Wirksamkeit von Quellzusatzen im Beton fur den Ausgleich von Zwangspannungen

Restraint stresses which can cause cracking in concrete members, are reduced in some countries by the addition of expansive additives. Such products, which have not been licenced in the FRG up to now, normally contain calciumsulpho-aluminates and/or free lime. Investigations on free and restrained specimens showed that the optimal dosage of the expansive additive depends to a great extent on the cement used. At a too low dosage (i.e. lower than about 5% of cement) the efficiency is nearly zero, at too high dosage damaging can occur. For preventing such damage, also during a later wet period, the water-cement ratio of concrete with expansive additives should be at least 0,50; also careful curing of the concrete within the first few days is very important.