EFFECT OF NAOH MOLARITIES ON STRENGTH PROPERTIES OF GROUND PERLITE-BASED GEOPOLYMER MORTARS

Geopolymers are the eco-friendly binders derived from activation of alumina silicates such as fly ash and metakaolin with alkaline activators. Ground perlite, a volcanic alumina silicate, has a potential to be a precursor material for geopolymer production due to its high SiO2 content and amorphous form. This paper presents the investigation of geopolymer production with ground perlite and NaOH. For this purpose, mortar mixtures are prepared with four different NaOH solutions (3M, 6M, 9M and 12M). Mortar specimens with dimensions of 4*4*16 cm are taken from the mixtures and heat curing process is applied to the specimens after casting. The flexural and compressive strength tests are conducted on the mortar specimens at 7 and 28 days of curing. The test results showed that the flexural and compressive strengths of the ground perlite based geopolymer mortars are increased with the molarity of NaOH solution, significantly

UTILIZATION OF CHROME ORE CONCENTRATION PLANT TAILINGS AS FINE AGGREGATE IN READY-MIXED CONCRETE

Large amount of the chrome ore concentration plant tailings was discarded during chrome ore mining process. The accumulation of the tailings takes large areas of land for the storage and causes environmental and safety problems. When the annual consumption of the ready mixed concrete per person (approximately 1.5 m3/person) in Turkey is considered, employment of the tailings in the ready-mixed concrete may be a solution for the recovery of the tailings. In addition, using chrome tailings as a substitution for sand to produce ready-mixed concrete is a possible way to solve the resource problem of sand deficiency. The aim of this study is to investigate the utilization of the tailings taken from a chrome ore concentration plant in Eskisehir, Turkey as fine aggregate in ready-mixed concrete production. For this purpose, the tailings were partially replaced with the fine aggregate by the weight at 0, 10, 20 and 30% proportions by weight in the ready-mixed concrete mixtures. Standard curing is applied until the time of test to the 15x15x15 cm cube specimens taken from the mixtures.  The unit weight, compressive strength and ultrasonic pulse velocity values of the cubic specimens were investigated in this study. Performed tests showed that replacing sand to chrome ore tailings has a potential for further investigations. 

ATIK ANDEZİT VE MERMER TOZUNUN ÇİMENTO HARÇLARININ DAYANIM ÖZELLİKLERİNE ETKİSİ

The sludge generated during cutting of andesite and marble stones is stored in powder form after drying. Due to the wide usage area and consumption of marble and andesite, the storage problem of these wastes arises. Therefore, it is important to eliminate the storage problems of these wastes and to recover them to the economy. For this purpose, in this study, mortar samples were produced using 5%, 10%, 15% and 20% of waste andesite and marble powder separately instead of cement. Ultrasound pulse velocity, flexural and compressive strength tests were carried out on the produced samples. The experimental results showed that the most suitable substitution rate of marble powder used in this study is 10% and andesite powder 15%. In addition, the highest flexural and compressive strength values were achieved in mortars with 15% andesite powder substitution instead of cement

Evaluation of Right Ventricular Global Longitudinal Strain in COVID-19 Patients After Intensive Care Unit Discharge

Background and Aim:Using two-dimensional speckle tracking echocardiography (2D-STE), the ventricular functions of hospitalized coronavirus disease-2019 (COVID-19) patients were assessed. However, there is limited information about cardiac functions in the first year after recovery from the intensive care unit (ICU). This research aims to assess the right ventricular functions of COVID-19 patients and their changes within the first year after ICU discharge using 2D-STE.Materials and Methods:The study was conducted prospectively. The study included 68 consecutive patients and 70 control patients. Echocardiography was performed in the ICU and the first year after discharge from the hospital. Right ventricular global longitudinal strain (RVGLS) was measured using the 2D-STE method.Results:The mean age of the study group was 48.67±8.10 and 37 (54.4%) patients were males. There were no substantial differences across the groups, including age, gender, body mass index, heart rate, diabetes, dyslipidemia, and smoking (P > 0.05). A substantially significant positive correlation was detected between right ventricular dimension (RAD) (r = 0.644, P < 0.001), right ventricular diastolic dimension (RVDD) (r = 0.573, P < 0.001), ferritin (r = 0.454, P < 0.001), D-dimer (r = 0.305, P = 0.011) values and RVGLS in the in-hospital and after-discharge first-year groups. The RVGLS values of the control, in-hospital, and after-discharge first-year groups were -20.36±3.06, -16.98±3.78, and -17.58±6.45, indicating a statistically significant difference across the groups (P < 0.001). Tricuspid annular plane systolic excursion was higher in the control group (P < 0.05).Conclusion:RVGLS was found to be depressed during the in-hospital period and showed no improvement in the 1 year post discharge

