Cementitious Composites Research Articles

Water deironing through the reagent and biosorption treatment and utilization of iron-rich sediments and biosornets in cement production

ABSTRACT The processes of reagent and sorption removal of iron ions from water were investigated and the efficiency of deironing was evaluated. Lime and biosorbents based on walnut shells were used through experiments. The range of iron ions concentrations from 2 to 100 mg/L was studied. The efficiency of deironing is reached maximum efficiency during biosorbtion. In order to create resource-efficient technologies, it is important to develop effective methods of sludge and spent sorbents utilisation. The sediments formed as a result of reagent and sorption purification of water from iron were utilised in the composition of cement with the consumption 3%. The effect of additives application in cement production was evaluated according to the following properties: normal density, coefficient of water separation, time of hardening, compressive strength at the age of 2 and 28 days.

Effect of additional Al sources on early-age strength of fly ash-based geopolymer containing calcium carbide residue and Glauber’s salt as activators

Alkali-activated materials are more environmentally friendly than cementitious composites and are used in the construction and building sector. However, their intrinsic low early strength under ambient temperatures hinders their practical applicability. More research is needed on the possibilities of increasing early strength at ambient temperatures. In this study, aluminum sulfate (AS) was used as an additional aluminum source to improve the early-age properties of fly ash (FA)-based geopolymers incorporating calcium carbide residue (CCR) and Glauber’s salt (GS) as activators. XRD, TG, SEM, ICP and isothermal calorimetry analyses were carried out to characterize the phase composition, microstructure and hydration process of the prepared materials. The results showed that the 1d strength of AS1-CCR10 was increased by 260.7 % compared with the control material, and the effect on the late strength was negligible. The relative content of AFt increased by 2.97 %, creating a more compact microstructure. During the extraction process, insufficient dissolved Al3+ in the composite led to a decrease in initial strength. In the hydration process, the induction period of AS1-CCR10 was advanced by 40.92 % and that of t50 was advanced by 57.74 %, which accelerated the early reaction rate. However, the Krstulovic-Dabic model could not accurately describe the initial stage of the hydration reaction of composite materials. This study is helpful to broaden the utilization of geopolymer composites and provide a theoretical basis for the preparation and reaction mechanism of alkali-activated materials.

Expanded vermiculite acting as artificial flaws to enhance the tensile properties of high-strength engineered cementitious composites

In this study, an expanded vermiculite (EV) was proposed to substitute silica sand, and act as artificial flaws in high-strength engineered cementitious composites (ECC) to improve its ductility. Experimental and analytical investigations were conducted on the mechanical behavior, micromechanical analysis and microstructural analysis of ECC from macro-, meso-, and micro-scales. The results demonstrated that the inclusion of EV reduced the compressive strength of ECC composites from 77.6 MPa to 60.2 MPa, although this does not hinder its role as a constituent of high-strength concrete (60 MPa). However, compared with that of 2.56 % in reference ECC mixture, due to the EV addings, the strain capacity of ECC mixtures was increased up to 8.22 %. On the other hand, incorporating fine EV particles (0.15 mm, 0.42 mm, and 2 mm) was positive to the tensile strength of ECC mixtures with a 23 % improvement, while the addition of coarser EV (1–3 mm and 3–5 mm) led to an 8 % reduction. At microscale, the incorporation of EV reduced the critical flaw size and increased the flaw size, significantly increased the number of active flaws, as a result, more micro-cracks were initiated, and thus greatly improving ductility of ECC.

Eco-friendly strain-hardening cementitious composites with recycled PET fine aggregate: Mechanical behavior and environmental benefits

The production of strain-hardening cementitious composites (SHCC) heavily relies on natural fine aggregates. This study employs recycled PET fine aggregates to prepare PET-modified SHCC (P-SHCC). The physical properties and mechanical behavior of P-SHCC with different PET volume replacement ratios (0 %, 25 %, 50 %, 75 %, and 100 %) are experimentally investigated. The microstructures were examined to analyze the impact of additional defects induced by the interfacial transition zone between recycled PET and cementitious matrix. The multiple cracking behavior was discussed based on the crack parameters. The results indicate that the incorporation of PET significantly enhances the ultimate strain and crack control capability of SHCC while reducing the material's density. Furthermore, energy consumption, carbon emission, and comprehensive environmental indexes were employed to analyze the environmental benefits. The findings demonstrate the feasibility of preparing SHCC with recycled PET fine aggregate, particularly in enhancing the strain capacity and environmental benefits.

