Engineered Cementitious Composites Mixtures Research Articles

Assessment of interface characteristics and durability aspects of manufactured sand (M-sand) in engineered cementitious composites

Concrete structures usually tend to crack and cause several distresses, thus resulting in regular maintenance activities. Engineered Cementitious Composites (ECC) in structural applications are becoming popular due to their cracking resistance and deformability. However, the conventional mix design of ECC with silica sand levied a negative influence on cost and drying shrinkage, thereby affecting their practical implementation. In this study, the matrix properties and interface characteristics of ECC tailored with Manufactured sand (M-sand) replacing the river sand at varying proportions were investigated. The study conducted mechanical characterization, matrix fracture toughness, and single-crack tension tests to evaluate the micro-mechanical properties and fiber-matrix interaction. Furthermore, the shrinkage characteristics and permeability properties of ECC mixtures were also evaluated at various replacement levels of M-sand. The natural river sand adhered to the finer gradation, characterized by a fineness modulus of 1.63, while the M-sand exhibits a coarser gradation, having a fineness modulus 2.74. The experimental results showed that the ECC mixtures with M-sand improved the compressive strength (up to 29 %) at 100 % replacement level and marginally influenced the tensile strength. However, the tensile ductility and fiber bridging characteristics showed a noticeable decrease as the percentage replacement increased in the mixtures. On the other hand, the drying shrinkage of all M-sand ECC mixtures showed a notable reduction irrespective of the curing ages. It is also seen that the permeability properties were slightly increased compared to that of the control mixture. In summary, the study observed a trade-off between mechanical strength and tensile ductility, highlighting the effects of fiber-matrix interface tailoring on the overall performance of ECC mixtures with M-sand for various structural applications.

Engineered Cementitious Composites with Super-Sulfated Cement: Mechanical, Physical, and Durability Performance.

This study aimed to bridge a research gap by exploring the utilization of super-sulphated cement (SSC) in engineered cementitious composites (ECCs) as a sustainable alternative to ordinary Portland cement (OPC)-based mixtures. The SSC was designed with slag, gypsum, and a small amount of OPC. The primary objective was to investigate the effects of incorporating SSC, both with and without fly ash (FA), at various FA/SSC ratios between 0 and 1.5. A comprehensive evaluation was conducted to assess the performance of the ECC-SSC mixtures, including the compressive and flexural strengths, ductility, ultrasonic pulse velocity, rapid chloride permeability, and drying shrinkage. Additionally, advanced microstructural evaluation techniques such as scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis as well as X-ray diffraction (XRD) analysis were employed to analyze the reaction products in selected mixtures. The results showed that the ECC mixture produced with SSC exhibited comparable strength to the ECC-OPC. In general, all the SSC-based ECCs fulfilled the criteria for various engineering applications, especially when the fly ash to SSC ratios were 0 and 0.8. In addition, ECCs with FA/SSC ratios of 1.2 and 1.5 showed ultra-ductile performance higher than the control ECC. Interestingly, all the FA-based ECC-SSC presented lower shrinkage characteristics than the control OPC-based ECC.

Improving properties of Engineered Cementitious Composite (ECC) using Bacillus subtilis immobilized in silica gel

This study investigates the impact of incorporating Bacillus subtilis immobilized in silica gel (BS+SG) on various properties of Engineered Cementitious Composites (ECC). Silica gel serves as the immobilization medium to sustain bacterial viability in the challenging environment of ECC mixtures. The study explores bacterial content ranging from 5 % to 15 % of water content. Results reveal a significant enhancement in compressive strength for ECC with 5–15 % BS+SG, showing increases of 11.9–18.8 % at 28 days of water curing as compared to ECC without bacteria. This improvement becomes more pronounced at 56 days, attributed to silica gel’s protective role in preserving bacterial activity, leading to calcite production that effectively fills pores during extended curing. The positive impact extends to tensile strength and strain capacity. Additionally, BS+SG contributes to reduced porosity and water absorption even after prolonged curing, thus enhancing the durability of ECC. This study highlights the potential of BS+SG in advancing the properties of ECC, with emphasis on its role in improving compressive strength, strain capacity, and durability.

