Browsing by Author "Vapur, Huseyin"

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Production of precipitated calcium carbonate particles from gypsum waste using venturi tubes as a carbonation zone
(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 01.01.2019) Altiner, Mahmut; Top, Soner; Kaymakoglu, Burcin; Seckin, Ismail Yigit; Vapur, Huseyin; 0000-0002-7428-5999; 0000-0003-3486-4184; 0000-0003-4438-3982; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
In this study, we investigated the production of precipitated calcium carbonate (PCC) particles from desulfurization gypsum (DG) waste using a new experimental apparatus that is divided into two main parts: carbonation and stabilization zones. The solution was circulated via a pump from the stabilization zone to the carbonation zone where different types of Venturi tube were used for the reaction of CO2 with solution to produce PCC particles. The effects of CO2 flow rate, circulation rate, and Venturi types on the properties of the produced PCC particles were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analyses. The conductivity and pH values of the solution were monitored during the carbonation. In addition, the reactivity of selected PCC was determined to evaluate its use as a sorbent in a desulfurization unit. The experimental results indicate that the Venturi tube had a strong effect on the reaction time and properties of PCC particles. The use of a Venturi tube resulted in a decrease in the time required for producing PCC particles, which were smooth, well-crystallized, and nano-sized cubic crystals. However, when no Venturi tube was used, hollow spherical crystals formed along with cubic crystals. It was found that the reactivity of selected PCC particles produced using Venturi tube was rather higher (52x10(-4) min(-1)), indicating that the PCC can be used as a sorbent in the desulfurization unit.
Properties of fly ash-based lightweight geopolymer concrete prepared using pumice and expanded perlite as aggregates
(ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2020) Top, Soner; Vapur, Huseyin; Altiner, Mahmut; Kaya, Dogan; Ekicibil, Ahmet; 0000-0003-3486-4184; 0000-0002-6313-7501; 0000-0002-7428-5999; 0000-0003-4438-3982; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
The present paper aims to utilize the fly ash wastes with lightweight aggregates for geopolymer concrete production process in which sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) were used as alkali activators, respectively. The designed experiments were examined by the Yates Analyses and so the productions of geopolymer concrete were investigated depending on curing temperature, solid/liquid rate and concentration of alkali activators. The curing temperature and alkali activator concentration were revealed as effective parameters in geopolymerization. The effects of expanded perlite (EP) and acidic pumice (AP) aggregates were discovered for the production of lightweight geopolymer concretes. The microstructural properties of each produced geopolymer concrete were characterized using SEM, EDS and laser particle size analyses. The specifications of the concrete were evaluated based on their uniaxial compressive strength (UCS), point load strength (PLS), sonic speed (SS), Mohs hardness (MH), and water absorption (WAR) ratio results. In addition, the effects of pre-wetting of EP aggregates, which have hydrophilic nature, were examined. To the best of our knowledge, this is the first time that pre-wetted lightweight EP aggregates were used to produce lightweight GP concretes. As a result of pre-wetting, chemical usage decreased by 32.5%. The UCSs of the lightweight geopolymer concretes were in a range of 10-50MPa and their unit weights changed between 1250 and 1700 kg/m(3). Lighter concretes were obtained by the addition of EP aggregates rather than AP ones. (C) 2019 Elsevier B.V. All rights reserved.