Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2023Evaluation of Pozzolanic Activity of Two Different Types of C and F Fly Ashes with Fineness Factor
Sahin, Demet Demir; Cavusoglu, Ibrahim; Yilmaz, Ali Osman
Today, energy produced from coal is economical compared to other sources but it faces a very serious waste problem. However, these wastes are evaluated by using them as mineral additives in cement, which leads to lower cement costs, saving resources, producing environmentally friendly cement, reducing CO2 gas, and producing high-strength cement. In this work, the pozzolanic properties of different types of fly ash (Afşin Elbistan C type and Çayırhan F type) are investigated. The fly ashes used in the study are first subjected to the milling process (10, 20, 30, 45, and 60 minutes), and then the 28 and 90-day pozzolanic activity index tests of the milled and unmilled ashes are performed. The results obtained show that the 28-day pozzolanic activity value of the ashes subjected to 20-, 30-, 45-, and 60-minute milling times are higher than the value specified in the standard, compared to the unmilled and 10 min milled fly ash. In addition, for all fly ash samples, the 90-day pozzolanic activity index results show that while the pozzolanic activity index value of Çayırhan (ÇYH) fly ash is higher than the standard value, that of Afşin Elbistan (AE) fly ash is lower than standard. The outcomes of the present study show that the mechanical properties of the fly ash are generated by the burning of coal increase after milling process, and thus can be used as a mineral additive. With the effect of grinding, both fly ash increase the pozzolanic activity. The results are determined with the experimental results obtained.
- MakaleYalnız künye2021Sodium silicate effect on setting properties, strength behavior and microstructure of cemented coal fly ash backfill
Cavusoglu, Ibrahim; Yilmaz, Erol; Yilmaz, Ali Osman
Representing an engineered mixture of coal fly ash, cement and water, cemented coal fly ash backfill (CCB) is typically employed for filling the openings created after coal excavation in the earth. A high rate of productivity for coal mines requires a high early-age strength backfill design. Therefore, the use of admixtures in CCB is key for accelerating the backfill setting time and augmenting short-and long-term strength. This study offers the effect of sodium silicate (SS) as an accelerator on early age mechanical and microstructure properties of CCB. SS-based admixture was used for a dosage of 0.5, 1 and 1.5 wt% in CCB that contains 25 wt% ordinary Portland cement OPC and 75 wt% coal fly ash. Backfill setting time was done by using the Vicat system while its strength and pore structure were measured by using the uniaxial compressive strength test, and scanning electron microscopy and Hg intrusion porosimetry. Results display that use of SS in CCB increases its short-term strength gain up to 14% and shortens the mining cycle by cutting its setting time up to 58%. The microstructure analyses also indicate that CCB formulated with SS has a finer pore structure than that without admixture. The outcomes of the present study will be advantageous to evaluate both setting time and strength behavior of CCB used in coal mines, thereby causing the effective backfill plan in terms of money saving and easy operation.
- MakaleYalnız künye2021Additivity effect on properties of cemented coal fly ash backfill containing water-reducing admixtures
Cavusoglu, Ibrahim; Yilmaz, Erol; Yilmaz, Ali Osman
Cemented coal fly ash backfill (CCB), a flowable structure of coal fly ash, binding agent and mixing water, has been often employed in mining operations to offer ground support as well as waste disposal solutions. An appropriate CCB mass should have sufficient rheological (e.g., workability) and mechanical (e.g., strength and stability) characteristics. Chemical admixtures are well known to greatly enhance the pumpability and strength properties of cementitious materials. Thus, this work provides the effect of water-reducing admixtures (namely, Sikament MR 50 W and Sikament FFN) on characteristics of CCB materials manufactured at a constant slump value. The role of admixtures in CCB mix is to reduce the cement-related costs, to modify the properties of the hardened backfills, and to ensure the quality of the backfill during mixing, transporting, placing, and curing. These admixtures were used at a dosage of 1% and 2% by weight of anhydrous material on cement. Several laboratory tests including slump, setting time, uniaxial compressive strength, scanning electron microscopy and mercury intrusion porosimetry were undertaken on CCB samples to understand their fresh and hardened performance. Experimental results show that the admixtures used ensure the slump required to deliver CCB at low water/cement ratios, improve short- and long-term backfill strengths up to 33%, and decrease the total porosity of the tested CCB. The findings of this study also show that the admixture use in CCB leads to a significant decrease in the considered cement content and a remarkable increase in the mechanical strength. As a result, understanding the actual fresh and hardened properties of CCB remains crucial for the choice of the greatest acting backfill admixture and for a fruitful change from capable experimental results to the in-situ conditions.
