Sewage Sludge: Some Applications in Civil Engineering

The use of civil construction waste has been consolidated as a way to achieve sustainability in civil construction, as well as reduce the environmental impacts resulting from the improper disposal of this material. Due to the specificities of its products, civil construction has a large field where this waste can be used as raw material. The objective of this work is to contribute to studies on the possibilities of using sewage sludge as a way to improve the characteristics of the soil in collapse and as small concrete aggregates. Sewage sludge with 25, 50 and 75 mg/ha from the Mangueira and Curado treatment stations was used with an addition of about 5%, 10%, and 15%. In order to characterize the properties of sewage sludge and analyze its interaction with the soil and concrete specimens, several tests were carried out, such as: physical and chemical tests, scanning electron microscopy tests, hydraulic conductivity tests, chemical mobility tests, compressive strength tests, sclerometric tests, and ultrasonic pulse velocity tests. The results obtained allowed us to conclude that the addition of sewage sludge to the soil contributed to reduce its collapsibility, showing that this procedure can be useful for improve the performance of collapsible soils. It was also observed that when the proportion of sewage sludge was increased in substitution for small-size concrete aggregates, the compressive strength and water absorption decreased when compared to a concrete block made with usual aggregates. The behavior obtained indicates that the use of sewage sludge to replace the small-sized concrete aggregate part should be used with caution, even in small-sized buildings, requiring advanced studies to explore its use as a material building.