THE EFFECT OF FGD GYPSUM ADDITION IN THE MIXTURE OF SHOTCRETE USED BOTTOM ASH AS FINE AGGREGATE

Abstract

Shotcrete used for temporary or permanent protection of slope in Mae Moh mine that may
deteriorate when exposed to the weather change. In order to improve the efficiency and reduced cost of
shotcrete, by-product materials from Mae Moh power plant area good alternative to use in the mixture. This
study investigated the influence of flue gas desulphurization (FGD) gypsum on the properties of shotcrete
used bottom ash as fine aggregate. The mixture of shotcrete was a combination of Portland cement type 1 and
bottom ash in a ratio of 1:3. The addition of FGD gypsum in the mixture was 4%, 8% and 12% by weight of
cement. Water to cement ratio was 0.6. The results demonstrated the slump flow of shotcrete decreased
withFGD gypsum increment. However, the setting time of shotcrete was longer with FGD gypsum increment.
The addition of FGD gypsum in the mixture at 12% can be reduced the shrinkage approximately 100
microstrains. The addition of FGD gypsum at 4% in the mixture can be developed the compressive strength
approximately 8-20% of shotcrete without FGD gypsum. Moreover, the compressive strength and durability
of shotcrete mixed with FGD gypsum at 4% could be able to give the highest strength. Nevertheless, the
compressive strength and durability of shotcrete tend to decrease with FGD gypsum increment when the
mixture containing FGD gypsum exceeds 4%. In conclusion, the addition of FGD gypsum at 4% in the
mixture was the most efficient to develop the properties of shotcrete.