Materials From Hazardous Iron Ore Treatment Waste, Concrete Demolition Debris And Lime Production Waste to Increase Environmental Sustainability of Industrial Regions

To prevent environment pollution by hazardous industrial dumps of iron ore treatment sludge, concrete production/demolition debris and lime production waste sustainable cement-less construction materials were developed for substitution of traditional natural raw components excavated in careers, irreversibly destroying natural bonds. Their axial resistance values on the 3 rd day of hydration were till 2.34 MPa, on the 28 th day - up to 3.94 MPa, on the 180 th day 8.40 MPa and on the 365 th day 10.22 MPa. The expanding coecient on the 3 rd day were till 2.13%, 2.51% on the 28 th day, and on the 365 th day 2.22%. Water absorption on the 28 th day was 7.17 - 9.32% and decreases to 6.26 - 8.64% on the 90 th day. All these characteristics correspond to the Brazilian norms. The physical - chemical processes of materials’ structures formation included alkaline dissociation of solid particles’ surface, with sol appearing and densication till transition to gel. Long-lasting gel compaction and densication to stone-like condition made its structure similar to natural rock materials - silica, opal, obsidian, perlite, pumice, amber, ask, etc. They can be used for production of road bases, concrete blocks and solid unburned bricks, among other sustainable construction materials.


Introduction
Industrial and municipal waste in solid, liquid and gaseous forms are the main environmental pollutants of our planet. The constant rise in atmospheric temperature caused by them calls into question the survival ability of future generations of people. According to the authors of this study, the only way to overcome this dangerous trend is to develop methods for the disposal of all types of waste as valuable raw materials and to apply them at an industrial level with a remarkably high environmental and economic e ciency.
The results of this experimental study convincingly prove the possibility of environmentally friendly building materials' producing from such most widely spread industrial waste as iron ore treatment waste (IOT), concrete production and demolition debris (CDD) and lime production wastes (LPW) instead of more costly traditional natural components of building materials -sand, clay, crushed stone, rock gravel and others. Therefore, between the years 2000 and 2017 there were 36 cases of IOT tailings dams' failures in the world, an average of two per year, which caused signi cant environmental damage (Wise Uranium (2015). Two major irreparable disasters occurred in 2015 in Brazil (Mariana), in which 50 million cubic meters of IOT leaked and reached the Atlantic Ocean; the second one was in Brumadinho (2020) that poured 13 million cubic meters (Freitas, et al, 2019). One of the best ways to avoid similar harmful damages is to apply IOT as a principal valuable by-product for civil construction material and to decrease its accumulation in the dumps. Galvão et al (2018) offering it as a sustainable reddish paint for construction pigment; for mortars and laying bricks production (Fontes. et al, 2016); for Portland cement clinker (Luo, et al, 2016;Yao, et al, 2020); to improve resistance to sulfates attacks (Xiong, et al, 2017); as replacement for ne aggregate in concrete (Shettima, et al, 2016).
Concrete production and demolition (CDD) debris is a waste of all types of technological processes associated with the production and destruction of building concrete. The amount of its production in different countries is estimated differently and depends mainly on the life standard of the society. For example, in the European Union (2018) it reached 46% in 2018 of the total amount of waste (Akhtar and Sarmah, 2018) and much less in developing countries (Huanga, et al, 2018). Zhang, et al (2017) informed that annual CDD production in China is about 3 billion tons. Typical components in the CW are inert materials, such as concretes with almost 90% of natural rocks, mortars, and ceramics, slate, glass, which have proven to be a substitute for natural aggregates (Fatemi and Imaninasab, 2016). According to Brazilian norm NBR 15116 (2004), at least 90% of CDD mass are fragments of natural rocks. Therefore, Silva, de Brito and Dhir (2014) studied properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production. Xuan, Sun and Zheng (2018) applied CDD non-structural concrete artifacts and for cement production (Robalo, et al, (2021); in composites with y ash, dust from cement kilns and gray water (Bassani, 2019).
Large amount of lime production waste (LPW) is formed mainly due to two reasons: when calcining carbonate rocks occurred below 960°C or during long-term storage of lime with access of humid air. Brazilian norms NBR 6453 (2003) allow a maximum of 12% of total CO 2 content with chemical impurities like Fe 2 O 3 , Al 2 O 3 , SiO 2 . Otherwise, this material is called lime production waste (LPW) and cannot be marketed and used as construction lime.
Usually, LPW is used for sanitary purposes of municipal sewage sludge treatment, to create an alkaline environment for various technological processes, like activator of chemical slag-soil interaction of road base construction in Kazakhstan (Mymrin, et al, 2019). Pedroso (2019) cement-less concrete from three types of industrial wastes: of cellulose production, concrete demolition (CDD) and lime production. LPW can be used in composites with two different types of spent sun ower cooking oils and brick waste powder as pozzolanic addition of new lime mortars (Pahlavan, et al, 2017) or glass mortars (Yang, Poon, Ling, 2019); to produce cementless controlled low-strength material based on waste glass powder (Xiao, et al, 2021); for soil stabilization based on recycled-glass powder waste and dolomitic lime (Baldovino, et al, 2021); for preparation of geopolymer (El-Naggar, et al, 2019); as amendment of municipal sewage sludge with lime and mussel shell (Wang, et al, 2019) or for production of lime-incineration sewage sludge ash pastes (Zhou, et al, 2021); for cementless controlled low-strength material based on waste glass powder (Xiao, et al, 2021). LPW was used also Karanac, et al (2018) y ash as a low-cost adsorbent of Zn 2+ , Pb 2+ , and As +5 ions.
Objectives of the study A study of the available world scienti c research literature, some of them are mentioned above, showed that there is no information on the development of building materials, produced from iron ore treatment waste, concrete production / demolition debris and lime production waste. The production of building materials is the largest consumer of natural resources, a signi cant part of which can be replaced by industrial and municipal waste with remarkably high environmental and economic e ciency. The recent ecological disasters in brazilian history forced the development of as many compositions of building materials as possible with the largest content of these and other waste. The solution to this problem is the main goal of this study. Elucidation of the physicochemical processes of the developed building materials' structure formation was an equally important goal since their structures explain all the properties and reliability of materials during their operation.

