PURPOSE: A soil solidifier composition is provided to increase dynamic compacting and to improve the strength of a weak soil by generating ettringite with an excellent hydration property. CONSTITUTION: A soil solidifier composition using a waste fly ash comprises 40-65 weight% of a waste fly ash which is generated by a furnace desulfurization method; 20-30 weight% of a general Portland cement; 11-20 weight% of a calcined alunite with improved reactivity by calcinating the alunite; 3-7 weight% of an aluminum hydroxide; and 1-3 weight% of a lingo sulfate-based dispersant. The distribution of a particle with a particle diameter of 35 micron or less is 90% or more.
