Concrete Test Research Articles

Performance of Sustainable Green Concrete Incorporating Quarry Dust and Ferronickel Slag as Fine Aggregate.

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete.

Study on Sorptivity Test on Fly Ash Aggregate Concrete

Aggregate is most widely used in reinforced concrete construction. In this investigation, fly ash aggregates were used in concrete and its effect on durability of concrete was studied. The fly ash was collected from Mettur Thermal Power plant. Then the cement fly ash proportion of 10:90, 12.5:87.5, 15:85, 17.5:82.5, 20:80 and 22.5:77.5 were adopted to get fly ash aggregates. The Particle size distribution, Specific gravity and Water absorption tests on aggregates were conducted. M20 grade of concrete was considered. The fresh concrete tests like Slump test and Compacting factor test were conducted. For the plain concrete and fly ash aggregate concrete the cubes were cast. All the specimens were cured in a curing tank. The plain and fly ash aggregate concrete cube specimens were cast and tested at the age of 28days and 56days. Sorptivity and saturated water absorption tests were conducted on these plain and fly ash aggregate concrete specimens. The results were tabulated and compared by drawing graphs. Based on the results obtained, conclusions and suggestions were made.

The fracture energy of concrete reinforced with double-helix macro basalt-fibre-reinforced polymer fibre

A novel type of fibre – double-helix macro basalt-fibre-reinforced polymer (DHM BFRP) fibre – is proposed to increase the cracking, tensile strength and ductility of concrete. The novel fibre is made from micro basalt fibres and resin, twisted together in a double helix. BFRP offers high tensile strength, good corrosion resistance and low cost, while the double-helix geometry provides excellent bond–slip performance between the fibre and the concrete matrix. Three-point bending (3PB) tests were conducted to measure the fracture energy of concrete reinforced with DHM BFRP fibres. The influences of fibre orientation (aligned and random) on cracking load, peak load, flexural strength and fracture energy were analysed. Compared with random DHM BFRP fibres, aligned fibres resulted in a 26.4% higher fracture energy and a 29.7% increase in flexural strength. Finite-element models of the 3PB tests were established using LS-Dyna. The Karagozian & Case concrete model was calibrated based on the fracture energy results to obtain a material model of fibre-reinforced concrete (FRC) considering fibre orientation. The errors between the simulated and tested maximum loads for 3PB tests of plain concrete, FRC and fibre-reinforced self-compacting concrete were 8.3%, 4.0% and 11.4%, respectively, indicating that the simulated and test results were in good agreement. This study provides a theoretical foundation and technical support for practical engineering applications of DHM BFRP fibres.

Corrosion characteristics of concrete by landfill leachates of different ages

Landfill leachate is a highly corrosive pollutant, and the composition of landfill leachate varies greatly between landfill ages. Landfill leachates of different ages pose a corrosive danger to concrete structures. In this study, four landfill leachates of different ages were selected for concrete immersion corrosion tests to elucidate the corrosion characteristics of concrete. Measurements of concrete mechanical property indices were combined with microscopic analysis methods, such as X-ray diffraction and scanning electron microscopy. The effects of the compositional differences of the landfill leachate of different ages and contact times on the concrete were analyzed and evaluated. The test results showed that the young landfill leachate slowed down the hydration process of concrete and promoted the generation of expansive corrosive crystals such as gypsum and calcium sulfate, which changed the internal microstructure of the concrete and caused irreversible damage. Exposure to leachates caused a decrease of the concrete quality, compressive strength, and dynamic elastic modulus to below their initial values. The participation of intermediate and mature landfill leachate in the hydration process of concrete promoted the hydration reaction in the short term. However, with the prolongation of the test period, this enhancement gradually weakened, and at the same time, the sulfate in the landfill leachate and the hydration products generated ettringite, which produced expansion stress on the internal structure of the concrete, destroying the structure and decreasing its strength. The experimental results of this study provide theoretical support for the treatment of different ages of landfill leachates and the design and protection of landfill concrete structures.

