High-strength Concrete Specimens Research Articles

Durability Studies on High Strength Concrete

High strength concrete (HSC) is very useful for recent construction technology; the major problem of HSC is the insufficient ductility. To investigate the ductility of HSC, the entire stress-strain curve, especially in the descending branch, shall be recorded. The aim of this study is to investigate the durability of High strength concrete for different replacement levels of mineral admixtures by alternate wetting and drying phenomenon which includes; acid attack, sulphate resistance and marine Environment and also to determine the compressive strength of concrete as GGBFS partial replacement for cement. Concrete mix is designed for M80 Grade of concrete using modified ACI method. Maximum Compressive Strength of 96.4MPa and 91.6 MPa at 28days were found for the HSC specimens at a partial replacement of cement with 30% of GGBFS in normal water curing and accelerated curing tank respectively. The specimens immersed in marine solution were found to have less weight loss when compared to acids and sulphate solution.

Low-Cycle Reverse Loading Tests of the Continuous Basalt Fiber-Reinforced Polymer Column Filled with Concrete

The continuous basalt fiber-reinforced polymer column filled with concrete (BFRPC composite column) can well resist the erosion of the external environment, improve the durability of the structure, and reduce the life-cycle cost of the project. To evaluate the mechanical behaviors of the BFRPC composite column under cyclic lateral loading, laboratory low-cycle reverse loading tests were implemented on a BFRPC composite column specimen, a prestressed reinforced concrete (PRC) tube column specimen, and a prestressed high-strength concrete (PHC) tube column specimen. The failure features, hysteretic curve, and skeleton curve for these three types of column specimens were compared and analyzed through the load–displacement hysteretic curve. The results indicated that the BFRPC composite column possesses the better bearing capacity and deformation performance. The horizontal bearing capacity of the BFRPC composite column is at least three times better than that of PHC and PRC tube columns. Finally, the functional expression of the skeleton curves for the BFRPC composite column is fitted by the rational function fitting method.

Research on compressive performance of high-strength concrete confined by high-strength stirrups

Axial compressive test of high-strength concrete prism specimens confined by high-strength stirrups are carried out. The yield strength of stirrups, volumetric stirrup ratio and concrete strength are investigated for the impact of pressure performance. The results show that the confined concrete specimens with high stirrup ratio, high strength, exhibits good ductility. The use of high-strength stirrups is an effective measure to prevent a sudden drop in the falling section of the high-strength concrete stress-strain curve; under the circumstances, the application of high-strength stirrups can reduce the volumetric stirrup ratio.

Mechanical Properties of High-Strength Pervious Concrete with Steel Fiber or Glass Fiber

Pervious concrete (also called porous concrete) is one of the most promising sustainable and green building materials today. This study examined high-strength pervious concrete and ordinary-strength pervious concrete reinforced with steel fiber or glass fiber. A total of fifteen mixtures of normal- and high-strength pervious concretes with steel fiber or glass fiber were used. The goal of high-strength pervious concrete is that the 28-day compressive strength be above 42 MPa and the porosity be as close to 15% as possible to achieve technical specifications. Both normal- and high-strength pervious concretes reinforced with steel fiber (1%, 2%) or glass fiber (0.25%, 0.5%) were investigated in water permeability, porosity, compressive strength, flexural strength, elastic modulus, and toughness tests. The test results show that in both high-strength pervious concrete and ordinary pervious concrete with steel fibers added, the porosity and permeability coefficient are increased compared with the control group. The coefficient of permeability for high-strength, fiber-reinforced pervious concretes with two aggregate sizes meets the requirements of the ACI specification for structural concrete. In addition, the high-strength pervious concrete specimen H1-S2 (2% steel fiber) has the highest compressive strength of 52.8 MPa at the age of 28 days. The flexural strength of pervious concrete also increases with age. However, the flexural strength of fiber-reinforced pervious concrete did not follow this trend due to the large variation in the quality control of different fiber mixtures. However, both steel fiber and glass fiber have a certain degree of improvement in the flexural toughness, and the effect is better with steel fiber. After the flexural strength reaches the peak value, there is still about 30% of the bearing capacity, and it gradually decreases until it is completely destroyed.

