Influence of sulfate solution concentration on the formation of gypsum in sulfate resistance test specimen

The sulfate concentration, which is required to form gypsum from portlandite, was derived from thermodynamical calculations and experimental measurements. The obtained results were compared to the sulfate concentrations in laboratory solutions that are commonly used to test the performance of concrete exposed to sulfate attack and also to sulfate concentrations that can be expected under field conditions. It was derived that the formation of gypsum can strongly affect the performance of binders in the tests, but has a less marked impact under most field conditions. An SEM investigation of mortar bars that were exposed to different sulfate concentrations supports the suggestion made.     

Einfluß von Carboxymethylcellulose auf das Verhalten von Tonsuspensionen unter besonderer Berücksichtigung des Tiefbohrsektors

The function of drilling fluid includes the removal of the cuttings from the bore hole, the supporting of the hole wall, the cooling of the bit, and the maintenance of the hydrostatic equality with the formation pressure. The clay suspension preferred to employ these purposes possess adequate flow limits and gel strengths, the water retensivity however is insufficient. With the addition of carboxymethylcellulose the dispersion of clay in water and the water retensivity are improved. In the present publication, the influence of carboxymethylcellulose in clay-water and sodiumchlorid-saturated clay-water suspension on the rheological properties and the water retensivity are investigated.