The Impact of Sodium Salts on Alite and Cement Hydration

• 作 者: BertaMota[1]ThomasMatschei[2]KarenScrivener[1]
• 机 构: Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, STI/IMX/Station 1210
• 出 处: The 14th International Congress on the Chemistry of Cement (
• 发表日期: 2015年期

　　This work aims to clarify the impact of alkali and sulfate on the morphology of C-S-H, which is the main product of cement hydration, responsible for the development of strength.It is observed that sodium salts lead to an acceleration of the hydration rate at early ages but the effect at later ages differs.The morphology, as well as the chemical composition, of this phase is dependent on the surrounding solution composition.The presence of alkali salts appears to impact the morphology of C-S-H at early ages which at the same time seems to influence its ability to fill the space at later ages.A plain white cement system is compared to systems with the addition of NaOH and Na2SO4, two Na-salts which accelerate the hydration of cement at early ages.In the plain cement,C-S-H adopts a needled divergent structure which grows outwards from the surface.The presence of NaOH seems to lead to a C-S-H which is more parallel to the surface, without growing outwards.On the contrary,Na2SO4 leads to a comparable morphology to the one in the plain system, thus sulfate ions seem to correct the morphology of C-S-H.The same changes in the morphology of C-S-H are observed in alite-based systems.