THE POSSIBILITIES OF USE COAL GANGUES AS AN ADDITIVE TO GEOPOLYMER CONCRETES

Michał Łach1*

, Kinga Korniejenko1, Tomasz Ronczoszek

2, Norbert Komar

3, Janusz Mikuła

1

1Faculty of Materials Engineering and Physics, Cracow University of Technology, Poland 2Ronenberger LTD., Tarnowskie Góry, 42-605

3Ekologia Przedsiębiorczość Innowacje, 17 Kuhna Av., 42-256 Olsztyn

* Corresponding author: e-mail: michal.lach@pk.edu.pl

Acknowledgment

1. This work has been supported by Intelligent Development Operational Program

2014-2020, 1.1.1: Industrial research and development works carried out by enterpris-

es, funded by the National Centre for Research and Development in Poland, within

the framework of the grant: ‘Development of coal gangue recovery technology for

the simultaneous production of metakaolin and road-building aggregates with addi-

tional energy recovery’ (‘Opracowanie technologii odzysku łupków przywęglowych

do jednoczesnej produkcji metakaolinu i kruszyw drogowo-budowlanych z dodat-

kowym odzyskiem energii’), grant no. POIR 01.01.01-00-0009/17-00.

Acknowledgment

2. This work has been supported by the ERANet-

LAC 2nd Joint Call (http://www.eranet-lac.eu)

funded by the National Centre for Research and

Development in Poland, within the framework of

the grant: ‘Development of eco-friendly compo-

site materials based on geopolymer matrix and re-

inforced with waste fibers’.

References

1. Huang G., Ji Y., Li J., Hou Z., Dong Z., 2018, Improving strength of calcinated coal gangue geopolymer mortars via increasing calcium content, Construction and Building Materials, vol. 166, p. 760–768.

2. Li C., Wanb J., Suna H., Li L., 2010, Investigation on the activation of coal gangue by a new compound method, Journal of Hazardous Materials, vol. 179, p. 515–520.

3. Sedira N., Castro-Gomes J., Kastiukas G., Zhou X., Vargas A., 2017, A Review on Mineral Waste for Chemical-Activated Binders: Mineralogical and Chemical Characteristics, Mining Science, vol. 24, p. 29−58.

Introduction

The main components of waste gangue associated with coal mining are illite, quartz and kaolinite, which contain a

large amount of silicon oxide and aluminum oxide. Their chemical composition makes it potentially a good raw

material in the process of alkaline activation [2, 3]. However, to ensure adequate reactivity in the alkaline activation

process, this raw material requires initial preparation in a mechanical and thermal process [2]. It is possible to use

only one of these processes to activate the material, however, optimal properties are obtained by means of mechani-

cal activation - grinding (fine particles show higher reactivity) and thermal activation in the calcination process [2].

It should also be noted that the best material properties are obtained on the basis of gangue, which contains a high

content of amorphous aluminosilicate [3]. The content of reactive components, in particular active silicon and alu-

minum, is important very important in geopolymer synthesis [1].

Wt% TiO2 SiO2 Al2O3 Fe2O3 CaO MgO MnO SrO BaO Na2O K2O P2O5 SO3 ZrO2

K4 1,11 65,77 21,44 4,22 0,33 1,26 0,05 0,01 0,07 0,73 3,93 0,22 0,07 0,09

K5 0,88 56,84 27,37 4,96 1,31 1,80 0,07 0,02 0,06 1,21 3,67 0,13 0,34 0,04

Research methods

Samples for testing were taken from two Polish hard coal

mines: Piast [K4] and Ruch Rydułtowy [K5]. The material was

first crushed in a jaw crusher and then milled in a ZM200

RETSCH ultra centrifugal mill (0.040 mm sieve). The material

thus prepared was subject to calcination in chamotte furnaces

at a temperature of 750°C.

XRD analyses were performed with a Rigaku SmartLab X-ray

diffractometer with the following parameters: CuKα radiation,

reflective graphite monochromator, lamp voltage 45 kV, lamp

current 200 A, step: 0.05°2θ, counting time per step = 1 s. The

values of lattice parameters obtained have been used for the

phase identification of samples under analysis. For this pur-

pose, the data from the ICDD (International Centre

for Diffraction Data 2016) catalogue and XRAYAN computer

program were utilized.

The topography of the particle surfaces and the chemical mi-

croanalysis were performed with a JEOL JSM-820 scanning

electron microscope equipped with an EDS system. Before

SEM examination, the samples were covered by a thin gold

layer by sputter coater JEOL JEE-4X.

Fig. 2. X-Ray diffraction patterns of samples K4

Results

Figure 1 shows an example of the appearance of coal shales in the form of rocks.

Figures 2 and 3 show the results of XRD analyses for carbonaceous shales collected,

respectively, from the deposit of coal mines KWK Piast and Ruch Rydułtowy. Figures

4 and 5shows the morphology of calcinated wastes from the coal mines.

Table 1 presents the oxide composition of the investigated coal shale.

Fig. 3 X-Ray diffraction patterns of samples K5

Fig. 4. SEM of samples K4 Fig. 5. SEM of samples K5

Fig. 1. Example of coal gangue

Table 1. Oxide composition of samples

Conclusions

Materials that have been tested due to a high SiO2 content exceeding

55% and a high content of Al2O3 exceeding 20% are an interesting ma-

terial for the synthesis of geopolymers. The XRD tests carried out sho-

wed the presence of kaolinite which during the calcination process

transforms into an amorphous phase desired for the production of geo-

polime. The process of their reprocessing and utilization fits into the

following rules subject to intensive development, viz.: zero waste eco-

nomy (Zero Waste Europe), effective use of resources (Resource Effi-

cient Europe) as well as closed-circuit economy (Circular Economy).