Strength Of Concrete Material Research Articles

Analysis of temperature stress and critical heating temperature for hydronic airport pavement

The hydronic heated pavement system has been widely used for snow and ice removal in airports and other transportation infrastructure facilities because of its good snow melting efficiency and environment friendliness. However, the study of the temperature stress distribution in hydronic pavement and the corresponding critical operation method shows many insufficiencies, which allows security problems during system operation. This paper investigated the temperature stress of the hydronic pavement near the pipes with a 3D finite element model. This model was validated by the measured temperature stress in a full-scale hydronic snow melting experiment system. The locations of the maximum compressive and the time-varying tensile stress in the hydronic pavement were reported. The maximum temperature stresses of the hydronic pavement with various design and operation parameters were compared, and the sensitive parameters were proposed. In particular, the critical fluid temperature with various design and weather parameters was presented by comparing the maximum temperature stress in the pavement with the failure strength of concrete material. The findings show the maximum compressive stress appears near the hydronic pipe, and the maximum tensile stress appears at the midpoint between two adjacent pipes after heating for 2 h. Maximum tensile stress increases with pipe embedded depth, pipe diameter, fluid temperature, and pavement capacity, but decreases with air temperature and pipe spacing. To ensure the safety of hydronic pavement, the critical fluid temperature under different conditions is controlled within the range from 38 °C to 77 °C.

Research on the dismantling of double-arch tunnel after long-term service—the case study of Huangmeishan Tunnel demolition project

Mountain tunnel structures are subject to a variety of diseases with increasing service life. Earlier tunnels may need to be demolished and expanded because of the poor serving capacity. But few studies of tunnel demolition projects are available. Based on the demolition project of Huangmeishan Tunnel, this paper discusses the demolition scheme of the double-arch tunnel, calculates the stability of the slope, and investigates the defects and material performance in the tunnel. The water leakage in the tunnel mainly occurred at the mid-partition wall and the drainage pipe was clogged severely. The largest width of the crack detected is 15 mm. Material performance tests indicated that the concrete material strength exceeded the design values. In the loading test, the largest displacements of the tunnel arch and haunch were 1.73 and 1.32 mm, which verified the safety of heavy vehicles in construction. Finally, suggestions are given to avoid similar phenomena in other tunnels during the design, construction, and operation phase. The novelty of this study lies in its comprehensive analysis of a tunnel demolition project. The findings of this study contribute to enhancing the knowledge and understanding of tunnel demolition and support the safe and efficient execution of future demolition projects.

Development of compressive strength prediction platform for concrete materials based on machine learning techniques

With the continuous development of artificial intelligence, machine learning (ML), as an important branch, is used to promote the digitalization of concrete. Considering that the verification of the strength corresponding to the concrete mixture requires strict curing system and cycle, high cost and low efficiency, ML technology is employed to predict the 28-day compressive strength of ordinary concrete for the support of engineering practices. The aim is to develop an efficient platform for predicting the compressive strength of concrete materials. Ridge Regression (RR), Least Absolute Shrinkage and Selection Operator (Lasso), Elastic Net Regression (EnR), Support Vector Regression (SVR) and K-Nearest Neighbor (KNN) are established, of which efficiency and accuracy are analyzed and calculated in detail. Then, integrated algorithms, namely Gradient Boosting Decision Tree (GBDT), eXtreme Gradient Boosting (XGBoost) and Random Forest (RF), are used to improve the prediction accuracy of a single machine learning algorithm. Finally, Grid Search (GS) optimization algorithm is used to further improve the generalization performance of the model. The results show that the R2 in training set of the single models is about 0.8, which is obviously lower than that of ensemble models (>0.95). It is encouraging that after conducting grid search optimization, the prediction accuracy of ML models can be improved obviously, of which R2 increasing by around 15%. In addition, the GS-XGBoost model achieved the most excellent prediction accuracy and generalization performance, with R2 values of over 99% in both the training and test sets. Finally, based on the results obtained, a software platform with a convenient graphical user interface (GUI) has been developed, which can greatly improve the efficiency of material design and testing required by researchers and engineers.

