Dynamic Splitting Tension Research Articles

Mechanical Properties of High-Strength Concrete Reinforced with Hybrid Basalt–Polypropylene Fibers under Dynamic Compression and Split Tension

Mechanical Properties of High-Strength Concrete Reinforced with Hybrid Basalt–Polypropylene Fibers under Dynamic Compression and Split Tension

Experimental study on impact behaviour of normal strength mortar at cryogenic temperatures and after freeze-thaw cycles

Concrete structures employed for the storage of Liquefied Natural Gases (LNG) currently undergo temperature as low as −170 °C. These critical engineering structures may also experience dynamic loads such as impact or explosion during service life. Therefore, it is crucial to explore the mechanical response of concrete at intermediate to high strain rates together with low temperatures or cryogenic freeze-thaw (FT) cycles. This study presents experimental research into the combined effects of low temperatures and strain rate on normal strength mortar, providing a preliminary analysis of the dynamic performance of concrete at low and cryogenic temperatures. A Split Hopkinson Pressure Bar (SHPB) device was used to investigate the characteristics of dynamic compression (at strain rates of 40, 80, 120 and 160 s−1) and dynamic split tension (at strain rates of 20, 40, 60 and 80 s−1) of Normal Strength Mortar (NSM) at different low temperatures. In addition, the dynamic compression (at strain rates of 80, 130 and 180 s−1) after cryogenic FT cycles was also explored. The findings revealed that the failure pattern of NSM samples exposed to coupled low temperature or cryogenic FT cycles and high strain rate loading notably varied from that observed under room temperature condition. Both the dynamic compressive and split tensile strengths of NSM increased with the strain rates at all temperatures. At −160 °C, the dynamic compressive and splitting tensile strengths of NSM specimens were greater than those at room temperature (by 10.94 % and 28.29 %, respectively) and −70 °C (by 3.13 % and 4.12 %, respectively). Cryogenic freeze-thaw cycles evidently impacted the material static and dynamic performance. An empirical model was developed to predict the dynamic increase factors (DIFs) for both dynamic compression and splitting tensile strengths of NSM at low/cryogenic temperatures and after freeze-thaw cycles. Scanning electron microscopy (SEM) technique was performed to study and comprehend the microscopic processes and microstructural changes after FT cycles.

Rock-like material under large diameter SHPB dynamic splitting tension: meso-damage mechanical behavior and stress wave propagation model

The mechanical behavior of splitting tensile damage and the law of stress wave propagation of rock-like materials (RLM) are of great significance to further reveal the dynamic disaster mechanism of the deep rock mass. The meso-damage mechanical behavior and stress wave propagation characteristics of RLM disks under impact splitting were studied by using a large diameter split Hopkinson pressure bar (SHPB). In terms of dynamic damage, the splitting tensile stress-compression strain curves of RLM disks obviously showed three stages of mechanical behavior evolution: initial elastic-plastic deformation, pre-peak plastic damage, and post-peak brittle fracture failure. The macro-damage of RLM disks increased with the increase of strain rate. The meso-tensile fracture was the result of both the initial meso-damage and the impact splitting meso-damage. The dynamic splitting damage variable defined based on the damage fracture energy can accurately describe the damage evolution characteristics of impact splitting on RLM disks. In the aspect of stress wave propagation, the peak value of transmission stress showed an advanced effect with the increase of incident stress wave. In the early stage (0–50 μs), the transmission stress wave ratio (σT/σI) increased with the increase of strain rate, while in the later stage (82–200 μs), the transmission stress wave ratio (σT/σI) decreased with the increase of strain rate. The stress wave propagation law in the process of impact splitting on RLM disks was clearly revealed based on the stress wave propagation model established by the one-dimensional elastic stress wave theory. Finally, the dynamic mechanical mechanism of splitting damage and fracture of RLM disks under different strain rates was discussed deeply.