Study on the Effect of Post-Freezing Mechanical Properties of Polypropylene Fibre Concrete Based on BAS-BPNN

An indoor accelerated freezing and thawing test of polypropylene fibre-reinforced concrete in chloride and sulphate environments was conducted using the “fast-freezing method” with the objective of investigating the damage law of the post-freezing mechanical properties of hydraulic concrete structures and studying the effects of different mixing amounts of polypropylene fibres on the mechanical properties of concrete. Furthermore, in order to reduce the cost of concrete tests and shorten the time required for conducting concrete tests, a backpropagation neural network based on a Beetle Antenna Search algorithm (BAS-BPNN) was established to simulate and predict the mechanical properties of polypropylene fibre-reinforced concrete. The accuracy of the model was verified. The results indicate that the order of improvement in the macro-physical properties of concrete due to fibre doping is as follows: PPF1.2 exhibited the greatest improvement in macro-physical properties of concrete, followed by PPF0.9, PPF1.5, PPF0.6, and PC. When the freezing and thawing medium and the number of cycles are identical, all four assessment indexes (R2, RMSE, SI, MAPE) demonstrate that the four groups of polypropylene fibre concrete exhibit superior performance to the control group of ordinary concrete. This indicates that polypropylene fibre can enhance the mechanical properties and freezing resistance of the concrete matrix, delay the process of freezing and thawing damage to the matrix, and extend the lifespan of the matrix, yet cannot prevent the ultimate failure of the matrix. The application of intelligent algorithms to optimise the parameters of an artificial neural network model can enhance its capacity to generalise and predict the mechanical properties of concrete. In terms of the coefficient of determination (R2), the Beetle Antenna Search algorithm (0.9782) outperforms the Particle Swarm Optimization (PSO; 0.9676), the Genetic Algorithm (GA; 0.9645), and the backpropagation neural network (BPNN; 0.9460). The improved backpropagation neural network based on the Beetle Antenna Search algorithm not only avoids the trap of local optimality but also improves the model accuracy while further accelerating the convergence speed. This approach can address the complexity, non-linearity, and modelling difficulties encountered during the freezing process of concrete. Moreover, it offers relatively accurate prediction outcomes at a reduced cost in comparison to traditional experimental methodologies.

The behavior of reinforced concrete frames exposed to high temperature under cyclic load effect

Continued use of the structure through minor renovations and repairs without a complete and accurate determination of the extent of damage to the structure and its elements exposed to high temperature effects due to fire, etc. will cause more loss of life and property in the event of an earthquake that may occur later. The aim of this study is to determine the losses on the lateral load and energy damping capacities and stiffness of reinforced concrete frames exposed to 200, 400, 600 and 800 ℃ high temperatures for 60, 120 and 180 min. For this purpose, 13 reinforced concrete frame test elements with the same concrete and steel material properties and dimensions were produced. All reinforced concrete frame test members were brought to the specified target temperature within one hour and exposed to high temperature effects for 60, 120 and 180 min at these target temperatures. The test members then allowed cooling down on their own and when they reached room temperature, they removed from the oven and subjected to cyclic lateral loading tests. The data obtained from the cyclic lateral loading tests processed to obtain lateral load - horizontal displacement, stiffness - horizontal displacement, cumulative energy consumption - horizontal displacement and strength envelope curves for each test element. According to the results of the cyclic lateral loading tests, it was determined that the lateral load carrying capacities of the test members exposed to high temperature for 60, 120 and 180 min decreased by 24 %, 33.33 % and 36 % in push, and by 25.76 %, 37.6 % and 38.72 % in pull, respectively. In addition, the energy consumption of the test elements exposed to high temperature for 60, 120 and 180 min decreased by 30.98 %, 42.41 % and 39.62 %, respectively, compared to the reference test element. The initial stiffness of all test elements exposed to the high temperature effect decreased compared to the initial stiffness of the reference test element not exposed to the high temperature effect. According to these results, the effect of high temperature causes losses in many parameters that are of vital importance in the building elements, but also highly affects the earthquake behavior of the building.

Increasing Compressive Strength of Self Compacting Concrete with MasterGlenium and MasterSure

The growth in development complexity demands innovation in the construction industry. Self-compacting concrete (SCC) can flow and fill mold cavities without additional vibration, offering an efficient solution for structures with complex shapes or tight spaces. In addition, SCC can speed up bonding and simplify workability by adding MasterGlenium and MasterSure superplasticizers. However, its use is limited due to a lack of understanding of the optimal composition of the mixture. The research aims to determine the effect of adding MasterGlenium and Maste Sure in the concrete mixture on the compressive strength of concrete. Experimental research was conducted with a mixture of MasterGlenium additives at 0.25%, 0,30%, 0,35%, 0.40%, and MasterSure 0.30% of the total binder. Slump and compressive strength tests of concrete are carried out to determine workability and quality performance. The research results showed that the optimal concrete mix with the addition of MasterGlenium 0.35% and MasterSure 0.30% was 25.39 Mpa, higher than Normal concrete 15.21 Mpa. The slump test results confirm that the concrete is classified as SCC. This shows the importance of the composition of MasterGlenium and MasterSure superplasticizers on the compressive strength of SCC concrete. So, the results of this research can be used to improve the quality of concrete structure projects.

