Investigation of The Pozzolanic Reactivity of Bagasse Ash Via Compressive Strength Development
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Date
2020-10-16
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Addis Ababa University
Abstract
Currently, the construction sector demands more materials with good quality than ever. On the contrary, materials are scarce and depleting. So, the need for alternative construction materials that are renewable, cheaper, and eco-friendly is increasing. Studies on partial and full replacement of the most widely used materials are timely. The general objective of this study is to investigate the pozzolanic reactivity of bagasse ash via compressive strength development while partially replacing cement at 10% by volume.
Rapid, reliable, and relevant (R3) testing techniques were employed. This was done by measuring the heat of hydration and by determining the amount of bound water. Test results were compared with the strength development and with the pozzolanic activity determination test. Furthermore, the characterization of pastes was also done.
The blending of cement made the paste to require more water and enhance the initial and final setting time. In reference samples, the cumulative heat flow was 284.02J/g at 170hrs and the maximum rate of heat flow was 80.08J/gh which was found at 4 minutes and 14 seconds. Whereas in blended samples the cumulative heat flow decreased to 275.18J/g at 170hours and the maximum rate of heat flow decreased to 69.41J/gh which was found delayed to 5 minutes and 13 seconds. The difference in heat of hydration between the reference and blended sample increases as time increases starting from 3J/g on the 1st day to 9J/g on the 3rd day. Blended samples were found to have 2.58% bound water(gram) content whereas the reference samples were found to have 2.89% bound water(gram) content on day 1. Compressive strength at an early age (≤ 1 day) is lower in the bagasse ash (BA) blended mortar cubes. But, during later days compressive strength of BA blended mortar cubes were the highest and quartz blended mortar cubes were the lowest. In addition to this, the pozzolanic activity of bagasse ash (PABA) was found to be 346.08mg of Ca(OH)2 per gram of bagasse ash. The proposed R3 method meets all the criteria of SCM screening tests and well correlated to the compressive strength development. Results of the R3 test were also in accordance with the findings of the PABA.
All these confirmed the presence of pozzolanic reactivity of the bagasse ash and results were found to be coherent and in agreement with each other. Therefore, improvements in the concrete property while bagasse ash is used as a partial replacing material is partly due to the pozzolanic reaction of the bagasse ash.
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Bagasse Ash, Strength, Pozzolanic Reactivity