Sürdürülebilir Kalkınma Amaçları
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- MakaleAçık Erişim2025Slag Substitution Effect on Features of Alkali-Free Accelerator-Reinforced Cemented Paste Backfill
Cavusoglu, Ibrahim
Cemented paste backfill (CPB) improves underground stability by filling mine voids, but the high cost of cement presents economic challenges for miners. While alternative binders and admixtures have been explored, the combined impact of slag substitution and alkali-free (AF) accelerators on CPB performance is not yet fully understood. This study investigates the influences of slag substitution and AF accelerators on the performance of CPB through a comprehensive experimental approach. CPB samples were prepared with slag substitution ratios of 25%, 50%, and 75%, maintaining a fixed AF accelerator content of 0.4%. Various test techniques, including unconfined comprehensive strength (UCS), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), and thermal analysis (TG/DTA), were employed to study their mechanical and microstructural properties. Monitoring tests were also conducted to thoroughly assess the performance of CPB, including suction (self-desiccation), electrical conductivity (EC), and volumetric water content (VWC) tests. The results showed that the PCI50–SL50–0.4AF sample exhibited 2.3 times higher strength than the control sample for 28 days, with this improvement attributed to enhanced pozzolanic reactions contributing to better microstructural compactness. Monitoring tests revealed accelerated hydration kinetics and reduced water content in slag-reinforced CPB, highlighting the significant role of AF accelerator in facilitating rapid setting and improving early-age mechanical strength. Microstructural findings revealed that porosity decreased and C–S–H gel formation increased in the specimen containing slag and AF accelerators, contributing to increased strength and durability. These findings highlight the potential usage of slag and AF accelerators to enhance CPB’s mechanical, microstructural, and hydration properties, offering significant benefits for mining operations by improving backfill performance, while contributing to environmental sustainability through reduced cement consumption and associated CO2 emissions.
- MakaleAçık Erişim2024Superplasticizer Dosage Effect on Strength, Microstructure and Permeability Enhancement of Cementitious Paste Fills
Cavusoglu, Ibrahim
A cementitious paste fill (CPF) ensures the long-age stability of underground cavities. Recently, superplasticizers, specifically ones that are polycarboxylate ether-based, have been incorporated to enhance CPF performance, yet their long-term effects on permeability, mechanical properties, and microstructures remain unclear. This study investigates these effects with CPF samples containing varying superplasticizer dosages (0%, 1%, 3%, 5%) that have been cured for up to 150 days. Rheological assessments (slump cone, vane shear tests), unconfined compressive strength testing, microstructural characterization (MIP, SEM), and hydraulic conductivity measurements were performed alongside XRD and thermal analyses (TAns) on high w/c (2) cement paste samples. The results showed that superplasticizer addition reduced CPF water content by 23% and yield stress by six times, aiding slurry transport. Long-term strength was enhanced by up to 2.4 times compared to the control samples, indicating improved underground stability. Superplasticizers altered the CPF samples stress–strain responses, increasing their load-bearing capacity. TG/DTG and XRD analyses revealed that hydration product development increased and porosity decreased in the presence of a superplasticizer. Hydraulic conductivity and permeability also decreased significantly. SEM and MIP analyses showed that the superplasticizer enhanced denser microstructures with fewer pores and fractures. These findings offer promising implications for designing CPFs with improved strength, durability, and environmental sustainability.
- 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.
- MakaleAçık Erişim2023Engineering Properties of Cemented Paste Backfill with Full-Range Water-Reducing Admixture
Cavusoglu, Ibrahim; Fall, Mamadou
This paper presents the effects of a full-range water-reducing (FRWR) admixture on the key engineering properties of cemented paste backfill (CPB). CPB samples with a certain slump are prepared with 4.5% cement by mass of the tailings and different dosages of an FRWR admixture (superplasticizer contents of 1%, 3%, and 5%) to evaluate their water demand during hydration, rheological properties, self-desiccation ability, and microstructural and mechanical properties. Moreover, cement paste samples with a high water-to-cement ratio (w/c = 2) which are used to model the cement matrix of the CPB are prepared for x-ray diffraction (XRD) scanning and thermal analyses (TAns). The results show that the addition of an FRWR admixture to the studied CPB can reduce its water demand by up to 23% and significantly increase its strength from 1.0 MPa to 2.38 MPa (by approximately 2.4 times) at 28 days. The pore volume of the CPB samples is also significantly reduced from 27.17 to 18.27% due to the capability of the FRWR admixture to reduce water demand. Also, the addition of an FRWR admixture to the CPB results in a substantial decrease (up to 83%) of its yield stress, thereby improving its flowability. The CPB samples with an FRWR admixture are found to have a higher negative pore water pressure, i.e., higher self-desiccation, than the CPB sample without an FRWR admixture. The microstructural analysis also shows that the FRWR admixture has an increasing effect on the hydration products in the CPB mixture.
- 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.
- Derleme MakaleYalnız künye2012Hydropower for sustainable energy development in Turkey: The small hydropower case of the Eastern Black Sea Region
Capik, Mehmet; Osman Ylmaz, Ali; Cavusoglu, Ibrahim
Turkey is a rich country from the point of variety and potential of renewable energy resources. Hydros, winds, biomass, solar and geothermal are important renewable and environmentally friendly sources for energy in Turkey. Turkey produces large amount of hydropower with a total gross hydropower potential of 433 TW h/yr, which is equal to 13.8% of the total hydropower potential of Europe. Technically useable potential is 216 TW h/yr and economic potential is 140 TW h/yr. The main aim of the present study is to investigate hydropower potential of Turkey and small hydropower plants in Eastern Black Sea Region for sustainable energy development in Turkey. The geography of Turkey especially, Eastern Black Sea Region supports and suitable the development of the small hydro plants to increase the energy generation and utilization of available water sources in Turkey. Besides, the paper deals with hydropower policies to meet ever increasing energy demand for sustainable development of Turkey.