The construction sector is responsible for a significant share of global CO₂ emissions, largely due to the production of Portland cement. The need to reduce the environmental impact of concrete has driven research towards low-clinker-content mixtures and the integration of innovative materials capable of enhancing the thermophysical performance, such as phase change materials (PCM). PCM can contribute to the material’s energy efficiency by improving the thermal regulation of concrete structures. In this context, the present study is conducted within the framework of the SINCERE project, which provides the tools for optimising the carbon footprint and energy performance of historic buildings, by utilising innovative restoration materials and practices, energy harvesting technologies, and information and communication technology (ICT) tools. This work aims to develop and characterize a high-performance fiber-reinforced mortar (UHPC) with reduced clinker content and the incorporation of microencapsulated PCM. The research was conducted through an experimental campaign divided into two phases. In the first phase, six different mix designs were analyzed, featuring three different types of cement and two experimental superplasticizers, in order to identify the optimal mixture to be further developed in the second phase. The characterization was performed through fresh-state tests, mechanical tests in compression and flexural strength, as well as microstructural and chemical analyses via SEM-EDS. In the second phase, starting from the optimized mix (designated as "IV10"), metallic amorphous alloy fibers, natural pozzolan as a partial clinker replacement, and microencapsulated PCM were gradually incorporated into the cementitious matrix. The characterization of these new mixtures was carried out through mechanical tests, thermodynamic analyses, and shrinkage measurements, including both total and autogenous shrinkage. The results showed that the addition of metallic fibers significantly improved flexural strength and ductility, while clinker substitution with pozzolan maintained adequate mechanical performance while reducing the material's environmental impact. The inclusion of PCM led to an increase in microporosity, resulting in a reduction of mechanical strength by approximately 10% in compression and 20% in flexural strength. However, thermodynamic tests did not show significant improvements in the material’s ability to regulate internal temperature, suggesting that the amount of PCM used (1.7% by volume) may not be sufficient to effectively influence the thermal performance of the mortar. In conclusion, the developed fiber-reinforced mortar demonstrated excellent mechanical properties and a reduced carbon footprint due to clinker reduction. However, to achieve significant benefits in terms of thermal efficiency, it is recommended to evaluate an increase in the PCM content in the mixture, while considering its potential impact on workability and mechanical performance.
Il settore delle costruzioni è responsabile di una significativa percentuale delle emissioni globali di CO₂, in gran parte derivanti dalla produzione di cemento Portland. La necessità di ridurre l'impatto ambientale del calcestruzzo ha portato alla ricerca di miscele a basso contenuto di clinker e all'integrazione di materiali innovativi in grado di migliorarne le prestazioni termofisiche, come i materiali a cambiamento di fase (PCM). I PCM, infatti, possono contribuire all'efficienza energetica del materiale, favorendo la regolazione termica delle strutture in calcestruzzo. In questo contesto, il presente studio è condotto nell’ambito del progetto SINCERE, il quale fornisce gli strumenti per l’ottimizzazione dell’impronta di carbonio e delle prestazioni energetiche degli edifici storici, attraverso l’impiego di materiali e pratiche innovative per il restauro, tecnologie per la raccolta e l’utilizzo dell’energia, nonché strumenti basati sulle tecnologie dell’informazione e della comunicazione (ICT). Questo lavoro si propone di sviluppare e caratterizzare una malta fibrorinforzata ad alte prestazioni (UHPC) con ridotto contenuto di clinker e l'incorporazione di PCM microincapsulati. La ricerca è stata condotta attraverso una campagna sperimentale articolata in due fasi. Nella prima fase, sono stati analizzati sei diversi mix design, con tre differenti tipologie di cemento e due additivi superfluidificanti sperimentali, al fine di identificare la miscela ottimale da sviluppare nella seconda fase. La caratterizzazione è stata eseguita mediante prove allo stato fresco, test meccanici a compressione e flessione, nonché analisi microstrutturali e chimiche tramite SEM-EDS. Nella seconda fase, partendo dal mix ottimale identificato (denominato "IV10"), sono