| Summary: | 博士 === 國立臺灣科技大學 === 營建工程系 === 98 === This study investigates the properties and applications of geopolymer made of the fly ash as the major source material of silica-alumina activated by the alkali solution of sodium hydroxide solution and sodium silicate solution (water glass). The experimental design method was used to evaluate the effects of various alkali solutions on the engineering properties of geopolymer. In addition, through curing at elevated temperature, the influences of curing temperature and duration on the properties of geopolymer were also studied. In terms of application, the feasibility of retrofitting deteriorated concrete structure and potential for the immobilization of toxic heavy metal ions using geopolymer, respectively, were also explored and served as the base for developing the green materials for the reduction of waste and environmental protection. The experiment results show that: (1) The ANOVA results from the Taguchi experimental design method indicate that the dosage of sodium silicate solution is the most significant factor to control the compressive strength and dynamic elastic modulus of geopolymer. The individual contributions on the compressive strengths and dynamic moduli of elasticity of fly ash-based geopolymer at various ages are 80.63 to 89.52% and 62.26 to 72.71%, respectively. In comparison, the influence of dosage of sodium hydroxide solution is minor. (2) An adequate dosage of sodium silicate solution must be always kept, otherwise, the excessive additions of sodium silicate solution will increase the ratio H2O/Na2O such that the reduction of compressive strength and dynamic elastic modulus of geopolymer will occur. (3) The increase of curing temperature effectively improves various properties of geopolymer where the effect of 90 oC is better than that of 60 oC. In addition, the longer the curing time, the better the enhancement of geopolymer properties. However, the curing time of 12 hours is the most cost-effective. (4) The cylindrical concrete specimen retrofitted by the geopolymer mortar with steel fiber will defer the propagating speed of cracking during loading test to provide a longer pre-warning time. (5) The effects of heavy metal ions on the compressive strength of geopolymer were very complex. A negative effect on the compressive strength at age of 56 days was found. But the efficiency immobilization of heavy metal ions increases with age and complied with the provisions of the EPA standards for toxic dissolution.
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