Tensile Properties Of Concrete Research Articles

Effect of Natural Raw Fibers on Mechanical Properties of Fiber Reinforced Concrete: A Step Towards Sustainability

Abstract Concrete is the mostly used constructional material in industry and have versatile quality in nature. Fibrous concrete has significant factor that improve the scale and value to concrete for humid environments. Day by day abundant demand and use of concrete is increasing in construction industry. It is considered as a 2nd largest building material due to the major productivity. By the use of fibrous concrete, some bonding issues have been addressed and mitigate the environmental problems. Keeping in this view, an experimental based study is conducted to evaluate the strength of fiber reinforced concrete at different percentages 0%, 0.5%, 1.0%, 1.5% and 2.0%. All percentages are added by the weight of concrete with all fibers. In this connection, forty-five cylinders of five mixes are prepared. Workability checked of fresh concrete during the pouring of concrete cylinders. Poured cylinders’ samples are left for different curing ages at 7 and 28 days. Thirty cylinders for compression at 7 and 28days but fifteen cylinders for split tensile test at 28days with all fibers i.e. glass fiber, steel fiber, coconut fiber and polypropylene fiber. After curing, compression and split tensile tests are performed to check the strength of hardened concrete. Workability of five mixes lies between 40-90mm and compression strength is increased at 1% replacement with all fibers which is suitable for sustainable construction. Also, fibrous concrete is suitable for humid environment where high strength and voids less concrete are required like plaster in external walls and all structural components. Addition of fibers in concrete may improves the strength parameters as well as to increase the bonding and tensile properties of concrete. It reduces the quantity of water to be used in concrete. Also, the use of different types of fibers has been proved to be economical and is considered as environmentally friendly construction material.

Development of ultra-ductile strain hardening 3D printed concrete composite utilizing critical fiber volume and coarse aggregate

This study presents a promising approach of integrating coarse aggregates and steel fibers (smooth straight and corrugated) into 3D printed concrete to enhance both strain-hardening and ductility properties. The research delves into the engineering design of fiber reinforced 3D printed concrete by analysing the effect of critical fiber volume and coarse aggregate addition on concrete tensile properties. The combination of coarse aggregate and fiber enhances the material ability to withstand increasing loads by promoting plastic deformation, while mitigating the crack formation and propagation. Experimental methodology for engineering design of fiber reinforced 3D printed concrete is elucidated via critical fiber volume analysis, strain hardening analysis, and ductility assessment under direct tensile loading. The results indicate synergistic effect of corrugated fibers and coarse aggregates on the tensile properties and unlike straight smooth fiber, corrugated long fibers significantly contribute to excellent strain hardening behaviour. The new 3D printed concrete composite developed in this study exhibited distinctive yield point with high strain hardening factor (1.62), ductile factor (10.86), and enhanced energy absorption capability (+105 kJ/m³). These enhanced properties make the material particularly suitable for applications in seismic-resistant structures and other load-bearing applications where ductility and energy absorption are critical.

Tensile strength prediction of crumb rubber concrete based on mesoscale modelling

ABSTRACT This study presents an experimental study and a mesoscale model for evaluating the tensile performance of crumb rubber concrete (CRC). In the experimental study, indirect tensile strengths of CRC with 6%, 12% 18% rubber contents were tested. Then the tested CRC samples were modelled as a five-phase material containing rubber, coarse aggregate, mortar, aggregate-mortar interface layer, and rubber-mortar interface layer. Numerical results from the mesoscale model agreed well with experimental tests. Parameter analysis was carried out to investigate the content, size, shape of rubber particle, thickness of interface layer on the tensile strength of CRC. Numerical results also indicated that rubber content was the governing influencing factor on the tensile strength reduction. As comparison, the influence from rubber size and rubber shape was relatively low. For a specimen with constant rubber content and size, changes in the distribution of rubber particles resulted in slight changes in the tensile strength of CRC as well. The effect of rubber particles on the tensile properties of concrete was similar to that of pores. Finally, tensile strength prediction formula was developed based on the pores model proposed in this study.

