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This article discusses the influence of fiber types, including polyvinyl alcohol (PVA) fiber, polyethylene (PE) fiber, and steel fiber (SF), on the compressive strength, flexural strength, bending toughness, and tensile ductility of lightweight cement-based composites. The fiber dispersion and the microscopic morphology were assessed using fluoresc...
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Ultra-high performance cementitious composite (UHPCC) is an advanced composite material with superior compressive strength. UHPCC with low steel fiber content typically fails in a single-crack mode under tension, resulting in a high risk of catastrophic structural collapse and limiting its wide application. However, high steel fiber content adverse...
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... First, the maximum fiber bridging stress must be greater than the first-crack strength of the matrix. In addition, the complementary energy should be greater than the crack tip toughness of matrix [10]. While steel fibers sufficiently fulfill the former, fail to secure latter one. ...
This study aimed to achieve improved tensile performance of strain-hardening cementitious composites (SHCCs) utilizing various types of supplementary cementitious materials (SCMs) along with polyethylene (PE) fibers. Ground granulated blast-furnace slag (GGBS), silica fume (SF) and cement kiln dust (CKD) were used as SCMs, with at least two types of SCMs incorporated into SHCC to improve the mechanical performance through hybrid effect of SCMs. Additionally, reaction sensitivity and hydration products were evaluated using specimens manufactured under various curing temperatures (20 °C, 40 °C, and 90 °C) in consideration of different chemical compositions of the SCMs. It was confirmed that the 40 °C curing condition has the most positive effect on the compressive and tensile strengths of SHCC and strain capacity. The absence of SF led to a decrease in the strain capacity, significantly affecting the low strain energy density of the corresponding specimens. The specimen cured at a temperature of 40 °C after incorporating all three SCMs exhibited remarkably long-lasting strain-hardening behavior and achieved the highest strain capacity and strain energy density among all the specimens. Crack investigation after a tensile test was conducted to confirm traces of strain-hardening behavior, which improved a reliability of the mechanical tests. Moreover, derivative thermogravimetry analysis was performed to identify the residual amounts of hydrates affecting the performance of the cement composites. The high Ca(OH)2 residue was the basis for explaining insufficient hydration reactions, and the key factors for the low strength of some specimens was found in a low produced amount of CaCO3.
... In composite materials subjected to cyclic loading, the high stress zone prone to crack initiation is usually located at geometric discontinuities due to material mismatch. In fiber-reinforced composites, local fiber fracture is a typical defect [5][6][7]. The criteria for evaluating the fatigue strength of materials mostly depend on assumed structural models. ...
To comprehend the fatigue failure mechanism at the fiber discontinuity in fiber-reinforced composites, it is necessary to evaluate the local mechanical behaviors. The fatigue strength depends on the stress distribution at the fiber inclusion corner. An improved advanced finite element method (IAFEM) is proposed for the stress intensity factor (SIF) analysis at the fiber inclusion corner. In the IAFEM, the element stiffness matrix of singular inclusion corner element (SICE) is obtained, and the singular elastic field at the tip of the fiber inclusion is determined. The effects of load direction, fiber distribution, fiber geometry, and material properties on SIFs are analyzed numerically using the IAFEM. The difference in stress field distribution between two-dimensional and three-dimensional fiber inclusions is discussed. The IAFEIM and calculation results can provide reference for fatigue strength analysis and preparation of composite materials.
... However, amount of fibres that can be added is governed by workability; especially steel fibres [7]. Lately, numerous studies examined the fracture behaviour of LWC [8][9][10][11][12], but limited number of studies concentrated on the fibrous LWC [13][14][15][16][17][18][19][20][21][22]. The fracture energy (Gf) and stress intensity factor (K) are the chief parameters in fracture mechanics and they are of great importance in understanding crack initiation and propagation in concrete. ...
... A total of 88 points [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] were collected from peer-reviewed papers published in reputable journals. Initial data analysis revealed that some data points were unreliable with the overall trend and thus removed to improve the accuracy of the ANN model resulting in a total of 57 points used in the final analysis. ...
Determining the amount of energy required for crack propagation in concrete structures based on fracture mechanics principles is interesting. Fracture energy of concrete, as a quasi-brittle material, is an effective index for safe design of structures and failure behavior modelling. The nonlinear behavior of concrete in the fracture process is complex and there is a limited number of conclusive discussions on how to accurately predict the fracture energy using the existing estimating formula. Accordingly, this paper attempts to provide an innovative empirical approach for estimating the fracture energy of concrete. Based on a large quantity of experimental data, an artificial neural network (ANN) technique was used to construct connections between certain various effective parameters and specific fracture parameters, and therefore to predict the related fracture parameters. The fracture parameters of major interest in this study were the fracture energy (Gf) and stress intensity factor (K). The developed ANN-based prediction model combined the influence of the most significant characteristics influencing the fracture parameters with many important parameters never considered before.
