Fiber Reinforced Cement Composites Research Articles

Cracking can make concrete stronger – The coupled effect of matrix cracking and SiO2-enhanced fiber/matrix interface healing on the tensile strength of FRCC

It is a doctrine that cracking always degrades tensile properties of cementitious composites. This study first-timely demonstrates that in the presence of water, cracking can enhance the tensile properties of fiber-reinforced cementitious composites (FRCCs) via the autogenous healing of fiber/matrix interface. PVA micro-fibers with or without a layer of nano-SiO2 coating were involved. Pre-debonding, water conditioning, and reloading were applied to single-fiber specimen made with both fibers. While both fibers engaged stronger the fiber-to-matrix frictional bond after water conditioning, the enhancement of SiO2-coated fiber was significantly larger as more healing product formed in-situ. Tensile pre-cracking, healing, and reloading were applied to FRCC specimens made with both fibers. While both fibers enabled FRCC tensile recovery via self-healing, only the FRCC with SiO2-coated fibers accomplished a higher tensile strength than their uncracked-but-identically-conditioned counterpart. Micromechanics-based modeling verifies that the enhanced FRCC tensile strength was due to healing-strengthened fiber/matrix interface.

Flexural Behavior Characteristics of Steel Tubes Filled with SFRCCs Incorporating Recycled Materials.

This study deals with the effect of fly ash and recycled sand on the flexural behavior of SFRCCs (steel fiber-reinforced cementitious composites)-filled steel tubes. As a result of the compressive test, the elastic modulus was reduced by the addition of micro steel fiber, and the fly ash and recycled sand replacement decreased the elastic modulus and increased the Poisson's ratio. As a result of the bending and direct tensile tests, strength enhancement by the incorporation of micro steel fibers was observed, and a smooth descending curve was confirmed after initial cracking. As a result of the flexural test on the FRCC-filled steel tube, the peak load of all specimens was similar, and the applicability of the equation presented by AISC was high. The deformation capacity of the steel tube filled with SFRCCs was slightly improved. As the elastic modulus of the FRCC material lowered and the Poisson's ratio increased, the denting depth of the test specimen deepened. This is believed to be due to the large deformation of the cementitious composite material under local pressure due to the low elastic modulus. From the results of the deformation capacities of the FRCC-filled steel tubes, it was confirmed that the contribution of indentation to the energy dissipation capacity of steel tubes filled with SFRCCs was high. From the comparison of the strain values of the steel tubes, in the steel tube filled with SFRCC incorporating recycled materials, the damage was properly distributed between the loading point and both ends through crack dispersion, and consequently, rapid curvature changes did not occur at both ends.

Carbon fiber surface nano-modification and enhanced mechanical properties of fiber reinforced cementitious composites

It has been widely recognized that fiber–matrix interface has great significance on the performance of fiber-reinforced cementitious composites. In this research, an effective fiber modification method is proposed and its enhanced mechanical properties are observed. Through the condensation and polymerization of the tetraethyl orthosilicate under alkaline conditions, a thin SiO2 layer was formed on carbon fiber surface, which can react with Ca(OH)2 thus form calcium silicate hydrate to condense the fiber–matrix interface. In this paper, nano-SiO2 modified carbon fibers are produced and the mechanical properties of modified carbon fiber reinforced cementitious composites are investigated. Modified material exhibited 24.7% enhancement in flexural strength and up to 25.1% enhancement in tensile strength with the fiber volume fraction of 0.5%. Better post-crack behavior and toughness properties were also estimated, which were attributed to nano-modification strengthening the ITZ through the reaction of surface nano-SiO2 with Ca(OH)2 resulting in much more amount of CSH gel and a denser microstructure of fiber–matrix interface. The microstructure of denser interface and porosity can be found through SEM and BSEM analysis. The porosity on the observation surface of interface transition zone of unmodified fiber and modified fiber was 4.03% and 2.43%, respectively. The change of chemical elements in the interface transition zone was analyzed by line scanning, and the Ca/Si of the modified carbon fiber was significantly lower than that of the unmodified carbon fiber.

