Residual Flexural Tensile Strength Research Articles

Challenges of a Circular Economy: The Example of Raw Recycled Tyre Steel Fibres Added to Concrete.

This research was conducted to analyse the possibility of using raw, untreated recycled tyre fibres as an effective concrete reinforcement according to circular economy principles. The aim of the article was also to develop a method for dispensing tire fibres on a real scale. Additional treatment and homogenisation of recycled steel fibres entail higher energy consumption, emissions of greenhouse gases, and increased costs. However, obtaining durable and safe concrete effectively reinforced with steel fibres is critical. Finding a balance between environmental friendliness and product durability is a circular economic challenge. Reference concrete with commercial steel fibres (15 kg/m3) and two concretes containing various quantities of non-treated, raw tyre recycled fibres (25 kg/m3 and 45 kg/m3) were industrially produced. Tests were carried out on the properties of the concrete mixture and hardened concrete, such as compressive strength, flexural strength, splitting strength, modulus of elasticity, residual flexural tensile strength, and fibre distribution in concrete. Tests revealed that increasing the amount of raw tyre fibres disturbs the structure and causes air entrainment and the formation of fibre clusters. Smaller quantities of raw tyre fibres turn out an effective concrete reinforcement. The use of non-treated tyre fibres as concrete reinforcement is possible but requires more stringent control of the concrete parameters. Implementation tests on an industrial scale are a novelty in this study, presenting an analysis of the possible dispensing of tyre fibres in a ready-mixed concrete production plant and testing the characteristics of manufactured concrete.

Development of an enhanced damage law for typical steel fiber reinforced concrete based on uniaxial compression and tension tests

Understanding the stiffness of a concrete structure is crucial to analyze it, particularly for statically indeterminate structures. Stiffness degradation – commonly referred to as damage – occurs with the onset of cracking or large compressive strains. For most conventional and specialized types of concrete, damage studies and models for predicting damage development are available. However, more information is needed about the damage behavior for the most common steel fiber reinforced concrete in Europe with strength class C30/37 and modern end-anchored high-strength fibers in dosages of 20–40 kg/m3. Therefore, in this study, these common steel fiber concretes were subjected to multiple load cycles in (1) uniaxial compression tests on cylinders and (2) direct tensile tests on bone specimens to investigate their damage behavior. The resulting damage was then compared to known damage laws, but none of the models predicted accurate damage results. Finally, an existing damage law for plain concrete was modified as a function of the residual flexural tensile strength—the relevant parameter for describing the performance of the steel fiber reinforced concrete. Hereby, we were able to decisively improve the agreement between experimental results and the theoretical prognosis by utilizing our modified damage law.

Mechanical properties of polymer fibre reinforced concrete in the light of various standards

The article presents the results of a detailed experimental campaign including a compressive strength test, three- and four-point bending test (3PBT and 4PBT, respectively) of polymer fiber reinforced concrete with the addition of metakaolin. The comprehensive analysis included three Types of concrete mixture differing in amount and used polymer fibers. It was concluded that polymer fibers did not influence the maximum compressive and flexural tensile strength of concrete. On the other hand, they had a beneficial effect on the ductility, residual and equivalent flexural tensile strengths, and fracture energy of samples. The mixtures of Type 1 and 2 were characterized by softening behaviour but the mixture of Type 3 by soft-hardening behaviour. In the 3PBT, the residual flexural tensile strengths obtained according to EN 14651 did not correspond clearly with equivalent flexural tensile strengths calculated in compliance with RILEM TC 162-TDF. It is noteworthy that the effectiveness and correctness of equations presented in other work of the authors referring to dependencies between deflection, crack and tip mouth opening displacements for the 3PBT were confirmed on samples with different composition and fibers. Based on the 4PBT, the equivalent flexural tensile strengths according to JCI-SF4 standard were calculated and the correlations with the results from 3PBT were defined.

