Cementitious Matrix Composites Research Articles

Dynamic Stability of Polypropylene FiberReinforced Concrete

The paper presents a comparative fatigue analysis of conventional and fiber-reinforced cement matrix composites under few repeated loads. Consideration of low-cycle fatigue at a design stage.Purpose: The aim of the work is to evaluate fatigue changes in conventional and fiber-reinforced cement matrix composites during repeated loads with zero asymmetry coefficient and 0.6–0.9 amplitude. Subjected to low cyclic loads are ordinary concrete and polypropylene fiber reinforced concrete with an equivalent diameter 0.8 mm and 40 mm length with 1.5 vol.% reinforcement.Methodology: Automated multi-factor strain control indicating structurally relevant components. Dynamic tests are performed on an Instron 5989 testing machine using a hard mode of the load change at 0.04 mm/s strain rate. Strain is measured in two directions. Control parameters are recorded after each 10 cycles until 300 cycles. Residual strain and cyclic kinetics of incremental strain are the key parameters of internal resistance.Value: Detected are the higher damping ability of the fiber composite and higher fatigue resistance potential at the stress-state fluctuation.

Study on the Correlation Between Mechanical Properties, Water Absorption, and Bulk Density of PVA Fiber-Reinforced Cement Matrix Composites

Fiber-reinforced cement matrix composites (CMCs) have gained significant attention due to their ability to enhance material properties for use in demanding environments. This study investigated the workability and mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced CMCs, focusing on compressive strength, split tensile strength, and flexural strength. It also assessed water absorption capacity through immersive water absorption tests using cubes and capillary water absorption tests using cylinders, alongside bulk density measurements for both shapes. The results indicated that the dosage of PVA fibers significantly influences the workability of CMCs, while the water-to-binder ratio has a minimal effect. Increasing the dosage of PVA fibers in CMCs from 0.5 vol.% to 1 vol.% led to a decrease in several properties: compressive strength decreased by 13.38%, split tensile strength by 21.05%, flexural strength by 9.23%, bulk density of cube samples by 4.14%, and bulk density of cylindrical sample by 6.36%. Conversely, both immersive water absorption and capillary water absorption increased, rising by 10.87% and 77.71%, respectively. Compressive strength was found to increase with the bulk density of the cubes and to decrease with rising immersive water absorption. Similarly, split tensile strength increased with the bulk density of the cylinders and decreased as capillary water absorption increased. Strong correlations were observed among three key pairwise combinations: the bulk density of cubes and immersive water absorption (R2 = 94%), compressive strength and bulk density of cubes (R2 = 96%), and compressive strength and immersive water absorption (R2 = 92%). Furthermore, the analysis and comparison of carbon fiber-reinforced and PVA fiber-reinforced CMCs will provide important references for the field, especially in cases where material availability or cost varies.

Molecular dynamics simulation of nanocellulose and cement matrix composites

Molecular dynamics simulation of nanocellulose and cement matrix composites

SnO wrap on SnS reinforced thermoelectric properties of CF/EG cement matrix composites

In this study, SnO wrap on SnS was prepared and incorporated into carbon fiber/expanded graphite (CF/EG) cementitious composites by the coating process. The effects of different SnO wrap on SnS coating ratios and contents on the microstructures of CF/EG cementitious composites were investigated and discussed, and the thermoelectric properties of SnO wrap on SnS CF/EG cementitious composites were systematically investigated in the temperature range of 35–70 °C. The results show that the coating ratio and content of SnO wrap on SnS have a significant effect on the thermoelectric properties of CF/EG cementitious composites. It is noteworthy that when the SnO wrap on SnS is 2:1, the thermoelectric properties of its cementitious composites are greatly improved. For example, when it is added at 1.0 wt%, the conductivity is 2.27 S/cm, the Seebeck coefficient is 41.90 µV/°C and the power factor is 0.38 µW·m−1K−2. The addition of SnO wrap on SnS to CF/EG cementitious materials generates a large number of interfaces, and the presence of high-density interfaces hinders the motion of carriers, which leads to the scattering of carriers at the interfaces and enhances the Seebeck effect in cementitious composites. Therefore, SnO wrap on SnS has great potential for thermoelectric applications.

