Optimum design of cement-based composite materials

Bu çalışmada, çelik tel narinliği ve içeriğinin eğilme halinde Çelik Tel Donatılı Betonun kırılma parametrelerine etkisi araştırılmakta ve bu parametreler optimize edilerek daha sünek ve daha düşük maliyetli beton elde edilmektedir. Optimum tasarım için, üç-düzeyli iki faktörlü tam deneysel tasarım, Tepki Yüzey Yöntemi ve çok amaçlı sayısal optimizasyon teknikleri kullanılmaktadır. Çelik telin narinliği ve içeriğinin özgül kırılma enerjisi ve karakteristik boya etkisinin belirgin olduğu sonucuna varılmaktadır. Daha sonra, agrega konsantrasyonunun betonun kırılma ve mekanik özeliklerine etkisi incelenmektedir. Kırılma enerjisinin belirlenmesi için RILEM TC 50-FMC standardına göre çentikli kirişler üzerinde üç noktalı eğilme deneyi yapılmıştır. Betonda agrega konsantrasyonunun artımı kırılma enerjisi ve karakteristik boy gibi kırılma özeliklerini belirgin biçimde iyileştirmektedir. Anahtar Kelimeler: Çelik tel, yarma-çekme dayanımı, eğilme dayanımı, agrega konsantrasyonu, kırılma enerjisi, karakteristik boy, tepki yüzey yöntemi, çok amaçlı optimizasyon.In this study, the main objective is to optimise the fracture parameters of Steel Fibre Reinforced Concretes for obtaining a more ductile behaviour than that of plain concrete. The effects of the aspect ratio and volume content of steel fibre on fracture properties of concrete in bending were investigated by measuring the specific fracture energy and characteristic length. For the optimum design, three-level full factorial experimental design, Response Surface Method and numerical optimisation techniques were used. The results show that the effects of fibre volume content and aspect ratio on specific fracture energy and characteristic length are significant. On the other hand, the effect of aggregate concentration on the fracture and mechanical behaviour of plain concrete under bending was investigated. For the determination of the fracture energy the three-point bending test was performed on notched beams according to the recommendation of the RILEM 50-FMC Technical Committee. Six control mixes ranging from hardened cement paste (hcp) to normal concrete were prepared in which the aggregate grading, water/cement ratio (w/c=0.316), and maximum aggregate size were kept constant, but the volume fraction of aggregate was changed as: 0.00 (hcp); 0.15; 0.30; 0.45; 0.60 and 0.68 m3/m3 (real concrete). Experimental results shows that modulus of elasticity, splitting tensile strength, net bending strength, fracture energy and characteristic length increases significantly with increasing aggregate concentration. Keywords: Steel fibre, splitting strength, bending strength, aggregate concentration, fracture energy, characteristic length, response surface method, multiobjective optimization