Experimental study on the axial tensile properties of polypropylene fiber reinforced concrete

In order to study the axial tensile properties of polypropylene fiber reinforced concrete, an axial tensile test device for concrete is developed in this paper. The device is composed of three parts: rigid frame, spherical hinge and puller, and specimen fabrication part. The test device can accurately measure the tensile strength and peak tensile strain of concrete, and perfectly solves the eccentricity problem of concrete specimens under tension. It can measure the post peak segment tensile strain, such that the whole process tensile stress–strain curve can be obtained. The axial tensile test of polypropylene fiber concrete was carried out using the above test device, and the results show that the tensile strength of concrete can be clearly improved by adding polypropylene fiber, which makes the tensile failure of concrete show certain plastic characteristics. The test results show that with the increase in fiber content, the tensile strength of concrete increases first and then decreases. The effects of polypropylene fiber content and curing age on the tensile properties of concrete were studied and the optimum polypropylene fiber content was determined. When the fiber content is 0.9 kg/m3, the tensile strength of concrete reaches the maximum value. The splitting tensile test of concrete under the same condition was carried out simultaneously. The damage phenomenon and test results of the axial tensile test and splitting tensile test of concrete were compared and analyzed, and the applicability of the new developed device in the concrete axial tensile test was verified.

Mesoscopic modeling and simulation of tensile properties of cracked concrete using cohesive model

A random aggregate (RA) model consisting of mortar, aggregate, and the interfacial transition zone (ITZ) was established to investigate the effect of existing cracks on the tensile properties of concrete. Based on this, a method for establishing a geometric model of cracked concrete was proposed by inserting 0-depth cohesive elements into the RA model. The influence of crack length, width, and area on the tensile properties of concrete were studied using the established cracked concrete model. In addition, the key parameters of bond strength and fracture energy of the mortar and ITZ regions were tested. The cement is ordinary Portland cement with a strength grade of 42.5, and the sand is medium sand. The fracture energy tests were conducted using a displacement-controlled loading model with a loading rate of 0.4 mm/min, while the tensile strength tests were conducted using a stress-controlled loading method with a loading rate of 0.06 MPa/s. The feasibility and accuracy of the numerical method used were verified by comparing the results with those of a finite compression simulation. The numerical results show that as the crack length increases, the tensile strength and elastic modulus of concrete gradually decrease, but if the crack length is 0.47 h, the elastic modulus of concrete shows an abnormal increase. The range of the crack's influence on the tensile performance of concrete is between 50 mm and 100 mm. If the crack width is less than 0.55 mm, the tensile strength of concrete gradually decreases with the increase of crack width, and when the crack width is greater than 0.55 mm, the tensile strength stabilizes.

Influence of Fibers on Fresh and Mechanical Properties of (FRC) Fiber Reinforced Concrete, A Step Towards Sustainability

Abstract Mostly used material is concrete which has versatile quality for construction works. Fibrous concrete have significant factor that improve the scale and value to concrete for humid environments with significant role. Day by day abundant demand and use of concrete is increasing. It is considered as a 2nd largest building material due to the major productivity. By the use of fibrous concrete, some bonding and environmental issues have been addressed. Keeping in this view, an experimental based study is conducted to evaluate the strength of fiber reinforced concrete at different percentages 0%, 0.5%, 1.0%, 1.5% and 2.0%. All percentages are added by the weight of concrete with all fibers. In this connection, one hundred and fifty-three cylinders of five mixes are prepared. Workability checked of fresh concrete during the pouring of concrete cylinders. Poured cylinders’ samples are left for different curing ages at 7 and 28 days. One hundred and two cylinders for compression at 7 and 28days but fifty-one cylinders for split tensile test at 28days with all fibers i.e. glass fiber, steel fiber, coconut fiber and polypropylene fiber. After curing, compression and split tensile tests are performed to check the strength of hardened concrete. Workability of five mixes lies between 40-90mm.Fibrous concrete is suitable for humid environment where high strength and voids less concrete are required. Addition of fibers in concrete may improves the strength parameters as well as to increase the bonding and tensile properties of concrete. It reduces the quantity of water to be used in concrete. Also the use of different types of fibers has been proved to be economical and is considered as environmental friendly construction material.