Effect of Contents, Tensile Strengths and Aspect Ratios of Hooked-End Steel Fibers (SFs) on Compressive and Flexural Performance of Normal Strength Concrete

This study is a part of the study to simplify the reinforcing details of reinforced concrete (RC) structural members by substituting the conventional reinforcement with hooked-end steel fibers (SFs). This paper investigates the effects of SF strength, dosage and aspect (l/d) ratio on the compressive and flexural behaviors of normal strength concrete with specified compressive strength of 30 MPa. In this study, hooked-end SFs of high strength (2000–2400 MPa) and normal strength (1100–1200 MPa) were used with three l/d ratios of 64, 67 and 80. Hooked-end SFs were incorporated with three dosages of 20 kg/m3 (0.25 vol.%), 40 kg/m3 (0.50 vol.%) and 60 kg/m3 (0.75 vol.%). Eighteen steel fiber reinforced concrete (SFRC) mixes were mixed. To evaluate the compressive and flexural performance of each SFRC mixture, three SFRC cylindrical and prismatic specimens for each mixture were manufactured and tested, respectively. The test results that the inclusion of hooked-end SFs had little effect on the compressive strength, while it improved the toughness of concrete. Hooked-end SFs were also found to be effective in enhancing the flexural performance of concrete. The dosage and properties (strength and l/d ratio) of SFs significantly affect the residual flexural tensile strength (fR1 and fR3) at serviceability (SLS) and ultimate limit state (ULS) defined in fib Model Code 2010 (MC2010).

Effect of notch-to-depth ratio on flexural and fracture behaviors of UHPGC notched beams based on four-point bending test and acoustic emission

An ecological ultra-high-performance glass sand concrete (UHPGC) was prepared by partially replacing quartz sand in traditional ultra-high-performance concrete (UHPC) with glass sand recycled from waste glass. The four-point bending tests of UHPGC notched beams with different notch-depth ratios (0.2, 0.3, 0.4, and 0.5) were carried out, while acoustic emission (AE) monitoring was employed at the whole fracture process. Flexural toughness and residual flexural tensile strength were used to evaluate the flexural properties. Meanwhile, fracture energy and fracture toughness were used to evaluate the fracture properties. The results reveal that notch-depth ratio exhibits a significant effect on the flexural and fracture performances of UHPGC notched beams. The residual flexural tensile strength, flexural toughness, fracture energy and fracture toughness decrease with the increase of notch depth. Moreover, AE energy parameters can favorably characterize the differences of energy release in the fracture processes of UHPGC beams with different notch depths, and favorable correlations are observed between cumulative AE energy and fracture energy. Besides, AE wavelet entropy are constructed based on wavelet packet transform (WPT) of AE waveforms, and the evolution model of wavelet entropy is established. By comparing with the evolution process of AE energy information entropy, it is proved that the maximum point of wavelet entropy can be used as the key point to predict the peak load.

Residual flexural tensile strength properties of notched concrete beams with high-strength steel fibers

The purpose of this study is to replace the steel bars and barbed wires in reinforced concrete structures, conduct experiments using steel fiber-reinforced concrete (SFRC), and investigate its failure modes. We conduct the experiments by performing the three-point bending test specified in the EN 14651 standard. Based on an analysis of the results obtained worldwide in recent years, we use SFRC specimens fabricated in the structural laboratory of Chungnam University in South Korea and apply the results from other researchers. The residual stresses of 625 SFRC specimens are analyzed based on the high or low strengths of the fibers and categorized according to fiber content and the aspect ratio of the fibers. The contribution of each condition to the residual flexural strength is discussed based on the results of the residual flexural strength after cracking, and it is suggested that more research and calculations are needed for high-strength steel fibers.

Behaviour of single bonded anchors in uncracked steel fibre reinforced concrete under tensile loading – Experimental investigations and analytical model

This paper investigates the behaviour of single bonded anchors in uncracked steel fibre reinforced concrete (SFRC) undergoing concrete cone breakout failure under tension loads. Experimental investigations are carried out on bonded anchors installed in SFRC under tension loads while varying different parameters, namely, concrete grade, fibre content, embedment depth, vicinity to none and one or two edges. In addition to the unconfined tests resulting in concrete cone failure of anchors, confined tests are also carried out to verify the equivalent performance of bonded anchors in normal concrete and SFRC. The test results are evaluated for the influence of individual parameters on the enhancement of concrete breakout capacity of anchors. The tests performed on the anchors in SFRC show that the enhancement of the performance of the anchors due to SFRC depends on the steel fibre amount, embedment depth as well as their position (away or near to the free edge). Based on the detailed evaluation of the test results, a new analytical model for predicting the concrete cone capacity of anchors in SFRC is proposed. The analytical model proposed is an extension of the concrete capacity design (CCD) method used for the design of anchors in normal concrete and considers the different parameters listed above to determine the concrete cone capacity of the anchors in SFRC. An alternate equation relating the concrete capacity of anchors in SFRC with the mechanical properties commonly used to characterize SFRC (residual flexural tensile strength) is also proposed. When compared with the test results the proposed equation results in average value of the test to calculated failure loads as 1.0 and a CoV of 11.7%.

