İnşaat Mühendisliği Makale Koleksiyonu

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Assessing spatiotemporal characteristics of meteorological droughts in the Marmara Basin using HadGEM2-ES global climate model data
(Springer, 2025) Duvan, Akın; Aktürk, Gaye; Yıldız, Osman
In this study, spatial and temporal characteristics of meteorological droughts in the Marmara Basin, which is located in the semi-arid climate region with the highest population density in Turkey, were determined using HadGEM2-ES global climate model data. Here, precipitation projection data using both RCP 4.5 and RCP 8.5 scenarios were employed. The Standardized Precipitation Index (SPI) was employed to calculate drought intensities, and areal distributions of drought were determined using the inverse distance weighting (IDW) interpolation method. Drought intensity-area-frequency (DIAF) curves for the basin were created by converting point drought intensity data into areal drought data. The DIAF curves provided analysis of the temporal and spatial characteristics of droughts in the basin and revealed that drought intensities are projected to be higher under the RCP 8.5 scenario.
Optimization and prediction of colored pervious concrete properties: Enhancing performance through augmented grey wolf optimizer and artificial neural networks
(Elsevier, 2025) Koç, Ahmet Tuğrul; Yıldızel, Sadık Alper
This research introduces an innovative method that integrates glass fiber reinforcement, pigment integration, and advanced artificial intelligence (AI) modeling to enhance the performance of colored pervious concrete. Glass fiber inclusion improved packing density and decreased porosity, with a reduction from 18.42 % to 11.24 %. The incorporation of pigment (up to 2.5 kg/m3) affected aesthetics while not significantly altering porosity, permeability, or mechanical properties. The addition of glass fibers significantly enhanced compressive and flexural strengths, achieving values of 24.08 MPa and 6.3 MPa, respectively, at a 1 % glass fiber content. Albedo results indicated that solar reflectance varies by color, with white concrete showing the highest reflectance values. The artificial neural network (ANN) and Grey Wolf Optimizer (GWO) models demonstrated high predictive accuracy for key properties, achieving R2 values greater than 0.9 for compressive strength (CS), flexural strength (FS), and Cantabro loss (CL). Data augmentation enhanced model reliability and optimization results. The research indicates that 1 % GF and 0 % pigment are optimal for achieving a balance between strength and durability, providing essential guidance for the high performance, aesthetically adaptable permeable concretes, especially for urban infrastructure applications where, effective stormwater management, reduced heat island effects, and improved durability are critical.
Enhancing the Thermal Properties of Foam Concrete with Pumice-Encapsulated soy wax Phase Change Material: a Novel Approach
(Landsberg, Germany : Ecomed, 2025) Yavuz, Ali; Özkılıç, Yasin Onuralp; Yıldızel, Sadık Alper
This study explored an innovative technique for improving the thermal characteristics of foam concrete by incorporating soy wax phase change material (PCM) encapsulated within pumice. The core of this research is the development of PCM-pumice aggregates through the macro encapsulation of soy wax. This process involves direct impregnation, where melted soy wax is uniformly distributed within the porous structure of lightweight pumice aggregates. The thermal properties of the resulting foam concrete, notably its thermal conductivity, were rigorously evaluated. This evaluation entailed measuring the conductivity using a heat flow meter and subjecting the concrete samples to controlled temperature cycles, with a focus on the 25 °C and 55 °C marks. These specific temperatures were chosen to assess the impact of the PCM phase change on the thermal behavior of the concrete. Key findings indicate that the incorporation of PCM-pumice aggregates markedly improves thermal conductivity and heat retention in the solid state while simultaneously reducing fluidity, density, and compressive strength as a result of increased cohesion and porosity. Thermal conductivity significantly increased by up to 37% in the solid state relative to the control mix, due to the phase change material occupying air gaps within the concrete. Conversely, the thermal conductivity decreased in the liquid state, utilizing the PCM's latent heat capacity to lower heat transfer rates.