Evaluation of Design Parameters (α and β) for Analysis and Design of Piles on Soft Clays

This paper presents the analyses of 12 prestressed concrete instrumented test piles (TPs) that were driven in different bridge construction projects of Louisiana as part of a load testing program. The 12 TPs were driven mainly in cohesive soils. Detailed soil characterizations including both laboratory and in situ tests were conducted to determine the different soil properties. The TPs were instrumented with vibrating wire strain gauges to be able to calculate the distribution of skin friction and end-bearing capacities separately. Static load tests and dynamic load tests were conducted on each TP after end of driving to calculate the ultimate load capacity. Fifty six soil layers exhibiting clayey soil behavior and sandy soil behavior dominated the remaining 15 soil layers. The total stress parameter (α) and the effective stress parameter (β) were back-calculated for each soil layer. The α values ranged from 0.22 to 1.80, and the β values ranged from 0.11 to 0.83. Regression analyses were performed on 42 soil layers (75% data) to develop an empirical model to predict α as a function of undrained shear strength. The remaining 25% of the data were used to verify the developed model, and good agreement was observed between the measured and predicted values.

Effect of uniaxial loading on the spalling of concrete panels for Melbourne's Metro Tunnel Project

AbstractThe Metro Tunnel is a Victorian Government funded infrastructure project which will create a new end‐to‐end rail line from Sunbury in the west to Cranbourne/Pakenham in the south east, with bigger and better trains, next generation signaling technology and five new underground stations. This article provides a detailed summary of the structural fire testing requirements for the platform tunnel side wall and arch lining in the Metro Tunnel's State Library and Town Hall stations. Contrasted to building fires, tunnel fires are more significant within a few minutes due to the confined space which can cause concrete spalling and jeopardize the bearing capacity of the tunnel, which is a significant concern to designers. The catastrophic European tunnel fire events in 1999 and 2001 led to the development of innovative regulations and recommendations, including guidelines endorsed by the European Federation of National (EFNARC 132F r3:2006) and Efectis R0695:2020. This paper explains the methodology taken to design the fire rated concrete test for the platform tunnel side wall and arch lining in the State Library and Town Hall stations of Melbourne's Metro Tunnel Project for structural stability for the period of a serious fire event. For the first time, uniaxial loading (500T) was applied to five large‐scale flat concrete panels (1800 × 1800 × 400 mm) which are normally unloaded during fire exposure and exposed to the RABT ZTV (rail) fire curve. The first testing program investigated the influence of polypropylene dosage in the concrete mix design and its effect on the magnitude and severity of concrete spalling. The results indicated that the recommended 2.0 kg/m3 polypropylene dosage requirement as specified by Eurocode is conservative. Concrete mix designs with a stable aggregate and the correct curing regime can mitigate spalling at significantly lower polypropylene dosage rates. The water pooling effect was evident during the fire testing and the surface cracking that developed was vertical to the surface, allowing for the release of the pore water pressure build‐up.

Mechanical testing and engineering applicability analysis of SAP concrete used in buffer layer design for tunnels in active fault zones

Abstract To tackle the challenge of dislocation damage when tunnels traverse active fault zones, this study introduces the concept of using brittle buffer materials for anti-dislocation. Building on this concept, we propose a novel concrete buffer material utilizing large-sized spherical super absorbent polymers (SAP) as a porogen, aimed at ensuring the safety of tunnel structures during active fault dislocations. To investigate the feasibility and superiority of SAP concrete as a buffer material compared to other similar materials, we prepared samples with three different SAP concrete proportions and conducted a series of physical and mechanical tests. The results show that SAP pre-hydrated with 0.2 mol·L−1 sodium carbonate solution exhibits a slower rate of moisture loss in the cement slurry, aiding the hydration reaction of concrete. The permeability coefficient of SAP concrete is approximately 10−7 cm·s−1, slightly lower than foam concrete of the same density level. SAP concrete buffer material demonstrates significant brittleness, in contrast to the mostly ductile nature of other buffers such as foam concrete and rubberized concrete. Utilizing the brittle nature of SAP concrete materials, when applied to tunnels affected by stick–slip active fault dislocations, its instantaneous loss of compressive capacity provides excellent yield performance, thus protecting the tunnel lining from damage. However, under certain circumferential pressure conditions, both the peak and residual strength of SAP concrete significantly increase. High peak and residual strengths do not favor the effective buffering effect of SAP concrete; therefore, an approach involving the intermittent arrangement of precast buffer blocks has been proposed for application.

