High Strength Concrete Research Articles

Seismic Performance of Shaped Steel Reinforced High‐Strength Concrete Walls: Cyclic Loading Test and Analytical Modeling

ABSTRACTThe thickness of the bottom shear walls in tall and super‐tall structures is often designed too large to meet the limit requirements of axial compression ratios, which increases the weight and cost of the structure. To address this issue, high‐strength concrete (HSC) and shaped steel are combined to form composite shear wall members. This paper focuses on seismic performance and analytical hysteresis model of steel reinforced HSC shear walls (SRHCW) under high axial compressive load. Firstly, the reversed cyclic test was conducted to investigate the influence of concrete strength and the steel ratio on the seismic performance of SRHCWs by comparing the failure mechanism, hysteretic curves, stiffness degradation, ductility, energy dissipation, and steel bar strain variation of each specimen. Then, a hysteresis model for SRHCWs was established, and the model can be used for the nonlinear analysis and seismic performance evaluation of SRHCWs. Finally, the accuracy of the proposed hysteresis model was evaluated by the experimental data. The experimental results show that under high axial compression ratio, the interstory drift ratio capacity of SRHCWs can reach 3.03% showing excellent deformation performance. The wall specimens built with different strength concrete and shaped steel ratios exhibited similar strength, deformation, and initial stiffness, indicating that the steel ratio of the wall can be effectively reduced by upgrading the concrete strength of the wall specimens while ensuring its seismic performance. The analytical model can well predict the hysteresis force–deformation curves of SRHCWs under high axial load ratios.

Shear behavior of high-strength concrete beams reinforced with carbon fiber-reinforced polymer bars

This study experimentally investigates the shear performance of high-strength concrete (HSC) beams reinforced with carbon fiber-reinforced polymer (CFRP) bars. Thirteen HSC beams were tested under four-point monotonic loading until failure, focusing on parameters such as the shear span-to-depth (a/d) ratio, longitudinal reinforcement ratio, transverse reinforcement ratio, and the type of longitudinal reinforcement (CFRP, steel, and hybrid CFRP-steel). The study analyzed failure modes, shear cracking patterns, cracking load, ultimate shear capacity, and load-deflection responses. Results indicated that shear failures in CFRP-reinforced HSC beams can occur suddenly due to the brittle nature of both FRP and HSC. Adding longitudinal steel bars alongside CFRP bars significantly enhanced the ultimate shear capacity while balancing both ductility and durability. The ultimate shear capacity was primarily influenced by the longitudinal reinforcement ratio and the a/d ratio. Specifically, the ultimate shear capacity decreased by approximately 72 % as the a/d ratio increased from 1.0 to 3.0. Furthermore, the maximum midspan deflection increased by 135 %, rising from 4.0 mm to 9.4 mm with the same change in the a/d ratio. Conversely, increasing the longitudinal reinforcement ratio from 0.6 % to 1.7 % led to a 43 % increase in ultimate shear strength due to enhanced dowel action mechanism and improved crack control, which contributed to a higher shear resistance in the concrete beam. Both CFRP and steel-reinforced beams exhibited similar shear capacity, indicating comparable shear transfer mechanisms. Additionally, a proposed shear model based on regression analysis of 139 FRP-reinforced HSC beams demonstrated better predictive accuracy than existing design codes.

Effect of incorporating ultrafine palm oil fuel ash on the resistance to corrosion of steel bars embedded in high-strength green concrete

