Flexural Properties Research Articles

Investigating the influence of coarse aggregate characteristics and fiber dispersion on the flexural performance of ultra-high performance concrete (UHPC)

The flexural properties of ultra-high performance concrete containing coarse aggregate (UHPC-CA) strongly depend on the characteristics of coarse aggregates and the dispersion of fibers. However, the impact of the interaction between coarse aggregate and steel fibers on the bending performance of UHPC-CA is not well-understood. This study investigated the four-point bending properties of UHPC-CA to clarify the influence of coarse aggregates. Mechanical tests, laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), and image analysis were performed to investigate the impact of coarse aggregate on flexural properties, considering coarse aggregate properties, and steel fiber dispersion. The results indicate that coarse aggregates affect both bending strength and toughness. The type of coarse aggregate primarily influences bending strength, while the quantity of coarse aggregate determines toughness. The peak strength is closely related to the strength of the parent rock, whereas toughness is significantly affected by fiber dispersion. Coarse aggregate can adversely impact toughness by their inherent brittleness and worsening the fiber dispersion within the matrix. Additionally, this paper provides parameters for selecting suitable coarse aggregate for UHPC. It is recommended that coarse aggregate added to UHPC possess a strength approximately 1.5 times that of the matrix, with a particle size not exceeding 10 mm and a content below 30 %.

Effects of low temperatures and steel fibres on the flexural properties of carbonised recycled aggregate concrete

To investigate the effects of low temperatures and carbon dioxide reinforcement on the flexural properties of steel fibre recycled concrete, this study conducted three-point bending tests on 16 sets of carbonated recycled aggregate concrete (CRAC) beams and 16 sets of recycled aggregate concrete (RAC) beams. The flexural properties of them at different low temperatures (20 ℃, 0 ℃, −30 ℃, −60 ℃) and steel fibre volume dosage (0 %, 0.5 %, 1.0 %, 1.5 %) were compared. The flexure toughness index, flexural tensile strength, and equivalent flexural strength were calculated from the macroscopic test results to assess the flexural resistance of CRAC comprehensively. Combined with scanning electron microscopy-energy spectroscopy (SEM-EDS) analysis, the microstructure and elemental content of CRAC were analysed to reveal the mechanism of carbonation and low temperatures on the macroscopic mechanical properties of CRAC. The results showed that the flexural properties of recycled aggregate concrete reinforced with CO2 were significantly improved compared to RAC. The maximum increase in flexural tensile strength and equivalent flexural strength of CRAC after low temperatures was about 61.94 % and 61.38 %, respectively. CO2 can react with the cement hydration products of the recycled aggregates to produce CaCO3 and silica gel, filling in the transition zone of the CRA-matrix interface, which can improve the microstructural densification of the CRAC at low temperatures. With further decrease in temperature, the effect of low temperatures on the flexural properties of CRAC was more significant due to the impact of ice crystal growth, with a maximum enhance in flexural tensile strength and equivalent flexural strength of 131.35 % and 165.93 %, respectively, compared to that at 20 ℃. The strength and toughness of CRAC with 1.5 % steel fibre are improved best at low temperatures.

AN EXPERIMENTAL STUDY CONDUCTED TO DETERMINE THE EFFECTIVENESS AND DURABILITY OF PRESERVATION TREATMENTS ON VOLCANIC TUFF STONES

In this study, two treatments were performed on deteriorated volcanic tuff stone samples taken from a 16th-century historical structure: (i)solventless mixtures of ethyl silicates (TEOS) tetraethoxysilane consolidation product followed by application of two different silane-siloxane-based water-repellent commercial products (TEOS+WR1 and TEOS+WR2), (ii) two different silane-siloxane based water repellent commercial products (one emulsion (WR2) and the other solution (WR1) based). This study aims to determine the effectiveness, compatibility, durability and service life of the studied conservation treatments on tuff stones. Therefore, colorimetric measurements, chemical and petrographic analyses (XRF, XRD, SEM-EDS) and physical and mechanical characterization tests were performed on the treated and untreated samples.Additionally, accelerated weathering tests were performed in the laboratory on all treated stones to determine the long-term performance of the chemical treatments.After these weathering tests,physical (water absorption under atmospheric pressure, water capillarity coefficient, water vapour permeability) and mechanical (ultrasonic pulse velocity, flexural and compressive strength) property tests were performed again and according to the results, the performance change in the efficiency indexes (TEI,%) was calculated. All results were compared and discussed. The results showed the best performance of TEOS+WR1 treatment in improving the consolidating and water-repellency abilities of tuff stone samples.However, the least colour change in the colour measurements after the treatments was in the treatments using emulsion-type water-repellent products.

