Natural Hydraulic Lime Research Articles

Effect of Waste Glass Powder Replacement of Hydraulic Lime on Properties of Natural Hydraulic Lime Mortars

This paper investigates the effects of the partial replacement of natural hydraulic lime (NHL) with waste glass powder (GP) on the physical, mechanical, and microstructural properties of NHL mortars. In the experimental study, five mixtures containing up to 50% GP were prepared to evaluate its effect on the flow, carbonation, unit weight, water absorption, porosity, ultrasonic pulse velocity, capillary water absorption, compressive strength, and microstructure of NHL mortars. The experimental results suggest that the partial replacement of NHL with GP significantly affects the properties of NHL mortars. A reduction in compressive strength was observed with increasing GP content in mortars at both early and later stages. Nevertheless, the compressive strength difference between samples containing 50% GP and the reference was found to be relatively minor at 91 days, implying an enhanced pozzolanic reaction over time. The incorporation of GP improved the consistency and capillary water absorption of mortars, while the opposite was observed for ultrasonic pulse velocity, porosity, and water absorption. The microstructural analysis revealed distinct changes in the structure of samples incorporating GP. The partial substitution of hydraulic lime with GP could be beneficial in reducing the CO2 emissions of NHL mortars.

Development of Biodegradable and Recyclable FRLM Composites Incorporating Cork Aggregates for Sustainable Construction Practices

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

Phase evolution and microstructure changes induced by accelerated carbonation in natural hydraulic lime paste with GGBFS addition

Carbonation is a primary factor driving the continuous improvement of the long-term performance of natural hydraulic lime (NHL). This research systematically examines the impact of accelerated carbonation (3 % CO2) on the carbonation depth, phase composition, microstructure, and compressive strength of hardened natural hydraulic lime (NHL) pastes mixed with different amounts of ground granulated blast furnace slag (GGBFS), termed as S-NHL. The findings show that the hydration reaction products of GGBFS and Ca(OH)2 (CH), such as C3AH10, C4AĈH11, and C-S-H, densify the microstructure of S-NHL, resulting in a decrease in carbonation depth with increasing GGBFS content. Accelerated carbonation (AC) promotes the rapid transformation of a significant quantity of CH into calcite in S-NHL, with the carbonation of CH occurring more readily than the carbonation of hydration reaction products. Throughout the AC process, NHL contains only calcite-type calcium carbonate. In contrast, after 28 days of AC, the carbonation of hydration reaction products such as C3AH10 and C-S-H in S-NHL produces a minor amount of aragonite and vaterite. AC continuously reduces the total pore volume and porosity of S-NHL, but the average pore diameter and most probable pore diameter initially decrease and then slightly increase. AC significantly reduces the large pores in S-NHL, ultimately resulting in pores predominantly composed of capillary pores (50–1000 nm). AC facilitates the development of compressive strength in S-NHL paste, with the increase in compressive strength being positively correlated with its CH content.

Study on modification of natural hydraulic lime historical building repair mortar

Qingdao boasts a wealth of historical buildings, yet they have sustained varying degrees of damage due to environmental erosion over decades. Traditional cement-based repair materials can exacerbate the damage to these structures and often fall short of the stringent requirements for historical building restoration projects. Natural Hydraulic Lime (NHL) offers excellent compatibility and breathability, making it suitable for restorative work on historical buildings. However, its low early strength and durability pose limitations in Qingdao's complex environment. Consequently, this study investigates the enhancement of NHL mortar using Ground Granulated Blast Furnace Slag (GGBFS/BFS) powder. Nine mix formulations were developed to investigate the impact of varying BFS contents on the physical properties and microstructure of the repair mortar. The results indicate that, compared to the reference sample, the modified mortar exhibits reduced water requirement for normal consistency, shorter setting time, lower water absorption, and decreased shrinkage. Regarding mechanical properties, the incorporation of BFS significantly enhances the mechanical strength of the repair mortar. When the proportion of BFS is 60 %, the flexural and compressive strength of the mortar samples increase by 304 % and 611 % at 28 days, respectively. Upon incorporating BFS, a pozzolanic reaction occurs in the alkaline environment, leading to the formation of calcium silicate hydrate (C-S-H) gel. This gel fills the pores within the mortar, enhancing the densification of the system, which in turn improves the mechanical properties and microstructure of the repair mortar. SEM analysis corroborates these findings. XRD analysis confirms that BFS does not introduce harmful substances.

