Sustainable Lightweight Concrete Designed with Modified Solidified Wastewater Sludge as Partial Replacement of Cement

Marina Škondrić (), Aleksandar Radević, Aleksandar Savić, Zorana Naunović, Željko Radovanović, Snežana Svetozarević and Vladana Rajaković-Ognjanović
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Marina Škondrić: Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia
Aleksandar Radević: Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia
Aleksandar Savić: Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia
Zorana Naunović: Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia
Željko Radovanović: Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia
Snežana Svetozarević: Department of Psychology, Faculty of Philosophy, University of Belgrade, 18-20 Čika Ljubina Street, 11000 Belgrade, Serbia
Vladana Rajaković-Ognjanović: Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia

Sustainability, 2025, vol. 17, issue 3, 1-25

Abstract: The requirement for high-quality drinking water and the treatment of wastewater prior to discharge into the environment results in the generation of sludge. As with any high-volume materials, beneficial reuse applications are being sought to promote sustainable environmental solutions. This research examined the possibilities of producing sustainable lightweight concrete using modified solidified wastewater sludge as a partial replacement of cement. Wastewater sludge was modified by the addition of aluminum oxide and magnesium silicate hydrate. The properties of the modified wastewater sludge were examined, as well as the influence of the partial cement replacement with the sludge in lightweight concrete. Besides testing the physical and mechanical properties of four mortar mixtures, an additional analysis of the willingness of final users to accept novel material containing wastewater sludge was addressed. The results obtained for the mortar samples indicate that 20% cement replacement is the upper limit for the modified sludge’s application. The lightweight concrete prepared with the modified sludge (in the amount of 20%) was tested in a hardened state. The water permeability was reduced by 33.3% with the addition of the modified sludge. Both tested concrete mixtures showed good frost resistance. The maximal measured reduction in the compressive strengths was 7.6%. Citizens’ perceptions and responses regarding the beneficial reuse of materials emphasize the importance of comprehensive education for their future acceptance.

Keywords: cement replacement; lightweight concrete; solid waste management; wastewater sludge; sustainable solutions for cement-based composites; human factor in sustainable solutions (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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