6. Result And DiscussionConcrete test cubes were tested for water permeability with the test system prior to the determination of compressive strength at 28-days and 1-year. Investigation has been made on the effect of TIA on the properties of concrete. The influence of TIA containing some 60 % silica on the water permeability and compressive strength of grade 25 and grade 80 concrete have been discussed. The TIA concrete specimens generally showed reduced water permeability compared to the control. Test results was presented in the form of a mix design nomograph [15].
The appropriate use of TIA tends to enhance strength development and reduce water permeability of concrete if the cement replacement level is not more than 10 %. Water permeability of around 1 x 10 -13 m/s can be achieved for grade 80 concrete containing 5 % TIA. Concrete of reduced water permeability are suitable for products and structures subjected to constant water pressure such as the precast concrete piles and other concrete substructures.
