Microsilica in Sodium Silicate Bonded Sands

This paper investigates the microsilica addition value in the improvement of the sand molds and cores properties made with sodium silicate binders. There are experiments confirming the importance of the better sand mixtures mobility in the strengthening of these molds and cores. The paper explains the difference between microsilica and nanosilica in their interaction with alkaline silicate solutions and shows how the products of this interaction affect the properties of the sand mixtures. The results presented in the paper show the role of microsilica in curing sodium silicate bonded sands and demonstrate more possibilities to spread its positive complex effect on the sand molds and cores cured chemically, without heat. Conducted experiments with these sands proved the benefits of applying microsilica as a sand additive for increasing density and strength of the molds and cores, for easing their shakeout by lowering silicate level in the binder system. It is shown that the microsilica presence in the powder component allows using a hydrous sodium silicate powder also as a part of this component to replace a liquid sodium silicate in the two-component silicate binder system as well as creating pourable dry mixtures of silica sand and all solid additives of the binder system.