Multi-Objective Optimization and Mechanical Properties Analysis of Steel-PVA Hybrid Fiber-Reinforced Cementitious Composites.

When steel fiber and PVA fiber produced in China and PVA fiber made in Japan are prepared according to the appropriate proportions, the mechanical properties of hybrid fiber-reinforced cementitious composites (HFRCC) are better, which is beneficial to cost control and has wide application prospects. The effects of the volume content of steel fibers and the volume substitution rate of PVA fibers on the tensile strength, compressive strength, and flexural strength of HFRCC were analyzed using the factor optimization method and principal component analysis (PCA). Through the principal component analysis of HFRCC, a mathematical model for comprehensive performance evaluation was established, and a multi-objective optimization was carried out. The results show that compared with the matrix, the tensile strength, compressive strength, and flexural strength of concrete increase significantly when the volume content of steel fibers is 0.2-0.4% and the volume substitution rate of domestically produced PVA fibers in China or PVA fibers produced in Japan is 50-100%. The maximum cost reduction is 88.25%, and the strength index of HFRCC can reach the optimum; the weights of each factor on the performance of HFRCC were obtained through mathematical statistics. Combined with a variable correlation analysis, these indicators should be noted when optimizing the performance of HFRCC. The research results can provide a basis for the preparation of HFRCC.

Strategies for reusing multiple recycled powders: Evaluating the mechanical performance and sustainability of Engineered Cementitious Composites (ECC)

Engineering Cementitious Composites (ECC) are fibre-reinforced cementitious materials with excellent tensile strain capacity. Recycling powder from building and demolition waste can improve the ecological efficiency of concrete and reduce the cost of raw materials. In this study, recycled glass powder (RGP) was used to partially replace traditional cement. Based on using a 1:1 replacement of recycled brick powder (RBP) and recycled concrete powder (RCP) for fine aggregates, two sets of variables were set: the RGP substitution rate (10 %, 15 %, 20 %, and 25 %) and RGP particle-size range (38–75 μm, 75–150 μm, and 150–300 μm). Comprehensive material testing and mechanical experiments were conducted, including X-ray diffraction analysis, thermogravimetric analysis, shrinkage tests, uniaxial compressive tests, uniaxial tensile tests, and scanning electron microscopy. The results indicated that fully substituting quartz sand with RBP and RCP enhanced the ECC performance. Incorporating RGP significantly improved the ultimate tensile strain and crack-propagation ability of the ECC while reducing the 90-d shrinkage rate. The 28-d compressive strength and tensile strength have some loss, but can meet the strength requirements. SEM showed that incorporating RGP weakened the bonding strength of the fibre matrix, making it easier for the fibres to be pulled out. By evaluating the experimental results, the mix ratio of a 20 % substitution rate and 75–150-μm size was selected. A material-sustainability indicator (MSI) analysis of the raw materials and production process of RGP-ECC was performed. The embodied energy, carbon emissions, and economic indices were reduced to a certain extent, thereby improving the ecological efficiency of concrete.

Development of multifunctional cementitious composite using biochar

The global emphasis on sustainability has increased the demand for eco-friendly construction materials, with biochar emerging as a promising additive for concrete. It enhances mechanical properties, reduces greenhouse gas emissions, and adds advanced multifunctionalities. Traditionally, achieving multifunctionality in cementitious composites involves using costly conductive fillers like carbon fibers and carbon black, which pose dispersion and health challenges. In contrast, biochar offers a cost-effective and carbon-negative alternative. Its high carbon content enables multifunctionality and sensing capabilities when integrated into cement. This study explores the multifunctional properties of biochar-based cementitious composites, focusing on self-sensing abilities, carbon sequestration, and their chemical and mechanical properties. Results indicate that adding biochar at 5 %, 10 %, and 15 % levels enhances compressive strength by 16.62 %, 46.20 %, and 51.17 %, respectively, while reducing ductility due to its porous nature at higher concentrations. Moreover, increasing biochar content from 5 % to 10 % correlated strain with fractional changes in resistivity (R2 = 0.99), highlighting its potential in self-sensing and structural health monitoring applications. BC15 samples also exhibited a 70 % higher CO2 absorption rate compared to controls, showcasing biochar's ability to improve concrete's functionalities and environmental performance. This study supports the wider adoption of biochar in construction to advance sustainable construction practices and contribute to global carbon reduction goals.

