Search Results (129)

This study presents a comprehensive non-destructive evaluation of a broad range of construction materials using the impulse excitation of vibration (IEV) technique. Tested specimens included low- and normal-strength concrete, fiber-reinforced concrete (with basalt, polypropylene, and glass fibers), lime mortars (NHL-2 and -3.5), plaster, and clay bricks (light and dark). Compressive and flexural strength tests complemented dynamic resonance testing on the same samples to ensure full mechanical characterization. Flexural and torsional resonance frequencies were used to calculate dynamic elastic modulus, shear modulus, and Poisson’s ratio. Strong correlations were observed between dynamic elastic modulus and shear modulus, supporting the compatibility of dynamic results with the classical elasticity theory. Flexural frequencies were more sensitive to material differences than torsional ones. Fiber additives, particularly basalt and polypropylene, significantly improved dynamic stiffness, increasing the dynamic elastic modulus/compressive strength ratio by up to 23%. In contrast, normal-strength concrete exhibited limited stiffness improvement despite higher strength. These findings highlight the reliability of IEV in mechanical properties across diverse material types and provide comparative reference data for concrete and masonry applications. Full article

Eco-friendly mortars have been manufactured with hybrid binders made of blast furnace slag and a reduced amount of clinker. The objective is to explore new formulations suitable for reinforced structures. Previous studies are mainly focused on activation with sulfates, a salt that is corrosive to reinforcing steel. Sodium nitrate and sodium carbonate, easily implementable in construction, have been used as activators in two different concentrations that involve similar Na content. A Type II PC mortar is used as reference. The dimensional stability of the mortars during curing (at 99% RH) and subsequent drying at 40% RH, has been evaluated, as well as their porosity and mechanical properties. Böhme tests revealed that studied hybrid binders have lower wear resistance than PC mortar. Activation with Na₂CO₃ allows the obtention of mortars with reduced porosity and good compression resistance, but generates microcracking that favors chloride diffusion. Activation with nitrates favors precipitation of AFm phases identified through differential thermal analysis. Nitrates in moderate amounts (4% w/w) allow manufacturing hybrid mortars with good resistance to chloride penetration and reasonably good mechanical properties. Hence, this binder can be a promising option for reinforced structures. Higher amounts of nitrates (8%) for activation give rise to more porous mortars. Full article

The development of sustainable cementitious materials is crucial to reduce the environmental footprint of the construction industry. Alkali-activated materials (AAMs) have emerged as promising environmentally friendly alternatives; however, their compatibility with natural stone in heritage structures remains poorly understood, especially regarding salt migration and related damage to stones. This study presents a novel methodology for assessing salt movement in solid materials between two types of stones—Boñar and Silos—and two types of binders: blended Portland cement (BPC) and an AAM. The samples underwent capillarity and immersion tests to evaluate water absorption, salt transport, and efflorescence behavior. The capillarity of the Silos stone was 0.148 kg·m⁻²·t^−0.5, whereas this was 0.0166 kg·m⁻²·t^−0.5 for the Boñar stone, a ninefold difference. Conductivity mapping and XRD analysis revealed that AAM-based mortars exhibit a significantly higher release of salts, primarily sodium sulfate, which may pose a risk to adjacent porous stones. In contrast, BPC showed lower salt mobility and different salt compositions. These findings highlight the importance of evaluating the compatibility between alternative binders and heritage stones. The use of AAMs may pose significant risks due to their tendency to release soluble salts. Although, in the current experiments, no pore damage or mechanical degradation was observed, additional studies are required to confirm this. A thorough understanding of salt transport mechanisms is therefore essential to ensure that sustainable restoration materials do not inadvertently accelerate the deterioration of structures, a process more problematic when the deterioration affects heritage monuments. Full article

