Properties of Inorganic Polymers Produced from Brick Waste and Metallurgical Slag

Soultana Soultana,Bartzas Bartzas,Komnitsas Komnitsas,Valouma Valouma

doi:10.3390/min9090551

Soultana Soultana, Bartzas Bartzas + Show 2 more

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https://doi.org/10.3390/min9090551

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Abstract

This paper explores the alkali activation potential of brick wastes and metallurgical slags. Inorganic polymers (IPs) were produced using an alkaline medium consisting of sodium hydroxide and sodium silicate solutions and the optimum synthesis conditions were determined. In this context, the variable parameters, such as solid to liquid (S/L) ratio, curing temperature (60, 80 and 90 °C) and ageing time (7 and 28 days) on the compressive strength and the morphology of the produced IPs were investigated. Specimens produced under the optimum synthesis conditions were subjected to high temperature firing and immersed in distilled water and acidic solutions for various periods of time, in order to assess their durability and structural integrity. The results showed that the IPs produced using a mix ratio of 50 wt % metallurgical slag and 50 wt % brick wastes, cured at 90 °C and aged for 7 days obtained the highest compressive strength (48.9 MPa). X-ray fluorescence analysis (XRF), particle size analysis, Fourier transform infrared spectroscopy (FTIR), mineralogical analysis (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis also confirmed the optimum microstructural characteristics and the chemical reactions that took place during synthesis. The overall results of this study indicate that the co-valorization of different waste streams, which are produced in large quantities and cause environmental problems if not properly managed, is a viable alternative for the production of binders or secondary construction materials with higher added value.

Highlights

Construction and demolition wastes (CDWs) comprise the largest waste fraction in industrialized countries
The compressive strength of the Inorganic polymers (IPs) produced from brick waste (B) as a function of H2 O/Na2 O
It can be seen that, as the H2 O/Na2 O molar ratio increases from 15.5 to 18.1; the compressive strength of specimens cured at high temperature (80 and 90 ◦ C) increases whereas, the same increase in H2 O/Na2 O molar ratio, resulted in lower compressive strength for specimens cured at the lower temperature (60 ◦ C)

Summary

Introduction

Construction and demolition wastes (CDWs) comprise the largest waste fraction in industrialized countries. They represent one third of the total waste volume generated by industrial activities, which in the EU-28 is about 3 billion tons per year [1]. CDWs derive from construction and demolition activities and mainly contain concrete, masonry, asphalt and metals [2]. 54% of CDW is comprised of ceramic materials (i.e., bricks and tiles), while approximately 12% is concrete [3]. Their disposal requires large areas and often causes severe impacts to the environment [1,4]. The production of 1 ton of cement results in emissions of approximately

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