However, since volume of permeable voids of modified samples
was lower than the plain cement paste at w/s = 0.27, it can be
assumed that incorporation of OC was able to generate an important
micro structural modification and thus contribute to formation
of closed porosity or reduction in the continuity of pores. On
the other hand, as it is shown in Fig. 4, volume of permeable voids
of modified samples greatly increased at higher w/s ratios that suggests
about formation of higher volume of capillary pores, what is
in agreement with observation made by others [14,15]. Since sorptivity
reflects the combined effects of composition, pore structure
and wettability [21], it was thought that water absorption has
increased probably due to complete wetting of pore surface which
suggests that pore blocking effect or an effective barrier against
water migration into the bulk was not formed by OC at higher
w/s ratios.