Properties Of Cementitious Composites Research Articles

CaCO3 coating of off-specification fly ash for upcycling in cementitious materials

To address this challenge of shortage of specification-grade fly ash(SGFA) and recycling of off-specification fly ash(OSFA), this research proposes a novel approach of coating OSFA with nano-CaCO3. This improves the surface characteristics of the particles and creates nucleation sites that enhance cement hydration, thus potentially improving the fundamental properties of cementitious materials incorporating OSFA. The first step in this process involves optimizing the quantity of nano-CaCO3 coating on OSFA to achieve the best mechanical properties for concrete applications. Subsequently, experimental investigations were conducted to compare the mechanical properties of cementitious pastes prepared with original OSFA, OSFA and nano-CaCO3 powders, and coated OSFA. Isothermal calorimetry and pore structure analyses indicated that the coating treatment transformed OSFA from a detrimental additive to a beneficial one for concrete. This coating significantly strengthened the OSFA particles and promoted cement hydration, consequently enhancing the mechanical properties of cementitious composites containing OSFA. This innovative method offers a promising solution for addressing the fly ash shortage in the concrete industry while minimizing the need for land disposal of OSFA.

Comparative Study on the Impact of Various Non-Metallic Fibres on High-Performance Concrete Properties

The performance of high-performance concrete has been enhanced in the present study by incorporating non-metallic fibres without altering the binder content. The impact of these fibres on high-performance concrete flexural and compression characteristics and the arrangement of fibres within the composite were systematically analysed. Unlike conventional practices, the authors of the research introduce various non-metallic fibres, including alkali-resistant glass fibres, carbon microfibers, three types of polypropylene microfibers, and one type of polyvinyl alcohol fibre while maintaining an equal amount of binder. The research aims to comprehensively evaluate the fibre’s influence on cement composite properties. Various types of non-metallic fibres, highlighting differences in diameters and their physical-mechanical properties with a constant amount by volume, have been considered in the research. Alkali-resistant glass and carbon fibres exhibit low values of residual post-cracking force but polyvinyl alcohol fibres demonstrate the best post-cracking behaviour, with a residual post-cracking force value. This detailed examination of fibre distribution and composition sheds light on the nuanced effects on fresh and hardened concrete properties. Notably, this work diverges from existing research by maintaining a constant binder amount and considering the quantitative distribution of fibres in a unit volume of the cement matrix, along with their aspect ratio. These findings provide valuable insights for selecting the most suitable non-metallic fibres for enhancing high-performance concrete properties.

Destructive Effects of Slag from Municipal Waste Incineration Plants on Cement Composites.

The increasing production of solid waste and the scarcity of natural aggregates as a matter of fact have made waste recycling a necessity. One such waste, which is generated in large quantities, is slag. However, slag from incineration plants may contain harmful elements that adversely affect the physical, chemical and mechanical properties of cement composites. This study presents laboratory research results on the effect of slag from the Poznan Municipal Waste Thermal Conversion Plant (Poland) on the physicochemical properties of cement composites. The samples were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown that the slag analyzed contained significant amounts of aluminum, which had a direct effect on the structure of the concrete. An example of this influence is the release of hydrogen during reactions, which causes swelling and cracking of the concrete and reduces its mechanical strength. The authors emphasize that waste aggregate (slag) can be effectively used in the production of concrete after appropriate processing that reduces the risk of adverse effects.

Influence of elevated temperature on the interfacial adhesion properties of cement composites reinforced with recycled coconut fiber

