Cementitious Composites Research Articles

Modification Mechanism of Glass Fibers on Ordinary Portland Cement and Sulphoaluminate Cement Composites

The problems of easy cracking, high brittleness, and low bond strength of ordinary Portland cement and sulphoaluminate cement (OPC-SAC) composites limit their application as rapid repair materials. In this study, glass fibers (GFs) were added to OPC-SAC composites with the content of 0.0–1.5% to improve their properties. Fluidity, mechanical properties, bond properties, and drying shrinkage properties were researched, and their microstructure was characterized by SEM and ICT. Hydration products at different curing ages were studied by XRD and FTIR. The results showed that GFs improved the mechanical properties of OPC-SAC composites. The 28 d flexural strength, compressive strength, and bond strength of specimens with 0.5% GFs reached maximum values, increasing by 22.1%, 12.1%, and 82.9%, respectively, compared with the control group without GFs.. GFs significantly inhibited the drying shrinkage of composites, and the inhibitory effect was magnified with the content of GFs. Adding 0.5% of GFs could reduce the porosity of specimens, decrease the volume proportion of pores (>10 mm3), and refine the pore structure. In summary, 0.5% is recommended as the optimal content of GFs to be added into the OPC-SAC composites.

Improved performance of coconut fiber and quartzite waste cement composites using accelerated carbonation.

The use of vegetable fibers and mining waste has shown promising results for the production of cementitious composites with outstanding ecological parameters. However, the basic pH of the cement matrix promotes degradation of the fibers, which affects their mechanical properties. To overcome this incompatibility, accelerated carbonation is suggested, in which decreasing the pH of the cementitious matrix can also increase the durability of the composites. Therefore, the aim of this study was to investigate the effects of accelerated carbonation on the physical-mechanical properties of coconut fiber-cement. The composites were produced by extrusion using high early-strength cement, coconut fibers, chemical additives, and different percentages of quartzite (0, 25, 50, 75, and 100%) as a substitute for limestone. In the second stage, composites made with 100% quartzite were subjected to accelerated carbonation for 0, 6, 12, and 24 h. The effect of accelerated carbonation was evaluated via physical, mechanical, thermogravimetric, and microstructural tests. Accelerated carbonation resulted in a 6% reduction in apparent porosity after 12 h of exposure and an increase in the toughness of the composites from 2.18 to 3.69 kJ/m2 after 12 h of carbonation (an increase of 69.3%). The results thus indicated that the complete replacement of limestone with quartzite waste and curing under accelerated carbonation have strong potential for the production of lighter, stronger, and more sustainable fiber-cements, for which the best carbonation time is 12 h.

A State-of-the-Art-Review on Performance RC Beams with Openings

The inclusion of web openings in reinforced concrete (RC) beams has become increasingly necessary to accommodate utility services like electrical wiring, plumbing, HVAC systems, and network cables. However, these openings significantly influence both the serviceability and strength of RC beams. In the service stage, they reduce stiffness, leading to increased deflection. At the ultimate stage, they cause stress concentrations due to the disruption of stress flow around the opening area. This geometric discontinuity can lead to premature failures if not properly addressed. Researchers have proposed various methods to counteract the reduction in strength and stiffness caused by openings. This paper reviews recent developments in the behavior and strengthening of RC beams with web openings. Openings are classified based on size, shape, position, orientation, and the stage at which they are introduced. Typical failure modes, such as flexural and shear failures, are also discussed. Among different shapes, circular openings perform better due to smoother stress distribution. Beams with openings in the flexural region generally show improved behavior compared to those in shear zones. Strengthening techniques using ferrocement and strain-hardening cementitious composites (SHCC) have proven effective. The study highlights the importance of considering web openings during the design phase to enhance structural performance and avoid unexpected failures. Key Words: Reinforced concrete beams, web openings, structural performance, serviceability, stress concentration, strengthening techniques.

Member Size Effect in Seebeck Coefficient of Cement Composites Incorporating Silicon Carbide

This study investigates the size effect on the Seebeck coefficient (SC) in cement composites incorporating silicon carbide (SiC). Two specimen shapes, cubic (50 × 50 × 50 mm3) and beam (40 × 40 × 160 mm3), were analyzed with varying SiC substitution ratios (0%, 50%, and 100%) for fine aggregates. Thermal and electrical conductivities were measured to assess their influence on the SC. The results showed that a higher SiC content increased porosity, which reduced mechanical strength but significantly improved thermal and electrical conductivities. Thermal conductivity increased from 1.88 W/mK (0% substitution) to 11.89 W/mK (100% substitution), while electrical conductivity showed an improvement from 0.0056 S/m to 0.065 S/m. Cubic specimens exhibited higher SC values compared to beam specimens, with a maximum SC of 1374 μV/K at 100% SiC substitution, attributed to shorter thermal diffusion distances. The findings suggest that optimizing member size and SiC content can significantly improve the thermoelectric performance of cement composites, potentially enhancing energy efficiency in construction applications.

