Bahar Demirel

This study investigates the use of glass powder (GP) as a sustainable alternative to cement in the production of lightweight concrete, addressing the environmental footprint reduction and waste management of traditional concrete materials. In this study, 8 different concrete series were produced by substituting CT with cement in varying ratios. The produced samples were cured using standard methods and kept in MgSO4 and Na2SO4 solutions for specific periods of time, and their mechanical performance and microstructural properties were evaluated. As a result of the tests performed on the concrete specimens obtained, it was found that 5% and 10% GP substitution provided maximum performance. The originality of the study is the feasibility of reducing the amount of cement while maintaining the performance of lightweight concrete and it is thought to contribute significantly to sustainability studies. In addition, the use of GP in concrete production reduces material weight, contributes to sustainable construction practices and offers a viable alternative in lightweight concrete production.

In this study, it is aimed to predict the performance of concretes obtained by using supplementary cementitious materials (SCM) before and after high temperature using artificial neural network. Thus, in addition to contributing to sustainable development and circular economy by using waste materials in concrete production, predicting concrete strength using artificial neural network without the need for experimental studies will provide a great advantage in practice. In addition, it will also contribute to the literature in terms of determining the optimum amount of metakaolin to be used with fly ash in concrete production. Metakaolin, silica fume and fly ash were used as SCM in different proportions in concrete mixes. Accordingly, a total of 22 concrete series were prepared, one of which was the control series. Porosity, ultrasonic pulse velocity, pressure and tensile strength tests were applied to the series at the end of 7th, 28th and 90th curing periods before high temperature. In order to determine the strength losses after elevated temperature, porosity and compressive strength tests were applied at temperatures of 400, 600 and 800 °C. Mineral additive series showed positive mechanical properties up to 20%. However, it has been observed that the use of fly ash after a certain rate causes a decrease in strength. After elevated temperature, strength loss was observed in all series due to the increase in temperature, while it was observed that the rate of being affected by elevated temperature decreased as the percentage of metakaolin increased. Optimum mineral additive usage percentages were determined as 10% fly ash and 15% metakaolin. On the other hand, the use of mineral additives above the optimum level caused the performance of the concrete to decrease. Then, the concrete compression strengths obtained at 7th, 28th, and 90th days and at 400, 600 and 800 °C temperatures are taken as the outputs of the ANN. The artificial neural network provided the closest results to experimental data. Moreover, to prove the predictive performance of ANN, a comparative analysis was made with GPR, SVM and LR and the smallest value of the RMSE value is obtained with the ANN model. Finally, a fivefold cross-validation criteria was used to objectively present the performance of the model.

Bu çalışmanın amacı atık cam tozu kullanılarak üretilen betonların yüksek sıcaklık öncesi ve sonrası dayanım performanslarındaki değişimini araştırmaktır. Bu doğrultuda, farklı atık cam tozu ikame oranı içeren 6 farklı beton karışım serisi hazırlanmıştır. Üretilen beton serileri üzerinde mekanik testler içeren deneysel bir program yürütülmüştür. Kür süresini tamamlayan beton serileri, sırasıyla 400 oC, 600 oC, 800 oC’de, 1 saat yüksek sıcaklıkta bekletilmiştir. Bu beton gruplarının yüksek sıcaklık sonrası basınç dayanımı kayıpları belirlenmiştir. Betonda atık cam tozu ikamesinin artmasıyla betonun mekanik özelliklerinde azalma görülmüştür. Öte yandan en iyi sonuç cam tozu oranının %10 oranında kullanıldığı serilerde gözlenmiştir. Betonda cam tozu oranının %10’a kadar kullanımının betonun performansını arttırdığı gözlenmiştir. Sonuç olarak, atık atık cam tozunun yüksek sıcaklığa dayanıklı beton üretiminde çimento ikame malzemesi olarak kullanılabileceği görülmüştür. Çimento miktarında yapılacak bu azaltma ile karbon ayak izi azaltılmış daha çevreci bir beton üretiminin mümkün olabileceği görülmüştür. Ayrıca beton üretiminde atık cam tozu kullanımının, atık yönetimine çözüm ve döngüsel ekonomiye katkı sağlayarak inşaat sektörü için potansiyel bir seçenek haline gelmektedir.