Effect of metakaolin and ground pumice on the properties of high strength concrete containing steel fiber

Bu çalışmada çelik fiber içeren yüksek dayanımlı beton özellikleri üzerine metakaolin, öğütülmüş pomza ve metakaolin ile birlikte kullanılan öğütülmüş pomzanın etkileri deneysel olarak araştırılmıştır. Deneysel çalışmada, kontrol betonlarından hariç 6 farklı seride bu mineral katkılar kullanılarak 30 farklı karışımda beton üretilmiştir. Birinci seride, çimento yerine ağırlıkça metakaolin, ikinci seride çimento yerine ağırlıkça öğütülmüş pomza ve üçüncü seride çimento yerine ağırlıkça metakaolin ile birlikte öğütülmüş pomza yer değiştirilerek 7 farklı kombinasyonda kullanılmıştır. Diğer seriler ise ilk üç serideki karışımlara çelik fiber eklenerek üretilmiştir. Ayrıca tüm karışımlarda bağlayıcı miktarı 500 kg/m³, su-bağlayıcı oranı 0.20 ve çökme değerleri 8 +- 2 cm olarak belirlenmiştir. Karışımlarda, su miktarını azaltmak ve sabit bir çökme değerini belirlemek için yüksek oranda su azaltıcı özelliğe sahip süper akışkanlaştırıcı farklı oranlarda kullanılmıştır. Taze beton özelliklerinden çökme ve taze birim ağırlık deneyleri yapılmıştır. Sertleşmiş beton özelliklerinden ise sertleşmiş birim ağırlık, ultra ses geçiş hızı, basınç dayanımı, eğilme dayanımı ve yarmada çekme dayanımı değerleri deneysel olarak belirlenmiştir. Kontrol betonları ile diğer serilerdeki betonlardan elde edilen deneysel sonuçlar karşılaştırılmıştır. Ayrıca, farklı serilerdeki betonlar da birbirleri ile karşılaştırılmış ve en uygun mineral katkı oranları belirlenmeye çalışılmıştır. Karşılaştırmalarda metakaolin içeren betonların performansının diğerlerine göre daha yüksek olduğu gözlenmiştir. Sonuç olarak, tüm serilerde yüksek dayanımlı beton elde edilebileceği gözlenmiştir.In this study has been experimentally investigated the effects of metakaolin, ground pumice and metakaolin together with ground pumice on the properties of high performance concrete containing steel fiber. In the study, except for control concretes by using these mineral additions in six different series, 30 different mixtures were produced. In the first series, metakaolin was used to replace by weight of Portland cement, in the second series, ground pumice was used to replace by weight of Portland cement, and also in the third series, ground pumice was used in the seven different combinations to replace by weight of Portland cement together with metakaolin to replace by weight of Portland cement. The other series were produced by adding steel fiber to previous series. Also, in the all mixtures, a constant total binder content of 500 kg/m³, the water-binder ratios of 0.20 and slump values of 82 cm were designed. The superplasticizer, which has high ratio of water reducing effect, was used in different proportions to reduce the water proportion and determine the value of constant slump value in the mixtures. The slump and unit weight of fresh concrete properties were tested. The hardened unit weight, ultrasound pulse velocity, compressive strength, flexural strength and splitting tensile strength values of hardened concrete properties were also experimentally determined. The results of control concretes were compared with the results of other series. The results of concrete in the different series were also compared with the results of each other, and tried to determine optimum ratios of mineral additives. As a result, it is seen that high strength concrete can be obtained in all series

