Search Results (242)

In this study, the water-repellent performance of Expanded Perlite (EP) coated with stearic acid (SA) at different coating/EP ratios (0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4% and 5%) and the capillary water absorption and thermal conductivity behaviors of the modified insulation mortars prepared at these different coating/EP ratios were investigated experimentally. In contrast to the existing literature, experimental studies were carried out for both coated and uncoated EP particles used in mortars to which water-repellent polymers were not added, and the minimum and maximum coating amounts showing the lowest capillary water absorption and slump were determined. In addition, the sustainability of modified insulation mortars consisting of EP-coated SA was determined by sustainable thermal performance (STP). In other words, this study is the first in the literature to determine how the thermal conductivity values of these mortars may change during their use in buildings. According to the experimental results, water absorption, which is an undesirable property, decreased significantly when coated with SA, and even SA-coated expanded coarse perlite (SCP) showed almost no water-absorption behavior at coating levels above 2%. The water-repellent performance of SCP was determined to be 83.2% between 0.1% and 0.4%. In addition, for coarse mortars (MCs), the best water-repellent performance was achieved at a 5% coating/EP ratio, with a 37% reduction in the capillary water-absorption coefficient. In addition, it was found that STP values increased as the coating/EP ratio increased. In other words, modified insulation mortars became more sustainable with an increasing SA coating/EP ratio. The highest STP values were observed in Groups 2 and 4 at a 5% coating/EP ratio, with MC-5 reaching 39.27% in Group 2 and MF-5 reaching 30.30% in Group 4. The results are important from a practical/industrial point of view and from a scientific point of view. Full article

This current review examines modeling approaches for renovating reinforced concrete (RC) buildings for vertical forest (VF) application, taking into account structural retrofitting, energy systems, forestry integration, and occupant comfort. The study assesses research conducted with an advanced 3D finite element analysis and the use of retrofitting modeling techniques, including textile-reinforced mortar (TRM), fiber-reinforced polymer (FRP), seismic joints, and green concrete applications. The energy system modeling methods are reviewed, taking into account the complexity of incorporating vegetation and seasonal variations. During forestry integration, three main design parameters are identified, namely, root systems, trunks, and crowns, for their critical role in the structural stability and optimal environmental performance. The comfort models are identified evolving from static to adaptive models incorporating thermal, acoustic, visual and air quality parameters. The current review consists of more than one hundred studies indicating that the integration of natural systems to buildings requires a multidimensional and multidisciplinary approach with sophisticated systems. The findings of this review provide the basis for implementing VF models to RC buildings, while highlighting areas requiring further research and validation. 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

The inherent limitations of ordinary cement mortar—characterized by its high brittleness and low flexibility—result in a diminished load-bearing capacity, predisposing concrete pavements to cracking. A novel approach has been proposed to enhance material performance by incorporating emulsified asphalt and latex into ordinary cement mortar, aiming to improve the flexibility and durability of concrete pavements effectively. To further validate the feasibility of this proposed approach, a series of comprehensive experimental investigations were conducted, with corresponding conclusions detailed herein. As outlined below, the flexibility properties of the modified cement mortar were systematically evaluated at curing durations of 3, 7, and 28 days. The ratio of flexural to compressive strength can be increased by up to 38.9% at 8% emulsified asphalt content at the age of 28 days, and by up to 50% at 8% latex content. The mechanism of emulsified asphalt and latex-modified cement mortar was systematically investigated using a suite of analytical techniques: X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG-DTG), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through comprehensive analyses of microscopic morphology, hydration products, and elemental distribution, the enhancement in cement mortar toughness can be attributed to two primary mechanisms. First, Ca²⁺ ions combine with the carbonyl groups of emulsified asphalt to form a flexible film structure during cement hydration, thereby reducing the formation of brittle hydrates. Second, active functional groups in latex form a three-dimensional network, regulating internal expansion-contraction tension in the modified mortar and extending its service life. Full article

This study investigates the thermal performance of 23 different mortar types, each containing different mixes, properties, and additives. A comprehensive literature review was conducted to collect experimental data on the thermal properties of these mortars, which were then used in a numerical analysis through thermal finite element modeling. The results showed that all mortar types contributed to reducing the internal temperature of structural steel and reinforced concrete elements, with performance primarily influenced by key factors such as the mortar’s thermal conductivity, specific heat capacity, thermal diffusivity, and coating thickness. In particular, the mortar with glass fiber reinforced polymer (GFRP) as a slag substitute and the mortar with expanded perlite replacing sand showed the highest thermal protection and achieved a temperature reduction on the order of 100%. In contrast, mortars containing 30% vermiculite or 15% light expanded polyvinyl chloride (PVC) as a sand substitute showed the lowest thermal performance. Full article

