Use Of Engineered Cementitious Composites Research Articles

Experimental and analytical study on steel-concrete-ECC composite frames with URSP-S connectors

To improve the slab crack resistance in the hogging moment region of steel-concrete composite frames, this paper proposes using Engineered Cementitious Composite (ECC) and Uplift-Restricted and Slip-Permitted Screw-type (URSP-S) connectors near the columns of the frames, the structural behavior of the innovative steel-concrete-ECC composite frames were experimentally and numerically investigated. Firstly, five 1/2-scaled steel-concrete composite frames were experimentally studied under vertical uniform slab loading and horizontal low cyclic loading. The failure mode and cracking, load-displacement relationship, stiffness and strength degradation, energy dissipating, and strain of composite frames with ECC and URSP-S connectors were analyzed, and good cooperative behavior and overall seismic performance were found. Then, it was compared with the results of the other four specimens with different slab materials and shear connector types. The experimental results showed that the use of ECC and URSP-S connectors improved slab crack resistance 55% in terms of crack width, and rarely influenced the structural performance of the composite frames. ECC played a major role in controlling the crack width while URSP-S connector played a major role in controlling the crack number. In addition, based on the test specimen with ECC and URSP-S connectors, an elaborate finite element (FE) model was developed and validated by the test results in terms of cyclic curves and failure mode. Moreover, supplementary modeling analyses with various parameters on the influence of the frame capacity were performed, where steel beam height was the most influential parameter.

Structural behaviour of RC-ECC beam-column connections under quasi-static loading

This research investigates the quasi-static cyclic behaviour of a special moment-resisting frame (SMRF) structure with the application of engineered cementitious composites (ECC) in the beam-column joint. For this purpose, three full-scale beam-column connections were cast and tested under quasi-static loading conditions. The control specimen was cast with the conventional concrete having 21 MPa compressive strength and detailed as per special moment resisting frame (SMRF) requirement. On the contrary, transverse reinforcement was removed from the remaining two (02) specimens with ECC replacing concrete in the joint region and the interface portion of the beam-column connection. Strain gauges and LVDTs were installed at appropriate locations to record the connection's response. After the careful acquisition of data, hysteresis loops, load-displacement envelop and energy dissipation curves were obtained. The test results demonstrated that models with ECC in the joint outperformed the control specimen in ductility, load-carrying capacity and energy dissipation. As compared to the control specimen, the use of ECC in beam-column connection increased the peak displacements by 28.44 %, peak load carrying capacity by 27.13 % and energy dissipation by 58.06 %. Due to high shear strength and ductility, the use of ECC in the joint region was found to address the shear stress requirements without using any transverse reinforcement.

Effect of using Engineered Cementitious Composites (ECC) on failure behavior of flat slab-column connections

Load capacity and ductility are two key characteristics of the flat slab-column connection in high seismic areas. This study specifically examined the effect of strengthening layer thickness of Engineered Cementitious Composites (ECC) on punching shear strength and post punching behavior of flat slabs. The effect of the unbalanced moment, ECC thickness of the slab and the strengthening ECC layer on flat slab punching and post punching behavior were also investigated. Thirteen reinforced concrete flat slab specimens were made and examined. It was observed that the replacement of slab concrete with ECC increased the punching capacity and improved post-punching behavior without a large and sudden drop in load. In addition, the use of ECC as a strengthening layer for the flat slabs significantly increased the punching and post-punching shear strength capacities. The change in failure mechanism was observed from a sudden and abrupt failure to a ductile failure with high-energy absorption when more ECC layer thicknesses were used.