Research Progress of Straw Fiber Reinforced Cementitious Composites

Sustainable development involves the use of sustainable materials as substitutes for traditional materials to avoid excessive consumption of natural resources. As a natural green material, plant fiber is gradually attracting the attention of researchers in the field of architecture due to its potential application value in composite materials. In order to promote the development of natural plant fiber composites, based on the analysis of the characteristics of natural plant fiber materials, and based on the role of natural plant fiber composites in crack resistance and toughening, internal maintenance, heat preservation and energy conservation, this paper comprehensively reviews the application of plant fiber cement based composites in building projects, hoping to provide some reference for the development and application of new building materials.

Impact of Pumice Substitution on Mortar Properties: A Case Study on Mechanical Performance and XRD Analysis

The incorporation of sustainable construction is essential for minimizing the environmental footprint of cementitious composites. This research examines the mechanical behavior and microstructural features of alternative mortars in which pumice acts as a partial cement replacement. By applying the Taguchi methodology, nine mortar mix variations were assessed at different pumice replacement rates (15%, 25%, and 50%), and their mechanical strength was compared against a control mixture without substitution. Additionally, an X-ray diffraction (XRD) analysis identified the mineral components in the pumice to evaluate their performance and durability. Based on a statistical variance analysis (ANOVA), mortars with up to 25% substitution are suggested as they attain mechanical strength values comparable to those of a control mixture. This study contributes to the advancement of environmentally sustainable construction materials and provides valuable insights into the viability of using pumice in sustainable infrastructure developments.

Surface-Engineered Cenospheres Encapsulating Phase Change Materials for Functional Cementitious Composites.

The escalating global energy demand underscores the critical need for advanced solutions for energy-efficient buildings. Passive thermal energy storage systems using microencapsulated phase change materials (PCMs) offer promise but face integration challenges in cementitious materials due to weakening mechanical strength, which arises from poor shell strength and weak interfacial bonding with cementitious phases. This study introduces a novel approach for synthesizing functionalized microencapsulated PCMs from fly ash-based cenospheres addressing interfacial compatibility. Cenospheres are perforated for PCM encapsulation and sealed using two different materials: 1) melamine-formaldehyde (MF), a standard polymeric shell; and 2) silica, selected for its chemical compatibility with cementitious phases. Experimental results show that the silica sealing improved mechanical strength by 50% over those of MF, corroborated by molecular dynamic simulations showing silica's binding energy with calcium silicate hydrate exceeded threefold, with more than twice the uniaxial tensile strength. Thermal analyses confirmed the preservation of PCM in both sealing approaches. This work establishes a transformative pathway for advancing PCM-based thermal energy storage in building materials.

Influences of Additives on the Rheological Properties of Cement Composites: A Review of Material Impacts

Cement-based materials are essential in modern construction, valued for their versatility and performance. Rheological properties, including yield stress, plastic viscosity, and thixotropy, play indispensable roles in optimizing the workability, stability, and overall performance of cement composites. This review explores the effects of supplementary cementitious materials (SCMs), chemical admixtures, nanomaterials, and internal curing agents on modulating rheological properties. Specifically, SCMs, including fly ash (FA), ground granulated blast furnace slag (GGBFS), and silica fume (SF), generally improve the rheology of concrete while reducing the cement content and CO2 emissions. Regarding chemical admixtures, like superplasticizers (SPs), viscosity-modifying agents (VMAs), setting-time control agents, and superabsorbent polymers (SAPs), they further optimize flow and cohesion, addressing issues such as segregation and early-age shrinkage. Nanomaterials, including nano-silica (NS) and graphene oxide (GO), can enhance viscosity and mechanical properties at the microstructural level. By integrating these materials above, it can tailor concrete for specific applications, thereby improving both performance and sustainability. This review presents a comprehensive synthesis of recent literature, utilizing both qualitative and quantitative methods to assess the impacts of various additives on the rheological properties of cement-based materials. It underscores the pivotal roles of rheological properties in optimizing the workability, stability, and overall performance of cement composites. The review further explores the influences of SCMs, chemical admixtures, nanomaterials, and internal curing agents on rheological modulation. Through the strategic integration of these materials, it is possible to enhance both the performance and sustainability of cement composites, ultimately reducing carbon emissions and advancing the development of eco-friendly construction materials.