The regulatory mechanism of vinyl acetate-ethylene (VAE) in the interfacial properties of silicate cement–silica fume repair mortar was investigated by examining the effects of varying VAE contents (0 wt.% to 10.0 wt.%) on mortar fluidity, mechanical strength, and interfacial bonding strength. The interface microstructure was also examined to reveal its evolution. Results indicate that VAE enhances mortar fluidity through micro-filling and interfacial activity. At 10% VAE content, fluidity reached 265 mm, a 14.97% increase. However, VAE introduction reduced compressive and flexural strength due to pore induction at low dosages and polymer network interference at high dosages. By improving interfacial stress transfer and refining calcium sulfoaluminate (AFt) and C-S-H crystals in the interfacial transition zone, VAE increased the tensile bonding strength of the repaired mortar to 2.1 MPa at 28 days, a 133.3% increase, according to microscopic analysis. Based on performance analysis, 5.0 wt.% VAE is optimal, increasing interfacial bonding strength by 133.3% while limiting compressive strength loss to 9.4%, thus achieving interfacial collaborative optimization of the repaired mortar. Full article

Traditional fiber-reinforced polymer (FRP) retrofit methods can restore the strength of reinforced concrete columns well, but stiffness is also partly restored. To increase the initial stiffness of retrofitted columns, this study investigated the seismic behavior of retrofitted resilient reinforced concrete (RRC) columns that were retrofitted by different methods, including high-strength mortar retrofit, carbon fiber-reinforced polymer (CFRP) retrofit, and CFRP and steel plate retrofit. In addition, the effect of the axial load was also considered. Quasi-static tests were conducted twice on five specimens, i.e., before and after repairing. The first test was used to create earthquake damage, and the second test was used to compare the seismic behavior of the retrofitted columns. The experimental results indicated that the CFRP retrofit method, whether with a steel plate or not, can restore the lateral resistance capacity well; furthermore, the drift-hardening behavior and self-centering performance were well maintained. The residual drift ratio of the CFRP-retrofitted column was less than 0.5%, even at a drift ratio of 3.5%, and less than 1% at the 6% drift ratio. However, the initial stiffness was only partly restored using the CFRP sheet. The introduction of steel plates was beneficial in restoring the initial stiffness, and the stiffness recovery rate remained above 90% when CFRP sheets and steel plates were used simultaneously. The strain distribution of the CFRP sheet showed that the steel plate did work at the initial loading stage, but the effect was limited. By using the steel plate, the CFRP hoop strain on the south side was reduced by 68% at the 6% drift ratio in the push direction and 38% in the pull direction. The axial strain of CFRP cannot be ignored due to the larger value than the hoop strain, which means that the biaxial stress condition should be considered when using an FRP sheet to retrofit RC columns. Full article

To improve the construction performance of inorganic adhesives used for bonding fiber-reinforced polymer (FRP) sheets to reinforce concrete structures, make rational use of resources, and reduce carbon emissions, double-shear tests on the interface bonding performance between bonded FRP sheets and cement mortar test blocks, as well as four-point bending tests on bonded carbon fiber-reinforced polymers (CFRPs) to reinforce concrete beams, were conducted using basic magnesium sulfate cement (BMSC) as the adhesive. The influence laws of parameters, such as the type of FRP sheet and the number of FRP sheet bonding layers on the shear performance of the bonding interface between BMSC and cement mortar test blocks, were investigated, as well as the influence laws of the number of CFRP sheet bonding layers and the type of binder on the bending performance of CFRP sheet-reinforced beams. The test results show that the ultimate load of CFRP-reinforced beams bonded with BMSC as the binder increased by 17.4% to 44.4% compared with the unreinforced beams and simultaneously improved the flexural stiffness and crack-limiting ability of the reinforced beams. The failure of the reinforced beam begins with the separation of the CFRP sheet from the concrete at the middle and bottom of the beam span. When the CFRP sheet of the reinforced beam is one layer and two layers, the flexural bearing capacity reaches 91.4% and 96%, respectively, of the reinforced beam, with epoxy resin as the binder under the same conditions. With the increase in the number of CFRP layers, the flexural bearing capacity of the reinforced beam improves, but the increased flexural bearing capacity does not increase proportionally with the increase in the number of sheet layers. By introducing the influence coefficient of BMSC on the flexural bearing capacity (FBC) of reinforced beams, based on the test results, the formula for calculating the FBC of concrete beams, which are reinforced with CFRP sheets bonded by BMSC, was developed. After verification, the calculation formulas established in this paper have high accuracy and can provide theoretical references for similar engineering applications. Full article