Local use of ECC to simultaneously enhance the shear strength and deformability of RC beams

• A new method that can simultaneously enhance the shear strength and deformability of RC beams was proposed. • The effects of compression-zone material on the variation of V c and v s were evaluated. • Shear deflection and flexural deflection were decoupled. • The mechanisms of how compression-zone material affects the shear strength and deformability were investigated. Existing studies have substantiated that the stress (or strain) states of compression-zone concrete exert significant influence on the performance of shear-critical reinforced concrete (RC) beams. Based on this understanding, the current paper presents a tentative work by replacing the compression-zone concrete with engineered cementitious composite (ECC) to simultaneously enhance the shear strength and deformability of a RC beam. To uncover the reasons behind the enhancements due to the inclusion of ECC, the shear strength contributions from concrete ( V c ) and stirrups ( V s ) were obtained with reasonable accuracy using an innovative methodology. Shear and flexural deformations were decoupled utilizing two methods with the help of the imaging technique. The cracking process, crack width, strain fields, and principal direction evolutions were monitored by a digital image correlation (DIC) system. The test results clearly show that the inclusion of ECC in the compression zone significantly increased both the shear strength and deformability of RC beams. More specifically, the inclusion of ECC changed the crack width and pattern, the variation trends of V c and v s and the deformation proportion. Finally, existing shear deformation models were evaluated, and none of them could predict the shear deformation of beams incorporating ECC due to the high nonlinear feature.

Experimental and numerical investigations of the effectiveness of engineered cementitious composites and stainless steel plates in shear strengthening of reinforced concrete beams

AbstractThis paper investigates the shear strengthening of reinforced concrete (RC) beams incorporating engineered cementitious composite (ECC) and stainless steel plates (SSPs). The use of ECC, characterized by strain‐hardening in conjunction with SSPs, was investigated in this study to improve the shear performance of RC beams. Total 10 RC beams were tested under static loading up to failure to investigate a few key parameters, namely: material of strengthening (ECC and SSPs), the thickness of ECC, and shape and configuration of SSPs. Experimental findings showed that the proposed strengthening methods can significantly improve the failure pattern and increase the ultimate shear capacity of the studied RC beams by 36%–97% compared to the unstrengthened beam. Experimental results were compared against the predicted ultimate shear strength of RC beams using design equations specified by various design codes. Nonlinear three‐dimensional finite element modeling was developed for beams strengthened with ECC layer and validated against the test results and found to be accurate. Based on the experimental and numerical results, new shear capacity formulae were proposed considering the ratio of ECC‐to‐concrete beam cross‐section (ρECC) and then verified against the numerical predictions.

Experimental and Numerical Investigation of Different Types of Jacketing Effect on Retrofitting RC Short Columns Using ECC Concrete

Given the deterioration of civil infrastructure throughout the world, developing more efficient repair and strengthening is essential. Jacketing is one of the most common methods for retrofitting reinforced concrete (RC) columns. Notably, using engineered cementitious composite (ECC) within the jacketing area increases the bearing capacity and significantly enhances the ductility of the columns. The recent development of ECC concrete with suitable compressive strength and higher ductility of about 5 % can significantly enhance the performance of reinforced concrete structures. The behavior of retrofitted RC columns depends heavily on the cohesion between the jacket and the original column as well as the mechanical properties of the jacketing materials. This study investigates jacketed square and circular RC columns using ECC and conventional/normal concrete (NC) using different casing techniques to retrofit RC columns, namely galvanized mesh, U and L-shape joints, removing the cover, core drilling, and integrated models. All specimens were subjected to a compression test. The results indicate that in both square and circular specimens, the use of ECC as a super ductile material and vertical U-shaped elements to connect the longitudinal rebars of the casing and the core leads to much higher ductility and bearing capacity than in NC specimens. These elements also showed suitable ductility because of using ECC as a super ductile material. In order to optimize these methods, finite element analysis (FEA) was conducted using Abaqus software to verify experimental models, as well as a parametric study to achieve an optimum design of the jacketing.

Dynamic response of cylindrical water storage tanks made byECC compared to normal concrete

In this paper, the dynamic behaviour and seismic damages of concrete cylindrical water storage tanks are investigated. Furthermore, by modeling the reservoirs, using normal concrete and engineered cementitious composite (ECC), the effects of ECC on reducing the seismic damages of reservoirs are investigated. For this purpose, ANSYS software is used to perform the nonlinear dynamic analysis of the tanks and different parameters including the hoop force and bending moment of the wall and cracking or crushing of the concrete were examined. According to the results, the relationships and criteria provided in the ACI standard for design of tanks are recommended to be revised in certain parts. Unlike the normal concrete tanks, in those made of ECC, concrete fracture is not observed and the crack width remains very small at a level that is not problematic. Finally, the use of ECC in cylindrical water storage tanks is suggested as a strategy for reducing the seismic vulnerability of this type of hydraulic structures.