The determine of the performance classes of steel fiber reinforced concrete

Traditional concrete has weak characteristics regarding tensile strength and load bearing capacity following cracks. These weak characteristics of concrete cause sudden collapse on the concrete following rupture from dynamic effects such as impact, stroke and earthquake. The studies were performed to improve these characteristics by using different types of fibers in recent years. In these studies, performed in order to improve ductility and mechnical properties of concrete, it is observed that various types of steel fibers are used more than the other types of fibers. Tensile strength, aspect ratio and volume ratio of steel fiber have important effects on performance of Steel Fiber-Reinforced Concrete (SFRC). For the performance classes of SFRCs, their equivalent flexural tensile strength values were determined according to both Serviceability Limit State (SLS) and Ultimate Limit State (ULS). For this purpose, water-cement ratios of 0.55 were used in the production of concretes. For same water/cement ratio volume fractions of diffrent type steel fibers were varied from 0.26 to 0.64%. This study used three different steel fiber type (L/d=80, 65, 55). The complete load versus deflection curves were obtained for all unnotched beams of 150x150x750 mm. During the testing, the load and signals for deflections were recorded and stored by a computerized data acquisition system. Hence, five concrete batches were made for same water/cement ratio. In each series, the same aggregates (sand: 0 to 4 mm, limestone fines: 0 to 5 mm, crushed limestones: 4 to 11 mm and 8 to 22 mm) were used. Ordinary Portland cement (CEMI 42.5) contents in the mixtures with "water/cement" ratio of 0.55 were 350 kg/m3. The amount of water reducing admixture varied between 1.35% and 1.65% by weight of cement for different concrete mixtures to maintain approximately the nominal slump between 100 and 130 mm. In mixing, cement, sand, limestone fines, and crushed limestones were blended first in dry condition. Half of the water reducing admixture and of the water were mixed in a pan and added to the mixture. The remaining of the water reducing admixture and the water were added to the mixture gradually to provide homogeneity in the mixture. Steel fibers were scattered in the mixture and carefully mixed to achieve a uniform distribution. The specimens were cast in steel moulds and compacted on a vibration table. All the specimens were demoulded after about 24 hours, stored under wet burlap at 20oC until 28 days of age, then laboratory air-cured until testing days at 56 days. The dimensions of the beams, prepared for four point bending tests, were 150x150x750 mm. At least four beam specimens from each concrete mixture were used. For each mixture, three cylinders, 150 mm in diameter and 300 mm in height, were used for compressive strength and modulus of elasticity tests. Six disc specimens, 150 mm in diameter and 60 mm in height, were prepared for the splitting test. For a certain volume fraction of hooked end steel fibers, the fracture energy and the equivalent flexural tensile strengths for both SLS and ULS increase significantly. It is shown that the ability of the beam to absorb energy was substantial, even if the cut-off points were taken at the specified deflections for SLC and ULC. According to the experiment results, it is observed that steel fiber volume percentage and aspect ratio in each matrix strength do not affect compressive strength and elasticity module of steel fiber reinforced concrete. On the contrary, as steel fiber volume percentage and aspect ratio in each matrix strength increased, energy absorption capacity and equivalent flexural strength that are utilized in designs based on performance increased. It is examined that steel fiber aspect  ratio and toughness increment along with volume percentage increment are more effective in same fiber aspect ratio and volume rated steel fiber reinforced concretes with higher matrix strength.The necessity of high energy to separate the fiber-matrix bond while fibers are breaking off and getting scraped from matrix may interpret the increase in toughness. As for the enhancement in toughness by increasing steel fiber volume, it can be explained by the increment in fiber's crack bridging effect with the increase of steel fiber quantity in unit area. One of the reasons why semi-brittle concrete gains ductile behavior characteristic can be explained with steel fiber's load bearing from the splitting of matrix to the crack formation in fiber-matrix interface. Keywords: Steel fiber-reinfoced concrete, performance classes, equivalent flexural tensile strength, servicability limit state, ultimate limit state.Çelik Lif Donatılı Betonların (ÇLDB) performans sınıflarını belirlemek için performansa dayalı tasarım parametrelerinden olan eşdeğer eğilme-çekme dayanımı Kullanılabilirlik Sınır Durumu’na (KSD) ve Taşıma Gücü Sınır Durumu’na (TSD) göre belirlenmelidir. Bu amaçla yalın ve çelik lifli tüm karışımlarda su/çimento oranı 0.55 alınmış ve sabit tutulmuştur. Beton üretimlerinde 80, 65 ve 55 olmak üzere üç farklı narinlikteki (L/d) uçları kancalı çelik lifler, her bir narinlikte üç farklı hacim oranlarında kullanılmıştır. Karışımlarda çimento (CEM I 42.5 R) miktarı 350 kg/m3 olarak sabit tutulmuştur. Kimyasal katkı, belirli işlebilirlikte (çökme değeri=100-130 mm) karışımlar üretebilmek için çimento ağırlığının % 1.35-% 1.65 arasında değişen oranlarda kullanılmıştır. ÇLDB’ler üzerinde basınç, elastisite modülü, yarmada çekme ve kiriş eğilme deneyleri yapılmıştır. 150x150x750 mm boyutundaki çentiksiz kiriş numuneler üzerinde yapılan kiriş eğilme deneyleri sonucunda yük-sehim eğrileri elde edilmiştir. Yük-sehim eğrilerinin altında kalan alanlar esas alınarak Almanya Beton Birliği Yöntemi’ne (ABBY) göre eşdeğer eğilme dayanımları (KSD ve TSD) belirlenmiştir. Deneyler sonucunda, çelik lif hacim oranı artışının betonun basınç ve elastisite modülüne etkisi olmadığı görülmüştür. ÇLDB’nin yarma çekme ve eğilme dayanımının arttığı ve lif narinliği büyük olan betonlarda bu artışların daha fazla olduğu belirlenmiştir. Belirli bir çelik lif narinliği için çelik lif hacmi arttıkça, KSD ve TSD için eşdeğer eğilme çekme dayanımları belirgin bir biçimde artmıştır. Çelik lif donatılı betonların performans sınıflarının elde edilmesi yapısal tasarım ve uygulamalarda büyük yararlar sağlayacağı düşünülmektedir. Anahtar Kelimeler: Çelik lif donatılı beton, performans sınıfları, eşdeğer eğilme-çekme dayanımı, kullanılabilirlik sınır durumu, taşıma gücü sınır durumu

