In this study, the effect of pH level of mixing water on physical, mechanical and microstructure properties of cementitious mixtures was examined. In order to adjust the pH level of mixing water, various ratios of NaOH were added to ultra-pure water. Therefore, in total, six different mixing waters were obtained including the reference mixing water, pH10, pH11, pH12, pH13 and pH14. Mortar samples were produced using the obtained mixing waters with CEM I 42.5R Portland cement, then physical and mechanical properties of the cement mortars were determined on the 7th, 14th, 28th and 90th days. In addition, microstructure properties of the cement mortar specimens were determined after the 28 days curing period. Porosity measurements by mercury intrusion porosimetry were also examined after the 28 days cure periods. At the end of study, it was determined that the alkaline mixing waters (up to pH13) have positive effects on the compressive strength and workability of the cement mortars. The best result was obtained with pH12 mixing waters.

Textile reinforced concrete (TRC) has gained attention from the construction industry due to its light weight, high tensile strength, design flexibility, corrosion resistance, and remarkably long service life. Some structural applications that utilize TRC components include precast panels, structural repair, waterproofing elements, and façades. TRC is produced by incorporating textile fabrics into thin cementitious concrete panels. Premature debonding between the textile fabric and concrete due to improper cementitious matrix impregnation of the fibers was identified as a failure-governing mechanism. To overcome this performance limitation, in this study, a novel type of TRC is proposed by replacing the cement binder with a polymer resin to produce textile reinforced polymer concrete (TRPC). The new TRPC is created using a fine-graded aggregate, methyl methacrylate polymer resin, and basalt fiber textile fabric. Four different specimen configurations were manufactured by embedding 0, 1, 2, and 3 textile layers in concrete. Flexural performance was analyzed and compared with reference TRC specimens with similar compressive strength and reinforcement configurations. Furthermore, the crack pattern intensity was determined using an image processing technique to quantify the ductility of TRPC compared with conventional TRC. The new TRPC improved the moment capacity compared with TRC by 51%, 58%, 59%, and 158%, the deflection at peak load by 858%, 857%, 3264%, and 3803%, and the toughness by 1909%, 3844%, 2781%, and 4355% for 0, 1, 2, and 3 textile layers, respectively. TRPC showed significantly improved flexural capacity, superior ductility, and substantial plasticity compared with TRC.

Pumice aggregates with low density and high porosity are widely used in lightweight concrete. The high water retention ability of pumice aggregates adversely affects the properties of fresh concrete. Additionally, pumice aggregates’ inadequate mechanical strength and durability hinder concrete performance. In recent years, research on coated aggregates has gained traction to improve the physical properties, mechanical strength, and durability characteristics of concrete. In this study, coarse pumice aggregates were coated with polyester and partially substituted with uncoated aggregates at ratios of 0%, 25%, 50%, 75%, and 100% in lightweight concrete formulations. Specific weight and water absorption tests were performed on the aggregates, while slump and unit weight tests were performed on fresh concrete mixtures. SEM-EDX analyses, unit weight, water absorbing capacity, sorptivity, compressive strength, freeze-thaw resistance, and sulfate resistance tests were performed on concrete specimens. The results indicated that the polyester coating significantly increased the specific weight of the aggregates and decreased the water absorption rates by up to 85%. Despite the coated aggregates resulting in decreased compressive strength of concrete specimens, they demonstrated reduced water absorbing capacity and sorptivity characteristics relative to reference concrete. Moreover, concrete made with coated aggregates exhibited better results in freeze-thaw and sulphate resistance tests.

Calcium aluminate cements (CACs) are a group of rapid-hardening hydraulic binders with a higher aluminum composition and lower ecological footprint compared to their ordinary Portland cement (CEM) counterparts. CACs are commonly known to have higher thermo-durability properties but have previously been observed to experience a major strength loss over time when exposed to thermal and humidity conditions due to the chemical conversion of their natural hydrated products. To address this, in this study, silica fume is added to induce a different hydration phase path suggested by previous studies and utilized in conjunction with fiber-reinforced lightweight pumice to produce lightweight concrete. To closely evaluate the performance of the produced samples with CAC compared to CEM, two different types of cement (CEM and CAC) with different proportions of pumice and crushed stone aggregate at temperatures between 200 and 1000 °C were tested. In this context, sieve analysis, bulk density, flowability, compressive and flexural strength, ultrasonic pulse velocity and weight loss of the different mixes were determined. The results of this study point to the better mechanical properties of CAC samples produced with pumice aggregates (compared to crushed stone) when samples are exposed to high temperatures. As a result, it is found that CACs perform better than CEM samples with lightweight pumice at elevated temperatures, showing the suitability of producing lightweight thermal-resistant CAC-based concretes.

Bu çalışmada doğalgaz depolama tanklarında kullanılması önerilebilecek bir betonun kriyojenik sıcaklık koşulları altında fiziksel ve mekanik özelliklerine düşük sıcaklıkların (-196 ° C) etkisi incelenmiştir. Bu amaçla üretilen numuneler 90 gün su küründe dayanım kazanmış ve sonrasında 20 dakika sıvı nitrojene maruz bırakılmıştır. Isı alış verişinin tamamlanması için kriyojenik kür tankında bir saat bekletilen numunelerin oda sıcaklığında 24 saat çözülmesi sağlanmıştır. Bir çevrim donma çözülme etkisinde kalan numuneler üzerinde, dinamik elastisite modulü ve ultrases geçiş hızı, basınç ve eğilme dayanımı deneyleri yapılmıştır. Sonuç olarak kendiliğinden yerleşen betonların bir çevrim kriyojenik sıvı etkisi ile dinamik elastisite modülü ve ultrases geçiş hızı değerlerinde referans numuneye göre sırasıyla %16 ve % 8,7 düşüş gözlenmiştir. Basınç ve eğilme dayanımı değerlerinde ise sırasıyla bir çevrim sonucunda % 10,11 ve %10,49 oranında artış görülmüştür. Anahtar kelimeler: Doğalgaz, Kendiliğinden yerleşen beton, Kriyojenik sıcaklık

Tahribatsız test metotları, yapıların yerinde (inşaat sahasında) ve taşıyıcı elemanlara hasar vermeksizin muayenesine olanak tanımaktadır. Betonun durabilite performansı ve dinamik yükler altındaki davranışı hakkında bilgi veren dinamik elastisite modülü değeri, tahribatsız yöntemler ile hızlı bir biçimde tespit edilebilmektedir. Beton üretimi esnasında sahada sıkça rastlanılan sorunlardan biri de soğuk derz olayıdır. Bu çalışmada, farklı döküm zamanları kullanılarak yapay olarak oluşturulmuş soğuk derze sahip numunelerin dinamik elastisite modüllerindeki değişim tahribatsız yöntemler kullanılarak ele alınmıştır. Bu kapsamda Referans (serbest döküm), 30o, 45o ve 90o derz yüzeyine sahip kiriş numuneler üzerinde farklı döküm sürelerinde (-30, 0, +30, +120, +240, +480, +1140. dakikalarda) numuneler üretilmiştir. Üretimi yapılan kiriş numuneler üzerinde 28 gün kür süresi ardından rezonans frekansı test metodu kullanılarak dinamik elastisite modülü değerleri hesaplanmıştır.