Theses supervised by Prof. Dr. Mustafa Şahmaran
11 theses · Hacettepe University, Gazi University
Development of geopolymer concretes with construction demolition waste
All around the world, sustainability of degrading infrastructures is a growing concern. Conventional concrete which is the main building block of these infrastructures consists of Portland cement as the main binding phase. Globally, there is an increasing trend in the cement consumption and as the emerging countries continue developing, the trend is expected to continue increasing. However, production of Portland cement is significantly energy-inefficient, carbon-intensive and accounts for 5 to 8% of total human-driven CO2 emissions. Prolonged sustainability therefore necessitates the design and production of construction materials that are eco-friendly in nature. For true infrastructural sustainability, hence, a paradigm shift is necessary in terms of both greenness of conventional concrete material and improved infrastructural durability for the sake of less frequent repairs. Construction and demolition applications have become one of the leading sectors in the world with the increased number of repetitive repair/renovation/maintenance of buildings, roads, bridges and other structures. However, each year, significant amounts of solid waste are generated as a result of the abovementioned applications requiring to be tackled properly. There are multiple adverse effects of construction and demolition waste (CDW) which include (i) waste landfilling of very large clean lands, (ii) causing hazardous pollution which jeopardize the surroundings and (iii) wasting of natural resources. Although "zero CDW" seems unpractical since the waste generation is unavoidable, effective solutions to minimize the amount of CDW generated must be sought for the sake of environmental, social and economic benefits. To counteract the negative effects of Portland cement production and favour increased materials' greenness, "geopolymers" are being researched widely nowadays. Geopolymer is a cement-free binding material obtained by the alkali-activation of certain aluminosilicate source materials. The source materials are generally obtained from industrial by-products including fly ash, slag, etc. Moreover, along with the significantly superior materials' greenness, geopolymers are being repeatedly reported to have high strength and enhanced durability performance (especially in terms of acid, corrosion, fire and frost resistance), although large-scale production and applications of geopolymer concretes are very restricted since the performance properties of ultimate geopolymeric materials are largely dependent on the selected aluminosilicate source material, availability of which is highly dependent on the geography. The current research aims at developing "green" geopolymeric concrete whose constituents are entirely obtained from CDW for truly sustainable infrastructural development. For the purposes of the research, firstly, geopolymeric binding phases were developed using the inert portion of CDW which is largely composed of waste concrete, wall/roof members including different types of bricks/tiles and waste glass. Secondly, CDW-based aggregates with different sizes were incorporated into the geopolymeric binders to obtain "green" mortar and concrete mixtures. After evaluating the mechanical and micro-mechanical properties of geopolymer concretes, the focus was placed on the assessment of a set of durability properties. Successful outcomes and wide knowledge transfer of the current research are believed to make benefits in the lives of individuals by not only lowering the cost-inefficient and environment-unfriendly repairs of infrastructures but also completely recycling the CDW which is troubling all countries around the world with easy-to-implement, low-cost and energy-efficient techniques.
Influence of mixing methods on the nox reduction capability and electrical properties of photocatalytic cementitious systems
Nitrogen Oxides (NOx) are a group of highly reactive and hazardous gases encompassing compounds ranging from nitrous to nitric acid. Air pollution caused by nitrogen oxides that are emitted to the atmosphere by industrial corporations and vehicles has reached worrisome levels, especially in crowded cities. To eliminate the adverse effects of these gases, titanium dioxide (TiO2) is used worldwide as a photocatalyst due to its high efficiency in oxidization of NOx. Incorporating TiO2 into cement-based composites gives them photocatalytic capability: uniform and stable dispersion of TiO2 throughout the matrix is an indisputable requirement for improved photocatalytic efficiency. The main purpose of this study is to investigate the effects of different mixing techniques and surfactant materials on the dispersion of high dosage nano-TiO2 particles (5% of total weight of binder materials) throughout cement-based materials, with the goal of producing cost-effective cementitious systems, more feasible mixing methods, and ensuring proper dispersion of nano-TiO2. Five different mixing methods were proposed to achieve uniform distribution of the nano-TiO2. They were each implemented using different mixing procedures, equipment and surfactants. The performance of each mixing method was evaluated based on photocatalytic performance, electrical impedance (EI), compressive strength and microstructural analysis. Test results showed evidence of the significantly positive effect of polyacrylic acid (PAA) on the dispersion of nano-TiO2. In general, the highest dispersion occurred with ultrasonication and binary utilization of polycarboxylate ether-based plasticizer (PCE) and PAA. The EI test was a highly effective evaluation method for homogeneous distribution of conductive nano particles throughout the matrix. Results also showed a significant relationship between electrical performance and nitric oxide (NO) degradation of composites, and electrical properties of composites are able to provide a reliable estimate of the photocatalytic efficiency of them.