Machine learning for strength evaluation of concrete structures – Critical review

Artificial intelligence (AI) in the form of machine learning enables the working framework to get more accurate at interpreting outcomes without being explicitly programmed. Machine learning is described as a collection of techniques and algorithms that are capable of extracting information from data and continually enhancing their capabilities through the process of learning from experience. In Machine learning, Artificial Neural Networks (ANN), Multiple linear regression, support vector machine, and linear regression are widely available. An outline of the benefits of machine learning (ML) in the domain of Civil Engineering is described in this article. The review focused more on the determination of the strength characteristics of concrete through machine learning. Rapid growth in the sophistication of these approaches has had a profound impact on Civil Engineering, particularly in the building and infrastructure industries. In the field of Civil Engineering, Machine Learning plays a significant role in forecasting strength, particularly compressive strength and the physical features of concrete, such as assessment of crack propagation, surface roughness, etc., as opposed to the references. The review shows that machine learning-based strength estimation yields reliable findings in comparison to experimental values. The review explores various machine learning models which are used to estimate concrete properties. The XGBoost produces the best accurate result (85%) with the lowest mean absolute error. The most significant shear strength and compressive strength features, according to an analysis of the relevance of the input parameters, are the ratio of shear span to effective depth, longitudinal reinforcement ratio, concrete strength, and volume percent of fiber. The analysis demonstrated that machine learning may be utilized successfully to determine the compressive and tensile properties of concrete.

Fatigue Factor Assessment and Life Prediction of Concrete Based on Bayesian Regularized BP Neural Network.

Concrete tensile properties usually govern the fatigue cracking of structural components such as bridge decks under repetitive loading. A fatigue life reliability analysis of commonly used ordinary cement concrete is desirable. As fatigue is affected by many interlinked factors whose effect is nonlinear, a unanimous consensus on the quantitative measurement of these factors has not yet been achieved. Benefiting from its unique self-learning ability and strong generalization capability, the Bayesian regularized backpropagation neural network (BR-BPNN) was proposed to predict concrete behavior in tensile fatigue. A total of 432 effective data points were collected from the literature, and an optimal model was determined with various combinations of network parameters. The average relative impact value (ARIV) was constructed to evaluate the correlation between fatigue life and its influencing parameters (maximum stress level Smax, stress ratio R, static strength f, failure probability P). ARIV results were compared with other factor assessment methods (weight equation and multiple linear regression analyses). Using BR-BPNN, S-N curves were obtained for the combinations of R = 0.1, 0.2, 0.5; f = 5, 6, 7 MPa; P = 5%, 50%, 95%. The tensile fatigue results under different testing conditions were finally compared for compatibility. It was concluded that Smax had the most significant negative effect on fatigue life; and the degree of influence of R, P, and f, which positively correlated with fatigue life, decreased successively. ARIV was confirmed as a feasible way to analyze the importance of parameters and could be recommended for future applications. It was found that the predicted logarithmic fatigue life agreed well with the test results and conventional data fitting curves, indicating the reliability of the BR-BPNN model in predicting concrete tensile fatigue behavior. These probabilistic fatigue curves could provide insights into fatigue test program design and fatigue evaluation. Since the overall correlation coefficient between the prediction and experimental results reached 0.99, the experimental results of plain concrete under flexural tension, axial tension, and splitting tension could be combined in future analyses. Besides utilizing the valuable fatigue test data available in the literature, this work provided evidence of the successful application of BR-BPNN on concrete fatigue prediction. Although a more accurate and comprehensive method was derived in the current study, caution should still be exercised when utilizing this method.

The effect of tension stiffening in moment-curvature responses of prestressed concrete members

Although tensile resistance of concrete is often neglected in calculating the nominal flexural capacity of a concrete member, it needs to be taken into account to accurately trace the deformation response of concrete members as it affects pre- and post-cracking behavior. To adequately address tensile resistance contributed by concrete in moment–curvature analysis, it is necessary to exploit a proper concrete tensile stress–strain model. While constitutive stress–strain models of reinforced concrete in tension have been studied by many researchers and well documented, those of prestressed concrete have gained relatively less attention. There are also conflicting results on how prestressing force affects concrete tension stiffening. This study fills the gap in existing studies and suggests an appropriate and simple model capturing the concrete tensile stress–strain relationship of prestressed concrete in a moment–curvature analysis. Based on an inverse-engineering approach using experimental test data and nonlinear analysis results, the effect of concrete tension stiffening varied by the level of prestressing force is investigated. The results show that concrete tensile properties hardly affect the force–deformation response of beams with high-level prestressing. Additionally, several parameters related to concrete tension stiffening are examined in the parameter study. By comparing predicted moment–curvature responses with test data, ideal values for considered parameters are obtained. Based on the parameter study, simple equations are proposed that are expressed in concrete compressive strength to simulate the concrete tensile stress–strain responses of partially prestressed members. The proposed equations are demonstrated using several prestressed beam tests found in previous studies.