Physical and mechanical properties of deflection-hardening hybrid fibre-reinforced recycled aggregate concrete

Recycled aggregate concrete (RAC) has been gaining a large interest in recent years due to the depletion of natural aggregates and environmental protection requirements. To improve the ductility of RAC for structural applications and to avoid corrosion risks involved with utilising steel fibres, this study proposes a deflection-hardening hybrid fibre-reinforced recycled aggregate concrete (FRRAC) by combining newly developed macro-basalt fibre (BF, 0.67 % by volume) and recycled macro-polypropylene fibre (PF, 0.67 % by volume). Its fresh, static and dynamic mechanical properties were investigated and compared with the mix containing macro-BF only (1.34 % by volume). A Ø 100 mm split Hopkinson pressure bar (SHPB) system was used to determine the dynamic mechanical properties in compression and tension. The hybrid FRRAC retained up to 90 % of its average first peak load at 3.5 mm crack width and showed better cracking bridging performance under dynamic splitting tension than the specimens with the same volume of macro-BF. Empirical formulae for dynamic increase factors and energy absorption capacities against varying strain rates have also been proposed for the newly developed hybrid FRRAC.

Development of green engineered cementitious composites with acceptable dynamic split resistance utilising recycled polymer fibres

Using recycled tyre polymer fibres (RTPF) to replace part of polyvinyl alcohol fibres (PVAF) is a strategy to produce green and economical engineered cementitious composites (ECC). This paper systematically investigated the influence of RTPF dosage (0.25–1.0 vol%) on split tensile performance of ECC under different strain rates. Results indicated that replacing PVAF with RTPF up to 0.5 vol% could still show a pronounced strain-hardening behaviour for ECC, although accompanied by a decrease in static split tensile strength. The dynamic split tensile performance of all ECC mixes was strongly sensitive to strain rate and all hybrid fibre reinforced ECC presented a greater strain rate effect than the mono-PVAF reinforced ECC. Under dynamic split tension, the specimens with various RTPF dosages could maintain their structural integrity. This paper suggested that RTPF can be adopted to replace part of PVAF to produce a greener and more economical ECC with satisfactory static and dynamic mechanical performance but the highest substitution amount should be set to 0.5 vol%.

Effect of elevated temperatures on behaviour of recycled steel and polypropylene fibre reinforced ultra-high performance concrete under dynamic splitting tension

This paper investigates the dynamic splitting resistance of ultra-high performance concrete (UHPC) incorporating recycled steel (RS) and polyethene (PP) fibres at various temperatures (i.e., 20, 200, 400, 600, 800 °C) and strain rates (i.e., 2.3−7.2 s−1). A series of tests are performed to evaluate the compressive strength, elastic modulus, uniaxial tensile strength, dynamic splitting properties and microstructural characteristics of UHPC at elevated temperatures. Results reveal that the maximum compressive strength, elastic modulus and uniaxial tensile strength of UHPC appear at 400 °C due to the promoted hydration of unhydrated clinkers at elevated temperatures. When the temperature increases from 20 °C to 400 °C, the dynamic splitting strength and dissipated energy of UHPC under the strain rate range of 6.8–7.2 s−1 increases by 30.9 % and 124.2 %, respectively. However, an opposite trend occurs with the dynamic splitting properties of UHPC decreasing with elevated temperatures of 400–800 °C, and accordingly the dynamic increase factor at 800 °C is only 61.8−73.7 % of that at room temperature. The synergistic effect of RS and PP fibre on the impact resistance of UHPC at elevated temperatures can be explained by: (i) the enhanced pore connectivity by PP fibres prevents explosive spalling of UHPC at elevated temperatures; (ii) the bridging and pull-out effects of RS fibres improve residual dynamic properties of UHPC after high-temperature exposure.

