Editorial

3 pages, 173 KiB

Open AccessEditorial

Mechanical Research on Reinforced Concrete Materials

by Wei Wang

Materials 2023, 16(21), 6892; https://doi.org/10.3390/ma16216892 - 27 Oct 2023

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Reinforced concrete (RC) is a commonly used construction material in civilian and military buildings due to its superior material characteristics compared to steel and timber (e [...] Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

Research

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18 pages, 7139 KiB

Open AccessArticle

Study on the Dynamic Mechanical Properties of Ultrahigh-Performance Concrete under Triaxial Constraints

by Wei Zhang, Jize Mao, Xiao Yu, Bukui Zhou and Limei Wang

Materials 2023, 16(19), 6591; https://doi.org/10.3390/ma16196591 - 07 Oct 2023

Cited by 1 | Viewed by 760

Abstract

To confirm the effect of confining pressure on the dynamic mechanical behavior of ultrahigh-performance concrete (UHPC), this study used a true triaxial split Hopkinson pressure bar test system to perform dynamic compression tests on UHPC under triaxial constraints. The confining pressure range considered [...] Read more.

To confirm the effect of confining pressure on the dynamic mechanical behavior of ultrahigh-performance concrete (UHPC), this study used a true triaxial split Hopkinson pressure bar test system to perform dynamic compression tests on UHPC under triaxial constraints. The confining pressure range considered was 5~10 MPa, the strain rate range was 35~80 s⁻¹, and the steel fiber contents were 0.5%, 1% and 2%. The three-dimensional dynamic engineering stress-strain relationship and equivalent stress-strain relationship of UHPC under different confining pressures and different strain rates were obtained and analyzed in detail. The results show that under the confinement condition, the dynamic peak axial stress–strain and dynamic peak lateral stress–strain of UHPC have strong sensitivity to the strain rate. In addition, the dynamic peak lateral stress–strain is more sensitive to the confining pressure than the dynamic axial stress. An empirical strength enhancement factor (DIFc) that considers the strain rate effect and confining pressure was derived, and the impact of the coupling between the enhancement caused by the confining pressure and the strain rate effect on the dynamic strength of the UHPC under triaxial confinement was discussed. A dynamic strength failure criterion for UHPC under triaxial constraint conditions was established. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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21 pages, 11992 KiB

Open AccessArticle

Experimental and Numerical Study of Non-Explosive Simulated Blast Loading on Reinforced Concrete Slabs

by Zhixiang Xiong, Wei Wang, Guocai Yu, Jian Ma, Weiming Zhang and Linzhi Wu

Materials 2023, 16(12), 4410; https://doi.org/10.3390/ma16124410 - 15 Jun 2023

Cited by 3 | Viewed by 1085

Abstract

This study presents a non-explosive method for simulating blast loading on reinforced concrete (RC) slabs. The method involves using a newly developed blast simulator to apply a speedy impact load on the slab, which generates a pressure wave similar to that of an [...] Read more.

This study presents a non-explosive method for simulating blast loading on reinforced concrete (RC) slabs. The method involves using a newly developed blast simulator to apply a speedy impact load on the slab, which generates a pressure wave similar to that of an actual blast. Both experimental and numerical simulations were carried out to evaluate the effectiveness of the method. The experimental results showed that the non-explosive method can produce a pressure wave with a peak pressure and duration analogous to those of an actual blast. The numerical simulations also showed good agreement with the experimental results. Additionally, parameter studies were conducted to evaluate the effects of the rubber shape, the impact velocity, the bottom thickness, and the upper thickness on the impact loading. The results indicate that pyramidal rubber is more suitable as an impact cushion for simulating blast loading than planar rubber. The impact velocity has the widest range of regulation for peak pressure and impulse. As the velocity increases from 12.76 to 23.41 m/s, the corresponding range of values for peak pressure is 6.457 to 17.108 MPa, and for impulse, it is 8.573 to 14.151 MPa∙ms. The variation in the upper thickness of the pyramidal rubber has a more positive effect on the impact load than the bottom thickness. With the upper thickness increasing from 30 mm to 130 mm, the peak pressure decreased by 59.01%, and the impulse increased by 16.64%. Meanwhile, when the bottom part’s thickness increased from 30 mm to 130 mm, the peak pressure decreased by 44.59%, and the impulse increased by 11.01%. The proposed method provides a safe and cost-effective alternative to traditional explosive methods for simulating blast loading on RC slabs. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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16 pages, 17557 KiB

Open AccessArticle

The Strain Rate Effects of Coral Sand at Different Relative Densities and Moisture Contents

by Kai Dong, Kun Jiang and Wenjun Ruan

Materials 2023, 16(12), 4217; https://doi.org/10.3390/ma16124217 - 07 Jun 2023

Cited by 1 | Viewed by 727

Abstract

A 37-mm-diameter split Hopkinson pressure bar (SHPB) apparatus was used for impact loading tests to determine the effects of the relative density and moisture content on the dynamic properties of coral sand. The stress–strain curves in the uniaxial strain compression state were obtained [...] Read more.