Mechanical characteristics, microstructural evolution, and reinforcement mechanisms for a cement-matrix nanocomposite

Mechanical characteristics, microstructural evolution, and reinforcement mechanisms for a cement-matrix nanocomposite

Effect of ICCP on tensile performance of carbon fiber bundles in seawater sea-sand cementitious matrix

Effect of ICCP on tensile performance of carbon fiber bundles in seawater sea-sand cementitious matrix

Effect of ICCP on tensile performance and piezoresistive effect of CFRCM plates

Effect of ICCP on tensile performance and piezoresistive effect of CFRCM plates

Fatigue and post-fatigue behavior of FRCM-concrete specimens under direct shear and bending conditions

Fatigue and post-fatigue behavior of FRCM-concrete specimens under direct shear and bending conditions

Restoration of two-span RC beams with severely corroded reinforcement using C-FRCM composites

Restoration of two-span RC beams with severely corroded reinforcement using C-FRCM composites

Simplified Procedure to Determine the Cohesive Material Law of Fiber-Reinforced Cementitious Matrix (FRCM)-Substrate Joints.

Fiber-reinforced cementitious matrix (FRCM) composites have been largely used to strengthen existing concrete and masonry structures in the last decade. To design FRCM-strengthened members, the provisions of the Italian CNR-DT 215 (2018) or the American ACI 549.4R and 6R (2020) guidelines can be adopted. According to the former, the FRCM effective strain, i.e., the composite strain associated with the loss of composite action, can be obtained by combining the results of direct shear tests on FRCM-substrate joints and of tensile tests on the bare reinforcing textile. According to the latter, the effective strain can be obtained by testing FRCM coupons in tension, using the so-called clevis-grip test set-up. However, the complex bond behavior of the FRCM cannot be fully captured by considering only the effective strain. Thus, a cohesive approach has been used to describe the stress transfer between the composite and the substrate and cohesive material laws (CMLs) with different shapes have been proposed. The determination of the CML associated with a specific FRCM-substrate joint is fundamental to capture the behavior of the FRCM-strengthened member and should be determined based on the results of experimental bond tests. In this paper, a procedure previously proposed by the authors to calibrate the CML from the load response obtained by direct shear tests of FRCM-substrate joints is applied to different FRCM composites. Namely, carbon, AR glass, and PBO FRCMs are considered. The results obtained prove that the procedure allows to estimate the CML and to associate the idealized load response of a specific type of FRCM to the corresponding CML. The estimated CML can be used to determine the onset of debonding in FRCM-substrate joints, the crack number and spacing in FRCM coupons, and the locations where debonding occurs in FRCM-strengthened members.

FRCM Confinement of Masonry: Strain Model Assessment and New Proposals.

One of the main limitations to the use of fabric-reinforced cementitious matrix (FRCM) composites for the external confinement of masonry is the lack of accurate formulas for estimating the compressive strength and ultimate strain of confined members. With the aim of providing a contribution on the topic, the authors have been carrying out studies on the FRCM-confined masonry for some time and, in a recent study, they proposed some formulations for the prediction of compressive strength. In continuity to that work, an analytical study on the ultimate strain of FRCM-confined masonry is presented in this paper, and preliminary models were derived by considering a wide experimental database compiled from the technical literature. The accuracy of the found relationships was examined based on a comparison with the few formulas published in the literature or reported in international guidelines. To this purpose, it is worth highlighting that the current Italian Guidelines CNR-DT 215/2018 do not provide indications about the estimation of the ultimate strain of FRCM-confined masonry, and the study proposed here attempts to provide a contribution to the mentioned document.

