Sewage sludge ash in concrete. Investigation of possibilities for use

The experimental sewage sludge ash in this project is obtained from an open air deposit at Lynettefællesskabet I/S. Replacing the cement with the ash resulted in a significant decrease in compressive strength from about 45MPa for the reference mortar to 35 MPa and 25MPa for 10% and 20% replacement, respectively, for 7 days cured samples. Replacing 10% sand with the ash resulted in a similar strength development over 42 days as the reference sample. The best result obtained regarding highest compressive strength was for mortar samples where 5% sand was replaced with milled ash. Here the 7-days compressive strength reached 60 MPa, which is much higher than the 45 MPa of the corresponding reference sample without ash.

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