Abstract Durability degradation in reinforced concrete (RC) constructions is commonly attributed to the steel reinforcement corrosion caused by chloride. The utilization of supplemental cementitious resources, such as waste materials from industrial and agricultural sectors, typically improves the impermeability and strengthens concrete resistance to corrosion, sulfate, and acid attacks. Therefore, the prevention of steel reinforcement corrosion is greatly important in resolving challenges related to the durability and stability of RC structures, particularly when utilizing agriculture waste materials. This approach also serves as a solution for waste disposal. The aim of this study is to investigate the corrosion-resistant characteristics of high-strength concrete that contains ultrafine palm oil fuel ash (U-POFA) as a partial replacement for cement. Four high-strength green concrete (HSGC) mixes were investigated in this study with a partial replacement of ordinary Portland cement (OPC) by U-POFA at 0, 20, 40, and 60% by mass. The aim of this study is to analyze the workability, strength activity index (SAI), compressive strength, rapid chloride permeability, linear polarization resistance (LPR) by different measurement methods, and four-probe resistivity measurement by electrical resistivity measurement method of over a curing period of 7, 28, 60, and 90 days. The use of U-POFA in the different mixes results in improved workability, SAI, compression strength, and chloride penetration resistance compared with the zero-POFA mix. It is clear from the study results that adding U-POFA as a partial replacement for OPC improved the corrosion resistance of HSGC mixtures. Thus, the incorporation of U-POFA 60% succeeded in reducing the chloride ion penetration by 80% and the LPR by 93% at the test age of 90 days, compared to the reference mixture.

The bond-slip behavior of H-shaped steel embedded in UHPC under reversed cyclic loading

To investigate the bond-slip behavior of the interface between H-shaped steel and ultra-high performance concrete (UHPC) under reversed cyclic loading, 18 steel-UHPC and 6 steel-NC composite specimens were fabricated and subjected to both reversed cyclic and monotonic loading tests. Key parameters including concrete strength, steel fiber volume fraction, embedded length of the steel section, and loading scheme were examined. The results indicate that, under reversed cyclic loading, the bond strength of the steel-UHPC composites decreased by 7 %–15 %, while the residual bond strength decreased by 16 %–57 % compared to monotonic loading. For both loading schemes, bond strength slightly decreases with an increase in embedded length but can be significantly enhanced by increasing the steel fiber volume fraction, which also improves residual bond strength and energy dissipation under reversed cyclic loading. Additionally, bond strength increases with higher concrete strength. Finally, a damage index D derived from the bond stress-slip hysteresis curves was used to represent bond degradation under reversed cyclic loads, and a constitutive model to predict the bond-slip behavior of the steel-UHPC interface under reversed cyclic load was presented.

Effects of CaO-based expansive agent on carbonation resistance of marine concrete

Marine concrete contains a high volume of supplementary cementitious materials, which benefits low-carbon concrete production. However, they may also increase the risk of cracking and accelerate the carbonation due to the pozzolanic reaction. Theoretically, the CaO-based expansive agent (CEA) can inhibit shrinkage cracks and introduce external calcium sources that aid in the carbonation resistance of concrete. A comprehensive understanding of the impact of CEA on the carbonation resistance of marine concrete is currently scarce.In this study, marine concretes with varying dosages of CEA were exposed to 20% CO2 for 28 days. The carbonation depth, carbonation coefficient, air permeability, pore structure characteristics and CO2 buffer capacity of concrete were investigated. When the CEA dosage was less than 6%, the carbonation resistance and air permeability approached the reference groups in normal-strength concrete (NSC) and high-strength concrete (HSC). However, more than 6% CEA significantly decreased the carbonation resistance of concrete, particularly for HSC. For NSC, there was an excellent correlation between the carbonation coefficient and compressive strength, while for HSC, the carbonation coefficient correlated well with porosity. Also, CO2 buffer capacity was essential to assess the carbonation resistance of marine concrete.

Development of a high-strength lightweight geopolymer concrete for structural and thermal insulation applications

Investigating the thermal insulation properties of lightweight geopolymer concrete is essential. This paper aims to develop a lightweight aggregate geopolymer concrete (LWAGC) with good density, compressive mechanical and thermal insulation properties. The dry density of LWAGC was adjusted by incorporating expanded perlite (EP). The variation in physical and mechanical properties of LWAGC with different EP content was discussed, including dry density, P-wave velocity, ultimate compression strength and elastic modulus. Based on infrared thermal imaging technology, a rapid measurement method was proposed to simulate the indoor temperature change of buildings at high ambient temperatures. The thermal insulation performance of the LWAGC with different EP contents was further evaluated. The findings show that as the EP content in LWAGC increases, there is a corresponding decrease in P-wave velocity, dry density, ultimate compressive stress, and elastic modulus. The lowest dry density of LWAGC reaches 1209kg/m3 while the ultimate compressive stress is still larger than 25.0MPa, which can used as LC25 building materials in load-bearing structures. The results also show that the addition of EP can improve the thermal insulation properties of LWAGC. The LWAGC with 50% EP content has the highest reduction rate of temperature and can maintain the indoor temperature lower than 35 °C under high ambient temperature, which have potential application prospects in the load-bearing structures and thermal insulation of tall buildings.

