Early C3A hydration in the presence of different kinds of calcium sulfate

Abstract

12 13 Hydration reactions of C 3 A with various amounts of calcium sulfate hemihydrate, 14 gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, 15 and a monitoring of the ionic concentrations of diluted suspensions. This study 16shows that sulfate type used modifies the early C 3 A-CaSO 4 hydration products and 17 the rate of this hydration. The fast initial AFm formation observed before ettringite 18 precipitation in the C 3 A-gypsum system is avoided as soon as hemihydrate is 19 present in the suspension. This was attributed to.higher super saturation degrees and 20 then higher nucleation frequency with regard to the ettringite obtained in the 21 presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also 22 leads to an increase of the ettringite formation rate during at least the five first hours 23 under experimental conditions. 24 25

Molecular and submolecular scale effects of comb‐copolymers on tri‐calcium silicate reactivity: Toward molecular design

“…41,48,[81][82][83][84][85][86] However, it is also necessary to study the interaction between the different phases that might induce other reactions or kinetics as in pure phases systems. Lerch 87 and later Tenoutasse 30 illustrated in particular the importance of the balance between the silicates, the aluminates and the sulfates ( Figure SB3.2).…”

Impact of environmental moisture on C3A polymorphs in the absence and presence of CaSO4 · 0·5 H2O

“…For example, it is well established that at the early stage of its hydration with liquid water, C 3 A can react with sulfates to form AF m or AF t phases (Black et al, 2006;Brown et al, 1984;Minard et al, 2007;Pourchet et al, 2009). Thus, formation of those phases may significantly affect further sorption of water vapour by cement.…”

Influence of Lithium Carbonate on C3A Hydration

“…As for CCLS paste (Figure 8(c)), the main crystalline phases are anhydrous C 3 A, ettringite, Mc, Ms, and [14]. In Table 3, as for CCL paste, the ratio of Mc to C 3 A of CCLS paste is higher, indicating that Li 2 CO 3 can partly promote the C 3 A hydration in the presence of CaSO 4 ·2H 2 O, which is consistent with the result of heat evolution ( Figure 7).…”

“…Conductimetry and isothermal microcalorimetry of hydration system are carried out based on the literature [14]. Meanwhile, the paste is dried at 55°C and then ground to a particle size smaller than 45 μm, and the mineralogical compositions are performed by XRD (D8, Bruker AXS Corporation, Germany) with a scan rate of 1.000°per min and FTIR (Nicolet 6700, ermo Electron Scienti c Instruments, USA) with a frequency range of 4000-399 cm …”