Physio-mechanical, durability and microstructural properties of sustainable permeable concrete reinforced with basalt fiber: reuse and recycling of waste polypropylene
(Springer, 2024) Doğan, İbrahim; Yıldızel, Sadık Alper; Kaplan, Gökhan
This study investigated permeable concrete's physico-mechanical durability and microstructural properties using recycled polypropylene aggregate (RpA) and basalt fiber (BF). RpA was used as a replacement for coarse aggregates with weight ratios of 5%, 10%, 15% and 20%, and BF was added to the mixtures with volume ratios of 0.25%, 0.5%, 0.75% and 1%. The study evaluated the physical, mechanical, permeability and durability properties of permeable concrete mixtures. The addition of RpA and BF reduced the density and slump of the concrete. For example, when RpA content was 20% and BF content was 1%, the dry density of concrete decreased from 1780 to 1828 kg/m3. The slump value decreased from 38 to 14 mm. The permeability coefficient increased with increasing RpA and BF amounts. For example, when the RpA ratio was 20% and the BF ratio was 1%, the permeability coefficient increased from 0.42 to 0.98 cm/s. The compressive strength decreased as the substitution rates of RpA increased. For example, the 28-day compressive strength of the mixture containing 20% RpA and 1% BF decreased from 23.52 to 12.85 MPa (compared to the reference mixture). Flexural strength was only reduced with the addition of RpA, but it increased by 0.75% BF. For example, the 28-day flexural strength of the mixture containing 20% RpA decreased from 2.96 to 2.42 MPa, while this value increased to 4.05 MPa with the addition of 0.75% BF. Using RpA alone increased the mass loss, but adding BF decreased the mass loss. For example, while the mass loss of the mixture containing 20% RpA was 17.7% at the end of 400 cycles, this value decreased to 13.8% with the addition of 0.75% BF. These results show that permeable concrete produced using RpA and BF can be used as a sustainable and durable materials in urban infrastructure projects.
Design of large-scale real-size steel structures using various modified grasshopper optimization algorithms (April, 10.1007/s00521-022-07196-3, 2022)
(Springer London Ltd, 2022) Aydoğdu, İbrahim; Örmecioğlu, Tevfik Oğuz; Tunca, Osman; Çarbaş, Serdar
[Abstract Not Available]
Endüstriyel Hangar Tipi Çelik Yapıda Farklı Makas ve Çapraz Türlerinin Yapısal Sistem Üzerindeki Etkilerinin İncelenmesi
(2023) Dikiciaşık, Yağmur; Sen, İbrahim Tarık; Çarbaş, Serdar
Teknoloji geliştikçe ve dünya koşulları değiştikçe, yapısal alandaki ihtiyaçlar ve çözümler bilim alanındaki güncel yöntemlere göre değişmekte ve gelişmektedir. Alternatif yapı metotlarına kıyasla, çelik yapı sistemleri daha dayanıklıdır ve çeşitli geometrideki yapı ihtiyaçlarına güvenli çözümler sunabilmektedir. Bu çalışmada, endüstriyel hangar tipi çelik yapının, örgü düzeni ve stabilite durumları değiştirilerek yapısal analizler gerçekleştirilmiş ve elde edilen sonuçlar karşılaştırmalı olarak değerlendirilmiştir. Sabit bir lokasyon üzerinde aynı boyutlara sahip toplam 24 farklı endüstriyel hangar tipi çelik yapının, farklı 3 makas ve 6 çapraz sistemi için sabit ve hareketli yükler altında yapısal analizleri gerçekleştirilmiş, elde edilen sınır değerler uygulama şartnamelerine göre incelenmiştir. TS EN 1991-1-4 ve TS EN 1991-1-3 standartları, Türkiye Bina Deprem Yönetmeliği (TBDY) ve Çelik Yapıların Tasarım, Hesap ve Yapımına Dair Esaslar (ÇYTHYDE) yönetmeliği dikkate alınmıştır. Yapılara, sismik yükler zaman-tanım alanında mod birleştirme yöntemi kapsamında etkitilmiş ve 1992 yılında meydana gelen 6,8 Ms büyüklüğündeki Erzincan depreminden