Magnesium phosphate cement (MPC) is the preferred material for rapid repair due to its rapid setting and early strength properties. However, its inherent brittleness renders it less suitable for use in assembled building nodes. To address the brittleness of MPC, coconut fiber (CF), a natural fiber known for its toughness, is often employed as a reinforcement. However, CF-MPC encounter difficulties in high-temperature settings, such as fire emergencies, which may compromise the interfacial bonding properties of this materials. This paper presents an investigation into the interfacial bonding properties of CF-MPC at elevated temperatures. The study employed microscopic analysis to observe the material changes of CF at elevated temperatures, evaluated the mechanical property changes by means of Fiber Tensile Test, and assessed the interfacial bonding performance by means of Fiber Drawing Test between CF and MPC. The findings indicated that as the temperature increased, the carbonized residue of the CF gradually decomposed, resulting in a notable decline in mechanical strength. Upon exceeding 400 °C, the carbonization of CF was complete, resulting in the loss of its mechanical properties. Besides the results also demonstrated that the interfacial bond strength of CF-MPC at a burial depth of 7.5 mm reaches its maximum value of 2.14 MPa at 20 °C. As the temperature rises to 200 °C, the interfacial bond strength at a burial depth of 12.5 mm reaches its maximum value of 1.08 MPa at this temperature. The findings of this study are conducive to promoting the application of CF-MPC at high temperatures and provide a theoretical basis for the subsequent optimization of this material.

Organic and Inorganic Modifications to Increase the Efficiency in Immobilization of Heavy Metal (Zn) in Cementitious Composites-The Impact of Cement Matrix Pore Network Characteristics.

This research investigated the properties of modified cementitious composites including water purification from heavy metal-zinc. A new method for characterizing the immobilization properties of tested modifiers was established. Several additions had their properties investigated: biochar (BC), active carbon (AC), nanoparticulate silica (NS), copper slag (CS), iron slag (EAFIS), crushed hazelnut shells (CHS), and lightweight sintered fly ash aggregate (LSFAA). The impact of modifiers on the mechanical and rheological properties of cementitious composites was also studied. It was found that considered additions had a significantly different influence over the investigated properties. The addition of crushed hazelnut shells, although determined as an effective immobilization modifier, significantly deteriorated the mechanical performance of the composite as well as its rheological properties. Modification by iron slag allowed for a significant increase in immobilization properties (five-fold compared to the reference series) without a substantial impact on other properties. The negative effect on immobilization efficiency was observed for nanoparticulate silica modification due to its sealing effect on the pore network of the cement matrix. The capillary pore content in the cement matrix was identified as a parameter significantly influencing the immobilization potential of most considered modifications, except biochar and active carbon.

Substantiation of the Effectiveness of Water-Soluble Hydrophobic Agents on the Properties of Cement Composites

Substantiation of the Effectiveness of Water-Soluble Hydrophobic Agents on the Properties of Cement Composites

Simulation-based analysis of impact of CNT dispersion on hydration of cement paste

Dispersion of carbon nanotubes (CNTs) is one of the key factors determining the mechanical properties of cement composites. This study analyzed impact of CNT dispersion on hydration of cement paste. An image analysis method based on optical microscopy images was proposed to quantitatively consider the CNT dispersion. To quantify CNT dispersion, this paper proposed PCNT, which is the percentage of a 1 μm2 space containing CNTs within entire water volume. To investigate CNT dispersion effect, the same amount of CNT was classified into six steps (S1, S5, S15, S30, S50, and S100) according to PCNT. The relationship between CNT dispersion and the hydration, porosity, and compressive strength of the cement paste was analyzed using a CEMHYD3D considered CNT effect. The optimal CNT dispersion for 0.1 wt% CNT reinforcement in a cement paste with water-to-cement ratio of 0.3 was found to be 15 % PCNT. The improvement in CNT dispersion resulted in acceleration of hydration of cement paste, improvement in compressive strength, and densified microstructure.

Unraveling the reinforcing mechanisms for cementitious composites with 3D printed multidirectional auxetic lattices using X-ray computed tomography

This study investigates the mechanical properties of cementitious composites with 3D-printed auxetic lattices, featuring negative Poisson’s ratios (auxetic behavior) in multiple directions. These lattices were fabricated using vat photopolymerization 3D printing, and three base materials with varying stiffness and deformation capacities were analyzed to determine their impact on the composites’ mechanical behavior. To unravel the reinforcing mechanisms of multidirectional auxetic lattices, which exhibit auxetic behavior in both planar and out-of-plane directions, X-ray computed tomography (X-ray CT) was utilized to analyze composite damage evolutions under different strain levels. The micro-CT characterization reveals that auxetic lattices more effectively constrain crack growth and dissipate energy by distributing stress evenly within the cement matrix. In contrast, due to lack of lateral confinement, the non-auxetic lattice reinforced composites primarily dissipate energy through extensive crack propagation and interfacial damage, leading to lower peak strength. When strain exceeding 5%, although the confinement from the auxetic behavior diminished with crack propagation, the lattice can still maintain the composite’s structural integrity, resulting in 1.7 times higher densification energy than conventional cement-based materials. These findings provide valuable insights for designing auxetic lattice-reinforced cementitious composites with enhanced load-bearing capacity and improved dissipation capabilities.