Effects of source location on the pozolannic properties of Rice Husk Ash (Rha) and strength properties of concrete

This paper presents the effects of variability in the chemical and elemental composition of Rice Husk Ash (RHA) sourced from four (4) different locations on Tensile Properties of Concrete. RHA is an agricultural waste gotten from rice mills after removal of rice paddy for food and burnt in open air or under controlled processes. RHA is found to be pozzolanic and can be used to partially replace cement to enhance the strength and quality of concrete. The different sources where RHA was gotten are; Ogoja, Abakaliki, Adani and Adikpo in Nigeria. It is discovered that the pozolanic properties of RHA varies based on their source location. Samples from Ogoja where found to have the highest pozzolanic properties followed by Abakaliki, Adani, and Adikpo, their silica content was found to be 84.55, 76.3, 70.12, 70.11, respectively. RHA was used to replace cement in concrete at 5, 10,15,20,25 and 30%. The compressive strength was determined and the values are as follows; And the compressive strength values at 28 days was found to be in the range of 37-42N/mm2 at 5%RHA, 35-39.5N/mm2 at 10%RHA, 30-34.5N/mm2 at 15%RHA, 27-29N/mm2 at 20%RHA, 22-25.6N/mm2 at 25% RHA and 21-24N/mm2 at 30% RHA compared to the controlled sample with a strength value of 42.64N/mm2. Cylindrical columns concrete of size 100mm diameter by 200mm long were moulded and stored in water for 28 days before testing for tensile splitting strength. The values determined from the split tensile test are as follows; 2.1-3.1N/mm2 at 5%RHA, 2.1-2.5N/mm2 at 10% RHA, 1.8-2.10 N/mm2 at 15% RHA, 1.2-1.7 N/mm2 at 20%RHA, 1.1-1.3 N/mm2 at 25% RHA and 0.62-0.9 N/mm2 at 30% RHA while the results of the controlled sample is 3.1 N/mm2.From the results above it can be deduced that source location influences the chemical properties of RHA strength characteristics of the Concrete with RHA as partial replacement.

Study on Tensile Properties and Failure Modes of BFRC

The effects of basalt fiber volume fraction and fiber length on the tensile properties of concrete are studied by experiments. The mechanism of fiber improving the tensile failure mode of concrete is analyzed. The results show that the tensile properties of BFRC are significantly improved compared with the matrix concrete. The initial crack strength and yield strength increase significantly with the increase of fiber volume fraction, while the initial crack strain and yield strain increase significantly with the increase of fiber length. The roughness coefficient of BFRC fracture surface can be used as the index of fiber improving concrete tensile properties.

Study on Tensile Stress-Strain Relationship of BFRC

In this paper, different types of basalt fiber concrete (BFRC) were been researched on the tensile properties. Moreover, analyzed the influence of fiber length and fiber volume fraction on the tensile properties of concrete. The results showed that the tensile strength of BFRC increased significantly with the increase of fiber volume fraction, and the strain increased significantly with the increase of fiber length. The BFRC tensile stress-strain curve shows obvious staged failure, and the function of stress-strain relationship based on the regression method has burning relevance with the test results.

In situ testing of barrette foundations for a high retaining wall in molasse rock

Barrettes are common foundations for high-rise buildings, especially because of their high bearing capacity, for vertical as well as for lateral loads. In this paper, it is shown how these were adopted and tested for anchoring a 27 m high retaining wall in rock on a slope located in the centre of Zurich. The monolithic 10 × 1 × 25 m deep barrettes, excavated and built in layered rock (Upper Freshwater Molasse), are also intended to stabilise the slope. The main contribution to their bearing capacity is given by the contact strength between the reinforced concrete and the rock. Two full-scale pull-out tests, instrumented by distributed fibre-optical measurements, are carried out to investigate the contact strength between rock and reinforced concrete. The results show that dilatancy at the contact caused by the irregular excavated surface has a strong influence on the bearing capacity. Additionally, the distributed fibre-optic instrumentation allowed progressive crack propagation of the reinforced concrete in the barrettes to be detected during the test. Inverse analysis of the rock and concrete tensile properties are obtained within a finite-element calculation, which takes into account the non-linear properties of the reinforced concrete and the rock.

