The main objective of this work is to study the hydration and properties of calciumsulfoaluminate 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
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