A mechanism study of thermal resistance formation and post-fire strength recovery in cement paste with carbon nanotubes and nanosilica via focused ion beam/scanning electron microscopy tomography

Although carbon nanotubes (CNT) and nanosilica (NS) have shown substantial potential for enhancing the thermal resistance and post-fire mechanical recovery of cementitious composites, their combined synergistic effects remain unclear. This study aimed to elucidate the influence of CNT and NS double-hybrids on the physicochemical properties of cementitious composites under different heating temperatures (200, 500, and 800 °C) and re-curing conditions (25 °C/65 % RH and water immersion). We assessed the changes in the compressive and tensile strengths, bulk density, surface morphology, hydration products, and pore characteristics using focused ion beam scanning electron microscopy to visualize the evolving nanoscale pore structures. Our findings reveal a remarkable synergistic effect on the thermal resistance and strength recovery properties of the CNT/NS hybrid samples, owing to the stable matrix observed after heating to 800 °C. Following exposure to 800 °C, the tensile strength exhibited a remarkable 69.6 % increase compared to its pre-heating state, without any indication of crack formation. The CNT served as nucleation sites, expediting the pozzolanic reaction of NS during heating and resulting in a homogenized pore structure with interconnected hydrates. The CNT/NS hybrid samples exhibited uniform shrinkage of hydrates without creating nanoscale rod-like pores typical in ordinary cement paste, while the increase in pore volume was predominantly attributed to the expansion of existing pores and the formation of nearby new pores.

Advanced cement composites: Investigating the role of graphene quantum dots in improving thermal and mechanical performance

The investigation of graphene quantum dots (GQDs) at very small nano- and atomic sizes is a novel approach in the fields of structural cement, concrete, and ceramic materials, which have not been thoroughly explored. This study investigates the comparative effects of two variations of GQDs, Qdl and Qdp, against a control mixture to assess the potential of graphene derivatives in enhancing thermal and mechanical properties of cement composites. The research presents their influences across a wide range of attributes, including flowability, bulk density, permeable voids, water absorption, compressive strength, flexural strength, surface temperature, thermal conductivity, thermal diffusivity, specific heat capacity, Brunauer-Emmett-Teller (BET) isotherm, thermogravimetric analysis (TGA), and microstructural characteristics. The empirical data underscore the superior freshness, physical, mechanical, and thermal attributes of GQDs-infused cement composites. Notably, the composites with 0.3 % Qdl show 20.8 % and 50 % increases in compressive and flexural strengths, respectively. On the other hand, the composites with 1.2 % Qdp show significant improvements in both compressive and flexural strengths, being 40 % and 108 % stronger than the control, respectively. Additionally, the thermal properties of the composites exhibit a proportional enhancement with increasing GQDs content. Microstructural analyses reveal a nano-bridging mechanism well-uniformly facilitated by the secondary nucleation and crystallization of calcium silicate hydrate (CSH) gel. This investigation offers innovative insights into the incorporation of GQDs in cement composites, highlighting their potential to create highly conductive structural cement and ceramic.

Effect of MWCNTs-OH on the mechanical properties of cement composites: From macro to micro perspective

This study is focused on elucidating the role and mechanism of hydroxyl-functionalized multi-walled carbon nanotubes (MWCNTs-OH) as a reinforcement material in cement-based composites. The dispersion of MWCNTs-OH within the cement composites was first assessed using Raman spectroscopy. Subsequently, SEM, FT-IR, TGA, XRD, and nano-indentation techniques were employed to investigate the structural transformation and phase changes occurring in the cement matrix upon incorporating MWCNTs-OH. The results reveal that MWCNTs-OH can significantly improve the macro-mechanical properties of cement composites by their capacity for pulling out, pore-filling, inducing multi-cracking, and promoting hydration. From a micro-perspective, observations of the micro-morphology demonstrate that MWCNTs-OH reinforces cement composites through crack-bridging and pull-out effects. Regarding the hydrated calcium silicate (C-S-H), the addition of MWCNTs-OH has a negligible impact on the ratio of low-density C-S-H (LD-CSH) to high-density C-S-H (HD-CSH). Moreover, the results obtained from FT-IR and XRD tests provide evidence that the bonding between MWCNTs-OH and the cement matrix is predominantly governed by physical interactions.

