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Durability performance of fibrous high-performance cementitious composites under sulfuric acid attack

Mermerdaş Kasım, Ipek Süleyman, Anwer Ahmed Motesem, Ekmen Şevin, Özen Mustafa

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 4

203--222

The high-strength concrete having a better compressive strength demeanor can be manufactured by the addition of the fibers which eliminates the inherent weakness, the brittle failure due to lack of tensile strength. In this study, an experimental study covering the enhancement of the mechanical characteristics and the investigation of the performance against the aggressive acid attack of high-performance cementitious composites (HPCC). For this, steel and glass types of fiber were employed in the manufacturing of HPCC, as either single or hybrid at various levels. The HPCC mixtures were designed at a constant water-to-cementitious ratio of 0.25. Portland cement and microsilica were employed in the manufacturing as cementitious material whereas the aggregate was the mix of river and quartz sands. 14 HPCC mixtures were designed and the flowability, unit weight, compressive and flexural strengths, sorptivity index, ultrasonic pulse velocity were tested at various ages. Besides, the loss in the strength, mass, and dimension of HPCC mixtures was also measured after exposure of the mixtures 1- and 2-month aggressive sulfuric acid (H2SO4). Additionally, the experimental results were statistically evaluated through general linear model ANOVA. Based on the results, the highest compressive strength values were observed in the HPCC mixture manufactured with steel fiber. The lowest losses in both flexural and compressive strengths were observed in the mixtures produced with microsilica. Steel fiber addition increased the compressive strength not only after applying the normal curing regime but also after exposing the sulfuric acid. Both flexural and compressive strength of HPCC mixtures were influenced by fiber type and volume fraction. The addition of glass fiber decreased compressive strength.

Nonlinear finite element analysis of double skin composite columns subjected to axial loading

Ipek Süleyman, Güneyis Esra Mete

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 1

109--133

The study aimed to simulate the behavior of the concrete-filled double skin steel tubular (CFDST) composite columns having a circular hollow section using the finite element method (FEM). To indicate the accuracy and the reliability of the model, the proposed FEM model was verified by the experimental test results available in the literature. Moreover, the code-based formulas (ACI, AISC, and Eurocode 4) and some empirical models suggested by the previous researchers for predicting the axial capacity of CFDST columns were used in this study to compare their results with the proposed FEM model. Furthermore, to visualize the effectiveness of sectional properties and infilled concrete compressive strength on the ultimate axial strength of double skin composite columns, a parametric study was conducted. For this, 72 test specimens were modeled considering two outer and inner steel tube diameters, three outer and inner steel tube thicknesses, and two different concrete cylinder strengths. All results were statistically evaluated. It was observed that the proposed FEM model had a good prediction performance. As well, the FEM model results indicated that the sectional properties, in particular, the diameter of the outer steel tube and concrete compressive strength, had remarkable effects on the load-carrying capacity of CFDST columns.