Investigation of the properties of alkali-activated lightweight concretes

Bu çalışmada, alkali ile aktive edilmiş hafif betonların özellikleri araştırılmıştır. Deneysel çalışma iki aşamada gerçekleştirilmiştir. İlk aşamada Portland çimentolu kontrol karışımı hariç, 5 farklı seride 57 farklı alkali ile aktive edilmiş harç karışımı üretilmiştir. Alkali ile aktive edilmiş harç karışımlarında bağlayıcı malzeme olarak yüksek fırın cürufu ve uçucu kül, alkali aktivatör olarak da sodyum hidroksit ve sodyum silikat farklı oranlarda kullanılmıştır. Üretilen harçların birim ağırlık, ultrases geçiş hızı (Upv), eğilme dayanımı (ffs) ve basınç dayanımı (fc) değerleri deneysel olarak belirlenmiştir. Ayrıca, seçilen harçlar üzerinde yüksek sıcaklık deneyi gerçekleştirilmiş, harçların birim ağırlık, Upv, ffs ve fc değerlerinde yüksek sıcaklık etkisiyle meydana gelen değişimler irdelenmiştir. İkinci aşamada ise öncelikle her bir harç serisinden en iyi mekanik özelliklere sahip 2 harç karışımı seçilmiştir. Portland çimentolu kontrol karışımından hariç, seçilen harç karışımları ile aynı bağlayıcı faza sahip 10 farklı hafif beton karışımı üretilmiştir. Beton karışımlarında bağlayıcı miktarı 500 kg/m3 ve su:bağlayıcı oranı 0.48 olarak belirlenmiştir. Beton karışımlarında agrega olarak farklı miktarlarda bazik pomza agregası kullanılmıştır. Hafif betonların çökme, birim ağırlık, su emme, kılcal su emme, Upv, ffs, fsts ve fc değerleri deneysel olarak belirlenmiştir. Bununla birlikte, betonların ağırlık ve fc değerlerinde asit, sülfat ve yüksek sıcaklık etkisiyle meydana gelen değişimler incelenmiştir. Ayrıca, yüksek sıcaklık etkisinin seçilen harçların ve hafif betonların mikro yapılarında ve mineralojik kompozisyonlarında meydana getirdiği değişimler incelenmiştir.In this study, properties of alkali-activated lightweight concretes are investigated. This experimental study is performed in two stages. In the first stage, except from the control mortars produced with Portland cement, 57 different alkali-activated mortar mixtures in 5 series are manufactured. Blast furnace slag and fly ash are employed as precursors and sodium hydroxide and sodium silicate are used as the alkali activators at different ratios in the alkali-activated mortar mixtures. The unit weight, Ultsound pulse velocity (Upv), flexural strength (ffs) and compressive strength (fc) values of the mortars are determined experimentally. In addition, after high temperature exposure, the changes in the unit weight, Upv, ffs and fc values of the selected mortars are investigated. In the second stage, two mortar mixtures have the highest mechanical properties in each series are selected. Except from the control mixture made with Portland cement, 10 different lightweight concrete mixtures which have the same binding phase with the selected 10 mortar mixtures are produced. The binder dosage and water to binder ratio of the concrete mixtures are determined as 500 kg/m3 and 0.48, respectively. Basaltic pumice aggregate is used in the concrete mixtures in different amounts as aggregate. The slump, unit weight, water absorption, capillary water absorption, Upv, ffs, fsts and fc values of the lightweight concretes are determined experimentally. In addition, after exposure to acid, sulfate and high temperature, the changes in the weights and fc values of the concretes are observed. Besides, the influence of high temperature on the microstructures and mineralogical compositions of the selected mortars and the concretes are examined

Mechanical and microstructural properties of waste andesite dust-based geopolymer mortars

Waste andesite dust (WAD) occurs during sawing and other stone dressing processes of andesite stone. The disposal of WAD may cause storage and environmental pollution problems. The use of WAD in geopolymer production may be a solution to these problems. The mechanical and microstructural properties of geopolymer mortars synthesized from WAD were investigated in this work. To investigate these properties, the geopolymer mortars were manufactured using WAD with different molarity variations of NaOH as alkali-activator. The produced fresh WAD-based geopolymer mortars were cured at 100 °C in three different periods (12, 24, and 48 hours). The results revealed that the ultrasonic pulse velocity (Upv), flexural strength (ffs), compressive strength (fcs) of WAD-based geopolymer mortars increased as increasing NaOH molarity until reaching an optimum concentration (12 M for this work). Curing periods also significantly affected the mechanical and microstructural properties of WAD-based geopolymer mortars. The results showed that the higher ffs and fcs values can be obtained with a longer curing periods. Moreover, considering overall performance analysis, geopolymer synthesis with WAD promises a solution for sustainable mortar production and waste elimination

Çelik Fiber İçeren Dayanımlı Beton Özellikleri Üzerine Metakaolin Ve Öğütülmüş Pomzanın Etkisi