The effect of styrene-butadiene rubber and ethylene vinyl acetate polymers on the mechanical properties of Engineered Cementitious Composites

Nowadays, the application of the Engineered Cementitious Composites (ECC) is increasing. An alternative way to use un-oiled fibers in ECC is the coating fibers with hydrophobic oil. Coating of fibers with hydrophobic oil in high volumes of concrete is not practical and is almost impossible. In this study, to increase the mechanical properties of ECC with the use of unoiled fibers, the polymers of styrene butadiene rubber (SBR) and ethylene vinyl acetate (EVA) were used. The cement was replaced by the polymers in order to strengthen the tensile and flexural properties. In sum, 7 mix proportions were prepared for the intended tests. The ECC for compressive strength, the uniaxial tensile and three-point bending were examined and tested. The results of the present research indicated that the use of polymers boosts the tensile and flexural properties of the ECC with unoiled fibers. The tensile strain in this study increased by more than 3% after the application of the polymers. Furthermore, the compressive strength increased by more than 47 MPa, and the deflection at the mid-span reached more than 9 mm in the bending test. On the other hand, these results also proved that the SBR latex is more compatible with the use of ECC in comparison of EVA powder.

Finite Element Analysis on Reinforced Concrete Columns Strengthened by ECC Jacketing under Eccentric Compressive Load

Engineered cementitious composite (ECC) can be used for strengthening of concrete columns due to its similar structure and suitable connection to normal concrete and its special tension behavior. In this study, to analyse the columns, finite element (FE) method was used after verification by experimental results. Reference column was strengthened by normal concrete and ECC jacketing. The effects of type of jacket material, longitudinal reinforcement, compressive stress and ultimate tensile strain of ECC on variations of eccentric load-bending moment (P-M) interaction curves were investigated. Results showed that the use of ECC instead of normal concrete can increase load carrying capacity of strengthened column, due to tensile strain hardening behavior of this material. It was found that, amount of this increase depends on eccentricity of eccentric load and varying from 0.4-23%. In ECC jacketing, tensile cracks are continuous, but in concrete jacketing, there were discrete cracks and more quantity of damages. Due to higher load carrying capacity and better distribution of tensile cracks in ECC jacketing than normal concrete jacketing, the use of ECC is suitable for strengthening of reinforced concrete columns. Load carrying capacity of columns under concentric load and pure bending moment were calculated by theoretical method and the results were compared with FE.

Mechanical behaviour of ECC ring beam connections under square local compressive loading

To reduce the damage degree and ensure the connection zone have a sufficient local compressive strength for safely transferring the axial load from the concrete filled steel tube (CFST) column, a novel through-beam engineered cementitious composite (ECC) ring beam connection is proposed. To investigate the local compressive behaviour of the ECC ring beam connections, fifteen ring beam connections with different matrix types, width factors, height-to-width ratios and reinforcement ratios were tested under square local loading. According to the test results, the ECC ring beam connections showed higher load carrying capacity and ductility than the reinforced concrete (RC) ring beam connections. It was found that decreasing the height-to-width ratio and increasing the reinforcement ratio evidently improved the peak load of ECC ring beam connections. Test results also showed that increasing the width factor resulted in a significant increase in the displacement ductility for connections with a large height-to-width ratio. The height-to-width ratio showed a positive influence on the ductility for connections with a large width factor. Additionally, increasing reinforcement ratio could significantly increase the ductility. These test results point to the great potential of the use of ECC in the ring beam connections where the connection will be subjected to large axial load.