Experimental investigation on the flexural performance and damage process of steel fiber reinforced recycled coarse aggregate concrete

The application of recycled concrete requires the reliable information on its flexural performance especially after cracking. In this study, the three-point bending tests were carried out on 40 notched beam specimens to investigate the flexural performance and damage process of steel fiber reinforced recycled coarse aggregate concrete (SFRCAC). The effects of water-cement ratio, recycled coarse aggregate replacement ratio and steel fiber volume fraction on the residual flexural tensile strength and flexural toughness of SFRCAC were analyzed. Moreover, the flexural damage process of the SFRCAC notched beam was explored and analyzed by Acoustic Emission (AE) technology. The results show that the residual flexural tensile strength and flexural toughness of SFRCAC decrease with increased water-cement ratio and recycled coarse aggregate replacement ratio, respectively. Adding steel fibers can effectively improve the residual flexural tensile strength and flexural toughness of SFRCAC. The post-cracking behavior of SFRCAC changes from strain-softening to strain-hardening when steel fiber volume fraction increases from 0.5% to 2%. Finally, the empirical formula of residual flexural tensile strength for SFRCAC has been put forward by analyzing and fitting the test results in this study and related literature.

2,000 MPa급 고강도 후크형 강섬유로 보강된 60 MPa급 콘크리트의 잔류 휨 인장강도

본 연구는 고강도 강섬유를 이용하여 전통적인 철근이나 망사를 대체하여 콘크리트구조를 단순화하려고 강섬유 보강콘크리트의 기계적 특성을 기반으로 하는 구성 모델을 연구하려고 한다. 특히, 휨 분석과 설계에 필요한 휨 인장응력 모델은 잔류 휨 인장강도의 영향을 크게 받는다. 본 논문에서는 2,000 MPa 고강도 후크형 강섬유로 보강된 27개의 노치 고강도 콘크리트 보에 대한 3점 휨 실험을 진행하고 논의하였다. 본 실험에선, 고강도 콘크리트에 형상비(lSUBf/SUB/dSUBf/SUB)가 64 및 67, 80의 섬유 세 타입을 사용하였으며, 변수로는 체적비 0.25 %(20 kg/㎥), 및 0.5 %(40 kg/㎥), 0.75 %(60 kg/㎥) 를 선정하였다. 본 실험 결과와 타 연구자들 문헌을 통해서 수집한 결과를 분석하여 사용 한계 상태(SLS) 및 극한 한계 상태(ULS)에서 HSFRC의 잔류 휨 인장강도에 대한 콘크리트 및 강섬유의 특성의 영향을 조사하였다.

Influence of macro-synthetic fiber on the mechanical properties of iron ore tailing concrete

Iron ore tailing (IOT) is a hazardous by-product of iron extraction, and its disposal has resulted in serious environmental issues. This paper investigated the interfacial bond performance of macro-synthetic fiber (MSF). The effect of the IOT replacement ratio on the compressive performance of concrete and the effects of MSF on the compressive and flexural performance of IOT concrete were evaluated. Test parameters included IOT replacement ratio (0%, 50% and 100%), fiber volume fraction (0%, 0.5%, 1.0%, 1.5% and 2%) and fiber aspect ratio (43, 60 and 69). The test results indicated that the deterioration in compressive strength was observed with the increase in the IOT replacement ratio. The mechanism of the effect of IOT on the compressive performance of concrete was analyzed. However, the incorporation of MSF compensated for the reduction in compressive strength caused by iron ore tailings (IOTs). Furthermore, the post-cracking performance, which includes residual flexural tensile strength, equivalent flexural tensile strength and fracture energy, of concrete increased with the increase in fiber volume fraction. The fracture energy of IOT concrete increased by a factor of 18.06–20.19, and the post-cracking performance of IOT concrete was comparable with that of natural sand (NS) concrete at an MSF fiber volume fraction of 2%. At a given fiber volume fraction, the MSF with a higher fiber aspect ratio was more effective in improving post-cracking performance than one with a lower aspect ratio. Moreover, new empirical equations were proposed, which can accurately predict the residual flexural tensile strengths and equivalent flexural tensile strengths. These results provide important implications for determining the contribution of MSF in strengthening and toughening IOT concrete.