A 37-mm-diameter split Hopkinson pressure bar (SHPB) apparatus was used for impact loading tests to determine the effects of the relative density and moisture content on the dynamic properties of coral sand. The stress–strain curves in the uniaxial strain compression state were obtained for different relative densities and moisture contents under strain rates between 460 s⁻¹ and 900 s⁻¹. The results indicated that with an increase in the relative density, the strain rate becomes more insensitive to the stiffness of the coral sand. This was attributed to the variable breakage-energy efficiency at different compactness levels. Water affected the initial stiffening response of the coral sand, and the softening was correlated with the strain rate. Strength softening due to water lubrication was more significant at higher strain rates due to the higher frictional dissipation. The volumetric compressive response of the coral sand was investigated by determining the yielding characteristics. The form of the constitutive model has to be changed to the exponential form, and different stress–strain responses should be considered. We discuss the effects of the relative density and water content on the dynamic mechanical properties of coral sand and clarify the correlation with the strain rate. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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16 pages, 3739 KiB

Open AccessArticle

A Research Investigation into the Impact of Reinforcement Distribution and Blast Distance on the Blast Resilience of Reinforced Concrete Slabs

by Yangyong Wu, Jianhui Wang, Fei Liu, Chaomin Mu, Ming Xia and Shaokang Yang

Materials 2023, 16(11), 4068; https://doi.org/10.3390/ma16114068 - 30 May 2023

Cited by 1 | Viewed by 1178

Abstract

Reinforcement is one of the important factors affecting the anti-blast performance of reinforced concrete (RC) slabs. In order to study the impact of different reinforcement distribution and different blast distances on the anti-blast performance of RC slabs, 16 model tests were carried out [...] Read more.

Reinforcement is one of the important factors affecting the anti-blast performance of reinforced concrete (RC) slabs. In order to study the impact of different reinforcement distribution and different blast distances on the anti-blast performance of RC slabs, 16 model tests were carried out for RC slab members with the same reinforcement ratio but different reinforcement distribution and the same proportional blast distance but different blast distances. By comparing the failure patterns of RC slabs and the sensor test data, the impact of reinforcement distribution and blast distance on the dynamic response of RC slabs was analyzed. The results show that, under contact explosion and non-contact explosion, the damage degree of single-layer reinforced slabs is more serious than that of double-layer reinforced slabs. When the scale distance is the same, with the increase of distance, the damage degree of single-layer reinforced slabs and double-layer reinforced slabs increases first and then decreases, and the peak displacement, rebound displacement and residual deformation near the center of the bottom of RC slabs gradually increase. When the blast distance is small, the peak displacement of single-layer reinforced slabs is smaller than that of double-layer reinforced slabs. When the blast distance is large, the peak displacement of double-layer reinforced slabs is smaller than that of single-layer reinforced slabs. No matter how large the blast distance, the rebound peak displacement of the double-layer reinforced slabs is smaller, and the residual displacement is larger. The research in this paper provides a reference for the anti-explosion design, construction and protection of RC slabs. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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17 pages, 4564 KiB

Open AccessArticle

Analytical Study of SH Wave Scattering by a Circular Pipeline in an Inhomogeneous Concrete with Density Variation

by Zailin Yang, Chenxi Sun, Guanxixi Jiang, Yunqiu Song, Xinzhu Li and Yong Yang

Materials 2023, 16(10), 3693; https://doi.org/10.3390/ma16103693 - 12 May 2023

Cited by 1 | Viewed by 899

Abstract

In this paper, the shear horizontal (SH) wave scattering by a circular pipeline in an inhomogeneous concrete with density variation is studied. A model of inhomogeneous concrete with density variation in the form of a polynomial-exponential coupling function is established. By using the [...] Read more.