Investigation on mechanical behavior of engineered cementitious composites incorporating alkali‐resistant glass fiber and quarry dust

AbstractAt present, engineered cementitious composites (ECC) are rapidly replacing ordinary concrete in the building production due to its superior durability and mechanical qualities. Enormous researches have been done on ECC incorporating various fibers, industrial wastes, supplementary cementitious materials and super plasticizers. As far as fiber is concerned, poly vinyl alcohol fiber was widely explored. In this study, attempt has been made to involve alkali resistant glass fiber as a replacement for poly vinyl alcohol fiber. In addition, the high rate related with ECC as a result of the utilization of micro‐sized silica sand has restricted its extensive pertinences. Thus, this study recommends utilization of quarry dust to replace fine silica sand in the ECC at amounts ranging from 0% to 100% in order to establish a green, sustainable and cost‐effective ECC. The flowability and mechanical demeanor of the ECC mixtures in terms of the tensile, compressive and flexural properties were evaluated. It is arrived that 2% of volume fraction would be the optimum dosage by which better mechanical properties can be achieved. As a result of the present research findings, it is found that the quarry dust could be a better substitute for silica sand up to 75% without any compromise in compressive and flexural strengths. To attain higher tensile qualities, however, it might not be appropriate to replace more than 50% of the silica sand with quarry dust. Cost analysis of the ECC mixtures show that using quarry dust as aggregate is both cost‐effective and sustainable.

Fresh, Compressive and Direct-Tensile characterization of Engineered Cementitious Composite

A new category of high-performance fiber-reinforced composite broadly known as Engineered Cementitious Composite (ECC) has gained rapid attention in the construction industry in recent years. The exceptional behaviour of ECC, therefore high ductility, toughness, and durability, make it a promising material for various structural applications such as tunnel inner lining, dam and bridge deck slab construction. This investigation aims to study the fresh and mechanical characteristics of ECC, including workability, compressive, and direct tensile strength. A total of 15 ECC mixes are prepared with varying superplasticiser-binder ratio (0.200, 0.225, 0.250, 0.275 and 0.300 %), sand-binder ratio (0.35, 0.40 and 0.45) and a constant water-binder ratio (0.27). The mini-slump cone test was performed to examine the workability of the fresh ECC mixtures. The results showed that using a higher content of the superplasticiser resulted in an upsurge in both the workability of the fresh ECC mixtures and the mechanical strength of ECC, particularly the tensile strength. Apart from this, both the mechanical tests are performed at the 7 and 28 days. As per the results, both the compressive strength and direct tensile strength of ECC are found to be comparatively higher than that of the conventional mix. In conclusion, ECC is an efficient construction material for various structural applications, especially for the latest 3D printing construction techniques. The uniform dispersion of fibers significantly improves the tensile strength and ductility of ECC, making it a suitable material for seismic-resistant structures.

Adhesive characteristics of novel greener engineered cementitious composite with conventional concrete substrate

Engineered cementitious composite (ECC) is a high-graded advanced construction material that can be used to strengthen and repair structural composites owing to its high mechanical and durability properties. Nevertheless, the ability of ECC to strengthen and repair concrete surfaces depends on the interfacial bond between the conventional concrete (CC) substrate texture and ECC overlay. It ensures sufficient adhesive or bonding ability over a lifetime under various loading and environmental conditions. The present study investigates the bond strength between CC substrate and modified ECC with agro-industrial by-products, such as ground granulated blast furnace slag (GGBS), bagasse ash (BA), and rice husk ash (RHA). The bond strength is determined using three types of tests, namely the slant shear, split cylinder, and split prism tests. A mathematical model has also been developed to predict the bond strength of the different ECC mixtures. The results indicate that incorporating 40% GGBS, 10% BA, and 10% RHA in ECC helps in attaining the maximum interfacial bond strength with cross-hatched textures under all types of testing. According to the ACI standard, ECC with agro-industrial by-products ranging from 10% to 55% achieved the required bond strength in all three tests. Correspondingly, the outcomes of the present research are compared with those obtained from previous studies to gain further insights into various applications, which are highly relatable. Furthermore, the experimental outcomes were strongly correlated with the mathematical modeling with great accuracy.