Effect of nanocomposite cementitious capillary crystalline waterproofing material on self-healing properties of cementitious composites

There are limited studies about the effect of nanocomposite cementitious capillary crystalline waterproofing material (CCCW) on the self-healing properties of cementitious materials in different environments. Compressive strength recovery ratio(CSRR) test, electrochemical impedance spectroscopy (EIS) test, and macroscopic cracks healing observation test were adopted to study the self-healing properties of pure mortar specimens, mortar specimens mixed with CCCW, and nanocomposite CCCW respectively under three kinds of curing conditions. The self-healing mechanism of nanocomposite CCCW was analyzed using thermogravimetric analysis and differential scanning calorimetry (TG-DSC), mercury intrusion porosimetry (MIP), and scanning electronic microscope and energy dispersive spectroscopy (SEM-EDS) techniques. It was found that the curing condition significantly influenced self-healing performance, with touching water curing condition having the highest impact, followed by soaking water curing condition and natural curing condition. Nanocomposite CCCW promoted the healing performance of damaged specimens and significantly increased the CSRR. Under touching water curing condition, the CSRRs of the mortar groups with 3% nano-SiO2, 3% nano-CaCO3, and 2% nano-MgO were 26.1%, 11.5%, and 8.6%, respectively, higher than the CSRR of the single-doped CCCW group. After 28 days of touching water curing, change in charge transfer resistance before and after specimen healing (∆Rct) of the groups with 3% dosage of nano-SiO2, 3% dosage of nano-CaCO3, and 2% dosage of nano-MgO were 5.2, 1.8, and 2.7 times, respectively, higher than that of the single-doped CCCW mortar group. Throughout the healing process, the addition of the three nanocomposite CCCWs accelerated the hydration reaction to generate C-S-H gel, CaCO3, Aft, etc., improved the internal pore structure, reduced the size of the most probable pore diameter (MPPD) of the mortar specimens, and ultimately promoted the self-healing properties of the cementitious materials.

Enhancing the Properties of Cement Composites Using Granulated Hemp Shive Aggregates

In recent years, civil engineers have been exploring innovative methods of constructing buildings using environmentally friendly materials. The beneficial properties of hemp harl, an agricultural waste that is gaining popularity in construction, prompted the idea of strengthening its properties through the granulation process and using it as an aggregate in cement composites. This work aimed to investigate whether the use of hemp husk in the form of granules would have a positive effect on the properties of cement composites compared to their traditional form (stems). Potato starch was introduced as an additional factor in the granulation process to improve the material. Experimental tests were carried out on organic fillers, fresh mixtures, and hardened composites. Physical, mechanical, and structural tests (SEM imaging) were carried out. The highest strength was demonstrated by samples containing hemp shive aggregate (1.186 MPa), while the use of hemp shives in the form of granules had a positive effect on the consistency and density, and it also reduced water absorption by 30% during the production of the composite. The apparent density of composites with hemp shives in the form of hemp pellets was higher (1042 ÷ 1506 kg/m3) than in the case of composites with shives in the form of harl (727 ÷ 1160 kg/m3). Nevertheless, hemp shive in both forms can be used as a natural aggregate in cement composites.

