Cementitious Composites Research Articles

Investigation of the macro performance and mechanism of biochar modified ultra-high performance concrete

Ultra-high performance concrete (UHPC), an extraordinary category of cementitious composites, showcases unparalleled mechanical and durability properties. Given the current disparity in carbon levels and the environmental hazards associated with cement production, various types of biochar materials have been incorporated into cement composites. This approach offers a mutually advantageous solution, effectively reducing CO2 emissions while simultaneously preserving natural resources. This study aims to evaluate the use of palm shells, a waste biomass, as a substitute for aggregate in the UHPC matrix. The investigation focused on replacing 1–40 % of sand, specifically considering apricot, date, and peach shells biochar at an 8 % replacement. A comprehensive analysis was carried out on a total of 12 combinations, encompassing a control group. For biochar-mortar admixtures, a decrease in workability and density were observed. Replacing 1 % of sand with biochar in UHPC mortar improved compressive strength, but increasing biochar dosage weakened it. Biochar-mortar was demonstrated a dual impact on drying shrinkage. Mixtures with higher biochar dosages showed a slight increase in permeability. Incorporating 1 % biochar into UHPC led to a slightly lower electrical flux value. SEM images were obtained, highlighting the compact morphological structure seen in both the control and the 1 % biochar mortar. MIP test showed nearly 1.6 times increase in the 2-dimensional porosity, from 10.49 % (control) to 16.83 % for sample which had 30 % biochar. Based on the results obtained, it could be concluded that biochar possesses the capability, which enhances the properties of UHPC mortar when used as a partial replacement for conventional fine aggregate in minor fractions.

Electromagnetic interference shielding performance and piezoresistivity of multifunctional cement composites by adopting conductive aggregates

This study explores the application of multifunctional cement composites prepared with graphene-coated conductive aggregate (Gr@Ag) and carbon fiber (CF). The electromagnetic interference (EMI) shielding effectiveness, electrical conductivity, and piezoresistive performance of cement mortars were investigated by varying the aggregate to binder (a/b) ratio and CF content. It was found that the EMI shielding effectiveness of cement mortar was enhanced by 24.8 % with the a/b ratio increased from 1.0 to 2.5, reaching 20.07 dB with a 3 mm thickness specimen. This is accompanied by significant improvements in the electrical conductivity and piezoresistive performance of cement mortars. In addition, CFs were included in cement mortars to further improve the electrical performance. Results indicate that there exists a percolation threshold, beyond which extra CF additions did not lead to further increases in the conductivity of cement mortars. The present research has illustrated the novel approach of incorporating the EMI shielding functionality into cement composites by adopting conductive aggregates, expanding the functional and smart performances towards future applications.

Enhancing self-healing properties of engineered cementitious composites through the application of super-sulfated cement

To date, no prior research has addressed the self-healing performance of engineered cementitious composites (ECC) prepared with super-sulfated cement (SSC), despite its potential to reduce carbon emissions compared to Portland cement (OPC). This paper addresses this significant research gap in the literature by exploring the influence of SSC on the recovery ability of pre-cracked ECC samples. In addition to the mechanical characterization at the sound state, an exhaustive investigation was undertaken to comprehensively assess the self-healing ability of flexural strengths, deflections, ultrasonic pulse velocity (UPV), and rapid chloride permeability (RCPT) of preloaded SSC-based ECCs. Furthermore, scanning electron microscopy (SEM), coupled with energy-dispersive X-ray (EDX) was employed to evaluate the microstructural changes and development of self-healing products within the microcracks of SSC mixtures prepared with various amounts of FA. The findings indicated that SSC-based ECC, while maintaining comparable mechanical and ductility properties, exhibited significant improvements in the recovery rates of ECC, reaching more than 27%, 7%, and 76% for flexural strength, UPV, and RCPT, respectively, compared to the OPC-based control ECC. The microstructural SEM-EDS results confirmed the enhanced precipitation of ettringite as a new self-healing product related to the inclusion of SSC in ECCs, along with the conventional C-S-H/C-A-S-H gels.

