This study analyzed the behavior of two laboratory-synthesized calcium silicates, C 3 S and C 2 S, after hydration in 8-M NaOH and in water as a control. Two-and 28-d mechanical strength values were determined and the products were characterized with XRD, TEM, and 29 Si and 23 Na MAS NMR. The results showed that hydrating C 3 S in a highly alkaline medium had no significant effect on the mechanical development of the material, whereas in C 2 S hydration, that medium hastened hydration substantially, impacting setting and hardening times. This finding has technological implications, given the low early-age reactivity of dicalcium silicate under normal hydration conditions.

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This study analyses the behavior of calcium silicates C 3 S and C 2 S hydrated in two alkaline media, Na 2 CO 3 and Na 2 SO 4 . The silicates were synthesized with laboratory reagents and hydrated in water, to which solid-state alkaline activators with 4 wt% Na 2 CO 3 or 4 wt% Na 2 SO 4 were added. Two-and 28-day mechanical strength values were determined and the reaction products were characterized with XRD, SEM/EDX, and 29 Si and 23 Na MAS NMR. The findings showed that the presence of Na 2 CO 3 hastened hydration kinetics and stimulated early-age mechanical strength development in both silicates. The most significant effect of sodium sulfate, however, was observed in the 28-day material in both silicates, in which it raised strength by stimulating the precipitation of C-S-H gels with a high percentage of Q 2 units.akali activation, calcium silicate, calcium silicate hydrate, cements, gels

This study explored the behavior of laboratory-synthesized tricalcium aluminate (C 3 A) in alkaline media. In all the trials, the C 3 A was hydrated with water containing a certain percentage of alkali activators (4% Na 2 CO 3 , 4% Na 2 SO 4, or 8% Na 2 SO 4 by weight of C 3 A). Two-and 28-day mechanical strength values were determined and the products were characterized with XRD, DTA, and NMR. The compressive strength of the C 3 A pastes rose in the presence of the alkaline activators used in this study. The alkalis induced the formation of calcium monocarboaluminate (C 4 AČ H 11 ) as the main hydration product in all cases. In addition, when Na 2 SO 4 was added, a sodium calcium sulfoaluminate, phase U (C 4 ASˇNH 16 ), formed. The presence of this mineral, whose formation is associated with high pH values, furnished indirect information on the alkalinity in the medium.

The mechanical performance of a hybrid cement containing 48% fly ash, 48% mineralized belite clinker, 1. 5% gypsum and 2.5% Na 2 SO 4 was analyzed and the hydration products were identified. The findings showed that the newly designed cement met European standard EN 197-1 compositional, mechanical and setting time requirements (cement type IVB). The hydration products forming in this blended "alkaline-belite" cement (as it was determined through XRD, 29 Si and 27 Al MAS NMR and electron microscopy) consisted in a mix of cementitious gels: C-(A)-S-H and N-(C)-AS -H, which interacted and over time evolved toward the latter with no detriment to the mechanical strength developed by the cement.

We report a case of congenital cystic adenomatoid malformation (CCAM) of the lungs resulting in sudden death immediately after birth. The case is extremely unusual because of the diffuse bilateral involvement. The extensive involvement of both lungs could explain the abrupt onset of the symptoms and the ineffectiveness of resuscitation attempts. The presence of cartilage as a part of the malformation adds interest to the case, since it is seldom found in this malformation and to the best of our knowledge has been reported only exceptionally in a type II CCAM.