In this paper, the shear horizontal (SH) wave scattering by a circular pipeline in an inhomogeneous concrete with density variation is studied. A model of inhomogeneous concrete with density variation in the form of a polynomial-exponential coupling function is established. By using the complex function method and conformal transformation, the incident and scattering wave field of SH wave in concrete are obtained, and the analytic expression of dynamic stress concentration factor (DSCF) around the circular pipeline is given. The results show that the inhomogeneous density parameters, the wave number of the incident wave and the angle of the incident wave in concrete are important factors affecting the distribution of dynamic stress around the circular pipe in concrete with inhomogeneous density. The research results can provide a theoretical reference and a basis for analyzing the influence of circular pipeline on elastic wave propagation in an inhomogeneous concrete with density variation. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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19 pages, 7755 KiB

Open AccessArticle

Study on Mass Erosion and Surface Temperature during High-Speed Penetration of Concrete by Projectile Considering Heat Conduction and Thermal Softening

by Kai Dong, Kun Jiang, Chunlei Jiang, Hao Wang and Ling Tao

Materials 2023, 16(9), 3604; https://doi.org/10.3390/ma16093604 - 08 May 2023

Cited by 2 | Viewed by 993

Abstract

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass [...] Read more.

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass loss. In this paper, theoretical models are established to calculate the mass erosion and heat conduction of projectile noses, including models of cutting, melting, the heat conduction of flash temperature, and the conversion of plastic work into heat. The friction cutting model is modified considering the heat softening of metal, and a model of non-adiabatic processes for the nose was established based on the heat conduction theory to calculate the surface temperature. The coupling numerical calculation of the erosion and heat conduction of the projectile nose shows that melting erosion is the main factor of mass loss at high-speed penetration, and the mass erosion ratio of melting and cutting is related to the initial velocity. Critical velocity without melting erosion and a constant ratio of melting and cutting erosion exists, and the critical velocities are closely related to the melting temperature. In the process of penetration, the thickness of the heat affected zone (HAZ) gradually increases, and the entire heat conduction zone (EHZ) is about 5~6 times the thickness of the HAZ. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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19 pages, 6839 KiB

Open AccessArticle

Corrosion-Effected Bond Behavior between PVA-Fiber-Reinforced Concrete and Steel Rebar under Chloride Environment

by Xuhui Zhang, Xun Wu and Yang Wang

Materials 2023, 16(7), 2666; https://doi.org/10.3390/ma16072666 - 27 Mar 2023

Cited by 7 | Viewed by 1299

Abstract

Corrosion-effected bond behavior between polyvinyl-alcohol-fiber-reinforced concrete and steel rebar under a chloride environment is the experimental subject studied in the present work. Twenty-four pull-out specimens are designed and subjected firstly to an accelerated corrosion test. The effects of polyvinyl alcohol fibers on the [...] Read more.

Corrosion-effected bond behavior between polyvinyl-alcohol-fiber-reinforced concrete and steel rebar under a chloride environment is the experimental subject studied in the present work. Twenty-four pull-out specimens are designed and subjected firstly to an accelerated corrosion test. The effects of polyvinyl alcohol fibers on the cracking behavior, chloride penetration of concrete members and the corrosion loss of steel rebars during the corrosion test are discussed. After this, these corroded specimens are subjected to a pull-out test. The failure mode, the bond-slip curves and the typical bond-stress values are measured during the test. The effects of polyvinyl alcohol fibers and corrosion loss on bond behavior between polyvinyl-alcohol-fiber-reinforced concrete and steel rebar are clarified. Results show that the polyvinyl-alcohol-fiber-reinforced concrete exhibits worse resistance to corrosion damage than plain concrete. The cracking width, chloride penetration depth in concrete and the corrosion loss of steel rebar are more serious for the specimens with more polyvinyl alcohol fibers. The polyvinyl alcohol fibers also negatively affect bonding in ascending branches for both the specimens, but improve the bonding in descending branches after peak stress in the case of splitting. In the present test, the bond strength of corrosive specimens is increased slightly and then decreases gradually with the deepening of corrosion loss. The failures of specimens change from pull-out to splitting-pull-out as the corrosion time exceeds 30 days. Compared with uncorroded specimens, the maximum degradation of bond strength is about 50.1% when the corrosion is increased from 0% to 15%. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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21 pages, 12345 KiB

Open AccessArticle

Mechanical Behaviour Evaluation of Full Iron Tailings Concrete Columns under Large Eccentric Short-Term Loading

by Xinxin Ma, Jianheng Sun, Fengshuang Zhang, Jing Yuan, Mingjing Yang, Zhiliang Meng, Yongbing Bai and Yunpeng Liu

Materials 2023, 16(6), 2466; https://doi.org/10.3390/ma16062466 - 20 Mar 2023

Cited by 2 | Viewed by 1137

Abstract

In this study, full iron tailings concrete (FITC) was created using iron tailings from a tailings pond in Qian’an, China. Iron tailings account for 86.8% of the total mass of solid raw materials in the FITC. To enable large-scale use of FITC, a [...] Read more.

