•Quasi-static and dynamic splitting tests of fiber reinforced concrete are conducted.•Splitting tensile strength and failure mode of fiber reinforced concrete are studied.•Influence of different ...fiber mixing ratios on splitting tensile strength is analyzed.•Variation of splitting tensile strength with the force loading rate is discussed.•The effect of fiber content on the loading rate-enhancing effect is explained.
The influence of steel-polypropylene hybrid fibers on the tensile properties of high-strength concrete is investigated by quasi-static and dynamic Brazilian disc splitting tests. The failure modes of fiber reinforced concrete specimens and the influence of different fiber mixing ratios on the splitting tensile strength of the specimens are analyzed. The research results indicate that the plain concrete and single-doped polypropylene fiber concrete specimens show straight cracks along the loading line during the experimental process, showing the brittle failure characteristics; while the single-doped steel fiber concrete and hybrid fiber concrete specimens show more bifurcated micro-cracks along the loading line, showing the ductile failure characteristics. The splitting tensile strength of concrete specimens increases with the increase of steel fiber content, and increases first and then decreases with the increase of polypropylene fiber content. The mixed use of steel fiber and polypropylene fiber not only improves the splitting tensile strength of concrete specimens, but also reduces the risk of brittle failure of concrete. Especially when the steel fiber content is S2 (2.5%), the hybrid of steel-polypropylene fibers has a great improvement effect on the splitting properties of concrete specimen. In addition, it is found that the splitting tensile strength of fiber reinforced concrete specimens increases with the increase of force loading rate, showing the enhancing effect of loading rate. Comparing the rate-enhancing effect of specimens with different fiber content, it is found that the change of fiber content has a certain influence on the loading rate-enhancing effect of specimens.
•Self-healing concrete was prepared by pre-wet with SHA.•The compressive strength of self-healing concrete with SHA of 0.6 m3 was 36.1 MPa.•SHA can improve the frost resistance of concrete.
The ...existing research on self-healing concrete based on Microbial-induced carbonate precipitation (MICP) focuses on the crack-healing effect. However, there are limited studies on the physical and mechanical properties of such concretes. In this paper, the effects of different mixing methods and self-healing agent (SHA) particle size on SHA crushing rate, apparent density, and mixture strength are experimentally investigated. The optimal particle size of the SHA was determined as 1–2.36 mm. Also, it was shown that the SHA should be put in first when mixing. Considering the particle size and mixing method, self-healing concrete specimens with two different sizes and five dosage gradients were prepared. The resulting change in compressive strength and splitting tensile strength of concrete with the SHA amount was determined. Also, the change in frost resistance of specimens after 200 freeze–thaw cycles was evaluated. The results indicate that the compressive strength and splitting tensile strength of concrete gradually decrease with the increasing amount of the SHA. The splitting tensile strength decreases slightly compared with the compressive strength of self-healing concrete. However, the frost resistance of concrete increases firstly and then decreases with the increase of SHA content. Therefore, when the content of the SHA is 0.4 m3, the frost resistance of concrete is the best.
This study focused on coupled effect of temperature and impact loading on tensile strength of an ultra-high performance fibre reinforced concrete (UHPFRC), which retains 69% of its original ...compressive strength after exposure to 1000 °C. The relationship between tensile strength and compressive strength was investigated under the coupled action since temperature may have different effects on them. Static tests and dynamic tests using a self-designed Split Hopkinson Pressure Bar (SHPB) system were conducted at temperatures 20, 200, 400, 600 and 800 °C. Comparison was made between tensile strength and compressive strength of UHPFRC obtained in hot state and cooled-down state. It was found splitting tensile strength fell sharply beyond 400 °C but still retained 41% of its original strength at 800 °C, well above other concretes. Temperature and combined action of elevated temperature and impact loading have different effects on splitting tensile strength and compressive strength.
•Segregation degree is remarkably dependence on the volume fraction and size of Sat-SAP.•Porosity and pore size have obvious influence on the mechanical properties.•The modified stress-strain model ...accurately describes the compression behavior.•Correlations between porosity, pore size and mechanical behaviors are investigated.•The relationship between compressive and splitting-tensile strengths is studied.
