Changes in Pore Structure and Enhanced Durability of Concrete by the Use of Permeable Forms

Abstract

It is quite a while since permeable forms were developed and put to practical use, aiming at improving the durability of concrete by means of preventing airs and honeycombs from forming on these concrete surface. Permeable forms are designed to drain excess water contained in the concrete immediately after their placement. Removal of excess water not only decrease the water-cement ratio of the surface concrete, but increases the density of the concrete, and eventually enhances its durability.
However, few studies focus on the characteristics of pore structure, namely, the relationship between changes in the volume and distribution of capillary pore and the durability of concrete by the use of permeable forms. In this study, investigations were made paying attention to changes in pore structure on past data obtained from tests conducted on permeable forms. The data include pore size distribution, cement volume distribution, depth of accelerated neutralization, salt infiltration and surface strength. The investigations led to the following findings :
1) Use of permeable forms decrease the percentage of pore volume, especially that ranging between50 nm and 2μm.
2) In the case of pore size ranging between 50 nm and 2μm, correlations can be seen between the decrease in pore volume and such properties as neutralization, salt infiltration and surface strength.