Combined experimental methods to assess absorption rate of natural and recycled aggregates

The assessment of maximum water absorption and absorption rate are necessary in order to design concrete mixtures from relatively porous aggregates, such as recycled aggregates. The experimental research presented in this paper investigates and improves the existing procedures for determining water absorption rates. New equations and experimental procedures are proposed to correct the existing procedures. Three types of aggregates were studied. Natural aggregates with two gradations 4-10 and 6.3-20 mm, natural limestone aggregates with gradation 4-20 mm and recycled aggregates with two gradations 4-10 and 10-20 mm. For each granular type, two tests were conducted, the first with oven-dried aggregates and the second with aggregates having initial moisture. Effects of initial moisture state were deduced from the first part of the experimental program. Then existing procedures were combined in order to design new procedures. Finally a method was developed for testing the volume variation of aggregates by hydrostatic weighing; the detailed testing procedure and equations of the new method are illustrated using the natural and recycled aggregates. Results from pycnometer method and hydrostatic weighing showed very good correlation.