Use of a reference limestone fine aggregate to study the fresh and hard behavior of mortar made with recycled fine aggregate

Recycled fine concrete aggregates (RFA) are not enough used in the construction sector, mainly because of their high water absorption capacity. These fine particles are composed of crushed natural aggregate and adherent hardened cement paste. The main goal of this research is to compare the behaviors of mortars made either with RFA or with a model limestone fine natural aggregate (LFA). The LFA is prepared in order to obtain physical properties as close as possible to those of the RFA. A specific characterisation is carried out to compare the density, water absorption, morphology of grains, size distribution and packing density of both aggregates. Mortars are then manufactured with same composition and same volume of LFA and RFA. Different states of moisture of the RFA are studied. The fresh behaviour of the mortar made with saturated RFA is very close to that of the mortar made with LFA which confirms that the latter is a good reference compared to the RFA. Comparison of fresh behaviours of mortars made with RFA of different state of moisture to that of mortar made with saturated sand allows then to determine the water absorbed in the different moisture conditions. Afterwards, a mechanical study is realised, taking into consideration the exact quantity of absorbed water of the RFA in dry or saturated conditions. Knowing the exact effective water value allows us to study both the strength of mortar made with RFA, the strength of the matrix and the adherence between the fine aggregate and the paste.