elde edilen sismik ivme kayıtları kullanılarak dinamik analizler yapılmıştır. Çelik elemanların tasarımında ÇYTHYDE'deki Yük ve Dayanım Katsayıları ile Tasarım (YDKT) hesap yöntemi kullanılmıştır. Yapılarda sadece kapasite tasarımı sınırlandırılarak her tip yapı elemanından en az birinin minimum %80 kapasitede çalışması sağlanıp diğer yapısal tepkiler elde edilmiştir. Yapısal analizlerden elde edilen taban kesme kuvveti, yapı ağırlığı, kolon üst nokta ötelenmesi, tepe noktası ötelenmesi ve maksimum deplasman sonuçları yapısal analiz programına göre karşılaştırmalı olarak değerlendirilmiştir. Sonuç olarak, dışmerkez çaprazlı yapıların yapısal ağırlık açısından, merkezi çaprazlı yapıların ise öteleme açısından daha avantajlı yapısal tepkiler verdiği gözlemlenmiştir.
Cost optimization of colored gypsum composites
(2019) Yıldızel, Sadık Alper; Kaplan, Gökhan
Lately, gypsum composites as decorative and construction elements have been widely used for many building types due to their certain architectonic styles. Decorative gypsum composites are not very durable and stable when compared to the other composites; therefore, they need to be rehabilitated in short periods. To meet the increasing demand in the sustainability of these types of the composite, many researches have been conducted for improving its properties with the minimum cost. The aim of this study was to obtain the optimum cost of the colored gypsum composites with the improved mechanical properties. Glass fiber reinforced, silica and expanded perlite reinforced gypsum composites were colored with the addition of brown, yellow, black and red pigments. The mechanical properties such as compressive strength and freeze thaw (F-T) resistance of the mixes were also examined. A cost optimization analyze were performed based on the experimental test results. Results revealed that the usage and the cost of the color pigment added gypsum composites could be primarily optimized.
Design cost minimization of a reinforced concrete column section using overnew swarm-based optimization algorithms
(Springer Science and Business Media Deutschland GmbH, 2024) Tunca, Osman; Çarbaş, Serdar
It is very tiresome for a practiser to detect the best feasible sizing design of structural members including reinforced concrete columns that is a highly nonlinear and complicated structural engineering optimization problem. This is due to such a design is practically conducted via conventional trial-and-error computing methods in which resistance to external loads, cost efficiency, and aesthetic factors, etc. have to be considered. This study focuses on minimizing the design cost of primarily proposed reinforced concrete column design problem via three overnew swarm-based optimizers such as Coati Optimization Algorithm, Fox Optimizer and Pelican Optimization Algorithm (POA) that are firstly utilized for this purpose. In this regard, the type of steel rebar distribution, the characteristic strength of the concrete, the height and width of the column section, and the number and diameter of the rebars are treated as discrete design variables of the newly proposed complex reinforced concrete column design cost optimization problem. In solution, the design requirements specified in practice code provisions should also be met. Here, Turkish Building Earthquake Code 2018 specifications are considered as practice structural design constraints. Consequently, the algorithmic performances of three overnew swarm-based metaheuristic optimization algorithms are compared and evaluated in detail. Amongst them, the POA shows most fruitful algorithmic design solution performance. © The Author(s) 2024.
