Homogenization process of field samples of recycled aggregates

•A homogenization process of recycled aggregate is analyzed.•The uniformity of the recycled aggregate is compared with reference methods.•The evolutions of the water absorption, granular composition and size are evaluated.•Recommendations could be deduced for a method to homogenize the field sample. The production of recycled aggregates requires thorough quality control. Sampling procedures already exist to ensure the representativeness of natural aggregates. However, given the heterogeneity of recycled aggregates, new sampling procedures have to be developed. The first step is the homogenization of the field sample which must then be reduced to lab size elementary samples. A typical homogenization process using a front-end loader was analyzed here. The tests were conducted on a field sample of 1 m3 of RA, reconstituted from crushed concrete, brick and asphalt. The field sample was mixed and the uniformity was characterized at two levels of mixing. The obtained uniformity was then compared, firstly, with the uniformity of the same field sample after homogenization using a large mixer and, secondly, with the result of the homogenization on a large sample in the laboratory. The local uniformity was obtained fast but the mixing should be prolonged to decrease the heterogeneity between different zones of the mixture. 6 loading/unloading mixing cycles with the loader appeared to be enough, even if it seemed in principle possible to increase the mixture uniformity nearly twice. In fact, one main drawback of the method was the evolution of the size and water absorption with the homogenization process. So, instead of continuing further the loader mixing with additional degradation of the mixture, it is suggested to increase the number of elementary samples to be analyzed in the laboratory.