Yasutaka Sagawa

Optimization of Fly Ash-Based Geopolymer Using a Dynamic Approach of the Taguchi Method

A geopolymer is an inorganic polymer devised by Davidovits. In the field of construction materials, hardened bodies resulting from polymer reactions among metallic ions, such as Si4+ and Al3+, and alkaline solutions, such as sodium hydroxide solution and sodium silicate solution, have been studied. Geopolymers have several superior characteristics, such as high strength and high resistance to sulfuric acid. Thus, geopolymers can be applied to precast concrete products, such as sewage pipes. There are several kinds of design parameters to be considered when manufacturing geopolymers, which makes it difficult to establish a reasonable design for this material. The present study presents an optimization of fly ash-based geopolymers using a dynamic approach of the Taguchi method. As an input value, the volume ratio of the active filler and the alkaline solution is adopted. Coal fly ash and ground-granulated blast-furnace slag are used as active fillers. Six design parameters are taken into account. Type of fly ash and the institutes where the experiments were conducted are considered as noise conditions. As a result, the applicability of this method to the optimization of fly ash-based geopolymer is confirmed. The optimized geopolymer mortar was also found to have a stable long-term compressive strength and a superior resistance to sulfuric acid.