Hasarlarını kendiliğinden algılama ve iyileştirme kabiliyetine sahip çok fonksiyonlu çimento bağlayıcılı kompozitler
Tasarlanmış çimento bağlayıcılı kompozitlere (ECC) nano (karbon nano tüp [KNT]) ve mikro (karbon fiber lif [KF]) ölçekte karbon esaslı malzeme ilavesi ile kendiliğinden iyileşme ve kendini algılama özelliklerinin birlikte değerlendirildiği çok fonksiyonlu akıllı çimento esaslı kompozitlerin geliştirilmesi tez çalışmasının temel amacıdır. Geliştirilen kompozitlerin kendiliğinden iyileşme ve kendini algılama özelliklerinin gerçekçi ortam koşullarında ve uzun dönemlerde sürdürülebilirliğinin incelenmesi adına sürekli su ve ıslanma kuruma kürünün kısa ve uzun dönemdeki etkileri tez çalışması kapsamında incelenmiştir. Ayrıca karbon esaslı malzeme kullanılarak oluşturulan kompozitlerde yüksek ve düşük kızdırma kaybına sahip uçucu küllerin farklı oranlarda (uçucu kül / portland çimentosu: 1,2; 2,2) ikamesinin karışımların kendiliğinden iyileşme ve kendini algılama özelliklerine etkisi değerlendirilmiştir. Karbon esaslı malzeme içeren karışımlarla karşılaştırma yapmak amacıyla karbon esaslı malzeme içermeyen kontrol karışımları da hazırlanmıştır. Kendiliğinden iyileşme testleri hasarsız (sağlam) ve çatlaklı (ön yüklenmiş) numuneler üzerinde hızlı klor iyonu geçirimlilik testi, elektriksel direnç testleri ile gerçekleştirilmiştir. Karbon esaslı kompozitlerin mekanik özellikleri, basınç ve eğilme testleri ile değerlendirilmiş, ön yükleme yapılarak çatlatılmış ve belirtilen kür koşullarında iyileştirilmiş numunelerle mukayese edilmiştir. Numunelere ait çatlaklar video mikroskop aracılığıyla takip edilerek her bir karışıma ait çatlak kapanma performansları analiz edilmiştir. Bunun yanında kendiliğinden iyileşme/algılama yeteneğine sahip numunelerin mikro yapılarını irdelemek adına SEM/EDX, TGA ve XRD testleri yapılarak her bir karışım ayrı ayrı karakterize edilmiştir. Çalışma sonuçlarına göre genel olarak, karbon esaslı malzeme içeren numunelerin basınç ve eğilme dayanımlarında yer yer kontrol numunelerine kıyasla düşüşler yaşanmış, ancak elektriksel direnç testlerinde hasar karşısında kendini algılama performansı (özellikle KNT) üst seviyede bulunmuştur. Bunun yanında genel olarak ön yüklenmiş numunelerde, karışım ve kür koşullarından bağımsız olarak çatlaklarda iyileşmenin belirgin olduğu görülmüştür.