Estimation of Nondestructive Compressive Strength of Concrete Using Impact Force Response Signal

Abstract This study examined the potential of the impact force response signal induced by impacting an object to estimate the compressive strength of concrete nondestructively. For this study, an automatic impacting device was devised, a system was set up to measure impact force signal, and a program was developed to analyze the obtained signal and estimate the compressive strength. Concrete test specimens were manufactured and tested. Impacts were carried out on the specimens, and the impact force signals were obtained. The signals were analyzed to obtain the total impact force signal energy, and a uniaxial compressive strength test was carried out on each specimen to measure the compressive strength directly. A good relationship was formed between the total impact force signal energy and the uniaxial compressive strength. The strength was estimated from the obtained relationship for new test specimens and compared with the directly measured strength. The comparison indicated that the estimated strength and the measured strength had a close relationship. In addition, a Schmidt hammer test was carried out on the new specimens before the uniaxial compressive test, and the test results were compared with those from the impact force signal energy. The strength estimation using the impact force signal energy had a better result. The study results show that the compressive strength of concrete materials could be estimated nondestructively using the proposed method.

Experimental study on permeability of spun high strength concrete material during mechanical loading

The pretensioned spun high strength concrete pipe pile (PHC pipe pile) is widely applied in important infrastructures of off-shore zones due to its low permeability and high capacity. During the construction process and the whole service period of PHC pipe piles, the damage is inevitably caused by many reasons, which may eventually cause the early durability failure of piles. Many researches have been conducted to study the change in permeability of normal concrete due to mechanical damage. However, the relation between permeability and damage of spun high strength concrete (SHSC) is still not been studied. To quantitively investigate the change of permeability of SHSC, a series of specimens of PHC pipe piles were tested for the change of permeability during mechanical loading process in this study. As a result, the relation of stress and permeability of spun high strength concrete as well as the crack roughness of the SHSC is obtained for efficient application in engineering. Before the 40% stress ratio, the permeability of the SHSC is slightly decreased as the compressive stress increases. The mean value and standard deviation of the intrinsic permeability of the SHSC are increased as the compressive stress loading reaches the peak stress. The order of magnitude of the crack roughness ξ can be taken as 10- 4 for engineering application. Compared with the vibrate-casted concrete, the crack roughness ξ is smaller, indicating that the crack surface of SHSC is rougher than the vibrate-casted concrete.

Compressive strength of concrete material using machine learning techniques

Compressive strength of concrete material using machine learning techniques

Inclined 3D concrete printing: Build-up prediction and early-age performance optimization

To enhance the adaptability of 3D concrete printing (3DCP) to freeform and topologically optimized prefabricated structures, it is of great necessity to develop inclined 3D printing for overhang structures. In this study, the prediction criteria for stable buildability of additive stacking was established to facilitate the inclined 3D printing. The optimization of the working performance of 3D printed concrete materials is a prerequisite for achieving rapid construction. Therefore, the approach of compounding retarder and accelerator was simultaneously adopted to the hybrid cementitious material to optimize the extrudability and early-age stiffness, and furtherly improve the coordination of ultra-early age performance to the additive printing process of overhang structures. The development of green strength of concrete materials are quantitatively analyzed. The optimum replacement rate of HB-CSA to OPC is determined as 15%, and the setting time can be controlled within 35–96 min. Finally, the effectiveness of the developed evaluation method is verified by both the numerical analysis and experimental investigation, the deviation of the proposed constructability evaluation criterion can be controlled within 9.0%.

