An original experimental campaign never conducted until now on Non-Hazardous Waste Incineration aggregates is presented in this paper. The experiments were conducted in two phases: Scanning Electron Microscopy (SEM) and instrumented indentation. A cartography followed by a series of Quantitative Chemical Microanalysis (QCM) was carried out on the 0/12.5 mm fraction of the particle size distribution. Instrumented indentation tests were carried out on isolated particles of 25 mm in diameter. Observations at the SEM yielded the exact chemical composition of the bottom ashes. It has been found that the proportions of the chemical elements composing the material are slightly different from those of other studies. This difference has made it possible to note that the zone of production of the bottom ash significantly influences their physicochemical characteristics. From the indentation curves obtained, the “Olivier and Pharr” method was used to determine the reduced modulus of elasticity “Er”. Mean values of approximately 65 GPa and 40 GPa were obtained respectively for vitreous phases and less vitreous ones.

This article first talks about railways in general and ballast in particular. An inventory is then made on the modernization of the Senegalese ballast railways. In the second phase, an experimental work of characterization of basaltic aggregates of Diack (Locality of Ngoundiane, Thiès region, Senegal) is presented. The grain size studied is 25/50 mm as for any material studied for use as railway ballast. Experimental work presented consists of the characterization of the shape of an aggregate using the NF P 18-301 standard. The test consists of comparing the volume of the aggregate to that of an equivalent sphere with the largest diameter of the aggregate, by calculating the average volume coefficient. With a Representative Elementary Volume (REV) of 6 aggregates, the volume coefficient "C v " fluctuates between 0.27 and 0.49 with an average volume coefficient of 0.39 which is well above 0.15. The grains studied are polyhedral and therefore have a high mechanical resistance.

Instrumented indentation tests have been carried out on an isolated 25 mm diameter particle of Non-Hazardous Waste Incineration bottom ash. These tests have enabled one to assess the intrinsic mean reduced modulus of elasticity “Er” of the particles. This result is used as input data for a 3D numerical model of Representative Elementary Volumes (REV) of a road gravel made with this kind of by-products. This numerical model is based on a multi-scale hierarchical modelling strategy. The aggregates treated with cement have been decomposed into two REV at the sub-mesoscopic and mesoscopic scales. The numerical simulations campaign (“virtual laboratory”) lead to the following results. At the sub-mesoscopic scale, we determined the input parameters for the Concrete Damaged Plasticity Model (CDPM) used at the mesoscopic scale. At the mesoscopic scale, the mechanical characteristics of the road aggregates usually determined through experiments have been found. The non-hazardous waste incineration bottom ashes treated by hydraulic binder was classified into mechanical classe 3.

An extensive experimental work of instrumented indentation on isolated particles of Non-Hazardous Waste Incineration bottom ash (NHWI) is presented in this paper. The aggregates studied come from the Garenne quarries at Vignoc (Brittany, France). Two spherical tungsten carbide indenters of respective 0.5 and 140 mm radius “R” were used for test series “A” and “B”. The particles studied have diameters ranging between 20 and 25 mm. With a 0.5 mm radius indenter, average reduced elastic moduli ranging from 15 to 68 GPa were found. An average reduced elastic modulus of 15 GPa was found with the 140 mm radius indenter. The experiments made it possible to highlight the particular heterogeneity that characterizes the rigidity of the types of aggregates studied.