Natural Lime–Cork Mortar for the Seismic and Energetic Retrofit of Infill Walls: Design, Materials, and Method

Recent seismic events have prompted research into innovative and sustainable materials for strengthening and repairing obsolete and vulnerable buildings. These earthquakes have exposed the high seismic vulnerability of existing reinforced concrete (RC) buildings, particularly in secondary structural elements like infill walls. In addition to structural issues, these buildings often face significant energy deficiencies, such as thermal bridges, due to inadequate insulation. Traditionally, structural and energy improvements for residential buildings are addressed separately with different methods and protocols. This preliminary study is part of a broader research initiative at the University of Reggio Calabria (Italy), aiming to design an innovative fiber-reinforced plaster using natural, sustainable, and locally produced materials to enhance the energy and structural performance of existing wall infills. The study investigates two plaster matrices made of natural hydraulic lime and silica sand, with 15% and 30% cork granules added. Mechanical and thermophysical tests on multiple specimens were conducted to evaluate their suitability for seismic and energy retrofitting of infill walls. Results indicate that adding cork reduces mechanical strength by approximately 42% at a 30% cork content without compromising its use in seismic retrofitting. Thermophysical tests show improved thermal performance with a higher cork content. These findings suggest that the lime–cork mixture at 30% is effective, offering excellent ductility and serving as a promising alternative to traditional cementitious plaster systems. The next experimental phase will test matrices with varying percentages of gorse fiber.

The manufacture of natural hydraulic limes: Influence of raw materials' composition, calcination and slaking in the crystal-chemical properties of binders

This study aims to achieve an in-depth understanding of the manufacturing process of natural hydraulic lime (NHL) by assessing the influence of raw materials' chemical- mineralogical composition and the effect of the slaking process. NHLs with variable hydraulicity were manufactured using 56 raw materials from carbonate outcrops in Andalusia (Spain). This study shows that siliceous limestones with microcrystalline quartz generate hydraulic phases after calcination. However, when the amount of this reactive silica exceeds 18% by weight, CaO is not formed, and only calcium silicates appear. It was also found that slaking of NHL leads to partial hydration of the most reactive calcium silicates, reducing the expected reactivity of the lime. Instead, exposure of NHL quicklimes to environmental relative humidity promotes the formation of disordered portlandite and reduces the partial hydration of hydraulic phases. Our findings demonstrate that standard slaking can be replaced by alternative methods for the studied binders.

Wood ash-based binders for lightweight building materials: Evaluating the influence of hydraulic lime and cement on the setting and mechanical properties of wood ash pastes

The shift from fossil fuels to bioenergy has led to increased wood ash output. Since a large proportion of this waste ends up in landfills, recycling wood ash in construction materials is one of sustainable approaches of managing this by-product. However, the amount of biomass ashes currently recycled in building materials is still limited. This study therefore explored the feasibility of valorising four different types of wood ashes in large quantities in the production of lightweight building materials. Thirty pastes with different levels (80, 90, 95 and 100 wt%) of wood ash and (0, 5, 10 and 20 wt%) of natural hydraulic lime (NHL) or ordinary Portland cement (PC) were developed. Partial replacement of wood ash (WA) by NHL or PC accelerated the setting and improved the mechanical properties of blended pastes. The initial and final setting times decreased with increasing NHL or PC content in the mixes. The strength of the pastes increased with increasing NHL or PC levels and curing time. However, wood bottom ash (WBA) mixes were controversial because their mechanical properties gradually weakened over time. For WA-NHL blends, the 28-day flexural and compressive strength ranged from 0.02 to 1.12 MPa and from 0.05 to 2.59 MPa, respectively. On the other hand, for WA-PC pastes, the flexural and compressive strengths at 28 days varied from 0.07 to 2.72 MPa and from 0.13 to 5.49 MPa, simultaneously. These results prove that wood ash can be used effectively as a main component of binding matrices for lightweight building materials.

