Evaluation of effects of C A and SOA contents in Portland cement on its compressive strengt6, hydrat!on rate and products. Three cement samples varFing in C3A content and one varying in SO 3 content were used, hydrated initially at three temperatures. Compressive strength, bound water content, free lime content and Differential Scanning Calorimeter curves were determined during the progression of hydration. In interpretation bound water was used as a measure of quantity of binding material and Free Lime to Bound Water Ratio (FLWR) -of chemical constitution and quality. On a essay6 d'dvaluer les effets des teneurs du ciment Portland en CBA et en S03 sur sa r6sistance ~ la compression, son taux d'hydratation et ses produits d'hydratation. On a examin6 trois ciments Portland ~ diffdrentes teneurs en C3A et un ciment Portland ~ diff6rentes teneur en SO 5. L'hydratation initiale a did faite ~ trois temp6ratures diff6rentes. On a suivi le progrds de l'hydratation par la d6termination de la r6sistance ~ la compression, de la teneur en eau li6e e% en chaux fibre et, enfin, par des courbes d'un calorimetre ~ balayage diff6rentiel (Differential Scanning Calorimeter). La teneur en eau li6e a 6tait employde pour 6valuer la quantit6 des produits d'hydratation. Le rapport des teneurs en chaux libre et en eau lide (FLWR) semble correspondre ~ la constitution et ~ la qualit6 du gel.