Civil Engineering / İnşaat Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/13

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Author: search.filters.author.Erdem, Tahir KemalScopus Q: search.filters.scopusQuartile.Q2

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  • Article
    Citation - WoS: 55
    Citation - Scopus: 64
    High-Early Ductile Cementitious Composites With Characteristics of Low Early-Age Shrinkage for Repair of Infrastructures
    (Springer Verlag, 2015) Şahmaran, Mustafa; Al-Emam, Muhannad; Yıldırım, Gürkan; Şimşek, Yunus Emre; Erdem, Tahir Kemal; Lachemi, Mohamed
    Reduced performance in concrete infrastructures is mainly caused by the formation of cracks, which may arise due to deteriorating mechanisms during service life. In most cases, reduced performance calls for urgent repairs to the degraded section. Therefore, it is highly desirable to develop dimensionally stable, ductile repair materials that can attain adequately high strength in a limited amount of time, compensate for significant deformation due to mechanical and environmental loadings, and prevent early-age shrinkage cracks. In this paper, the performance of such a material (high-early-strength engineered cementitious composites, HES-ECC, with very low early-age shrinkage capacity) was investigated by studying mechanical properties and dimensional stability. Composites were produced with different water to cementitious materials and slag to Portland cement ratios. In order to enhance composite properties in terms of ductility and early-age shrinkage characteristics, saturated lightweight aggregates replaced sand in the mixtures. The experimental results show that the majority of HES-ECC mixtures developed in this study attained compressive strength values of more than 20.0 MPa and minimum flexural strength of 6.0 MPa within 6 h. Moreover, the HES-ECC mixtures exhibited strain-hardening behavior with strain capacities comparable to normal strength ECC, as well as substantially reduced autogenous shrinkage strain, both of which are unlikely to trigger the formation of cracks in tension at early ages. The integration of these conflicting parameters suggests that HES-ECC can easily meet the need for fast and durable repairs.
  • Article
    Citation - WoS: 54
    Citation - Scopus: 69
    Strength Prediction of High-Strength Concrete by Fuzzy Logic and Artificial Neural Networks
    (American Society of Civil Engineers (ASCE), 2014) Tayfur, Gökmen; Erdem, Tahir Kemal; Kırca, Önder
    High-strength concretes (HSC) were prepared with five different binder contents, each of which had several silica fume (SF) ratios (0-15%). The compressive strength was determined at 3, 7, and 28 days, resulting in a total of 60 sets of data. In a fuzzy logic (FL) algorithm, three input variables (SF content, binder content, and age) and the output variable (compressive strength) were fuzzified using triangular membership functions. A total of 24 fuzzy rules were inferred from 60% of the data. Moreover, the FL model was tested against an artificial neural networks (ANNs) model. The results show that FL can successfully be applied to predict the compressive strength of HSC. Three input variables were sufficient to obtain accurate results. The operators used in constructing the FL model were found to be appropriate for compressive strength prediction. The performance of FL was comparable to that of ANN. The extrapolation capability of FL and ANNs were found to be satisfactory.
  • Article
    Citation - WoS: 75
    Citation - Scopus: 87
    Use of Spent Foundry Sand and Fly Ash for the Development of Green Self-Consolidating Concrete
    (Springer Verlag, 2011) Şahmaran, Mustafa; Lachemi, Mohamed; Erdem, Tahir Kemal; Yücel, Hasan Erhan
    In the United States alone, the foundry industry discards up to 10 million tons of sand each year, offering up a plentiful potential resource to replace sand in concrete products. However, because the use of spent foundry sand (SFS) is currently very limited in the concrete industry, this study investigates whether SFS can successfully be used as a sand replacement material in cost-effective, green, self-consolidating concrete (SCC). In the study, SCC mixtures were developed to be even more inexpensive and environmentally friendly by incorporating Portland cement with fly ash (FA). Tests done on SCC mixtures to determine fresh properties (slump flow diameter, slump flow time, V-funnel flow time, yield stress, and relative viscosity), compressive strength, drying shrinkage and transport properties (rapid chloride permeability and volume of permeable pores) show that replacing up to 100% of sand with SFS and up to 70% Portland cement with FA enables the manufacture of green, lower cost SCC mixtures with proper fresh, mechanical and durability properties. The beneficial effects of FA compensate for some possible detrimental effects of SFS.