Residual flexural tensile strength of normal-weight and lightweight steel fibre-reinforced concrete at elevated temperatures

In this study, the residual flexural tensile strength (fR,j) of steel fibre reinforced concrete (SFRC) at elevated temperature was investigated through a detailed test program. Sixty pre-notched SFRC prism specimens, cast with both normal-weight and lightweight concrete with different fibre contents, were heated inside a furnace to temperature ranging from 200 °C to 800 °C. The uniformly heated specimens were then subject to three-point bending using a carefully configurated test setup, to evaluate the residual flexural tensile strengths at elevated temperatures. The specimens were also tested at ambient temperature for benchmark comparison. A drop in both the residual flexural tensile strengths and the stiffness of SFRC was observed with the increase of temperature. The flexural tensile strength retention plotted against the elevated temperature exhibited a bilinear relationship. Based on the experimental results, a piecewise linear regression analysis was carried out to propose empirical equations to predict the residual flexural tensile strength of SFRC at elevated temperatures. The proposed equations were able to predict the strength retention factors with an average accuracy of around 98 % and a standard deviation of 18 % on average. The results from this study form the basis for predicting the behaviour of SFRC structural members under fire conditions.

Durability Performance of PVA Fiber Cement-Stabilized Macadam

To further improve the durability of cement-stabilized macadam and guarantee the use quality and sustainability of a semi-rigid base, the current study was carried out. With the help of a dry shrinkage test, temperature shrinkage test, freeze–thaw bending test, and fatigue test, the effect of incorporating PVA fiber on the deformation characteristics of cement-stabilized macadam was analyzed, and the changes in low-temperature residual toughness of the mixture before and after modification were compared. The low-temperature toughness of PVA fiber cement-stabilized macadam was evaluated with the help of the standard toughness evaluation method. The fatigue life prediction equation of PVA fiber cement-stabilized macadam was established based on the Weibull distribution. The results showed that PVA fiber can effectively improve the deformation characteristics, low-temperature toughness, and fatigue performance of cement-stabilized macadam. The low-temperature residual flexural tensile strength and low-temperature bearing capacity were increased by 10.3% and 55.3%, respectively. The residual toughness indices were increased by 58.6%, 88.1%, and 98.3% and the residual strength index was increased by more than 100%. The fatigue life was improved by 178~368% under different stress intensity ratios. The fatigue life values obeyed the two-parameter Weibull distribution, and the correlation between the fatigue life prediction equation and the measured data was significant. The fatigue life prediction error was between 0.03 and 4.9% under different stress intensity ratios.

An Explorative Study into the Influence of Different Fibers on the Spalling Resistance and Mechanical Properties of Self-Compacting Concrete after Exposure to Elevated Temperatures

This study aims to explore the impact of different fibers on the explosive spalling resistance, residual compressive strength, residual flexural tensile strength, and mass loss of self-compacting concrete (SCC) after heating to elevated temperatures. The fiber types, fiber contents, and target temperatures are selected as the tested variables. Steel fibers (SF), polypropylene fibers (PF), and their combination are used to improve the fire resistance of SCC. Then, the specimens are tested after exposure to different target temperatures varying from 200 °C to 1000 °C and cooling down to room temperature naturally. The obtained results reveal that PF can effectively prevent explosive spalling in the SCC. Moreover, it was found that the temperature of 400 °C is a critical temperature for the residual compressive strength of fiber-reinforced SCC. Regarding the flexural tensile strength, the temperature of 200 °C was found to be a changing point of the SCC after heating to elevated temperatures. A sharp decrease in the compressive strength is observed when the target temperature exceeds 400 °C. For temperatures below 400 °C, the compressive strength is enhanced slightly with the increase of the target temperature. Moreover, incorporating a fiber cocktail is an effective way to improve the explosive spalling resistance and residual mechanical properties in the case of fire. Finally, the regression analysis was performed and the proposed correlations between the residual strengths and elevated temperatures are compared with equations in the literature. Good accuracy of the proposed correlation is achieved for fiber-reinforced SCC.

