The use of ferro-silicate slag from ISF zinc production as a sand replacement in concrete

Technical studies have shown that ferro-silicate slag from the Imperial Smelting Furnace (ISF slag) production of zinc can be used as a replacement for sand in cementitious mixes. The ISF slag contains trace quantities of zinc and lead, which are known to cause retardation of concrete set. Testing of experimental concrete mixes proves this retardation affect, although the delay in set does not appear deleterious to the eventual concrete hydration. If a gelatinous layer containing lead and zinc ions is formed around the cement grains in the concrete mix, set begins when this layer is disrupted and then continues as it would as if no zinc or lead had been present. Leaching studies demonstrate that pulverized-fuel ash and ground granulated blastfurnace slag have the potential to reduce the leaching of lead and zinc ions from the ISF slag, even in highly alkaline solutions.