Development and application of artificial hydraulic lime for Chinese architectural heritage restorations

Lime is commonly employed in the restoration of historic buildings due to its strength properties, which align well with the demands of architectural heritage conservation. However, recent shortages in high-quality limestone raw materials and the commercial inclusion of finely ground limestone powder in hydrated lime powder have led to significant challenges. These include low initial strength, pronounced shrinkage and cracking, and poor resistance to frost. Although natural hydraulic lime (NHL) offers moderate strength, its high cost presents an obstacle to widespread use in architectural heritage restoration. Three types of artificial hydraulic lime (AHL) — AHL1, AHL2, and AHL3 — were prepared with the objective of low cost and easy scalability. These were formulated by incorporating white cement (WC), blast furnace slag powder (BFSP), heavy calcium carbonate powder (HCCP), and industrial-grade white sugar (WS) into industrial-grade hydrated lime powder (IHLP). To align the setting time of the AHLs with the requirements of traditional builders, WS was incorporated as a retarding agent. The addition of WC, BFSP, and HCCP to IHLP resulted in enhancements over IHLP in several key aspects: compressive strength, pore structure post-hardening, dry shrinkage rate, and frost resistance. This approach will enhance the restoration quality of architectural heritage in China, leading to fewer repeated repairs and significant savings in manpower and material costs. Ultimately, AHL2 was applied in the restoration of the Confucius Temple, proving its efficacy and alignment with traditional construction requirements. This research provides valuable theoretical and practical insights for enhancing the preservation of architectural heritage.

Encapsulated crystallisation inhibitor as a long-term solution to mitigate salt damage in hydraulic mortars

Salt (NaCl) weathering in mortar, can be mitigated by incorporating a crystallisation inhibitor (sodium ferrocyanide) during mortar preparation. However, the service-life of the inhibitor is limited, due to its susceptibility to leaching out of mortar. Encapsulating the inhibitor in chitosan-calcium alginate capsules has demonstrated controlled-release of the inhibitor and therefore, reduction in its leaching. Nevertheless, the addition of capsules may have a negative effect on mortar's properties and/or its salt-weathering resistance. In this research, natural hydraulic lime (NHL) and commercial cement-based mortars were prepared, with encapsulated inhibitor and with directly mixed-in inhibitor. Mechanical and physical properties of mortars were assessed experimentally. An accelerated NaCl-weathering test was performed to assess the durability of mortar to salt damage. The damage evolution was assessed visually and by quantifying material loss, efflorescence and leaching of the inhibitor. At the end of the test, crystal morphology inside the pores was examined using SEM. The results show that adding inhibitor, both in encapsulated and mixed-in form, had a negligible effect on the properties of NHL and cement-based mortars. Compared to the reference mortar without inhibitor, NHL-mortars with mixed-in inhibitor and encapsulated inhibitor had a better durability to salt damage, showing negligible material loss. The capsules facilitated controlled-release and reduced leaching of the inhibitor. In cement-based mortars including the reference, no damage was observed; still, the inhibitor was shown to be effective in modifying the salt crystal habit. The results show that encapsulation of the inhibitor can improve the service-life of the mortar without compromising its performance.

New Discovery of Diethyl Carbonate Modified Natural Hydraulic Lime in Heritage Conservation

ABSTRACT Cracks are one of the common diseases on the surface and inside of stone cultural relics. The research and application of grouting materials are crucial for crack conservation of cultural relics. This work mainly studies the modification of Natural Hydraulic Lime (NHL2), a commonly used crack grouting material for stone cultural relics. Diethyl Carbonate (DEC) is used to modify Natural Hydraulic Lime to provide a carbon source within the system, and it can produce the raw material (CO2) needed for the reaction to maintain the continuous occurrence of hydration and carbonation reactions. Diethyl Carbonate-modified Natural Hydraulic Lime (DEC-NHL2) can keep the original physical phase and composition unchanged, refine the grain size, and increase the product of the hydration and carbonation reaction. In addition, it can promote the synchronous carbonation of the inner and surface parts, accelerate the coagulation rate of the slurry and improve the compressive strength, thus substantially enhancing the reaction continuity and stability of the NHL2 slurry, and avoiding the repair damage caused by stress concentration. It provides a new idea for grouting and protection of stone cultural heritages.