Assessment of the Mechanical and Microstructural Performance of Waste Kraft Fibre Reinforced Cement Composite Incorporating Sustainable Eco-Friendly Additives

This study investigates the influence of limestone powder and metakaolin as sustainable eco-friendly additives on the properties and behavior of cementitious composite boards, with a focus on mechanical strength, physical properties, and microstructural characteristics. The experimental investigation begins with the characterization of the raw materials, including limestone powder, and metakaolin, to assess their particle sizes, elemental composition, and microstructural features. Cement composite boards were fabricated using an innovatively developed lab-simulated vacuum dewatering process, by varying the proportions of limestone powder and metakaolin as partial replacements for cement, along with waste kraft fibres as reinforcement. Mechanical testing was conducted to evaluate the flexural strength and behaviour of the composite boards according to standardized procedures. A microstructural analysis was performed using scanning electron microscopy (SEM) to examine the effect of additives on the cementitious matrix, fibrematrix interaction, and hydration products. The findings from the experimental study reveal insights into the influence of limestone powder and metakaolin on the mechanical properties and microstructure of waste kraft fibre-reinforced cement composite boards. Our analysis of the results shows that adding 9% limestone powder as partial cement replacement produces a 24% and 50% enhancement in flexural strength at 7 and 28 days of hydration, while that of metakaolin as partial cement replacement was optimum at 6% with an enhancement of 4% and 36%, respectively, at 7 and 28 days of hydration. The implications of these findings for the development of sustainable cementitious composite are discussed, including the potential benefits of using limestone powder and metakaolin as supplementary cementitious materials in waste kraft fibre-reinforced cement composite boards. Finally, recommendations for optimizing additive proportions are also provided to enhance the understanding and application of these materials in the construction and building industries.

Synergy performance of hybrid fiber-reinforced ultra-high-performance cementitious composites with low fiber contents

This study aims to assess the synergistic tensile performance resulting from the hybridization of long and short fibers. Three types of long steel,fibers, i.e., twisted, hooked, and smooth fibers, along with two types of short fibers, i.e., smooth and polyamide fibers, were incorporated into ultra-high-performance concrete (UHPC) at a total volume content of 1.5%. To predict the tensile resistance of the hybridizations, various machine learning models, including artificial neural network (ANN), decision tree (DT), random forest (RF), and support vector machine (SVM), were applied by utilizing a significant number of collected experimental results. Experimental findings demonstrated that the hybridization of long and short fibers effectively enhanced tensile resistance compared to mono fibers. These hybridizations exhibited negative synergy factors in post-cracking strength but positive synergy factors in both strain capacity and specific work to fracture. Predictions using machine learning models revealed that the RF model exhibited outstanding performance in predicting the tensile resistance of the hybridizations. Furthermore, the compressive strength of the matrix was found to be the most important factor affecting post-cracking strength, whereas fiber length had the most substantial impact on the strain capacity.

Water proofing performance assessment of hydrophobic agent-based Portland cement concrete: A multi-dimensional experiment approach