Enhancing the Ductility of a Reinforced Concrete Beam using Engineered Cementitious Composite

A series of small-scale rectangular reinforced concrete beams made with different mix proportions were presented. The beams were fabricated using normal concrete designated as specimen control (NC), normal concrete blended with supplementary material using Class F fly ash (SMFA), and engineered cementitious composite (ECC). The beams comprised of similar reinforcement where the ratio of compression, tension, and transverse bars were 1.0%, 1.5%, and 1.0% respectively. To this end, the beams were tested under four-point bending and they were intended to fail in flexure mode. The tests also aimed to provide direct evidence regarding the improvement of beam ductility due to the use of ECC. Furthermore, the performance of test beams on the overall strength, crack pattern, and damage state was also assessed. To corroborate the experimental work, an analytical work employing nonlinear finite element analysis using Abaqus was also included. From this study, it was found that each beam demonstrated a discernible ductile plateau upon the post-cracking region with Beam ECC showing the largest ductility compared to the other two thereby suggesting that the use of ECC could enhance the beam ductility. It was also shown that the flexural cracks manifested in Beam ECC were less critical, signifying that ECC is a damage-tolerant composite. Furthermore, the overall results of predicted load-deflection and damage state obtained from Abaqus were also in a good agreement with the experimental results.

Ductility enhancement of reinforced concrete beam using Engineered Cementitious Composites in the tension zone

In this study, the optimum flexural properties (viz., ductility and crack arresting mechanism) of Engineered Cementitious Composites (ECC) in the tension zone (1/3 of depth) along with conventional M25 grade concrete in the compression zone (2/3 of depth) of beam is investigated. Polyvinyl alcohol (PVA) fibres and Polypropylene (PP) fibres are used separately in two different ECC mixes. A comparative analysis on flexural strength, deflection, ductility and strain along the depth are carried out for control, PVA-ECC and PP-ECC composite beams. From the flexure studies, it is found that the ultimate load carrying capacity of PVA-ECC fibre composite beam is 16.7% more than control beam and 3.63% more than the PP-ECC fibre composite beam. Deflection of PVA-ECC fibre composite beam is found to be 40.3% and 12.5% less than control beam and PP fibre composite beam respectively, in addition, the stiffness of the PVA-ECC composite beams in the pre-cracking stage is observed to be slightly lesser compared to control and PP-ECC fibre composite beam. From the studies, it is clear that the use of ECC in the cover region, improved the flexural behaviour and ductility by avoiding brittle crack failure. The PVA-ECC fibre based composite beam performed relatively better than PP-ECC fibre based composite beam with respect to strength aspect.

Skid resistance and surface water drainage performance of engineered cementitious composites for pavement applications

Engineered Cementitious Composite (ECC) is a unique class of the high performance fiber-reinforced cement-based material showing extreme tensile ductility of several percent. Few studies have reported potential use of ECC for rigid pavement applications. The critical shortcoming of ECC for roadway application is on the surface texture. ECC lacks coarse aggregates, which leads to low skid resistance and surface drainage. In this study, corundum is first incorporated as fine aggregates into ECC mix (ECC-Cor) to improve the surface micro-texture. The resulting ECC-Cor possesses satisfactory mechanical performance and high skid resistance (BPN > 70). ECC-Cor also shows good durability and the micro-textures can last for more than 100,000 load cycles. While the addition of corundum significantly enhances the micro-texture and skid resistance, improvement on macro-texture and surface drainage is marginal. Further surface treatment with grooves successfully improves the functional performance, not only by minimizing the risk of hydroplaning (water outflow time < 4 s) but also by improving the skid resistance (BPN > 90). An empirical model, which correlates water drainage to macro-texture and pavement geometries of ECC, is proposed.

