CONCRETE ATTACK BY FEED ACIDS - ACCELERATED TESTS TO COMPARE DIFFERENT CONCRETE COMPOSITIONS AND TECHNOLOGIES

Concrete in agricultural construction is often subjected to aggressive environmental conditions. For example, spilled meal-water-mixtures an d silage effluent contain lactic and acetic acids, which degrade concr ete. Through accelerated laboratory tests, the resistance of different concretes to these acids was studied. The variables were cement type, cement content, aggregate type, and consolidation. The data presented show a well-consolidated concrete with blast-furnace slag cement and a fairly high cement content to be the most durable. High alumina ceme nt was advantageous under certain conditions. Use of limestone aggrega tes reduced the effect of other variables and protected the hardened c ement paste, particularly when portland cement was used. Three stages in attack were distinguished: 1) the concrete was weakened on the surf ace by chemical attack only, 2) the weak surface layer was removed by mechanical impact, 3) a part of the cement paste and (limestone) aggre gates was dissolved. The measure of deterioration had an influence on the significance of differences between concrete samples. Therefore, i t is emphasized that care is required when comparing results from diff erent investigations.