Study on the Uses of Derba Ordinary Portland and Portland Pozzolana Cements for Structural Concrete Production
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Date
2014-08
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Addis Ababa University
Abstract
By varying the relative proportions of the essential compounds and fineness to which the cement is ground and/or by incorporating pozzolanic materials, it is possible to produce different Portland cement types; and these proportions should be known by the customers. However, almost all the cement factories of Ethiopia are not willing to disclose their manuals and chemical composition of the cements. And even most of the consultants who design structures are simply specifying the ingredients of concrete without enough description of type, reasonable content, and relations with other factors which have direct effect to the hydrolysis reaction of the cements. These and others are costing the country negatively. Therefore this research focuses on the study of the uses of Debra ordinary Portland and Portland pozzolana cements for structural concrete production from the production process of the cements to the final results and their focus to the environment.
To achieve the final output of this research, the cement factory was visited and test results of Derba OPC and PPC were collected from the factory. Then the chemical and physical properties of these cements were analyzed and the cement production process of the factory is also illustrated. Furthermore, ten mix proportions for Normal, Intermediate and High Strength Concretes were conducted in laboratory. In each class of concrete, concreting was made keeping every condition the same except varying the cement amount per trial mixes of both the cements; hence, all attained concrete properties of each class are mainly attributable to the cement’s properties; as all things including material properties and gradations are carefully done.
The analyzed cement test results together with literature survey on effect of cement in concrete properties are used to relate with the progress of concrete compressive strength results. The laboratory conducted compressive strength test results are also narrative to the fineness, lime concentration and particle size distribution of the cements.
As shown on the analysis part, the expected concrete strength proposed using the cement test results analysis has turned out to be similar with the laboratory compressive strength test results. In fact, this has created strong confidence with regard to the other concrete properties proposed using the cement test results analysis.
Observation on the test results of this research indicates that for the mix proportions and curing conditions made in this study, at all ages and classes of concrete, Derba OPC has produced high compressive strength concrete, using as much minimum cement as possible. For concretes made
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of this cement, as the strength class increases the percentage increment of compressive strengths at 3rd and 7th days were increased from 46.99% for C-25 to 73.25% for C-90 (101.5MPa) and from 63.37% for C-25 to 86.19% for C-90 respectively. And for concretes made of Derba PPC, as the strength class increases the percentage increment of compressive strengths at 3rd and 7th days were also increased; i.e. from 41.62% for C-25 to 57.81% for C-70 and from 67.57% for C-25 to 82.09% for C-70 respectively. In doing this, I have found that the mix proportions to produce C-90 using OPC was equivalent to C-70 for PPC; and is therefore hard to produce concrete compressive strength of above C-70 using Derba PPC, but was possible to achieve up to 80.5MPa using it.
Therefore, the PPC cannot produce a 28th day concrete compressive strength as high as that of the OPC. The low pozzolanicity of the natural pumice used in production of the PPC should be the reason for the ultimate strength of concretes made of the PPC to be lower than that of the OPC.
Finally, following an in-depth multidimensional analysis of the title, I have recommended potential counter measures to ensure sustainable cement production and development in the construction industry of Ethiopia.
Key words: Cement, Chemical Composition, Compressive Strength, Concrete, Derba OPC, Derba PPC, Particle Size Distribution.
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Keywords
Cement, Chemical Composition, Compressive Strength, Concrete, Derba Opc, Derba Ppc, Particle Size Distribution