This thesis investigates the use of Coal Mine Waste Geomaterials (CMWGs) as partial or total replacements of fine and coarse aggregates in mortars and concretes, as part of the MINRESCUE Project funded by the European Commission for the coal and steel research Fund (RFCS 2014-2020 GA 899518). The use of these materials in concrete can bring numerous benefits, first of all less exploitation of natural resources such as sand and gravel. Moreover, their use could be a beneficial solution to the problem of mining industry wastes disposal in a world economy characterized by increasing energy demand and a gradual fossil fuel abandonment. Sustainable concretes must preserve their characteristics over time even in aggressive environments. For this reason the new mixtures have been evaluated through performance and durability tests, that analyzed resistance to carbonation and chloride diffusion phenomena as main causes of concrete reinforcement corrosion. Mortar durability has been evaluated subjecting the specimens to freeze-thaw cycles. The results for the new mixtures are compared with those of reference ones. This thesis tests have been conducted on concretes and mortars whose natural aggregates have been replaced by monoricycled or biricycled aggregates from the mining sites of Poltegor, Marcel (Poland) and Subterra (Spain). The monoricycled aggregates are Coal Mining Wastes (CMW), while the biricycled ones come from Construction Demolition Wastes (CDW) in which sand and gravel have been partially replaced by CMW. The work has been carried out at different scales by evaluating only fine fraction volume replacement in mortar, fine and coarse fractions replacement, and only coarse fraction replacement in concrete. Sand in mortar has been replaced by the fine fraction of CMW for 25%, 50% and 100%, while the following substitutions were considered for concrete: (a) reference sample; (b) replacement of 25% of coarse fraction by CMW; (c) replacement of 13% of both fine and coarse fractions by CMW; (d) replacement of 30% of coarse fraction by biricycled aggregates; (e) two mixes replacement of 15% of both fine and coarse fractions by biricycled aggregates from different sources. Promising results have been observed, particularly for mixtures substitutions affecting only the coarse aggregate. Mono and biricycled aggregates from Subterra perform better than aggregates from the Central Mining Institute of Poland (Poltegor and Marcel). Mortar tests showed lower tensile and compressive strength values for increasing percentage of replacement. Only tensile strenght was negatively affected by freeze-thaw cycles. The higher water absorption of CMW coarse fraction compared to the gravel one influenced the lower workability of mixtures with monoricycled aggregate, causing the necessary addition of superplasticizer in some cases. The encouraging results achieved confirm the possibility to pursue this path as a solution for coal mining wastes disposal problem.
La tesi indaga l’uso di scarti provenienti dalle miniere di carbone (Coal Mine Waste Geomaterials, CMWGs) in sostituzione parziale o totale di aggregati fini e grossolani per malte e calcestruzzi, nell'ambito del Progetto MINRESCUE finanziato dalla Commissione Europea per il Fondo di ricerca per il carbone e l'acciaio (RFCS 2014-2020 GA 899518). I benefici derivanti dall’uso di tali materiali nel calcestruzzo possono essere molteplici. In primo luogo, un minore sfruttamento di risorse naturali come sabbia e ghiaia. Inoltre, il loro impiego potrebbe costituire una soluzione vantaggiosa al problema dello smaltimento dei rifiuti dell’industria mineraria, in un’economia mondiale caratterizzata da un crescente aumento della domanda energetica e da un progressivo abbandono dei combustibili fossili. Un calcestruzzo sostenibile deve durare nel tempo anche in ambienti aggressivi. Per questo le nuove miscele sono state provate in termini di prestazioni e di durabilità, in particolare analizzando la resistenza ai fenomeni di carbonatazione e di diffusione dei cloruri in quanto principali cause della corrosione delle armature all’interno dei calcestruzzi. La durabilità della malta è stata, invece, valutata sottoponendo i provini a cicli di gelo e disgelo. I risultati vengono confrontati con quelli di miscele di riferimento. In questa tesi sono state svolte prove su calcestruzzi e malte in cui gli aggregati naturali sono stati sostituiti da aggregati monoriciclati o biriciclati provenienti dai siti minerari di Poltegor, Marcel (Polonia) e Subterra (Spagna). Gli aggregati monoriciclati sono scarti dell’attività di estrazione del carbone (Coal Mining Waste, CMW), mentre gli aggregati biriciclati provengono dalla frantumazione di calcestruzzo (Construction Demolition Waste, CDW) in cui sabbia e ghiaia sono state sostituite parzialmente con CMW. Il lavoro è stato svolto su scale