Browsing by Author "Dilbas, H."

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Application of Finite Element Method on Recycled Aggregate Concrete and Reinforced Recycled Aggregate Concrete: a Review
(Kare Publishing, 2021) Dilbas, H.
In recent years, concrete has become a widely used material for general purposes in the structural area due to its excellent performance and properties. Hence, an increasing number of concrete structures are built, and a huge amount of building stock has been occurred around the world. However, because of the many progress (i.e., natural disasters), some of the concrete structures are demolished and their status is changed into rubble, and hence this becomes an environmental problem threatening the nature. To struggle with the rubbles, – a brilliant idea – recycling concrete is appeared and to disposal the rubbles in concrete works become a subject in the authorities’ agenda. Also, according to the brilliant approach, the studies focus on some experiments and simulation works (i.e., finite element modeling) to analyze the use of rubbles as recycled aggregate (RA) in concrete, recycled aggregate concrete (RAC) and reinforced RAC (RRAC) properties. At this point when a deep look is concentrated on the papers on RAC and RRAC, the reviews generally include experimental works of the research but rarely or hardly ever consider the simulation stages of the researche. Hence, this paper is drawn as a state-of-the-art report on modeling works of RAC and RRAC. Also, this paper gives finite element model (FEM) details of the examined research to improve the future studies on RAC and RRAC with helpful comments and directions. © 2021, Kare Publishing. All rights reserved.
Experimental Investigation on Properties of Recycled Aggregate Concrete With Optimized Ball Milling Method
(Elsevier Sci Ltd, 2019) Dilbas, H.; Cakir, O.; Atis, C. D.
Numerous research studies were conducted to improve the weak properties of recycled aggregate as a construction material during the last two decades. Most of these studies mainly focused on minimizing the undesired characteristics of the recycled aggregate through various treatment techniques to strengthen the attached old mortar or remove it from the recycled aggregate. Mechanical Treatment Methods (MTMs) used to remove the attached mortar from the aggregates were evolved over the years. Among available methods of treatments in the literature, the number of studies investigated the MTMs with an optimization process is limited. In lack of proper optimization process with rubble quality identification, mechanical treatment methods may be ineffective to provide concretes with sufficient properties, and they may yield to extra energy consumption and carbon emission. In other words, the optimization of treatment methods and determination rubble quality are two essential steps for having satisfactory results on the recycled aggregate. In this study, an optimization process is applied using the Los Angles test machine through the conducted Ball Milling Method (BMM). During the BMM process, various combinations of rotation (R) (100-200-300-400-500) and the steel ball (S) (0-2-5-7-10-12) applied to the recycled aggregate. Analysis results demonstrated the effectiveness of reducing the 8.95% water absorption value of the untreated recycled aggregate to 0.84% after the optimization process of BMM. Then, seven concrete specimens including 0-20-40-60% recycled aggregate (RA) and improved recycled aggregate (RA-i) mixes produced in the framework of the experimental study. For comparison purposes, engineering properties of 28 days concrete are determined. The use of RA-i up to 60% in concrete has not influenced the physical and mechanical properties, distinctively. After the optimization process, the RA use in concrete increased up to 60% which is twofold of the optimum RA value in the literature. As a result, optimized BMM improved the mechanical and physical characteristics of RA and increased the use of RA ratio in concrete mixes without any trade-off. (C) 2019 Elsevier Ltd. All rights reserved.
An Investigation on Effect of Aggregate Distribution on Physical and Mechanical Properties of Recycled Aggregate Concrete (Rac)
(Kare Publishing, 2022) Dilbas, H.
