Materials engineer, Testing Engineers Inc., Oakland, Calif.
Professor of engineering science, University of California, Berkeley, Calif.
Durability of concrete is greatly influenced by the permeability of the cement paste which in turn is governed by the pore size distribution. Some mineral and chemical admixtures are known to enhance the durability of portland cement concrete. The objective of this work was to investigate how the pore size distribution and permeability of portland cement pastes are modified by the addition of pozzolanic admixtures, blast furnace slag, and chloride salts. The effectiveness of pozzolans in reducing the volume of large pores and permeability was found to depend on the reactivity of the pozzolan used. Large additions of granulated blast furnace slag increased the total pore volume, however the pore size distribution was shifted toward finer pores and therefore the permeability of the paste was reduced. Among the chloride admixtures, namely calcium, magnesium, and sodium chloride, magnesium chloride was most effective in reducing both the volume of large pores and permeability of the cement pastes.
Paper ID: CCA10203J