ABSTRACT
A b s t r a c t Research was c a r r i e d out on the i n f l u e n c e s of type (hemihydrate, n a t u r a l anhydrite) and amount of calcium sulphate i n p o r t l a n d cements on i n i t i a l c onsistency and s t i f f e n i n g of standard mortars (model concretes). In order to achieve good w o r k a b i l i t y and l i t t l e s t i f f e n i n g the p r o p o r t i o n of the e a s i l y s o l u b l e sulphate must be adjusted to the s p e c i - f i c p o r t l a n d cement c l i n k e r used and to cement fin e n e s s . Apart from t h i s o p t i m i z a t i o n , mortar consistency i s i n f l u - enced mainly by the amount of AI2O3 contained. The e f f e c t of v a r y i n g working temperatures i s i n f l u e n c e d by the amount of hemihydrate i n p o r t l a n d cements. Keywords : Fresh Concrete, Consistency, S t i f f e n i n g , Workab i l i t y , Calcium Sulphate, P o r t l a n d Cement, Temperature
1 I n t r o d u c t i o n
W o r k a b i l i t y i s an important q u a l i t y of f r e s h concrete on s i t e , determined mainly by i t s consistency. The r e l i a b l e attainment of a req u i r e d consistency under v a r y i n g condit i o n s represents t h e r e f o r e one of the main tasks of f r e s h concrete technology.