Influence of 3D-printed, milled and pressed lithium disilicate on the bond strength to two resin cements: an in vitro study.

Influence of 3D-printed, milled and pressed lithium disilicate on the bond strength to two resin cements: an in vitro study.

Impact of Wood Bio-aggregate Content on the Thermo-physical and Mechanical Properties of Bio-based Cementitious Composites

Impact of Wood Bio-aggregate Content on the Thermo-physical and Mechanical Properties of Bio-based Cementitious Composites

Integrating life cycle assessment (LCA) and machine learning for sustainable designs: a case study on protective layers made of mineral-bonded fiber-reinforced composites

Abstract Purpose In recent years, machine learning (ML) has become an important tool for predicting material properties and optimizing their mechanical performance without the need for large data sets. However, when design considerations only target structural characteristics, sustainability issues are often overlooked, leading to increased carbon dioxide emissions, energy consumption, and over-reliance on non-renewable materials. This study seeks to bridge this gap by optimizing the design of impact-resistant fiber-reinforced cement-based composites through a sustainability-driven, ML-based modeling approach. Methods In this context, we propose a three-stage integrated framework that combines experimental test databases, sustainability assessment, and ML modeling. The specific design scenario considered here is the use of these materials as protective layers for concrete structures under impact loading. A variety of combinations of fiber and/or textile-reinforced cementitious composites were considered, including single and multiple layers. A life cycle assessment (LCA) was performed in terms of global warming potential (GWP), as this is a sensitive and critical environmental parameter in the concrete industry. The experimental data, consisting of 193 tests on composites subjected to hard impacts, measured the dissipated energy and ballistic limits. Principal component analysis (PCA) was employed to identify patterns and correlations within the experimental data. Based on the database, an ML model was developed to predict energy dissipation, enabling optimization for untested configurations. A multi-objective optimization (MOO) strategy was applied to balance the energy dissipation and GWP constraints, enabling the identification of Pareto-optimal solutions that represent the best trade-offs between mechanical performance and environmental impact. Conclusions The ML model demonstrated high accuracy in predicting GWP and energy dissipation, closely matching experimental data for tested configurations and indicating strong generalization potential for unseen cases. For severe impact applications (above 4 kJ of impact energy), carbon textile grids outperformed other reinforcements, achieving a 20% performance increase with two layers of textile, while maintaining emissions at 5–6 kg CO $$_2$$ 2 equivalent per plate. Glass emerged as the best alternative for strict GWP limits. Remarkably, hybrid composites, despite their higher cement content in comparison to conventional textile-reinforced concrete (TRC), are the most viable choice due to the superior toughness attained due to short fibers and the sustainability benefits of limestone calcined clay cement (LC3) blended binders. Ultimately, the ML model and LCA framework developed in this study can be extended to other material systems and design scenarios.

Methodological aspects of strength testing of building products based on thermoplastic waste

The urgency of the problem of recycling polymer waste is increasing every year. It is promising to use thermoplastic waste as binders in polymer-mineral compositions for the production of small-piece construction products such as paving slabs, curbs, parking limiters, elements of landscape design, etc. Technical requirements for the compositions of polymer-mineral compositions, the properties of their products, test methods are not regulated. One of the most informative characteristics is static uniaxial compression tests. It is necessary to accumulate statistics on strength tests of composites based on secondary thermoplastics and develop mathematical patterns of the influence of sample size, primarily their thickness, on strength properties. Therefore, the work is aimed at improving the methodological aspects of assessing the compressive strength of polymer-mineral samples based on thermoplastic matrices. Crushed polymer waste of polyethylene terephthalate and polypropylene, a combination additive ethylene vinyl acetate, and limestone flour were used to make the samples. Samples of various thicknesses were made by pressing from hot mixtures, then their compressive strength was determined. As a result, a differentiated approach to the geometry of the samples is proposed, taking into account the peculiarities of their manufacture and the complexity of obtaining samples of exactly the same thickness. A linear basic dependence of strength on the thickness of the sample is obtained, and a method for calculating compressive strength from the experimental thickness of the sample to the control one is proposed. It is proposed to take the sample thickness of 4 cm as a control, by analogy with the current standards for cement composites. Using the basic dependence and the proposed conversion method, it is possible to design formulations of compositions using various powdered mineral fillers (filling degree of more than 50% by weight) and various thermoplastic wastes, combining rigid thermoplastic polyethylene terephthalate and polyolefins in compositions.