Forecasting of Lake Level by Soft Computing Approaches
(Springer Science and Business Media Deutschland GmbH, 2024) Demir, Vahdettin; Tamer, Mehmet Ali; Çarbaş, Serdar
To ensure the sustainability and management of water resources, regularly monitoring the water levels in lakes, rivers, basins, dam reservoirs, etc. is a very important engineering task. Our freshwater resources are gradually decreasing due to the destruction of freshwater resources and climate change. For this reason, monitoring, modelling, and researching of freshwater resources, especially lakes, are increasingly important issue for nowadays. In this chapter, soft computing approaches are used to forecast of lake water levels at Beyşehir Lake, located in the central part of Turkey. To do this, three artificial neural network algorithms (Multilayer, Radial Basis and Generalized Regression), two heuristic algorithms (Model 5-Tree and Multivariate Adaptive Regression Spline), and a Support Vector Machines containing three different functions (Radial, Polynomial, and Linear) are used. In addition to being models used successfully in hydrological modelling of civil engineering, the changes in modelling performance with the number of iterations, kernel functions, optimization algorithms, and data input sets that constitute the internal dynamite of the techniques are investigated. The attained results show that through these multiple parameters, radial basis artificial neural networks are the most successful when compared with mean absolute error, root mean square error, coefficient of determination, Taylor diagrams and Violin plots. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Optimization of waste tyre steel fiber and rubber added foam concretes using Taguchi method and artificial neural networks
(Elsevier Ltd., 2024) Yıldızel, Sadık Alper; Özkılıç, Yasin Onuralp; Yavuz, Ali
This research presents a study on the waste tyre steel (WTS) and rubber particles (RP) added foam concrete using Taguchi method and Artificial neural networks (ANN) by revealing its potential utilization in construction industry. The fresh and hardened characteristics of foam concretes were experimentally tested. Twenty-five different samples were first prepared according to the Taguchi design and compressive and flexural strengths, dry density and thermal conductivity of the samples were optimized. A Quasi-Newton based ANN algorithm was proposed to obtain prediction equations for the flexural and compressive strength of foam concretes. ANOVA analysis was also conducted to determine the most important factors. The results showed that the combined utilization of WTS and RP decreases the harmful effect of RP on the strength properties of foam concretes. Taguchi optimization results were confirmed through validation tests. With the proposed ANN method, R2 values were obtained as 0.9775 for compressive strength, 0.9723 for flexural strength, 0.9654 for dry density and 0.9527 for the thermal conductivity measurements. Both Taguchi and ANN system were found to be suitable for the design and estimation of the responses.
Addressing electric transit network design frequency setting problem with dynamic transit assignment
(Taylor and Francis Ltd., 2024) Aksoy, İlyas Cihan; Alver, Yalçın
Electric buses are projected to become the standard mode of transit systems in the foreseeable future for sustainable transportation. Realizing this transition necessitates a meticulously planned electricity infrastructure design which should be handled simultaneously with the traditional transit network planning to enhance the efficiency of electric transit networks. For this integrated problem referred to as the Electric Transit Network Design and Frequency Setting Problem, several studies have been conducted, with the absence of evaluating the energy state of each electric bus individually. The Multi-Objective Differential Evolution Algorithm (MODEA), developed to address the complex problem at hand, is tested on a hypothetical network by filling research gaps in previous studies. Energy states resulting from the individual evaluation of each bus in the best Pareto optimal solution considering dynamic aspects of the transit network are presented comprehensively. Furthermore, the impact of dynamic characteristics on the electric transit network design is demonstrated by comparing the findings obtained on the static network.