The construction sector faces growing pressure to adopt sustainable alternatives amid the global plastic-waste crisis. This study presents a novel use of mechanically recycled high-density polyethylene (HDPE) and polypropylene (PP) to manufacture full-scale plastic rebars for mortar-free, light-load construction applications. A total of 48 samples, plain and ribbed, across three diameters (12 mm, 19 mm, and 25 mm) were fabricated and tested. Due to the absence of standardized protocols for recycled plastic rebars, tensile testing was conducted in reference to ASTM A615. Characterization techniques such as X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) confirmed the material’s structural features and polymer integrity. XRD confirmed the crystalline phases of HDPE and PP, while SEM revealed ductile fracture in HDPE and brittle failure in PP. The 25 mm ribbed PP rebars demonstrated superior performance, achieving a maximum load capacity of 12.2 ± 0.6 kN, a toughness index of 19.3 ± 1.0, and energy absorption of 101.6 ± 5.0 N-m × 10. These results affirm their suitability for lightweight structural components such as boundary walls, partition panels, and mortar-free interlocking systems. Unlike prior studies that confined recycled plastics to filler roles in composites, this work validates their direct application as full-section, load-bearing members. Additionally, a polynomial-based empirical model was formulated to predict the tensile behavior of the recycled rebars. The findings underscore the potential of mechanical extrusion as a low-emission, scalable solution to convert plastic waste into durable construction materials that support circular economic principles. Full article

In order to deeply investigate the effects of various factors on the shear behavior of RC beams strengthened with fiber-reinforced polymer (FRP) grid–polymer cement mortar (PCM) composite, and to construct a more accurate formula for the shear behavior of reinforced concrete beams, the following work is carried out in this investigation: Firstly, the finite element numerical simulation of FRP grid–PCM composite RC beams model is carried out using ABAQUS and compared with the test results to verify the correctness of the model; then, the effects of the amount of FRP grid reinforcement, the elastic modulus of the FRP grid, the shear span ratio of the beam, the concrete strength, and the shear reinforcement ratio on the shear performance of the strengthened beams are analyzed; finally, based on the effective strain of the FRP grid to quantify its actual shear contribution, a calculation formula of the shear behavior Capacity of RC Beams Strengthened with an FRP grid–PCM composite is proposed. The results show that the model established in this paper can effectively simulate the shear behavior of the beams in the test; additionally, the effects of the amount of FRP grid reinforcement, the shear span ratio, and the concrete strength are more significant. Finally, the theoretical results of the calculation formula fit well with the collected experimental ones. 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

This study developed a vinyl acetate-ethylene rapid repair mortar (VAE-RRM) by using a binary blended cementitious system (ordinary Portland cement and sulfoaluminate cement) and vinyl acetate-ethylene (VAE) redispersible polymer powder. The effects of the polymer-to-cement ratio (P/C: 0~2.0%) on setting time, mechanical properties, interfacial bonding, and microstructure were systematically investigated. The results reveal that VAE delayed cement hydration via physical encapsulation and chemical chelation, extending the initial setting time to 182 min at P/C = 2.0%. At the optimal P/C = 0.9%, a synergistic organic–inorganic network enhanced flexural strength (14.62 MPa at 28 d, 34.0% increase) and interfacial bonding (2.74 MPa after interface treatment), though compressive strength decreased to 65.7 MPa due to hydration inhibition. Excessive VAE (P/C ≥ 1.5%) suppressed AFt/C-S-H growth, increasing harmful pores (>1 μm) and degrading performance. Microstructural analysis via scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) demonstrates that VAE films bridged hydration products, filled interfacial transition zones (ITZ), and refined pore structures, reducing the most probable pore size from 62.8 nm (reference) to 23.5 nm. VAE-RRM 3 (P/C = 0.9%) exhibited rapid hardening (initial setting time: 75 min), high substrate recovery (83.3%), and low porosity (<10%), offering an efficient solution for urban infrastructure repair. This work elucidates the dual mechanisms of pore refinement and interface reinforcement driven by VAE, providing theoretical guidance for designing high-performance repair materials. Full article