Effect of polyvinyl alcohol fiber on the mechanical properties and embodied carbon of engineered cementitious composites

Engineered cementitious composite (ECC) is a fiber-reinforced cementitious composite material that has garnered considerable attention from the building and scientific sectors. However, ECCs offer improved mechanical and durability characteristics compared to regular concrete. Fibers serve a crucial function in producing ultrahigh tensile ductility and autogenous fracture width control inside the micromechanical reinforcing system of ECC. This research discusses the various proportions of polyvinyl alcohol fibers (PVA) as reinforcing materials by total volume fraction in ECC in terms of mechanical properties performance, environmental consequences, and economic effects. A total of 60 ECC samples were cast to achieve the targeted compressive strength of 45 MPa of ECC mixture reinforced with 1%, 1.5%, and 2% of PVA fiber by the volume fraction. Though, the best compressive of ECC is calculated by 62.60 MPa at 1% of PVA fiber at 28 days. Besides, the tensile and flexural strengths are enhanced by 5.20 MPa, and 11.15 MPa at 1% of PVA fiber in ECC for 28 days respectively. In addition, the density of ECC is reduced with rises in the content of PVA fiber while water absorption is increased as the percentage of PVA fiber growths in the ECC after 28 days respectively. Moreover, the embodied carbon and energy are improved when the PVA fiber by the volume fraction increases in the mixture. It has been observed that the use of 1% PVA fiber by the volume fraction in cementitious composites is offering maximum strength and less embodied carbon and energy, therefore, it has been recommended for structural application.

Generative AI for performance-based design of engineered cementitious composite

Engineered cementitious composite (ECC) has been intensively studied due to its excellent tensile performance. However, classical micro-mechanical design theory of ECC is qualitative and fails to give detailed ECC mixtures at specific tensile parameters. This study aims to develop a performance-based mixture design model to generate ECC mixtures using generative AI method. An experimental database consisting of 129 polyethylene fiber reinforced ECC (PE-ECC) records has been built. The database was used to train one invertible neural network model and two artificial neural network models. A series of PE-ECC mixtures were generated by the proposed model based on desired mechanical performance and sustainable requirements. Based on the experimental results, the developed model was proven to compose PE-ECC mixtures that satisfy the target requirements with a maximum deviation of less than 16%. The neural network-based model can be used in various application scenarios (e.g., low-cost ECC and low-carbon ECC), thus promoting the development of ECC materials in the area of research and engineering application.

Effect of graphene oxide as a nanomaterial on the bond behaviour of engineered cementitious composites by applying RSM modelling and optimization

A crucial aspect of the design approach for bar-reinforced concrete buildings is the proper transfer of loads between the concrete and steel reinforcement via bonding. Bar pull-out tests were done to see how graphene oxide (GO) affected the bond strength, bond energy, and bond stress–slip response of deformed reinforcing bars implanted in engineered cementitious composites (ECC). This was done to improve the bond strength of steel/concrete composites. This article examines the bonding behaviour of steel reinforcing bars in a mixture of GO-modified ECC. The findings of pull-out assessments conducted on two distinct diameters (12 and 16 mm) of reinforcement steel bar inserted in ECC are initially provided. The investigation's findings are then utilised to determine the bond-slip interactions that describes the relations between the ECC mixtures and steel reinforcement bars. According to the experiment results, the introduction of GO as a nano-reinforcement in the ECC mixture had a considerable positive effect on the bar-matrix interactions owing to its bridging function. After 28 days, the bond strength of steel bars with widths of 12 and 16 mm was increased by 54.80% and 26.70%, respectively, when 0.05 wt% of GO was added to 1% of PVA fibre. The response surface methodology (RSM) is employed for developing predictive algorithms, which are then utilised in performing multi-variate optimization on bond-slip parameters, including bond strength, bond slip and bond energy. The acquired actual and predicted findings suggest that the created models are adequate for interpreting the bond performance of reinforcement steel bars in the GO-ECC.

Tensile properties of slag-based engineered cementitious composites with ground granulated blast-furnace slag

During the last decade, concrete technology has been undergoing rapid development, resulting in a new concept of engineered cementitious composite (ECC) to overcome the brittle behaviour of cement-based materials. ECC is one movement to fully incorporate waste material as an innovation in green material due to excellent toughness and energy absorption capacity, self-healing ability, fire performance, and remain durable under erosion environment. ECC exhibits a strain-hardening behaviour through the formation of micro cracking. This study is focusing on the tensile behaviour of the slag-based ECC. A total of five ECC mixes were designed with different cement to ground granulated blast-furnace slag (GGBS) ratio. Five samples of dog bone and three cylindrical for each mixture were prepared for direct tensile and compression tests. Compared to control samples, there are increments in compressive strength for samples contained 50-60% of GGBS and reductions in compressive strength for samples contained 70-80% of GGBS. The tensile strengths of ECC increase in the rate proportionally to the content of GGBS in ECC mixtures. The failure modes of the ECC cylinder samples including crushing under compressive load and few micro cracks are observed in ECC dog bones.