Optimum steel frame design through ultimate seismic energy dissipation of double diagonal friction dampers
(Elsevier B.V., 2024) Çarbaş, Serdar; Artar, Musa
In this paper, a creative design methodology is exhibited to attain seismic design optimization of steel frames that are equipped with double diagonal braces on which Pall friction dampers (PFDs) are mounted. The PFDs supply highest seismic energy dissipation to a structure for restricting destructive structural responds. Hence, the PFDs provide elastic movement to the steel frames to avoid the damaging consequence of an earthquake. To achieve this, the seismic energy dissipation over PFDs mounted on double diagonal brace members are tried to be maximized in this study. The Kobe earthquake record is used for conducting nonlinear dynamic time-history analyses to acquire structural responses of the steel frames. The Jaya algorithm (JA) that is a gradient- and parameter-free metaheuristic optimization technique is selected as an optimizer. The design algorithm encoded in MATLAB is integrated with SAP2000 structural analysis program through inbuilt open application programming interface (OAPI) functions to achieve simultaneous structural seismic responses. In proposed design methodology, firstly the optimal designs of steel frame structures without implementing double diagonal friction dampers are accomplished under effect of seismic loading exposed to structural design constraints of stress, displacement, drift, and geometric taken from AISC-ASD structural specifications. Then, the double diagonal friction dampers are implemented in the optimally sized frames to determine optimum yield strengths which are frictional slip loads. Hereby, the JA makes certain the dissipated seismic energy as maximum by checking the yield strength between the frame stories. In the end, it is verified that the PFD mounted double diagonal friction dampers provide maximum seismic energy dissipation throughout the steel frame structures for optimal sizing
Sustainable and cost-efficient design optimization of rectangular and circular-sectioned reinforced concrete columns considering slenderness and eccentricity
(Elsevier B.V., 2024) Tunca, Osman; Çarbaş, Serdar
In buildings, the transfer of external and internal loads starting from the roof and the top floor should gradually be carried towards the lower floors through column elements in a safe way and eventually transmitted to the foundation system of the building and then to the ground. Thus, the reinforced concrete columns are crucial structural elements that provide essential load transfer between stories of the buildings and resist horizontal loads such as earthquakes. The purpose of this study is to examine the effect of slenderness and eccentricity on achieving the most sustainable and most cost-effective design of rectangular and circular sectioned reinforced concrete columns. Slenderness is a crucial concept for bearing structural elements in pressure. Besides, the eccentricity is a frequently encountered term in practice. Unlike prior researches, this study takes the effect of slenderness, eccentricity, and cross-sectional geometry into account as well as the discrete design variables and codes of practice. The main goal of the optimization procedure is to generate a sustainable and cost-efficient reinforced concrete column design. The characteristic strength of the concrete, sizes of cross-sections, cross-sectional area of longitudinal and confinement rebars and their numbers are considered as discrete design variables in optimal design problem. The Turkish Requirements for Design and Construction of Reinforced Concrete Structures (TS500) and Turkish Building Earthquake Code (TBEC), which are complement each other, are used to determine realistic design constraints of design optimization problem. Thus, two different rectangular and circular sectioned reinforced concrete columns, which have three lengths, are sustainably and cost-efficiently optimized under three different load cases considering three various eccentricities via grey wolf optimizer. Finally, the attained 108 alternative optimum designs are evaluated in terms of sustainability (CO2 emissions) and cost-efficiency as separate objective functions. Consequently, the innovative attractive design solutions are accomplished such as external loads are less effect than height of the column on the optimal design of reinforced concrete columns.
Effect of geometry on flexural behavior of optimal designed web-expanded beams
(Elsevier Ltd., 2024) Taş, Serkan; Erdal, Ferhat; Tunca, Osman; Özçelik, Ramazan
Web-expanded steel beams (WESBs) are an excellent example of technological progress in the construction industry. The objective of this research is to compare the flexural strength of optimally designed geometrically diverse WESBs, including castellated, cellular, and angelina types. First, the minimum design weights of these three different WESB types are determined using nature-inspired harmony search (HSA) and particle swarm optimization techniques (PSO), according to the ANSI/AISC-360 and Eurocode practical design rules. Subsequently, a comprehensive experimental procedure was carried out to investigate the load-carrying capacity and failure modes of eighteen new generation simply supported WESBs, which were optimally designed. Scale models of the tested beams, originally made of steel sections with I-profiles, were subjected to various external loads in the reaction frame laboratory. The experimental results confirmed that angelina beams performed better than castellated and cellular beams under all loading conditions. Finally, a three-dimensional finite element analysis was performed for each specimen. These numerical verification analyses, performed using ANSYS Workbench, considered both geometric and material nonlinearities to validate realistic laboratory test results.
