Concrete is a material both weak and strong. Its durability decreases under negative impact of several chemicals. In particular, when some sulphates in sea and ground waters react with cement paste, concrete expands and cracks; therefore, concrete has a very short life span. In that case, either the effects of sulphates should be suppressed as much as possible, or the performance of concrete sh...

Mine waste constitutes one of the biggest environmental and management problems, both due to its quantity danger when they are rich in toxic elements. There is a wide variety from oxidation ores metal mining areas, sulphide other minerals. These residues may be enriched potentially elements that can spread contaminate ecosystems, farmland villages. This study has focused on characterization eva...

To clarify the action of dextran sulphate, a heparin analogue, in the clotting of fibrinogen by thrombin, determinations were carried out on the clotting activity, the release of fibrinopeptides from fibrinogen, and the hydrolytic activity of thrombin against a peptide chromogenic substrate in the absence or presence of antithrombin III (heparin cofactor). It was shown that dextran sulphate its...

Computer models for cement hydration has been proven to be a useful tool for understanding the chemistry of cement hydration, simulating the microstructure development of hydrating paste and predicting the properties of the hydration process /1/. One of these advanced models is CEMHYD3D, which is used and extended within the University of Twente for the last 12 years with pore water chemistry /...

Several types of sulphatases occur in nature. These are distinguished by the nature of the ester group found in the ethereal sulphates which they hydrolyse (Fromageot, 1950). Takadiastase, a commercial preparation of Aspergillus oryzae, possesses arylsulphatase (phenolsulphatase) activity (Neuberg & Kurono, 1923), for it hydrolyses phenolic monoesters of sulphuric acid but has no action on alip...