Improvement of tensile properties of carbon fibre-reinforced cementitious matrix composites with coated textile and enhanced mortars

Fibre Reinforced Cementitious Matrix (FRCM) systems are composite materials used for retrofitting structures thanks to their high strength-to-weight ratio and their compatibility with different substrates. The mechanical properties of FRCM depend on textile and mortar characteristics and on the interfacial bond behaviour between grid and matrix. In this research, FRCM systems made of two different carbon grids (one impregnated and one unimpregnated) and employing five different mortars were compared to assess the influence of both grid and mortar on the mechanical properties of the reinforcement. Tensile tests were carried out with a displacement and strain monitorization using Digital Image Correlation (DIC). The results reveal a remarkably better performance of the systems with impregnated grid, especially when combined with high strength mortars. The enhancement was particularly observed in terms of ultimate tensile strength, crack spacing, existence of a trilinear stress–strain curve, and efficiency factor (exploitation of the fibres in the composite).

Dynamic structural responses of high-performance fiber-reinforced cement composites panels subjected to high-velocity projectile impact loadings

Dynamic structural responses of high-performance fiber-reinforced cement composites panels subjected to high-velocity projectile impact loadings

Progressive collapse assessment of reinforced concrete (RC) buildings with high-performance fiber-reinforced cementitious composites (HPFRCC)

The susceptibility of concrete beam-column joints in reinforced concrete (RC) frame structures to progressive collapse can result in severe damage or collapse. High-performance fiber-reinforced cementitious composites (HPFRCCs), as a strain-hardening material, can be used instead of ordinary concrete to improve RC frame buildings' performance. This study evaluates the effects of using HPFRCC in beam-column joints on the behavior of RC frame structures subjected to progressive collapse. Five RC buildings with moment-resisting frame systems were studied for this purpose, one with ordinary concrete beam-column joints and the others with HPFRCC beam-column joints and varying quantities of reinforcement on beams and columns. The buildings were evaluated using 3D modeling with OpenSees finite element software and removing a corner column using the alternative load path method (ALP) per GSA regulations. The results show that using HPFRCC in beam-column joints can improve the robustness of RC frame buildings to progressive collapse by increasing beam-column joint stiffness, load-bearing capacity, and the ability to withstand large deformations. Furthermore, damages caused by the sudden removal of corner columns in buildings reveal that the use of HPFRCC in beam-column joints results in a reduction in damages, even in buildings with a reduced quantity of reinforcements (buildings H1 and H2), even though a significant decrease in the number of longitudinal reinforcements of beams and columns in the building with HPFRCC beam-column joints (building H3) can result in severe damage to the connections.

Secondary Natural Fibre-Reinforced Cementitious Composites: A Comprehensive Review

Construction activities use millions of tonnes of conventional, non-renewable building materials and release 30% of the world's CO2 emissions. Green building materials that are easily accessible, affordable, renewable, recyclable, and thus sustainable should be promoted in order to reduce these issues. The use of waste from secondary natural fibre (SNF) as a biological replacement for synthetic fibre in cementitious composites is reviewed in this research in light of recent trends. The varieties and classification of SNF, as well as its chemical make-up and physical and mechanical characteristics, were highlighted in the article. This study also discussed the mechanical, thermal, and durability characteristics of secondary natural fibre cementitious composites (SNFRC), as well as ways to enhance the durability of SNF in cementitious composites and new trends and applications for SNFRC. The report offered various areas for more research in SNFRC as a conclusion.

