Use of wastewater sludge for base and subbase of road pavements

• It investigates the use of 20% of wastewater Sludge by weight in pavement base layers.
• Sludge-soil mixtures with different additive (lime, cement and emulsion) were studied.
• Soils mixtures improved the mechanical behavior with the additives.
• Resilient modulus of the mixtures was greater when compared to the traditional materials of base.
• The addition of 1% of emulsion to the mixture supplied the highest increments of resistance.

The occurrence and destination of wastewater sludge in the soil and hydric resources has been recognized as an emerging issue in preserving the environment. This residue is formed by all solids removed during the effluent treatment process. Conventional solutions of sending sludge to landfills or depositing it on land or in rivers are expensive and dangerous. This paper investigates the application of the stabilization/solidification technique for wastewater sludge using lime, cement and bitumen as additives. The modified soil samples were tested for the following parameters: California Bearing Ratio (CBR), Unconfined compressive strength (UCS), Indirect tensile strength (ITS), Resilient Modulus (RM), and deterioration tests (LWT e WTAT). The addition of 1% emulsion as an additive to the mixture supplied the highest increments in strength. Furthermore, the addition of only 1% of lime or cement increases the values of the tests by about 200%. These results are acceptable values for pavement purposes, from the structural point of view.