Mechanical, durability and solar reflectance properties of colored self? Compacting concrete
(2023) Yıldızel, Sadık Alper
Urbanized areas are known to have significantly higher temperatures than rural areas. The Urban Heat Island (UHI) effect is caused by surfaces such as asphalt, buildings, and other heat-absorbing surfaces that store more heat than natural vegetation. Sun-light reflecting properties of building materials are improved with different applica-tions. The present study investigates the mechanical, durability and solar reflectance properties of the colored self-compacting concrete. SCCs containing yellow, green, and black pigments were produced and evaluated. The fresh properties were determined with the slump, L-Box and V-funnel tests. Furthermore, compressive strength, solar reflectance and magnesium sulfate resistance tests were conducted. Yellow pigment added SCC showed a great potential (with the albedo of 0.42) in terms of solar reflec-tance and decreasing the contribution to the urban heat island effect.
Effect of the soil slope on the cost-efficient optimum discrete design of reinforced concrete isolated footings
(Elsevier Ltd., 2024) Tunca, Osman
The primary aim of this study was to investigate the impact of the soil slope on the cost-efficient optimum design of reinforced concrete isolated footings. In contrast to previous studies, the magnitude of the soil-bearing capacity was considered dynamically related to the foundation size and embedment depth. Thus, the principal objective of the optimization process was to attain an optimal reinforced concrete isolated footing design on sloped soil at the lowest possible cost. The length and width of the foundation, thickness of the footing, embedment depth, and diameter of the steel longitudinal rebars were considered as design variables. To achieve optimum designs, the principles of the Turkish Requirements for Design and Construction of Reinforced Concrete Structures (TS500 2000) and the Turkish Building Earthquake Code (TBEC 2018) were utilized to determine the practical structural design constraints of the optimization problem. The well-known Hansen and Vesic methods were used independently to compute soil load-bearing capacities. Thus, reinforced concrete isolated footings were cost-effectively optimized in four different load cases and four different soil slope cases, considering the Hansen and Vesic approaches as two different computation methods for the soil load-bearing capacity. As a robust and up-to-date algorithm, the grey wolf optimizer was utilized as an optimization tool. 32 optimum designs were then optimally evaluated with respect to cost efficiency, considering the soil slope, load case, and load-bearing capacity computation effects. As a result, increments in the soil slope were found to increase the cost of reinforced concrete isolated footings nonlinearly. The maximum cost differences between the 0° and 45° soil slopes evaluated in the design examples analyzed using the Hansen and Vesic soil load-bearing capacity methods were 116.36% and 148.05%, respectively. © 2023 Institution of Structural Engineers
Reimagining the future of transport and forever open road program
(Süleyman Demirel Üniversitesi İdari Ve Mali İşler Daire Başkanlığı, 2022) Armağan, Kemal
Transportation has a very wide effects either economic or social on human life. Millions of people are also working directly or indirectly for this industry. So, it is a mandatory for governments to evaluate their aspects on transportation construction, management, control and maintenance by increasing mobility. Also new technological developments and researches caused some changes in the expectations at many fields by new design and management approaches. The European Commission have supported some researches within Horizon 2020 program for new innovations to develop a highly efficient and effective cross modal transportation. In this paper recent developments at FOX (Forever Open Infrastructure Across all Transport Modes) program seeks to develop general methods for all transport modes and FOR (Forever Open Roads) program have reviewed. There are also benefits of FOR program that developed by Forum of European National Highway Research Laboratories (FEHRL) have mentioned and the outcome elements as automated, autonomous and resilient roads of the program have described.