Autogenous deformation and fracture properties of cementitious materials: Effect of size and type of aggregates

Yüksek performanslı çimentolu malzemelerde erken yaşlarda oluşan otojen deformasyonu önlemek için önceden suya doyurulmuş hafif agregalar su rezervuarı olarak kullanılabilir. Sabit bir düşük su/çimento oranına sahip silis dumanı katkılı çimento hamurunun otojen deformasyonunu önlemek için, hacimce %30’u normal veya hafif agrega ile yer değiştirildi. Kullanılan agrega cins ve tane boyutunun oluşturulan kompozitlerin kırılma enerjisi, karakteristik boy ve kiriş açıklık ortası en son sehime olan etkileri incelendi. Sonuçlar, normal agregaların rijitliğinin çimento hamuruna göre yüksek olması sayesinde otojen deformasyonu bir miktar kısıtlarken, hafif agregaların çimento hamuruna su sürükleyerek otojen deformasyonu önlediğini gösterdi. Çimento hamuruna hafif agrega ilave edilmesiyle hidratasyon derecesi özellikle erken yaşlarda arttı. İnce hafif agrega ilavesiyle su rezervuarları hamur fazı içerisinde daha yakın dağılarak iyi bir içsel kürleme sağladı. Böylece, ince hafif agrega ile çimento hamurunun hidratasyon derecesi iri hafif agrega ilavesine göre daha yüksek bulunmuştur. Aynı zamanda içsel kürlemenin çimento hamurunun hidratasyon derecesini de artırdığı bulundu. Ayrıca, ince hafif agrega kullanımının iri hafif agregaya göre belirgin şekilde çimento hamurunun otojen deformasyonunu azalttığı belirlendi. İnce hafif agregalı kompozitlerin kırılma enerjisi, kirişin açıklık ortasındaki son sehim değeri, yarılmada çekme dayanımı ve basınç dayanımının iri hafif agregalı kompozitlere kıyasla daha yüksek olduğu görüldü. Normal agrega kullanımı ile kompozitlerin kırılma ve mekanik özelikleri artarken hafif agrega kullanımı ile azalmalar görüldü. Diğer yandan hafif agregalı kompozitlerin sünekliği çimento hamuruna göre daha yüksek bulundu.  Anahtar Kelimeler: Agrega tane boyutu, hafif agrega, içsel kür, kırılma enerjisi, otojen deformasyon, süneklik.  Since high strength/high performance concretes (HSC/HPCs) are produced using rich mixes with high cement contents and low water/cement ratios, they are denser and more homogeneous than normal strength concretes. Low porosity and non-connected capillary pore structures are the most important properties of these concretes. There is an insufficient amount of water in concrete to complete the hydration process, and also the water income is prevented because of the impermeable character of concrete. Concurrent with the production of hydrates, after de-moulding (also before) time dependent volume changes of cement paste occur. Development of the empty pores due to chemical shrinkage is the main reason for diminishing the radii of menisci. This decrease causes self-desiccation by increasing capillary stress in the pore water. The absorption of free water into pores by the hydrates and formation of fine pores is driven by the chemical shrinkage. At later ages, however, self desiccation becomes the major drive mechanism. The development of empty pores continues during self-desiccation and it affects the hydration kinetics. This effect limits the ultimate degree of hydration and consequently the strength of cement paste. Since the tensile strain capacity of concrete at early ages is not sufficient enough to resist stresses caused by the external and internal restraints, autogenous deformation leads to the formation of cracks. These early age cracks may induce durability problems. Conventional curing techniques are not effective in mitigating this decrease of relative humidity (RH) in the hardened cement paste.  Using pre-soaked fine lightweight aggregate (LWA) for preventing the decrease of RH in the hardened cement paste matrix was first recommended by Philleo (1991). It is known that the bond between lightweight aggregate and matrix is stronger than that of normal aggregate. This enhanced interfacial zone prevents the length changes developed under RH and/or thermal conditions. In application, concrete is usually designed on the basis of compressive strength theory, in which the brittleness of concrete is ignored. For this reason, fracture parameters of concrete have to be defined along with its brittleness. Because the LWAs produce more microcracks, the concrete containing these aggregates behaves more ductile (i.e., less brittle) than normal cementitious materials.  On the other hand, the use of LWA instead of dense aggregate is expected to result in a lower strength. It is obvious that the amount of LWA for internal curing must be optimized according to the mechanical and fracture properties of cementitious materials. This study presents the results of experimental studies conducted for determining the restraining effect of both LWAs and normal weight aggregates (NWAs) on autogenous deformation and fracture properties of composites containing 70% paste and 30% aggregate by volume. It has been shown that the size of NWAs has no significant effect on autogenous deformation at 28 days, while the autogenous deformation of cement paste with 0-2 mm size fraction of NWA has been found higher than that with 2-4 mm and 4-8 mm at the age of 360 days. At early ages, the finer NWAs (0-2 mm) restrained the autogenous deformation of cement paste, because the modulus of elasticity of cement paste was not too high. On the other hand, addition of coarser size NWAs easily restrained the shrinkage of cement paste at later ages. The fine size LWAs, as expected, has been found to be more effective in mitigating the autogenous deformation of cement paste than coarse LWAs. The addition of LWAs to paste phases increased the degree of hydration, especially at early ages. The use of fine LWAs causes the water reservoirs to be distributed in proximity and results in a better internal curing, hence the degree of hydration of cement paste with finer LWAs is greater compared to that with coarser LWAs. While the compressive strength of composites slightly increases with the increasing size of NWA, the size of LWAs has no significant effect on compressive strength. Also, the moduli of elasticity along with the bending and splitting tensile strengths were not affected significantly by the size of aggregates (both NWA and LWA). Addition of fine sand aggregate at the size fraction of 0-2 mm increased the characteristic length significantly compared to the cement paste. Although the fracture energies of cement pastes with LWAs were found smaller than that of reference cement paste the addition of LWAs caused an increase in the characteristic length of cement paste. Keywords: Autogenous deformation, fracture energy, internal curing, lightweight aggregate, particle size of aggregate, toughness.