Development of construction demolition waste-based geopolymeric composites suitable for three-dimensional additive manufacturing
Conventional concrete, the main building block of our infrastructure, uses Portland cement (PC) as the main binder, consumption of which is increasing rapidly on a global scale. PC production is significantly energy-inefficient and accounts for up to 9% of total human-driven CO2 emissions worldwide. On the other hand, the construction and demolition waste (CDW) industry is recognized as one of the main sectors contributing to the global solid waste production, constituting 30-40% of total urban waste. Therefore, development of greener binders and proper handling of CDW is of great importance to benefit environment-, social- and economy-wise. In addition, along with the material-related breakthroughs, operation-related breakthroughs utilizing advanced manufacturing technologies need to be made to achieve truly sustainable construction practices. The traditional formwork system in the construction industry requires high cost, workmanship, energy and causes significant waste generation and operational challenges. Thus, three-dimensional additive manufacturing (3D-AM) method can be applied to concrete-like materials as a promising alternative to the existing methods for construction and can contribute to a paradigm shift. This thesis study aims (i) to develop innovative alternative green construction materials by using out of waste materials obtained from construction and demolition activities, and (ii) to merge these developed green materials into 3D-AM for the achievement of truly sustainable construction practices both at the material and operational levels. In that context, to begin with, geopolymer paste mixtures were produced by using CDW-based components with a primary focus on fresh/rheological properties. After that, CDW-based geopolymers were incorporated with CDW-based fine recycled concrete aggregates (FRCA) to obtain geopolymer mortars with fresh properties fitted for 3-dimensional printability. In conclusion, the performance of selected geopolymer mortar mixture with the properties fitted for 3 dimensional-printability was validated via laboratory-scale 3D-AM application. It is believed that adoption and implementation of all novel cost-effective solutions proposed by the current thesis study will provide a great opportunity for valorising waste materials for use in high-grade building products, reducing CO2 emissions by closing the human-driven carbon cycle, increasing energy efficiency and ensuring proper resource management; which will help boost green construction in favour of human health, natural ecosystems, global economy and future circularity of valuable raw materials and products, and tackling the global issue of climate change.
New generation geopolymer binders incorporating construction demolition wastes
As a result of consistently expanding urban population, continuous development and industrialization of countries' economies around the world, construction and demolition industry gained prominence, despite the fact that it is also considered to be one of the largest producers of solid wastes on a global scale. At the root of substantially increased amounts of construction and demolition waste (CDW) around the world, there, for the most part, stand the new structural applications, repair/maintenance, renovation, demolition works and infrastructural development projects. If not controlled appropriately, these wastes, most of which are going to clean landfills and which are likely to incorporate toxic substances, can endanger the health of individuals and environments surrounding them. Therefore, it is crucial to deal with CDW in proper ways for environmental, social and economic benefits. From the material greenness point of view, geopolymers have been drawing the attention of numerous researchers as promising alternatives to Ordinary Portland Cement (OPC). Geopolymer is a class of aluminosilicate-based binding materials and relies on no cement. It can be made from industrial by-products such as fly ash and slag activated by an alkaline solution. Geopolymers are appealing due to engineering performances such as higher strength and resistance to acid, corrosion, fire/temperature and frost, in addition to material greenness. The aim of this thesis is to evaluate the usability of construction demolition wastes in geopolymer production. Roof tile, red clay brick, hollow brick, concrete and glass wastes which are forming a large part of construction demolition wastes were classified, crushed and grounded right after demolition. These waste materials were used as aluminosilicate precursors individually for alkali activation without inclusion of any type of mainstream pozzolanic materials. Sodium hydroxide, sodium silicate, potassium hydroxide were used individually or combined at different ratios as alkaline activator for polymerization reactions at different molarity and concentrations. Geopolymer pastes which are based on construction demolition wastes were tested under uniaxial compressive strength loading to determine implementability of using CDW as an aluminosilicate source for geopolymers. Besides, geopolymer pastes were characterized with respect to their morphology, chemical and crystallographic structure using methods of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Thermogravimetric Analysis (TGA). Consequently, usability of the construction demolition wastes as aluminosilicate sources in the geopolymer production individually or combined at specific ratios has been proven. Results show that it is possible to obtain the desirable strength grades from geopolymer pastes by alkali activation of brick-based construction demolition waste. However, it seems necessary to place more focus on the improved usability of waste concrete and glass in the production of geopolymer pastes.