Shear Behavior of Strengthened Ferrocement RC Beams by Steel Wire Mesh

This paper investigates the possibility of strengthening a ferrocement RC beam with steel wire mesh under static loading. This experimental study included testing ten normal and high-strength concrete specimens made with ferrocement. The main parameters were the steel wire mesh layers 4, 8, and 10 in addition to the compressive strength and shear to span to depth ratio of 1.8 and 2.5. The cracking load, ultimate load, deflections, initial stiffness, energy absorption, diagonal and compressive strains, and crack pattern and failure modes of such beams were discussed. The outcomes exhibited that the beams behave linearly until they reach about 21.5% of the ultimate strength for the normal concrete beam and 23.2% for the high-strength concrete beam. The steel wire mesh presence affected the ultimate strength of the concrete beam, which increased the cracking load by an average of 15.5% for the high-strength RC beam and by 24.2% for normal-strength RC ones. The ultimate load was increased by an average of 40% for the high-strength strengthened beams and with less percentage for the normal ones, which was 31%. The ratio affected the ultimate load-carrying capacity and maximum displacement directly, which increase led to a decrease in the ultimate load-carrying capacity. The strengthening by steel wire mesh enhanced the initial stiffness, ductility, and energy absorption. Doi: 10.28991/CEJ-2022-08-05-04 Full Text: PDF

Experimental study on shear performances of ultra-high performance concrete deep beams

This study presents an experimental study on the shear behaviors of fourteen ultra-high performance concrete (UHPC) deep beams. The effects of different parameters, including shear span to effective depth ratio λ, concrete strength s, steel fiber volume fraction (UHPC strength) Vf, longitudinal reinforcement ratio ρs, horizontal and vertical web reinforcement ratio (ρsh and ρsv), were considered. The other two deep beams of normal strength concrete (NSC) and high strength concrete (HSC) were also tested for comparison. Experiment results indicate that the shear strength of the UHPC specimens increased with the concrete strength, longitudinal reinforcement ratio, stirrup ratio, and horizontal web reinforcement ratio, and decreased with increasing ratio of shear span to effective depth. The UHPC specimens are ideally reinforced, while NSC and HSC specimens are over-reinforced, therefore, the strength of longitudinal reinforcement is easier to be fully utilized in the former than that in the latter. Both “beam action” and “arch action” coexisted in the UHPC deep beams. Before the applied load reached 50%∼70% of the ultimate load, the UHPC deep beams were dominated by the “beam action”; after that, they were dominated by the “arch action”. All deep beam specimens failed in shear, 13 UHPC specimens failed in shear compression, one UHPC with a lower shear span to effective depth ratio (λ = 0.554) as well as NSC and HSC specimens failed in diagonal compression, which indicated that the failure modes were affected by the ratio of shear span to effective depth λ and the concrete strength s. For the shear strength of the UHPC deep beams, 0.739 is the threshold value of λ. When λ is greater than it, the shear strength decreases with the increase of λ, while when λ is less than that, the shear strength approximately remains constant.

Study on Strength and Durability Properties of Bacterial Concrete

The primary thought of this review is to assess the strength and durability properties of high strength concrete specimens by replacing cement with bacteria for healing cracks. Concrete is the most commonly used construction material all around the world. Cracks are formed due to various reasons. The cracks act as a pathway through which water and toxic salts enter. This causes corrosion and also leads to failure of structure. Repair and Rehabilitation works are costly to be done. In order to overcome this, bacteria is induced into the concrete which leads to the process of Microbial Induced Calcium Precipitate (MICP). The cracks heal by self-healing mechanism and results in crack free concrete structure. It also improves the compressive and tensile strength. In this article a new bacterium has been cultured and identified and is used as a self-healing material in M30 Grade concrete.

Corrosion assessment in rebars of high-strength concrete using electromechanical impedance technique

The corrosion of steel rebar in reinforced concrete structures is one of the main reasons for early deterioration and premature failure of concrete structures, leading to enormous restoration costs worldwide infrastructure restoration. In the past, many sensors and techniques have been developed to monitor corrosion in steel rebar. However, the Electromechanical Impedance (EMI) technique using the piezoelectric Lead Zirconate Titanate (PZT) patches has been immersed as a promising technique to detect damages at an incipient level. This paper presents the corrosion assessment in embedded rebar in high-strength concrete using surface-bonded PZT patches through the EMI technique. The High Yield Strength Deformed (HYSD) rebars of Fe415 grade embedded in high-strength M60 grade concrete cylindrical specimens were used for the experimental work. The artificial corrosion in the embedded rebar was simulated through the accelerated corrosion test for 180 days. The conductance signatures were acquired through a surface-bonded PZT patch on embedded rebar. First, qualitative and quantitative corrosion assessment was carried out based on the conductance signature and the Root Mean Square Deviation (RMSD). Second, the effectiveness of extracted equivalent parameters was demonstrated for capturing the degradation of stiffness and mass due to corrosion. Finally, the corrosion rate is evaluated through equivalent parameters, and a comparison was made with the actual mass loss. The experimental study demonstrated that the EMI technique could be used very effectively through the statical index RMSD and equivalent parameters to identify corrosion phases and resulting losses in stiffness and mass of the structure.