Experimental and numerical studies on the mechanical behaviors of basic magnesium sulfate cement concrete under dynamic split-tension

Dynamic splitting-tensile tests were conducted on basic magnesium sulfate cement concrete (BMSCC) at three different water-cement ratios using a 75 mm diameter split Hopkinson pressure bar (SHPB). The failure process of BMSCC under dynamic splitting loading was simulated using the finite element software LS-DYNA and a random aggregate mesoscopic model. The results demonstrated the strain rate effect in BMSCC, where the dynamic splitting-tensile strength increased with higher strain rates. Furthermore, the strength grade of the material significantly influenced the growth rate of peak stress, with higher strength grades exhibiting faster rates. The dynamic increase factor (DIF), a parameter characterizing the dynamic behavior of brittle materials, exhibited a linear relationship with the logarithm of strain rate. The LS-DYNA software was employed to numerically simulate the dynamic splitting-tensile process at the meso-scale, yielding satisfactory results with relative errors of 12.7%, 6.3%, and 3.3% for the dynamic splitting-tensile strength at different water-cement ratios, respectively.

Experimental and mesoscopic investigation of self-compacting rubberized concrete under dynamic splitting tension

Self-compacting rubberized concrete (SCRC) has gained extensive investigations due to its good impact resistance and environmental friendliness, while the dynamic splitting tensile properties of SCRC are seldom studied. In this study, river sand in SCRC was replaced by three rubber volume fractions (5%, 10%, 15%). The experiments indicated that the static compressive strength, static tensile strength, elastic modulus and dynamic splitting tensile strength declined with the increase of rubber content. The dynamic splitting tensile strength, dynamic increase factor (DIF) and failure mode of SCRC were sensitive to strain rate. SCRC with a higher rubber volume had a greater DIF. The critical strain rate of different SCRC was obtained by piecewise fitting, which decreased with the enhancement of rubber content. Meanwhile, a three-dimensional mesoscopic model of SCRC was established. The rubber particles were generated by a random polyhedron algorithm and randomly thrown into the sample by the take and place algorithm. The numerical calculation suggested that the mesoscopic model could exhibit the fracture process of SCRC under high strain rates. The propagation of cracks bypassed the rubber particles and produced a mass of branch cracks under high strain rates, dissipating a large amount of energy and elevating the DIF, which is consistent with the macroscopic failure pattern. In addition, the effect of strain rate and rubber volume on DIF was discussed combined with the mesoscopic model.

Investigation on the dynamic tensile behaviour of rubberized mortar using the Brazilian disc method

The use of tire rubber particles as a partial substitute for fine aggregate in cement-based materials has been proven to potentially have both environmental and economic benefits. Although the studies on the physical and mechanical properties of rubberized mortar are abundant, those related to the dynamic tensile behaviour are scarce. In this study, rubber powders with three sizes (0.125 mm, 0.180 mm, and 0.425 mm) are used to fabricate the Brazilian disc rubberized mortar specimen, with rubber volume percentages up to 40%. A 50 mm-diameter split Hopkinson pressure bar (SHPB) apparatus is then adopted to conduct the dynamic split tension tests, and the static tensile tests are also conducted for comparison purposes. Experimental results show that the dynamic split tensile strength of the rubberized mortar linearly increases with increasing the loading rate, whereas decreases with the increase of the rubber volume percentage. The mortars with smaller rubber powder at the same percentage exhibit more significant dynamic strength loss. As compared with the static tests, the reduction ratio of the dynamic split tensile strength of mortar with different rubber content is much smaller. The dynamic increase factors of the rubberized mortar are more sensitive to the loading rate, and positively correlated to both the rubber volume and the powder size. Besides, the occurring time of the primary crack initiation gradually decreases with increasing the loading rate and rubber size, whereas increases with increasing the rubber volume percentage. In addition, the dissipated energy density of the rubberized mortar is positively correlated with the rubber volume percentage, and the addition of the smaller rubber powder can enhance the dynamic energy absorption capacity.