Investigation of the rheological and workability properties of construction and demolition waste based geopolymer mortars
Being the most widely used construction material, concrete brings about considerable challenges. Portland cement (PC), main binding material for concrete, creates enormous negative impacts mainly due to the high energy requirement for its production and associated release of greenhouse gases. Production of PC and concrete encompasses a series of steps which require involvement of natural resources such as water, aggregates, clay, limestone and gypsum, which leads to detrimental effects for environment as well. Considering that, minimizing the usage of cementitious materials would clearly increase the environmental benefits such as reduced energy consumption, CO2 emissions and raw material use. This therefore has led researchers to search for the development of environmentally-friendly construction materials. Efforts within the recent years resulted in novel concepts of new generation binder materials termed as alkali-activated materials or geopolymers, that are successful candidates to partially or fully substitute PC. Geopolymers are inorganic polymers that are formed as a result of the reaction between aluminosilicate source materials (i.e. precursors) and alkaline activators (e.g. solutions of alkali-hydroxide/-silicate). Among different aluminosilicate precursors used in geopolymer technology, mineral admixtures such as blast furnace slag, fly ash, silica fume and metakaolin are prevalent while as different alkaline activators, sodium hydroxide potassium hydroxide, calcium hydroxide, sodium silicate are used more commonly. However, these precursors are highly demanded given their successful utilization concrete mixtures as mineral admixtures for years. Therefore, increasing attention was started to be paid on aluminosilicate precursors that are not strongly demanded by concrete industry. As a result of the urban transformation, which is mainly based on demolishment and reconstruction, millions of buildings are transformed each year upon completing their service life and/or reaching to a state that is dangerous to their dwellers and environment. What to do with the tremendous amounts of Construction and Demolition Waste (CDW) created is a question of huge debate globally and CDW mostly ends up being landfilled, which requires immense areas of storage and is very costly health-/economy-/environment-wise. One effective way for the proper CDW handling is to utilize CDW components in producing geopolymers. This is reasonable given the fact that CDW generation is a global problem and CDW can be easily found anywhere in the world. In this study, it was aimed to analyze effects of activators type, usage rates and combinations on rheological and workability performance of CDW based geopolymer matrix. In that context, at first, mortar phase composed of wall and roof members including bricks, tiles, glass waste and concrete waste in which recycled aggregate was utilized, was investigated with empirical test methods. For detailed investigation, rheometer was used to understand rheological and workability characteristic of CDW based geopolymer in addition to empirical test methods. In that way, know-how about rheological and workability performance of CDW based geopolymer was formed as well as mechanical performance and it was made possible to select the correct activator according to the application needs by using the results of the thesis study.