Compressive strength of SF and FA based self curing HSSC: An experimental study

Typical High-strength concrete (HSC) mixtures are characterized by low water-cementitious material ratio, high content of cementitious material, and the incorporation of admixtures. Concrete needs a favourable atmosphere by providing moisture for a minimum base period of 28 days for hydration and to attain targeted strength. In the present scenario of water scarcity, the water required for curing concrete is a troublesome constraint. Self-curing concrete is one of the peculiar concretes for coping with insufficient curing caused by human error. The prime goal of this study is to identify the self-curing compound’s optimum dosage for High Strength Self-Compacting Concrete (HSSC). Likewise, it is aimed to investigate the compressive strength characteristics of HSSC. For the study, a self-curing agent namely “PEG-400” with varying percentages (0.5%, 1%, 2% & 3% by weight of cement) was investigated. An attempt was made to identify the effect of the self-curing compound on the fresh and hardened properties of HSSC, workability tests and compressive strength tests were conducted. The tests on hardened concrete were conducted after curing for 28 days for conventional HSC specimens and ambient curing for HSSC. It was observed that with the addition of 1% of PEG-400 self-curing compound, the compressive of HSC was found to be increased by 1.86% in comparison with the conventionally cured HSC. It was observed that with the addition of 1% of PEG-400 self-curing compound, the compressive strength of HSSC was found to be increased by 1.87% in comparison with the conventionally cured HSSC.

Interface strength of High-Strength concrete to Ultra-High-Performance concrete

High-Strength Concrete (HSC) has been used in the production of precast concrete structures while Ultra-High-Performance Concrete (UHPC) has been considered an option for filling the connection between HSC elements due to outstanding mechanical properties and durability. However, it is necessary to investigate how these connections would benefit from using UHPC. This study explores the influence of HSC surface preparation on the strength developed at the interface with UHPC. Surfaces with Exposed coarse aggregates, Shear keys, Exposed fine aggregate, Expanded mesh, Exposed fiber and without any special surface treatment (Smooth) were considered. Both contact measurement and sand patch test were used for quantification of surface roughness. The strength at the interface was evaluated by third-point flexural loading, push-off, slant shear and splitting tension. The flexural test was considered more representative of the adhesion than the splitting test because the failure mode of the first occurred totally at the interface. Depending on the surface preparation, HSC/UHPC interface showed a bond strength comparable or superior to that of the monolithic HSC specimen. Among the surfaces evaluated, the one with Exposed coarse aggregate achieved the best results.

Flexural Behavior of Ultra-High-Performance Fiber-Reinforced Concrete Beams after Exposure to High Temperatures.

Due to the dense structure of ultra-high-performance concrete (UHPC), it is prone to explosive spalling at high temperatures. In this paper, flexural testing of UHPC and high-strength concrete (HSC) beams was carried out at room temperature and after being subjected to different levels of thermal exposure (300–500 °C). The cross-section of the beam specimen was 150 (width) × 200 (depth) mm, and its length was 1500 mm. The flexural and shear design of the beam specimens were carried out in accordance with the ACI 318M-14 code. All of the beams were singly reinforced with two #4 rebars (minimum reinforcement ratio) as a longitudinal tensile reinforcement at the bottom of the specimen and at an effective depth of 165 mm. The flexural load was applied using the three-point load method. The results show that, at room temperature and after being subjected to different thermal exposures, compared with the HSC specimens, the stiffness of the UHPC specimens in the post-cracking stage was relatively larger and the deflection under a given load was smaller. Moreover, whether at room temperature or after exposure to different thermal exposures, the ductility of the UHPC specimens was better than that of the HSC specimens.

Structural Behavior of High-Strength Concrete Slabs Reinforced with GFRP Bars.

In this manuscript, structural testing was conducted on high-strength concrete slab specimens to investigate the behavior of such specimens when reinforced with a locally produced GFRP reinforcement. Subsequently, a finite element model (FEM) was constructed and validated against the experimental results. In the experimental phase, a total of eleven specimens (nine were reinforced with GFRP, while two were reinforced with conventional steel) were constructed and tested. The slabs dimensions are 700 mm × 1750 mm with variable thickness from 100 mm to 150 mm and different reinforcement ratios using different diameters. The structural behavior of the tested slabs was investigated in terms of ultimate load, ultimate deflection, load–deflection relationship, and crack pattern. Additionally, a nonlinear finite element model using the software ANSYS 2019-R1 was constructed to simulate the structural behavior of slabs reinforced with GFRP bars. The results obtained from the finite element analysis are compared with experimental results. The outcomes showed that the contribution of GFRP rebars in concrete slabs improved slab ductility and exhibited higher deflection when compared with traditional steel rebars. Good agreement between experimental and nonlinear analysis was obtained.