Test of Dynamic Mechanical Properties of Ambient-Cured Geopolymer Concrete Using Split Hopkinson Pressure Bar

The application of geopolymer concrete (GPC) in construction could reduce a large amount of carbon dioxide (CO2) emission, which is greatly beneficial to environmental sustainability. Structures made of GPC might be subjected to extreme loading such as impact and blast loads. Therefore, a good understanding of the dynamic properties of GPC is essential to provide reliable predictions of performance of GPC structures subjected to dynamic loading. This study presents an experimental investigation on the dynamic compressive and splitting tensile properties of ambient-cured GPC using split Hopkinson pressure bar (SHPB), with the strain rate up to 161.0 s−1 for dynamic compression and 10.3 s−1 for dynamic splitting tension. The failure mode and damage progress of GPC specimens, energy absorption, and dynamic increase factor (DIF) were studied. Test results showed that ambient-cured GPC exhibited strain rate sensitivity. The compressive and splitting tensile DIFs increased with the strain rate and the ambient-cured GPC with lower quasi-static compressive strength exhibited higher DIFs under both dynamic compression and splitting tension. Empirical formulas were proposed to predict the DIF of ambient-cured GPC. Furthermore, the specific energy absorption of ambient-cured GPC under dynamic compression increased approximately linearly with the strain rate.

Dynamic properties of granite rock employed as coarse aggregate in high-strength concrete

The dynamic properties of a granite rock employed in crushed form as coarse aggregate in high-strength concrete, were experimentally characterised, and the average values obtained were assumed to be representative of the properties of the coarse aggregate. Cylindrical specimens were core-drilled from the granite rock, then cut into various lengths for different tests, i.e. static and dynamic uniaxial compression, as well as static and dynamic splitting tension (Brazilian tests). From the data obtained, the effects of strain rate on the mechanical properties (e.g. stress-strain relationship, tensile and compressive strengths) were analysed. Significant rate dependence was observed for both tensile and compressive responses, and this was quantified via a dynamic increase factor (DIF, the ratio between the dynamic and static strength). For compression, the DIF follows the CEB-FIP 2010 equation frequently used to describe the rate sensitivity of normal-strength concrete. The tensile response shows a stronger rate dependence than the compressive response, and its DIF deviates from predictions based on the CEB-FIP equation, which underestimates the tensile DIF, and defines a much higher strain rate at which transition from a gradual to a rapid increase in the DIF occurs. An empirical DIF formula, derived from fitting of experimental data, is proposed to describe the tensile rate sensitivity. Apart from experimental characterisation, efforts were also directed at identifying a constitutive model to describe the dynamic behaviour of the granite coarse aggregate, and the Johnson-Holmquist 2 (JH-2) model, commonly used to capture the impact response of brittle materials (e.g. rock, ceramic) was chosen. The dynamic tensile and compressive properties obtained from experiments, were employed to determine the material parameters in the JH-2 model. Finite element modelling of the dynamic compression and splitting tension tests was performed, using the JH-2 model and the material constants derived, to describe the behaviour of the granite specimen. The simulation results correlate well with experimental measurements.

Behaviour of recycled tyre polymer fibre reinforced concrete under dynamic splitting tension

