Abstract
ABSTRACT: The consortium of three durability index test methods consisting of oxygen permeability,
sorptivity and chloride conductivity were used to evaluate the potential influence of four (4)
common SANS 10197 cements on strength and durability of concrete. Twenty four (24)
concrete mixtures of water-cement ratios (w/c’s) = 0.4, 0.5, 0.65 were cast using the cement
types CEM I 42.5 N, CEM II/A-M (V-L) 42.5 N, CEM IV/B 32.5R and CEM II/A-V 52.5 N.
The concretes investigated fall in the range of the normal strength, medium strength and high
strength concretes. Samples were cast into cubes and panels for extraction of the test discs.
Other variables investigated were the effect of using filler sand in the mixtures and the
influence of compaction method.
It was found that the marked differences in oxygen permeability and sorptivity results
observed at normal and medium strengths tended to disappear at high concrete strengths.
Also, the influence of the different cement types on the durability properties diminishes at
high strengths with a slight bias towards better performance by low strength cement
containing higher proportion of extenders. The cements of low strength and/or that contained
no extenders (CEM 32.5 R, CEM I 42.5N) showed greater sensitivity to sorptivity relative to
other cement types, with water sorptivity values of the former increasing significantly with
increase in w/c of the mixtures. Results also show that while concrete resistance to chlorides
generally improves with increase in strength, the level of chloride resistance appears to reach
a limit beyond which no further improvement is achieved with high strengths. It appears that
incorporation of extenders is necessary for superior chloride resistance even with high
strengths.