Prediction of the compressive strength of strain‐hardening cement‐based composites using soft computing models

AbstractStrain‐hardening cement‐based composites or engineered cementitious composites (ECC) is concrete produced using randomly distributed short polymer fibers. It is very ductile compared to conventional concrete. Compressive strength (CS) is a critical property used as a quality control tool to evaluate the strength of concrete implemented in the structural provisions and mix designs. Accordingly, to save cost and time for testing, it is essential to provide a predictive model to forecast the CS of the concrete mixtures using machine learning and modeling techniques. In this study, different modeling tools are used to propose analytical models to predict the CS of ECC mixtures, such as linear regression (LR), multi‐expression programming (MEP), artificial neural network (ANN), and Gaussian process regression (GPR). A total of 210 data were collected from the literature and used to train and test the developed model. The fly ash‐to‐cement ratio ranged from 0 to 5.6, water to binder ratio from 0.19 to 0.56, different superplasticizer and fiber content, and curing times of 1 to 180 days. Based on the evaluation of the developed models, the ANN model is superior to other developed models with a high coefficient of determination (R2), root mean squared error (RMSE), mean absolute error (MAE), and scatter index (SI). The sensitivity analysis of the input parameters' effect on the CS prediction indicates that the curing time and the fly ash‐to‐cement ratio are essential in forecasting ECC's CS.

RC columns strengthened with engineered cementitious composite (ECC) jacketing

This article aims to study the uniaxial compressive behavior of reinforced concrete (RC) columns strengthened with engineered cementitious composite (ECC) jackets. For this purpose, two advanced ECC mixtures containing polypropylene fibers were designed, and ECC jackets were cast to confine fourteen circular column specimens. Longitudinal and transverse grooving, sandblasting, and abrading were used as surface preparation techniques to achieve better adherence of ECC jackets to eight control (reference) column specimens, while two specimens with no surface preparation but with the same jacketing were used as a reference. The four remaining concrete column specimens lacking either internal reinforcement or an ECC jacket were used as control. All the specimens were subjected to concentric loading to determine the efficiency of ECC jacketing in enhancing load-carrying capacity and ductility. The experimental results revealed that compared to the control column, the reference specimens subjected to longitudinal grooving as surface preparation and ECC jacketing exhibited improvements of up to 1.3 and 2.5 times in their load-bearing capacity and energy absorption, respectively. Besides, ECC jacketing in specimens with the longitudinal grooving method increased the reference columns’ initial and secant stiffness values by up to 3.2 and 1.6 times, respectively. Finally, the models reported in the literature were evaluated in terms of their ability to capture the stress-strain curves of the ECC jacketed RC columns used in the present study.

Strain hardening green cementitious composites reinforced with nanoparticles: Mechanical and microstructural properties and high temperature effect

This study investigates the effect of nano-particles on the composite's mechanical, microstructural, and high-temperature resistance by using TiO2 and Al2O3 nano-particles in different proportions in the engineered cementitious composites (ECC) composite. TiO2 and Al2O3 nanoparticles were used in three different ratios (0.5%, 1%, and 1.5%) in the ECC mixtures. Then, flexural strength, compressive strength, and ultrasonic pulse velocity (UPV) experiments were conducted on the prepared composites. The relationships between the concentration of TiO2 and Al2O3 nano-particles and the compressive strength were investigated. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) analyses were performed to investigate the microstructural contents of the prepared samples. In addition, the effects of high temperatures on the mechanical properties of nano-doped ECC samples were investigated at 200, 400, 600, and 800 °C. The content of 1% TiO2 (1 TiN) and 1.5% Al2O3 (1.5 AlN) nano-particles increased the compressive strength of the nano-doped-ECC samples by 19.6% and 20.2% compared to the nano-free control samples. Also, the increases in compressive strength of 1 TiN and 1.5 AlN samples exposed to 800 °C increased up to 26.24% and 34.56%, respectively.

