Use of Sewage Sludge Ash in the Production of Innovative Bricks—An Example of a Circular Economy

Andelina Bubalo,Karlo Nad,Nina Stirmer,Drazen Vouk

doi:10.3390/su13169330

Andelina Bubalo, Karlo Nad + Show 2 more

Open Access

https://doi.org/10.3390/su13169330

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Journal: Sustainability	Publication Date: Aug 19, 2021
Citations: 14	License type: CC BY 4.0

Affiliation: University of Zagreb, Rudjer Boskovic Institute

Abstract

In this paper the properties of clay bricks with 5 wt%, 10 wt%, and 20 wt% sewage sludge ash (SSA) were studied and compared with the properties of control bricks made of 100% clay. Sewage sludge (SS) was collected at two wastewater treatment plants (WWTPs) in Croatia—WWTP Zagreb and WWTP Karlovac—and incinerated at a temperature of 900 °C The bricks were produced on a laboratory scale. A total of seven types of bricks were produced—control bricks and six types of bricks as combinations of different wt% of SSA generated from SS that was collected at two different WWTPs. The physical and mechanical properties of produced bricks were tested. Compressive strengths of bricks with 5 wt% SSA (54.0–54.5 N/mm2) and 10 wt% SSA (50.2–51.0 N/mm2) were higher compared to the control bricks (50.4 N/mm2), while bricks with 20 wt% SSA (37.0–43.9) N/mm2) had noticeably lower compressive strenght. The coefficient of saturation was lower for bricks with SSA compared to control bricks. The initial absorption values were more pronounced for SSA fractions of 20 wt%.

Highlights

The production of bricks from clay has a long tradition in the world and its growth is pronounced in developing countries
The trend of urbanization and industrial expansion is leading to an increase in demand for bricks, brick production in some countries has shown a negative trend in the last decade [1,2]
It can be seen that the sewage-sludge ash (SSA) brick specimens showed a slightly higher weight loss during firing compared to the control brick, especially for the

Summary

Introduction

The production of bricks from clay has a long tradition in the world and its growth is pronounced in developing countries. 1500 billion bricks are produced annually, 87% of which are produced in Asia [1]. Brick is one of the most commonly used building materials. The possibilities of using brick are wide, it is still mainly used for the construction of residential buildings [3]. Clay brick provides the properties of a good thermal insulator, fulfills the capacity of heat storage, and is characterized by the ability to self-regulate moisture as a result of high resistance to water vapor diffusion and by good sound insulation, high fire resistance, and long service life [3,4]

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