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Task 04

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Documentation of the quality of the ashes

DTI is responsible for this task, which includes carrying out analyses, statistical treatment of results, evaluation and reporting. Finally, a “Product Standard” for bio ash will be drafted. The chemical and physical properties of the bio ash from each of the two WWTP will be assessed six times at regular intervals during one full year.

In order to manufacture concrete of consistent quality with bio ash, it is essential to know that the properties of the ash vary only within certain limits. It is known from past years analyses of the bio ashes that the elemental composition (including heavy metals) is rather consistent. Data from AWS show coefficients of variance (c.v.) in the range of 5-15%. However, only very few data on bio ash tested according to EN 450-1 “coal combustion fly ash” exist. The EN 450-1 tests performed on bio ash, although designed to evaluate coal combustion fly ash, are considered to provide the information needed to evaluate how well bio ash will perform in concrete. Therefore, EN 450-1 will serve a reference document for this task.

Full testing confirming to EN 450-1 5.2 (chemical properties) and 5.3 (physical properties) will be performed on six bio ash samples from each WWTP. The samples will be taken every two months over a full year at each of the two WWTPs.

In addition to the EN 450-1 analyses, the particle size distribution of the ashes will be analysed by Sedigraph for particle smaller than 100 microns, the mineralogy of the bio ashes will documented using optical microscopy, scanning electron microscopy, and X-ray diffraction, and the heavy metal content will be estimated by WDXRF-analyses. The particle size distribution of the ash will influence the workability of the concrete, and any substantial variation in particle size distribution may influence the concrete manufacturer’s ability to manufacture consistent quality concrete. Information about the mineralogy of the bio ash is essential to understanding and evaluating the bio ash in terms of strength development and reactivity in general (desirable and un-desirable).

The analysis results will be statically treated and evaluated with respect to production of consistent quality concrete. Statistical treatment of analysis results will be carried out on a semi-annual basis and a short progress reports issued. At the conclusion of the project a final report also including evaluation of the data in terms of concrete production will be issued. The report will have strong ties to Tasks 5, 6, and 8.

Progress Indicators – 1) All ash samples collected from incineration plants, 2) All chemical and physical testing initiated.

Expected results - The task is expected to provide a good overview of the variations in bio ash properties over the full production year.

Constraints - If the variations in the bio ash properties are found to be substantial it may limit the potential applications of bio ash concrete. However, the larger the plants are the less variation is to be expected, and the two plants included in this project are relatively large.