In this study, full iron tailings concrete (FITC) was created using iron tailings from a tailings pond in Qian’an, China. Iron tailings account for 86.8% of the total mass of solid raw materials in the FITC. To enable large-scale use of FITC, a comprehensive investigation of the structural behaviour of full-iron tailing-reinforced concrete (FITRC) specimens is warranted. Therefore, eight rectangular reinforced concrete (RC) columns with conventional reinforced concrete (CRC) as a control were tested to investigate the effects of section dimensions, initial eccentricities, and concrete strengths, on the structural behaviour of FITRC columns under large eccentric short-term loading. The experimental and analytical results indicated that the sectional strain of the FITRC columns satisfied the plane-section assumption under short-term loading, and the lateral deflection curve agreed well with the half-sinusoidal curve. In addition, the FITRC columns exhibited a slightly lower cracking load and lower ultimate load capacity than the CRC columns, and the crack widths were larger than those of the CRC columns. The reduction in the load capacity observed in the FITRC was within the permissible range stated in the design code, thereby satisfying the code requirements. The deformation coefficients of the FITRC and CRC columns were identical, and the cracking and ultimate loads calculated according to the current code and theories were in good agreement with the measured results. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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17 pages, 6715 KiB

Open AccessArticle

Effect of Superfine Cement Modification on Properties of Coral Aggregate Concrete

by Fei Wang, Jianmin Hua, Xuanyi Xue, Neng Wang, Feidong Yan and Dou Feng

Materials 2023, 16(3), 1103; https://doi.org/10.3390/ma16031103 - 27 Jan 2023

Cited by 11 | Viewed by 1585

Abstract

In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. [...] Read more.

In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. Hence, superfine cement is used innovatively in this study to modify coral aggregates; additionally, the effects of the water–cement ratio and curing time on the water absorption and strength of modified coral aggregates are investigated. Modified coral aggregate concrete is prepared, and the effect of using modified superfine cement on its workability and strength is investigated. Experimental results show that when the water-cement ratio exceeds 1.25, the slurry does not form a shell on the surface of the coral aggregates and the water absorption of the coral aggregates increases significantly. The strength of the modified coral aggregates cured for a short duration is slightly lower than that of unmodified coral aggregates, whereas that cured for 28 days is approximately 20% higher than that of unmodified coral aggregates. Using superfine cement to modify coral aggregate concrete can improve its workability, but not its compressive properties. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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11 pages, 13699 KiB

Open AccessArticle

Determining Dynamic Mechanical Properties for Elastic Concrete Material Based on the Inversion of Spherical Wave

by Huawei Lai, Zhanjiang Wang, Liming Yang, Lili Wang and Fenghua Zhou

Materials 2022, 15(22), 8181; https://doi.org/10.3390/ma15228181 - 17 Nov 2022

Cited by 1 | Viewed by 1020

Abstract

The paper presents a new method to study the dynamic mechanical properties of concrete under low pressure and a high strain rate via the inversion of spherical wave propagation. The dynamic parameters of rate-dependent constitutive relation of elastic concrete are determined by measured [...] Read more.

The paper presents a new method to study the dynamic mechanical properties of concrete under low pressure and a high strain rate via the inversion of spherical wave propagation. The dynamic parameters of rate-dependent constitutive relation of elastic concrete are determined by measured velocity histories of spherical waves. Firstly, the particle velocity time history profiles in the low stress elastic region at the radii of 100.6 mm, 120.6 mm, 140.6 mm, 160 mm, and 180.6 mm are measured in the semi-infinite space of concrete by using the mini-explosive ball and electromagnetic velocity measurement technology. Then, based on the universal spherical wave conservation equation and the fact that the accommodation relationship in state equation satisfies linear elastic law, the inverse problem analysis of spherical waves in concrete (called “NV + T0/SW”) is proposed, which can obtain the dynamic numerical constitutive behavior of concrete in three-dimensional stress by measuring the velocity histories. The numerical constitutive relation is expressed in the form of distortion, and it is found that the distortion law has an obvious rate effect. Finally, the rate-dependent dynamic parameters in concrete are determined by the standard linear solid model. The results show that the strain rate effect of concrete cannot be ignored with the strain rate range of 10² 1/s. This study can provide a feasible method to determine the dynamic parameters of rate-dependent constitutive relation of concretes. This method has good applicability, especially in the study of the dynamic behavior of multicomponent composite materials with large-size particle filler. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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15 pages, 6158 KiB