Fracture behavior and mechanical properties of engineered cementitious composites exposed to long-term sulfate and chloride environments

The fracture properties of engineered cementitious composites (ECC) exposed to dry-wet cycles in sulfate and sulfate-chloride solutions were studied by three-point bending (TPB) beams at the corrosion periods of 0, 30, 90, 130, 180, 270, and 360 days. The digital image correlation (DIC) technique was used to understand the whole fracture process. The fracture toughness and fracture energy were calculated using the proposed method, and the evolution of the horizontal strain field, displacement field, and fracture process zone (FPZ) were investigated. Meanwhile, the compressive and tensile performance of the specimens at the same corrosion periods were analyzed. The results showed that (1) Compared to water immersion, the environments of sulfate and sulfate-chloride were beneficial in improving the compressive and tensile strength, and weakening the tensile ductility. (2) With increasing the corrosion time, the evolution of the unstable fracture toughness can be distinguished into three phases: a stable phase, an increasing phase, and a rapidly decreasing phase, and the initial fracture toughness followed an increasing and then decreasing trend. The fracture energy initially decreased and tended to stabilize after 130 days. (3) By using DIC technology, as the corrosion time increased, the horizontal opening displacement at the notch tip showed a decreasing trend and stabilized after 90 days generally. The fracture path determined through horizontal displacement was well matched with the macrocrack trajectory. (4) The addition of chloride ions helped to improve the mechanical properties of ECC under long-term corrosion, such as compressive strength, unstable fracture toughness, fracture energy, and opening displacement at the notch tip. Compare to concrete, ECC exhibited greater resistance to sulfate corrosion.

Towards Eco-Friendly Waste Solutions: Environmental Impact of Engineered Cementitious Composites in Solid Waste Management

Towards Eco-Friendly Waste Solutions: Environmental Impact of Engineered Cementitious Composites in Solid Waste Management

Applicability and chemical mechanism of lightweight cement composite containing fly ash and sand for sustainable embankment

Lightweight embankment is an effective method for soft foundation treatment, while decreasing its cement usage can protect environment, save resource and reduce cost. This study aims to develop a lightweight cement composite (LC) containing fly ash and sand to provide guidance for filling the sustainable embankment. The chemical mechanism, micro-morphology, mechanical strength and workability of lightweight cement composites were evaluated through macro-micro tests, as well as life cycle assessment was performed to analyze the sustainability, and determine the optimal mixing ratio. The results showed that the moderate amount of fly ash was beneficial to enhance the mechanical strength of LC, while adding sand further improved its ductility, toughness, workability and sustainability. When the replacement rate of fly ash and sand were 10 % and 20 %, the energy absorption and fluidity of LC increased by 57 % and 7 %, and its ductility index, carbon emission and construction cost decreased by 34 %, 46 % and 35 %, respectively. Fly ash reacted with calcium hydroxide produced by cement hydration to generate more calcium silicate gels, which reduced the large pore of LC and improved its internal structure, while sand played a certain skeleton role.

Pullout behavior of polyethylene fiber from cement matrix: Effect of embedment length, matrix strength, and inclination angle

Engineered cementitious composites reinforced with polyethylene fibers (PE-ECC) exhibit the potential for high strength and toughness. To optimize the performance and tailor the properties of PE-ECC, this study focuses on analyzing the pullout behavior of polyethylene (PE) fibers from matrices through single fiber pullout tests and scanning electron microscopy analysis. One fiber type was used throughout the experiment, while three embedment lengths and three inclination angles were considered to investigate the pullout behavior from high-strength matrices. Furthermore, the pullout response from matrices with middle and low strength was examined, considering two embedment lengths. The results indicate that fibers with shorter embedment lengths exhibit lower pullout loads but higher energy absorption capacities. High matrix strength enhances adhesion and friction at the fiber-matrix interface, resulting in plumper pullout load versus slip curves. Owing to snubbing and matrix spalling effects, as the inclination angle increases, both the peak load and slip at the peak load of the inclined fibers exhibit an exponential increasing trend. Additionally, following the peak load, the pullout load of inclined fibers decreases more gradually than that of aligned fibers, and the energy absorption capacity of inclined fibers is significantly improved. Ultimately, general equations are derived for the calculation of pullout work and equivalent bond strength.