Investigation of the rheological and workability properties of construction and demolition waste based geopolymer mortars
Being the most widely used construction material, concrete brings about considerable challenges. Portland cement (PC), main binding material for concrete, creates enormous negative impacts mainly due to the high energy requirement for its production and associated release of greenhouse gases. Production of PC and concrete encompasses a series of steps which require involvement of natural resources such as water, aggregates, clay, limestone and gypsum, which leads to detrimental effects for environment as well. Considering that, minimizing the usage of cementitious materials would clearly increase the environmental benefits such as reduced energy consumption, CO2 emissions and raw material use. This therefore has led researchers to search for the development of environmentally-friendly construction materials. Efforts within the recent years resulted in novel concepts of new generation binder materials termed as alkali-activated materials or geopolymers, that are successful candidates to partially or fully substitute PC. Geopolymers are inorganic polymers that are formed as a result of the reaction between aluminosilicate source materials (i.e. precursors) and alkaline activators (e.g. solutions of alkali-hydroxide/-silicate). Among different aluminosilicate precursors used in geopolymer technology, mineral admixtures such as blast furnace slag, fly ash, silica fume and metakaolin are prevalent while as different alkaline activators, sodium hydroxide potassium hydroxide, calcium hydroxide, sodium silicate are used more commonly. However, these precursors are highly demanded given their successful utilization concrete mixtures as mineral admixtures for years. Therefore, increasing attention was started to be paid on aluminosilicate precursors that are not strongly demanded by concrete industry. As a result of the urban transformation, which is mainly based on demolishment and reconstruction, millions of buildings are transformed each year upon completing their service life and/or reaching to a state that is dangerous to their dwellers and environment. What to do with the tremendous amounts of Construction and Demolition Waste (CDW) created is a question of huge debate globally and CDW mostly ends up being landfilled, which requires immense areas of storage and is very costly health-/economy-/environment-wise. One effective way for the proper CDW handling is to utilize CDW components in producing geopolymers. This is reasonable given the fact that CDW generation is a global problem and CDW can be easily found anywhere in the world. In this study, it was aimed to analyze effects of activators type, usage rates and combinations on rheological and workability performance of CDW based geopolymer matrix. In that context, at first, mortar phase composed of wall and roof members including bricks, tiles, glass waste and concrete waste in which recycled aggregate was utilized, was investigated with empirical test methods. For detailed investigation, rheometer was used to understand rheological and workability characteristic of CDW based geopolymer in addition to empirical test methods. In that way, know-how about rheological and workability performance of CDW based geopolymer was formed as well as mechanical performance and it was made possible to select the correct activator according to the application needs by using the results of the thesis study.
Influence of self healing on the mechanical properties of geopolymer binder composites
Engineered geopolymer composites (EGC), is emerged through a combination of the geopolymer material developed as an alternative to Portland cement (PC), whose usage is increasing day by day with the growing population around the world and which is responsible for 8% of human-induced carbon dioxide (CO2) emission, together with the engineered cementitious composite (ECC) technology that is hundreds of times more ductile than conventional concrete by exhibiting strain hardening response and multiple micro-crack formation. As the rate of usage of Portland cement increases with each day, the harm to the environment also increases. For this reason, new generation environmentally friendly materials developed as an alternative to PC, obtained by activating aluminosilicate-based industrial by-products such as fly ash and metakaolin, with alkaline solutions are called geopolymers. Although the geopolymer material stands out with its high strength, thermal resistance, and environmental friendliness, it is a brittle material by nature, just like concrete. For this reason, the ductility problem must be eliminated to ensure the applicability of the geopolymer material, which is currently not very suitable for large-scale field applications. In addition, ECC, which can able to make high levels of deflection thanks to its micro-mechanical based design approach, has been used for years in dams, bridge-deck slabs, and large-scale field applications with various special requirements through its high strength and durability features and its applicability have been proven. For this reason, it is very important to develop engineered geopolymer composites due to the sustainability, protection of natural resources, and to meet the requirement for high strength and durability with the developing industry and technology. Construction demolition wastes (CDW) is one of the growing problems with the effect of the increasing population worldwide. Construction demolition wastes that emerged with the development of infrastructural systems, urban transformation, construction/demolition, and repair processes, constitute a serious problem due to the storage, pollution of natural resources, mixing with lean drinking water and soil. Therefore, rational solutions are required to eliminate this problem. In this thesis study, it is planned to recycle and reuse of CDW, which constitutes the majority of the wastes currently available worldwide, with the geopolymerization technique. Since it is an aluminosilicate source and easy to obtain, it is thought that CDWs are very suitable for geopolymerization. Cracks may occur in concrete due to infrastructure problems, difficulties in applications, and harsh environmental factors, and sometimes the properties of the material cannot be recovered as these cracks negatively affect both strength and durability. In this case, it is necessary to intervene as quickly as possible and begin the maintenance