Recycled tyre polymer (RTP) fibre has recently been gaining ever-increasing attention from the scientific community as a promising substitute to synthetic fibres for cementitious composites to improve sustainability. This paper, for the first time, investigates the behaviour of RTP fibre reinforced concrete (FRC) under dynamic splitting tension, focusing on the effects of fibre content (0.1, 0.2, 0.4 and 0.8 vol%) and strain rate (0.88–3.54 s−1) and the feasibility of replacing polypropylene (PP) fibre with RTP fibre for FRC. Results indicate that the inclusion of RTP fibres is favourable in enhancing the splitting tensile properties of concrete under various strain rates (10−1 to 101 s−1), where the dynamic splitting tensile strength and dissipated energy of concrete mixture containing 0.2 vol% RTP fibre are improved by 5.5%–14.2% and 24.9%–36.7% respectively compared to the plain mixture as a result of fibre bridging effect. Fibre pull-out process considerably contributes to the enhancement of energy dissipation capacity. The splitting tensile properties of all mixtures are sensitive to strain rate, where the developed empirical equations well describing the relationship between dynamic increase factor (DIF) and strain rate provide insight into this rate sensitivity. A comparison between RTP-FRC and PP-FRC confirms that RTP fibre can be used as a sustainable and cost-effective alternative to PP fibre for cementitious materials considering engineering properties and potential economic benefit of the composites.

Experimental study on dynamic mechanics and energy evolution of rubber concrete under cyclic impact loading and dynamic splitting tension

To comprehensively explore the mechanical damage and energy evolution of rubber concrete under different dynamic loading modes, the dynamic mechanical experiments of rubber concrete under four loading modes were carried out by using the split Hopkinson pressure bar (SHPB) system. The main tests were the single impact compression, cyclic impact compression with constant load, cyclic impact compression with variable load, and dynamic splitting tension based on the splitting principle of Brazilian disc (BD). The failure modes, stress waves, stress–strain curves, strength, deformation, and energy evolution characteristics of rubber concrete under different test methods were analysed. Under impact compression, the macroscopic cracks of the specimens first appeared on the local weak surface of the edge and propagated with the increase of impact pressure and impact times. Under dynamic splitting, the fracture of specimens began from the “initial compression damage zone (ICDZ)”, and extended to the center of the specimen along the force direction due to the action of stress concentration. The change of the wave impedance of the specimen determined the variation characteristics of reflected and transmitted waves, which reflected the cumulative damage evolution of the specimen in the process of cyclic impact. When the cyclic impact was carried out many times under the critical impact load, the strength and deformation showed the phenomenon of “strengthening at first and then weakening” and “decreasing at first and then increasing” respectively. The evolution curves of reflected energy ratio and absorbed energy ratio were complex and opposite. The evolution curves of specific energy absorption and absorbed energy ratio can be divided into three stages, which can effectively reflect the damage change of the specimens under different impact loads.

Experimental and numerical study on tensile strength and failure pattern of high performance steel fiber reinforced concrete under dynamic splitting tension

High performance steel fiber reinforced concrete (HPSFRC) is widely used in structural engineering due to its excellent performance. It is necessary to study its dynamic mechanical properties for making full use of the material, reducing the engineering cost and optimizing the structural design. Firstly, the dynamic splitting tensile tests of HPSFRC with different fiber contents (0%, 1%, 2%) were conducted by using a 74 mm-diameter splitting Hopkinson pressure bar (SHPB) system under different strain rates (70/s ~ 190/s). Then, according to failure pattern of the specimen and test data, the enhancement mechanism of strain rate and steel fiber on tensile stress of HPSFRC is analyzed, relationship between strain rate and dynamic splitting tensile strength increase factor (DIFft) is also discussed. Furthermore, the enhancement mechanism of steel fiber and strain rate on HPSFRC is verified based on energy conversion during failure process. Finally, the dynamic failure process of HPSFRC is simulated by LS-DYNA, and failure patterns of HPSFRC with different fiber contents are compared from the perspective of crack development. The results indicate that the energy dissipation ratio increases with the ascending steel fiber content and decreases with the ascending strain rate. The steel fiber can increase tensile stress of HPC, and the enhancement degree under quasi-static loading is better than that under dynamic loading. In addition, steel fiber reinforced factor and DIFft have strain-rate effect. Steel fiber reinforced factor decreases as strain rate increases. On the contrary, DIFft increases as strain rate increases, and the increasing trend gradually slows down. These results can provide a basis for improving the dynamic tensile properties of HPSFRC.