This study presents a comprehensive review of various advanced methodologies that have been used to enhance the structural and thermal performance of masonry walls through innovative and sustainable retrofitting/upgrading techniques. Focusing on three primary approaches—mechanical/structural retrofitting, thermal retrofitting, and integrated (structural and thermal) retrofitting, this paper critically examines various masonry-strengthening strategies. Retrofitting techniques are categorized by material use and objectives. Fiber-based solutions include insulation materials, fiber composite mortar for strength, FRP for high-strength reinforcement, and TRM for durability. According to the relevant objectives, retrofitting can enhance structural stability (FRP, TRM), improve thermal insulation, or combine both for integrated performance. Particular emphasis is placed on the effectiveness of TRM systems, with a comparative analysis of man-made (glass, steel textile) and natural fiber-based TRM solutions. Regarding integrating natural fibers into TRM systems, this study highlights their potential as eco-friendly alternatives that reduce environmental impact while maintaining or improving structural integrity. Furthermore, it highlights and examines techniques for testing masonry walls. In this context, this review highlights the applicability of natural fiber as a sustainable building material in various retrofitting/upgrading solutions. Full article

It is challenging for mortar to simultaneously enhance the transmission property of water vapor while maintaining excellent waterproofness and impermeability. However, in some applications, both are necessary. Therefore, three different kinds of modifiers, i.e., cementitious capillary crystalline waterproof materials (XYPEX), γ-methacryloxy-propyl-trimethoxy-silane (KH570), and styrene-butadiene rubber latex (SB), are employed to explore how modified mortar can possess excellent waterproofness, impermeability, and the water vapor transmission property simultaneously. Combining characterization techniques, the influencing factors of these three properties are studied. The results indicate that XYPEX promotes the formation of hydration products within pores, improves waterproofness and impermeability, but decreases the water vapor transmission property. KH570 introduces numerous pores ranging from 0.1 to 5 micrometers and enhances the hydrophobicity of mortar; at 1.25% and 2.5% contents, the modified mortar exhibits excellent waterproofness and water vapor transmission property but poor impermeability. SB introduces numerous air pores and forms polymer films; at 20% content, the modified mortar exhibits excellent waterproofness and water vapor transmission property, with impermeability remaining unchanged, making SB a favorable modifier that combines these three properties. Finally, the mechanisms of these three properties are discussed, which provides a theoretical reference for the control of mortar’s waterproofing, impermeability, and water vapor transmission. The selection of modifiers is based on the actual performance requirements. Full article

Concrete is popular in construction due to its strong performance and low maintenance. However, some structures become unsafe over time due to poor maintenance and design flaws. As demand for maintenance grows, restoring older structures is a cost-effective option. Advanced repair techniques aim to extend service life and improve concrete properties, with a focus on eco-friendly solutions. Recent trends have highlighted the potential of incorporating polymers into repair methods, but the use of glycoluril–formaldehyde, a polymeric material known for its hydrogen bonding capacity, remains unexplored in repairing existing structures. This research investigates the effects of glycoluril–formaldehyde in simple matrices like cement paste and mortar to understand its impact. By examining the chemical reactions between glycoluril–formaldehyde with cement paste, this study delves into the fresh, mechanical, and microstructural characteristics. To evaluate the influence of glycoluril–formaldehyde, cement paste specimens were subjected to various tests, including consistency, initial and final setting time, and miniature slump flow tests. Cement mortar specimens were then subjected to compression strength tests conducted at various ages. The results demonstrate that a 3% addition of glycoluril–formaldehyde in concrete offers optimum performance, ensuring improved mechanical strength and microstructure. The microstructural investigation using optical microscopy, an X-ray diffraction, and SEM analysis confirms the polymerization of glycoluril–formaldehyde and the formation of a denser microstructure. The thermogravimetric (TG) and differential thermogravimetric (DTG) analysis provides crucial insights into the thermal stability of the cementitious system, aiding its characterization for high-temperature applications. Full article