Synergistic effects of PVA fibres and healing agent encapsulated gelatine carrier in cementitious composites

Synergistic effects of PVA fibres and healing agent encapsulated gelatine carrier in cementitious composites

Numerical Modelling of Nanoindentation in Cement Paste

The instrumented nanoindentation technique is widely used to investigate the local mechanical properties of cementitious composites. Due to its high-resolution load control and displacement sensing capabilities, this technique is increasingly being used to measure hardness, elastic modulus, creep parameters, and residual stresses that have been explored at micro and nanolevel. During the indentation of brittle materials, cracks may be generated around the impression, which depend on load conditions, material and indenter geometry. This work presents a simulation of the three-dimensional nanoindentation model established with finite element method and modified constitutive relation. The model is created to simulate on single phase (homogeneous) materials such as cement clinker (C3S and C2S separately) and the hydrated phase – Low Density CSH and High Density CSH separately that constitute the primary phases of cementitious matrix. Then numerical modelling (FEA) of indentation is conducted using the concrete damage plasticity (CDP) material model, with the constants calibrated for hardened cement paste. At the end, there was a good agreement when comparing the differences between the simulated and literature experimental results.

The use of dendritic fibrous nano-titanium to enhance the initial characteristics and durability of lightweight concrete

The utilization of nanoparticles in concrete has been propelled by their advantageous attributes, such as their fine particle size and remarkable reactivity. To enhance these properties, various nanoparticles can be integrated into the lightweight concrete matrix. We introduce a novel technique to produce TiO2 structures resembling dandelions, featuring interfaces between anatase and TiO2 phases as well as a distinct outer layer. This approach utilizes a deep eutectic solvent-tuning method that is both user- and environmentally friendly. The formation of this remarkable external covering is attributed to the hierarchical arrangement of two-dimensional ultrathin nanosheets with mesopores in a three-dimensional configuration. The primary focus of this study is the utilization of DFNT, a nanoparticle possessing a three-dimensional structure, within the matrix of lightweight concrete. To conduct this study, concrete cases with congestion of 1000 kg/m3 were fabricated and subjected to testing. We sought to evaluate the effect of different weight ratio proportions of DFNT on the enduring characteristics of lightweight concrete, such as the contraction caused by drying, the degree of openness, the capacity to absorb water, and the speed at which ultrasonic waves travel. The inclusion of DFNT induces a transformation in the microstructural composition of lightweight concrete, shifting it from a loose needle-like structure to a more compact and cohesive microstructure characteristic of cementitious composites. Furthermore, DFNT enhances the lightweight concrete matrix by occupying the empty spaces, tiny fractures, and gaps present within it.

Effect of chemical treatments on the mechanical and physical performance of corn straw fibers in cement mortar

This study investigates the effects of water, acetic acid (CH3COOH), and sodium hydroxide (NaOH) treatments on the physical and mechanical properties of corn straw fibers in cement mortar. The use of natural fibers in cement composites offers a promising approach to reducing reliance on synthetic materials and utilizing agricultural byproducts. Chemical treatments like NaOH and CH3COOH improve fiber-matrix bonding, which is critical for enhancing the mechanical properties of the composites. NaOH treatment resulted in the most significant improvements, with surface roughness increasing by 104.8% and compressive strength reaching 52.8 MPa at 1.5% fiber content after 28 days. CH3COOH treatment boosted early-stage flexural strength, achieving 6.75 MPa at 7 days, but its long-term effect was limited. Water treatment showed minimal impact on fiber performance. These results indicate the potential for NaOH-treated fibers to enhance the strength and durability of cement-based materials.

