Kirchheim Ana Paula, Rodríguez Erich D, Myers Rupert J, A Gobbo Luciano, M Monteiro Paulo J, C C Dal Molin Denise, de Souza Rui B, Cincotto Maria Alba
Department of Civil Engineering of Federal, University of Rio Grande do Sul (UFRGS), Porto Alegre 90035-190, Brazil.
Department of Structures and Civil Construction, Federal University of Santa Maria (UFSM), Santa Maria 971015-900, Brazil.
Materials (Basel). 2018 Apr 7;11(4):568. doi: 10.3390/ma11040568.
The tricalcium aluminate (C₃A) and sulfate content in cement influence the hydration chemistry, setting time and rheology of cement paste, mortar and concrete. Here, in situ experiments are performed to better understand the effect of gypsum on the early hydration of cubic (cub-)C₃A and Na-doped orthorhombic (orth-)C₃A. The isothermal calorimetry data show that the solid-phase assemblage produced by the hydration of C₃A is greatly modified as a function of its crystal structure type and gypsum content, the latter of which induces non-linear changes in the heat release rate. These data are consistent with the in situ X-ray diffraction results, which show that a higher gypsum content accelerates the consumption of orth-C₃A and the subsequent precipitation of ettringite, which is contrary to the cub-C₃A system where gypsum retarded the hydration rate. These in situ results provide new insight into the relationship between the chemistry and early-age properties of cub- and orth-C₃A hydration and corroborate the reported ex situ findings of these systems.
水泥中的铝酸三钙（C₃A）和硫酸盐含量会影响水泥浆体、砂浆和混凝土的水化化学、凝结时间及流变学性能。在此，进行原位实验以更好地理解石膏对立方晶型（cub-）C₃A和钠掺杂正交晶型（orth-）C₃A早期水化的影响。等温量热法数据表明，C₃A水化产生的固相组合随其晶体结构类型和石膏含量而发生显著变化，其中石膏含量会引起放热速率的非线性变化。这些数据与原位X射线衍射结果一致，该结果表明较高的石膏含量会加速正交C₃A的消耗以及钙矾石的后续沉淀，这与立方C₃A体系中石膏延缓水化速率的情况相反。这些原位研究结果为立方和正交C₃A水化的化学性质与早期性能之间的关系提供了新的见解，并证实了这些体系已报道的非原位研究结果。
