Structural Modulations in Monoclinic Tricalcium Silicate Solid Solutions Doped with Zinc Oxide, M(I), M(II), and M(III)

Abstract

Structural modulations in solid solutions of C 3 S doped with various amounts of ZnO were investigated via the selectedarea electron diffraction method. Three monoclinic modifications (M(I), M(II), and M(III)) were identified in the solid solutions. The modifications had pseudohexagonal subcells that were modulated to form supercells. Coordinates of the reflections attributable to the supercells could be expressed by the following linear combinations of vectors of the reciprocal lattices: m 1 (؊2a*/5.4 ؉ 2b*/5.4 ؊ 7c*/5.4) for M(I), m 2 (؊a*/5 ؉ b*/5 ؊ c*) for M(II), and m 3 (؊a*/6 ؉ b*/6 ؉ 7c*/6) for M(III), m 1 and m 2 ‫؍‬ ؎1 and ؎2, and m 3 ‫؍‬ ؎1, ؎2, and ؎ 3. All the monoclinic modifications possessed structural modulations of a one-dimensional type. The modulation waves could be detected as wavy contrasts by high-resolution transmission electron microscopy.

The Effect of Magnesium and Zinc Ions on the Hydration Kinetics of C3S

“…XRF revealed the content of zinc to be 0.98 wt% (±0.004%) for the alite produced with 3 wt% of zinc and 1.16 wt% (±0.004%) for the alite produced with 4 wt% of zinc. Most probably, zinc evaporates during synthesis, as also observed by Urabe et.al . No zinc oxide was detected in any sample, but small amounts of free lime were found: around 0.8 wt% for the alite with 0.98 wt% of zinc and around 0.4 wt% for the alite with 1.16 wt% of zinc.…”

“…Figure gives selected angular ranges, (a) 31.5°–33.5° 2θ and (b) 51° to 52.5° 2θ of the XRD patterns for the prepared samples. The type of polymorph is identified from the presence of two or three peaks in the 32.3°–33° 2θ and 51°–52.5° 2θ angular window and through a comparison with literature data of alite incorporating magnesium and zinc . It is observed that pure C 3 S and alite doped with zinc are triclinic and alite doped with magnesium is monoclinic.…”

“…However, a T3 structure cannot be excluded. In the literature, large amounts of zinc incorporation are reported to stabilize the M2 polymorph, whereas T2 is usually found for lower zinc concentrations. XRF revealed the content of zinc to be 0.98 wt% (±0.004%) for the alite produced with 3 wt% of zinc and 1.16 wt% (±0.004%) for the alite produced with 4 wt% of zinc.…”

“…Zinc stabilizes T1 between 0 and 0.5 wt%, then T2, M1, and M2 with increasing amounts of zinc addition. However, the reported limits for stabilization of the different polymorphs vary significantly between different studies, perhaps due to volatilization of zinc during synthesis …”

Polymorphism of tricalcium silicate in Portland cement: A fast visual identification of structure and superstructure

“…The difference between M1 and M3 polymorphs becomes evident when looking at the W3 and W5 angular windows, which have always been considered in the literature as characteristic of the various polymorphs (Bigare et al 1967, Guinier and Regourd 1969, Regourd 1979, Qing et al 1992, Urabe et al 2002: in both cases, the doublet of Bragg lines is shifted towards the large angles for the M3 alite. However these windows are not able to assess the presence of an eventual superstructure.…”