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    Optimization of Air Lime Concrete and Air Lime-based Ternary Mixtures with Sustainable Additives for Enhanced Performance in Heritage Buildings
    (2024-10-21) Alvarez-Galindo, J.I. (José Ignacio); Kyriakou; Çam, E. (Elif); Navarro-Blasco, I. (Iñigo); Fernandez-Alvarez, J.M. (José María)
    The urgent need for sustainable, carbon-negative construction materials has been intensified due to global warming (Barbhuiya, 2023; Haik, 2020). Historic buildings face unique challenges in integrating eco-friendly parameters due to the necessity of compatibility of new materials with historic structures and mitigating their long-term impacts (ICOMOS, 2003). The replacement of OPC with lime in concretes and mortars enables lower carbon emissions and compatibility with historic buildings, although it exhibits higher porosity, water absorption and lower compressive strength than OPC (González-Sánchez, 2021; Rosell, 2023; Velosa, 2009). In this case, admixtures are used to improve the performance of lime-based mixes (Grist, 2013; Seabra, 2009). The study focuses on optimising lime concrete and air lime-based ternary mixes by incorporating eco-friendly additives, as different pozzolanic agents and fibres, to enhance their physical and mechanical properties to be used in restoration works. Silica fume, which is a by-product, and natural volcanic ash were selected as pozzolanic agents and added in different percentages between 0–30%. Hemp and basaltic fibres were included in 1%. The study evaluated the effects of different binders and additives through analyses such as fluidity, water retention, and setting time, also compressive strength tests (7th-28th days). The fresh state analyses revealed that adding silica fume reduced the slump values of the mortars by 13%, whereas volcanic ash and fibres had no significant impact on these values. It was also observed that mixtures containing volcanic ash exhibited lower water retention than those with silica fume. Additionally, the inclusion of basalt fibres reduced water retention in the lime-based ternary mortar by up to 4% compared to those containing hemp fibres. According to mechanical tests, cement and silica fume contributed to the compressive strength values of lime-based mixtures. However, volcanic ash and fibres negatively affected compressive strength values in the early stage. As a conclusion, using silica fume and cement in lime-based mixtures reduces the workability of mortars, contrary to volcanic ash and fibres, while increasing mechanical properties even in the early stages.
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    Vaterite Calcined Clay Cement (VC3) as a Low-Carbon Solution
    (2024-10-21) Alvarez-Galindo, J.I. (José Ignacio); Kyriakou; Rubio-Aguinaga, A. (Andrea); Navarro-Blasco, I. (Iñigo); Nofalah, M.H. (Mohammad Hossein); Fernandez-Alvarez, J.M. (José María)
    Climate change, driven by rising CO2 levels, is a critical global challenge. Portland cement production, exceeding 4 Gt/year with demand projected to rise by 50%, significantly contributes to this issue. Consequently, there's growing interest in developing low-carbon cementitious binders to reduce the construction industry's environmental impact. This study explores vaterite, a metastable calcium carbonate polymorph, for its potential to enhance cementitious materials' sustainability and performance. Vaterite Calcined Clay Cement (VC3) is investigated as a lowCO2 alternative to traditional cement. Vaterite can sequester approximately 0.44 kg CO2 per kg produced and potentially has a lower manufacturing carbon footprint. Recent advancements have made large-scale vaterite production economically viable, contributing to significant CO2 emission reductions. A scalable vaterite production method was applied utilizing a rapid precipitation technique involving mixing at a 2:1:1 molar ratio of K2CO3, CaCl2, and NH4Cl solutions, followed by filtration and ethanol treatment. This method yields high-purity vaterite making it well-suited for cement applications. The study investigated the effects of varying vaterite content, cement reduction levels, and Metakaolin-to-Vaterite (MK/V) ratios on the compressive strength, and fresh state characteristics of VC3 formulations. Results demonstrated an enhancement of long-term compressive strength (ca. 60% to 80%) of OPC mortar at 28 days when replacing calcite with vaterite up to 15%. Reduction in cement content to 45% and 40% of the total binder proportion, resulted in average compressive strength decreases of 17% and 23%, respectively. Furthermore, results demonstrated that by decreasing MK/V ratio from 3 to 1, compressive strength increases from 20MPa to ca. 27 MPa, that indicates potential pathways for more sustainable formulations. Rheological analysis demonstrated that vaterite improves flowability about 5% compared to calcite, addressing a challenging aspect of traditional Limestone Calcined Clay Cement (LC3) systems. By increasing MK/V ratios from 1 to 3 a decrease in workability of ca. 6% is observed. The effectiveness of polycarboxylate ether (PCE) superplasticizer in enhancing rheology was confirmed across various mix designs. This comprehensive approach to VC3 optimization offers promising pathways for developing high-performance, low-carbon cementitious materials, contributing to the sustainable future of the construction industry and potentially enabling carbon capture at gigaton scales.
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    Optimized Phase Change Material-Enhanced Lime Renders for Energy-Efficient Building Envelopes: Thermal and Durability Characterization
    (2024-10-21) Alvarez-Galindo, J.I. (José Ignacio); Kyriakou; Rubio-Aguinaga, A. (Andrea); Navarro-Blasco, I. (Iñigo); Fernandez-Alvarez, J.M. (José María)
    The construction sector's substantial contribution to global energy consumption and carbon emissions necessitates the development of innovative, sustainable building materials (PachecoTorgal et al., 2014; UN Environment Programme, 2019; Fei et al., 2021). Lime mortars, traditionally used as renders for building envelopes, are experiencing renewed interest due to their low environmental impact and compatibility with heritage conservation (Campo and Grosso, 2022; Manoharan and Umarani, 2022; Rodriguez-Navarro et al., 2023). This research focuses on the optimization of lime renders through the incorporation of microencapsulated Phase Change Materials (PCMs), specifically PCM24 and PCM18, which exhibit melting temperatures of 24°C and 18°C, respectively. These PCMs are designed to enhance thermal regulation in different climatic zones by storing and releasing heat at temperatures critical to building comfort (Saffari et al., 2017; Li et al., 2021). The optimized lime renders were formulated with the simultaneous addition of a superplasticizer, an adhesion booster, and a pozzolanic agent, ensuring improved workability, adhesion, and durability, key factors for their application in building envelopes. This study emphasizes the need to not only improve the energy efficiency of the material but also ensure its long-term durability, as sustainable construction requires materials that maintain performance over extended periods (Cunha, Aguiar and Ferreira, 2017).