Experimental and analytical study of temperatures developed by the heat of hydration of high-strength self-compacting mass concrete

Experimental and analytical study of temperatures developed by the heat of hydration of high-strength self-compacting mass concrete

Evaluation of the usability of trachydacitic aggregate in rigid pavements in terms of strength and durability

The research presented here investigates the usability of trachydacitic, an unexploited material that occurred in nature, as aggregate in the construction of concrete/rigid pavements under two different curing conditions. These curing conditions are specified as 28 days 20 ± 5 ˚C water curing and combined curing including 3 days 20 ± 5 ˚C water curing + 2 days dry oven curing at 200 ± 5 ˚C. Four different combinations of trachydacitic aggregated concrete as conventional concrete (CC) and high strength concrete (HSC), with steel fiber and fiberless, were produced at different cement and water contents. Mechanical (compressive and flexural strength), durability (freeze-thaw and sorptivity) and surface abrasion properties of studied concretes were tested for each curing condition. Additionally, SEM-EDX and XRD analyses were conducted to investigate the microstructural, elemental and mineralogical changes with curing. According to the test results, the highest compressive and flexural strength were obtained from the DLPB (Trachydacitic aggregated fibrous HSC) as 75,09 MPa and 10,09 MPa respectively after the combined curing process. Moreover, the combined curing process increased the resistance of concrete to freeze-thaw and water sorptivity, while reducing its resistance to Böhme abrasion. Microstructural investigations also revealed that HSCs have a denser structure compared to conventional concretes. As a result, it was determined that the powder form of trachydacitic aggregate, unlike its coarse form, can be used in HSC road pavement construction.

Effect of high-strength SCC with and without steel fibres on the shear behaviour of dry joints in PCSBs

The structural behaviour of precast concrete segmental bridges (PCSBs) heavily relies on the strength of the joints between segments. Multi-keyed dry joints are currently the most commonly used solution in these discontinuity zones. Employing high-strength concrete is becoming increasingly common in civil engineering given its higher strength and improved durability. It specifically allows higher prestressing levels in PCSBs. Using self-compacting concrete enhances workability and adding steel fibres improves mechanical properties. The existing scientific literature includes experimental tests to analyse the shear behaviour of castellated dry joints in different concrete types. However, no experimental tests appear specifically for the castellated dry joints made with high-strength self-compacting concrete (HS-SCC) with and without steel fibres. Therefore, this experimental study conducted 31 push-off-type tests to analyse the behaviour and shear capacity of dry joints made of HS-SCC by investigating the influence of adding steel fibres to the concrete mix. The study examined crack patterns, load-displacement behaviour, failure modes and different (cracking, ultimate and residual) loads. The addition of steel fibres improved joints’ shear capacity. However, brittle behaviour was observed after reaching ultimate load when using HS-SCC, even when steel fibres were added to the concrete mix. Finally, the adequacy of existing formulations was analysed. Standard AASHTO proved to be on the unsafe side for the castellated dry joints specimens made of HS-SCC without steel fibres, and provided a good approximation for the specimens with steel fibres.

Experimental study on eccentric compressive performance of RC columns strengthened with textile-reinforced high-strength high ductile concrete

Textile-reinforced concrete (TRC) exhibits limited efficiency in strengthening RC columns, primarily due to low textile utilization and inadequate compressive strength. To improve the compressive performance of RC columns, high-strength high ductile concrete (HSHDC) is employed to replace the concrete in TRC, forming textile-reinforced HSHDC (TR-HSHDC). HSHDC possesses a compressive strength exceeding 100 MPa and a peak tensile strain of 2 %, with internal short fibers contributing to improved textile utilization. Eight RC columns, including two control columns, one HSHDC-strengthened column, and five TR-HSHDC-strengthened columns, were tested under eccentric loading. The experimental parameters included initial eccentricity, level of preloading, and number of textile layers. The results indicated that the strengthened columns exhibited good integrity at failure and generated fine cracks on the surface. Under non-preloading conditions, the load-bearing capacity and ductility gain caused by TR-HSHDC jackets were from 48.6 % to 181.7 % and 12.1–59.3 %, respectively. As the initial eccentricity increased, the load-bearing capacity gain improved. However, the strengthening effect decreased as the level of preloading increased, which was attributed to the strain lag of the strengthening material. Finally, based on the plane cross-section assumption, a calculation formula considering strain-lag behavior was established to predict the maximum load of the column strengthened with TR-HSHDC.