Tensile, flexural and fatigue properties of different thermoplastic nanocomposites: experimental investigation and ANN prediction of the fatigue life

ABSTRACT Polymer-based nanocomposites have received immense attention in industrial applications as their mechanical properties are superior to traditional polymer composites. In this study, three different thermoplastic polymers, namely (a) polypropylene (PP), (b) acrylonitrile butadiene styrene (ABS), and (c) high-density polyethylene (HDPE) were used for the purpose of engineering different nanoclay-based nanocomposites. The blending of the polymer was performed by varying the nanoclay weight percentage (0.5, 1, 3, and 5 wt.%) using a twin-screw extruder. The different nanocomposites were fabricated through injection moulding process. The composites were fabricated by considering the 90 bars of injection pressure, 60 mm/s of injection speed, and 25 sec of cooling time. The effect of nanoclay inclusion on the mechanical properties of the nanocomposites was evaluated and compared with the neat polymer. The effect of nanoclay inclusion was studied through morphological analysis of the fractured tested specimens. The tensile strength and modulus of ABS-nanoclay (5%) exhibited an enhancement of 30.95% and 35%, respectively as compared to the pure ABS. Meanwhile, the fatigue life revealed an improvement of 66.01%. The tensile strength and modulus of the ABS/nanoclay (5%) were achieved as 38.6 MPa and 1.44 GPa.

Automated design of architectured polymer-concrete composites with high specific flexural strength and toughness using sequential learning

Architectured polymer-concrete composite (APCC) is a promising structural material with high mechanical performance while optimizing the design of APCC for a high flexural strength, high toughness, and light weight remains a challenge. This paper presents a machine learning-based approach to design APCC with high specific flexural strength and toughness. The proposed approach integrates sequential surrogate modelling, Latin hypercube sampling, and Lion Pride Optimization to predict and optimize the flexural properties of APCC. The proposed approach was implemented into designing APCC beams, which were fabricated via 3D printing and tested under flexural loads. Results show that the APCC beams achieved high flexural strength, high toughness, and light weight, simultaneously. The devised architecture of APCC arrested crack propagation and promoted energy dissipation. Parametric studies were performed to evaluate the effect of key design variables of APCC on flexural properties. This research advances the basic knowledge and capabilities of AI-assisted design of APCC.

Optimising Additive Manufacturing to Produce PLA Sandwich Structures by Varying Cell Type and Infill: Effect on Flexural Properties

The objective of this research is to optimize additive manufacturing processes, specifically Fused Filament Fabrication (FFF) techniques, to produce sandwich structures. Mono-material specimens made of polylactic acid (PLA) were produced, where both the skin and core were fabricated in a single print. To optimize the process, variations were made in both the base cell geometry of the core (Tri-Hexagon and Gyroid) and the core infill (5%, 25%, 50%, and 75%), evaluating their effects on static three-point bending behavior. Optical microscopy was employed to assess both the structure generated by additive manufacturing and the fracture modes. The findings reveal that increasing the infill, and thus the core density, enhances the mechanical properties of the structure, although the improvement is such that samples with 50% infill already demonstrate excellent performance. The difference between hexagonal and Gyroid structures is not significant. Based on microscopic analyses, it is believed that the evolution of 3D printers, from open to closed chamber designs, could significantly improve the deposition of the various layers.

Assessment of ply thickness and aluminum foils interleaving on the impact response of CFRP composites designed for cryogenic pressure vessels

Carbon fiber reinforced polymer (CFRP) proved to be the best choice to produce cryogenic pressure vessels coupling a reduced weight with superior mechanical performance. Despite this, CFRPs are prone to fuel leakage due to interconnected matrix cracks resulting from mechanical and thermal stresses. Two strategies were combined in this work to reduce fuel permeability, i.e., increase of plies number and metallic film interleaving, evaluating the cryogenic impact response of these new configurations. At first, the only ply thickness effect was assessed and the hybrid sandwich-like (SL) configuration with traditional CFRP (RC) skins and a thin-ply (TP) core displayed impact and residual flexural properties close to RC ones. Then, the effect of aluminum foils interleaving was investigated, and the interleaved SL configuration displayed higher residual flexural properties than interleaved RC for all temperatures, e.g., the residual flexural strength was 30.3 % higher at room temperature and 14.6 % higher at −70 °C, respectively.