CDPM2F: A damage-plasticity approach for modelling the failure of strain hardening cementitious composites

For the use of micro-mechanics based constitutive models for fibre reinforced strain hardening cementitious composites in finite element simulations of structural components, it is required to link the crack opening at the scale of fibres to the cracking strain at the scale of structural components. We aim to establish this link by incorporating a micro-mechanics based fibre bridging stress crack opening law into a macroscopic damage-plasticity approach, which we call CDPM2F. The model is implemented in the open-source finite element program OOFEM. The model produces mesh-insensitive results and its response agrees well with experimental results for failure in tension, shear and compression reported in the literature.

Development of eco-friendly engineered cementitious composites (ECC) with both waste glass powder and aggregate: A comprehensive investigation

This study investigated the micro-macro properties of engineered cementitious composites (ECC) with both waste glass powder (WGP) and waste glass aggregate (WGA) as substitutes for binder and silica sand, aiming to achieve sustainable ECC materials and recycle waste glass in a high-value approach. The results indicate that a high volume of WGP used as a replacement for cement leads to a loose microstructure in ECC, whereas ECC prepared with 100 % WGA replacing silica sand exhibit a better microstructure compared to the reference ECC. Replacing cement with a high volume of WGP reduces the compressive and flexural strengths, but replacing silica sand with WGA increases the compressive and flexural strengths of ECC. Under tensile loading, both WGP replacing binders and WGA replacing silica sand enhance the strain capacity of ECC at substitution rates not exceeding 25 %. As the substitution rate increases, replacing 50 % of cement with WGP reduces the strain capacity and ultimate tensile strength of ECC by 18 % and 32.5 %, respectively. Nevertheless, substituting WGA for silica sand can enhance the strain capacity of ECC. Substituting WGP for the binders increases the transport properties and water-permeable porosity of blended ECC, while the replacement of silica sand with a moderate dosage of WGA reduces the water transport properties and water-permeable porosity. The simultaneous substitution of binder and silica sand with WGP and WGA, respectively, enables the production of sustainable ECC with desirable micro-macro properties. The complete replacement of silica sand and fly ash with WGA and WGP, respectively, is feasible, whereas the substitution of cement with a high-volume WGP should be limited.

Experimental study on hybrid fiber reinforced high performance concrete properties: Investigatingcomprehensive energy consumption capacity

The brittleness of concrete in tension increases with higher compressive strength, necessitating the study of cementitious composites that combine high strength and ductility. This study investigated the fresh and mechanical properties of high-strength concrete (HPC) incorporating fibers: steel, basalt, and polyethylene (PE). Hybrid fiber reinforced high performance concrete (HyFHPC) was created by tailoring mix proportions, with eight series of specimens cast, each carrying different fiber combinations alongside plain HPC as a reference. Compressive, tensile, and flexural tests were conducted, and results were analyzed. The electron microscopy techniques were employed to observe the microstructural morphology and perform elemental analysis of the composites. Findings revealed a dense HPC matrix with 1.5 % total fiber content, exhibiting uniform dispersion and ideal bonding. Digital image correlation (DIC) technique was utilized to analyze strain distribution and crack development of specimens in tension and bending, proving effective in tracking the strain and crack evolution. Statistical analysis of five influencing elements—cubic compressive strength, axial compressive strength, tensile energy dissipation, tensile fracture energy, and energy release rate—revealed Series F9 (S0.5P1) as optimal for comprehensive energy consumption performance. HyFHPC demonstrated enhanced strength, ductility, and toughness compared to HPC with mono fiber or none. The hybridization achieved positive synergy and improved reinforcing efficiency while conserving resources.

