Rheological and hydration characterization of calcium sulfoaluminate cement pastes

Cement and Concrete Research

León‐Reina

et al. 2013

157

The main objective of this work is to study the hydration and properties of calcium sulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied parameters were: i) FA content, 0, 15 and 30 wt.%; and ii) water addition, water-to-CSA mass ratio (w/CSA = 0.50 and 0.65), and water-to-binder mass ratio (w/b = 0.50). Finally, compressive strengths after 6 months of 0 and 15 wt.% FA [w/CSA = 0.50] mortars were similar: 73 ± 2 and 72 ± 3 MPa, respectively. This is justified by the filler effect of the FA as no strong evidences of reactivity of FA with CSA were observed. These results support the partial substitution of CSA cements with FA with the economic and environmental benefits.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydration studies of calcium sulfoaluminate cements blended with fly ash

García-Maté

Cement and Concrete Research

León‐Reina

et al. 2013

157

“…The amount of the sulfate source was previously optimized elsewhere [30] through phase assemblage and mechanical strenght measurements, and also the effect of different sulfate sources [12] was studied. Due to the short setting time of bassanite-pastes the hydration and performances of the corresponding pastes and mortars are expected to be controlled/improved through the addition of additives.…”

Section: Introductionmentioning

confidence: 99%

Tailored setting times with high compressive strengths in bassanite calcium sulfoaluminate eco-cements

García-Maté

Londoño-Zuluaga

Cement and Concrete Composites

et al. 2016

This work deals with the hydration of a calcium sulfoaluminate (CSA) eco-cement prepared with bassanite and different additives (type and content) at a fixed water/CSA ratio of 0.5. Pastes prepared with bassanite show high water demands, high viscosity values and short initial setting times which are related to the fast dissolution rate of bassanite and the subsequent precipitation of gypsum. These facts have a dramatic effect onto the mechanical strength values, and make necessary the addition of additives.Here, the addition of different amounts of specific retarders (polycarboxylate, tartaric acid and phosphonic acid) not only improved the workability of pastes and mortars, but also delayed the setting time, by modifying the dissolution rates of the phase(s), and improved mechanical strengths.Finally, mortars with high compressive strengths (46 and 84 MPa at 1 and 7 days of hydration, respectively) and, chiefly, tailored setting times with high strengths have been prepared.

“…In addition, the interest in the ye'elimite structure has recently increased because it is the major component in calcium sulfoaluminate cements (CSA) [14][15][16] , and the second most relevant phases in sulfobelite cements, BCSA, (~25 wt%) [17][18][19] . CSA and BCSA cements are environmentally-friendly materials as they allow decreasing the CO 2 footprint in cement fabrication.…”

Section: Introductionmentioning

confidence: 99%

Pseudocubic Crystal Structure and Phase Transition in Doped Ye’elimite

Cuesta

Crystal Growth & Design

Losilla

et al. 2014

Self Cite

Sodalites are tridimensional alumino-silicate materials containing cages where loosely bonded anions are located. Ye'elimite, Ca 4 [Al 6 O 12 ]SO 4 , is outstanding as an aluminate sodalite with a flexible framework accepting several type of dopants with important structural consequences. Moreover, ye'elimite is also important from an applied perspective as it is the most relevant phase in calcium sulfoaluminate cements. The crystal structure of stoichiometric ye'elimite has recently been unraveled but the structure of dopant-containing ye'elimite, which is presents in cements, is not well studied. Here, we report the pseudo-cubic crystal structure of doped ye'elimite, Ca 3.8 Na 0.2 Al 5.6 Fe 0.2 Si 0.2 O 12 SO 4 , from high-resolution synchrotron powder diffraction data. The powder pattern is indexed with a cubic cell and a structural model is reported based on the I4 ̅ 3m space group. However, this compound displays diffraction peak narrowing on heating. Furthermore, some high-angle split peaks become single peak on heating and a phase transition is measured at 525ºC. Therefore, it is concluded that the crystal structure at room temperature has lower symmetry although it can be described as cubic. The structural study at 800ºC suggests a truly cubic structure and we speculate that this phase transition, on heating, is likely related with the dynamical disordering of the sulfate anions. Finally it is concluded that the high temperature cubic state was not quenchable to ambient, even when the tested chemical substituents are introduced into the structure.