Aminotris(methylene phosphonic acid) (ATMP) and poly(acrylic acid) sodium salt (PAA) have shown favorable results in the treatment of porous building materials against weathering damage, showing promising potential as mixed-in additives during the production of lime-based mortars. This study investigates the impact of these additives on microstructure and mechanical properties. Additives were introduced in various concentrations to assess their influence on CaCO₃ crystallization, porosity, strength, and carbonation behavior. Results revealed significant modifications in the morphology of CaCO₃ precipitates, showing evidence of nanostructured CaCO₃ aggregates and vaterite stabilization, thus indicating a non-classical crystallization pathway through the formation of amorphous CaCO₃ phase(s), facilitated by organic occlusions. These nanostructural changes, resembling biomimetic calcitic precipitates enhanced mechanical performance by enabling plastic deformation and intergranular bridging. Increased porosity and pore connectivity facilitated CO₂ diffusion towards the mortar matrix, contributing to strength development over time. However, high additive concentrations resulted in poor mechanical performance due to the excessive air entrainment capabilities of short-length polymers. Overall, this study demonstrates that the optimized dosages of ATMP and PAA can significantly enhance the durability and mechanical performance of lime-based mortars and suggests a promising alternative for the tailored manufacturing of highly compatible and durable materials for both the restoration of cultural heritage and modern sustainable construction. Full article

Historical masonry structures deteriorate over time, requiring restoration and strengthening. Hydraulic lime-based mortars (HLMs), due to their compatibility with historical materials, are commonly used for this purpose. This study examines the fire resistance of masonry walls constructed with HLMs. Masonry prisms with clay bricks were prepared using HLMs in accordance with material testing standards. Specimens were subjected to high temperatures ranging from 200 °C to 800 °C, followed by flexural–compression tests for mortar and compression tests for masonry prisms. A total of 20 masonry prism specimens, 15 brick specimens, and 15 mortar specimens were tested, including reference specimens at room temperature. Experimental results indicate that masonry prisms, clay bricks, and HLMs progressively lose their mechanical properties as temperature increases. The elastic modulus of masonry prisms was evaluated according to relevant standards, and Finite Element Analysis (FEA) was conducted to validate temperature-dependent material properties. The stress–strain response of M15 HLM masonry prisms was determined, addressing the absence of such data in EN 1996-1-2. Additionally, compression test results were compared with digital image correlation (DIC) analyses to enhance measurement accuracy. This study provides critical insights into the thermal performance of masonry walls with HLMs, contributing to the development of fire-resistant restoration materials. Full article

Cement–based mortars are essential in both modern construction and heritage conservation, where balancing mechanical strength with material compatibility is crucial. Mortars containing ––binders with low hydraulic activity, such as CEM II/B–L, often exhibit increased porosity and diminished strength, limiting their suitability for structurally demanding applications. This study investigates the potential of multiwalled carbon nanotubes (MWCNTs) to enhance the mechanical and microstructural properties of mortars formulated with both CEM II/B–L and CEM I binders. The influence of CNT incorporation was systematically assessed through compressive and flexural strength tests, vacuum saturation tests, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and differential thermal analysis (DTA). The results demonstrate significant mechanical improvements attributable to nanoscale mechanisms including crack bridging, pore–filling, and stress redistribution. Microstructural characterization revealed a refined pore network, increased densification of the matrix, and morphological modifications of hydration products. These findings underscore the effectiveness of CNT reinforcement in cementitious matrices and highlight the critical role of binder composition in influencing these effects. This work advances the development of high–performance mortar systems, optimized for enhanced structural integrity and long–term durability. Full article