Mechanical and tribological performance of NaOH-Treated bamboo fiber-reinforced recycled HDPE composites under fretting wear conditions

ABSTRACT The study investigates the impact of bamboo fiber reinforcement on the mechanical and tribological properties of recycled high-density polyethylene (rHDPE) composites. Bamboo fibers extracted from locally sourced Bambusa Balcooa were subjected to a comprehensive alkali treatment to enhance their properties, including increased crystallinity, thermal stability, and altered morphology. The treated bamboo fibers were incorporated into rHDPE using a compression molding technique at varying weight percentages (0.5–2.0 wt-%). The results revealed that optimal mechanical performance, particularly tensile strength (155.7 MPa) and modulus (6.6 GPa), was achieved at 1.5 wt-% fiber content, attributed to effective load transfer between the matrix and fibers. Beyond this content, performance declined due to fiber agglomeration and poor dispersion. Flexural properties mirrored these findings, with the highest strength (207.5 MPa) and modulus (11.7 GPa) observed at 1.5 wt-%. Thermogravimetric analysis (TGA) and X-ray diffraction confirmed enhanced thermal stability and crystallinity in treated fibers. Fretting wear tests indicated a reduction in the coefficient of friction with increased fiber content, particularly at lower loads, while wear loss was minimized at 1.5 wt-% BF, suggesting optimal reinforcement. SEM analysis highlighted microstructural changes, including fiber pull-out, debonding, and void formation, correlating with the observed mechanical degradation at higher fiber contents. .

Experimental and numerical study on the flexural properties of RC beams with different CFRP-strengthened schemes

This study conducted a four-point bending experiment investigation on the flexural performances of the RC beams strengthened with various CFRP schemes. Four beams were employed, i.e., the ordinary RC beam (L0), the RC beam bonded with CFRP sheet (L1-C), the CFRP U-wrapped RC beam (L2-U), and the RC beam using CFRP rivets (L3-A). Test results highlighted the obvious improvement in the flexural performances of CFRP-strengthened beams in terms of enhancing load-carrying capacities and limiting overall deformations compared to beam L0. In addition, end anchorage systems, including CFRP U-hoop and CFRP rivets, changed the failure mode, restricted crack propagation, and mitigated the bottom CFRP sheet debonding effectively. The ultimate loads of beams L1-C, L2-U, and L3-A were 27.4 %, 36.4 %, and 41.6 % higher than beam L0, respectively, indicating that CFRP rivets performed the best in improving the beams' flexural properties. Finite element analysis was developed to simulate the bending experiment process. The numerical results comply well with the experiments in terms of the crack distribution pattern and bending force history. Then, parametric studies for the design suggestions with the use of the modes reveal that the implementation of the CFRP rivet with a depth of 80 mm and a diameter of 10 mm seems to be an ideal optimization plan for the beams herein.

Effect of sintering temperature on feature resolution and flexural strength of ceramics fabricated through vat photopolymerization additive manufacturing

PurposeAlthough ceramic additive manufacturing (AM) could be used to fabricate complex, high-resolution parts for diverse, functional applications, one ongoing challenge is optimizing the post-process, particularly sintering, conditions to consistently produce geometrically accurate and mechanically robust parts. This study aims to investigate how sintering temperature affects feature resolution and flexural properties of silica-based parts formed by vat photopolymerization (VPP) AM.Design/methodology/approachTest artifacts were designed to evaluate features of different sizes, shapes and orientations, and three-point bend specimens printed in multiple orientations were used to evaluate mechanical properties. Sintering temperatures were varied between 1000°C and 1300°C.FindingsDeviations from designed dimensions often increased with higher sintering temperatures and/or larger features. Higher sintering temperatures yielded parts with higher strength and lower strain at break. Many features exhibited defects, often dependent on geometry and sintering temperature, highlighting the need for further analysis of debinding and sintering parameters.Originality/valueTo the best of the authors’ knowledge, this is the first time test artifacts have been designed for ceramic VPP. This work also offers insights into the effect of sintering temperature and print orientation on flexural properties. These results provide design guidelines for a particular material, while the methodology outlined for assessing feature resolution and flexural strength is broadly applicable to other ceramics, enabling more predictable part performance when considering the future design and manufacture of complex ceramic parts.