Effect of Traffic Vibration on Compressive Strength of High-Strength Concrete and Tensile Strength of New-to-Old Concrete Interfaces

Widening existing bridges is an important way to meet the surge in traffic demand, which is often carried out in a way that does not interrupt traffic. To investigate the effect of traffic vibration on the compressive strength of high-strength concrete and the splitting strength of new-to-old concrete interfaces, the initial to final set time of high-strength concrete C60 was first investigated in this article. Then, the traffic disturbance parameters were determined. Later, the compressive strength of C60 concrete at different stages under traffic disturbance parameters was carried out. Finally, the splitting tensile strength of new-to-old concrete specimens at different stages with different loading modes was tested. The test results indicated that the compressive strength of the specimens vibrated for 3 h and cured for 3, 7, and 28 days was increased by 4.3%, 5.7%, and 11.9%, respectively; those of the specimens vibrated for 7 h and cured for 3, 7, and 28 days was decreased by 13.7%, 20.4%, and 19.9%, respectively; the effect traffic vibration on the compressive strength of the specimens vibrated for 5 h was not obvious. When loaded along the old and new concrete joint, the specimens cracked along the joint; the splitting tensile strengths of the specimen at different disturbed stages were significantly decreased. When loaded perpendicular to the joint, the specimens cured for 3 and 7 days still cracked along the joint, and the splitting tensile strengths of the specimen at different disturbed stages were significantly decreased; while the specimens cured for 28 days cracked in the direction perpendicular to the joint, the tensile strengths of the specimens at different disturbed stages were significantly decreased. This study can promote the widening and improvement of existing concrete highways and bridges, which can save resources and improve land use.

Comparative studies on interfacial bond performance of ultrahigh performance concrete (UHPC) for sustainable repair of bridges and pavements

Ultra high performance concrete (UHPC) is emerging as an innovative sustainable solution to rehabilitate deteriorated concrete pavements and bridges. In such usage, UHPC may be cast against different substrate materials such as normal strength concrete (NSC) for bridge strengthening and rehabilitation or against high strength concrete (HSC) for shear key connections. UHPC may also be cast against precast UHPC due to the rapid increase in using precast UHPC components. Although the UHPC usage in above applications has recently increased, an investigation of bond performance between UHPC and three different substrate materials have not yet been investigated. The study examined the bond performance between cast-in-place UHPC and three different substrate materials. Three different surface preparations were considered in the current study: smooth, exposed aggregate/fibers and grooved. To generalize the outcomes from the present study, three different test methods including, splitting, bi-shear and slant shear with three different slants were selected. The experimental results demonstrated that the UHPC adhered better with NSC and HSC substrates when the pressure washing was used to expose the aggregate. Meanwhile, the UHPC had better bond with grooved surface preparation of UHPC substrate. The smooth surface should be avoided when UHPC cast against all substrates. Furthermore, the friction coefficients from the codes were overestimated for smooth surface regardless the substrate strengths. However, the design codes provided a conservative estimate for both cohesion and friction coefficients for exposed aggregate/fibers and grooved interface surface preparations.