Flexural Tensile Behavior of Single and Novel Multiple Hooked-End Steel Fiber–Reinforced Notched Concrete Beams

Novel multiple hooked-end steel fibers possessing high anchorage with the concrete matrix have been invented and are desired to achieve significant improvement in the performance of steel fiber–reinforced concrete (SFRC). In this study, C50/C70/C80 notched concrete beams containing 4D steel fibers with 1.5 hooked ends at a dosage of 0–110 kg/m3, 5D fibers with double hook-ends at a dosage of 0–110 kg/m3, and 3D steel fibers with a single hooked end at a dosage of 0–70 kg/m3 were tested under three-point bending. The experimental results indicated that increasing fiber dosage and the number of hooked ends were generally effective in improving the flexural tensile behavior of concrete beams, especially high-strength concrete beams. The two linear relationships of the equivalent flexural tensile strength feq,2 and feq,3, evaluated by RILEM TC 162-TDF, as well as the residual flexural tensile strength fr,1 and fr,4, evaluated by BS EN 14651, were confirmed to be appropriate for concrete beams reinforced by 3D, 4D, and 5D steel fibers. Based on the experimental results from this study and more in the literature, the analytical equation, proposed by Naaman et al. and simplified by Pajak et al., was verified to be reliable for predicting the maximum flexural tensile strength for concrete beams reinforced by 3D, 4D, and 5D steel fibers. Furthermore, the analytical equation, proposed by Venkateshwaran et al., that can explicitly take into account the effects of concrete compressive strength, fiber volume fraction, fiber aspect ratio, fiber length, and number of fiber hook ends, was modified for predicting the residual flexural tensile strength (fr,i) of novel multiple hooked-end SFRC. It was found that the modified Venkateshwaran et al. equation was approved as valid for high-strength SFRCs in this study, whereas the original one only applies for low-strength and normal-strength SFRCs. All these represent a step forward in advancement on the knowledge and understanding of SFRC with novel multiple hooked-end steel fibers.

Effectiveness of Concrete Reinforcement with Recycled Tyre Steel Fibres.

The role of searching for industrial waste management solutions in construction is key for environmental protection. Research in recent years has focused on solutions aimed at reducing the carbon footprint. This paper presents the results of tests conducted on concrete reinforced with treated recycled tyre steel fibres (RTSFs) compared to the same amount of manufactured steel fibres (MSFs). The effectiveness of concrete reinforcement with RTSFs was analysed using the fracture mechanics parameters of cementitious composites. Rheological tests, residual flexural tensile strength tests, work of fracture measurements, toughness indices, examinations of the fibre distribution in the concrete, and SEM observations of the concrete fractures with fibres were performed. Determining the work of fracture and toughness indices was an innovative aspect of this paper. As the amount of RTSFs increased, a decrease in the consistency was observed, although the distribution of fibres in the concrete was uniform, as proven by the results of computer tomography tests. Concrete reinforced with RTSFs that is purified and refined during the recycling process might have better properties than concrete reinforced with the same amount of MSFs. The application of RTSFs in construction has environmental and economic benefits in addition to the strengthening of cementitious composites.

Empirical approach for the residual flexural tensile strength of steel fiber‐reinforced concrete based on notched three‐point bending tests

AbstractWhen designing steel fiber‐reinforced concrete, for example, according to Model Code 2010, the residual flexural strength values must be specified as fundamental properties. It is often difficult to establish the relationship between residual flexural strength values and the required dosage of steel fibers depending on the type of steel fibers and the concrete quality. For an estimation of the presumably necessary dosage of steel fibers, various empirical approaches exist for the approximate determination of the residual flexural strength values, which, however, are based on different tests and have been almost exclusively been derived on the basis of few or “own” test results of the respective institute. For this reason, the validity of the respective approximation approach is often limited. Using the bending beam database “Steel Fibre Reinforced Concrete”, selected approaches were systematically analyzed and an improved approach for determining the residual flexural strength values of steel fiber‐reinforced concrete was developed.