Assessment of a high strength concrete using experimental and numerical methodologies for high strain rate ballistic impacts

The high compressive strength of concrete materials enables it to be implemented for many applications. Understanding its response under high strain rate loadings is especially important for some of these applications. This study investigates the high strain rate response of a high-performance concrete denoted as BBR9 under ballistic impact. This is conducted through both an experimentally and numerically based methodology. BBR9 targets are impacted with a spherical projectile at velocities ranging from 432 to 1459 m/s and three target thicknesses ranging from 25.4 to 58.1 mm. These impacts are studied numerically by formulating a finite element model corresponding to the experimental design in this study. The mechanical response of the concrete target is captured using the Holmquist-Johnson-Cook (HJC) concrete model with its parameters calibrated to confined compressive experiments of the BBR9 concrete. The simulations show good agreement with the kinetic experimental data with an average error across all simulation points of approximately 5%, thereby validating the HJC model for this concrete in these high strain rate loading applications.

Numerical Investigation of Integral Abutment Bridges Using Finite Element Approach with Consideration of Live Load and Temperature of the Materials

The structural research is very important area of civil engineering. There is a need of research as a cumulative analysis for thermal impact on civil structures like bridges. There are numerous materials elements of civil engineering research for the Advance material, as chemical composition research to improve strength of concrete materials, contamination studies of steel material used in many huge structures, thermal loading studies etc. Hence, this paper analyzes and presents the possible causes for failure of material of Integral Abutment Bridges and substructures. Paper further presents the numerical analysis as well as finite element analysis to gain insight into the interactions between integral abutments, approach fills, foundation piles and foundation soils. The finite element analyses indicate appreciable rotations occur in integral abutments, resulting in the shear and moment reductions in the piles. Further, various elements of material are discussed which may impact the sustainability of bridges along with a numerical analysis to avoid structural failures. This study can help for researchers to identify the maintenance paradigms for bridge structures to avoid sudden failure incidences.

Optimization of sustainable concrete characteristics incorporating palm oil clinker and nano-palm oil fuel ash using response surface methodology

The production of concrete by replacing cement and aggregates with biomass materials is a low-carbon footprint and low-cost approach. In this study, the influences of nano-palm oil fuel ash (NPOFA) and palm oil clinker (POC) partially replaced instead of cement (0, 15% and 30%) and coarse aggregate (0, 50%, 100%) into sustainable concrete on workability and compressive strength are investigated using response surface methodology (RSM) methods. The RSM forecasting has presented satisfactory outcomes in optimizing the quantity of POC and NPOFA in the production of concrete with acceptable strength. The peak compressive strength is achieved for the mixture containing 0% POC and 15% NPOFA, and the mixture containing 100% POC and 30% NPOFA has the lowest compressive strength. The optimum condition is successfully predicted using RSM. The use of NPOFA binder enhances the workability and compressive strength of concrete material, in addition to enhancing the sustainability of the concrete industry. Meanwhile, the results of economic and environmental assessments also show that the addition of NPOFA and POC significantly reduces the cost and carbon emissions of concrete, and the effect of NPOFA is even more pronounced. This method might result in the noteworthy consumption of POC and NPOFA in the production of concrete and assist in achieving environmental sustainability by reducing the agricultural and industrial waste by-products.