Mechanical Properties of Cement Matrix Composites Reinforced with Polyoxymethylene Fibers of Different Lengths

Mechanical Properties of Cement Matrix Composites Reinforced with Polyoxymethylene Fibers of Different Lengths

Available measurement methods to evaluate the fiber and matrix bond performance of FRCM composites

Available measurement methods to evaluate the fiber and matrix bond performance of FRCM composites

Shear strengthening of RC beams with U-wrapped FRCM composites: assessment of current design guidelines

Shear strengthening of RC beams with U-wrapped FRCM composites: assessment of current design guidelines

Experimental and numerical bond behavior of PBO FRCM tested using a pull-out set-up

Experimental and numerical bond behavior of PBO FRCM tested using a pull-out set-up

Bond behavior between carbon fabric reinforced cementitious matrix (FRCM) composites with added short fibers and concrete substrates

Bond behavior between carbon fabric reinforced cementitious matrix (FRCM) composites with added short fibers and concrete substrates

Influence of severe thermal preconditioning on the bond between carbon FRCM and masonry substrate: Effect of textile pre-impregnation

Influence of severe thermal preconditioning on the bond between carbon FRCM and masonry substrate: Effect of textile pre-impregnation

Study on the physicochemical properties of Chinese PVA fibers: Toward low-cost cement-based composites

Engineered Cementitious Composites (ECC) reinforced by Japanese Polyvinyl Alcohol (PVA) fiber showed excellent tensile ductility, which attracted much attention in the field of civil engineering in recent years, but the application was still limited by cost. There were quite a few kinds of low-priced PVA fibers in China, with a tremendous difference in physical and chemical properties. In this paper, a variety of typical PVA fibers produced in different regions in China were compared with the products imported from Japan to analyze the performance differences, especially the dispersion and enhancement effect in fiber reinforced cement matrix composites. Combining with the physical and chemical characteristics of each fiber, the relationship between the characteristics of fibers and the properties of composites was summarized. The experimental results illustrated the strength and interface characteristics of PVA fibers were the dominating influencing factors to the bending and tensile properties of PVA-ECC, while hardly affected the compressive strength. Insufficient intrinsic strength of fibers significantly decreased bending resistance and tensile strength. Excessive oil agent treated PVA fibers performed lower interfacial reaction with the cement matrix, meanwhile original PVA fiber with high hydrophilicity was not conducive to the dispersion and bridging function. The appropriate interface treatment approach could guarantee the fibers to achieve the sliding pull out bridge connection, and also meet the high slip strengthening effect, leading to the multi-seam cracking and strain hardening characteristics of ECC material. This work provided the preparation of low-cost cement-based composites, guiding the selection of fiber raw materials in ECC.

Shear capacity prediction for FRCM-strengthened RC beams using Hybrid ReLU-Activated BPNN model

Shear capacity prediction for FRCM-strengthened RC beams using Hybrid ReLU-Activated BPNN model

Analysis of probable consequences of cement composite frost destruction

The article presents an analysis of variations in the internal resistance of standard and fiberreinforced cement composites under non-stationary low-temperature and humidity effects. Various aspects of the response kinetics of prismatic samples in the monotonous compression mode are considered. The sample set included control samples and those subjected to cyclic freezing and thawing according to their standard frost resistance. Test samples (100 × 100 × 400 mm) were made of conventional (B series) and fiber-reinforced (FB, polypropylene fibers df = 0.8 mm, lf = 40 mm, µf = 1.5 vol%) concrete with a component ratio of cement: sand: crushed stone: water = 1:1.42:3.57:0.55. The accepted base of T-W cycles corresponded to the standard concrete grade in terms of frost resistance, established in control tests (F200). Static tests of composites were preceded by low-temperature exposures according to an accelerated method for assessing frost resistance with a temperature decrease down to minus 35℃ and thawing in a 5% NaCl solution. Samples were automatically loaded (Instron 5989 test complex) according to a special program with a constant deformation rate of 5·10-5 mm/s and continuous recording of deformations. Significant differences were observed in the strength kinetics, magnitude and structure of deformations, along with a high sensitivity and quantitative informativeness of the significant parameters of the strength kinetic concept for solid bodies. The expediency of a differentiated approach to the selection of calculation models and criteria for the temperature and humidity transformations of cement-matrix composites, which takes operational requirements into account, is substantiated.