Migration of Corrosive Substances in Concrete Caused by Casting Conditions

Abstract

This paper discloses 1) that expansive properties due to alkali-silica reaction, diffusion properties of oxygen and infiltration properties of chlorine differ for the direction of concrete placement and the direction perpendicular to it, 2) that when the placement height of a lift becomes great, these properties will differ markedly between upper and lower parts of the lift even when placement is in the same direction. It is also pointed out that the causes of these ununiformities are 1) that continuous capillaries in the vertical direction and voids at the undersides of aggregate particles are formed due to segregation accompanied by bleeding immediarely after placement and 2) that the constitution of the concrete has greater porosity at the upper part due to rising of segregated water the greater the height of placement.