Effect of hydration degrees on the accelerated carbonization (3 % CO2) behavior of natural hydraulic lime

Natural Hydraulic Lime (NHL), as a low-carbon binder, possesses a significantly higher carbon sequestration potential compared to cement-based materials. This study aims to elucidate the accelerated carbonation mechanism of NHL5 by investigating the evolution of phase composition and microstructure during the accelerated carbonation process, as well as the preferential reactivity of different carbonatable components. Different hydration levels of NHL5 paste were achieved by controlling various steam curing durations (with a water-to-binder ratio of 0.5); accelerated carbonation conditions included 3±1 % CO2, 25±3°C, and 70±5 % relative humidity. The results indicate that higher hydration levels positively impact the mechanical properties of samples after carbonation. The compressive strength of the sample with carbonation curing 28 after 7 days of steam curing (S7C28) reached 45.6 MPa, and the carbon sequestration per unit mass increased. Specifically, S7C28 achieved an increase in carbon sequestration from 71.8 g/kg to 364.3 g/kg after 28 days of incomplete carbonation, while the high degree of hydration also limited the diffusion of CO2. Qualitative and quantitative analyses confirm that the carbonation reactivity in NHL5 paste follows the order: Ca(OH)2>C-S-H gel>C2S. The continuous generation of carbonation by-products, such as calcite and silica gel, fills the pores of the samples, enhancing their strength. These results suggest that higher hydration levels in NHL5 significantly promote the effectiveness of carbonation curing at a 3 % CO2 concentration, leading to improvements in mechanical performance, carbon sequestration capacity, and microstructural characteristics.

Variations in the physical and mechanical behavior of basalt fiber reinforced NHL mortars exposed to different curing conditions

This paper investigates experimentally the short-term behavior of natural hydraulic lime (NHL) mortars reinforced with ballast fiber for use as structural repair mortars in historic and contemporary buildings. The physical and mechanical properties of mortar mixes reinforced with 0.143–0.215 mm equivalent thick and 12 mm long fibers in volumetric percentages of 1 %, as well as of unreinforced mortars, produced with different compaction methods and cured under different environmental conditions, have been evaluated. A cost-effectiveness analysis has also been carried out to determine the economic impact of these factors in their practical application. It is found that basalt fiber reinforcement provides lower water absorption coefficients and significantly improves the shore hardness, compressive strength, and post-critical flexural behavior of NHL mortars at early ages. Furthermore, it is observed that the compaction procedure can improve the packing density of the mortars providing higher densities, lower water absorption coefficients and higher mechanical strength values. Finally, it is verified that the curing parameters affect unevenly the basalt fiber reinforced NHL mortars and unreinforced NHL mortars, with greater deterioration being observed in the former when sufficient moisture is not ensured. Decreases in hardness, flexural and compressive strength, as well as increases in the water absorption coefficient are important. Consequently, the economic profitability of basalt fiber reinforcement depends on ensuring optimal moisture conditions during curing, especially when the mixes have already lost excess water after the first 2–3 days. The study provides quantitative and qualitative data to determine the appropriate curing parameters for basalt fiber reinforced NHL mortars that are viable in practice for their industrial performance.

Physico-mechanical, structural, and mineralogical analysis of composite concrete incorporating hydraulic lime and pozzolan

This study investigates alternatives to Portland cement (PC) through the utilization of pozzolanic materials like natural hydraulic lime and pozzolan in mortar and concrete production, offering both environmental and economic advantages. Natural hydraulic lime is particularly esteemed for its relevance in restoring architectural relics and preserving cultural heritage, while the incorporation of pozzolan and fine and coarse aggregates adds value to local resources. The study employs a range of comprehensive characterization techniques, including physico-chemical, mineralogical, and mechanical analyses such as X-ray fluorescence, particle size assessment, bulk density evaluation, shrinkage testing, water absorption analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and Proctor Normal and compressive strength tests, among others. Five different formulations, varying from 20 % to 40 % hydraulic lime content and a fixed 25.00 % pozzolan content, underwent testing across five curing periods (7, 14, 28, and 90 days). The results underscore the significant influence of curing time and hydraulic lime proportion on the physical, mineralogical, and mechanical characteristics of lime concrete. Scanning electron microscopy reveals a well-structured matrix in samples from various formulations, credited to effective void filling by lime and pozzolan. Furthermore, the identification of C-S-H phases through X-ray diffraction analysis enhances the concrete matrix, leading to a notable increase in compressive strength of up to 22.00 MPa. Water absorption rises with curing time due to the air curing process, fostering the formation of minor surface pores. This research assesses the environmental impact of hydraulic lime concrete across its lifecycle, underscoring the potential of pozzolans and natural hydraulic lime to produce locally-sourced, economical, and environmentally friendly construction materials, thereby contributing to global efforts in reducing carbon emissions.