differenti valutando la sostituzione in volume della sola frazione fine nella malta, della frazione fine e grossolana e della sola frazione grossolana nel calcestruzzo. Nella malta la sabbia è stata sostituita con la frazione fine di CMW per il 25%, 50% e 100%, mentre per il calcestruzzo sono state considerate le seguenti sostituzioni: (a) campione di riferimento; (b) sostituzione del 25% della frazione grossolana con CMW; (c) sostituzione del 13% della frazione fine e 13% grossolana con CMW; (d) sostituzione del 30% della frazione grossolana con aggregati biriciclati; (e) due mix sostituzione del 15% della frazione fine e 15% grossolana con aggregati biriciclati di diversa provenienza. Sono stati osservati risultati promettenti, in particolare per le miscele in cui la sostituzione interessa il solo aggregato grossolano. Gli aggregati mono e biriciclati provenienti da Subterra ottengono prestazioni migliori rispetto agli aggregati forniti dall’Istituto Centrale Minerario della Polonia (Poltegor e Marcel). Dalle prove su malta si osservano valori di resistenza a trazione e compressione più bassi al crescere della percentuale di sostituzione; i cicli di gelo disgelo hanno influito negativamente solo sulla resistenza a trazione. Il maggiore assorbimento di acqua della frazione grossolana di CMW rispetto alla ghiaia ha influito sulla minore lavorabilità delle miscele con aggregato monoriciclato rendendo necessaria, in alcuni casi, l’aggiunta di superfluidificante. Gli esiti incoraggianti confermano la possibilità di perseguire questa strada come soluzione per il problema dello smaltimento dei rifiuti delle miniere di carbone.
Calcestruzzi e malte con aggregati monoriciclati e biriciclati da residui di estrazione del carbone : uno studio su prestazioni e durabilità
Gandais, Clara;Randazzo, Alice
2022/2023
Abstract
This thesis investigates the use of Coal Mine Waste Geomaterials (CMWGs) as partial or total replacements of fine and coarse aggregates in mortars and concretes, as part of the MINRESCUE Project funded by the European Commission for the coal and steel research Fund (RFCS 2014-2020 GA 899518). The use of these materials in concrete can bring numerous benefits, first of all less exploitation of natural resources such as sand and gravel. Moreover, their use could be a beneficial solution to the problem of mining industry wastes disposal in a world economy characterized by increasing energy demand and a gradual fossil fuel abandonment. Sustainable concretes must preserve their characteristics over time even in aggressive environments. For this reason the new mixtures have been evaluated through performance and durability tests, that analyzed resistance to carbonation and chloride diffusion phenomena as main causes of concrete reinforcement corrosion. Mortar durability has been evaluated subjecting the specimens to freeze-thaw cycles. The results for the new mixtures are compared with those of reference ones. This thesis tests have been conducted on concretes and mortars whose natural aggregates have been replaced by monoricycled or biricycled aggregates from the mining sites of Poltegor, Marcel (Poland) and Subterra (Spain). The monoricycled aggregates are Coal Mining Wastes (CMW), while the biricycled ones come from Construction Demolition Wastes (CDW) in which sand and gravel have been partially replaced by CMW. The work has been carried out at different scales by evaluating only fine fraction volume replacement in mortar, fine and coarse fractions replacement, and only coarse fraction replacement in concrete. Sand in mortar has been replaced by the fine fraction of CMW for 25%, 50% and 100%, while the following substitutions were considered for concrete: (a) reference sample; (b) replacement of 25% of coarse fraction by CMW; (c) replacement of 13% of both fine and coarse fractions by CMW; (d) replacement of 30% of coarse fraction by biricycled aggregates; (e) two mixes replacement of 15% of both fine and coarse fractions by biricycled aggregates from different sources. Promising results have been observed, particularly for mixtures substitutions affecting only the coarse aggregate. Mono and biricycled aggregates from Subterra perform better than aggregates from the Central Mining Institute of Poland (Poltegor and Marcel). Mortar tests showed lower tensile and compressive strength values for increasing percentage of replacement. Only tensile strenght was negatively affected by freeze-thaw cycles. The higher water absorption of CMW coarse fraction compared to the gravel one influenced the lower workability of mixtures with monoricycled aggregate, causing the necessary addition of superplasticizer in some cases. The encouraging results achieved confirm the possibility to pursue this path as a solution for coal mining wastes disposal problem.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/217454