- MakaleYalnız künye2021Experimental Investigation of Usability of Construction Waste as Aggregate
Kulekci, Gokhan; Yilmaz, Ali Osman; Cullu, Mustafa
The aim of this work is to obtain recycled aggregate (RA) from construction debris in order to reduce the rapid consumption of aggregate resources and the environmental impact of these resources. In order to fulfill this aim, the density, porosity, Schmidt hardness test, uniaxial compression resistance, carbonation depth, and ultrasonic p-wave velocity experiments were conducted on different construction debris transported by trucks from 9 different points in Turkey. In addition, the debris samples taken were broken down to the size of the aggregate and subjected to the tests of density, porosity, moisture content, freeze-thaw, and impact resistance. As a result of the conducted experiments, the lowest mass loss as a result of freezing-thawing was in GRA with 9.36%, the highest mass loss was in ORA with 22.58%, the highest ORA average aggregate impact strength index was 21.27%, and the lowest TRA aggregate impact strength index was found to be 18.26%. İt was determined that most of the physical properties of RA obtained from the construction wreckage was within the limit values specified in the literature and that the recycled aggregates could be used instead of natural aggregate. With this work and these results, RA obtained could be used in many areas such as concrete aggregate in the construction sector, underground filling in mining, filling material in gunned concrete, and filling materials on highways.
- Derleme MakaleYalnız künye2012Present situation and potential role of renewable energy in Turkey
Çapik, Mehmet; Yilmaz, Ali Osman; Çavuşoĝlu, Ibrahim
Turkey has a rich potential of hydropower, wind and geothermal energy resources. The distribution of these renewable energy sources in operation are hydropower, wind and geothermal 14.802 MW 1002MW and 94 MW, respectively. Turkey possesses a huge hydroelectric resource which is one of the Turkey's major energy assets. Most of the important uses of water in power plants have been developed in the electricity generation. Turkey has a total gross hydropower potential of 433 TWh/yr, which is equal to 13.8% of the total hydropower potential of European. Technically useable and economic potential are 216 TWh/yr and 140 TWh/yr, respectively. The total share of all energy for electricity power generation in 2010 are coal, natural gas, fuel oil and renewable energy, 104,040 GWh, 125,549 GWh, 18,215 GWh, and 86,120 GWh respectively. Among the renewable energy resources in Turkey, biomass and solar energy are also important because their share in total energy consumptions have increased. On the other hand, Turkey has not utilized nuclear energy yet. The current government plans to have a nuclear power plant with a capacity of 1800MW at the Black Sea Port of Sinop. The main purpose of the energy policies is to answer the energy needs of increasing population and growing economy at minimum costs while making energy supply planning. Turkey's specific national energy strategy document and energy policy objectives are outlined in the institutional strategic plans. These strategic plans are energy supply security, regional and global influence in the area of energy and environment protection. The aim of energy policy including renewable are to develop existing energy sources and to avoid dependence on energy imports and to encourage private sector investment and to improve the reliability of electricity supply. The main aim this study will investigate at the present potential of energy resources and future contributions to the national energy consumption in Turkey. As result present energy situation, the renewable energy potential, and the energy politics of Turkey are investigated.
- MakaleYalnız künye2011Doğal taş ocaklarında blok hacminin belirlenmesi için RQD ve Jᵥ’nin kullanılabilirliği
Yilmaz, Ali Osman; Çapik, Mehmet; Kaya, Ayberk; Alemdag, Selcuk
Bu çalışmada, Doğankent (Giresun) yöresinde yüzeylenen Harşit Granitoyidi’nden üretilebilecek blokların hacminin belirlenmesinde, Kaya Kalite Göstergesi (RQD) ve Hacimsel Eklem Sayısı (J ᵥ) parametrelerinin kullanılabilirliği araştırılmıştır. Bu amaçla, pilot çalışma alanı olarak bir ocak seçilmiş ve açılan şevlerde hat etüdü çalışmaları yapılarak, süreksizliklerin özellikleri tayin edilmiştir. Harşit Granitoyidi’nden elde edilebilecek Blok Hacminin belirlenmesinde Kaya Kütle İndeksi (RMi) sınıflama sisteminde girdi parametresi olan blok hacmi (Vb) kullanılmıştır. Vb değerinin belirlenmesinde kullanılan Jv ve RQD değişkenleri ocak içindeki farklı şevlerde yapılan süreksizlikler arası ölçümler ile belirlenmiştir. RMi sınıflamasında kullanılan Blok Şekli Faktörüne (β) göre yapılan değerlendirmede blokların genellikle “kompakt, hafifçe uzun-düz” şekilli olduğu tesbit edilmiştir. Blok hacminin belirlenmesinde kullanılan parametrelerden RQD değişkeninin sınırlamalar içermesi nedeniyle, blok hacminin hesaplanmasında J ᵥ değerlerinin kullanılması tercih edilmiştir. Yapılan değerlendirmeler sonucunda Harşit Granitoyidi’nden üretilecek blokların ortalama hacminin Vb= 7.15 m³ olduğu belirlenmiş olup, bu değer ticari olarak değerlendirilebilecek blok hacmi aralığındadır.