Mechanical properties and self-sensing ability of amorphous metallic fiber-reinforced concrete

The aim of this research work is to develop a corrosion resistant fiber-reinforced concrete for radioactive waste disposal structures. In the case of precast concrete, the use of fibers is a solution to reduce the amount of steel reinforcement while maintaining high mechanical performance and durability. Concrete has a low strain capacity and a limited tensile strength. Generally, reinforcing bars are used to ensure tensile strength. A fiber reinforcement can also help to overcome such a mechanical weakness. For this purpose, an amorphous metallic fiber (AMF), corrosion-resistant and suitable for application in severe environment conditions are used. The fresh and hardened properties of the self-compacting fiber reinforced concrete (SCFRC) are studied with volume fractions of AMF of 0% and 0.28% and with three different aspect ratios (82, 114 and 123). Flexural tensile tests according to European standard EN 14651 are conducted to quantify the contribution of the fiber reinforcement on the residual flexural tensile strength. Since these fibers are electrically conductive, they are also tested to design a smart concrete. For this purpose, electrical resistance of specimens submitted to cyclic flexural loadings are monitored using a Wheatstone bridge.

Study on mechanical properties of macro‐synthetic fiber‐reinforced iron ore tailings concrete

AbstractMacro‐synthetic fiber‐reinforced iron ore tailings (IOT) concrete is an environment‐friendly building material featured by recycling IOT and improving performance of IOT concrete due to fiber incorporation. In this study, the mechanical properties of macro‐synthetic fiber‐reinforced concrete incorporating IOT were investigated. Two different replacement ratios of IOT (i.e., 0% and 50%) and six types of macro‐synthetic fibers at 1.0 vol% were adopted to investigate the effects of IOT, aspect ratio, elastic modulus, and tensile strength of macro‐synthetic fibers on mechanical properties of concrete. The results indicate that the concrete with IOT for natural sand (NS) replacement in 50 wt% demonstrates no loss in compressive strength and a minor loss of 7.67% in fracture energy, but the incorporation of IOT lowers splitting tensile strength and limit of proportionality, especially the splitting tensile strength with a decrease of 18.50%. The splitting tensile strength, equivalent flexural tensile strength, residual flexural tensile strength, and fracture energy were notably improved by adding macro‐synthetic fibers. Experimental results using Tukey test and Student's t test demonstrated that the fiber aspect ratio was more effective in improving equivalent flexural tensile strength, residual flexural tensile strength, and fracture energy than the elastic modulus and tensile strength of fibers, and the residual flexural tensile strength fR,4 was enhanced by 146.34% when increasing the fiber aspect ratio from 36 to 60.

Experimental investigations on the shear bearing behavior of prestressed ultra‐high performance fiber‐reinforced concrete beams with compact cross‐section

AbstractFor ultra‐high performance fiber‐reinforced concrete (UHPFRC) beams subjected to shear the bearing mechanisms differ significantly depending on the type of cross‐section. For I‐shaped cross‐section, existing models superimposing the contribution of concrete, prestressing, stirrups, and fibers were found to predict the shear bearing capacity appropriately. These models may, however, not be generally applicable. The aim of the present study is to investigate the shear bearing mechanisms for UHPFRC beams with compact cross‐section and, in particular, the influences of fiber volume fraction and prestressing on the development of the critical shear crack and the shear bearing capacity. This paper presents the experimental results of 22 three‐point test on 11 beams with varying fiber volume fraction and prestressing. It was found that increasing the fiber volume fraction increases the shear bearing capacity, but however, the benefit was less than proportional to the residual flexural tensile strength of UHPFRC. As expected, prestressing also affects the bearing capacity favorably.

Experimental and theoretical investigation on the stress transfer across cracks due to combined action of steel fibers and aggregate interlock

One of the steps to achieve a rational approach to the shear strength of reinforced concrete members is to understand the force transfer mechanisms throughout the critical crack. This subject has been investigated for decades, but its full comprehension has not been achieved, especially in steel fiber reinforced concrete (SFRC). In the present work, an experimental/theoretical investigation on the combined action of fiber bridging and aggregate interlock was carried out. The experimental program included 12 push-off specimens in which the variables were the fiber volume content (Vf) and aspect ratio (lf/df). The results showed an increase in shear strength and an improvement in the post-cracking stage as residual flexural tensile strength (fR) and Vflf/df increased. To gather information about the failure surface topography, 3D digital image correlation analysis was adopted for specimens without fibers. A contact density-based mechanical model is applied to plain concrete results to derive aggregate interlock parameters and, then, an extended model including fibers is proposed to evaluate the results for SFRC specimens. A reasonable agreement was achieved and the contribution of each mechanism could be estimated.