Terahertz (THz) Wave Imaging in Civil Engineering to Assess Self-Healing of Fiber-Reinforced Cementitious Composites (FRCC)

Terahertz (THz) Wave Imaging in Civil Engineering to Assess Self-Healing of Fiber-Reinforced Cementitious Composites (FRCC)

Rheological and Mechanical Properties of Kenaf and Jute Fiber-Reinforced Cement Composites

This study investigated the rheological and mechanical properties of cement composites with kenaf and jute fibers for use in shotcrete. The length and volume fractions of the fiber were varied; the rheological properties were analyzed in terms of air content, compression and flexural tests were conducted, and the degree of fiber dispersion was assessed using fluorescence microscopy. The rougher surfaces of the jute fibers led to a higher yield stress and viscosity of the composite compared to the kenaf fibers. The use of 10-mm-long jute fibers at 2.0% volume fraction led to optimal rheological properties while 30-mm-long jute fibers at 1.0% resulted in the worst properties. The yield stress and plastic viscosity exhibited positive and negative correlations with the fiber volume fraction, respectively. This was likely because of the bridging and fluid actions of the bubbles at higher fiber content. For a given fiber content, only the yield stress increases with an increase in fiber length. Although all the mechanical properties deteriorated (compressive strength decreased from 27.5 to 6 MPa, and flexural strength deteriorated from 6.2 to 1.8 MPa), the mixtures failed in a ductile manner. Using 10-mm-long kenaf fibers at 2.0% induced optimal fiber dispersion, whereas the minimum dispersion-coefficient value was found for 5-mm-long kenaf fibers at 0.5%.

Effect of nanosilica on fiber pullout behavior and mechanical properties of strain hardening ultra-high performance concrete

The bond properties between the fiber and matrix are a critical factor that affects the tensile properties and toughness of fiber-reinforced cementitious composites. This research aims to provide an effective method to improve the tensile properties of ultra-high performance concrete (UHPC) with strain hardening characteristics. The compressive, flexural, and tensile behavior was measured on UHPC with two geometric configurations of steel fibers and four nanosilica (nano-SiO2) mass fractions (0/1/3/5 wt% substitution rate of cement mass). The pull-out load-slip responses of steel fibers were also captured. In particular, determined the effect of fiber slip response on tensile properties of UHPC, then calculate elastic, strain hardening, and softening tensile parameters. Furthermore, the SEM, EDS, MIP, and XRD tests were used to reveal the enhancement mechanism of interfacial bonding performance and mechanical properties. The results show that the compressive and flexural strength peaks at 3 wt% of nanosilica, owing to nanosilica effectively ameliorating the pore structure and promoting the hydration process of the matrix. While the fiber pullout behavior and tensile properties show better performance at 5 wt% associated with increased hydration products attached to the fiber surface and more severe scratches after being pulled out. Notably, the addition of nanosilica endows strain hardening properties to UHPC containing straight fibers as well as increases the tensile toughness of UHPC containing hooked fibers due to the reinforcement of the matrix tunnel surrounding the steel fibers.

Impact of the Hybrid-Aluminum Additive on the Hydration Kinetics of Portland Cement in Fiber-Reinforced Cement Composites

A hybrid-aluminum additive (HAA) synthesized from industrial wastes including aluminum dross and flue gas desulfurized (FGD) gypsum was used as an additive for fiber-reinforced cement composites (FRCC). The impact of this additive on hydration kinetics was observed by the temperature change over time for the various HAA mixtures with ordinary Portland cement (OPC), sand, cellulose fibers, polyvinyl alcohol (PVA) fibers, and water, based on the method described in ASTM C186-98. The results showed that the hydration kinetics of OPC in the FRCC was improved by using HAA. In addition, when the amount of HAA was at 3% of the OPC weight, the hydration reaction rate was improved by 41%. The HAA additive acted as an accelerating agent by shortening the setting time and enhancing the temperature of the hydration reaction. This suggests that the cement paste can set faster, reducing the cycle time in FRCC processing. Even though further addition of the HAA increased the reaction rate, the setting time of OPC was too short to form a green sheet for the actual production of FRCC on an industrial scale. In addition, the heat released during the test, representing by the temperature change of the sample, was too high which could have a negative impact on the finished FRCC products.