Heavy rainfall led to excessive water infiltration and saturation in the concrete surfaces, resulting the dampness. This can adversely affect the aesthetical view, durability and strength of the concrete over time. However, hydrophobic cement is a specialized type of cement that has been developed to exhibit resistance to water penetration in the cement composite, which enhance the durability of concrete structure. In this research, hydrophobic Portland cement concrete (HPCC) specimens were assessed considering the mechanical strength properties, water absorption by different methods, and microscopic observations of hydration products. It was revealed that the compressive strength (CS) of HPCC concrete achieved around 28.7 MPa and 35.6 MPa at 7d and 28d, respectively having water to cement (W/C) proportion 0.45. The splitting tensile strength of HPCC samples having W/C 0.45 also found around 1.98 MPa and 2.43 MPa at 7d and 28d, respectively which values were higher as compared to control OPC specimens. In addition, HPCC concrete specimens showed capillary water absorption at 90d for 1D, 4D and 6D about 0.25 %, 0.36 %, and 0.39 %, respectively which was lower than that of PCC concrete samples. Moreover, the HPCC concrete plate specimens shown significantly lower water penetration by static vertical water pressure, for example concrete plate having 100 mm thickness presented around 2.6 mm water absorption depth at 90days. Furthermore, very few micro-pores were observed by SEM (scanning electron microscopy) in the microstructures of HPCC, whereas micro-cracks were not visible in the focus area. However, the findings might be applied in the construction sectors to protect the exterior building walls, roof floor slabs and plastering the concrete surfaces from dampness.

Evaluation of Biocomposite Cements for Bone Defect Repair in Rat Models.

Repairing or reconstructing significant bone defects is typically challenging. In the present study, two composite cements were used as scaffolds in a sub-critical femoral defect in rats. A control group and two experimental batches were used to compare the outcomes. This research aimed to investigate the osteogenic potential and toxicological tolerance of the bioproducts through histopathology and computed tomography imaging analysis at 14, 28, 56, and 90 days post-implantation. The biomaterials used in the investigation consisted of a 65% bioactive salinized inorganic filler and a 25% weight organic matrix. The organic part of the biomaterial was composed of Bis-GMA (bisphenol A-glycidyl methacrylate), UDMA (urethane dimethacrylate), HEMA (2-Hydroxyethyl methacrylate), and TEGDMA (triethylene glycol dimethacrylate), while the inorganic filler was composed of silica, barium glass, hydroxyapatite, and fluor aluminosilicate glass. The first findings of this research are encouraging, revealing that there is a slight difference between the groups treated with biomaterials, but it might be an effective approach for managing bone abnormalities. Material C1 exhibited a faster bone defect healing time compared to material C2, where bone fractures occurred in some individuals. It is unclear if the fractures were caused by the presence of the biomaterial C2 or whether additional variables were to blame. By the end of the research, the mice appeared to tolerate the biomaterials without exhibiting any inflammatory or rejection responses.

Physical & mechanical properties of pervious concrete incorporating municipal solid waste incineration bottom ash

Municipal solid waste incineration bottom ash (BA) as a cementitious substitute in pervious concrete constitutes a viable strategy for waste recycling and carbon emission mitigation. Nonetheless, the resultant alterations in the cementitious matrix composition and the inter-aggregate macro-porous structure induced by BA incorporation still need to be explored, limiting a thorough understanding of the mechanical behavior and permeability. Macroscopic tests were employed to investigate the impact of BA and compaction densities on the physical and mechanical properties. The effects of BA on the hydration products were analyzed using X-ray diffraction (XRD) and thermogravimetric analysis (TG) methods. The results reveal that at a density of 2190 kg/m³, BA has minimal effect on the interconnected porosity and permeability. However, as the density increases, a higher BA substitution ratio leads to a narrowed pore distribution and a significant reduction in permeability. Furthermore, a power-function relationship exists between the compressive strength and dynamic modulus of elasticity. At a 15 % substitution ratio, a slight decrease in hydration products was observed, resulting in a minor reduction in compressive strength. Concurrently, a linear relationship was established between the proportion of tiny pores (less than two mm2) and the relative compressive strength. Considering both permeability and mechanical performance, pervious concrete with a density of 2310 kg/m3 and containing no more than 10 % BA meets the requirements of the CJJ/T135-2009 standard. These findings provide a scientific basis for the mix design of pervious concrete incorporating BA.

Mechanical properties of cementitious metallic hollow sphere composite under compression

This study presents a novel cementitious metallic hollow sphere composite by integrating metallic hollow spheres (MHS) into a cement matrix. Experimental results show that while MHS reduce the stiffness and strength of cement matrix, they enhance deformability and energy absorption. Adding 0.5% polypropylene fibers significantly improves mechanical properties and changes failure mode from brittle to ductile. This work offers insights into MHS materials in civil engineering.