Raw materials and Test Samples (TSs) preparation
Two raw materials under study -concrete waste (CW) and lime production waste (LPW) were collected from the dumps of in the metropolitan region of Curitiba, Brazil enterprises. The iron ore waste (IOW) was collected after the Fundão burst in 2015 in Mariana, Minas Gerais, Brazil.
The dry mix of components was manually homogenized, hydrated to 15-17%, sealed in a manual Bovenau hydraulic press, in a cylindrical format with a height and diameter of 20 mm at a force of 5 MPa for 30 seconds, and stored in outdoor condition for various test periods; 60 TSs were made for each of the 16 compositions with total quantity near 1,000 samples. The TSs' properties were carried out by averaging ve measurements with the calculation of standard deviation values.

Methods
To investigate mechanical and physical properties the following tests were carried out: resistance to axial compression, water resistance, water absorption, expansion and shrinkage. The leaching and solubility tests were carried out for IOT sludge as the most polluted raw component and for composition 12 with the biggest (60%) IOT content on the 90th curing day. To study the raw materials and the developed composites' physicochemical processes of structure's formation, the following methods were applied: the particle size distribution was performed by a Bettersizer S3 Plus laser diffraction analyzer, in combination with sew method; chemical composition of the raw materials by X-ray uorescence analysis (XRF); mineral composition by X-ray diffraction (XRD) with automated database of minerals PDF-2; the chemical composition of new formations -by the method of energy-spectrum spectroscopy (EDS) and isotope composition by laser micro-mass analysis (LAMMA); morphological structure of the samples -by scanning electron microscopy (SEM); solubility and leaching of metals -by atomic absorption analysis (AAA).

