硅灰系硅铁或硅铁合金在冶炼时的烟尘经冷却凝聚而成,其中SiO_2含量高达90％以上,比表面积可达200,000厘米~2/克,也称冷凝硅灰。这是一种新型的矿物质外加剂,因其对混凝土各项性能的增进作用优于其它火山灰,而受到广泛重视。当混凝土中掺入硅灰后,和易性显著下降, The fume of silico-ferrosilicon or ferrosilicon alloy during smelting is formed by cooling and condensing, in which the SiO 2 content is as high as 90% or more, and the specific surface area is up to 200,000 cm 2 /g, which is also called condensed silica fume. This is a new type of mineral admixture. Because it has better effect on the performance of concrete than other volcanic ash, it has received extensive attention. When concrete is mixed with silica fume, the workability is significantly reduced.