Use of Coal Bottom Ash and CaO-CaCl2-Activated GGBFS Binder in the Manufacturing of Artificial Fine Aggregates through Cold-Bonded Pelletization.

Dongho Jeon,Younghoon Bae,Seyoon Yoon,Jae Oh,Haemin Song,Woo Yum

doi:10.3390/ma13245598

Abstract

This study investigated the use of coal bottom ash (bottom ash) and CaO-CaCl2-activated ground granulated blast furnace slag (GGBFS) binder in the manufacturing of artificial fine aggregates using cold-bonded pelletization. Mixture samples were prepared with varying added contents of bottom ash of varying added contents of bottom ash relative to the weight of the cementless binder (= GGBFS + quicklime (CaO) + calcium chloride (CaCl2)). In the system, the added bottom ash was not simply an inert filler but was dissolved at an early stage. As the ionic concentrations of Ca and Si increased due to dissolved bottom ash, calcium silicate hydrate (C-S-H) formed both earlier and at higher levels, which increased the strength of the earlier stages. However, the added bottom ash did not affect the total quantities of main reaction products, C-S-H and hydrocalumite, in later phases (e.g., 28 days), but simply accelerated the binder reaction until it had occurred for 14 days. After considering both the mechanical strength and the pelletizing formability of all the mixtures, the proportion with 40 relative weight of bottom ash was selected for the manufacturing of pilot samples of aggregates. The produced fine aggregates had a water absorption rate of 9.83% and demonstrated a much smaller amount of heavy metal leaching than the raw bottom ash.

Highlights

Concrete is an artificial material that is widely used for building infrastructure in civil engineering [1] and it is estimated that around 30 billion tons of concrete are produced worldwide every year [2]
Indicates that the ash was that not entirely inertash in was not entirely inert in the binder reaction but selectively soluble depending on the type of element; that is, Ca, Si, and Mg were likely present in a dissolvable state, while Al was not
This study investigated the use of coal bottom ash and CaO-CaCl22-activated ground granulated blast furnace slag (GGBFS) binder in the manufacture of artificial fine aggregates using a cold-bonded pelletization technique

Summary

Introduction

Concrete is an artificial material that is widely used for building infrastructure in civil engineering [1] and it is estimated that around 30 billion tons of concrete are produced worldwide every year [2]. Concrete production requires large quantities of natural fine and coarse aggregates, as about 70% of the total volume of concrete is composed these of aggregates. Natural aggregates, such as river and sea sand, are constantly being excavated, which destroys the natural environment and depletes natural resources. Coal bottom ash (bottom ash) is an incombustible residue waste collected from coal-fired power plants [6]. In the Republic of Korea (South Korea), coal fly ash (fly ash), which is an industrial by-product of coal-fired power plants, has been sold as either a mineral admixture for concrete or Materials 2020, 13, 5598; doi:10.3390/ma13245598 www.mdpi.com/journal/materials

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Discussion

Conclusion