Buckling Behavior of ECC Column Reinforced With Steel Bar

Engineered cementitious composite (ECC) is a type of high performance fiber reinforced concrete (FRC) with some good strain hardening behavior. This study deals with use of two different fibers, polyvinyl alcohol (PVA) and polypropylene (PP) fiber.PVA fiber is better than PP in terms of mechanical property. A total of 5 columns are prepared, one each of ECC with PVA fiber PVA(R/ECC), ECC with PP fiber PP(R/ECC), and one reinforced cement concrete (RC) column for comparisons. Rest of the two column deals with effective use of ECC in tension zone of the column PVA(R/ECC-RC) and PP(R/ECC-RC) i.e.in the top and the bottom (L/4) region, ECC is used and the centre (L/2) region is filled with RC. Same longitudinal reinforcement ratio was adopted for all the columns and columns were tested under eccentric compression. Due to eccentric compression RC column went through scaling and spalling process while this was not found in ECC columns due to fiber binding effect with cementitious material .Further more columns were analysed using finite element software ABAQUS to plot, Load versus Deformation curve, yielding pattern and stress distribution in the column .

Repair of fire-damaged RC slabs with basalt fabric-reinforced shotcrete

In this paper, an innovative basalt fabric-reinforced shotcrete system is proposed for the flexural strengthening of fire-damaged RC slabs for the first time. An extensive experimental program was conducted to validate this new fabric-reinforced cementitious matrix system. Parameters investigated in the tests included the duration of heating for the fire-damaged RC slabs, the types of the cementitious matrix (strain-hardening engineered cementitious composites (ECC) versus polymer-modified mortar (PMM)) and the layers of basalt fabrics that are used for the strengthening systems. A total of nine one-way slabs were constructed and tested in this paper. One slab served as the control specimen and was tested at ambient temperature, while the other eight slabs were initially exposed to the furnace fire following the ISO 834 standard temperature-time curve. After fire exposure, five slabs were strengthened using two or three layers of the strengthening systems. Test results indicated that the flexural capacity of the fire-damaged RC slabs strengthened with the basalt fabric-reinforced shotcrete systems was increased by 68.9–193.4% compared to their un-strengthened fire-damaged counterparts. The use of ECC as a cementitious matrix was found to be an attractive solution as the slabs strengthened using ECC achieved better results in terms of the cracking control and ultimate load, ductility performance as well as energy dissipation capacity.

Seismic behavior of 3-D ECC beam-column connections subjected to bidirectional bending and torsion

Special moment resisting frames (SMF) are commonly used in low- and medium-rise buildings located in regions of high seismicity. Although adequate performance of this seismic force resisting system was observed in prior earthquakes in terms of protecting buildings from collapse, the formation of plastic hinges in the beams and columns causes irreparable damage to the beam-column connections. Recently, interest in using fiber-reinforced concrete (FRC) has been growing to enhance energy absorption capacity and damage tolerance of beam-column connections and other components in reinforced concrete (RC) buildings. Prior research has mostly focused on the application of steel FRC (SFRC) in 2-D beam-column connections. However, little is known about the performance of exterior beam-column connections that are usually subjected to more complex loading during an earthquake, involving bi-directional bending and torsion of the column. In addition to the loading, the geometry of the connection requires a more involved test setup (i.e., with an out-of-plane beam and proper boundary conditions). In this research, the use of engineered cementitious composites (ECC) in 3-D exterior beam-column connections is investigated experimentally to improve building seismic performance. ECC is a special class of high-performance fiber-reinforced cementitious composites (HPFRCC) that, compared to conventional concrete, exhibits higher tensile ductility, energy absorption and shear resistance, in addition to improved bond performance with reinforcing steel (rebar). To understand the performance of exterior beam-column connections under complex loading conditions, scaled 3-D specimens were constructed and tested under simulated seismic loads. To improve the performance of the connections, conventional RC was replaced with reinforced ECC (RECC) that extends from the panel zone to the adjoining beams and columns to cover the potential plastic hinge regions. This paper discusses the loading protocols, the test setup for 3-D exterior beam-column connections, and the improvement in the joint behavior with the application of RECC as compared to conventional RC. The results suggest that the efficient use of ECC in the potential plastic hinge regions can improve the capacity and damage tolerance of beam-column connections under realistic seismic loading conditions.