Enhancing Cement-Based Composites Properties by NaOH-Treated Luffa Fibers

The combination of cement and natural fibers, as well as Luffa fibers, represents a revolutionary breakthrough in sustainable building materials. By combining these elements, this innovation has metamorphosed the mechanical properties of the fibers, significantly improving their ability to bond with cement. This synergy offers a major breakthrough in the creation of composites that are both robust and environmentally friendly, opening the way to a multitude of potential applications in the industrial and construction sectors. The Luffa fibers were subjected to extensive tensile tests to evaluate their strength and elasticity after a sodium hydroxide (NaOH) treatment procedure, while the composite material was subjected to three-point bending tests to analyze its mechanical properties under varying loads. At the same time, the density of the composite was accurately determined, and in-depth studies were carried out to assess its water absorption rate, which is critical for construction applications. In addition, detailed mathematical modeling was performed using advanced methods such as Hirsch, ROM and IROM. Alkali treatment substantially increased the tensile strength and Young’s modulus of Luffa fibers respectively from 23.80± 2.1 MPa to 67.01± 2.8 MPa with an increasement by 142%, and 3.65±0.4 GPa to 11.39± 0.9 GPa with an increasement by 152%. Cement composites showed a peak flexural strength of 1.42 MPa at 1.04%. The significant improvement in the mechanical properties of Luffa fibers achieved through alkali treatment, coupled with their inherent biodegradability, positions them as a promising sustainable reinforcement material for the construction industry.

Workability and Compressive Strength of Mortar with Addition of Rice Husk Ash (RHA) as Partial Cement Replacement in Engineered Cementitious Composite (ECC)

In today’s engineering world, an industrial ecology is a prevalent approach for achieving long-term industrial development. This approach encourages waste from by-products to be recycled. One of these by-product wastes is rice husk ask (RHA). Previous research has highlighted RHA’s significant potential as a cement additive alternative. The possible use of RHA as a partial replacement for cement in designed cementitious composites is briefly describe in the work (Engineered Cementitious Composite). RHA was utilized to substitute cement at various percentages by volume in the experiment, including 5%, 10%, 15% and 20%. The flow table test was used to evaluate the workability of the fresh mortar mix, while the compressive strength test was used to study the mechanical properties of the hardened mortar. From the result obtained, the workability of RHA-ECC is maximum at 10% by volume compared to other replacement levels with 52.21% at 28 days of curing. This study adds to the body of knowledge about the sustainability of RHA as a partial cement replacement for ECC.

Plasma Immersion Ion Implantation Increases Adhesive Bond Strength of PEK and PEEK to Dental Composites and Enables Hydrolysis Resistance

AbstractThe additive manufacturing technology known as selective‐laser‐sintering is available for the poly‐aryl‐ether‐ketone (PAEK) family of high‐strength polymers, enabling the rapid production of personalized dental and mandibular reconstructions at or near the point‐of‐care. PAEK mandibular segmental replacements, bridges, and abutments are transitioning to clinical use. There remains a need for improved adhesion between PAEK polymers and dental adhesives including dental composite resin cements. Without surface modification, there is a weak bond to PAEK polymers, especially when the surface of the polymer is smooth. Plasma‐immersion‐ion‐implantation (PIII) is applied to demonstrate a significant increase in the bond strength between Polyether–ether–ketone (PEEK) and Poly–ether–ketone (PEK) polymers and a commonly used dental composite resin cement, for multiple levels of interface roughness. A validated predictive model for the bond strength as a function of surface roughness expressed as a surface area ratio is presented that demonstrates the relative effect of PIII and mechanical interlocking. The results show that the bond strength achieved using PIII is retained even when the primer step is omitted, an important advance as the primer has been associated with hydrolysis‐induced weakening. A long‐term water immersion test shows that the PIII‐assisted primer‐free bond retains its strength while all primer‐assisted bonds are weakened.

The Impact of Superplasticizer Chemical Structure on Reactive Powder Concrete Properties

It is difficult to obtain efficient flowability of reactive powder concrete (RPC) mix due to a low water/binder ratio. The improvement of material flowability could be achieved by using the latest generation polycarboxylate superplasticizers (SPs), as well as by changing the mixing procedure. This paper presents two different superplasticizers’ effect on a fresh mix and hardened reactive powder concrete properties. Results of systematic experimental studies (including physicochemical and spectroscopic tests) and molecular modelling suggest that superplasticizer chemical structure plays a key role in shaping the properties of the concrete mix. It has been demonstrated that SP containing more carboxylate salt groups -COO− Me+ improves fluidity of the RPC mix and causes its better deaeration. In contrast, hardened concrete exhibits lower porosity and consequently greater strength. On the other hand, a change in ingredients mixing from a three-stage to a four-stage procedure increased the mix flowability and the RPC strength. The chemical structure of SP and the mixing procedure had no significant impact on cement hydration progress. Our results could be useful both from the point of view of the basic science of materials and the applied field of planning of cement composites in construction.