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    Effect of nanosilica addition on the mechanical properties of cement mortars with basalt fibers with or without silica fume
    (Kare Publishing, 2022) Pehlivan, A.O.
    Fiber reinforced concrete is widely used throughout the world however to reveal its full po-tential, optimization with different additives should be asserted. In this study, effect of the three different parameters were diagnosed by means of compressive strength, flexural strength and fracture. Ordinary Portland cement mortars were studied with three different basalt fiber contents (0, 0.5, 1%), three different nanosilica addition (0, 1, 2% by wt. of cement) and also silica fume incorporation (0, 5% by wt. of cement). The results showed that adding basalt fiber significantly improved the flexural strength and toughness properties and also with the addition of nanosilica the increase in flexural strength boosted up to 23% level of increase at the presence of silica fume. This synergy effect was found to be significant when incorporating basalt fibers. When nonfibrous specimens were inspected, it is seen that addition of nanosilica was not significantly efficient increasing neither the flexural strength nor fracture properties. © 2022, Kare Publishing. All rights reserved.
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    An Experimental Investigation on Strength Behavior of Recycled Fine Aggregate (RCFA)-Treated Compacted Clayey Soils
    (Springer Science and Business Media Deutschland GmbH, 2023) Kishko, H.; Kutlu, Z.N.; Şenol, A.; Pehlivan, A.O.
    In geotechnical engineering applications, soils that exhibit plastic behavior over wide ranges of moisture content and liquid limits have the potential of low bearing capacity, settlement and potential of swelling/shrinking where they are generally considered to be as problematic soils. Although the compacted soils are commonly used in geotechnical engineering practice, compacted fine grained soils are not commonly preferred to be used for earthworks due to this plasticity in nature associated with complex hydro-mechanical behavior. Practicing engineers rely on using variety of design, construction and stabilization techniques to reduce these potential problems. In this aspect, promoting the use of recycled waste materials as improvement techniques and to make compacted fine grained soils usable by means of a stabilization becomes an important issue towards both for; proposing sustainable solutions and also sustainability for the construction of large infrastructures. Within scope of this study, shear strength properties for short term stability of compacted fine grained soils were tested to examine the convenience of adding—recycled concrete fine aggregates—for soil stabilization purpose to overcome these problems. The recycled concrete fine aggregates can be considered as a new material which were produced from crushing ready mix C16 concrete cast in 1250 × 2500 mm framework and after a curing period of 90 days. After crushing process, both coarse and fine aggregates were acquired. Since generally recycled coarse aggregates were used in structural concrete applications, only recycled fine aggregates were facilitated in soil stabilization. This paper gives a brief summary of the results of ongoing research on the shear strength behavior of non-treated and treated low plasticity clayey soil, emphasizing the effects of treatment parameters as: percent by weight of fine aggregate, and curing time. The results for the experimental analysis are reported showing the effect of fine aggregate addition on the strength behavior of compacted fine grained soil for relevant engineering applications. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2023.
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    Investigation of fracture parameters of concrete incorporating basalt fibers
    (Fundatia Serban Solacolu, 2021) Pehlivan, A.O.
    Concrete is a brittle material that should be enhanced with better tensile strength and toughness capacity. Concrete matrix is generally reinforced with fibers which are extremely helpful inhibiting the crack propagation and supplying the ability of strain accumulation into concrete matrix. In this study, an environment friendly type of fiber was introduced into concrete for the investigation of mechanical properties and fracture characteristics by size independent double-K fracture parameters asserted in the literature. Effect of basalt fibers with different lengths and contents were investigated under notched three-point bending tests and relevant parameters obtained and calculated, were compared for two distinct parameters: fiber length (6, 12, 24 mm) and content (0, 0.1%,0.3%, 0.5%, 1%). Shorter fibers confronted dispersion problems when used in higher content whereas 12 mm fiber specimens performed more stable results. Fracture energy dissipation was found to be linearly increasing with increasing fiber content and also longer fibers were found to be more efficient. Double-K fracture parameters were found to be resourceful when considering toughness and ductility of the material besides these parameters indicated useful information regarding the pre-cracking and post-cracking behavior of concrete. SEM investigations were also conducted to monitor the bonding between basalt fibers and concrete matrix. © 2021, Fundatia Serban Solacolu. All rights reserved.