Fracture properties of cementitious composites containing nano-materials: A comprehensive review

Traditional cementitious materials exhibit low strength and poor durability, which cannot keep up with the requirements of modern concrete infrastructure. The small particle size and large specific surface area (SSA) of nano-materials can contribute to the volcanic ash activity, nucleation effect, and filling effect in cementitious composites (CC), which can effectively promote cement hydration and improve the internal structure of the matrix, thereby enhancing the fracture performance of CC. In order to gain a deeper understanding of the enhancing effect of nanomaterials on the fracture performance of CC, this article reviews the effects of different nanomaterials by introducing three fracture models. The results show that the effect of the type of nanomaterials on improving fracture performance was different due to the different structures of nanomaterials, and the optimal content of each type of nanomaterial was not the same. Though there are great application prospects for nanomaterials in CC, there are still many opportunities and challenges for nanoparticle-reinforced cementitious composites (NRCC) in actual engineering applications.

Enhancing mechanical properties of cementitious composites by boron nitride nanosheets modified carbon fiber

Carbon fiber (CF) is commonly employed to enhance the mechanical properties, electrical conductivity, and electromagnetic absorption properties of cementitious composites. However, its weak interfacial bonding with the matrix limits its application in such composites. In this study, boron nitride (BN) nanosheets were synthesized via the solid-state reaction and used to modify CF surface. The flexural and compressive strengths of cementitious composites incorporating BN nanosheets coated CF (BN@CF) increased by 18.45 % and 29.38 %, respectively, with CF doping at only 0.2 wt%. Isothermal calorimetry and TGA results revealed that BN nanosheets on CF surface would provide nucleation sites for the formation of C–S–H and CH. The microstructure and bonding properties of BN@CF were characterized using SEM/EDS, FTIR, XPS, finite element analysis, and single fiber pullout test. The results showed that the significant improvement of interfacial properties between the fiber and the matrix contributed to the increase of mechanical properties of cementitious composites. These findings provide an effective strategy for the strength development of CF-reinforced cementitious composites.

Improving electrical and mechanical properties of cement composites by combined addition of carbon black and carbon nanotubes and steel fibers

A cost-effective cement composite material has been developed for grounding systems, utilizing carbon black, carbon nanotubes, and steel fibers as conductive dopants. The electrical conductivity, mechanical properties, and fluidity of cement composites are investigated, and the synergetic mechanism of multiple conductive dopants in cement composites is revealed based on microscopic means. The results show that the combination of carbon black, carbon nanotubes, and steel fibers facilitates the establishment of efficient conductive networks in cement composites. The addition of 5 % carbon black, 0.3 % carbon nanotubes (by weight of cement), and 0.6 % steel fibers (by volume of composite) reduced the resistivity of the cement composite from 5568 Ω·cm to 310 Ω·cm after 28 days of curing. Then, it decreased to 267 Ω·cm after natural drying in laboratory environment until the 90th day. In addition, the resistivity of cement composites varies less than 5 % in environments ranging from −20°C to 50°C. Furthermore, the compressive and flexural strengths were 30.06 MPa and 6.17 MPa, and the flow diameter was 167 mm, which provided good mechanical strength and workability for conventional engineering applications. This paves an effective way for the further application of cement composites in grounding systems.

Multifaceted Analysis of the Thermal Properties of Shielding Cement-Based Composites with Magnetite Aggregate.

The paper presents and discusses the results of a study of the thermal properties of cement composites with different contents of magnetite aggregate (0%, 20%, 40% and 60% by volume). The effect of grain size on the evaluated thermal properties was also investigated. For this purpose, concrete containing 50% by volume of magnetite aggregate with four different fractions (1-2 mm, 2-4 mm, 4-8 mm and 8-16 mm) was used. Thermal parameters were evaluated on specimens fully saturated with water and dried to a constant mass at 65 °C. The series with varying grain sizes of magnetite achieved thermal conductivity values in the range of 2.76-3.03 W/(m·K) and 2.00-2.21 W/(m·K) at full water saturation and after drying to a constant mass, respectively. In the case of the series with 20% magnetite by volume, the thermal conductivity was 2.65 W/(m·K) and 1.99 W/(m·K) for the material fully saturated with water and dried to a constant mass, respectively. The series with a 60% volume share of magnetite obtained values of this parameter of 3.47 W/(m·K) and 2.66 W/(m·K), respectively, under the same assumptions.

