ANSWER!

CtO, the Cement factories technical information office has conducted extensive studies on the impact of acidified slurry on different concrete grades. The conclusion for new construction is that using conventional concrete grades with 15% fly ash, durability problems are not expected over a 25 year time period. For existing housing facilities, there is also no significant risk when converting to acidified slurry, provided that the concrete otherwise meets the requirements of the relevant environmental classes.
CtO’s recommendations can be downloaded (Document produced by Aalborg Portland) here:
“Anbefaling til valg af betonkvalitet til gylleanlæg til forsuret gylle”.