Effect of basalt fiber length on the behavior of natural hydraulic lime-based mortars

Abstract The number of studies aimed at the characterization of reinforced lime-based mortars for use in the rehabilitation of historic buildings is still very small. This fact contrasts with the growing interest of the industry in these products as substitutes for cement mortars, both for their constructive advantages (compatibility requirements) and their lower cost (economic and environmental). For this reason, this study investigates the effect of basalt fiber length on the physical, mechanical, and durability properties of reinforced natural hydraulic lime mortars and provides criteria for selecting optical blends to meet the various performance requirements for their use as building materials for traditional and contemporary structures. Specimens with 1% volume of basalt fibers and lengths of 6, 12, 18, and 24 mm have been tested. The results in fresh mortar show that increasing the fiber length decreases the consistency and bulk density, as well as increases the air content. Regarding the durability properties of hardened mortar, no direct relationship is observed between fiber length and the decrease in the water absorption coefficient of reinforced mortars. Nor is there a clear relationship between fiber length and the increase in Shore hardness and the decrease in adhesive strength in the reinforced mortars. On the contrary, for small lengths (up to 12 mm), there is a direct relationship between fiber length and the increase in other fundamental mechanical properties such as flexural and compressive strength. Based on the results obtained, a predictive model is proposed to determine the amplification factor of flexural and compressive strength as a function of fiber length.

Development and performance evaluation of a novel high-ductility fiber-reinforced lime-pozzolana matrix for textile reinforced mortar (TRM) masonry strengthening applications

This paper discusses the development of a high ductility fiber reinforced lime mortar with deflection hardening behavior. In this study, polypropylene fibers have been incorporated in a cementless reference matrix comprising of Natural Hydraulic Lime, silica fume, siliceous aggregates and workability aid admixtures. The properties of the reference and fiber reinforced mortar compositions were assessed by means of standardized laboratory tests and scanning electron microscopy. The reference composition gave an average compressive strength of 12 MPa, rendering it suitable for structural applications. Fiber addition at a dosage of 0.76% by wt. of solids led to a reduction of the compressive strength; however, sufficient load bearing capacity was still achieved (8 MPa). More importantly, the fibers enabled the mortar to sustain useful load after damage initiation, improving post-peak ductility under compression and allowing the material to reach bending stresses up to 20% higher than the first-crack strength. To evaluate the practical application of the proposed materials, their use as matrices in textile reinforced mortar (TRM) strengthening systems was investigated through pilot applications on stone masonry. Diagonal compression tests were performed on 9 ashlar masonry wallettes, including both un-retrofitted and TRM-retrofitted specimens. Single-sided TRMs consisting of alkali resistant glass textiles embedded in either the reference or the fiber reinforced mortar were considered. Specimens retrofitted with TRM constructed using the fiber reinforced mortar, exhibited a remarkable ~ 270% increase in shear strength and > 50% higher deformation capacity, compared to un-retrofitted ones. The strength increment achieved with the reference mortar as the TRM matrix was 80%, with minimal impact on ductility. The TRM comprising the fiber reinforced mortar also showed superior performance in terms of ability to retain integrity at high levels of shear deformation. Overall, the results indicate that the use of fiber reinforced lime matrices in TRM systems applied to masonry substrates has the potential to substantially enhance mechanical performance under in-plane loading, even in cases where only single-sided retrofitting can be realized.

Composite substrates for coral larval settlement and reef restoration based on natural hydraulic lime and inorganic strontium and magnesium compounds

Coral reefs face unprecedented threats from climate change and human activities, making reef restoration increasingly important for the preservation of marine biodiversity and the sustainability of coastal communities. One promising restoration method relies on coral breeding and larval settlement, but this approach requires further innovation to achieve high rates of settlement and survival. In this study, we built on our previous work engineering lime mortar-based coral settlement substrates by investigating three different compositions of a natural hydraulic lime (NHL) base material as well as composite NHL substrates containing alkaline earth metals. These materials were tested with larvae of three reef-building Caribbean coral species: Orbicella faveolata (Mountainous star coral), Diploria labyrinthiformis (Grooved brain coral), and Colpophyllia natans (Boulder brain coral). We found that the base material composition, including its silicate and calcium carbonate (CaCO3) content, as well as the addition of the inorganic additives strontium carbonate (SrCO3), magnesium carbonate (MgCO3), and magnesium sulfate (MgSO4), all influenced coral larval settlement rates. Overall, NHL formulations with lower concentrations of silicate and higher concentrations of calcium, strontium, and magnesium carbonates significantly increased coral settlement. Further, when dissolved ions of magnesium and strontium were added to seawater, both had a significant effect on larval motility, with magnesium promoting settlement and metamorphosis in C. natans larvae, supporting the observation that these additives are also bioactive when incorporated into substrates. Our results demonstrate the potential benefits of incorporating specific inorganic ion additives such as Mg2+ and Sr2+ into substrates to facilitate early coral life history processes including settlement and metamorphosis. Further, our results highlight the importance of optimizing multiple aspects of coral substrate design, including material composition, to promote settlement and survival in coral propagation and reef restoration.