The Influence and Mechanism of Curing Methods and Curing Age on the Mechanical Properties of Yellow River Sand Engineered Cementitious Composites.

This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in Engineered Cementitious Composites (ECC). With an annual accumulation of approximately 400 million tons in this region, YRS presents a substantial resource. ECC specimens with 100% YRS replacement with quartz sand were subjected to various curing methods: natural, steam, standard, and sprinkler. Extensive mechanical testing including flexural, compressive, uniaxial tensile, and four-point flexural tests was conducted. Additionally, Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses investigated microscopic mechanisms influencing macroscopic mechanical properties. Finally, the mechanical properties of the YRS-ECC test block after 14 days of standard curing and the traditional sand ECC test block were compared and analyzed. The results indicate that ECC specimens with 100% YRS substitution under natural curing show an optimal ultimate tensile strain of more than 4%, providing the best resistance to the reduction in ultimate flexural load and deflection due to aging. Steam curing enhances flexural and compressive strength, achieving an ultimate flexural load of 5 kN and a maximum deflection of 4.42 mm at 90 days. SEM analysis revealed lower C-S-H gel density under natural curing and higher under steam curing, enhancing fiber pull-out in steam-cured specimens. The MIP tests demonstrated that natural curing had the highest porosity (32.86%) and average pore size (51.69 nm), whereas steam curing resulted in the smallest average pore size, with 44% of pores under 50 nm. Compared with traditional sand, it is found that the ultimate bending load and deflection of YRS-ECC are 5.7% and 9.4% higher than those of traditional sand ECC, respectively, and its ultimate tensile strength and strain are also improved. These findings highlight YRS as a sustainable alternative to natural sand in ECC, with natural curing proving the most effective for superior mechanical performance, including tensile strain, crack resistance, and durability.

The Changes in the Inner-Structure and Mechanical Strength of the Composite Cement Materials and Silica-Carbon Nanotube-Nylon 66 Electrospun Nanofibers.

This study presents the feasibility of improving some selected mechanical strengths and the inner-structural analyses of cement matrix by electrospun nanofibers containing nylon 66, nanosilica, and carbon nanotube. The hybrid electrospun nanofibers were fabricated and mixed into ordinary Portland cement. From the mechanical strength test results, the hybrid nanofibers have shown their role in improving the tensile, compressive, and toughness behavior of the mixed cement material. The improvements of 62%, 38%, and 69%, respectively, were observed compared to those of the control paste. The novelty of the surface and inner structure of the hybrid fibers, as well as the modified cement matrix, were observed by the scanned images from electron microscopes. Besides, the additional pozzolanic reaction between the generated calcium hydroxide and the attached silica was clarified thanks to the results of energy dispersive spectroscopy, X-ray diffraction, and thermal gravimetric analysis. Finally, the consistency between mechanical strength results and inner-structure analyses showed the potential of the proposed fiber to improve cement-based materials.

MXene nanosheets magic: Unveiling the dual effect of strength and ductility enhancement in strain hardening cementitious composites

The aim of this study was to modify strain hardening cementitious composite (SHCC) using MXene nanosheets to further enhance its strength and ductility. The results showed that the addition of 0.03 wt% MXene nanosheets increased the compressive strength and tensile strain of SHCC by 18.04 % and 88.18 %, respectively. The mechanism of MXene nanosheets in improving the mechanical properties of SHCC was revealed by single fiber pullout test, micromechanical analysis, microstructure analysis and finite element analysis. Firstly, MXene nanosheets fill the pores inside the matrix, reduce the porosity of the matrix, disperse the stress, and inhibit the crack propagation, thus improving the compressive properties of SHCC. Secondly, when MXene nanosheets adhered to the fiber surface, they modified the interfacial properties between the fiber and the matrix, preventing fiber pullout and consequently improving the tensile ductility of SHCC.