and repair processes. However, traditional maintenance and repair processes do not eliminate the problems, and in some cases, no maintenance and repair can be made due to structural constraints. Fast repair mortars and other repair materials produced by the developing technology also cause the result to be ineffective in terms of the high cost. For this reason, the self-repairing of the material without any external intervention eliminates cost/labor and increases the service life of the material. Although self-healing is observed in almost all types of Portland cement, it becomes very effective with the ECC material that can form multiple micro-cracks. Thanks to the researches in the literature, the effect of self-healing on the properties of concrete has been proven. However, a comprehensive study has not been performed in geopolymer systems yet, and therefore the functioning of the self-healing mechanism in geopolymer material is not fully known. The main purpose of this master's thesis study is to produce environmentally friendly engineered geopolymer composites that are obtained from 100% construction demolition wastes, exhibit high mechanical performance, can make high deflection by demonstrating strain hardening, can create multiple micro-crack damages, and to examine the effects of the self-healing behavior that have not found a chance to be studied much in the literature, on the mechanical properties of engineered geopolymer composites. To examine the composite development and autogenous self-healing behavior, which are the main points of the thesis, it is aimed to investigate the microstructure of the composites obtained by chemical analysis such as SEM-EDX, XRD, and FTIR, as well as comprehensive laboratory studies.
Influence of self healing on the mechanical properties of geopolymer binder composites
Engineered geopolymer composites (EGC), is emerged through a combination of the geopolymer material developed as an alternative to Portland cement (PC), whose usage is increasing day by day with the growing population around the world and which is responsible for 8% of human-induced carbon dioxide (CO2) emission, together with the engineered cementitious composite (ECC) technology that is hundreds of times more ductile than conventional concrete by exhibiting strain hardening response and multiple micro-crack formation. As the rate of usage of Portland cement increases with each day, the harm to the environment also increases. For this reason, new generation environmentally friendly materials developed as an alternative to PC, obtained by activating aluminosilicate-based industrial by-products such as fly ash and metakaolin, with alkaline solutions are called geopolymers. Although the geopolymer material stands out with its high strength, thermal resistance, and environmental friendliness, it is a brittle material by nature, just like concrete. For this reason, the ductility problem must be eliminated to ensure the applicability of the geopolymer material, which is currently not very suitable for large-scale field applications. In addition, ECC, which can able to make high levels of deflection thanks to its micro-mechanical based design approach, has been used for years in dams, bridge-deck slabs, and large-scale field applications with various special requirements through its high strength and durability features and its applicability have been proven. For this reason, it is very important to develop engineered geopolymer composites due to the sustainability, protection of natural resources, and to meet the requirement for high strength and durability with the developing industry and technology. Construction demolition wastes (CDW) is one of the growing problems with the effect of the increasing population worldwide. Construction demolition wastes that emerged with the development of infrastructural systems, urban transformation, construction/demolition, and repair processes, constitute a serious problem due to the storage, pollution of natural resources, mixing with lean drinking water and soil. Therefore, rational solutions are required to eliminate this problem. In this thesis study, it is planned to recycle and reuse of CDW, which constitutes the majority of the wastes currently available worldwide, with the geopolymerization technique. Since it is an aluminosilicate source and easy to obtain, it is thought that CDWs are very suitable for geopolymerization. Cracks may occur in concrete due to infrastructure problems, difficulties in applications, and harsh environmental factors, and sometimes the properties of the material cannot be recovered as these cracks negatively affect both strength and durability. In this case, it is necessary to intervene as quickly as possible and begin the maintenance and repair processes. However, traditional maintenance and repair processes do not eliminate the problems, and in some cases, no maintenance and repair can be made due to structural constraints. Fast repair mortars and other repair materials produced by the developing technology also cause the result to be ineffective in terms of the high cost. For this reason, the self-repairing of the material without any external intervention eliminates cost/labor and increases the service life of the material. Although self-healing is observed in almost all types of Portland cement, it becomes very effective with the ECC material that can form multiple micro-cracks. Thanks to the researches in the literature, the effect of self-healing on the properties of concrete has been proven. However, a comprehensive study has not been performed in geopolymer systems yet, and therefore the functioning of the self-healing mechanism in geopolymer material is not fully known. The main purpose of this master's thesis study is to produce environmentally friendly engineered geopolymer composites that are obtained from 100% construction demolition wastes, exhibit high mechanical performance, can make high deflection by demonstrating strain hardening, can create multiple micro-crack damages, and to examine the effects of the self-healing behavior that have not found a chance to be studied much in the literature, on the mechanical properties of engineered geopolymer composites. To examine the composite development and autogenous self-healing behavior, which are the main points of the thesis, it is aimed to investigate the microstructure of the composites obtained by chemical analysis such as SEM-EDX, XRD, and FTIR, as well as comprehensive laboratory studies.
