Self-Immobilizing Metals Binder for Construction Made of Activated Metallurgical Slag, Slag from Lignite Coal Combustion and Ash from Biomass Combustion.

Barbara Słomka-Słupik

doi:10.3390/ma14113101

Abstract

Research on the effective use of secondary products is gaining more and more importance in Poland due to the intensively implementing idea of the circular economy. The solution used in this work are one of many tests useful in construction. The subject of this work was therefore the formation and testing of a new ecological construction binder, in particular for mortars or prefabricated elements working in the environment with high humidity. The binder was made of alkaline activated ground granular blast furnace slag (AAS), fly ash from biomass combustion (BFA) and furnace slag from brown coal combustion (LFS). The mixture was modified by introducing the zeolite to check the degree of metals immobilization contained in the ingredients of the mixture. A series of three mixtures were prepared: without and with zeolite soaked in distilled water or calcium nitrate. The strength of binders in time in dry and wet curing were tested and compared with the microstructure. The maximum compressive strength values at the eighth week were about 30 MPa. The strength values after 4 weeks of dry and wet curing were also compared. It was shown that 28-day wet curing increased the bending strength of the beams more than twice, but slightly decreased the compressive strength. The microstructure of the mixture with the highest values of compressive strength was the densest and the one with the lowest values of compressive strength, the most loosened with the most differentiated topographically fracture. The impregnation of zeolite with calcium nitrate decreased the compressive strength of the binder significantly. The bending strength of samples curing in dry conditions decreased during hardening. The results of the metals leaching test showed that the mixtures were safe for the environment, and due to the impregnation of zeolite with calcium nitrate, the binding effect of copper and zinc in the first weeks was greater than in the other mixtures.

Highlights

In the present state of knowledge, construction mortars or concretes in the form of a mixture with at least one inorganic binder, aggregate, water, additives and admixtures are commonly used
Ground granulated blast furnace slag (GGBFS) by Górazdze Cement S.A. (Chorula, Poland), which came from the Ekocem production plant (Dabrowa Górnicza, Poland), met the standard requirements according to PN-EN 15167-1 [59]
Presented experimental study investigated selected properties of the binder that can be used in construction, made of activated metallurgical slag, slag from lignite coal combustion and ash from biomass combustion

Summary

Introduction

In the present state of knowledge, construction mortars or concretes in the form of a mixture with at least one inorganic binder, aggregate, water, additives and admixtures are commonly used. The group of construction binders includes lime, gypsum, geopolymer and cement binders, but the main application is still cement. The production of cement, in turn, is associated with enormous CO2 emissions. Cement plants can cope with its reduction in many ways, the current situation on the cement market in Poland seems to be unregulated in terms of the possibility of reducing CO2 emissions [1]. The research in the field of building materials is currently focused on assumptions of the circular economy (in Pol.: GOZ). Solutions are sought that allow one to obtain a material made of secondary products, mainly after high-temperature processes. These are so-called combustion byproducts (in Pol.: UPS). Is the general characteristics of combustion by-products as cement components

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