Mechanical behavior of high performance cement-based composites

Yüksek ve ultra yüksek dayanımlı yalın betonlarda yutulan bağıl enerji düşük olduğundan bu malzemelere kısa kesilmiş çelik teller eklenerek sünek davranış elde edilmektedir. Böylece, son yıllarda basınç dayanımları 200 MPa’ı aşan yeni çimento esaslı sünek kompozitler geliştirildi. Bu malzemeler düşük geçirimlilik, geliştirilmiş dürabilite, sınırlı rötre ve korozyon dayanımının arttırılması gibi diğer yüksek performans özeliklerini de sağlar. Sunulan çalışma yüksek dayanımlı betonlar (YDB) ile homojen dağılı ultra incelikteki taneleri içeren yoğunlaştırılmış sistemleri (DSP), büyük kusurlarından arındırılmış (MDF) çimentoyu, geleneksel çelik tel donatılı betonları (ÇTDB), karma lif donatılı betonları, reaktif pudra betonları (RPC) gibi ultra yüksek dayanımlı çimento esaslı kompozitleri, yüksek oranda çelik tel içeren çimento bulamacı (SIFCON), kendiliğinden yerleşen betonu, sentetik lif donatılı betonları, erken yaşlardaki rötresi düşük yüksek dayanımlı yarı hafif betonu ve yangına dayanıklı polipropilen lif donatılı yüksek dayanımlı betonu gözden geçirmektedir.  Anahtar Kelimeler: Çelik lif, kendiliğinden yerleşen beton, polipropilen lif, reaktif pudra betonu, sifcon, yüksek dayanımlı beton.Since the relative absorbed energy during the fracture of concrete is low in both high strength and ultra high strength plain concretes, short cut steel fibers are added in these materials to obtain ductile behavior. In recent years, however, new cement-based materials have been developed which have compressive strengths over 200 MPa. These materials provide other high performance properties; such as low permeability, improved durability, limited shrinkage and increased corrosion resistance. This work reviews high strength concretes (HSCs) and some new cement based materials such as the Densified Systems containing homogeneously arranged ultra-fine Particles (DSP), Macro-Defect-Free (MDF) cement, conventional Steel Fiber Reinforced Conretes (SFRCs), concretes with hybrid fibers, ultra high strength cement-based composites such as Reactive Powder Conretes (RPCs), Slurry Infiltrated Fibered Concrete (SIFCON), Self Compacting Concrete (SCC), Synthetic Fiber Reinforced Concretes (SFRCs), Semi-Lightweight Concretes (SLWCs) with low shrinkage at early ages, and high strength polypropylene fiber reinforced concrete against fire. Keywords: High strength concrete, polypropylene fiber, reactive powder concrete, self-compacting concrete, sifcon, steel fiber