Tensile Response of Reinforced Ultra-High-Performance Fiber-Reinforced Cementitious Composites: Modeling and Design Recommendations

Tensile Response of Reinforced Ultra-High-Performance Fiber-Reinforced Cementitious Composites: Modeling and Design Recommendations

Flexural and tensile properties of chemically treated guinea corn husk-cow hair hybrid fiber reinforced cement composite

Flexural and tensile properties of chemically treated guinea corn husk-cow hair hybrid fiber reinforced cement composite

Electromechanical response of strain-hardening fiber-reinforced cementitious composites (SH-FRCCs) under direct tension: A review

Electromechanical response of strain-hardening fiber-reinforced cementitious composites (SH-FRCCs) under direct tension: A review

An improved calibration of Karagozian & Case concrete/cementitious model for strain-hardening fibre-reinforced cementitious composites under explosion and penetration loadings

The ultra-high tensile capacity of strain-hardening fibre-reinforced cementitious composites makes them promising for impact dynamics applications, however, there is a lack of reference for taking the parameters of the constitutive model of materials in numerical simulations. In this study, the Karagozian & Case concrete/cementitious model parameters for strain-hardening fibre-reinforced cementitious composites were comprehensively and systematically calibrated. Multiaxial behaviour, crack-bridging constitutive relations, strain-rate effects, regularization of damage evolution parameters, and parameters scaling method for wide-range strength of materials were all considered and carefully discussed. The calibrated parameters were validated using low-velocity drop-weight impact tests, near-field explosion tests, and high-speed penetration tests. In this study, the traditional element erosion method and meshless/particle methods of Smoothed Particle Galerkin (SPG) method were used for failure analysis in penetration and explosion models. The results show that the calibrated parameters accurately predict the cratering and scabbing diameters and failure modes of explosion tests with the element erosion method. Furthermore, the residual velocity of the projectile and crack patterns of targets were also predicted with good precision with both element erosion and SPG methods. However, in the simulations of low-velocity impact tests, the predictions of maximum deflection were acceptable, and the errors in residual deflection were significant due to the inherent weakness of the material constitutive model.

A framework for improving bridge resilience and sustainability through optimizing high-performance fiber-reinforced cementitious composites

High-performance fiber-reinforced cementitious composites (HPFRCC) exhibit benefits in improving infrastructure resilience but often compromise sustainability due to the higher upfront cost and carbon footprint compared with conventional concrete. This paper presents a framework to improve bridge resilience and sustainability through optimizing HPFRCC. This research considers ultra-high-performance concrete and strain-hardening cementitious composite, both featuring high mechanical strengths, ductility, and damage tolerance. This paper establishes links between bridge resilience, bridge sustainability, mechanical properties of HPFRCC, and mixture design. The investigated mechanical properties include the first crack stress, the ultimate tensile strength, and the ultimate tensile strain. With the established links, sustainability is maximized while resilience is retained by optimizing HPFRCC mixtures. The framework is implemented into a case study of a bridge that collapsed during construction. Results show that use of HPFRCC enhances resilience, and HPFRCC mixtures can be engineered to minimize the material cost and carbon footprint while retaining high resilience.

Autogenous self-healing of ultra-high-performance fiber-reinforced concrete with varying silica fume dosages: Secondary hydration and structural regeneration

Secondary hydration is the main driving force of autogenous self-healing and directly impacts the closure of cracks in damaged cementitious materials. In fiber-reinforced cement composites, secondary hydration also dominates the regeneration of the fiber-matrix interface during the self-healing processes. As an important factor influencing the cement hydration, silica fume (SF) addition can be crucial to the self-healing performance of cementitious materials and composites. In this paper, the effect of SF on the autogenous self-healing of ultra-high-performance fiber-reinforced concrete was investigated. With a ≥20% SF addition, the secondary hydration the cement matrix adjacent to the cracks was accelerated. The dissolution of amorphous silica and the formation of Si-containing healing phases was observed. These effects predominated the closure of the mouth and the inner part of the cracks. SF addition also enhanced the regeneration of fiber-matrix interface by promoting the growth of self-healing products in these areas. The closure of cracks and the regeneration of fiber-matrix interface are both responsible for the restoration of flexural properties.