Effects of cellulose nanofibrils on rheological and mechanical properties of 3D printable cement composites

This study explores the effects of cellulose nanofibrils (CNF), a relatively new type of nanocellulose material, on the rheological and printability characteristics of cementitious mixtures, and the mechanical properties of 3D printed specimens. The rheology of the mortar mixtures with varying ratios of CNF is thoroughly assessed first. Two testing protocols, stress growth test and ramp test, are followed for rotational measurements using a shear rheometer with a building cell and vane motor. Stress growth tests are carried out to quantify the static yield stress of the cementitious mixtures. Ramp tests are conducted to determine dynamic yield stress and plastic viscosity of the mixes using the Bingham visco-plastic material model. As oscillatory measurements, amplitude sweep tests are carried out to determine the viscoelastic properties of the mortar mixes, including storage modulus and critical strain that are found to be essential for buildability. Thermogravimetric analysis (TGA) is conducted to assess the effects of CNF on the hydration characteristics of the mixtures. The printability and the buildability of the mortar mixtures incorporating CNF are assessed using a 3D concrete printer equipped with a 10 mm diameter nozzle and screw pump mechanism. Tensile, flexural, and compressive strength tests are conducted to determine the mechanical properties of 3D printed specimens with varying ratios of CNFs. Scanning electron microscopy (SEM) is used to conduct the microstructural analysis on fractured surfaces of the mechanically tested specimens. Results indicate that adding CNF at least 0.3 wt% of cement has a favorable effect on the rheological properties of cement composites.

Ultrasonic pulse velocity as a non-destructive measure for the projectile impact resistance of cementitious composites across a wide range of mix compositions

This paper presents an investigation on the applicability of using ultrasonic pulse velocity (UPV) as a non-destructive measure for characterizing high velocity projectile impact (HVPI) resistance as well as physical/mechanical properties of cementitious composites across a wide range of mix compositions. Ultra-high performance concretes (UHPCs), engineered cementitious composites (ECCs), concretes, mortars and cement pastes with compressive strengths ranging from 34.2 MPa to 220.2 MPa and elastic moduli ranging from 17.1 GPa to 104.2 GPa are considered for investigation. Projectile impact resistance of cementitious composites is evaluated in terms of the depth of penetration (DOP) and equivalent crater diameter (ECD). Physical/mechanical properties, including compressive strength, static and dynamic moduli of elasticity, density, hardness, splitting tensile strength, compressive and flexural toughnesses, are investigated. The UPV is found to be a promising non-invasive and non-destructive measure for the DOP characterization, since both the UPV and DOP are governed by the weighted properties of underlying constituent materials (e.g. matrix and fine/coarse aggregate). In comparison to the DOP, the correlation between the ECD and UPV is relatively weak. The results indicate that there exists a strong correlation between the UPV and the elastic modulus/density/hardness of cementitious composites. It is also found that commonly used two-phase composite models can predict the UPV of concrete with good accuracy.

Effect of adsorption interactions of Arabic gum with cement

This study seeks to investigate the influence of cement and Arabic gum on the physico-mechanical and microstructural properties of cementitious composites. The influence of varying quantities of Arabic gum on the hydration, fluidity, mechanical performance and microstructure of cement paste was investigated. The influence of Arabic gum on slant shear performance and capillary water absorption was also investigated. The results indicate that the workability of cement was diminished as a result of the ability of Arabic gum to make the cement paste cohesive. It is evident that when the gum Arabic concentration increases from 147 to 174 mm, the resultant slump value for various w/b ratios drops. The adsorption characteristics showed that for a 15 mg g−1 dosage at 60, 45, 30, and 15 min, respectively, 1.43, 1.32, 1.25, and 1.03 mg g−1 are achieved. For 1% gum Arabic substitution, the highest flexural strength percentage growth is achieved at 38.46%, 23.74%, and 17.29% at 7, 14, and 28 days, respectively. In addition, the inclusion of Arabic gum improved the slant shear strength of cement composite, making it ideal for use as a building repair material with significant application potential. Experiments on the bonding behavior of the produced cementitious composite with the old mortar reveal that the shear bond strength was greatly increased, demonstrating the compatibility between the old and new cement composites. The microstructure and the porosity of the cement matrix also showed denser and compact matrix making them durable to attain better service life.