Application of fracture mechanics models to notched concrete disc specimens

Betonun gevrekliğini ve kırılma parametrelerini belirleyebilmek için günümüze dek kırılma mekaniğine dayanan çeşitli modeller önerildi. Bunlardan bazıları kırılma parametrelerinin belirlenmesi için sadece tepe yükünün ölçümüne dayanmaktadır. Sunulan bu  çalışmanın amacı, mod I (açılma modu) yüklemesi altında, farklı boyutlardaki beton disk numuneler üzerinde, boyut etkisini incelemektir. Bunun için aynı karışıma sahip beton numuneler kullanıldı. Numune boyutu arttıkça, hem çentikli hem de çentiksiz numunelerde nominal dayanım azalmaktadır, bu azalma çentiksiz numunelerde daha belirgindir. Deney sonuçları “Boyut Etkisi Kuralı”nı desteklemektedir. Elde edilen deneysel sonuçlar fraktal esasa dayanan iki modelle de karşılaştırıldı. Çoklu Fraktal Boyut Etkisi Yönteminin diğer yöntemlere göre daha yüksek korelasyon katsayısına sahip olduğu görüldü.  Anahtar Kelimeler: Beton disk numune, boyut etkisi, kırılma parametreleri, yarma-çekme dayanımı.Fracture of quasi-brittle materials such as concrete exhibits complex size effect. In recent years, several specimen geometries were used to study the strength dependence on size. So far, there is no acceptable test technique to determine the fracture parameters of concrete. On the other hand, there is little information about the fracture studies on the notched concrete disc specimens. Some fracture mechanics based models have been proposed for the determination of the fracture parameters and brittleness of concrete. Various test methods based on  peak load measurements were proposed to determine these parameters. The main objective of this work, however, is to study the size effect in concrete disc specimens with different sizes in mode I loading condition. All the specimens were cast from the same batch of concrete. As the dimensions of the specimens increase, the nominal strength decreases for both notched and un-notched specimens; the decrease was more noticeable in un-notched specimens. The test results obtained on the notched and un-notched specimens confirm the existence of the ?Size Effect Law?. The results were also compared with the approaches of two types of fractal based models. The correlation coefficient in Multi Fractal Scaling Law was greater than those of the others. Keywords: Concrete disc specimen, size effect, fracture parameters, splitting tensile strength

Effect of pozzolanic materials on the mechanical properties and chloride diffusivity of concrete