ВИЗНАЧЕННЯ НАПРУЖЕНЬ У ТОВСТИХ ПЛИТАХ ПРИ ЛОКАЛІЗОВАНИХ НАВАНТАЖЕННЯХ

The problem of invesigating the stresses in the plates, which are subjected to the action of concentrated forces and locally distributed load is considered. The stresses were determined on the basis of the relations of the three-dimensional theory of elasticity using two methods. The first uses the symbolic Lurie method with the additional application of Vashchenko-Zakharchenko expansion formulas. The solution is constructed in the form of series, which exponentially converge at points distant from the applied forces. However, these series converge slowly in the vicinity of the applied load. In this regard, the solution of the problem is constructed by another method, using the Hankel integral transformation. The approach to find special integrals appearing in problems of the theory of elasticity for plates is proposed. After transformations, the relations for determining the stresses that include the integrals of the functions exponentially attenuating at infinity are obtained. The relations for determining the stresses in the plates on the basis of approximate equations using the Kirchhoff-Lev hypotheses are also given. For this case, the solutions for stresses subjected to the action of concentrated forces and under locally distributed load are given in analytical form. There are cases when stresses found by the elementary formulas, obtained on the basis of Kirchhoff-Lev equations with sufficient accuracy for practice, can be applied in plate bending problems. In particular, it is found that the determined stresses at the boundary opposite to the applied local load turn out to be tensile and at the same time practically accurate if the force is greater than the thickness of the plate. In this case the stresses found under the applied load are determined with larger errors. However, these stresses are compressive and are not essential in the calculation of strength of concrete materials.

Structural effects and real strain-rate effects on compressive strength of sustainable concrete with crumb rubber in split Hopkinson pressure bar tests

The dynamic increase factor (DIF) of the concrete material strength, obtained using a split Hopkinson pressure bar (SHPB), includes structural effects that do not precisely reflect the real strain-rate effect of concrete. To further clarify the real strain-rate effects of rubberised concrete (RC), an experimental investigation regarding the dynamic compressive response of ordinary concrete (NC) and RC with three rubber contents (10%, 20%, and 30%) was performed in this study. Additionally, based on a dynamic constitutive model, i.e., the Karagozian and Case (K&C) concrete model, numerical SHPB tests were conducted using the LS-DYNA software. According to the experimental results, all parameters of the K&C model were discussed, and the damage factors were modified to satisfy the mechanical properties of RC. After validating the numerical model, it was observed that the experimental DIF included the inertial enhancement and the real DIF. Moreover, because rubber particles effectively reduce the density and improve the deformation capacity of concrete, the real strain-rate effect of RC was found to be more rate-sensitive than that of NC by analysing the radial stress distribution. In addition to lateral inertia, another external source, namely, the interface friction between the specimen and bars, which can produce lateral confinement, was further studied. It was found that interface friction significantly contributes to lateral confinement; however, as the strain rate increased, the impact generally decreased. Finally, the mechanism of the strain-rate effect of RC was clarified.

Shear performance of lightweight concrete filled hollow flange cold-formed steel beams

Concrete-infilled hollow flange cold-formed steel (CF-HFCFS) beams have gained attention in the construction practices owing to many benefits in terms of their structural performances and applicability. The concrete infill ensures better structural performance by restraining the buckling instabilities of thin-walled cold-formed steel elements. However, the shear strength characteristics of CF-HFCFS are not systematically explored yet and hence there is a lack of understanding on the shear strength characteristics of CF-HFCFS beams. Therefore, in this research, shear characteristics were investigated through numerical studies by establishing and analysing three-dimensional finite element (FE) models of CF-HFCFS beams. The developed FE models were verified against the experimental data in terms of failure modes, ultimate shear capacities, and load-displacement characteristics. Then a series of parametric analyses were carried out to investigate the shear behaviour of CF-HFCFS beams against the effects of geometrical (steel thickness, beam depth) and mechanical (yield strength of steel and compressive strength of concrete) properties to further verify the shear characteristics of CF-HFCFS. Lightweight normal and lightweight high strength concrete materials were considered as infill. Also, the influence of the concrete infill on the ultimate shear capacity of the CF-HFCFS beams was evaluated through parametric studies. The ultimate shear capacities were compared against the already available design provisions. Consequently, based on the data established through of parametric analyses, modified design provisions are developed to estimate the ultimate shear capacity of CF-HFCFS beams.