Sustainable architectural heritage conservation focuses on preserving historical buildings while promoting environmental sustainability. It involves using eco-friendly materials and methods to ensure that the cultural value of these structures is maintained while minimizing their ecological impact. In this paper, the use of the hydroxyapatite (HAp) in various combinations on masonry samples is presented, with the aim of identifying the ideal solution to be applied to an entire historical building in Banloc monument. The new solution has various advantages: compatibility with historical lime mortars (chemical and physical), increased durability under aggressive environmental conditions, non-invasive and reversible, aligning with conservation ethics, bioinspired material that avoids harmful synthetic additives, preservation of esthetics—minimal visual change to treated surfaces, and nanostructural (determined via SEM and AFM) reinforcement to improve cohesion without altering the porosity. An innovative approach involving hydroxiapatite addition to commercial mortars is developed and presented within this paper. Physico-chemical, mechanical studies, and architectural and economic trends will be addressed in this paper. Some specific tests (reduced water absorption, increased adhesion, high mechanical strength, unchanged chromatic aspect, high contact angle, not dangerous freeze–thaw test, reduced carbonation test), will be presented to evidence the capability of hydroxyapatite to be incorporated into green renovation efforts, strengthen the consolidation layer, and focus on its potential uses as an eco-material in building construction and renovation. The methodology employed in evaluating the comparative performance of hydroxyapatite (HAp)-modified mortar versus standard Baumit MPI25 mortar includes a standard error (SE) analysis computed column-wise across performance indicators. To further substantiate the claim of “optimal performance” at 20% HAp addition, independent samples t-tests were performed. The results of the independent samples t-tests were applied to three performance and cost indicators: Application Cost, Annualized Cost, and Efficiency-Cost-Performance (ECP) Index. This validates the claim that HAp-modified mortar offers superior overall performance when considering efficiency, cost, and durability combined. Full article

This study investigates the in-plane shear behavior of solid brick masonry walls, both unreinforced and retrofitted using Reinforced Khorasan Jacketing (RHJ), a traditional pozzolanic mortar technique rooted in Iranian and Ottoman architecture. Six one-block-thick English bond masonry walls were tested in three configurations: unreinforced with Horasan plaster (Group I), reinforced with steel mesh aligned to wall edges (Group II), and reinforced with mesh aligned diagonally (Group III). All the walls were plastered with 3.5 cm of Horasan mortar and tested after 18 months using diagonal compression, with load-displacement data recorded. A detailed 3D micro-modeling approach was employed in finite element simulations, with bricks and mortar modeled separately. The Horasan mortar was represented using an elastoplastic Mohr-Coulomb model with a custom softening law (parabolic-to-exponential), calibrated via inverse parameter fitting using the Nelder-Mead algorithm. The numerical predictions closely matched the experimental data. Reinforcement improved the shear strength significantly: Group II showed a 1.8 times increase, and Group III up to 2.7 times. Ductility, measured as post-peak deformation capacity, increased by factors of two (parallel) and three (diagonal). These enhancements transformed the brittle failure mode into a more ductile, energy-absorbing behavior. RHJ is shown to be a compatible, effective retrofit solution for historic masonry structures. Full article

Anti-washout admixtures (AWAs) are a unique component of underwater non-dispersive concrete (UNDC), which gives the concrete the ability to remain undispersed in water. On some special occasions, freshly mixed underwater non-dispersive concrete is exposed to the erosion of moving water, and conventional acrylamide-based AWAs are only suitable for static water or the water flow rate is small. In this study, the inorganic component nanosilica (NS) is modified, treated, and copolymerized with the organic components acrylamide (AM) and acrylic acid (AA) to form an inorganic–organic hybrid polymer with a hyperbranched structure, which changes the linear structure of the original polyacrylamide molecule, and we optimize the synthesis process. The polymers are characterized at the microscopic level and their compatibility with polycarboxylic acid water-reducing agents (SP) is investigated. In addition, the polymers are compared and evaluated with commonly used PAM in terms of their working performance. The experimental results indicated that under specific process conditions, polymers endow cement mortar with good resistance to water erosion. At the same time, the polymers’ three-dimensional network structure is prominent, with good compatibility with SP and better anti-dispersity. The microstructure of the cement paste with added polymers is dense and flat, but its flowability and setting time are slightly worse. This study provides a new development direction for the development of AWAs under a dynamic water environment, which has specific engineering significance. Full article