A ternary calcium silicate bone cement with high mechanical properties and good operability

The treatment of vertebral compression fractures of the spinal necessitates the use of injectable bone repair materials with the adaptive modulus of elasticity. Currently, newly developed injectable self-curing materials for minimally invasive surgery are primarily categorized into calcium phosphate and calcium silicate systems, both of which exhibit excellent biocompatibility. However, calcium phosphate bone cement lacks adequate mechanical properties and the stress does not match between bone and material. Calcium silicate cement has a long curing time, low mechanical strength, and high alkalinity. These deficiencies render them inadequate for meeting clinical requirements. Therefore, we incorporated inorganic disodium phosphate, organic polyvinyl alcohol, and solid component cerium oxide into the matrix phase of tricalcium silicate bone cement to establish a ternary self-curing hydration reinforcement system and produced an organic-inorganic composite injectable bone cement. Even though the composite bone cement has a longer setting time, it exhibited high compressive strength (61.9Mpa) and fracture strain (7.88 %), demonstrating excellent mechanical properties. Furthermore, it also demonstrates good injectable properties (86 %), anti-collapse properties, good biological activity, and outstanding antibacterial properties. The composite bone cement has great potential to develop a new injectable self-curing material to replace PMMA bone cement in clinical vertebral compression fractures.

Apoptotic effects of biodentine, calcium-enriched mixture (CEM) cement, ferric sulfate, and mineral trioxide aggregate (MTA) on human mesenchymal stem cells isolated from the human pulp of exfoliated deciduous teeth.

Preservation of primary teeth in children is highly important. Pulpotomy is a commonly performed treatment procedure for primary teeth with extensive caries. Thus, biocompatibility of pulpotomy agents is highly important. Biodentine, calcium enriched mixture (CEM) cement, ferric sulfate, and mineral trioxide aggregate (MTA) Angelus are commonly used for this purpose. Thus, this study aimed to assess the apoptotic effects of Biodentine, CEM cement, ferric sulfate, and MTA on stem cells isolated from the human pulp of exfoliated deciduous teeth. In this in-vitro, experimental study, stem cells isolated from the human pulp of exfoliated deciduous teeth were exposed to three different concentrations of Biodentine, CEM cement, ferric sulfate, and MTA for different time periods. The cytotoxicity of the materials was evaluated by flow cytometry using the annexin propidium iodide (PI) kit. Data were analyzed by ANOVA and Tukey's test at P<0.05 level of significance. All four tested materials induced significantly greater apoptosis compared with the control group. The difference in cell apoptosis caused by the first concentration of ferric sulfate and MTA was not significant at 24 hours. In other comparisons, the cytotoxicity of ferric sulfate was significantly lower than that of other materials. Biodentine showed higher cytotoxicity than MTA at first; but this difference faded over time. The cytotoxicity of CEM cement was comparable to that of MTA. The highest cell viability was noted at 24 hours in presence of the minimum concentration of ferric sulfate. The lowest cell viability was noted at 72 hours in presence of the maximum concentration of CEM cement. In comparison with other materials, ferric sulfate showed minimum cytotoxicity; the cytotoxicity of the three cements was comparable. It appears that the concentration of ferric sulfate and the composition of cements are responsible for different levels of cytotoxicity.

Co-encapsulation of bacterial spores and nutrients by polyethylene glycol for self-sealing cementitious composites

Co-encapsulation of endospores and nutrients in self-healing concrete can mitigate their negative effects on cement hydration. However, the current approaches of co-encapsulation for bacteria-based self-healing cementitious composites could cause pre-consumption of nutrients before cracking or a restricted release of nutrients after cracking. To address the nutrient release issue, polyethylene glycol (PEG) with high solubility was applied as an alternative to co-encapsulation of bacterial spores and nutrients, subsequently coated by an epoxy/sand protective shell herein. The core-shell structured capsules rapidly released the encapsulated substances within approximately 4 h and protected the encapsulated endospores in alkali environments. Due to the co-encapsulation, hydration retardation was avoided, leading to less severe reductions in compressive strength. After cracking, although the released amount of nutrients decreased after encapsulation, the closure of cracks below 300 μm was improved in the presence of capsules, thus water tightness was recovered more significantly. A model was developed to simulate sealing evolutions, and the modelling results were generally consistent with the experimental results.

