Title: Effect Of Citric Acid and Polycarboxylate Superplasticizers (PCE) on Hydration and Rheology of Sulfoaluminate Cement

Author(s): R.Belhadi, A. Govin, and P. Grosseau

Publication: Symposium Paper

Volume: 349

Issue:

Appears on pages(s): 408-417

Keywords: Citric acid, competitive adsorption, CSA, dispersing effectiveness, hydration, polycarboxylate superplasticizer (PCE)

DOI: 10.14359/51732761

Date: 4/22/2021

Abstract:

The production of normal portland cement (NPC) accounts for about 5%-7% of the total man-made CO₂ emissions. One of the low CO₂ alternatives to NPC is sulfoaluminate cement (CSA), mainly composed of ye’elimite (C₄A₃S), belite (C₂S) and sulfate source (CS or CSH₂). Its main hydrated phase is ettringite (C₆A₃SH₃₂). CSA are known for their poor workability and their short setting time, which require the use of superplasticizers and retarders.

The aim of this work is to investigate: (i) the effect of citric acid and polycarboxylate superplasticizers (PCE) on the hydration and rheology of CSA; and (ii) the effect of citric acid on the dispersing effectiveness of PCEs. Two PCEs, with the same chemical structure and different molecular structure, were studied. Isothermal calorimetry and thermogravimetric analysis (TGA) were used to describe the hydration process, while rheological properties were characterized with a flow test. Adsorption measurements were carried out with total organic carbon analyzer and ionic chromatography. The results show that the combination of citric acid and PCE allows better retention of workability over time. However, a competitive adsorption between citric acid and PCE decreases the initial dispersion.