I have performed water absorption and water permeability test for fly ash based geopolymer concrete. I found that the trends of water absorption and water permeability were different. The water absorption tend to reduce, while the water permeability tend to increase. I presumed that this was caused by the surface permeability which was not done properly. Can anyone advise me with this condition?
Water absorption test is related to free water intake while the other is based on the exposed pressure head. Since addition of fly ash at early ages decreases strength, impressed water pressure head causes water to penetrate easier. The longer you cure the concrete the less water permeability you will observe.
Thank you Kasim, so is it possible that the water permeability of geopolymer concrete with time in this condition?
I agree with Kasim. Anyway, water absorption and water permeability are not related to each other. Hence, it is possible to get the converse results. Imagine that at the short early of permeability test, the specimen will absorb the water (especially in high density specimen). So, the result collected at early period will be not too accurate. To avoid the problem, you should collect the flow data for the whole period until the flow is stable. If you can separate the difference, you will no more confuse again.
Answer the above question. In my research found that water permeability depend on its compressive strength. Since the compressive strength depend on time then water permeability too. However, researcher always plot the relationship between compressive strength and water permeability since all know that compressive strength depend on time.
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