Numerical modelling of bond behavior between rebar and high-strength fiber-reinforced cementitious composites (HSFRCC) for inter-module joint in modular construction

In modular construction, the optimization of joint design has always been a major challenge. The joint size is primarily governed by rebar-concrete bond strength, as tensile stress is transferred from one lapped bar to the other through the concrete substrate. The complex mechanism of rebar-concrete bond degradation is dependent on both the property of the bonded interface and the damage of surrounding concrete. By virtue of its exceptional mechanical performance that contributes to the enhancement in rebar bond property, high-strength fiber-reinforced cementitious composites (HSFRCC) are often adopted in precast construction to locally replace conventional concrete in the joint area. In a previous study, the authors explored the application of HSFRCC in modular construction and developed a novel inter-module joint design. Based on the mechanical properties of the materials and the explicit geometry of the bonded interface, a 3D finite element model was introduced and showed good agreement with pull-out test results. Building on the preceding works, this paper aims to further validate the numerical model and demonstrate its general applicability using HSFRCCs with different steel fiber content. With the validated model, the effects of rebar bond length, HSFRCC cover thickness, and thickness of steel plate confinement on the bond performance are investigated in parametric studies, which establishes the basis for formulating a rational design approach for the proposed joint method.

Impact simulations for high-performance fiber-reinforced cement composites using a coupled finite element and smoothed particle Galerkin method

This paper presents a projectile impact analysis of high-performance fiber-reinforced cement composite (HPFRCC) structures based on the coupling of the finite element method (FEM) and the smoothed particle Galerkin (SPG) model in the LS-DYNA program. The K&C material model is calibrated for the HPFRCC. Through a quasi-static analysis using the calibrated model, the criteria for the element size of a FEM and the nodal particle distance of the SPG model are determined. Numerical simulations of the coupled SPG-FEM model are conducted to predict the structural responses of HPFRCC structures subjected to high impact velocities ranging from 342 m/s to 808 m/s. The results for the coupled model are compared with experimental data as well as numerical results for a pure FEM model to determine the relative accuracy and efficiency of a coupled FEM and SPG model for the large deformation problem. The convergence of the numerical results is also investigated in terms of the residual velocity and penetration depth. Moreover, the effects of various parameters on the models are discussed through a sensitivity analysis, and suitable parameter ranges that improve the accuracy of the numerical results are suggested.

Strength Design of Ultra-High-Performance Fiber-Reinforced Cementitious Composites Using Local Ecological Admixture

The ultra-high-performance fiber-reinforced cementitious composite (UHPFRC) is a new generation of building material with extremely high mechanical strength and durability, which can be used for ultra-high, thin-wall or long-span construction, that prolongs the service life of construction in severe environments. In this study, UHPFRC was prepared with a high range of local ecological admixture to decrease the material’s cost and the environmental impact. Raw materials’ proportions, water/binder ratio, fiber-volume contents, and hybrid-fiber ratio were studied on the property improvement of UHPFRC, and an F-test analysis was induced to reveal the important significance on compressive strength. The results demonstrated that the compressive strength of 237.8 MPa was achieved with mineral admixture substitution over 40%. The particle-packing density and the binder reactivity both succeeded on the compressive strength. Water/binder ratio determined the hydration degree and the flowability of UHPFRC, which affected compressive strength through hydration products and microstructure. Also, compressive strength was more sensitive with hybrid-fiber than fiber-volume content. The order of importance for compressive strength was powder proportion > hybrid-fiber ratio > fiber-volume content > water/binder ratio.