Bending Test of Rectangular High-Strength Steel Fiber-Reinforced Concrete-Filled Steel Tubular Beams with Stiffeners

To better understand the bending performance of rectangular high-strength steel fiber-reinforced concrete (HSFRC)-filled steel tubular (HSFRCFST) beams with internal stiffeners, ten beams were subjected to a four-point bending test. The primary considerations were the strength grade of the HSFRC, the steel fiber content, the internal stiffener type, and the circular hole spacing of the perfobond stiffener. The moment–curvature and flexural load–deflection curves were calculated. The mode of failure and the distribution of cracks of the infill HSFRC were observed. The presence of steel fibers greatly improved the bending stiffness and moment capacity of HSFRCFST beams, with the optimal effect happening at a steel fiber content of 1.2% by volume, according to the experimental findings. The type of stiffener influenced the failure modes of the exterior rectangular steel tube, which were unaffected by the compressive strength of the infill HSFRC. On the tension surface of HSFRCFST beams, the crack spacing of the infill HSFRC was virtually identical to the circular hole spacing of perfobond stiffeners. When the circular hole spacing was between two and three times the diameter, the perfobond stiffener worked best with the infill HSFRC. The test beams’ ductility index was greater than 1.16, indicating good ductility. The test beams’ rotational capacities ranged from 6.26 to 13.20, which were greater than 3.0 and met the requirements of the specification. The experimental results demonstrate that a reasonable design of the steel fiber content and the spacing between circular holes of perfobond stiffeners can significantly improve the bending resistance of rectangular HSFRCFST beams. This provides relevant parameter design suggestions for improving the ductility and bearing capacity of steel fiber-reinforced concrete beams in practical construction. Finally, a design formula for the moment capacity of rectangular HSFRCFST beams with stiffeners is presented, which corresponds well with the experimental findings.

Application of novel deep neural network on prediction of compressive strength of fly ash based concrete

ABSTRACT Fly ash (FA)-based high-strength concrete (HSC) has attracted significant interest due to its potential to substitute Portland cement, offering both environmental benefits and improved performance. However, the design of FA-HSC is challenging, as key factors such as fly ash percentage, water content, and superplasticizer dosage have a complex influence on compressive strength. This study aims to develop an efficient predictive tool for FA-HSC mix design, using artificial intelligence (AI) models to address the inherent variability and uncertainty in these parameters. Six AI models, including a Deep Neural Network (DNN), were employed to analyse the relationships between mix design variables and compressive strength. The DNN model, in particular, demonstrated superior performance compared to the other models, with a high coefficient of determination (R2 = 0.89), variance accounted for (VAF = 88.3%), root mean square error (RMSE = 0.06), and residual standard error (RSR = 0.31). These results indicate that the DNN model can provide reliable predictions of compressive strength, offering a more efficient alternative to traditional trial-and-error methods. The AI-based approach can save both time and material costs while optimising performance. Overall, this AI-driven model contributes to the advancement of sustainable concrete technology by enabling more precise and resource-efficient mix designs for FA-based high-strength concrete.

Bonding strength between ultra high-performance concrete (UHPC) and the surface of normal and high-strength concrete

Bonding strength between ultra high-performance concrete (UHPC) and the surface of normal and high-strength concrete

Experimental study on the shear behaviour of high-strength lightweight concrete beams incorporating graphene oxide

Graphene oxide (GO) has achieved significant progress in the material behaviour of cement-based materials. However, research on its structural behaviour in high-strength lightweight concrete (HSLWC) structures is limited, which restricts its engineering applications. This study focused on investigating the effects of low contents of GO on the shear behaviour of HSLWC beams. A total of four HSLWC beams with GO contents of 0, 0.01, 0.03 and 0.05% (by weight of cement) were designed to observe failure modes, load‒deformation curves, shear capacities, crack behaviour and load‒strain curves under four-point loading by a 300 kN servo loading device. The results revealed that all the beams exhibited shear compression failure. GO improved the shear capacity of the HSLWC beams, and this strengthening effect increased with increase in GO content. When the content of GO was 0.05%, the ultimate load of the beam reached a maximum, which was 39.2% greater than that of the control beam. GO can endow the HSLWC beams with a certain degree of ductility. In addition, a modified JGJ 12-2006 model was proposed to predict the shear capacity of HSLWC beams containing different GO contents on the basis of a comparison of typical models. This study can provide exploratory engineering practice for evaluating and designing GO-reinforced HSLWC structures.