The use of binders in construction dates back to antiquity, with lime-based materials historically playing a significant role. However, the 20th century brought the widespread replacement of lime with Portland cement (PC), for its superior mechanical strength, durability, and faster setting time. Despite these advantages, the restoration of historic masonry structures has revealed the incompatibility of PC with traditional materials, leading to damage due to increased brittleness, stiffness, and reduced permeability. Consequently, lime mortars remain the preferred choice for heritage conservation. To enhance their durability while maintaining compatibility with historic materials, the incorporation of carbon-based nanoparticles has gained attention. This study investigated the impact of the carbon nanotubes (CNTs) additive on two types of lime-based mortars, calcium lime (CL) and hydraulic lime (HL), evaluating structural and mechanical properties, heat transport characteristics, and hygric properties after modification by CNTs with dosages of 0.1%, 0.3%, and 0.5% binder weight. Incorporation of CNTs into CL mortar resulted in an increase in mechanical strength and slight reduction in heat transport and water absorption due to changes in porosity. The addition of CNTs into HL mortars reduced porosity, pore size distribution, and other depending characteristics. The utilisation of CNTs as an additive in the investigated lime-based composites has been identified as a potentially effective approach for the reinforcement and functionalisation of these composite materials, as they exhibited enhanced mechanical resistance while preserving their other engineering properties, making them well suited for use as compatible mortars in building heritage repairs. Full article

Concrete and mortar production consumes significant natural resources, leading to environmental concerns and sustainability challenges. Sustainable alternatives, such as industrial byproducts, have been explored to replace clinkers and aggregates. Basalt rock powder (BRP) is a promising option due to its physical and chemical properties, including its better particle size distribution and compatibility with cementitious composites, and studies have highlighted its pozzolanic activity and its potential to improve mechanical properties (compressive strength, flexural strength, and durability). Reusing rock dust as a raw material could transform it into a mineral byproduct, benefiting the new material and reducing waste volumes. This article presents a systematic literature review on the use of BRP in construction materials, conducted using the Scopus, ScienceDirect, PubMed, and Web of Science databases and following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) procedures. The search resulted in 787 articles (up to December 2024) and, after the screening process, 17 met the inclusion criteria. From the selected articles, information regarding the utilization of this waste product; its influence on mechanical properties, pozzolanic activity, and durability; and the sustainability associated with its use was compiled. The risk of bias was low as the search was comprehensive, all the papers were peer-reviewed, and all authors reviewed the papers independently. In conclusion, the studies demonstrate the potential of using BRP as a component of cementitious materials, indicating it as a possible innovative solution to the current challenges in the construction industry. Full article

This study investigates structural integrity and proposes retrofitting solutions for the historical two-storey school building in Thrapsano, Crete, severely impacted by the September 2021 earthquake. An extensive methodology was adopted, incorporating field surveys, material characterization, finite element modeling, and experimental analysis. The assessment is focused on identifying structural damage, such as cracking and delamination in masonry walls, and evaluating the dynamic and static performance of the load-bearing system under seismic loads. Key interventions include grouting for masonry reinforcement, replacement of mortar with compatible materials, stitching of cracks, and the addition of reinforced concrete and metallic tie elements to enhance diaphragm action. Advanced numerical simulations, validated through experimental data, were employed to model the pre- and post-retrofit behavior of the structure. The proposed retrofitting measures align with Eurocodes 6 and 8, and the Greek code for masonry structures (KADET), aiming to restore the structural stability and improve seismic resilience while respecting the building’s historical significance. The results from the finite element analysis confirm the effectiveness of the interventions in reducing tensile stresses and improving load redistribution, ensuring compliance with modern safety standards. This case study offers a framework for the seismic retrofitting of heritage structures in a similar context. Full article