Performance of concrete materials containing recycled aggregate from construction and demolition waste

The performance of recycled aggregate material from construction and demolition waste can affect concrete material strength that incorporates recycled aggregate in high volume. The current research assesses the overall benefits of recycled aggregate materials from construction and demolition waste from different sources. It evaluates the performance of concrete materials containing recycled aggregate as a substitute for conventional aggregate materials at various rates for coarse and fine aggregate materials. The investigation includes basic laboratory works on the behavior of concrete materials. These tests consist of primary characteristics of the recycled aggregate materials that can determine the material performance while substituting virgin aggregate materials. The substitution rate varies to identify the best version of the materials. It ranges from 0% to 100%, and the data included in the current research work was obtained from site visits to the existing recycling plants in Delhi, India. The maximum replacement rate of recycled aggregate materials to the natural aggregate materials has been used up to 100%, and the effects have been analyzed. The substitution rate is highly dependent on the conditions and purpose of the engineering projects. Concrete materials perform accordingly as it is related to the substitution rates directly.

Simulating failure behavior of reinforced concrete T-beam under impact loading by using peridynamics

Peridynamics has been proven to be a promising method for investigating the damage and failure behaviors of reinforced concrete structures due to its strong capacity in tackling discontinuous problems. To accurately describe the dynamic failure behavior and damage evolution of reinforced concrete structures under impact loading, the commonly used micropolar peridynamic model is improved. The improved micropolar peridynamic model considers the weak tensile strength and strong compressive strength of concrete materials, weakens the interactions between rebar and concrete in reinforced concrete structures, and optimizes the descending softening branch of the concrete constitutive model after tensile yielding. The present approach is demonstrated through a single bar pull-out test and a four-point-bending reinforced concrete beam test. Besides, by introducing the contact algorithm for rigid projectile impact and penetration to deformable targets, the peridynamic model and numerical solver are applied to simulate the failure behavior of the reinforced concrete T-beam under drop hammer impact. The peridynamic predictions agree well with available experimental observations, demonstrating the reliability and potentiality of the improved micropolar peridynamic model.

Influence of Fe2O3 Content on Acoustic Properties of Backing Materials and Development and Utilization of Acoustic Emission Sensors

Fe2O3 and epoxy resin sensor substrate materials (Fe2O3/epoxy resin composite material) are prepared in this article. A series of acoustic emission sensors are prepared by using composite material as sensor substrate, and the effect of Fe2O3 content in composite material on sensor performance is studied. The effect of Fe2O3 content in the composite material on the performance of the sensor is studied through the simulated lead‐breaking experiment, and the self‐made sensor is calibrated by using the calibration system. Nondestructive testing of concrete materials with different strengths is carried out by selecting the sensor with the best performance. The results show that the content of Fe2O3 in the composite increases to 50%, the epoxy resin matrix reaches saturation point of accommodate Fe2O3 powder, and the propagation velocity of ultrasonic waves reaches the lowest point when it passes through the composite. The sensor with 50% Fe2O3 content as a backing layer has the highest sensitivity and signal‐to‐noise ratio. The relationship between the strength of concrete material and acoustic attenuation and frequency is established by using this sensor, and the law can be used to evaluate the strength and mechanical properties of concrete material without destroying them.

RETRACTED: Effect of succinic acid on compression strength concrete material

The aim of this research is to determine the effect of succinic acid on concrete strength. Butanedioic acid, also known as amber acid and succinic acid, is a 1, 2-ethanedicarboxylic acid. In nature, succinic acid is found in its pure or esterified forms. Maleic anhydride is converted to succinic acid through catalytic hydrogenation. Succinic acid is used as a construction additive. Succinic acid is applied to concrete at a concentration of 0 to 2% by weight. Succinic acid has a plasticizing effect. Compression intensity increased as succinic acid concentration increased. Succinic acid performs optimally at a concentration of 1% in M30, M25, and M20 concrete.