Morphology and Strength of Cement Paste from Clay as Nanomaterial

Now days the application of nanomaterials was vastly growing in the development of new material to improve the quality of human life. Particles of nanomaterials which are in nanoscale helps to improve to the characteristics of the existing micro based materials. The application of nanomaterials in the construction were started since in the early 90s when during those time micro based materials was very demanding especially when dealing with High Performance Concrete (HPC). The utilization of nanobased materials improves and reinforces the cement matrix system and performs early strength and also enhances tensile properties of concrete. In this research, two types of clay were used which nanometakaolin and nanometaclay. nanometakaolin were made from sol gel process thats involved milling technique and nanometaclay were supplied by Sigma Aldrich. The mix proportion for clay based cement paste also includes metakaolin as cement replacement material. nanometakaolin and nanometaclay was added as additives from 0, 1, 3, 5, 7, 9 percent (%) from weight of cement and will be compared to OPC as control specimen. nanometakaolin and nanometaclay inclusion in cement paste will be evaluated for morphology effect by using Scanning Electron Microscope (SEM), chemical composition by using X-Ray Fluorescent (XRF) technique and strength properties. From morphology evaluation, the shape of the particles and particularisation of the matrix observed on the nanometakaolin, nanometaclay and plain cement paste were compared. Similarly, the strength of the plain cement paste shows was compared with those of nanometakaolin and nanometaclay. From the results, shows that inclusion of nanometakaolin at 7% additives generates early strength of cement paste and at 28 days of age addition of 1% of nanometakaolin was found to be the optimum addition level. The addition of 1% nanometakaolin acts as an ultra-filler and refines the microstructure of concrete. Furthermore, nanometakaolin also produces a secondary hydration product by optimizing the remaining calcium hydroxide which was not fully removed during the hydration period.

Tension Stiffening Model for Concrete Beams Reinforced with Steel and FRP Bars

Cracking is an important aspect of concrete behavior that considerably affects the overall response of concrete structures. The initiation of cracks is governed by concrete tensile properties. The propagation of cracks is a complicated phenomenon that plays a significant role in the nonlinear analysis of concrete structures. The cracking process in tension starts at a relatively low tensile strain, causing plain concrete to exhibit a gradual softening behavior. This softening is augmented by the tension stiffening of reinforcing bars. The smeared crack approach is typically combined with nonlinear finite-element analysis to generate an accurate global response. The key to such representative accurate predictions relates to material parameters, especially those of tension stiffening effects. For a complete understanding of the crack development process, tests should be performed on concrete specimens at various load histories. However, due to the difficulty of testing concrete in uniaxial tension, only limited and often conflicting results are available. The present work develops an inverse approach combining nonlinear numerical analysis and global experimental response to develop the tension stiffening model parameters needed to simulate homogenized concrete behavior in tension. The results of the study provide good model parameters to use in the case of concrete beams reinforced with steel and fiber-reinforced polymer (FRP) bars.

Continuum damage mechanics based modeling of fiber reinforced concrete in tension

The tensile properties of concrete can be enhanced substantially by incorporating high strength and small diameter short fibers, which leads to fiber reinforced concrete (FRC). For this reason, FRC has been widely used in infrastructures, where tensile cracks may occur. However, an analytical model for such a material is still lacking. In this article, an attempt was made to model the behavior of FRC, which shows a hardening response in tension, based on the continuum damage mechanics (CDM). In the material, conventional concrete (a cement–sand–coarse-aggregate–water mix) was used as the matrix, and short steel fibers were used as the reinforcement. The quasi-brittleness of the matrix and the fiber–matrix interfacial properties were taken into consideration. Results show that the model-predicted stress–strain curves agree well with those obtained experimentally.