Study on the Variability of Ordinary Portland Cement Properties in Ethiopia
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Date
2021-06
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Addis Ababa University
Abstract
Cement is the key ingredient in the production of concrete. It has two functions strength inducing and binding property. Concrete production aims to satisfy the acceptable workability of freshly mixed concrete and desired strength and durability of hardened concrete. Among many factors material properties, mix proportioning, handling, placing, curing condition, testing of concrete are major considerations to produce concrete for a particular condition of use. An increase in the variation of cement properties leads to a corresponding variation in concrete properties. This forces one to use higher cement content during mix proportioning. The cement that is classified as the same type varies considerably from one plant to another plant depending on the changes in raw material, burning condition, and cooling rate.
Therefore, this study focuses on the evaluation of locally produced Portland cement performance. Specifically, the variability of physical and mechanical properties of Portland cements as per the Ethiopian standard, CES 28, studied. The scope of this study was limited to thirty cement samples from five cement producers having large market-shares in the Ethiopian cement market, (i.e. Dangote Cement, Derba Midroc Cement, Messebo Cement, Mugher Cement, and National Cement) for six consecutive months (March 2018 – August 2018). The cement samples were collected monthly from retail shops and cement factory stores. All the cement samples were grade 42.5. For the analysis of compressive strength, setting time, consistency, and soundness of cement variability, coefficient of variation (CoV) and student t-Distribution were used.
Two out of five cement brands did not fulfill the requirement of CES 28 in 2nd day compressive strength. Moreover, the variability of 2nd day compressive strength within six months varied from 5% to 20% within the same brand of cement. For 28th day compressive strength results, one out of five cement brands did not fulfill the requirement of CES 28. Additionally, the variability of 28th day compressive strength within six months varied from 3% to 8% within the same brands of cement. In the case of setting time and soundness properties, all cement brands conformed to the requirement of CES 28 initial setting time and soundness requirements. However, the variability of the results showed that all cement brands have high variability in both setting time and soundness.
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Cement, compressive strength, setting time, soundness, consistency