Yapılan deneysel çalışmada iki farklı seri beton üretildi. İlk seri betonlarda; portland çimentosu ince öğütülmüş F tipi uçucu kül ile yerdeğiştirildi, ikinci seri betonlarda ise çimentonun yerdeğiştirilmesi ince öğütülmüş yüksek fırın cürufu ile yapıldı. Çalışmanın ilk bölümünde ince öğütülmüş (Blaine özgül yüzeyi 604 m2/kg) uçucu kül miktarının betonun basınç dayanımına ve hızlı klor geçirimliliğine etkisi incelendi. Sabit 0.35 su/bağlayıcı oranında betonlar üretilerek her üretimdeki toplam bağlayıcı madde miktarı sabit tutuldu ve uçucu kül çimento ile %70’e kadar yerdeğiştirilerek kullanıldı. Uçucu külün çimentoyla yerdeğiştirilmesi bire bir ağırlık esasına göre ve %10’luk adımlarla yapıldı. Üretilen betonların çeşitli yaşlarındaki basınç dayanımları bulundu. Bu betonların üzerinde ayrıca ASTM C 1202 standardına göre hızlı klor geçirimlilik deneyleri de yapıldı. Çimentonun % 40 oranında ince uçucu külle yerdeğiştirilmesi durumunda beton basınç dayanımları yaklaşık aynı oldu. Betonda ince öğütülmüş uçucu kül kullanımı ile klor geçirimlilikleri önemli ölçüde azaldı. Çalışmanın ikinci bölümünde ise; aynı su/çimento oranına sahip betonlarda, çimento ince öğütülmüş yüksek fırın cürufu ile %40, %60 ve %80 oranlarında yerdeğiştirildi. Blaine özgül yüzeyi 5000 cm2/gr olan cürufun çimentoyla yerdeğiştirmesi yine bire bir ağırlık esasına göre yapıldı. Üretilen bu betonlarda ise klor iyonu yayınımı ve elektriksel özdirenç deneyleri yapıldı. Elde sonuçlar cüruf ilave edilmesinin betonların klor iyonu geçirimliliklerinin önemli oranda azalttığını ortaya koydu. Cüruf içeren betonların elektriksel özdirençleri de, sadece portland çimentosu ile üretilen betonlara göre büyük oranlarda arttı. Elektriksel özdirenç ölçümlerinin, yapı inşaa sürecinde, elde edilen beton klor geçirimliliklerinin izlenmesi ve kalite kontrolü için uygun bir yöntem olduğu sonucuna varıldı.  Anahtar Kelimeler: Puzolan, mekanik özelikler, dürabilite, klor yayınımı, elektriksel özdirenç.The primary objective of the present work is to study the effects of pozzolans on the mechanical and durability properties of concrete. Fly ash and granulated blast furnace slag were used in the study. In order to utilize the potential of these materials and obtain better concrete performance, pozzolans with smaller particle sizes were used, which were obtained by grinding. The experimental study consists of two parts. In the first part, effects of ground fly ash on the concrete properties were investigated. The effect of ground granulated blast-furnace slag on the chloride diffusivity of concrete was the main focus of the second part of the study. In the first part, a coarse F type fly ash was ground to a Blaine surface area of 604 m2/kg. The test results show that the physical properties such as density and fineness changed. The physical changes due to grinding are: i) the fineness of fly ash increases, ii) there is a remarkable increase in density by reducing the porosity of the fly ash particles, iii) the spherical fly ash particles transform into the mostly irregular shapes; some small fly ash particles keep their original shapes. For investigating the effects of ground fly ash, eight concrete mixtures were prepared using the same batch of ordinary portland cement (OPC) and ground low-lime fly ash. The aggregate grading used in the mixtures of concrete, water-binder ratio, and the maximum particle size of aggregate were kept constant in all concretes, but the partial replacement of cement by fly ash was varied from 0 % (OPC concrete) to 70 %, in steps of 10 %. The replacement was on one to one weight basis. Compressive strengths of the concretes were obtained for different ages. Rapid chloride permeability test was also carried out on the 1 year old specimens. At 28 days, there was little reduction in compressive strength up to 40 % cement replacement by ground fly ash; then significant decrease was recorded for the further fly ash dosages. At 56 and 120 days, however, the compressive strength up to 40 % cement replacement by fly ash was almost identical to that of the no fly ash concrete and for one year it was even higher. Beyond 40 % replacement, the compressive strength decreased significantly for the age of 1 year. The results of the rapid chloride penetration tests indicated that high volume ground fly ash concrete had much better resistance to the penetration of chloride ions. The main objective of the second part of the experimental study was to investigate the effect of ground granulated blast-furnace slag on the chloride diffusivity of concrete. Concretes with constant water/binder ratio were produced, in which an ordinary portland cement was partially replaced by a ground granulated blast-furnace slag with the replacement ratios of 40%, 60% and 80%, respectively. The slag used had a high fineness with a Blaine specific surface of 5000 cm2/gr. Accelerated chloride diffusivity tests based on migration testing were carried out on the concretes. In parallel, testing of electrical resistivity was also conducted. The resistivity of the concretes were obtained by two different test methods; i) two electrode method, and ii) four electrode method. The concretes containing granulated blast - furnace slag showed a significantly better resistance against chloride penetration when compared to that of the pure portland cement. Results proved that slag replacement ratio is a major factor for reducing the chloride diffusivity and the diffusivity decreased with the increasing slag amount. Incorporation of slag had an important effect also on the electrical resistivity of concrete and the resistivity of the concretes containing slag were substantially higher than that of the portland cement concrete. This increase in resistivity became more distinct with the increase in replacement ratio. For a given type of concrete and test conditions, the test results confirmed that there is a linear relationship between chloride diffusivity and electrical resistivity. Hence, as soon as this relationship is established, the test results also confirmed that a monitoring of electrical resistivity may be a very appropriate way for monitoring the chloride diffusivity as part of a general quality control during the concrete construction.   Keywords: Pozzolan, mechanical properties, durability, chloride diffusivity, electrical resistivity