Spall Behaviors of Metaconcrete: 3D Meso-Scale Modelling

Spalling is a typical tensile fracture phenomenon due to insufficient tensile strength of concrete. Concrete structure might experience severe spall damage at the rear surface of the structure owing to reflected tensile stress wave induced by impulsive load. In recent years, metaconcrete consisting of engineered aggregates has attracted attentions as metaconcrete exhibits extraordinary wave-filtering characteristics. Metaconcrete can be used to attenuate stress wave generated by impulsive load and hence possibly mitigate the spall damage. In this study, engineered aggregate is designed via the software COMSOL to have the frequency bandgap coincide with the dominant frequency band of stress wave propagating in the normal concrete (NC) specimen to reduce the stress wave propagation and hence spall damage. The wave propagation behaviors in metaconcrete specimen with periodically distributed engineered aggregates have been investigated in a previous study. This study establishes 3D meso-scale model of metaconcrete including mortar, randomly distributed natural aggregates and engineered aggregates to simulate spall behaviors of metaconcrete via the software LS-DYNA. The responses of metaconcrete composed of engineered aggregates with single bandgap and multiple bandgaps are studied. The results show that stress wave can be more effectively attenuated by using engineered aggregates with multiple bandgaps. It is found that although engineered aggregates mitigate stress wave propagation, the soft coating of the engineered aggregates reduces the concrete material strength, therefore spall damage of metaconcrete specimen is not necessarily less severe than the normal concrete, but has different damage mode. In addition, the influences of loading intensity and duration on stress wave, as well as the spall behaviors of metaconcrete specimen are also studied.

The Effect of Fire on the Strength of Concrete Material

Structural members exposed to fire may damage considerably, lose their durability, and even collapse due to the failure of the members. This work presents the results of an experimental investigation of the effect of fire on the strength of concrete. Cylindrical and beam specimens were prepared and burnt in the fire for one hour. In both cases, two systems were followed for cooling the samples, (i) natural cooling in the air (ii) forced cooling in the water. Afterwards, the compressive and flexural strength of the specimens were determined. The result shows that the strength of concrete was considerably reduced due to burning in fire. The compressive strength of cylindrical specimens was decreased by 44% and 60%, respectively, for the natural and forced cooling of the specimens. In the case of beam samples, the flexural strength was decreased60% and 69%, respectively, for the natural and forced cooled specimens. This research also reveals that the specimen cooled in air showed better performance compared to that cooled in water.
 Journal of Engineering Science 12(1), 2021, 63-68

Probabilistic framework for failure investigation of reinforced concrete wall panel under dynamic blast loads

Over the last decade, excessive devastations caused by extreme events, such as blast loading have raised significant concern on the performance of civil structural systems. Despite realizing the importance of inherent risk associated with this phenomenon, most of the studies neglected the effects of uncertainties associated with the system, wherein the design approaches have been entirely on deterministic scale. Hence, it is deemed important to identify the complexities in the system, and in this regard, a probabilistic framework is proposed which utilizes the effects of uncertainties in the system to compute the failure probabilities of a reinforced concrete (RC) structural member under extreme blast loading. The structural member adopted here is a three-dimensional (3-D) RC wall panel, which is modeled considering material and geometric nonlinearity, and the subsequent analysis is carried out under surface-burst and free airburst scenarios. High strain rate effect induced in the RC wall is modeled using available standard dynamic increase factors (DIFs) for concrete and steel. Uncertainty in the system is assumed in material capacity (strength), mechanical loads, and dynamic blast loads considering a certain mean and standard deviation. Responses are obtained in terms of deflection, stresses, and strains at center of the wall. Limit state of failure and the respective threshold limiting values are obtained from the United States Department of Defense manual, PDC-TR 06-08 (2008). Finally, first-order sensitivity analysis is conducted to show the extent of uncertainties in input parameters affecting the output response quantities. It is concluded that the uncertainty induced in the system has significant influence in the response of the wall panels under blast loading scenarios. Moreover, based on the sensitivity analysis performed, charge weight, standoff distance, and strength of concrete material are suggested to be crucial parameters for design of blast-resistant structures. To conclude, based on the currently considered scenario of intensity of blast, exposure type, and performance level required by the user, it is recommended to use wall panels of sizes more than 100 mm in civil structures, especially 125 mm to counter the effects of extreme blast loadings.