coefficients of the mixtures were measured. In addition the specimens exposed to elevated temperatures of 250, 500,750 and 1000 degrees C. Two different cooling methods were used (slow cooling and fast cooling). The residual compressive strengths of the specimens which were exposed to elevated temperatures were measured. In addition the mineral and texture changes of the specimens were examined by using plane polarized microscope. Test results indicated that, clinoptilolite substitution decreased the compressive strength of the specimens in early days, but increased at later days. The positive effects were observed about clinoptilolite substitution on the residual compressive strength of the specimens. It was observed from microscopic analyses that, as the amount of clinoptilolite increased in the mixtures, aggregates were less affected from elevated temperatures. Fast cooling (FC) method resulted in strength losses when compared to slow cooling (SC) method. Additionally, clinoptilolite substitution decreased the thermal conductivity coefficient of the concrete. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Recycling of waste PET granules as aggregate in alkali-activated blast furnace slag/metakaolin blends(ELSEVIER SCI LTD, 2014) Akcaozoglu, Semiha; Ulu, CuneytIn this study the utilization of waste PET aggregate in alkali-activated slag and slag/metakaolin blended mortar was investigated. Sodium hydroxide (NaOH) pellets and liquid sodium silicate were used as activators. Eighteen different mortar mixtures were prepared for the laboratory tests. In the reference mixture, unground slag (max Size of 4 mm) was used as aggregate. In PET aggregate mixtures, slag aggregate was replaced with waste PET aggregate, in amount of 20%, 40%, 60%, 80% and 100% by volume. The water-binder (w/b) ratio and aggregate-binder ratio used in the mixtures were 0.50 and 2.75, respectively. The unit weight, compressive strength, flexural tensile strength, ultrasonic wave velocity and water absorption and porosity ratios of the mixtures were measured. The test results showed that, using PET aggregate contributed to decrease of unit weight of alkali-activated mortars due to the low density of PET aggregate. Although the strength values of the specimens decreased depending on increasing waste PET aggregate amount, the compressive strength values of the alkali-activated slag mortars containing waste PET aggregate were satisfactory. In addition, alkali-activated slag mixtures containing 60% and 80% waste PET aggregate were drop into structural lightweight concrete category in terms of unit weight and strength properties. However, the compressive strengths of alkali-activated slag/metakaolin blended mixtures were lower than alkali-activated slag mixtures at the same cure condition. It is concluded from the test results that there is a potential for the use of waste PET as aggregate in the production of alkali-activated slag mortar. Because of using waste materials as binder and aggregate for mortar production in this study, alkali-activated slag mortar with PET aggregate is thought to be a good alternative for recycling of waste materials. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Thermal conductivity, compressive strength and ultrasonic wave velocity of cementitious composite containing waste PET lightweight aggregate (WPLA)(ELSEVIER SCI LTD, 2013) Akcaozoglu, Semiha; Akcaozoglu, Kubilay; Atis, Cengiz DuranIn this study, the influence of waste PET as lightweight aggregate (WPLA) replacement with conventional aggregate, on thermal conductivity, unit weight and compressive strength properties of concrete composite was investigated. For this purpose, five different mixtures were prepared (the control mixtures and four WPLA mixtures including 30%, 40%, 50%, and 60% waste PET aggregate by volume). Thermal conductivity (TC) coefficients of the specimens were measured with guarded hot plate apparatus according to TS ISO 8302 [1]. The thermal conductivity coefficient, unit weight and compressive strength of specimens decreased as the amount of WPLA increased in concrete. The minimum thermal conductivity value was 0.3924 W/m K, observed at 60% WPLA replacement. From this result, it was concluded that waste PET aggregates replacement with conventional aggregate in the mixture showed better insulation properties (i.e. lower thermal coefficient). Due to the low unit weight and thermal conductivity values of WPLA composites, there is a potential of using WPLA composites in construction applications. (c) 2012 Elsevier Ltd. All rights reserved.