Cellular concrete with millimeter-sized pores has recently been suggested as an attractive material in engineering fields because of its specific material properties. However, few studies have assessed the effects of porosity, pore size and their interaction on the splitting tensile strength of cellular concrete. A comprehensive understanding of the mechanical properties of cellular concrete is needed prior to its application in engineering. The effects of porosity (0, 5, 10, 15, 20, 25 and 30%) and pore size (0, 1, 4.5, 7.5, 9.5 and 12.0 mm) on the segregation, compressive strength and splitting tensile strength of cellular concrete fabricated using a saturated superabsorbent polymer (Sat-SAP) and their relationships are investigated in this study. The incorporation of SAP significantly increases the segregation characteristic of cellular concrete. The segregation is particularly high for porosities higher than 15%, and the lowest segregation is observed for pore sizes of 4.5–7.5 mm. The compressive and splitting tensile strengths of cellular concrete decrease gradually with increasing porosity and pore size, but the effect of pore size on the mechanical properties of cellular concrete is very weak at pore sizes greater than 9.5 mm and porosities less than 10%. Moreover, a modified method for describing the stress-strain curve and calculating the elastic modulus of cellular concrete is suggested. Based on these results, some empirical formulas are proposed or modified to better analyze the segregation characteristics, accurately describe the stress-strain curve, and effectively predict the mechanical properties of cellular concrete with different porosities and pore sizes and their relationship.
•Splitting tensile strength of concrete was predicted using different methods.•Plain and steel fiber-reinforced concretes were studied.•ML techniques have definitely a better performance compared ...with NLR.•Compressive strength is the most statistically significant parameter.
Compressive strength (fc) and splitting tensile strength (fspt) of concrete are two important parameters in structural design. Due to the complexity, cost, and time-consuming nature of performing tensile tests, many researchers are interested to predict the value of this property in a simplified but accurate manner. This paper presents non-linear regression (NLR) analysis, artificial neural network (ANN), support vector machine (SVM) and M5′ model tree (MT) techniques to predict the tensile strength (fspt) of concretes made with and without steel fiber reinforcement. Error measures were used to compare the performance of different models including the models developed in this study and those developed by other researchers. Results indicated that non-linear regression analysis, artificial neural network, support vector machine, and model tree algorithms can predict the splitting tensile strength of concretes made with and without steel fiber reinforcement with satisfactory accuracy. However, machine learning techniques such as ANN, M5′ model tree and SVM provided superior models compared to NLR analysis.
It is aimed to research the effects of electronic plastic waste (e-plastic) on the mechanical properties of polymer concrete. E-plastic was used as a part of the filling materials (quartz sand and ...gravel) to obtain polymer concrete in this study. Unsaturated polyester resin material has been chosen as the polymer material and used as binder in polymer concrete production. Resin/filling material ratio has been determined as 10–90%, 15–85% and 20–80%, e-plastic/filling material ratio has been decided to be 0%, 5%, 15% and 25%. 28-Day of axial compressive, flexural and splitting tensile strength values of the test samples were evaluated. The increase in the ratio of resin, increases the compressive strength while it does not cause a dramatic increase or decrease in the flexural and splitting tensile strength. Compressive, flexural and splitting tensile strength values decrease as the ratio of e-plastic increases. On the other hand, electronic plastic waste increases the polymer concrete’s ductility. Experimental study shows that ideal resin ratio and ideal e-plastic ratio values are 15% and 5%, respectively.
•Characteristics of Carbon fibre and comparison with other fibres.•Incorporation of Carbon fibre into conventional concrete.•Changes in mechanical characteristics and workability due to fibre ...addition.•Summary and future directions on carbon fibres in conventional concrete.
Though concrete is considered as the most widely used construction material, its limitations in terms of lower flexural and tensile strength, which may cause structural failure under tension and shear without a warning due to its brittle nature, directed research on enhancing its tensile and flexural characteristics further. Currently, various fibre types are used in the construction industry to mitigate said limitations of concrete and enhance characteristics including ductility, toughness, flexural and tensile strength. Steel fibre takes the higher fraction amongst commonly used fibre types in the present construction industry. Corrosion of steel fibre causes degradation of its ductility and performance with time. Carbon fibres’ higher tensile strength, low density and corrosive resistance properties make it a better alternative despite its higher cost. Currently, carbon fibre are mainly used in the construction industry for structural repair and rehabilitation works. Studies reveal that carbon fibre-reinforced concrete (CFRC) has a promising future, but the usage of carbon fibre in concrete as a reinforcement is currently limited and is still in the development stage. This paper provides an overview of carbon fibre and its characteristics, application and properties of CFRC. This review also addresses the state-of-the-art literature published on comprehensively analysing the variation of selected mechanical properties of CFRC with different fibre dosages compared with conventional concrete, particularly compressive strength, flexural strength and splitting tensile strength, workability, and including limitations of present literature for future research and development.