The aim of this study is to examine the effect of replacing waste aluminum sawdust (AS) with fine aggregate on the strength and durability properties of concrete. For this, concrete mixtures with a cement dosage of 400 kg/m3, water/cement (W/C) ratio of 0.40-0.50-0.60 were prepared. Aluminum sawdust obtained from Elazığ industrial site was added to the concrete mixtures by replacing 0%, 0.5% and 1% fine aggregate by volume. After curing in the curing pool for 28 days, the produced concrete samples were placed in the carbonation tank and exposed to the accelerated carbonation test in three different time periods as the 1st, 3rd and 7th days. Tests of compressive strength, splitting tensile strength, ultrasound transmission velocity, porosity and carbonation depth were performed on concrete samples before and after carbonation. The samples that were exposed to carbonation were compared with the samples that did not undergo carbonation. In addition, the microstructure of AS concrete was investigated using scanning electron microscopic images (SEM). In the microscopic images, larger cracks, openings and interfacial voids were observed in the concrete matrix with the addition of AS. However, due to the formation of ettringite in these gaps and cracks after carbonation, the cavities became smaller. As a result of the experiments, it was observed that the optimum W/C ratio was 40% and the AS amount was 0.5% in the use of AS in concrete. In addition, it was found that the carbonation effect improves the compressive and splitting tensile strength and increases the ultrasound transmission rate. Finally, life cycle assessment (LCA) was conducted to evaluate the environmental impacts of the prepared concrete samples. Considering the large amount of natural aggregate consumption, it is thought that the use of waste materials in concrete will provide environmental and economic benefits.

The aim of this study is to examine the effect of replacing waste aluminum sawdust (AS) with fine aggregate on the strength and durability properties of concrete. For this, concrete mixtures with a cement dosage of 400 kg/m3 and water/cement (W/C) ratio of 0.40-0.50-0.60 were prepared. AS obtained from Elazig industrial site was added to the concrete mixtures by replacing 0%, 0.5% and 1% fine aggregate by volume. After curing in the curing pool for 28 days, the produced concrete samples were subjected to accelerated carbonation test in the carbonation tank at three different time periods the 1st, 3rd and 7th days. Compressive strength test and carbonation depth measurement test were performed on the samples before and after carbonation. In addition, the microstructure of AS concrete was investigated using scanning electron microscopic images (SEM). In the microscopic images, larger cracks, openings and interfacial voids were observed in the concrete matrix with the addition of AS. In addition, it has been observed that the carbonation effect contributes to the compressive strength.

Bu çalışmanın amacı, farklı su/bağlayıcı ve kimyasal katkı oranına sahip yüksek dayanımlı betonların dayanım ve işlenebilirlik özelliklerini incelemektir. Bu kapsamda çimento dozajı 400 ve 600 kg/m3, su/bağlayıcı (S/B) oranları 0.20 ve 0.30 olan 16 seri beton karışımı hazırlanmıştır. Bu beton karışımlarında mineral katkı olarak puzolanik aktivitesi yüksek olan silis dumanı kullanılmıştır. Silis dumanı %5 ve %20 oranlarında çimento ile hacimce yer değiştirilerek kullanılmıştır. Kimyasal katkı ise çimentonun ağırlıkça %2 ve %3’ü oranında kullanılmıştır. Bu karışım oranları ile hazırlanan, yüksek dayanım elde edilmiş serilerin taze ve sertleşmiş beton (mekanik) özellikleri araştırılmıştır. Bu araştırma sonucunda serilerin slump, ve ve-be değerleri ile fc-7, fc-28 ve fc-90 günlük sonuçları karşılaştırılmıştır. Bu karşılaştırma sonucunda yüksek dayanımlı betonlarda (YDB) kimyasal katkı kullanımının işlenebilirlik üzerinde önemli faktör olduğu tespit edilmiştir. Bununla birlikte düşük S/B oranında, yeterli miktarda kimyasal katkı ve optimum silis dumanı miktarı ile yüksek dayanıma sahip betonların elde edilebildiği görülmüştür.