Reducing shallow foundation rotation due to reverse faulting using predefined shear planes

Permanent ground displacement due to faulting during strong earthquakes threatens the stability of civil structures. To protect surface foundations from faulting, several mitigation techniques have been developed. Owing to the limitations of earlier mitigation strategies for unidentified reverse faulting conditions, this research presents a novel mitigation system, including the installation of sliders beneath the wings of a V-shaped concrete element, to reduce footing rotation. To evaluate the effectiveness of the suggested mitigation strategy, concrete strength tests, a physical centrifuge test and a comprehensive numerical study for different fault locations and dip angles were conducted for the first time. Results demonstrated that the placement of the sliders beneath the V-shaped wings had a significant effect on dissipating the fault dislocation. Compared to the previous mitigation techniques, the proposed system decreased the foundation rotation from a high value (11°) to a low value (3·2°) for the worst-case scenarios. Furthermore, the friction coefficients among sliders and concrete, the concrete wing inclination angle, length and thickness were critical parameters to design the optimum proposed system. In contrast, soil layer thickness and relative density did not significantly affect the footing rotation.

ANALYSIS OF THE QUALITY OF FABA (FLY ASH BOTTOM ASH) BASED CONCRETE AS AN FINE AGGREGATE SUBSTITUTE WITH REFERENCE TO MIXTURE PROPORTION IN WORK UNIT PRICE ANALYSIS

In this research, the author used FABA (Fly Ash Bottom Ash) waste as an alternative to fine aggregate. This research can determine the physical properties of faba aggregate with the results of sieve analysis testing of faba aggregate which has a fineness modulus value of 2.34 which is included in the medium fine aggregate type. Testing for water content in faba fine aggregate in SSD conditions was 3.09%. Faba fine aggregate sludge content is 0%. Testing the organic substances on the faba fine aggregate showed that the NaOH color was reddish brown, because it needed to be washed first before being used as a concrete mixture. The face dry specific gravity of faba fine aggregate is 2.2 gr/cm2. Therefore, faba aggregate can be used as a substitute for sand because it has physical properties that meet the requirements as fine aggregate. Results The final compressive strength of faba concrete and normal concrete as a control at the age of 7 days and 28 days has reached the planned quality, but the compressive strength at normal concrete (control) is higher than faba concrete. With the results of the standard deviation values ​​at 7 days and 28 days, it is included in perfect workmanship condition because it has a standard deviation value of less than 3 MPa. The results of the concrete flexural strength test were only normal K300 concrete with a flexural strength of 4.60 MPa, which complies with SNI 2847:2013, namely producing a minimum flexural strength of fs = 4.4 MPa. Normal concrete has a much higher flexural strength than faba concrete, and the higher the quality of the planned concrete, the greater the resulting flexural strength of the concrete.

Reliability of using secondary and tertiary treated wastewater in concrete mixing and curing

AbstractWater scarcity is a problem that faces many regions. In a developing and arid countries, the need for fresh water is exponentially increasing. One of the most water consuming industries is the construction industry, especially in concrete manufacturing. This research is an evaluation of the Reliability of recycled wastewater to be used in concrete manufacturing. Two different wastewater treatment regimens are implemented: secondary and tertiary treated wastewater. The treated wastewater, either secondary or tertiary, replaces potable water with percentages of 25%, 50%, and 100%. The mixture of the two types of water is used in concrete mixing and curing. Control specimens with pure potable water are cast for the comparison. The experimental program investigated the cement setting, and for fresh concrete slump test is performed on all concrete mixtures. The hardened concrete is tested in compression and flexural strengths at ages of 7 days, 28 days, and 90 days. To investigate concrete durability, permeability test is conducted in addition to sulfate attack resistance. The concrete chemical composition is compared using the X-Ray Defragmentation (XRD) test. The results show that the treated wastewater may delay both the initial and final setting. The phenomenon is more pronounced in secondary treated wastewater. No significant effect on concrete performance in the fresh state is detected. For the compressive strength, both treatment regimens can be safely used. However, the flexural strength is reduced at the late ages. Using treated wastewater affects the permeability of concrete to be more durable and protect the reinforcement steel from rusting. For the XRD test, the results show different intensities and positions of the peaks of the different compounds encountered in the treated wastewater. Under sulfate attach, the treated wastewater specimens give higher expansion compared with potable water. In conclusion secondary and tertiary treated wastewater can be used in concrete mixing and curing. However, the manufactured concrete should be protected from sulfate attack to avoid excessive expansion.