stati progressivamente introdotti nella matrice cementizia fibre metalliche in lega amorfa, pozzolana naturale in sostituzione parziale del clinker e PCM microincapsulati. La caratterizzazione delle nuove miscele è stata condotta mediante test meccanici, analisi termodinamiche e prove di ritiro totale e autogeno. I risultati ottenuti hanno evidenziato che l’aggiunta delle fibre metalliche ha migliorato significativamente la resistenza flessionale e la duttilità del materiale, mentre la sostituzione del clinker con pozzolana ha permesso di mantenere adeguate prestazioni meccaniche riducendo l'impatto ambientale. L’inclusione dei PCM ha comportato un aumento della microporosità, con una conseguente riduzione della resistenza meccanica di circa il 10% in compressione e il 20% in flessione. Tuttavia, le prove termodinamiche non hanno mostrato miglioramenti significativi nella capacità del materiale di regolare la temperatura interna, suggerendo che il contenuto di PCM utilizzato (1,7% in volume) potrebbe non essere sufficiente a influenzare efficacemente le prestazioni termiche della malta. In conclusione, la malta fibrorinforzata sviluppata ha dimostrato di possedere eccellenti proprietà meccaniche e una ridotta impronta di carbonio grazie alla riduzione del clinker. Tuttavia, per ottenere benefici significativi in termini di efficienza termica, si raccomanda di valutare un incremento della quantità di PCM nella miscela, considerando il possibile impatto sulla lavorabilità e sulle prestazioni meccaniche del materiale.
Ultra High Performance Concrete with reduced embodied carbon: fresh state, mechanical and durability performance validation
Nicoloso, Jacopo;AUSTONI, LORENZO
2024/2025
Abstract
The construction sector is responsible for a significant share of global CO₂ emissions, largely due to the production of Portland cement. The need to reduce the environmental impact of concrete has driven research towards low-clinker-content mixtures and the integration of innovative materials capable of enhancing the thermophysical performance, such as phase change materials (PCM). PCM can contribute to the material’s energy efficiency by improving the thermal regulation of concrete structures. In this context, the present study is conducted within the framework of the SINCERE project, which provides the tools for optimising the carbon footprint and energy performance of historic buildings, by utilising innovative restoration materials and practices, energy harvesting technologies, and information and communication technology (ICT) tools. This work aims to develop and characterize a high-performance fiber-reinforced mortar (UHPC) with reduced clinker content and the incorporation of microencapsulated PCM. The research was conducted through an experimental campaign divided into two phases. In the first phase, six different mix designs were analyzed, featuring three different types of cement and two experimental superplasticizers, in order to identify the optimal mixture to be further developed in the second phase. The characterization was performed through fresh-state tests, mechanical tests in compression and flexural strength, as well as microstructural and chemical analyses via SEM-EDS. In the second phase, starting from the optimized mix (designated as "IV10"), metallic amorphous alloy fibers, natural pozzolan as a partial clinker replacement, and microencapsulated PCM were gradually incorporated into the cementitious matrix. The characterization of these new mixtures was carried out through mechanical tests, thermodynamic analyses, and shrinkage measurements, including both total and autogenous shrinkage. The results showed that the addition of metallic fibers significantly improved flexural strength and ductility, while clinker substitution with pozzolan maintained adequate mechanical performance while reducing the material's environmental impact. The inclusion of PCM led to an increase in microporosity, resulting in a reduction of mechanical strength by approximately 10% in compression and 20% in flexural strength. However, thermodynamic tests did not show significant improvements in the material’s ability to regulate internal temperature, suggesting that the amount of PCM used (1.7% by volume) may not be sufficient to effectively influence the thermal performance of the mortar. In conclusion, the developed fiber-reinforced mortar demonstrated excellent mechanical properties and a reduced carbon footprint due to clinker reduction. However, to achieve significant benefits in terms of thermal efficiency, it is recommended to evaluate an increase in the PCM content in the mixture, while considering its potential impact on workability and mechanical performance.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/236090