Calculations
The water resistance coe cient (C WR ) was determined based on the ratio: where R SAT is the axial compressive strength of saturated TSs after total immersion in water for 24 hours; and R D is the axial compressive strength of the specimen oven-dried at 100°C for 24 hours.
Water absorption values were calculated in accordance with the equation: Where, WA -the absorption of water by the test sample (%), Ms -mass of the sample after drying in oven at a temperature of 110 ° C for 24 hours (g) Mh -mass of the humid test sample after immersion in water at room temperature for 24 hours (g)

Research's Results
The research's results are presented in the following three sections: 3.1. Characterization of the initial components; 3.2. Mechanical and physical properties of the developed materials; 3.3. Physicochemical processes of its structure's formation explaining the reasons of these properties obtaining.

Raw materials characterization
All raw materials were characterized on particle size distribution, chemical and mineral compositions and structures' micro morphology.
3.1.1. Particles' sizes distribution of the raw materials Comparison of the particles' sizes distribution of the raw materials (Table 1) demonstrates that the particles thicker than 9.50 mm are in CDD (8.53 %) with total amount of particles between 2.00-and 9.50mm sizes 84.75%, followed by IOT (75.50%). IOT contains slightly larger particles having less than 2.00 mm -18.0% than RC -12.1%. The majority (64.87%) of the LPW particles by laser diffraction analyzer have particle sizes between 0.010 and 0.028 mm and only 0.36% by weight particles have sizes greater than 2 mm. Therefore, the nest in terms of particle size distribution can be considered LPW, and the biggest -CDD.

Chemical composition of the raw materials
The chemical composition of the raw materials ( Concrete waste CDD contains an even larger amount of SiO 2 -49.1% and CaO = 22.5% than IOT, due to the large amount of the main binding minerals of Portland cement calcium silicates (alite 3CaO·SiO 2 , belite 2CaO·SiO 2 ) and calcium aluminum-ferrite 4CaO·Al 2 O 3 ·Fe 2 O 3 , as well as rocks as concrete ller.
High C.L. = 10.60% of CDD can be explained by dissociation of carbonates and hydrates of concrete during calcination with a temperature of 1,000°C.

Mineral composition of the raw materials by XRD method
The study of the mineral composition of the initial components by XRD method showed that IOT (Fig. 1a Mineral composition of concrete waste (Fig. 1b) is presented by calcite CaCO 3 , albite Na (AlSi 3 O 8 ) and quartz SiO 2 with the highest scale Icps value until almost 800 cps. But the highest crystallin peak intensity at the angle 2Θ°=26.8° is presented by the overlap sum of calcite and quartz content diffractions. All others crystalline peaks of albite and quartz are rather low, but they are higher, than the peaks of IOW (Fig. 1a).
XRD of lime production waste ( (Table 2), but lime as mineral is presented by the only independent small peak at 2Θ°= 37.6°. Part of the lime can enter the amorphous phase of the sample, as well as part of amorphous and crystalline carbonates, but this information serves as irrefutable proof that this material will not serve as a commercial construction lime, but only as a lime production waste (NBR 6453, 2003).

Microstructure of the raw materials (by SEM method)
Micromorphology of the raw materials studied by the SEM method ( Fig. 2) presents particles of different sizes and shapes, without physical and chemical connections between them. These shapes can be seen as rounded, oval, angular, laminar, needles, among others.
There is a large number of different sizes and shapes pores between the particles. Almost all particles have a rounded surface explained by the hydration during storage. IOW was formed (Fig. 2a) in the conditions of excessive water amount and long-term storage as sludge in industrial dumps, therefore, all edges and corners of its particles have a characteristic drip-like appearance; the concrete waste ( Fig. 2b) was formed after hydration of the concrete mixture; and lime production waste (Fig. 2c)   The standard deviation values of the axial strength from the obtained experimental data never exceeded 5% of the average means.