Influence of self healing on the mechanical properties of geopolymer binder composites
Engineered geopolymer composites (EGC), is emerged through a combination of the geopolymer material developed as an alternative to Portland cement (PC), whose usage is increasing day by day with the growing population around the world and which is responsible for 8% of human-induced carbon dioxide (CO2) emission, together with the engineered cementitious composite (ECC) technology that is hundreds of times more ductile than conventional concrete by exhibiting strain hardening response and multiple micro-crack formation. As the rate of usage of Portland cement increases with each day, the harm to the environment also increases. For this reason, new generation environmentally friendly materials developed as an alternative to PC, obtained by activating aluminosilicate-based industrial by-products such as fly ash and metakaolin, with alkaline solutions are called geopolymers. Although the geopolymer material stands out with its high strength, thermal resistance, and environmental friendliness, it is a brittle material by nature, just like concrete. For this reason, the ductility problem must be eliminated to ensure the applicability of the geopolymer material, which is currently not very suitable for large-scale field applications. In addition, ECC, which can able to make high levels of deflection thanks to its micro-mechanical based design approach, has been used for years in dams, bridge-deck slabs, and large-scale field applications with various special requirements through its high strength and durability features and its applicability have been proven. For this reason, it is very important to develop engineered geopolymer composites due to the sustainability, protection of natural resources, and to meet the requirement for high strength and durability with the developing industry and technology. Construction demolition wastes (CDW) is one of the growing problems with the effect of the increasing population worldwide. Construction demolition wastes that emerged with the development of infrastructural systems, urban transformation, construction/demolition, and repair processes, constitute a serious problem due to the storage, pollution of natural resources, mixing with lean drinking water and soil. Therefore, rational solutions are required to eliminate this problem. In this thesis study, it is planned to recycle and reuse of CDW, which constitutes the majority of the wastes currently available worldwide, with the geopolymerization technique. Since it is an aluminosilicate source and easy to obtain, it is thought that CDWs are very suitable for geopolymerization. Cracks may occur in concrete due to infrastructure problems, difficulties in applications, and harsh environmental factors, and sometimes the properties of the material cannot be recovered as these cracks negatively affect both strength and durability. In this case, it is necessary to intervene as quickly as possible and begin the maintenance and repair processes. However, traditional maintenance and repair processes do not eliminate the problems, and in some cases, no maintenance and repair can be made due to structural constraints. Fast repair mortars and other repair materials produced by the developing technology also cause the result to be ineffective in terms of the high cost. For this reason, the self-repairing of the material without any external intervention eliminates cost/labor and increases the service life of the material. Although self-healing is observed in almost all types of Portland cement, it becomes very effective with the ECC material that can form multiple micro-cracks. Thanks to the researches in the literature, the effect of self-healing on the properties of concrete has been proven. However, a comprehensive study has not been performed in geopolymer systems yet, and therefore the functioning of the self-healing mechanism in geopolymer material is not fully known. The main purpose of this master's thesis study is to produce environmentally friendly engineered geopolymer composites that are obtained from 100% construction demolition wastes, exhibit high mechanical performance, can make high deflection by demonstrating strain hardening, can create multiple micro-crack damages, and to examine the effects of the self-healing behavior that have not found a chance to be studied much in the literature, on the mechanical properties of engineered geopolymer composites. To examine the composite development and autogenous self-healing behavior, which are the main points of the thesis, it is aimed to investigate the microstructure of the composites obtained by chemical analysis such as SEM-EDX, XRD, and FTIR, as well as comprehensive laboratory studies.
