Abstract
The relationship between the rebound number and strength of concrete varies as a function of the age of concrete, but the effect of age can generally be ignored for concrete between 3 days and 3 months old. However, for older concrete, it may be possible to develop the age factor of the rebound number of concrete taking into account the concrete's history. An investigation on the age factor of the rebound number has been made, using concrete specimens of 500 x 1200 x 1200 mm with the age of 20 years. The calibration curve varies according to the age of the concrete used in the test, and the age factor varies according to the degree of compaction, the use of a permeable sheet as the mould, the strength of the concrete, and the age of the concrete used to obtain the calibration curve.