Expansion of the developed materials during curing
Linear expansion of all developed materials (Table 4)   Composition 13 showed the highest shrinkage values at all curing days, followed by composites 14, 9 and 10. This variance in results can be justi ed by the high content (till 70% in composite 9) of total amount of LPW and CDD with priority in uence of LPW. Conversely, the lowest meaning of the expansion belongs to the composition 4, followed by composition 3 and 1, which has also the lowest resistance values on the 365th day (Table 2). These results con rm the idea of the relationship between the size variation and resistance of the test samples during physical and chemical processes of materials hydration. IOT in these composites plays the role of a passive ller. The standard deviation values of the experimental data obtained were varied between 0.02 -0.04%.

Apparent density of the developed materials during curing
The molding of the tested samples was through a compacting process, and this feature aims to improve the properties of the composite by reducing its voids by applying a pressing on the area, resulting in an increase in speci c mass apparent. Results of apparent speci c mass measuring and calculation (Table 4)    absorption; a minimum varying from 6.07 to 5.56% was measured in composition 4, respectively at the 28th and 90th day.
The standard deviation values of water absorption coe cient values never exceeded 0.07%.

STRUCTURE FORMATION PROCESSES OF THE DEVELOPED COMPOSITES
To study the physical-chemical processes of the developed materials' structures formation, composition After hydration and open-air curing in the diffractogram (Figure 3b) the peaks of portlandite disappear turning into calcite (CaCO 3 ). The intensities of calcite peaks increased at almost all angles, particularly the peak at angle 2Θ° = 29.5° grows from I = ± 1,200 to ± 1,500 cps due to the carbonization process of lime production waste and to the increase of calcite (CaCO 3 ) The process of all materials strengthening continues up to 365 days at a slow speed (Table 3). In Figure  3c, the visible increase in intensities of crystalline peaks of quartz and calcite. The largest of these quartz peaks at an angle of 2Θ ° = 26.5 ° increase their intensity from value I = ± 2,800 cps to the level of ± 3,000 cps. The calcite peak with angle 2Θ ° = 29.5 ° grows slightly slower in this time frame than during the rst 180 days -from ± 1500 cps to ± 1,700 cps.
A very high background of all three diffractograms is also well visible in Figure 3, which means a high content of amorphous materials. They were partially inherited from the initial amorphous components ( Figure 1), but a signi cant part was formed during the alkaline dissociation of all particles in the initial mixture, including that of quartz particles.

Changing composition 12 samples micro morphology during hydration and cure
The process of the micro morphological structure changing of the composition 12 samples during hydration and cure was studied using the SEM method ( Figure 4). The compacted dry sample of composition 12 (Figure 4a) is represented by particles of various con gurations -round, oval, angular, needles, curved lamellar, among others. The particles with the size 1 -200 µm are not linked together; the pores between them also have different sizes and shapes.
After 180 hydration days all particles are covered (Figure 4b and c) with a layer of gel-like material, sticking all particles together, which was not found in the original dry mix (Figure 4a). Under this layer, one can nd the con gurations of the initial particles. The number of pores has been drastically reduced, and their shapes have become smooth and rounded on all sides. The pore's sizes also drastically decreased and vary between 1 and 10 µm. This transition of dispersed and unconnected particles (Figure 4a) for their uni cation in monolithic structures (Figures 4-b, c, d and e) with density increasing (Table 5), simultaneous decreasing of water absorption values (Table 6) of these new formations' layers explains the increase in the resistance of materials (Table 3) in the forming these bonds.
The microstructure of the test samples at some points with bigger magni cation (Figure 4c and f) is signi cantly different due to the impossibility of obtaining equal homogeneity at the micro level of the initial components' mixes. They also clearly show the process of gathering and combining particles in small akes and short crystal-like new formations' needles over more monolithic areas, which leads to an increase in the resistance of the samples.
Much more of these crystal-like new needles and their druses appeared in the samples after 365 days of hydration (Figure 4f), which increased their resistance as well.
But the number of such points is relatively small and the overwhelming number of structural morphologies of the samples is characterized by the test samples' structure in Figures 4d and especially 4e -completely at, without any resemblance to the existence of individual initial particles and with a very limited number of small pores in gel-like amorphous structures of new formations.
The sol-gel transition was observed in this study for 365 days, but it can continue for 7 or more years Mymrin, et al (2019), especially in conditions of su cient humidity which causes long-term hardening and changes in other mechanical, physical and chemical properties of the developed materials.

