Influence of hardened cement paste content on the water absorption of fine recycled concrete aggregates

Abstract

A linear relationship was found between the mean size of four granular classes (0/0.63, 0.63/1.25, 1.25/2.5, 2.5/5 mm) of different laboratory-made fine recycled concrete aggregates (FRCA) and their hardened cement paste content (CPC). A method based on salicylic acid dissolution was specifically developed for the measurement of CPC. Results showed that bound water and density of FRCA were strongly correlated with their CPC. Identically, the water absorption coefficient also followed a linear trend as a function of the CPC but only for the three coarser granular classes. Indeed, the water absorption coefficient of the finer fraction of FRCA (0/0.63 mm) cannot be correctly measured using European standard method EN 1097-6 or method no. 78 of IFSTTAR; but it can be obtained by extrapolation from the previous linear trend. As a consequence, the accurate total water absorption of FRCA (fraction 0/5 mm) can be estimated.

Keywords:

• cement paste
• recycled concrete aggregates
• water absorption
• salicylic acid
• granular class
• porosity

Acknowledgments

Authors would like to thank the Lafarge Company for its cement and the Holcim Company for supplying natural aggregates. Authors would also like to thank the Colas Company for supplying materials. Finally, authors would like to thank the China Scholarship Council (CSC) for its financial support.