Open AccessArticle

Blast Resistance of Reinforced Concrete Slabs Based on Residual Load-Bearing Capacity

by Lijun Wang, Shuai Cheng, Zhen Liao, Wenjun Yin, Kai Liu, Long Ma, Tao Wang and Dezhi Zhang

Materials 2022, 15(18), 6449; https://doi.org/10.3390/ma15186449 - 16 Sep 2022

Cited by 7 | Viewed by 1718

Abstract

In this paper, the blast-loading experiment and numerical simulation are carried out for RC slabs with two typical reinforcement ratios. The time history of reflected shockwave pressures and displacement responses at different positions on the impact surface of the specimens are obtained, and [...] Read more.

In this paper, the blast-loading experiment and numerical simulation are carried out for RC slabs with two typical reinforcement ratios. The time history of reflected shockwave pressures and displacement responses at different positions on the impact surface of the specimens are obtained, and the influence of the reinforcement ratio on the dynamic responses and failure modes of the RC slabs is analyzed. Based on the experimental data, the simulation model of the RC slab is verified, and the results indicate good agreement between the two methods. On this basis, the residual load-bearing capacity of the damaged RC slabs is analyzed. The results show that the load distribution on the impact surface of the slab is extremely uneven under close-in blast loading. The resistance curve shape of the RC slabs varies markedly before and after blast loading, and its load bearing capacity and bending stiffness deteriorate irreversibly. Increasing the reinforcement ratio can impede crack extension, reduce the slab’s residual displacement, and, at the same time, reduce the decrease of the damaged slab’s load-bearing capacity. The findings of this study will provide insights into the anti-explosion design and damage evaluation of RC slabs. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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20 pages, 21476 KiB

Open AccessArticle

Dynamic Compressive Mechanical Properties of UR50 Ultra-Early-Strength Cement-Based Concrete Material under High Strain Rate on SHPB Test

by Wei Wang, Zhonghao Zhang, Qing Huo, Xiaodong Song, Jianchao Yang, Xiaofeng Wang, Jianhui Wang and Xing Wang

Materials 2022, 15(17), 6154; https://doi.org/10.3390/ma15176154 - 05 Sep 2022

Cited by 9 | Viewed by 1485

Abstract

UR50 ultra-early-strength cement-based self-compacting high-strength material is a special cement-based material. Compared with traditional high-strength concrete, its ultra-high strength, ultra-high toughness, ultra-impact resistance, and ultra-high durability have received great attention in the field of protection engineering, but the dynamic mechanical properties of impact [...] Read more.

UR50 ultra-early-strength cement-based self-compacting high-strength material is a special cement-based material. Compared with traditional high-strength concrete, its ultra-high strength, ultra-high toughness, ultra-impact resistance, and ultra-high durability have received great attention in the field of protection engineering, but the dynamic mechanical properties of impact compression at high strain rates are not well known, and the dynamic compressive properties of materials are the basis for related numerical simulation studies. In order to study its dynamic compressive mechanical properties, three sets of specimens with a size of Φ100 × 50 mm were designed and produced, and a large-diameter split Hopkinson pressure bar (SHPB) with a diameter of 100 mm was used to carry out impact tests at different speeds. The specimens were mainly brittle failures. With the increase in impact speed, the failure mode of the specimens gradually transits from larger fragments to small fragments and a large amount of powder. The experimental results show that the ultra-early-strength cement-based material has a greater impact compression brittleness, and overall rupture occurs at low strain rates. Its dynamic compressive strength increases with the increase of strain rates and has an obvious strain rate strengthening effect. According to the test results, the relationship curve between the dynamic enhancement factor and the strain rate is fitted. As the impact speed increases, the peak stress rises, the energy absorption density increases, and its growth rate accelerates. Afterward, based on the stress–strain curve, the damage variables under different strain rates were fitted, and the results show that the increase of strain rate has a hindering effect on the increase of damage variables and the increase rate. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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