The aim of this study was to optimize the aggregate gradation curve (AGC) for recycled aggregate concrete (RAC). Five different gradation curves such as three AGCs defined in TS802 (A16, B16, C16) and two proposed AGCs named G1 and G2 were employed. The concretes designed with AGCs consist of different mortar phases and included coarse aggregates such as coarse NA and coarse RA. Thus, three stages were considered and were progressed in the experimental program: the 1st stage included the evaluation of the properties of the mortars, and the effect of AGC on the mortar phase of the concrete was investigated. The mortars had the components of concrete such as cement, water, and fine aggregate (<4 mm) representing the mortar phase of concretes. The 2nd stage was the evaluation of the test results of the fresh and the hardened concretes and, in this stage, the effect of AGC on the properties of concrete was diagnosed. Also, an additional stage was the 3rd stage and was made on the experimental data to define the weights of the parameters of the concretes by using the Entropy Method and to select the best AGC with the help of a decision-support instrument, TOPSIS. Sepa-rately evaluation of the test results showed that C16 resulted in a durable RAC in terms of low water absorption capacity with high compressive strength. Besides, the results of the Entropy Method presented exciting findings, and the coarse aggregate ratio in the mix was found to be the most effective parameter among the investigated parameters. When all parameters were investigated together using the TOPSIS method, the best AGC was found as G2 for RAC, but A16 can be preferred instead of G2 according to the similar TOPSIS scores. In addition, this paper opens a path in the literature regarding the need for the development of AGC in RAC and further investigations should be made. © 2022, Kare Publishing. All rights reserved.
Pi Distribution Method for Numerical Fracture Analysis of Reinforced Concretes (RC) Based Recycled Aggregates
(Springer Nature, 2025) Charef, M.; Tani, N.K.; Dilbas, H.
A numerical investigation was carried out for both cases of cracked and uncracked reinforced (RC) and fibrous reinforced (FRC) /unfibrous concrete specimens incorporating recycled aggregate (RA), which were assessed to explore the failure properties of these materials, using the “Pi Distribution Method” (PDM). PDM is based on the non-random distribution of aggregates, which depends on the falling aggregate experiment. A finite element (FE) software (ABAQUS) is used to model the concrete specimens. The results demonstrate an improvement in the mechanical properties of concrete after adding RA. The incorporation of RA into the concrete results in an increase in elasticity and greater displacement at loading due to their important ductility, high porosity, and weak bond to the cement matrix. RA contributes to enhancing post-cracking behavior and stress redistribution. The elastic behavior of RA concrete shows a more horizontal load-displacement curve, indicating its deformability. Both concrete reinforcements, by bars and fibers, are analyzed in terms of Load-Displacement and load-CMOD (Crack Mouth Opening Displacement) for the notched specimen. The addition of steel fibers to RA contributes to the increase of the linear elastic stiffness before and at the maximal force of the specimens by acting as dispersed reinforcement. The efficiency of the proposed numerical FE mesoscopic model based on PDM is confirmed for all the study cases. This study opens new paths in the literature, explores many types of recycled aggregates and various fiber types, and considers other structural elements as beams, columns, and joints. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Rheology of Superabsorbent Polymer-Modified and Basalt Fiber-Reinforced Cement Paste With Silica Fume: Response Surface Methodology
(Kare Publishing, 2024) Dilbas, H.
A composite's rheology can be changed by adding superabsorbent polymer (SAP) and basalt fibers and using silica fume. This study aimed to investigate the effects of these components on the viscosity and shear stress parameters of the paste. The proportions of the components were varied, with SAP content ranging from 0.01% to 0.03%, basalt fiber from 0% to 0.50%, silica fume (micro silica) at 15%, and water content from 0.40 to 0.50. Response surface methodology was used to optimize the mixture proportions, and the rheological properties of the resulting pastes were characterized using a rheometer. Results showed that the addition of SAP and basalt fiber had a significant impact on the rheological properties of the paste, with increasing amounts of both resulting in increased viscosity and shear stress. Overall, this study highlights the potential of SAP and basalt fiber in advances of the rheology of cement paste and provides insight into the optimal proportions of these components for achieving desired rheological properties. The findings of this study could be useful in developing high-performance concrete with enhanced rheological properties, which could have a wide range of applications in the construction industry. In addition, 0.50% BF, 0.01% SAP, and 0.445 water-to-cement were found as optimum proportions regarding the rheology of the cement paste. © 2024, Kare Publishing. All rights reserved.