Comparison Of Concrete Durability As Produced By Various Cements Manufactured In Ethiopia

This research is intended to furnish comparative analysis on the effects of the differentrntypes of cements produced in Ethiopia on the durability characteristics of concrete preparedrnfrom the same. Several laboratory tests are conducted on concrete samples prepared fromrnthe various cements available in the country from different sources by keeping all the otherrningredients the same. The methods of specimen preparation like mixing time andrncompaction effort and the subsequent curing condition are also kept identical for therndifferent specimens. Therefore, in essence the study attempts to relate any variation in therndurability characteristics of the samples to be obtained after testing only to the type ofrncement originally used in their preparation.rnCritical review of related researches undertaken in the area reveals that under the samernexternal environmental conditions, durability characteristics of concrete are affected by itsrnmicrostructure. Concrete microstructure, which is its fundamental internal structure, in turnrnaffects the transport phenomena taking place inside it. Hence, quantitative analysis of thernvarious transport mechanisms in concrete is a direct lead to its ability to resist deteriorationrnover time, which is its durability. Consequently, considering the capability of the laboratoryrnand the available funding, three of the major transport mechanisms were selected andrntesting was conducted on concrete samples prepared from five cements obtained from threerndifferent sources to assess their level of variability. The results are then correlated with thernpossible influence of the different cements on the internal structure of the concrete samplesrnand comparative analysis is carried out.rnIn addition, to illustrate the effects of varying cement content on each concrete sample, tworntypes of mixes were prepared from each cement type, for normal and intermediate ranges ofrncompressive strength, and the tests were also conducted twice at two different ages of thernconcrete specimens, 60 and 90 days. Besides, compressive strength measurements wererntaken alongside the durability tests at the ages of 56 and 91 days, in addition to, of course,rnthe standard 28 days compressive strength test.rnThe results indicate that in some cases, there is a significant variation in some of the mostrncritical factors which affect durability within samples prepared from the different cementsrnfrom which reasonable proximity is expected. While anticipating exactly identical results isrnnot rational, it's alarming to find variation of magnitude as high as 100% which reflects thernneed for more stringent quality checking and rigorous product standardization at thernnational level. It’s also imperative to seek ways of improving performance of such cements.rnKey words: Hydration, Permeability, Diffusion, Sorption, Porosity, Resistivity

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