دانلود رایگان مقاله لاتین ر ژئوپلیمریزاسیون از سایت الزویر
عنوان فارسی مقاله:
رفتار ژئوپلیمریزاسیون کسر غنی از آهن خوب خاکستر قهوه ای
عنوان انگلیسی مقاله:
Geo polymerization behavior of fine iron-rich fraction of brown fly ash
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Geopolymers are semi-crystalline aluminosilicate polymers synthesized by the reaction of a solid aluminosilicate powder with an alkaline solution [1–4]. From a terminology point of view, if geopolymer hardens at room temperature like Portland cement it is called “geopolymer cement”, whereas it is called “geopolymer binder” if it requires heat treatment for hardening [5]. Geopolymer binders are considered as potential alternative to Portland cement because of its binding properties resulting in high strength, low permeability, and excellent durability [6,7]. Moreover, its production is less energy-intensive with 80% less CO2 emission compared to Portland cement [8–10]. The utilization of fly ash for geopolymer synthesis have been one of the most explored research areas in the last decades. This is due to the huge availability of fly ash all over the world and the needs to extend its different uses for bulk volume utilization [11]. In the present work, a brown color fly ash was collected from a coal-based thermal power plant in Mundra, India. The brown color of this fly ash is due to the high percentage of iron content. Thus, at many places, it is not acceptable as pozzolanic material for Portland pozzolana cement as it gives brownish color to cement. We have observed that the concentrations of iron oxides are more in lower size fractions of brown fly ash. Thus, we have used the air classification to segregate coarser and finer fractions. The segregated coarser fraction was grey in color. Thus, a study on their use as pozzolanic material for cement has been carried out and communicated elsewhere [12]. The iron rich-fly ash (Fe2O3 or Fe3O4) is generally avoided because it is believed that it decreases the compressive strength of geopolymer cements/binders [13]. But for the mass production of fly-ash geopolymer binders, such limitation should overcome. Elsewhere, it was reported that by segregating finer portion fly ash, its reactivity toward geopolymerization was considerably enhanced [14,15]. This paper reports the study of the geopolymerization and strength behaviors of fine iron-rich fly ash-based geopolymers. The characterizations of fly ash were done using X-Ray Fluorescence (XRF), X-ray diffractometry (XRD) and Particle size distribution (PSD). The geopolymerization reaction in various NaOHconcentration and sodium silicate to sodium hydroxide (S/H) ratio was monitored using Isothermal calorimetry. The hardened geopolymer pastes resulting were characterized using Field emission gun-scanning electron microscopy coupled to Energy dispersive X-ray spectroscopy (FEG-SEM/EDS). This is done to address the role of iron in microstructural characteristics. The compressive strength of geopolymer mortars was also assessed to show its suitability as construction materials.
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کلمات کلیدی:
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