Influence of adding supplementary cementitious materials on rheology properties of mortar with high paste/aggregate ratio
It mainly studies the effects of fly ash cenosphere,silica fume,nano silica,and traditional fly ash on the rheological and mechanical properties of high paste/aggregate ratio mortar.The results show that:(1)28 d compressive and flexural strength of mortar increases with the increase of the content of silica fume(to 7.5％).As silica fume continues to increase to 10％,strength does not increase but decreases.The fluidity,yield stress,and viscosity of mortar at low speed gradually decrease with the increase of the silica fume content.The high-speed viscosity first decreases slightly,while increases rapidly as silica fume reaches 10％.(2)For fly ash cenosphere(from 5％to 25％),28 d strength of mortar improves significantly,but the strength decreases gradually with the increase of fly ash cenosphere content.The yield stress and high-speed viscosity increase with the increase of fly ash cenosphere content.The fluidity and low-speed viscosity also increase significantly,but decrease with the increase of fly ash cenosphere content.In comparison,the improvement of mortar with fly ash is limited,and the fluidity increases with the increase of fly ash content.(3)With the additions of both silica fume(5％)and fly ash cenosphere(from 5％to 25％),the strength increase is not evident,and strength decreases with the increase of fly ash cenosphere content.Also,as fly ash cenosphere content increases,yield stress increases,and viscosity first increases and then decreases.(4)Adding nano silica(from 0.5 to 2.5％)significantly increases the viscosity and yield stress,and reduces the fluidity of mortar.When the content exceeds 1.5％,the strength decreases.Therefore,for the mortar with high paste/aggregate ratio,the content of silica fume and cenosphere should be controlled at a small content(5％)to obtain better comprehensive mechanical and theological properties.Nano silica can be used to control the theological properties of the slurry according to the demand,but its effect on the strength should be paid attention to.
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