Shear strengthening of simply-supported deep beams with openings incorporating combined steel-reinforced engineered cementitious composites and externally bonded carbon fibre-reinforced polymer sheets

Shear strengthening of simply-supported deep beams with openings incorporating combined steel-reinforced engineered cementitious composites and externally bonded carbon fibre-reinforced polymer sheets

Thermal, electrical, and mechanical performances of ultrahigh-performance cementitious composites with multiwalled carbon nanotubes

This study examines the influence of multiwalled carbon nanotubes (MWCNTs) on cementitious composites, specifically focusing on the fabrication of multifunctional cementitious composites known as ultrahigh-performance cementitious (UHPC) composites. Key properties such as compressive strength, thermal performance, and electrical resistance were examined with varying MWCNT contents, curing methods, curing duration, and supply voltage. The effects of the incorporation of MWCNTs on the hydration reactions of the cementitious composites were analyzed using field-emission scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction. The study revealed that MWCNT UHPC composites can achieve a maximum ultrahigh strength of 120.8 MPa. Additionally, the incorporation of MWCNTs enabled the composites to reach a maximum surface temperature of 90.6 °C during heating. Furthermore, the power consumption of MWCNT UHPC composites was found to be predictable based on the curing type and the duration of curing. Notably, the hydration reactions in MWCNT UHPC composites remained unaffected by the MWCNT content. The findings emphasize the potential of multifunctional MWCNT UHPC composites by offering exceptional strength, heating capabilities, and electrical performance in construction materials.

PET particles modify strain hardening cementitious composites: An approach to introduce defects to enhance deformation capacity

Enhancing deformation capabilities remains a critical direction in the research of Strain-Hardening Cementitious Composites (SHCC). This investigation introduces Polyethylene Terephthalate (PET) particles as a novel method to induce micro-defects within SHCC, aiming to reduce the material's initial crack strength and improve its deformability. Through the exploration of various PET particle volumetric substitutions for traditional aggregates, the development of PET particle-modified SHCC (PMSHCC) was achieved. The paper examines the impact and mechanisms of different PET volumetric substitution rates (0 %, 5 %, 10 %, 15 %, 20 %, and 25 %) on the workability, axial compression strength and tensile properties of PMSHCC. By employing Digital Image Correlation techniques, the progression of crack width and density in PMSHCC under tensile load was documented, facilitating an analysis of the influence mechanisms of varying PET volumetric substitution rates on the tensile strain-hardening behavior of PMSHCC. The findings indicate that the increased Interfacial Transition Zone (ITZ) thickness between PET particles and the cement matrix, combined with the lower elastic modulus of PET particles compared to the cement matrix and quartz sand, collectively contribute to a reduction in tensile initial crack strength and an enhancement in ultimate tensile strain of PMSHCC. Within the examined range, an increase in the PET volumetric substitution rate significantly improves the ultimate tensile strain of PMSHCC by up to 76.0 %, with a minimal reduction in tensile strength of only 3.99 %. Moreover, the study proposes a tensile linear strengthening elasto-plastic model for PMSHCC incorporating the PET substitution rate, enabling accurate prediction of the material's tensile stress-strain behavior. These findings not only offer a novel pathway for the utilization of waste plastics but also provide significant insights for enhancing the deformability of SHCC.

The experimental and numerical simulation of interface shear behavior between ECC and coal gangue concrete

Composite concrete structures are designed to integrate various concrete types at different levels, thereby improving their shear properties. In this paper, the effects of the interfacial keyway, reinforcement ratio, and pouring sequence on the shear strength of concrete-coal gangue concrete interface are studied by experiments and analyses. A total of 10 specimens were made, and the push-off test was carried out. Nonlinear finite element simulation was carried out using ABAQUS, and the influence of keyway angle on crack development was studied based on the extended finite element method (XFEM). It is found that the remarkable tensile and crack stability of engineered cementitious composites (ECC) has a positive effect on the shear strength of the ECC-coal gangue concrete interface. The ultimate shear strength of the interface and the ductility of the interface under shear load are significantly improved by interfacial shear reinforcement. The introduction of an interfacial keyway improves the shear strength of the concrete interface, and the number of keyways has the most significant effect on the interfacial shear strength. The angle between the crack propagation direction and interface will increase with the increase of keyway angle, the simulation results are in good agreement with the experiments.