... PVA and PP fiber cementitious composites are strong, lightweight, and deformable [19]. PVA fibers exhibit high adhesion to cement, whereas PP fibers exhibit a high degree of bridging capability [20,21]. The composite reinforcing properties of cellulose pulp and sulfate cellulose pulp significantly strengthen PVA fiber cementitious composites [22]. ...
Cementitious materials can be reinforced by adding different fibers. However, the effect of different fiber reinforcements on the mechanical properties of cement-based materials remains to be further studied. This paper studies the influencing factors of different fiber cement-based materials by combining experimental and theoretical methods. The tests used carbon fiber, glass fiber, and polyvinyl alcohol (PVA) fiber-reinforced cement-based materials. The addition ratios of fibers are 0%, 0.5%, and 1% by volume respectively. The compressive strength, bending strength, and drying shrinkage are studied for 3 to 28 d. The relationship between bending strength, compressive strength, dosage, and shrinkage is analyzed. The test results show that carbon fiber cement-based materials’ bending, and compressive strength increase the fastest, followed by glass and PVA fibers. The presented mathematical model accurately predicted the strength of the three fiber cement-based materials at different curing times. Compared to glass fiber and PVA fiber, carbon fiber shrinks less. It can be shown that the fiber significantly affects the early strength change of the fiber cement-based material by changing the shrinkage size of the fiber-cement-based material. The bending strength of carbon fiber, glass fiber, and PVA fiber increases with the increase of fiber volume fraction. On the other hand, the compressive strength increases and then decreases. Mechanical tests show that carbon fiber has the best reinforcement effect. The number of fibers, center spacing, and ultimate tensile length are all important factors that affect the strength of different fiber cement-based materials. Moreover, applied ABAQUS software established compression and bending finite element models of fiber-cement composites. It can predict the mechanical performance concerning fiber cement-based materials’ different types and volume fractions.
... As the BF density and absorption capacity of X-rays are close to that of concrete, the X-ray and CT methods are not suitable for the study of basalt fiber morphology; nonetheless, the CT method is a powerful tool to study the pore structure of concrete. Fluorescent tracking methods are mostly applicable to organic fibers, and require strict test conditions, as factors such as temperature and pH value will affect the accuracy of the test results [16,17]. For BF (non-organic fiber), fluorescent tracking methods are also not applicable. ...
... The tensile strength reached the maximum value when the BF content was also 3.0 kg/m 3 , approximately 2.62 MPa. The tensile strength of 3.0 kg/m 3 BF content increased by 16.6% compared to 0 kg/m 3 BF content, but the tensile strength of 7.5 kg/m 3 BF content decreased by 13.2% compared to 3.0 kg/m 3 BF content. The peak flexural strength was 3.9 MPa when the BF content was 3.0 kg/m 3 , and the flexural strength of 3.0 kg/m 3 BF content increased by 13% compared to 0 kg/m 3 BF content. ...
The orientation, distribution, and contact point density of BF (basalt fiber) in the concrete matrix play significant roles in the mechanical properties of BF concrete, but represent a weak point in current research. It is meaningful to study the morphological characteristics of BF in concrete. In this study, the transparent model test and joint blocking method were innovatively adopted to investigate the correlation of dosage with the BF morphological parameters and concrete mechanical properties. A focus on a BF dosage of 0–7.5 kg/m3 and the contribution index of fibers Cf was defined. Furthermore, NMR and CT techniques were used to observe the changes in the microstructure of BF concrete. The experimental results show that the BF contribution index Cf reaches the largest value when the BF content is around 3 kg/m3, approximately 2.7; in this case, the mechanical properties of BF concrete were also optimal, and the Cf was only 2.34 when the BF content was 7.5 kg/m3. NMR and CT test results show that there is a strong correlation between the BF morphological parameters and the distribution of pore structure in the concrete matrix. The overlapping contact of BF clusters led to the penetration of pores, which led the macro-pore proportion to increase dramatically. The increase in the macro-pore proportion is the main reason for the deterioration in concrete performance. In addition, these macro-pores may have adverse effects on the chloride ion permeability of BF concrete.
The sludge waste generated during the cutting of andesite stones is stored in dust form after drying. The wide range of use and consumption of andesite creates the problem of storage of the resulting waste. The main purpose of this study is to investigate the possibility of using in cement-based composites in order to sustainably dispose of these wastes and recover them to the economy. For this purpose, in the present study, the mechanical and microstructural properties of cement-based composites produced by replacing waste andesite with cement at 5%, 10%, 15%, 20%, 25% and 30% by weight were experimentally investigated. The results obtained at ages 28 day and 90 day revealed that the waste andesite dust increased the pore structure of the mixtures due to its porous structure, and therefore, the substitution of waste andesite dust with cement at low substitution rates up to 15% gave more positive results. More approximate results were obtained in terms of compressive, flexural and tensile strengths in the cement-based samples produced with the 5 wt % substitution ratio of waste andesite dust with cement compared to the reference sample. In addition, in the samples produced by substituting 30% by weight with cement, the deflection and tensile strain capacities were increased by approximately 2.31 and 1.88 times, respectively, compared to the reference sample.