The taguchi optimization of mechanical and durability properties of accelerator added concrete
(Gazi University, 2022) Çöğürcü, Mustafa Tolga; Uzun, Mehmet
It is very important to save time during the assembly of prefabricated elements. In wet connection types, the setting time of the concrete might lead time lose. There are many studies investigates the methods to shorten the setting time of concrete. Especially in the recent years, there are accelerators developed to shorten concrete setting time without causing corrosion. However, the negative effect of accelerators on fresh concrete properties such as workability makes them difficult to use. In this study, it is aimed to produce a concrete mixture with high initial strength and workability by using an accelerator. However, it is highly difficult to determine proper ratio of the accelerator for the mixture without precasting significant number of concrete samples which requires time, manpower and material consumption. Therefore, Taguchi optimization is very useful method in order to reduce this number of samples and effort. The optimum mixture has been achieved by performing the required tests applied to mixture designs obtained from Taguchi optimization.
Experimental investigation and analytical prediction of flexural behaviour of reinforced concrete beams with steel fibres extracted from waste tyres
(Elsevier Ltd., 2023) Yıldızel, Sadık Alper; Özkılıç, Yasin Onuralp; Bahrami, Alireza; Aksoylu, Ceyhun; Başaran, Boğaçhan; Hakamy, Ahmad; Arslan, Musa Hakan
In recent years, studies on the use of car tyre wastes in concrete have gained momentum. Especially, the effect of recycled waste steel wires (RWSWs) from tyres to be mixed into concrete for using in newly designed reinforced concrete buildings on the performance of construction elements is a fairly new research area. In this study, the bending behaviour of 12 reinforced concrete beams was investigated having 1/3 geometric scale, 100 × 150 × 1000 mm in size, and produced with RWSWs additive in different volumetric ratios (1%, 2%, and 3%) under vertical loads. Another main parameter selected in the study was the amount of varying tension reinforcements (2ϕ12, 2ϕ10, and 2ϕ8). The load-carrying, stiffness, ductility, and energy dissipation capacities of the RWSW reinforced bending beams were compared with the primary aim of this study which was to examine and present the contribution of RWSWs on the improvement of the bending performance of the reinforced concrete beams. The results revealed that the mechanical properties of the hybrid beams with RWSWs vary depending on dosages but are comparable with those of the beams-only with the same fibre dosage. A positive effect was obtained for the hybrid beams containing 2–3% RWSWs. Besides, RWSWs were found to be highly well mobilised at larger crack widths, and the post-cracking strength of RWSW mixes was significantly higher. Considering both mechanical properties of the beams and fresh properties such as the workability, 2% of RWSWs is recommended to be utilised in the reinforced concrete beams. On the other hand, the results were compared with the predictions of the methods given in the literature and standards. Moreover, an equation was derived to better predict the capacity of the hybrid beams using RWSWs.
Effects of mineral additive substitution on the fresh state and time-dependent hardened state properties of calcium alumina cement mortars
(Turkish Chamber Civil Engineers, Turkish Journal of Civil Engineering) Eren, Faruk; Keskinateş, Muhammer; Felekoğlu, Burak; Tosun Felekoğlu, Kamile
Calcium aluminate cements (CAC) are a candidate alternative binder to provide the requirements of a repair material such as accelerated hardening, good adhesion, compatibility with existing concrete, dimensional stability and corrosion resistance. The absence of water-soluble hydrated lime among the hydration products can also be accepted as an important advantage. However, the transformation reactions that may occur in the phase structure of the CAC depending on the ambient conditions over time may cause a loss of strength in the concrete produced with this cement. In this study, it is aimed to provide solutions to the problems arising from the conversion reactions in the hydration process of CAC, to improve the fresh state properties and to stabilize the strength development in the long term. Consequently, the effects of using CAC blended with different mineral additives (SiO2 and CaSO4) on the mortar consistency, setting time and rheological properties were investigated. In the hardened state, abrasion resistance and time-dependent compressive and flexural strength developments were determined. As a result of the experimental studies, it was concluded that the CAC mortars containing 16% SiO2 and 50% CaSO4 additives can provide improved properties in their fresh state, and they also demonstrate an improvement in strength after 400 days by obtaining stable products during the hydration process without any time-related strength loss.

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