Could city sewage sludge be directly used into clay bricks for building construction? A comprehensive case study from Brazil

• Published in: Journal of Building Engineering 2020-09, Vol.31, p.101374, Article 101374
• Main Authors: Areias, I.O.R., Vieira, C.M.F., Colorado, H.A., Delaqua, G.C.G., Monteiro, S.N., Azevedo, A.R.G.
• Format: Article
• Language: English
• Subjects: Clay brick; Cost analysis; Environmental impact; Sewage sludge; Technical properties
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2020.101374

The sludge resulting from the treatment of city sewage is a growing and relevant environmental problem due to population increase and migration from rural to municipal areas. In the present work, it is shown that city sewage sludge can be directly added to clay bricks used in building construction. By means of Winkler and prognostic diagrams, it is for the first time revealed maximum addition to be 50 wt%. A firing temperature of 850 and 950 °C and up to 15 wt% of sewage sludge addition produce clay bricks without impact to the environment and that attend the standards for linear shrinkage, water absorption and mechanical strength. Moreover, the sewage sludge acts as a fuel during the sintering process and contributes with 40% of the firing energy. As a consequence, sewage added clay bricks might be fabricated with the lowest price associated with only 16% of the cost of a corresponding concrete brick and 20% of that of a common clay brick fired at higher temperatures. •The Winkler and prognostic diagrams that sewage sludge could be directly added up to a limit of 50 wt%.•The investigated firing temperature is enough to burn the organic matter in the sewage sludge and eliminate pathogenic.•The burning releases an amount of heat that contributes with about 40% saving in firing energy.•Fully processed bricks were obtained with inert and consolidated clay ceramic structure.•An addition of 15 wt% sludge was the maximum found to still produce clay bricks that attend the Brazilian standards.