Behavior of Fiber and Nonfiber Reactive Powder Concrete in an Aggressive Environment

Abstract Durability studies have been carried out on the performance of reactive powder concrete (RPC) when exposed to a three-month (accelerated) exposure to varying sulfuric acid concentrations. The compressive strength and weight loss of the specimens were the key parameters investigated. Specimens consisted of nonfiber reactive powder concrete (NF-RPC), fiber-reinforced reactive powder concrete (FR-RPC), and a control high-strength concrete (HSC). Concentrations of sulfuric acid (H2SO4) of 1, 3, and 10 % were utilized as the attack solutions in this investigation. RPCs suffered the highest compressive strength and weight loss after 12 weeks when exposed to 1, 3, and 10 % H2SO4 solutions. It is postulated that the high levels of binding constituents within the RPC are extremely reactive with H2SO4. Results from the HSC specimens showed that a reduced cement content and coarse aggregate inclusion reduced the level of sulfuric acid attack. The presence of fibers within the RPC samples appears to provide benefits in relation to decreased weight loss, but this was not observed for higher concentrations of H2SO4. This study has shown that the durability of RPC in environments subject to high concentrations of sulfuric acid is generally not recommended.

The Effect of Construction Joint on Behavior of Reinforced Concrete Dapped End Beam

This research aims to investigate experimentally the attitude and performance of hybrid reinforced concrete Dapped End Beams. The study consists of testing thirteen specimens, all of which have similar dimensions (1000 * 120 * 250 mm). Three specimens were considered as control specimens (non-hybrid concrete) and the other specimens were strengthened in (nib and D-region) by using two types of concrete (high-strength concrete, steel fiber reinforced concrete) and with construction joint. The experimental results showed that the presence of the construction joint in the reentrant corner of specimens with non-hybrid normal concrete and specimens with non-hybrid high strength concrete leads to a decrease in strength of about (33%) and (6%), respectively and does not lead to a decrease in strength in the concrete specimens reinforced with steel fibers. Also, the presence of the construction joint in the D- region in normal non-hybrid concrete specimens and non-hybrid high strength concrete specimens as well as non-hybrid steel reinforced concrete specimens leads to an increase in the strength of about (0.5%), (10%) and (1%), respectively.

Fiber-reinforcement high-strength concrete made with expanded perlite powder

During the expansion process of natural perlite, a large amount of fine fraction of expanded perlite is unavoidably produced. These particles of expanded perlite powder (EPP) have a very low bulk density which caused some difficulty in storage and disposing. This paper investigates the effects of EPP on the properties of high-strength concrete (HSC). For this purpose, different HSC mixtures were designed and produced at two different series made with 0 and 0.5% polypropylene (PP) fibers in which EPP was used at 0-15%. The properties of HSC were investigated for compressive strength, UPV, and initial and final absorption. Variations in the mass and crushing load of HSC specimens were also evaluated after exposure to 5% H2SO4 solution. Results show that it is possible to develop HSC with 28-days compressive strength higher than 64.3 MPa by incorporating up to 15% of EPP. In addition, strong UPV-compressive strength correlation had been achieved for non-fibrous HSC mixtures containing EPP. Absorption characteristic of HSC mixtures showed all specimens can classify as “good” concrete quality. Furthermore, 0.5% PP fibers inclusion can minimize the detrimental effects of 5% H2SO4 solution attack on the mass loss values of HSC specimens containing 0-15% EPP to some extent.

Experimental Study on High-Strength Concrete, Ultrahigh-Strength Concrete and Corresponding Mortar Under Triaxial Compression

Based on uniaxial and triaxial compression tests, the present study investigates the mechanical properties of high-strength concrete (HSC), ultrahigh-strength concrete (UHSC) and the corresponding mortars with the same mix proportions of the matrixes of two types of concretes. The tests recorded the mechanical responses including peak stress, axial strain at peak point and failure modes of HSC, UHSC and mortars specimens. The test results show that the compressive strength and deformation capacity of concretes and mortars gradually grow higher with the increasing of confining pressure, and the enhancement of confining pressure on the compressive strength of mortar is significantly lower than that of concrete. For HSC and UHSC, the enhancement on compressive strength has a negative relationship with the uniaxial compressive strength and similar relationship is also found between the two types of mortars. Compared with the mortar, the increase in confining pressure can, to some extent, better enhance the deformation capacity of concrete. There are three failure modes of concretes and mortars under the confining pressure: vertical splitting failure, oblique shear failure and extrusion flow failure. Confining pressure has very little effects on the initial tangent modulus, the initial tangent modulus of the two types of concretes is larger than that of corresponding mortars, and the addition of coarse aggregate can improve the tangent modulus of HSC more significantly than UHSC. Failure surfaces for concretes and mortars under triaxial stress were identified by using the four-parameter failure criterion.