Flexural behaviour of steel composite beams encased by engineered cementitious composites

In this study, the flexural behaviour of a new form of Engineered Cementitious Composite (ECC) - Light Weight Concrete (LWC) encased steel composite beams is studied. Four simply supported ECC-LWC encased steel composite beams were tested to investigate the effects of ECC cover thickness on the ultimate load carrying capacities and failure modes. The test results indicated that the ductility of ECC enhanced the residual strength of encased steel member even after the crushing of the top ECC cover. It is demonstrated that the structural performance of traditional steel-concrete composite beams could be improved by replacing normal concrete with ECC and LWC as the encasing materials. In addition to flexural strength enhancement, it is found that the combined use of ECC and LWC could improve the overall ductility of the beams and reduce their weights. To complement the experimental study, a three-dimensional nonlinear finite element model is developed to simulate the behaviour of ECC-LWC encased steel composite beams. The model was validated by comparing the numerical results to the experimental results. A parametric study was then conducted using the model to investigate the influence of the ECC compressive strength, the ECC tensile strength, the LWC compressive strength and the steel yield strength on stiffness, flexural resistance and ductility of ECC-LWC encased steel composite beams.

Assessment of self-sensing capability of Engineered Cementitious Composites within the elastic and plastic ranges of cyclic flexural loading

Engineered Cementitious Composites (ECC) are emerging construction materials with proven mechanical and durability characteristics. These outstanding properties make the material an attractive choice for different infrastructure types. But the growing use of ECCs brings about the need to monitor the health of the structures that employ them. This study therefore focused on the self-sensing capability of ECC with different carbon-based materials (multi-walled carbon nanotubes [CNT], graphene nanoplatelets [GNP], carbon black [CB] and carbon fibers [CF]) when subjected to repetitive loading and unloading cycles within the elastic and plastic ranges. Tests were conducted on beam specimens loaded and unloaded under four-point bending loading. Within the elastic range, 30% of the ultimate flexural strength was decided for application on the tested specimens. For the plastic range, prismatic specimens prepared for cyclic flexural loading at high levels were loaded up to 70% of their ultimate flexural strength. Experimental findings showed that for all proposed ECC mixtures, self-sensing of imposed damage (i.e. loading) was successful for both elastic and plastic ranges, while the self-sensing of load removal (i.e. unloading) in the elastic range was not achieved as successfully. This was most probably due to very small imposed damage and continuously increasing intrinsic electrical resistivity of individual carbon-based materials under loading, which cannot be discharged upon unloading. Compared to other carbon-based materials, CF utilization during ECC production was the most effective method for self-sensing of cyclic loading and unloading in the elastic and plastic ranges. Improving the proven superior mechanical and durability properties of ECC materials with self-sensing characteristic will multiply the benefits for truly sustainable infrastructures.

A Review on the Use of Engineered Cementitious Composite in Bridges

Engineered Cementitious Composite (ECC) is a material with high ductility, tensile strength and self-healing more than the standard concrete. Applications of ECC are beneficial due to its long life cycle, high strength, low cost in the long-term, low maintenance and environmentally friendly nature. Properties and hardened behavior of ECC highlights that ECC has a tight crack width development, which increases its ability to resist long-term effects of hot, frost and humid weather. Additionally, it results low water permeability coefficient and high steel corrosion resistance compared to other common alternative materials. One of the promising areas of application for ECC is in highway structures, especially highway bridges. Highway structures suffer constantly from adverse environmental loads and often require frequent repairing or replacing due to cracks; expansion; water and chlorides effects which cause steel corrosion or the slope between the pavement, slab and the support at the end of a bridge. Detailed review on different properties and characteristics of ECC and the current applications of ECC clearly highlights the motivation to enhance the use of ECC for bridge construction. In addition, ECC can be introduced in jointless bridges by putting an ECC link slab instead of the expandable mechanical joint.

Structural Performance of Polymer Fiber Reinforced Engineered Cementitious Composites Subjected to Static and Fatigue Flexural Loading

This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs) to Portland cement (C) ratio (SCM/C) on the flexural fatigue performance of engineered cementitious composites (ECCs). ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand), type of SCMs (fly ash “FA” or slag), SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag) exhibited strain hardening behavior (under static loading) with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag) in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.