The Mechanical Characteristics of Enhanced Bendable Concrete By Polyvinyl Alcohol Fibers

Abstract Engineered Cementitious Composites (ECC), which are alternatively referred to as Bendable Concrete, is a class of Ultra-ductile cementitious composites characterized by their remarkable ductility and polyvinyl alcohol fiber (PVA) fiber reinforcing. These composites are designed to regulate cracks width effectively. This study investigates the influence of matrix flowability, fiber mixing technique, and curing conditions on the mechanical characteristics of Bendable Concrete utilizing high-tenacity (PVA) fibers. This study examined the compressive strength of Bendable concrete, which ranged from 60 to 70 MPa, with a strain exceeding 3%. To regulate the flowability of the matrix, high range water reducing admixture (HRWRA) was added to a matrix with a weight ratio of silica fume was 10% by weight of cement, a weight ratio of water to cementitious material of 0.3, also polyvinyl alcohol acetate solution (PVAS). The primary parameter under investigation in this study is the changing volume fraction dose of (PVA) fiber, while the remaining materials of the combination were held constant. Four different (PVA) fiber percentages (0.5, 1.0, 1.5, and 2.0)% were adopted by volume of cement. Three (cubes, cylinders, and prisms) were fabricated and cast from each mixture and tested at the ages (7, 28, and 90) days for investigated (compressive, splitting tensile, and Modulus of Rupture) strength, respectively. The results of the tests demonstrated that the proportion of fiber substantially affects the strengths, where both the Compressive strength and Splitting tensile strength were increased with the increment of fiber content until 1% of (PVA) fiber . In comparison, the higher Modulus of Rupture was abtained at 2% (PVA) fiber.

Assessing Biocompatibility of Composite Cements by Peri/Intramuscular and Subcutaneous Implantation in Rats.

This study's goal was to evaluate the biocompatibility of two composite cements over a 90-day period by analyzing the individuals' behavior as well as conducting macroscopic and histological examinations and Computed Tomography (CT) scans. We conducted the cytotoxicity test by placing the materials subcutaneously and peri/intramuscularly. Days 30 and 90 were crucial for our research. On those days, we harvested the implants, kidneys and liver to search for any toxic deposits. The biomaterial's uniformity, color and texture remained unaltered despite being in intimate contact with the tissue. Although a slight inflammatory response was observed in the placement location, we observed an improved outcome of the interaction between the material and its insertion area. There were no notable discoveries in the liver and kidneys. According to the obtained results, the biomaterials did not produce any clinical changes nor specific irritation during the research, demonstrating that they are biocompatible with biological tissues.

Performance of high-strength green strain-hardening cementitious composites incorporating CSA/CAC cements and GGBS

Strain-hardening cementitious composites (SHCCs) possess crack control and durability properties. In the pursuit of reducing CO2 emissions and addressing potential issues of slow strength development for SHCCs with pozzolans, the objective of this study was to develop high-strength green SHCCs (HSG-SHCCs) that exhibit improved early strength, drying shrinkage, and environmental friendliness. A ternary binder system was proposed, comprising of ground granulated blast furnace slag (GGBS), ordinary Portland cement (OPC), and either calcium sulfoaluminate cement (CSA) or calcium aluminate cement (CAC). The fresh, mechanical, and durability properties of the proposed HSG-SHCCs were experimentally investigated. Additionally, the microstructures and chemical phases of the developed CSA/CAC-GGBS-OPC ternary binder system were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed that the developed HSG-SHCCs demonstrated 6-hour and 28-day strengths of up to 11 MPa and 110 MPa, respectively. The CSA/CAC-based ternary binder system also exhibited enhanced durability and improved drying shrinkage. However, the inclusion of CSA and CAC in HSG-SHCCs could lead to a reduction in tensile performance, specifically in strain capacity. The main hydration products of the CSA/CAC-GGBS-OPC ternary binder system were C-S-H, ettringite, gibbsite, and calcium hydrate. In addition to the fresh, mechanical, and durability properties, the environmental impact of the developed HSG-SHCCs was also assessed. The results indicated that a 30 % replacement of OPC with CSA cement in the HSG-SHCC mix notably improved the trade-off among CO2 emissions, compressive strength, and tensile cracking resistance.

