Materials Today: Proceedings
Synthesis and mechanical characterization of geopolymeric mortars derived from inorganic industrial waste from Peruvian informal mining
Introduction
Geopolymeric materials are compounds of inorganic nature obtained by chemical processes of geopolymerization of aluminosilicates, such as: burnt clays, industrial waste, among others, and an alkaline compound in aqueous solution, typically sodium hydroxide [1], [2], [3], [4]. Recently, the international scientific community has shown a growing interest in the study of this type of materials, mainly due to the breadth of applications in which they can be used, this in turn, due to their low density, resistance to fire, and relatively low cost. , simple manufacturing, chemical stability and friendly synthesis with the environment [5]. Therefore, geopolymers are considered revolutionary materials with high potential as substitutes for Portland cement [3], [13]. Several works have been reported in the literature where the methodology for obtaining geopolymeric concretes with up to 70% compressive strength in the first 4 h of hardening is presented [6], unlike its Portland cement counterpart, which as is well known, it takes several weeks. On the other hand, studies related to the drying contraction of geopolymeric concretes revealed that after a year of being manufactured, they presented between 5 and 7 times less contraction, compared to their Portland cement counterparts [7], [8]. Other studies have evaluated the strength of geopolymeric concretes at relatively high temperatures and its comparison with their Portland cement counterparts. For example, Kong et al. [9] evaluated the compressive strength of geopolymer and Portland cement pastes, after being treated at high temperatures, found that at 800° C geopolymers improve their mechanical response, while at 400° C, cement pastes Portland lose all their stamina. It should also be remembered that during the obtaining of Clinker (main component of Portland cement) high CO2 emissions are generated, thus, it has been determined that for each ton of Portland cement manufactured, up to one ton of CO2 can be generated [10].
Finally, one of the most urgent environmental problems to solve in Peru is the large amounts of inorganic mining waste that are generated every year and today only accumulate in gigantic tailings fields [11], [12]. Due to all the above, in this work various mixtures of geopolymeric mortars derived from mining tailings and controlled quantities of fine sand were studied for their potential use as an alternative construction material to Portland cement mortar.
Section snippets
Starting materials and synthesis of the mortars
The starting materials for the fabrication of the control (C) and geopolymeric (G) mortars were:
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Binder: cement type I (for C) and inorganic waste from the informal mining industry (for G), sampled from an abandoned Peruvian informal mining tailings pit, located at UTM coordinates WGS 84, East 577668.00/North 8249624.00
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aggregates: fine sand sieved by ASTM # 100 mesh (150 µm),
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activating liquid phase: potable water (for C) and Na(OH) solution (for G).
Table 1 lists the mixtures studied in this
Phases and morphology of the raw material
From X-ray diffraction studies, the presence of the following crystalline phases in the binder raw material (mining tailings) could be identified: Quartz (SiO2), Albite (NaAlSi3O8), Calcite (CaCO3), Muscovite (K0.77Al1.93(Al0.5Si3.5)O10(OH)2) and Clinochlore ((Mg,Fe)6(Si,Al)4O10(OH)8). Fig. 1 presents the X-ray diffraction spectrum together with the identified peaks.
Fig. 2 shows the morphology obtained by scanning electron microscopy of binder powder (mining tailings). The micrographs were
Conclusions
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Geopolymeric mortars were successfully manufactured from the geopolymerization of inorganic wastes from the Peruvian informal mining industry and subsequent addition of fine sand.
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The geopolymer mortars studied showed real densities and average porosities of 2.7085 g/cm3 and 27%, respectively.
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The microstructure of the mortars studied consisted of two differentiated phases: (i) an interconnected continuous phase of small grains (geopolymerized mining waste) and (ii) a discontinuous phase of
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was financed by CONCYTEC - FONDECYT within the framework of call E041 with contract N° 140-2020-FONDECYT and was executed in the laboratories of the Universidad Católica San Pablo.
References (13)
- et al.
Mechanical properties of fly ash based geopolymer concrete with full and partial cement replacement
Constr. Build. Mater.
(2016) - et al.
Preparation of geopolymers from vanadium tailings by mechanical activation
Constr. Build. Mater.
(2017) - et al.
Novel geopolymer based composites reinforced with stainless steel mesh and chromium powder
Constr. Build. Mater.
(2017) - et al.
Comparative study of high temperature composites
Compos. B Eng.
(2001) - et al.
Effect of elevated temperature son geopolymer paste, mortar and concrete
Cem. Concr. Res.
(2010) - et al.
Use of recycled wash water and returned plastic concrete in the production of fresh concrete
Adv. Cem. Based Mater.
(1994)