Investigation of Concrete Mixtures Incorporating Hollow Plastic Microspheres

About the report:

This study investigated the potential of hollow plastic microspheres, HPM, for providing non-air-entrained portland cement concrete resistance to damage from cycles of freezing and thawing. In the study, a mixture with an air-entraining agent (vinsol resin) was used as the control for comparison with three experimental mixtures one with HPM, one with super water reducers (SWR) and HPM, and one with fly ash and HPM. HPM mixtures at dosages of 1.5% or more by weight of cement exhibited satisfactory resistance to damage from cycles of freezing and thawing. Mixtures with SWR and HPM exhibited low durability factors and failed the acceptance criterion requiring a durability factor of 60 or more. Concretes with fly ash and HPM displayed durability factors comparable to those of mixtures with the same dosages of HPM. However, the weight losses of fly ash mixtures were higher than those of comparable mixtures. To determine the cause of low durability factors in mixtures with SWR and HPM, specimens were examined using an optical microscope and scanning electron microscope. It was found that the paste of the mixture without the SWR contained numerous well distributed HPM voids. The paste of mixtures with the SWR and the same dosage of HPM contained few HPM voids distributed throughout, but did have concentrations of HPM at the undersurface of the aggregates.

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