Abstract: Blast furnace slag modifying experiments using iron tailings were conducted to investigate the effect of acidity coefficient(M_k)on crystallization property， viscosity and surface tension of modified-blast-furnace-slag. The results indicated that crystallization temperature of modified slag significantly decreases with the increase of M_k and the slag system is still unordered glass phase with slag temperature decreasing to 1100℃ when M_k is above 1.4. The sensitivity of slag viscosity to temperature change gradually decreases， the temperature range corresponding to theoretically suitable fiber-formation-viscosity range of slag wool gradually increases， and the difference between minimum fiber-formation-temperature and crystallization temperature in suitable fiber-formation-viscosity range(Δt=(t_○w-t_○l))， which is only 101.7℃ when M_k is 1.2， gradually increase with the increase of M_k. The effect of M_k on surface tension of slag is small and the ratio of surface tension to viscosity， σ/η， symbolizing difficult degree of slag-forming， gradually decreases with the increase of M_k in suitable fiber-formation-temperature range.

Key words: blast furnace slag, slag wool, crystallization property, viscosity, surface tension