Experimental and numerical study on post-fire flexural capacity of corroded reinforced concrete beams under various cooling methods

This paper investigates the flexural behavior of corroded reinforced concrete (RC) beams after various cooling methods. Twenty-eight RC beams were fabricated, with four beams remaining unexposed to fire and twenty-four subjected to fire damage. The study examined three concrete cover thicknesses (20 mm, 30 mm, and 40 mm), three fire exposure times (60 min, 90 min, and 120 min), and two cooling methods (natural cooling and water cooling) to analyze their impacts on the flexural properties of corroded RC beams. The results revealed that the minimum temperatures experienced by the steel bars were observed with a concrete cover thickness of 40 mm, indicating a reduction of up to 18.19 % compared to a cover thickness of 20 mm. After a 120 min fire exposure, water cooling resulted in brittle failure of corroded RC beams. Relative to room temperature, the peak load of non-corroded specimens with a 20 mm concrete cover thickness decreased by 18.2 % and 26.6 % at 90 and 120 min, respectively. For fire exposure durations of 60, 90, and 120 min, water spraying cooling resulted in a reduction of the peak load of corroded RC beams with a 20 mm cover thickness by approximately −3.9 %, 4.7 %, and 18.9 %, respectively, compared to natural cooling. After 120 min of fire exposure, the bearing capacity of water-cooled specimens increased with increasing concrete cover thickness. Numerical simulations utilizing the finite element method were employed to analyze the thermal response and flexural properties of corroded RC beams. The residual flexural capacity of corroded RC beams post high-temperature exposure was evaluated using three design codes: GB 50010–2010, ACI 318–19, and EN 1992–1-1.

Extruded PLA-CF modeled after human DNA: Effects of thermal shock and structural design on tensile and flexural properties

This study used human DNA structure to inspire an innovative design concept. Mechanical testing assessed how design parameters and thermal shock cycles affected it. As thermal shock cycles increase, material characteristics decrease. After sixty thermal shock cycles, tensile and flexural strengths dropped 43.33% and 35.90%, respectively. DNA structures had a better strength-to-weight ratio than solids. After 60 thermal shock cycles, 2 mm ribs, straight ribs, and hexagonal honeycomb ribs had higher tensile and flexural strengths of 9.42 and 20.76 MPa, respectively.

Fracture Behavior of Crack-Damaged Concrete Beams Reinforced with Ultra-High-Performance Concrete Layers

Reinforcing crack-damaged concrete structures with ultra-high-performance concrete (UHPC) proves to be more time-, labor-, and cost-efficient than demolishing and rebuilding under the dual-carbon strategy. In this study, the extended finite element method (XFEM) in ABAQUS was first employed to develop a numerical model of UHPC-reinforced single-notched concrete (U+SNC) beams, analyze their crack extension behavior, and obtain the parameters necessary for calculating fracture toughness. Subsequently, the fracture toughness and instability toughness of U+SNC were calculated using the improved double K fracture criterion. The effects of varying crack height ratios (a/h) of SNC, layer thicknesses (d) of UHPC reinforcement, and fiber contents in UHPC (VSF) on the fracture properties of U+SNC beams were comprehensively investigated. The results indicate that (1) the UHPC reinforcement layer significantly enhances the load-carrying capacity and crack resistance of the U+SNC beams. Crack extension in the reinforced beams occurs more slowly than in the unreinforced beams; |(2) the fracture performance of the U+BNC beams increases exponentially with d. Considering both the reinforcement effect benefit and beam deadweight, the optimal cost-effective performance is achieved when d is 20 mm; (3) with constant d, increasing a/h favors the reinforcement effect of UHPC on the beams; (4) as VSF increases, the crack extension stage in the U+BNC beam becomes more gradual, with higher toughness and flexural properties; therefore, the best mechanical properties are achieved at a VSF of 3%.

