Effect of a carboxylic acid on the rheological behavior of an aluminous cement paste and consequences on the properties of the hardened material

Aluminous cement pastes (Secar 71 from Lafarge) containing increasing quantities of acetic acid, HOAc, are prepared ((wHOAc/wcement) × 100 ranges from 0 to 10%). Pastes containing HOAc present a Newtonian behavior. The best dispersion is obtained when the mass content of acid with respect to the cement is equal to 0.5%. Microstructural characterizations of samples aged for 4 days at 20 °C and 95% relative humidity reveal a significant increase in density, a reduction in porosity as well as a displacement of pore diameter towards low sizes. The open porous volume decreases with time from 25 to 9 vol.% when samples are 4 days and 6 months old, respectively. The addition of HOAc also has a beneficial effect on the flexural strength of set samples.