Proceedings of the 7th International Symposium on East Asian Resources Recycling Technology November 10~14, 2003, Tainan, Taiwan
FIRE-RESISTANT GEOPOLYMER PRODUCED BY WASTE SERPENTINE CUTTING Ta-Wui Cheng Department of Materials & Mineral Resources Engineering National Taipei University of Technology
[email protected]
Abstract : There are more than half million tons of serpentine waste produced per year during mining operation in Taiwan. This study is to develop a process to manufacture fire-resistant geopolymer based on serpentine waste. The experiment results show that the waste serpentine-based geopolymer have very good physical/mechanical characteristics. For fire resistance tests, a 10 mm thick geopoly mer panel was exposed to a 1100℃ flame, with the measured back-side temperatures reaching less than 450℃ after 30 minutes. Th e products can be fabricated for construction purposes and have great application potential. Keyword: Serpentine, Geopolymer, Recycling, Fire-resistance
INTRUCTION The serpentine in Taiwan was formed from gabbro and olivine during metamorphism process. The major mineral is serpentine, and it has dark green appearance with hardness of 3 to 5.The production of serpentine in Taiwan can be divided into dimension stone, and crushed rock. Generally, almost all the dimension stone is exported for building decoration, and the crushed serpentine rock is supplied as flux for iron making. According to Ministry of Economic Affairs’ report [1], there are more than 0.54 million tons waste serpentine produced per year, due to the well-developed joints in the serpentine orebody and the requirements of the particle size (6 mm ~ 80 mm) of serpentine by iron making companies. Some of investigations on the utilization of serpentine have been carried out. Such as: fertilizer production [1], extraction of amorphous silicate and pure magnesium compounds [1-4], carbon dioxide sequestration [5-6], synthetic forsterite refractory materials [7]. However, due to serpentine being a raw substance for the manufacture of refractory materials, it could be directly used for fire -resistant material. Geopolymer, an inorganic polymer, firstly developed by Professor Joseph Davidovits in 1978 [8-9], have been gradually attracting world attention as potentially revolutionary materials. It is a class of three-dimensionally networked alumino-silicate materials, similar to natural zeolite minerals.
Geopolymeric materials possess great physical and mechanical properties, including fire and acid resistance. The aim of this research work is trying to produce a waste serpentine-based geopolymer for fire -resistance purposes that has the potential for reutilization serpentine waste in Taiwan.
EXPERIMENTAL METHODS Materials KOH (analytical grade) and sodium silicate solution (SiO2 :Na 2 O = 3.3, weight % Na 2 O = 6-7% and SiO2 = 23-25%) were obtained from L. K Chemical Co. Ltd., Taiwan. The waste serpentine samples for this study were collected from Wanjung (one of the serpentine mines) in Haulien, Taiwan. Table 1 shows the major chemical composition of the waste serpentine samples. Serpentine wastes (< 6 mm) were firstly ground to minus 74µm using a hammer mill. The particle size of the ground serpentine ranged from 0.8 to 104µm with D50 of 4.5µm. Kaolinite was obtained from the Standard Reagent Co. Ltd., USA. Metakaolinite was prepared by calcining the above kaolinite at 750℃ for 6 hours as described by Davidovits [10]. The particle size of the metakaolinite ranged from 2.7 to 19.9µm with D50 of 6.3µm. The Chemical compositions of the metakaolinite are also shown in Table 1.
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Table 1 Major chemical composition of metakaolinite and waste serpentine Chemical Waste Composition Serpentine Metakaolinite Wt.% SiO2 40.6 52.3 Al2 O3 4.0 42.8 Fe2 O3 6.9 1.0 CaO 3.8