Bu çalıGmada çelik fiber içeren yüksek dayanımlı beton özellikleri üzerine metakaolin, öğütülmüG pomza ve metakaolin ile birlikte kullanılan öğütülmüG pomzanın etkileri deneysel olarak araGtırılmıGtır. Deneysel çalıGmada, kontrol betonlarından hariç 6 farklı seride bu mineral katkılar kullanılarak 30 farklı karıGımda beton üretilmiGtir. Birinci seride, çimento yerine ağırlıkça metakaolin, ikinci seride çimento yerine ağırlıkça öğütülmüG pomza ve üçüncü seride çimento yerine ağırlıkça metakaolin ile birlikte öğütülmüG pomza yer değiGtirilerek 7 farklı kombinasyonda kullanılmıGtır. Diğer seriler ise ilk üç serideki karıGımlara çelik fiber eklenerek üretilmiGtir. Ayrıca tüm karıGımlarda bağlayıcı miktarı 500 kg/m³, su-bağlayıcı oranı 0.20 ve çökme değerleri 8??2 cm olarak belirlenmiGtir. KarıGımlarda, su miktarını azaltmak ve sabit bir çökme değerini belirlemek için yüksek oranda su azaltıcı özelliğe sahip süper akıGkanlaGtırıcı farklı oranlarda kullanılmıGtır. Taze beton özelliklerinden çökme ve taze birim ağırlık deneyleri yapılmıGtır. SertleGmiG beton özelliklerinden ise sertleGmiG birim ağırlık, ultrases geçiG hızı, basınç dayanımı, eğilme dayanımı ve yarmada çekme dayanımı değerleri deneysel olarak belirlenmiGtir. Kontrol betonları ile diğer serilerdeki betonlardan elde edilen deneysel sonuçlar karGılaGtırılmıGtır. Ayrıca, farklı serilerdeki betonlar da birbirleri ile karGılaGtırılmıG ve en uygun mineral katkı oranları belirlenmeye çalıGılmıGtır. KarGılaGtırmalarda metakaolin içeren betonların performansının diğerlerine göre daha yüksek olduğu gözlenmiGtir. Sonuç olarak, tüm serilerde yüksek dayanımlı beton elde edilebileceği gözlenmiGtirIn this study has been experimentally investigated the effects of metakaolin, ground pumice and metakaolin together with ground pumice on the properties of high performance concrete containing steel fiber. In the study, except for control concretes by using these mineral additions in six different series, 30 different mixtures were produced. In the first series, metakaolin was used to replace by weight of Portland cement, in the second series, ground pumice was used to replace by weight of Portland cement, and also in the third series, ground pumice was used in the seven different combinations to replace by weight of Portland cement together with metakaolin to replace by weight of Portland cement. The other series were produced by adding steel fiber to previous series. Also, in the all mixtures, a constant total binder content of 500 kg/m³, the water-binder ratios of 0.20 and slump values of 8?2 cm were designed. The superplasticizer, which has high ratio of water reducing effect, was used in different proportions to reduce the water proportion and determine the value of constant slump value in the mixtures. The slump and unit weight of fresh concrete properties were tested. The hardened unit weight, ultrasound pulse velocity, compressive strength, flexural strength and splitting tensile strength values of hardened concrete properties were also experimentally determined. The results of control concretes were compared with the results of other series. The results of concrete in the different series were also compared with the results of each other, and tried to determine optimum ratios of mineral additives. As a result, it is seen that high strength concrete can be obtained in all series

Properties of geopolymer mortars derived from ground calcined perlite and NaOH solution

This study presents the strength development and characterisation of geopolymer mortars containing finely ground calcined perlite (GCP) as a precursor which is activated with sodium hydroxide (NaOH) solution. For this purpose, mortar specimens were produced with CEN standard sand, GCP, water and NaOH. The specimens subjected to heat curing after 24 h from casting and kept at an ambient temperature until the day of testing. The unit weight, ultrasound pulse velocity, flexural and compressive strengths of the mortar specimens were obtained after dry curing. The experimental results revealed that the mechanical properties of the mortars improved as the curing period and heat-curing temperatures increase, as well as increasing the concentration of NaOH. In addition, the characteristics of the mortars were determined by SEM/EDS and XRD analyses. According to the experimental results, the compressive strength of 37 MPa were obtained, and it is concluded that GCP can be used in geopolymer mortars owing to its abundance and appropriate chemical composition

Strength development of ground perlite-based geopolymer mortars

Raw perlite is a volcanic alumino-silicate and is used as aggregate in the construction industry. The high silica and alumina contained in the raw perlite allows the production of geopolymer mortar with the help of alkaline solutions. In this study, different geopolymer mortars are obtained by mixing ground perlite (GP), sodium hydroxide (NaOH), water and CEN standard sand and the strength and microstructure of these mortars are investigated. Mortar specimens are placed in the oven 24 hours after casting and kept at different temperatures and times, then the specimens are cured under laboratory conditions until the day of strength tests. After curing, unit weight, ultrasound pulse velocity, flexural and compressive strengths are determined. Experimental results indicate that the mechanical properties of the mortars enhance with increasing oven-curing period and temperatures as well as increasing NaOH molarity. In addition, SEM/EDS and XRD analyses are performed on the mortar specimens and the results are interpreted