Mechanical properties and behaviour of high-strength plain and hybrid-fiber reinforced geopolymer composites under dynamic splitting tension

Geopolymer materials have been of particular interest to the construction industry due to their environmental benefits. However, their behaviour has rarely been investigated under dynamic loadings, although it is of fundamental concern to assess their vulnerability against higher loading rates. In this study, the dynamic tensile properties of a newly fabricated high-strength ambient cured geopolymer material and fiber reinforced geopolymer composites (FRGC) are presented. Since geopolymers are intrinsically brittle, novel equal-part blend of hooked-end and spiral-shaped steel fibers at two different fiber volume fractions and hybrid steel-polyethylene combination were used to reinforce the geopolymer matrix. The quasi-static splitting tensile tests were performed using a 300 KN displacement controlled Shimadzu test machine, while a modified Ø100-mm split Hopkinson pressure bar (SHPB) apparatus was used to conduct the dynamic splitting-tensile tests. A high-speed camera was used to capture the fracture development processes and crack-opening of different types of FRGC. The test results show that under quasi-static splitting tension, the unreinforced geopolymer exhibited minimal tensile strain capacity. With the addition of steel fibers and hybrid steel-polyethylene fiber reinforcement, the energy absorption capability of FRGC samples was significantly improved. The dynamic tests reveal the strong strain rate dependency and prominent tensile strength enhancements for all composites, although unreinforced geopolymer samples were more sensitive to the strain rate effect within the considered test range. A comparison between the test data and modified CEB guidelines reflect the non-suitability of code formulae to establish the dynamic increase factor (DIFft) relation for geopolymers. Based on the test data, empirical DIFft relationships are proposed for unreinforced and different types of FRGC samples. It is also indicated by image analyses that the excellent bonding of spiral steel fibers with the geopolymer matrix is befittingly complemented by polyethylene fibers to maintain the material integrity.

Dynamic Tensile Experimental Techniques for Geomaterials: A Comprehensive Review

This review article is dedicated to the Dynamic Behavior of Materials Technical Division for celebrating the 75th anniversary of the Society for Experimental Mechanics (SEM). Understanding dynamic behavior of geomaterials is critical for analyzing and solving engineering problems of various applications related to underground explosions, seismic, airblast, and penetration events. Determining the dynamic tensile response of geomaterials has been a great challenge in experiments due to the nature of relatively low tensile strength and high brittleness. Various experimental approaches have been made in the past century, especially in the most recent half century, to understand the dynamic behavior of geomaterials in tension. In this review paper, we summarized the dynamic tensile experimental techniques for geomaterials that have been developed. The major dynamic tensile experimental techniques include dynamic direct tension, dynamic split tension, and spall tension. All three of the experimental techniques are based on Hopkinson or split Hopkinson (also known as Kolsky) bar techniques and principles. Uniqueness and limitations for each experimental technique are also discussed.

Mesoscale modelling of concrete reinforced with spiral steel fibres under dynamic splitting tension

The addition of discrete steel fibres into concrete has been widely recognised as an effective measure to enhance the ductility, post-cracking resistance and energy absorption of the matrix subjected to impact loads. Despite useful information from experimental studies that investigate the macro-scale performance of steel fibre–reinforced concrete under dynamically applied loadings, results from a series of tests or from tests by different researchers are often found to be scattered. Besides variations in testing conditions, random variations of size, location and orientation of aggregates and fibres in steel fibre–reinforced concrete are deemed the fundamental reason of the scattering test data. High-fidelity modelling of concrete and steel fibre–reinforced concrete in mesoscale has been widely adopted to understand the influence of each component in the composite material. Numerical studies have been published to discuss the behaviour of steel fibre–reinforced concrete under dynamic splitting tension. Different shapes, for example, circles, ovals and polygons, of coarse aggregates were considered in different studies, and different conclusions were drawn. This study investigates the influence of the shape of aggregates on numerical prediction in mesoscale modelling of steel fibre–reinforced concrete materials with spiral fibres under dynamic splitting tension in terms of the strain distribution, cracking pattern and strength. The numerical model is validated by experimental results. It is found that the shape of aggregates in mesoscale modelling of splitting tensile tests has negligible influence. Furthermore, steel fibre–reinforced concrete specimens with different volume fractions of spiral fibres from 0.5% to 3.0% under various loading rates are simulated. Results from parametric simulations indicate the optimal dosage of spiral fibres in steel fibre–reinforced concrete mix with respect to the construction cost and mechanical property control.