Microchemical composition of new formations 12
The results of the chemical composition obtained in Figure 4d, e and f using the energy dispersion spectroscopy (EDS) method, are presented in Table 7. They demonstrate that new formations in the  (Table 2), with 20% of CDD contain in the composition 12 (Table 3). Therefore, the ettringite synthesis in the initial mix with such a small amount of SO 3 was practically excluded or at least could not be xed in our study due to the low sensitivity of the XRD method (about 5%).   (Fig. 6). The set of isotopes and their intensity at each of the new formations was signi cantly different from each other, also detected by the EDS method ( Table 7).
As the most sensitive analytical method, LAMMA helped to detect the presence of not only Cu (Table 2), but also the presence of other heavy metal isotopes (Cr, and Zn) in most of the points of new formations (Fig. 6).

Sustainability of developed composites
Environmental properties of the developed materials were studied by atom absorption spectroscopy (AAS) methods after samples' leaching and solubility in acid environment (NBR 10,004 -2014). The e ciency of the heavy metals' chemical binding was veri ed by comparing the AAS results of the initial IOT as more polluted raw material ( Figure 5 and Table 2) and composition 12 with a maximum 60% IOT content.
The hazardous IOT leaching study (  3. It can be argued that the structure formation process of the new developed composites consists of two mutually complementary effects: a. The effect of alkaline dissociation on the surface of solid particles with synthesis of new amorphous sol-gel formations (also known as "solid solutions"), gradually transforming into a rock-like state, like a large amount of well-known natural materials -silica, opal, obsidian, perlite, pumice, amber, ask, etc.
b. The effect of the synthesis of carbonates, especially calcite with possibly low crystalline and amorphous dolomite content, is clearly visible. Both types of new formations (amorphous and crystalline), as in nature, are mixtures of varying degrees of homogeneity both initially dissolved components and of the products of their interaction in the porous space.
The study of the physical -chemical processes of structures formation with these properties by the methods of X-rays diffraction, scanning electron microscopy, micro chemical composition through the method of energy dispersion system, of the chemical elements' distribution by mapping method and isotope content of metals by LAMMA method in the surface layer of new formations, allowed to establish the implementation of the following processes: chemical corrosion of the solid particles' surfaces of the initial components in an alkaline solution of hydrated lime production residue; chemical interaction of these solutions of the initial components with the formation of sol solutions of various chemical compositions; the densi cation of these solid solutions with their transition to a gel; the synthesis of calcite crystals in pore space; the transition of the gel during a year of hydration in the stone-like state.
These processes explain the change in all mechanical and physical properties of the materials developed throughout the year.
4. It was found that iron ore treatment waste contains signi cant amounts of metals, including hazardous heavy metals (Zn, Ni, Ba, Cd, Pb, Sn, Hg, Se, Cr) in quantities above brazilian sanitary norms.
The study of the ecological properties of the developed materials by standard methods of solubility and leaching in an acid medium demonstrated the ow of sol-gel bonding process with the synthesis of new formations up to the level that satis es the sanitary norms. Therefore, the greatest bene t from the application of the results obtained is the environment, considering the real possibility of using industrial waste as raw material, applying an appropriate nal destination, preventing possible contamination of the environment and reducing the extraction of natural resources. Figure 1 XRD patterns of the raw materials: a -iron ore treatment waste, b -concrete production and demolition debris and c -lime production wastes.

Figure 2
Microstructure morphology of the raw materials: a -iron ore treatment waste, b -concrete production and demolition debris and c -lime production wastes.
Page 26/29   Main chemical elements distribution in new formations of the composition 12 by mapping method.

Figure 6
Isotopes' composites at different points of the composition 12 sample after hydration and curing for 90 days.