Abstract: To make full use of the prominent green feature of slag concrete and accelerate its practical application, we adopted silica fume as the strength adjustor to investigate its effect on the mechanical strength and durability of mortars with 80% slag. We also evaluated the ecological efficiency of slag mortars. Experimental results demonstrate that silica fume is such an effective material to mitigate the retarded setting of mortars with high amount of slag due to dilutive effect. When 10% silica fume was added, the setting time of slag mortar was close to that of the control group. Moreover, silica fume has exerted prominent effects on the mechanical strength and durability of mortars. With 5% silica fume added, both the 28-day compressive strength and the flexural strength of mortar were much higher than those of mortar without silica fume. Consequently, the durability of mortar was also greatly improved by incorporating slag and silica fume into mortars, i.e., the capillary water absorption and electric flux of mortar reduced 8.83%-26.81% and 5.28%-36.87%, respectively. In summary, through the combined use of slag and silica fume as the alternative to 80% cement to prepare mortars, we significantly ameliorated the performance of slag mortars as well as its ecological efficiency, hence providing theoretical basis for the application and development of concrete with high volume of slag.

Key words: slag mortar, silica fume, mechanical strength, durability, ecological efficiency