Modified lignin by deep eutectic solvent as a novel coupling agent for wood-plastic composites

In this work, the influence of modified lignin by Deep Eutectic Solvent (DES) as a novel bio coupling agent on the various properties of wood flour- polypropylene composites (WPCs) was investigated. For this purpose, extracted lignin from Bagasse Soda black liquor was modified with Choline chloride–ZnCl2 deep-eutectic solvent (ChCl–ZnCl2 DES) and then different ratios of unmodified and modified lignin (0, 1, 3 and 5 wt%) were added to the wood flour/polypropylene mixture. Different properties of lignin after modification by DES along with physical and mechanical properties of the manufactured composites were measured according to the relevant standard methods. The FTIR analysis indicated that DES- modified lignin has a higher proportion of phenolic hydroxyl groups (1213 cm−1) and a lower one of methoxy groups (2854 cm−1) when compared to virgin lignin. DSC analysis also showed that the glass transition temperature (Tg) of lignin decreased from 90 °C to 80 °C by DES treatment. Based on the results obtained, the physical and mechanical properties of WPCs were continuously improved by increasing the modified lignin content from 1 to 5 wt%. The composites with DES-treated lignin presented lower water absorption and thickness swelling as well as higher flexural, tensile and impact properties compared to those prepared with unmodified lignin at the same fixed level of lignin. Moreover, based on the finding of this research, the composites with 5 wt% DES-treated lignin have relatively better physical and mechanical properties than those made from 2 wt% maleic anhydride polypropylene (MAPP) as a control sample. Modification of lignin with DES improves its uniform dispersion in the polymer matrix according to Scanning Electron Microscopy (SEM) images.

MECHANICAL BEHAVIOUR OF ISTLE FIBRE COMPOSITE REINFORCED WITH EPOXY AND E-GLASS AT DIFFERENT FIBRE ORIENTATIONS

This paper was aimed to study the mechanical properties of Istle fibre composites. The process of fabrication was done by hand layup technique at three different fibre orientations i.e., unidirectional, bidirectional and 45 degrees inclined, and also its effect on tensile and flexural property that was studied in the Instron Testing Machine. The fibre volume ratio was kept uniform for the entire specimen as 50:50. The treatment of istle fibre was done with sodium hydroxide to increase the fibre matrix bonding. The effect of E-glass reinforcement has also been studied in both bending tests and flexural tests. The maximum tensile and bending modulus recorded were from unidirectional fibre specimen.

Influence of fish-scale powder addition and stacking order on mechanical and thermal properties of hybrid kenaf/glass polyester composites

The increasing concern for the environment has driven a surge in popularity of utilizing modern technology to develop new products from renewable resources. To address this, polymer composites are incorporating various bio-waste materials as filler components. This study focuses on fabricating four-layered hybrid polyester laminates using kenaf (K), glass (G), and reinforced with fish scale (FS) powder at concentrations ranging from 5 wt.% to 15 wt.%. Mechanical properties are assessed following ASTM standards to evaluate the optimal FS filler percentage. The results reflect that the KGKG laminate with 15 wt. % FS exhibits utmost tensile strength and hardness, while the same laminate with 10 wt. % FS shows optimal flexural and impact properties. Further, numerical analysis is performed using ANSYS 19.0 software to validate the experimental findings. It is marked that, the results of numerical analysis are align intimately with the experimental data, with a deviation of 5 to 10%. Additionally, the moisture absorption behavior is investigated, and the results revealing that FS filler reduced moisture uptake and enhanced dimensional stability. Further, the study is extended to investigate the thermal attributes of laminates through Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). The fractured surface morphology are studied through Scanning Electron Microscopic (SEM) and the findings reveal significant occurrences of matrix cracking, fiber withdrawal, and the separation of fibers from the matrix. Overall, this study suggests the incorporation of FS bio-fillers into hybridized kenaf/glass laminates in order to improve performance and create environmentally friendly options that suitable for automotive applications.