The relationship between inflammation markers, positron emission tomography/ /computed tomography parameters and disease prognosis in advanced non-small-cell lung cancer patients

Introduction. Inflammation is known to be related to the development, spread, prognosis, and treatment response in cancer patients. Our study aimed to evaluate the correlation between inflammation indices and positron emission tomography-computed tomography (PET/CT) parameters and investigate their relationship with progression-free survival (PFS) and overall survival (OS) in patients diagnosed with stage-IV non-small cell lung cancer (NSCLC).  Material and methods. Demographic, clinicopathological, laboratory, and PET/CT data of 179 patients diagnosed with stage-IV NSCLC who presented to the Oncology Department of Dicle University, Faculty of Medicine between 2010–2020 were retrieved from patient files and the hospital database system.  Results. The median age at diagnosis was 64 (27–87) years. All patients included in the study had NSCLC: 72.6% had adenocarcinoma, 21.2% had squamous cell carcinoma, and 6.1% had other histological types. Of the 78 patients who were subjected to molecular analysis, 26 (33.3%) were EGFR-mutation positive. During the 10-month median follow-up, median first-line PFS was 6 months (95% CI 5.00–6.99), and median OS was 10 months (95% CI 7.8–12.1). The multivariate analysis performed for first-line PFS determined hemoglobin (HR = 1.01; 95% CI 1.003–1.02; p = 0.005) and PET total lesion glycolysis (TLG) (HR = 1.002; 95% CI 1.001–1.003; p = 0.003) values as independent prognostic factors. The multivariate analysis for OS determined positive EGFR mutation status (HR = 0.385; 95% CI 0.213–0.696; p = 0,014) and performance status (HR = 1.88; 95% CI 1.092–3.238; p = 0,008) as independent prognostic factors.  Conclusions. Our study determined the hemoglobin level and PET TLG from PET/CT parameters to be independent prognostic factors for PFS, and performance status and EGFR mutation positivity to be independent prognostic factors for OS

Evaluation of the effects of dual antiplatelet therapy on guided bone regeneration in peri-ımplant bone defect

PMID: 36730057In this study, the authors aim to investigate the effect of dual antiplatelet agents on peri-implant-guided bone regeneraation by studying a sample of rats with titanium implants in their tibias. The rats were randomly divided into 5 groups: acetylsalicylic acid (ASA) (n=10), treated with 20 mg/kg of ASA; ASA+CLPD (Clopidogrel): (n=10), treated with 20 mg/kg of ASA and 30 mg/kg of clopidogrel; ASA+PRSG (Prasugrel): (n=10), treated with 20 mg/kg of ASA and 15 mg/kg of prasugrel; ASA+TCGR (Ticagrelor): (n=10), treated with 20 mg/kg of ASA and 300 mg/kg of ticagrelor; and a control group (n=10) received no further treatment after implant surgery. Bone defects created half of the implant length circumferencial after implant insertion and defects filled with bone grafts. After 8 weeks experimental period, the rats sacrified and implants with surrounding bone tissues were collected to histologic analysis; bone filling ratios of defects (%) and blood samples collected to biochemical analysis (urea, creatinine, aspartate aminotransferase, alanine aminotransferase, phosphorus, magnesium, alkaline phosphatase, calcium, and parathormone). A statistically significant difference was not detected between the groups for all parameters (P>0.05). When the percentage of new bone formation was examined, it was found that there was no statistically significant difference between the groups (P>0.05). Antiplatelet therapy may not adversely affect guided bone regeneration in peri-implant bone defects