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- MakaleYalnız künye2023Scopus SJRQ2Engineering Properties of Geopolymer Mortars Containing Industrial Steel Shavings
Gülmez, Nihan; Koçkal, Niyazi Uğur
The purpose of using waste materials is to prevent the unnecessary use of resources and to reduce the amount of waste. Geopolymer, developed as an alternative to cementitious materials, prevents the depletion of natural resources and saves a large amount of energy. This paper presents the effect of waste steel shavings on the improvement of physical and mechanical properties of geopolymer mortars. For this purpose, geopolymer mortars were produced by using two binder types [slag (BFSb) and silica fume] as well as steel shavings in five different replacement percentages (0%, 2.5%, 5%, 7.5% and 10%) by volume instead of aggregate. A series of experiments on geopolymer mortars were carried out to determine properties such as bulk density, water absorption, apparent porosity, sorptivity coefficient, splitting tensile strength, flexural strength and compressive strength. Results showed that steel shavings recovered from metal processing and forming sector were highly effective at improving engineering properties of geopolymer mortars. Furthermore, although replacement of 20% by volume of BFSb with silica fume improved properties of geopolymer mortar, it was observed that the use of silica fume at higher ratios reduced mechanical properties by increasing porosity and sorptivity of BFSb-based geopolymer mortars.
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İncele - MakaleYalnız künye2023Scopus SJRQ2Computer-aided Optimization of Geopolymer Mortars
Gülmez, Nihan; Koçkal, Niyazi Uğur
The optimum mix design of geopolymers involves the purpose of determining which mixture will have high engineering properties without compromising the importance of each variable. This experimental study aimed to investigate the effects of some critical geopolymer mixture parameters on engineering properties by using historical data design in response surface methodology (RSM). Statistical models were developed between factors (binder and aggregate content, curing conditions and aggregate type) and their response surfaces (oven dry (OD) bulk density, water absorption, compressive strength and flexural strength). The final mathematical models for the response surfaces were constructed in terms of coded factors defined as dimensionless. In addition, a multipurpose optimization technique was used to achieve the desired design with the desired maximum strength.
- MakaleYalnız künye2022Scopus SJRQ2Corrosion potential and electromagnetic shielding effectiveness of geopolymer tiles produced with waste metal particles
Gülmez, Nihan; Koçkal, Niyazi Uğur; Özen, Şükrü; Ateş, Kayhan
This study is related to the production of special geopolymer specimens, where high effectiveness is provided in terms of electromagnetic interference (EMI) shielding and corrosion resistance. The study is important for the preparation of silica fume/slag based geopolymers by using waste steel and iron powder as a partial substitute for slag aggregate and thus to provide an effective solution to the disposal problems of waste metals. The electromagnetic interference shielding effectiveness (SE) of geopolymer tiles of 7.6 ± 0.1 mm thickness with different metal contents was measured at 4.9–7.05 GHz. Corrosion activity was monitored by measuring the half-cell potential of copper/copper sulphate (Cu/CuSO4) on specimens kept under controlled laboratory conditions for a period of 90 days at %60 relative humidity according to ASTM C876. In addition, anextensive evaluation of the optimization research on the design and proportion of mortar mixtures is presented here. EMI shielding effectiveness of slag based geopolymer tile with 10% steel particles has been determined as 26.1 dB in the frequency range 4.9–7.05 GHz. The results show that the shielding effectiveness reached a maximum of 23.1 decibels (dB) for geopolymer tiles in 40% iron powder content. Also, from experimental results, it was learned that geopolymer specimens with high slag content as binders in the mixtures showed better corrosion resistance.
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