Utilizing almond shell filler to improve strength and sustainability of jute fiber composites

AbstractIn recent years, natural fibers have begun to replace synthetic fibers in automotive, building, and marine applications because of their sustainability, renewability, low cost, and availability of raw materials. However, because of their low strength, biocomposites are strengthened by hybridization with stronger synthetic fibers or adding fillers. This study reinforced high‐cellulose jute fiber composites with cellulose‐based almond (Prunus amygdalus) shell filler (ASF). Natural waste almond shells were ground to microparticle size. Hybrid composites were prepared by adding microparticulate ASF to the jute fiber composites at 0%, 1.5%, 3%, 4.5%, and 6% by weight. A comprehensive experimental study included tensile, flexural, Charpy impact (flat and edgewise), and shear tests. The addition of ASF significantly improved the mechanical properties of the jute fiber composites, and the best values were obtained with 3 wt.% ASF addition. Tensile, flexural, impact, and shear properties increased by 48.2%, 63.5%, 24.4%, and 52.2%, respectively. Scanning Electron microscopy (SEM) micrographs used in morphological structural analysis prove that the high mechanical values are achieved by ASF strengthening the interlaminar adhesion. This study contributed to developing a hybrid natural composite material reinforced with natural fillers that is stronger, environmentally friendly, and sustainable.Highlights The organic structure of Almond Shell Filler (ASF) ensured the sustainability of natural composites. Cellulosic ASF significantly contributed to the structural stiffness and strength of jute fiber composites. ASF reduced voids, improved fiber‐matrix bonding, and prevented debonding and delamination. ASF optimized the mechanical performance of jute fiber composites at 3%.

Extreme temperature influence on low velocity impact damage and residual flexural properties of CFRP

AbstractIn this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (−50°C, room temperature, and 100°C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100°C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At −50°C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post‐impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate.Highlights Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and −50°C, RT, and 100°C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100°C). Electrospun veils enhanced CFRP bending and residual post‐impact properties at RT and 100°C.

Flexural behaviour of bamboo concrete beams

Bamboo plants can be found in both tropical and non-tropical locations of the world, it is thought of as a naturally occurring, quick-growing, and renewable resource. Bamboo is seen as a good alternative for construction due to the high energy requirements of current building materials and the limited availability of other naturally occurring materials like wood., bamboo is considered a good alternative for construction. To minimize carbon footprints in the environment, the research illustrates the flexural properties of Bamboo reinforced concrete to be able to use it as a successful replacement for steel bars. To study the flexural behavior, the total reinforcement constant and partially replaced steel with bamboo at 0%, 25%, 50%, 60%, 75% & 100%. Bamboo is a versatile material that can be used in a variety of construction applications, and it can also be employed in a variety of housing applications, notably roofing, and flooring. Moreover, bamboo culms are often used directly as structural members such as beams, slabs, and columns without any alteration. Bamboo can also be used as reinforcement in concrete as a replacement for steel. The shear and flexural behavior of bamboo-reinforced concrete beams is significantly better than that of plain concrete beams. Furthermore, bamboo fiber-reinforced concrete is a good alternative to existing fiber-reinforced concrete, such as glass and steel fibers.

Enhancing the performance of 3D-printed fiber-Reinforced mortar: synergistic effects of clays and bacterial cells as viscosity modifying agents

The absence of standardized 3D concrete printing mixtures drives ongoing material exploration. This study investigates mineral and bio-based viscosity modifying agents (VMAs) application in fiber-reinforced cementitious mortar. Nano-montmorillonite, sepiolite, and bacterial cells function as supplementary materials, partially substituting cement with fly ash for sustainability assessment and compatibility evaluation in our study. Mechanical tests encompass compressive, flexural strength, and interlayer bonding in 3D-printed samples. Based on the results, incorporating 0.150% Polyamide (PA) fiber positively affected interlayer bonding strength and deceleration of the flow loss rate. Additionally, adding clays decreased workability and compressive strength but improved interlayer bonding and flexural properties. On the other hand, substituting 20% of cement with FA improved the flowability of the mixture and showed great compatibility with other materials during printing. Applying a cement paste layer was evaluated as a practical method for bond enhancement at the interface. Bacteria incorporation improved flexural strength but weakened interlayer bonding. However, the combination of bacteria and clays resulted in a superior improvement in mechanical properties. This study demonstrates clays and bacteria’s potential in enhancing rheological and mechanical features in cementitious fiber-reinforced mortar. Notably, this study introduces bacteria cells and sepiolite as rheology modifiers in 3D concrete printing for the first time. Additionally, it presents a novel dog-bone-shaped structure test for assessing interlayer bond performance.