Analysis of Environmentally Friendly Concrete (Green Concrete) Using Coal Fly Ash as a Substitute Material for Portland Cement in Road Pavement

The development of technology in the field of construction, especially in concrete technology, is now becoming more rapid, which requires concrete materials that can adapt to the times. As well as for energy savings from normal concrete materials from a mixture of fine, coarse, cement and water can now be added to other materials. In this era, the use of cement for concrete making materials is very identical, therefore to reduce the use of cement, it is necessary to mix other materials. The research method that researchers use is the experimental-laboratory method by making test objects in the form of concrete cylinders with a size of 15x30 cm. Analysis of concrete testing using Fly Ash mixtures in this study there are several variations of fly ash mixtures, namely fly ash 50%, 60%, and 70%. In testing several Fly Ash mixtures produced a compressive strength value of 50% Fly Ash percentage and 2% Accelerator of 161.630 kg/cm2, 60% Fly Ash and 2% Accelerator of 154.189 kg/cm2, 70% Fly Ash and 2% Accelerator of 92.670 kg/cm2. In the results of this study with several variations of fly ash mixtures, the highest compressive strength value was obtained at a percentage of Fly Ash 50% and Accelerator 2%, which amounted to 161.630 kg/cm2 with the first variation test specimen sample at the age of 28 days of concrete.

Impact toughness and dynamic constitutive model of geopolymer concrete after water saturation

The dynamic compression test of geopolymer concrete (GC) before and after water saturation was carried out by the split Hopkinson pressure bar (SHPB). And the effects of water saturation and strain rate on impact toughness of GC were studied. Based on Weibull statistical damage distribution theory, the dynamic constitutive model of GC after water saturation was constructed. The results show that the dynamic peak strain and specific energy absorption of GC have strain rate strengthening effect before or after water saturation. The impact toughness of GC decreases after water saturation. The size distribution of GC fragments has fractal characteristics, and the fractal dimension of GC fragments after water saturation is smaller than that before water saturation. The dynamic constitutive model based on Weibull statistical damage distribution theory can accurately describe the impact mechanical behavior of GC after water saturation, and the model fitting curves are in good agreement with the experimental stress–strain curves.

Comparative study of pile quality control techniques

This article delves into the critical realm of quality control in pile foundation construction, presenting a comprehensive exploration of both destructive and non-destructive testing methodologies. Focused on enhancing structural integrity and reliability, the study evaluates techniques such as concrete strength testing, core sampling, Cross-Hole Sonic Logging (CSL), and Pile Integrity Testing (PIT). Results from field observations conducted during construction of the Light Rail Transit (LRT) system in Astana showcase the effectiveness of non-destructive methods, with 1,896 bored piles subjected to rapid testing. Significant findings reveal that approximately 75% of tested shafts exhibited anomalies, emphasizing the necessity for meticulous quality control. The article concludes by advocating for the adoption of advanced quality assurance protocols to mitigate risks and ensure the robustness of pile foundations in construction projects.

UTILIZATION OF HIGH-VOLUME FLY ASH AS A SUPPLEMENTARY CEMENTITIOUS MATERIAL IN ENVIRONMENTALLY FRIENDLY CONCRETE

Innovations in material technology are expected to reduce the use of commercial cement and replace it with other environmentally friendly materials with the same performance as normal concrete. Aim: This study aim to analyze the mechanical property of High-Volume Fly Ash Concrete (HVFAC) using F class fly ash with different mix percentages. Methodology and Results: The experiment was conducted in laboratory scale. Four variations of test specimens consisted of: 1 variation (F0), which is conventional concrete with 100% Portland cement as control specimen, and three variations of HVFC (F70, F80, and F90), which were made with fly ash content (%) 70, 80, and 90 of total cementitious. Fresh concrete testing to determine workability, while hard concrete testing is done by density and compressive strength tests at the age of 3, 7, and 28 days on specimens that have been treated with the water submerged curing method. Conclusion, significance, and impact of study: All HVFAC specimens fulfill the Self Compacting Concrete (SCC) category. The compressive strength test results at 28 days showed that the addition of fly ash percentage caused a decrease in compressive strength values in all HVFAC variants, but still exceeded the minimum requirements of high and medium quality concrete. All HVFAC variations meet the requirements of ASTM C618-23 based on the evaluation of Strength Activity Index (SAI) values at 7 and 28 days of age. The utilization of 90% fly ash as a cement substitute resulted in an environmentally friendly concrete product based on the concept of cleaner production.

