Effects of superplasticizers on the carbonation resistance of C3S and C3A hydration products

Abstract

The effects of three superplasticizers, Polycarboxylic acid superplasticizer (PA), Naphthalene sulphonated superplasticizer (NS) and Aminosulfonic acid based superplasticizer (AS), on the carbonation and crystal morphology of tricalcium silicate (C3S) and tricalcium aluminate (C3A) hydration products were investigated. These three superplasticizers can improve the carbonation resistance of C3S and C3A hydrations. However, at the appropriate dosages, they have different performance in improving the anti-carbonation ability of C3S and C3A hydrations. The mechanism behind this phenomenon was investigated by analyzing the quantity and crystal morphology of calcium carbonate (CaCO3), calcium hydroxide (CH) and ettringite using thermogravimetric analysis (TGA) and Stereoscan Electron Microscopic Photograph (SEM). The formations of calcium complex with superplasticizers are also estimated by means of X-ray photoelectron spectroscopy (XPS). These three superplasticizers can change the size, amount and orientation of hydrations. Thus, the anti-carbonation ability of the hydrations was improved.