Influence of self healing on the mechanical properties of geopolymer binder composites
Engineered geopolymer composites (EGC), is emerged through a combination of the geopolymer material developed as an alternative to Portland cement (PC), whose usage is increasing day by day with the growing population around the world and which is responsible for 8% of human-induced carbon dioxide (CO2) emission, together with the engineered cementitious composite (ECC) technology that is hundreds of times more ductile than conventional concrete by exhibiting strain hardening response and multiple micro-crack formation. As the rate of usage of Portland cement increases with each day, the harm to the environment also increases. For this reason, new generation environmentally friendly materials developed as an alternative to PC, obtained by activating aluminosilicate-based industrial by-products such as fly ash and metakaolin, with alkaline solutions are called geopolymers. Although the geopolymer material stands out with its high strength, thermal resistance, and environmental friendliness, it is a brittle material by nature, just like concrete. For this reason, the ductility problem must be eliminated to ensure the applicability of the geopolymer material, which is currently not very suitable for large-scale field applications. In addition, ECC, which can able to make high levels of deflection thanks to its micro-mechanical based design approach, has been used for years in dams, bridge-deck slabs, and large-scale field applications with various special requirements through its high strength and durability features and its applicability have been proven. For this reason, it is very important to develop engineered geopolymer composites due to the sustainability, protection of natural resources, and to meet the requirement for high strength and durability with the developing industry and technology. Construction demolition wastes (CDW) is one of the growing problems with the effect of the increasing population worldwide. Construction demolition wastes that emerged with the development of infrastructural systems, urban transformation, construction/demolition, and repair processes, constitute a serious problem due to the storage, pollution of natural resources, mixing with lean drinking water and soil. Therefore, rational solutions are required to eliminate this problem. In this thesis study, it is planned to recycle and reuse of CDW, which constitutes the majority of the wastes currently available worldwide, with the geopolymerization technique. Since it is an aluminosilicate source and easy to obtain, it is thought that CDWs are very suitable for geopolymerization. Cracks may occur in concrete due to infrastructure problems, difficulties in applications, and harsh environmental factors, and sometimes the properties of the material cannot be recovered as these cracks negatively affect both strength and durability. In this case, it is necessary to intervene as quickly as possible and begin the maintenance and repair processes. However, traditional maintenance and repair processes do not eliminate the problems, and in some cases, no maintenance and repair can be made due to structural constraints. Fast repair mortars and other repair materials produced by the developing technology also cause the result to be ineffective in terms of the high cost. For this reason, the self-repairing of the material without any external intervention eliminates cost/labor and increases the service life of the material. Although self-healing is observed in almost all types of Portland cement, it becomes very effective with the ECC material that can form multiple micro-cracks. Thanks to the researches in the literature, the effect of self-healing on the properties of concrete has been proven. However, a comprehensive study has not been performed in geopolymer systems yet, and therefore the functioning of the self-healing mechanism in geopolymer material is not fully known. The main purpose of this master's thesis study is to produce environmentally friendly engineered geopolymer composites that are obtained from 100% construction demolition wastes, exhibit high mechanical performance, can make high deflection by demonstrating strain hardening, can create multiple micro-crack damages, and to examine the effects of the self-healing behavior that have not found a chance to be studied much in the literature, on the mechanical properties of engineered geopolymer composites. To examine the composite development and autogenous self-healing behavior, which are the main points of the thesis, it is aimed to investigate the microstructure of the composites obtained by chemical analysis such as SEM-EDX, XRD, and FTIR, as well as comprehensive laboratory studies.