This study investigated the use of activated biochar derived from olive stone waste and recycled masonry aggregates in porous mortar mixtures and assessed their behaviour under accelerated carbonation curing conditions. Three mortar mixtures were produced, incorporating 0%, 5%, and 10% activated biochar by volume. The physical, chemical, and mechanical properties of the mortars were analysed, including the compressive strength, flexural strength, water absorption, porosity, and CO₂ capture capacity. Additionally, calorimetry tests were performed on cement pastes with 0%, 0.5%, 1%, 3%, 15%, and 20% activated biochar to evaluate their impact on setting times and ensure compatibility between activated biochar and cement. The results showed that the addition of biochar improved mechanical properties, particularly under accelerated carbonation curing, whereas active biochar (AcB) significantly enhanced the compressive and flexural strengths. Furthermore, biochar incorporation boosted CO₂ capture efficiency, with the 10% biochar mix showing up to 147% higher CO₂ uptake, compared with a control. These findings suggest that activated biochar and recycled masonry aggregates can be effectively utilised to develop sustainable construction materials and thereby contribute to carbon sequestration and the reduction in environmental impacts. This research fills the gaps in the current knowledge on the use of activated biochar from olive stones waste in cement-base materials under accelerated carbonation conditions. Full article

The high seismic vulnerability of unreinforced masonry buildings urgently calls for researchers to develop sustainable reinforcing methods and materials. This paper presents an innovative lime-based mortar reinforced with randomly oriented basalt fibers for the reinforcement of masonry heritage. The main aim of this study is to understand the effect of the content and the length of basalt fibers on the mortar’s mechanical behavior. As a cementitious material made mostly out of lime, the mortar is chemically compatible with the historical substrate and therefore suitable in cases of restoration works on architectural heritage. Moreover, the chopped basalt fibers are randomly oriented, and this characteristic makes the overall layer effective in all directions, as the state of stress induced by seismic action is directionally undetermined. The newly proposed reinforcement system is characterized by a twofold aspect related to sustainability: 30% of the aggregates composing the mortar mix design is a recycled result of the ruins of the 2009 L’Aquila earthquake, and the chopped fibers are made out of basalt, widely known for its environmentally supportable peculiarity. The study consists of testing samples characterized by two fiber lengths and six fiber contents, along with one set of plain mortar samples. Specimens measuring 160 mm × 40 mm × 40 mm are first tested in a three-point bending (TPB) configuration, aiming to determine the flexural strength and the post-peak capacity through the calculation of the fracture energy. Then, the two broken pieces resulting from the TPB tests, each measuring 80 mm × 40 mm × 40 mm, are tested in splitting and compression, respectively, aiming to compute the tensile and compressive strengths. Finally, to provide a trend for the mortar’s mechanical properties, a regression analysis is performed by fitting the experimental data with simple linear, polynomial, and exponential regression models. Results show that: (i) both fiber content and fiber length are responsible for a linear increase of the flexural strength and the fracture energy; (ii) for both short- and long-fiber mortar samples, the tensile strength and the compressive strength parabolically increase with the fiber content; (iii) the increase in fiber content and fiber length always generates a reduction in the conglomerate workability. The fiber content (FC) optimization with respect to the mechanical properties leads to a basalt FC equal to 1.2% for long-fiber samples and an FC equal to 1.9% for short-fiber ones. Full article

The Ateneo Sueco del Socorro, built in 1927 in Sueca, Spain, is a prime example of the 20th-century architectural transformation, using reinforced concrete. Designed by architect Juan Guardiola, it reflects the Art Deco style, incorporating ornamental elements from Eastern civilizations. The building’s structure includes masonry walls, concrete columns, and vaulted ceilings. The building displayed a high level of damage due to the oxidation and corrosion of the reinforcements that compose the façade, which led to the definition of the most appropriate study and intervention methodology, applying contemporary tests for reinforced concrete. The original project’s structural design reflects the construction methods of its time, with sculptural elements using Fallas modeling techniques, resulting in various concrete and mortar types. After the façade presented a pathological condition in the early 21st century that made its restoration urgent, a study methodology was followed with current tests to accurately determine the lesions, their degree of damage, and compatible materials for restoration. Corrosion on the façade is mainly triggered by carbonation and the depassivation of reinforcements, exacerbated by environmental issues like moisture retention and oxygen permeability. Repairs should use compatible pre-mixed mortars, with surface inhibitors recommended to extend the lifespan of reinforcements. Full article