Class B60-B80 cement concretes using crushed gravel from the Kama field

The results of a study of the quality of crushed stone from gravel of fr. 5–20 mm and screening of crushing of fr. 0–5 mm of the Kama field were presented and an analysis of their compliance with the requirements of regulatory documents was carried out. The characteristics of the crushing products were determined: grain composition, content of crushed grains; amount of lamellar (flaky) and needle-like shape, presence of dust-like and clay particles, crushed stone crushability during compression in a cylinder, screening fineness modulus and content of reaction silica in crushed stone and screening. Compositions of high-strength concretes of class B60–B80 were developed, in which fine quartz sand was used to enrich the crushing screening, carbonate mineral powder of MP-1 grade and microsilica (MK-85) as a filler, and polycarboxylate superplasticizer Polyplast PK as a water-reducing additive. Optimal compositions were obtained with the following cement consumption: for concrete B60 with a compression strength of 78 MPa, cement consumption was 466 kg/m3, for class B70 with a strength of 91 MPa – 483 kg/m3 and for B80 with a strength of 104 MPa – 503 kg/m3. At the same time, concrete mixtures were characterized by a cone settlement of 25–27 cm.

Concrete Damage Plastic Model for High Strength-Concrete: Applications in Reinforced Concrete Slab and CFT Columns

Concrete Damage Plastic Model for High Strength-Concrete: Applications in Reinforced Concrete Slab and CFT Columns

Dynamic Analysis of Construction and Safety for a Giant Column Frame-core Tube-extension Arm Truss Structure System

Introduction Considering the influence of the shrinkage and creep of high-strength concrete on the vertical deformation and stress of structures, the mechanical behaviour during the construction of the giant column frame-core tube-extension arm truss structure system was simulated by using finite element analysis software. Methods For the engineering example of the Wuhan Center, and the safety of the construction channel under a moving load was analysed numerically. The results indicated that that there was a difference in deformation between the elevation position and design position of floor; the maximum deformation difference occurred in the middle of the tower. Results Under moving loads, the displacement and stress of the channel were 0.5 times that under full load. Conclusion As the load moved, the maximum displacement and stress of steel beam and plate changed, while the displacement and stress of the supports and the placed beam and plate remained unchanged and maintained the minimum value.

Influence of alkali molarity on compressive strength of high-strength geopolymer concrete using machine learning techniques based on curing regimes and temperature

The compressive strength behavior of high-strength geopolymer concrete (HSGPC) has been studied in this research work with varying alkali concentration using the novel machine learning techniques. The alkali concentration in the activation solution plays a significant role in the geopolymerization process and affects the resulting compressive strength. In this research work, the range between 4 M and 16 M for alkali molarity (M), 18 kg/m3 and 160 kg/m3 for NaOH and 41 kg/m3 and 229 kg/m3 for NaSi was collected from literature and used in the various design mixes of this exercise. This was necessary because higher alkali concentrations promote a more efficient dissolution and activation of the aluminosilicate compounds, leading to increased geopolymerization and the formation of more calcium silicate hydrate (C-S-H) gel. The increased C-S-H gel content contributes to improved strength development. However, there is an optimal alkali concentration range for the sustainable production of geopolymer concrete, and exceeding this range can have a negative impact on compressive strength and ecofriendly handling of concrete. A total of fifty-three records were collected from literature and deployed in modeling the compressive strength (Fc) considering various curing regimes. Three symbolic machine learning techniques such as genetic programming (GP), evolutionary polynomial regression (EPR), and the artificial neural network (ANN) are used in this research model. The relative importance values for each input parameter were also evaluated, which indicated that all factors have significant impacts on (Fc), but Age (i.e., curing regime) has the most influence compared to FA, NaOH, and CAg then the other inputs. From the model relations between the calculated and predicted values, it can be shown that the decisive model, ANN produced line of parametric equation of y = 0.995x, and produced performance indices; MAE of 2.13 MPa, RMSE of 2.86 MPa and R-squared of 0.981, which makes the ANN the most reliable model in agreement with previous applications of the technique. These are against the poor performance of the EPR and GP, which produced R-squared less than 0.8 with higher error rates. The Taylor chart and the variance distribution, which further compares the accuracy and variances of the developed models support the outcomes. Generally, alkali molarity has shown its potential in the production of HSGPC due to its role in the reactivity phases of the concrete formulation; hydration, activation, pozzolanic, and geopolymerization reactions producing the gel needed for the strength gain in HSGPC.