Concrete
Durability

Uniformly dispersed, hollow-core polymeric microspheres can protect concrete from freezing-and-thawing damage. The article presents test data that show the effectiveness of a new method of delivering such microspheres into concrete.

The paper presents an analysis on the characteristics that enable particles, such as polymeric microspheres, that form annulus voids when concrete freezes to be used as an alternative technology to air entrainment for protection of concrete from freezing-and-thawing damage.

The use of a mineral-blended polymeric microsphere powder in concrete mixtures can provide protection from freezing-and-thawing (F-T) damage as well as lower the carbon footprint of concrete. The article presents results of compressive strength and cyclic F-T testing for microsphere and air-entrained concretes containing two levels of fly ash as a supplementary cementitious material.

Well-dispersed polymeric microspheres in a mineral powder medium can be used for protecting concrete from cyclic freezing-and-thawing damage. The article presents criteria for assessing the durability of microsphere concrete based on the parameters of the microsphere system in hardened concrete. The key equations for developing the durability criteria are also provided.

The air-void spacing parameters provided by various equations, when used as sole measures in predicting the frost resistance of concrete, do not seem to do any better than the standard spacing factor. Dispersion and spatial distribution have been shown to be effective ways of describing air-void or microsphere systems in hardened concrete as they have been quantified to establish criteria to assess the frost resistance of concrete. In the paper, dispersion and spatial distribution factors are elaborated upon to explain how they characterize zones that are protected by air voids or microspheres in the concrete.

Geometric probability concepts are used to establish a quantitative basis for predicting the magnitude of microscopically determined parameters of polymeric microsphere systems in hardened concretes relative to the actual magnitude of the parameters. The findings are relevant for air-entrained concrete as well when measurements obtained by microscopical examination of hardened concrete are compared with air content measured by the pressure method, or with air content and specific surface measured by the Air Void Analyzer (AVA).