Compressive strength, chloride-ion-penetration resistance, and crack-recovery properties of self-healing cement composites containing cementitious material capsules and blast-furnace-slag aggregates

Blast-furnace-slag aggregate (BFSA), a by-product of the steel industry, is an eco-friendly natural, aggregate substitute used in mortar and concrete. However, research on self-healing cement composites using BFSA is rare. In this study, the compressive strength, chloride-ion-penetration resistance, and crack-recovery properties of self-healing cement mortar samples prepared using cementitious material capsules (CMC) and BFSA of different ratios were examined and compared to a control sample. The test samples were: Control; C05B00 (5 % CMC and 0 % BFSA); C05B25 (5 % CMC and 25 % BFSA); C05B50 (5 % CMC and 50 % BFSA); C10B00 (10 % CMC and 0 % BFSA); C10B25 (10 % CMC and 25 % BFSA); and C10B50 (10 % CMC and 50 % BFSA). The compressive-strength recovery rate of the control stopped increasing after 28 days and was approximately 110 % on day 56 – that of C10B50 was approximately 121 %, (∼10 % greater than that of the control) and continued to increase even after 56 d. The chloride-ion-penetration resistance of C10B50 was excellent; the 28-day total charge was approximately 5858 C (∼ 40.2 % lower than that of the control). The crack-recovery rates, on day 28, of C05B50 and C10B25 were 71 % and 70 %, respectively (∼ 29–30 % higher than that of the control).

Characteristic and optimization of ferrite-rich sulfoaluminate-based composite cement suitable for cold region tunnels

Characteristic and optimization of ferrite-rich sulfoaluminate-based composite cement suitable for cold region tunnels

The Effect of Carbon Nanotubes and Carbon Microfibers on the Piezoresistive and Mechanical Properties of Mortar

Sustainability, safety and service life expansion in the construction sector have gained a lot of scientific and technological interest during the last few decades. In this direction, the synthesis and characterization of smart cementitious composites with tailored properties combining mechanical integrity and self-sensing capabilities have been in the spotlight for quite some time now. The key property for the determination of self-sensing behavior is the electrical resistivity and, more specifically, the determination of reversible changes in the electrical resistivity with applied stress, which is known as piezoresistivity. In this study, the mechanical and piezoresistive properties of mortars reinforced with carbon nanotubes (CNTs) and carbon micro-fibers (CMFs) are determined. Silica fume and a polymer with polyalkylene glycol graft chains were used as dispersant agents for the incorporation of the CNTs and CMFs into the cement paste. The mechanical properties of the mortar composites were investigated with respect to their flexural and compressive strength. A four-probe method was used for the estimation of their piezoresistive response. The test outcomes revealed that the combination of the dispersant agents along with a low content of CNTs and CMFs by weight of cement (bwoc) results in the production of a stronger mortar with enhanced mechanical performance and durability. More specifically, there was an increase in flexural and compressive strength of up to 38% and 88%, respectively. Moreover, mortar composites loaded with 0.4% CMF bwoc and 0.05% CNTs bwoc revealed a smooth and reversible change in electrical resistivity vs. compression loading—with unloading comprising a strong indication of self-sensing behavior. This work aims to accelerate progress in the field of material development with structural sensing and electrical actuation via providing a deeper insight into the correlation among cementitious composite preparation, admixture dispersion quality, cementitious composite microstructure and mechanical and self-sensing properties.

Properties of Cementitious Composite Reinforced with Recycled Pulp from Beverage Cartons

This study presents a comprehensive evaluation of the effects of the refining level of recycled pulp from beverage cartons (RPBC) on the properties of its cementitious composite. The RPBC with various freeness levels, ranging from 400 to 650 mL of the Canadian Standard Freeness test method (CSF), was prepared using a high-speed fruit blender. The specimens were formed by the slurry de-watering method with 8wt% fiber content and mortar matrix with a sand-to-cement ratio of 1:1. The key findings reveal that the cementitious composites reinforced with the RPBC exhibited a maximum value of flexural strength of 11.17 MPa and the freeness of 550 mL CSF. The fracture toughness values of the RPBC composites were significantly improved compared to that of the control specimen. However, the values decreased by about 14% to 20 % as the freeness reduced from 650 to 400 mL CSF. The bulk density and porosity of the RPBCC were not significantly affected by the freeness of RPBC.