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New environmental challenges and research opportunities arise on the use of solid wastes as well as their basic properties. In fact, recycling of these wastes and their by-products is attracting increasing interest worldwide because of the high environmental impact in the cement, concrete and other industries. Two types (type1: Fa100 and type 2: Ba100) of sludge ashes from the sludge waste center of Camberene (Senegal) were combined with different proportions of lime to assess their potential use in civil engineering. XRF, optical microscopy and spectroscopy were used to characterize the samples. The following major elements are present in the ashes: SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, P 2 O 5 . For the minor elements their concentration are very important in type 1 compared to those in type 2. These ashes have similar composition with cement except for CaO. The measurement of absorbance on the ashes shows a clear difference in optical absorption between samples. The lime pellet transmits more compared to Ba100 and Fa100 pellets. The materials obtained by mixing ash with lime in various proportions have a lower optical transmission with respect to lime and ash taken separately. Thus, the designed materials transmit less light which suggests an improved thermal isolation. The studied ashes suggest that they are not dangerous based on the Annex III of (criterion H14 of Directive 91 / 689 / EEC).

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Solid wastes and their by-products are gaining interest worldwide given their high environmental impact. Fly ash and Bottom ash from Camberene sludge waste center (Senegal) were characterized to assess the heavy metal contamination (using XRF and the Toxicological Risk) that is very important in type 1 unlike in type 2. The Index of geo-accumulation (Igeo), the Pollution load index (PLI), the Enrichment factor (EF) and Contamination factor (CF) have been computed to evaluate the contamination rate. These show that the fly ash has aIgeo value of 3.57 for Pb and 3.04 for As which means they are very polluted. For Cu we have an Igeo value of 4.23 and for Zn it is 4.67 so these ashes are strongly to extremely polluted by Cu and Zn but unpolluted to moderately polluted by Cr. For the bottom ashes we have Igeo values of 3.03 for Cu and 3.02 for Zn, to say they are also strongly polluted. However, they are not polluted by Cr and are only moderately polluted by Pb and As results confirmed by the EF calculation. Fine and dirty ashes have significantly been enriched by the metal As with an EF of 13.71 while for Pb its EF is 19.10 for the fine ash. As for the bottom ash we have respectively 7.26 and 5.19 for the EF of As and Pb. From the values of PLI these ashes are very highly polluted. Their possible dangerousness depends essentially on their heavy metal contents (criterion H14 of Directive 91 / 689 / EEC). In this Directive the material is toxic if its content in heavy metal is higher to some thresholds (see Annex III, Table 6). Most of their heavy metal contents are below the threshold in Annex III, indicating their harmlessness. This analysis highlighted the principal characteristics to be taken into account before using the SSA properly.

The disposal of waste has become an environmental issue due to the limited available landfilling space. This paper aims to compare the characteristics of hydrated lime with fine sewage sludge ash (FSSA) and coal fly ash (CFA). Multiple techniques, X-ray fluorescence (XRF), X-ray diffraction (XRD), the Fourier transform infrared (FTIR), compressive strengths, thermophysical properties, and setting time were used to assess the physicochemical characteristics of the lime-based materials. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of ashes, lime and binders. The results showed that the chemical composition of ashes is similar to that of cement. Besides glass, the main minerals identified in CFA and FSSA are quartz (SiO 2 ) and anhydrite (CaSO 4 ). Moreover, calcium aluminium oxide (Ca 3 Al 2 O 6 ) was detected for CFA and phosphorus calcium silicate (Ca 2 SiO 4 -Ca 3 (PO 4 ) 2 ) for FSSA and minor phases were detected for both. FTIR measurements were carried out to characterize the inorganics components of different samples. Compressive strengths of mortars with different formulations have shown that both have a long-term positive effect which might be related to a pozzolanic activity. For the CFA the L 3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others while for the FSSA the L 4 binder consisting of 80% fine ash and 20% lime has a higher compressive strength than the others. Both binders setting start times are greater than that of cement but shorter than that of lime. The study of the thermophysical properties of binders shows that they have a higher thermal resistance than cement mortar. Moreover, binders heat up less quickly because of their low effusivity compared to cement. Lime-based ma-