Study on Temperature Control and Cracking Risk of Mass Concrete Sidewalls with a Cooling-Pipe System

Hydration heat of early-age sidewalls can cause cracks owing to thermal stress, reducing the durability of underground space structures. The heat can be removed by the flowing water in the cooling pipe system. However, the cooling pipe may cause thermal stress due to the temperature gradient in the region adjacent to the cooling pipe, resulting in concrete cracking. To minimize the temperature peak of sidewalls and cracking risks in the region adjacent to the cooling pipe, the crack-distribution characteristics, temperature, and strain evolution of an early-age sidewall with a cooling pipe system are analyzed by concrete temperature and strain tests. Furthermore, a model that accounts for the early-age behavior of concrete and cooling-pipe effects is developed and solved. Finally, the effects of cooling-pipe parameters and ambient temperature on the sidewall’s temperature field and cracking risk are analyzed. The results indicate that the cracks emerge in the first two weeks after concrete pouring; most are vertical, and a few oblique cracks emerge in the wall corner. The tensile stress in the region adjacent to the cooling pipe gradually decreases along the flow direction. Reducing the water temperature and increasing the flow rate reduces the sidewall’s temperature peak and cooling rate. However, they increase the cracking risk in the region adjacent to the cooling pipe. When the flow rate exceeds 0.6 m3/h, further increasing the flow rate does not significantly affect the temperature field. Reducing the distance between cooling pipes reduces the temperature peak, cooling rate, and cracking risk in the region adjacent to the cooling pipe. In high-temperature environments, the cracking risk in the region adjacent to the cooling pipe increases significantly.

Concrete CFRP-Reinforced Beam Performances, Tests and Simulations

Nowadays, the increasing necessity of consolidating and renewing buildings represents a big challenge for engineers. Structural consolidation using composite materials glued on the damaged surface using high-performance adhesives could be a viable technical solution. In this context, this article’s aim is twofold. First, it presents the experimental results of the investigations performed on three types of reinforced concrete (RC) beams—without consolidation (G1), consolidated with carbon fibre-reinforced polymer (CFRP) lamella of SikaCarboDur (G2), and consolidated with CFRP fabrics (G3)—to determine their behavior under different loads. Second, a numerical study was performed using Finite Element Analysis (FEA) to compare and confirm the experimental results (stress, displacement). The numerical simulation shows that the stress in the areas covered by wraps is approximately 20% lower than in those without wraps.

Laboratory test and meso-scale discrete element modelling on creep behaviors of concrete

In this work, a series of concrete creep tests with different stress conditions were carried out by laboratory tests and the discrete element method (DEM). The instantaneous strain, creep strain, creep rate, as well as creep nonlinearity ratio were obtained by laboratory tests. Meanwhile, a DEM micromechanical model, including coarse aggregate with actual geometry, homogenized mortar, and interfacial transition zone (ITZ), was established and the validity of numerical results was verified by laboratory tests. On this basis, the mesostructure characteristics (i.e., contact force and force chain) were obtained by DEM micromechanical-based analysis. The results show that the creep strain increases with the increase of stress level and with the extension of load holding time, and the creep develops rapidly within 60 days and slowly after 60 days. As the applied stress level increases, the nonlinearity of creep strain becomes more obvious, all specimens achieve a stable nonlinear ratio after about 20 days. Meanwhile, the contact force in mortar and ITZ all tend to increase with the increase of stress level, resulting from the viscoelastic slippage in burger contact. The average contact force of ITZ is larger than that of mortar, and a difference of about 20% can be observed. The peak probability density of mortar occurs at fi/f‾ = 0.6–0.8, while that of ITZ occurs approximately at fi/f‾ = 0.5. By comparison with other models, the improved nonlinear viscoelastic-plastic creep model can well predict the creep behavior.