13 Recycled Concrete Aggregates are highly porous and may therefore absorb more water 14 than natural aggregates. Several methods allow for the measurement of water 15 absorption requiring drying at temperature above ambient conditions. We show here 16 that, for temperatures above the ambient temperature (> 30°C) and at low relative 17 humidity, the drying of recycled aggregates removes some bounded water contained in 18 hardened cement paste and increases both measured porosity and water absorption. 19 Porosity and XRD suggest that porosity increases due to ettringite dehydration. Thus, 20 the drying step required to characterize recycled aggregates leads to a systematic 21 overestimation of the water absorption. Moreover, this overestimation induces an error 22 in mix-design leading to a higher effective water/cement ratio. If absorption and water 23 content are measured with the same preparation protocol, correction is not needed. We 24 finally propose a correction method for the water absorption measured according to the 25 standard protocol (drying at 105°C).