Mine tailings-based geopolymer was proved to be successfully created with enhanced strength for potentially construction and building materials applications. Through geopolymerization, the mining ...wastes can be reused and the storage, economic, and environmental issues can be mitigated. However, the geopolymerization effect was relatively limited comparing to the ordinary Portland concrete. Therefore, the additions of amorphous supplementary fly ash were considered in the paper. In this study, class F fly ash was utilized as an amorphous additive and the additional aluminum source to adjust the Si: Al ratio for better geopolymerization effects. To better understand the mechanical and fracture behavior of the geopolymer after adding fly ash, the Brazilian indirect tensile tests were then conducted to evaluate the influence of different fly ash additions, 5%, 10%, 15%, and 20%, on the tensile strength of the geopolymer. Meanwhile, besides the load-displacement relationships, the digital image correlation was used to investigate the crack initiation and propagation in the geopolymer disks with respect to different fly ash additions. The crack evolution was evaluated from the full-field strain field from digital image correlation. Crack opening displacements, failure patterns, and strain evolutions for the geopolymer disks with different fly ash additions were examined. Results showed that, under the presented sample curing condition, the geopolymer with 15% fly ash addition had the largest tensile strength. Geopolymer disks without and with lower fly ash additions had plastic deformation prior to the peak load that can obviously be classified into three different stages. The geopolymer made without and with lower fly ash additions had both tensile and shear crack modes.
Rubber concrete: Mechanical and dynamical properties Gerges, Najib N.; Issa, Camille A.; Fawaz, Samer A.
Case Studies in Construction Materials,
December 2018, 2018-12-00, 2018-12-01, Volume:
9
Journal Article
Peer reviewed
Open access
The purpose of this paper is to report on an experimental study that explores the effect of using recycled rubber powder as an alternate fine aggregate in concrete mixes. Natural sand in the concrete ...mixes was partially replaced by 5%, 10%, 15%, and 20%. Physical properties such as the density, the compressive strength, the fresh concrete properties, the split-tension, and the impact load capacity are examined. The results revealed a decrease in the compressive strength of concrete cylinders containing rubber. The dynamic performance of the rubber concrete is of high importance because of its high resilient nature, as the rubber particles that are included in the concrete have a positive effect on the dynamic performance. The conclusions that were derived from this research implicate potential applications where rubberized concrete can be efficiently used. Even though rubberized concrete mixture generally has a reduced compressive strength that may limit its use in certain structural applications, it possesses a number of desirable properties, such as lower density, higher toughness, and higher impact resistance compared to conventional concrete.
Geopolymer is emerging as a potential alternative material to the ordinary Portland cement (OPC) owing to its energy efficiency and environmental protection. However, the effect of the mix design ...parameters on the behavior of geopolymer concrete (GPC) produced using local metakaolin (MK) is not well established. This paper presents findings from a comprehensive experimental program to study the effect of various mix design parameters on the properties of fresh and hardened MK-based GPC. Seventeen mixes were cast in four groups to investigate the effect of four parameters, including sodium silicate to sodium hydroxide ratio, alkaline solids to MK ratio, aggregate content, and water to solids ratio on the properties of GPC. The investigated properties included workability, density (wet and dry), development of compressive strength with age, splitting tensile strength, ultrasonic pulse velocity, water absorption, and horizontal abrasion resistance. Besides, two reference OPC concrete mixes, equivalent to two MK-based geopolymer mixes, were tested for the sake of comparison. The test results were helpful in developing a better understanding of the behavior of MK-based GPC. Some useful models are proposed for predicting workability, splitting tensile strength, water absorption, and weight loss in abrasion for MK-based GPC. The test results were supplemented and confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis performed on some selected GPC mixes.
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