Effects of nano-metakaolin on the enhanced properties and microstructure development of natural hydraulic lime

Effects of nano-metakaolin on the enhanced properties and microstructure development of natural hydraulic lime

Toughness of Natural Hydraulic Lime Fibre-Reinforced Mortars for Masonry Strengthening Overlay Systems

Masonry structures are susceptible to damage and collapse due to seismic actions, a problem in many urban areas. To address this issue, researchers are studying the use of fibre-reinforced mortars as overlay strengthening systems. This study assessed the use of synthetic polyacrylonitrile (PAN) fibres as reinforcement of natural hydraulic lime mortar, focusing on their influence on fresh behaviour and mechanical properties. Natural hydraulic lime (NHL) was chosen for its compatibility with typical older ceramic and natural stone structural masonry and contemporary ceramic brick infill masonry substrates, as well as for the sustainability benefits. The study also assessed the contribution of the PAN fibres to toughness enhancement in the developed formulations. The fresh behaviour of fibre-reinforced mortar (FRM) was found to be adequate for applications with fibre volume fractions below 0.50%. The compressive and flexural strengths were affected differently by the increase in fibre volume fraction, with compressive strength decreasing and flexural strength increasing. The maximum compressive strength of 13.3 MPa was obtained for 0.25% of fibres, while for flexural strength a maximum of 6.70 MPa was achieved with 1.00% of fibres. The compressive and flexural toughness, related to the post-cracking responses, increased with the fibre fraction, and even for fractions as low as 0.25%, an important increment of the capacity to dissipate energy was achieved.

Analysis of the Rheological Properties of Natural Hydraulic Lime-Based Suspensions for Sustainable Construction and Heritage Conservation.

Natural hydraulic lime (NHL)-based binders play a crucial role in preserving cultural heritage structures, ensuring integrity and longevity. Beyond traditional uses, these binders exhibit potential for integration into both non-structural and structural components, being compatible with innovative manufacturing processes such as digital fabrication. Meticulously designed grouts, with applicability in their fresh and hardened states, are essential for heritage stability. This study explores the relationships between mineral additions, chemical admixtures, and lime for grout formulations, aiming to advance our understanding and inform the optimization of materials for heritage restoration. Key questions include the influence of natural volcanic pozzolan (NVP) and metakaolin (MK) on rheology and the impact of varying ratios of superplasticizer on NHL-based grout's rheological behavior. This systematic evaluation of rheological parameters aims to innovate mix designs, expanding NHL-based binders' applicability in construction and science. Our hypotheses suggest that well-designed lime grout formulations, incorporating NVP and MK, can enhance rheological properties, addressing challenges in sustainable construction and heritage conservation. This research provides valuable insights for optimizing lime-based materials, fostering advancements in heritage restoration, and promoting wider NHL-based binder adoption in diverse construction applications.

Monitoring and Calibrating Building Materials Drying Kinetics with Capacitance Sensors

Building materials’ moisture content defines the overall durability and serviceability of buildings and infrastructures. Conventionally, moisture content is estimated by weighing the materials before and after drying. In this work, the results of capacitance wired sensors for measuring moisture content were investigated. These sensors facilitate in situ measurement of capacitance values, with the aid of specialized installation equipment, and the results are accessible via a cloud-based software application. In practice, the main drawback associated with the application of these sensors is related to their calibration. Thus, it is important to investigate different algorithms which convert capacitance readings into moisture content values. To address this, various specimens covering a diverse set of building materials were prepared in the laboratory. This study focused on examining two bricks, two sedimentary stones with low and high porosity values. and four different kinds of mortars (with different binders, namely hydrated lime putty, cement, natural hydraulic lime, and hydrated lime powder and pozzolan). The results indicated that a linear model can be recommended for calibrating sensor capacitance to moisture content measurements. This model can be used for the prediction of building material moisture content with high accuracy, from saturated to the dry state, covering the full range of drying kinetics.