Mechanical properties and behaviour of concrete reinforced with spiral-shaped steel fibres under dynamic splitting tension

Concrete exhibits excellent resistance to compressive forces, but is brittle and weak in tension. Various types of fibres have been investigated by many researchers to improve the ductility and energy absorption capability of concrete materials and structures under static and blast and impact loadings. Spiral-shaped steel fibres were recently proposed as reinforcement in a concrete matrix and it was found that spiral fibre reinforcement can significantly improve the ductility, crack control ability and energy absorption capacity of concrete material under static and impact compressive loads. This paper presents an experimental study of the static and dynamic properties of steel fibre reinforced concrete (SFRC) materials under splitting tension. SFRC materials mixed with spiral-shaped steel fibres of different volume fractions were prepared and tested. A high-speed camera was used to capture the deformation, failure and crack opening process of the tested specimens. The contribution of spiral fibres to the mechanical properties and behaviour of concrete at high strain rate under splitting tension was investigated. Analyses of the test results revealed the effectiveness of spiral fibres in improving the performance of SFRC (e.g. crack control, energy absorption capability and more pronounced rate sensitivity under dynamic splitting loading). Moreover, crack opening and closing (pull-back by spiral fibres) processes were observed, demonstrating the excellent bonding and outstanding performance of spiral steel fibres in maintaining the integrity of the concrete material, thus resulting in significant improvements in impact resistance and energy dissipation.

An Experimental Study of the Dynamic Split Tension Properties of Reinforced Concrete

Dynamic split tensile tests of reinforced concrete were carried out using the split Hopkinson pressure bar experimental technique to determine the failure modes of reinforced concrete at different strain rates, and the effect of reinforcement ratio and reinforcement layouts on the dynamic performance. The specimens with nine reinforcement ratios were used in the tests. Experimental results show that the tensile strength of reinforced concrete exhibits a critical strain rate, beyond which a larger increase in dynamic strength of specimens occur. The dynamic split tension strength of reinforced concrete is demonstrated to be greater than the plain concrete with the same strength grade over the range of tested strain rates. The results also indicate that the dynamic split tension strength of specimens enhances with the increase in the reinforcement ratio. These findings are instrumental to guide the structural design of reinforced concrete in engineering applications.

Dynamic Properties of Concrete at Moderately Elevated Temperatures

Reinforced concrete is widely used to not only provide structural support but also to mitigate the effects of radiation, malevolent attacks, and dynamic accidents. Dynamic tests were performed on 102 x 203 mm (4 x 8 in.) normal weight concrete (NWC) and fiber-reinforced concrete (FRC) cylinders using a drop hammer. Dynamic splitting tension and dynamic compression tests were performed at room temperature and at 204°C (400°F). The dynamic increase factor (DIF), which is the ratio of dynamic to quasi-static strength, and the strain rate were compared to existing models. The DIF for tension and compression increased with strain rate. For compression, a DIF up to 3.2 was recorded for strain rates up to 12 s⁻¹. For tension, a DIF up to 4.1 was recorded for strain rates up to 1.8 s⁻¹. Heated NWC and FRC specimens had lower DIFs compared to room-temperature specimens for dynamic compression and tension. The experimental DIFs followed closely the Modified Comite Euro-International du Beton (CEB) model for tension.