Numerical Investigations of Bond-Slip Performance in Pull-Out High Strength Concrete Specimens Subjected to Elevated

The concrete members several blessings over steel beam, like high resistance to prominent tem-perature, higher resistance to fatigue and buckling, high resistance to thermal shock, fire re-sistance, robust resistance against, and explosion. However there are some disadvantages as a result of exploitation totally different materials to product it. The most downside of structural concrete member is its deprived the strength to tensile stresses.The bond mechanism between steel bars and concrete is thought to be influenced by multiple parameters, like the strength of the encompassing media, the prevalence of cacophonous cracks within the concrete and therefore the yield stress of the reinforcement. However, properties of concrete mass has significantly effect when it was subjected to elevated temperature.The objective of this paper presents the results that allocating with the bond behavior of the rein-forcement of steel bar systems below static pull-out loading tests subjected to elevated tempera-tures. This numerical technique relies on relative slip and therefore the stress of bond distribu-tions done the embedded length and size of the bar within the concrete cylinder specimens. The obtained results square measure given and commented with the elemental characteristics of ferroconcrete members. The comparison showed smart agreement with experimental results

Finite element modelling of plain and reinforced concrete specimens with the Kotsovos and Pavlovic material model, smeared crack approach and fine meshes

Modelling of concrete through 3 D constitutive material models is a challenging subject due to the numerous nonlinearities that occur during the monotonic and cyclic analysis of reinforced concrete structures. Additionally, the ultimate limit state modelling of plain concrete can lead to numerical instabilities given the lack of steel rebars that usually provide with the required tensile strength inducing numerical stability that is required during the nonlinear solution procedure. One of the commonly used 3 D concrete material models is that of the Kotsovos and Pavlovic, which until recently it was believed that when integrated with the smeared crack approach, it can only be used in combination with relatively larger in size finite elements. The objective of this study is to investigate into this misconception by developing different numerical models that foresee the use of fine meshes to simulate plain concrete and reinforced concrete specimens. For the needs of this research work, additional experiments were performed on cylindrical high strength concrete specimens that were used for additional validation purposes, whereas results on a reinforced concrete beam found in the international literature were used as well. A discussion on the numerical findings will be presented herein by comparing the different experimental data with the numerically predicted mechanical response of the under study concrete material model.

Thermal Endurance of High Strength Fiber Reinforced Concrete.(Dept.C)

Thermal properties of high strength concrete specimens containing different contents of polypropylene fibers are experimentally investigated. The specimens were subjected to elongated period of high temperature, and thermal conductivity was measured. Reducing the water to cement ratio helps in reducing the concrete porosity and increasing the strength and results in different internal structure for high strength concrete compared will ordinary concrete and therefore influence the thermal parameters. Normally, properties of coarse aggregates tend to govern the overall thermal properties of ordinary concrete. Thus natural gravel, basalt, granite and dolomitic limestone are employed in the experimental program. Thermal conductivity is measured for specially designed specimens. A comparison is carried out with the corresponding results of ordinary concrete for dry and fully saturated samples. The findings indicate some major differences in the thermal features, which should be addressed in thermal analysis and insulation problems.

Thermal Emission analysis to predict damage in specimens of High Strength Concrete

In this paper thermal analysis was applied to determine the “Critical Stress” of concrete, different from its ultimate strength, able to produce the first damage in the structures under compressive loads. The Critical Stress can be thought as the stress able to produce the beginning of fatigue rupture within the material. Several specimens of high strength concrete were tested in order to define the incipient crack phenomena, also in internal part of the specimen not accessible by direct inspections, with the aid of infrared thermography. A finite element analysis completes the study and compares, for the same static loading conditions, the stress state with the experimental thermographic images. The final results show as the coupling of normal compressive test and the acquisition of the thermal images can be a useful aid to estimate a security stress value, indeed the Critical Stress, before the Ultimate Serviceability Limit (SLU) of the structure, defined as the maximum load condition before its failure.