Three-dimensional printing with cement-based materials is a promising manufacturing technique for civil engineering applications that already allows for the design and the construction of complex and highly customized structures using a layer-by-layer deposition approach. The extrusion mechanism is one of the most expensive parts of the 3D printer. Also, for low-scale 3D printers, based on the shape of the extruder and the geometry limitation of the mixing blade, the 3D mixture is often limited to a narrow range of materials due to the risk of layer splitting or blockage. Therefore, there is a need to develop affordable and feasible alternatives to the current design–fabrication–application approach of 3D printers. In this paper, various newly designed mixtures of fiber-reinforced mortars that can be 3D printed using only a commercially available screw pump are analyzed based on their fresh properties and mechanical characteristics. The results, in terms of extrudability, buildability, flowability, and flexural and compressive strengths, highlight the potential of using this technology for constructing complex structures with high strength and durability. Also, the reduced facility requirements of this approach enable 3D printing to be made more available for civil engineering applications. With further innovations to come in the future, this method and these mixtures can be extended for the sustainable and economically feasible printing of single-family housing units.

Studying emerging and cutting-edge digital construction techniques, especially the utilization of 3D printing for concrete/mortar materials, holds significant importance due to the potential benefits that these technologies might offer over the traditional approach of casting concrete in place. In this study, a mixture composed of Portland cement, water, sand, limestone filler and polypropylene fibers was utilized for 3D printed concrete production towards the sustainable constructions approach. The benefits that sustain this statement include reduced construction time and material requirements, diminished error and cost, increase in construction safety, flexibility of architectural design, and improved quality with much less construction cost and waste. The microstructure, fresh and hardened mechanical properties of the polypropylene fiber reinforced 3D concrete were investigated. The results indicated that it is essential to attain a slump measurement of approximately 40 mm and a slump flow within the range of 140 to 160 mm, as stipulated by relevant standards (ASTM C1437 and C230/C230 M), in order to create a 3D concrete mixture suitable for extrusion. Also, the effects of printing parameters, fiber dosage, material composition, and other factors on the 3D printed concrete strength were discussed, and the corresponding adjustments were addressed.

Cultural and religious heritage assessments and restorations are considered to be a fundamental requirement of any modern society because these constructions represent one of the most meaningful and tangible connections to our past. With rare exceptions, heritage buildings were built with materials and systems that could bear gravitational loads but not bending and shearing resulting from seismic loading. Thus, in many cases, earthquake ground motions have led to severe degradation and even the collapse of various parts of these structural systems. In order to address these issues, repair and replacement techniques are applied as common parts of restoration work. In the peculiar case of stone masonry structures, a standalone macroscopic examination is not self-assured and, most often, can lead to an inadequate selection of a replacement material. Therefore, a knowledge of mesoscopic, petrographic, physical and mechanical properties is compulsory in the design, planning and execution of restoration work. From this perspective, the present research has taken, as a case of study, the Frumoasa monastic complex from Iași, Romania, introducing microscopic, XRF (X-ray fluorescence) spectroscopy and petrographically based approaches, comparing three limestone samples with a sample dislodged from the original wall. The physical properties (bulk and real densities, open porosity and capillary water absorption coefficient) and the mechanical properties (compressive and tensile strengths) were also experimentally determined. The samples were extracted from stone quarries located on the territories that were part of the same historical region as the Frumoasa monastic complex. Based on the outcomes of this study, suitable criteria for the stone replacement—consisting of identifying the main structure, quarry rock petrographical parameters and physical and mechanical characteristics—were determined and applied.

This study provides insight into the structural assessment, diagnosis, and strengthening of the medieval church of Tazlău Monastery in Piatra Neamț, Romania. The first part of the paper briefly presents the wider context of strengthening and preserving heritage churches and monastic buildings and describes the architectural setting and the structural features of the traditional Romanian Orthodox churches. The second part of the paper is a case study related to the rehabilitation of a medieval heritage church, which is the paramount building of a larger monastic complex. Erected in 1496, the church of the Nativity of the Blessed Virgin Mary closely follows the medieval traditional Orthodox patterns from both architectural and structural points of view. Structural assessment and diagnosis revealed that degradations were induced and developed throughout the life of the structure due to approximately 24 earthquakes (estimated at over 6.0 magnitude) having endangered the structural safety of the building and the mural iconography. After the structural diagnosis, a combined and complex method of strengthening consisting of both grouting and introducing steel rods in vertically drilled galleries along the entire height of the walls was selected. The main advantage of applying this combined strengthening strategy was a remarkable enhancement of the structural seismic performance of the church building.

This study investigates the aerodynamic behavior of roof structures under wind-induced forces, focusing on buildings equipped with photovoltaic panels. Experimental data were obtained through wind tunnel testing of three 1:100 scale models, each representing a distinct roof geometry: gabled, hipped, and multi-pitched. Measurements of dynamic pressure and pressure coefficients were conducted for various wind incidence angles, ranging from 0° to ±150°. The results highlight the impact of roof geometry and PV panel placement on the pressure distribution, with notable variations due to flow separation and vortex formation around the panels. Gabled roofs exhibited pronounced pressure gradients, while hipped roofs showed more uniform distributions. Multi-pitched roofs demonstrated the most complex aerodynamic behavior due to their variable slopes. These findings enhance the understanding of wind-structure interactions for buildings with roof photovoltaic panels, contributing to the development of more resilient and energy-efficient structures. The research supports sustainable construction practices by improving wind load predictions and informing design decisions that promote the safe integration of renewable energy systems into the built environment.

This study offers insights into the management of intervention works aimed at conserving and revitalizing historical structures, focusing on the Bârnova Monastery in Iași, Romania. The study begins by contextualizing the broader challenges associated with preserving heritage churches and monastic buildings, elucidating the architectural characteristics and structural aspects typical of traditional Romanian Orthodox churches. Subsequently, the study delves into a detailed case analysis centered on the restoration of the medieval Bârnova Monastery, particularly its paramount structure, the Saint George Church, erected in the XVII century. This church exemplifies the traditional Orthodox architectural and structural norms prevalent during the medieval period. Through a structural diagnosis, the study identifies the vulnerabilities of the Saint George Church, which have been exacerbated by the impact of approximately 24 earthquakes of magnitudes exceeding 6.0 throughout its history. In response, a multifaceted approach to strengthening was devised, involving a combination of grouting and the installation of steel rods within vertically drilled galleries spanning the entire height of the walls. The adoption of this integrated strengthening strategy proved advantageous, significantly enhancing the seismic resilience of the church while simultaneously addressing the preservation needs of its historical features. This case study not only contributes to the body of knowledge on conservation and revitalization practices but also offers valuable insights into the effective management of intervention works for safeguarding heritage structures against seismic risks.