Sewage sludge ash (SSA) in high performance concrete: characterization and application

C M A Fontes,R D Toledo Filho,M C Barbosa

doi:10.1590/s1983-41952016000600009

Abstract

ABSTRACT Sewage sludge originated from the process of treatment of wastewater has become an environmental issue for three main reasons: contains pathogens, heavy metals and organic compounds that are harmful to the environmental and human health; high volumes are daily generated; and shortage of landfill sites for proper disposal. This research deals with the viability study of sewage sludge utilization, after calcination process, as mineral admixture in the production of concrete. High-performance concretes were produced with replacement content of 5% and 10% by weight of Portland cement with sewage sludge ash (SSA). The influence of this ash was analyzed through physical and mechanical tests. Analysis showed that the mixtures containing SSA have lower values of compressive strength than the reference. The results of absorptivity, porosity and accelerated penetration of chloride ions, presents that mixtures containing ash showed reductions compared to the reference. This indicates that SSA provided refinement of the pore structure, which was confirmed by mercury intrusion porosimetry test.

Highlights

Sewage sludge is the solid part generated during the treatment of the liquid phase of domestic sewage
Sewage sludge originated from the process of treatment of wastewater has become an environmental issue for three main reasons: contains pathogens, heavy metals and organic compounds that are harmful to the environmental and human health; high volumes are daily generated; and shortage of landfill sites for proper disposal
Borges et al [4] obtained a calorific value of 20MJ/kg for sewage sludge, which is in the same order of magnitude as the eucalyptus wood briquette (19,5MJ/kg) [5] and sugarcane bagasse (19MJ/kg), residues widely used in boilers as alternative sources of renewable energy

Summary

Introduction

Sewage sludge is the solid part generated during the treatment of the liquid phase of domestic sewage. Borges et al [4] obtained a calorific value of 20MJ/kg for sewage sludge, which is in the same order of magnitude as the eucalyptus wood briquette (19,5MJ/kg) [5] and sugarcane bagasse (19MJ/kg), residues widely used in boilers as alternative sources of renewable energy This type of process generates ashes that, dependingon the residue source, contain heavy metals and organic compounds in its composition, as in the case of calcined sewage sludge. Other studies have been carried out with this type of ash, and with that new materials have been produced and evaluated for their physical and mechanical behavior, including: lightweight and fine aggregates [15, 16, 17, 18, 19, 20], ceramics [21, 22 and 23] and concrete blocks [11] Within this context, this paper aims at the utilization of the sewage sludge after the calcination process, as a partial replacement for Portland cement in concentrations of 5% and 10%, by weight, in the production of high performance concrete. Given the fact that SSA contains heavy metals in its composition even after the burning process, a dense microstructure turns more difficult for those compounds to solubilize into the environment [8]

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Conclusion