Effect of graphene oxide particle as nanomaterial in the production of engineered cementitious composites including superplasticizer, fly ash, and polyvinyl alcohol fiber

Graphene oxide (GO) is a desirable nanoparticle for strengthening composite material owing to its outstanding mechanical characteristics. This research examines the influence of graphene oxide (GO) on the mechanical characteristics of Engineered Cementitious Composites (ECCs), including their mechanical performance under tension and compression conditions. In this study, GO was utilized with different percentages like 0 %. 0.02 %, 0.04 %, 0.05 %, 0.06 %, 0.08 % and 0.10 % by the weight of cement for determining the compressive strength, direct tensile strength and modulus of elasticity of ECC mixture. However, the dry density is improving as the content of GO increases while the water absorption is getting reduced blended with GO as nanomaterials rises in the ECC mixture after 28 days correspondingly. It has been observed that the use of GO as nanomaterial up to 0.08 % in ECC mixture is providing optimum compressive strength, tensile strength and modulus of elasticity after 28 days respectively. The increased composite strength as well as the chemical connection formed by the introduction of GO between the polyvinyl alcohol (PVA) fiber and the cement matrix are both responsible for the excellent mechanical characteristics of the GO-reinforced ECC mixture.

Axial compressive behaviour of thin-walled composite columns comprise high-strength cold-formed steel and PE-ECC

A new form of thin-walled composite columns, made of high-strength cold-formed steel (CFS) open sections and thin layers of engineered cementitious composites (ECC), is presented in this paper. The axial behaviour of columns with slenderness ratios (le/r) ranging between 10.08 and 13.86 under concentric loads were experimentally investigated. Twelve column specimens were divided into four groups of bare CFS columns, plain ECC columns, composite columns with SupaCee sections, and composite columns with Lipped-Cee sections. A specific ECC mixture with three PE-fibre contents: 0.75%, 1.75%, and 2.25% by mix volume, was placed in the tested columns in two thin thicknesses of 16.0 mm and 26.0 mm. Additionally, a high-strength concrete (HSC) mixture was utilised in two test columns for comparison with ECC. The results revealed that the composite CFS/ECC columns exhibited enhanced axial compressive capacities up to 2.79 times that of the bare CFS columns. The ductility indices and compressive toughness of the composite CFS/ECC columns were improved to 1.56 and 3.85 times those of the bare CFS columns, respectively. Strength prediction equations were developed based on the experimental observations to estimate the axial compressive capacity of composite CFS/ECC columns susceptible to local buckling.

Performance of cost effective engineered cementitious composite in exterior beam‐column connections under cyclic loading

AbstractThe present research examines the structural performance of exterior beam‐column connections made with the hybrid use of fibers and stone waste in engineered cementitious composite (ECC). The polyvinyl alcohol (PVA), recron 3 s polyester (PET) and micro steel fiber (MSE) were dispersed in various ECC mixtures to analyze the impact of fiber hybridization. The stone waste (SW) was utilized in different ECC mixtures as replacement of silica sand (SS). The performance of ECC beam‐column connection specimens was judged in terms of hysteresis load–deflection behavior, energy dissipation, ductility, and cracking pattern. The recorded results of ECC reinforced specimens were compared with specimens made with normal concrete (NC). Recorded results revealed that the connections made with ECCs exhibited better performance in terms of ductility and various parameters as compared to NC connections. The hybrid dispersion of fibers and addition of SW also contributed in improving the behavior of ECC specimens. The higher deformation, loading response, energy dissipation and ductility indicated that structures made with ECC can withstand strong ground earthquake motions.

Influence of Stone Processing Waste on Mechanical, Durability, and Ecological Performance of Hybrid Fiber-Reinforced Engineered Cementitious Composite

The current study is focused on the characteristics of sustainable engineered cementitious composites (ECCs) with the inclusion of various types of fibers (PVA, PET, and MSE) in hybridization, silica sand (SS), river sand (RS), and stone processing waste (SPW). SPW is termed as hazardous material because of the presence of finer particles and inorganic substances which contribute to leaching problems, and cause adverse effects on aquatic life and human health. The objective of this study was to introduce new kind of cost-effective, sustainable, and greener ECC to encourage its use in diversified applications. The characteristics of different ECC mixtures were assessed by observing the slump flow, compressive, tensile, flexural, ultrasonic pulse velocity, air permeability, electrical resistivity (ER), sorptivity, ecological behavior, and cost analysis. Experimental results revealed that the combination of micro-fibers enhanced the overall performance of ECC with reduction in the matrix cost. The addition of SPW in place of aggregates enhanced the flowability, strength, and durability characteristics, and contributed to reducing the carbon dioxide emissions. This study confirms that the combined use of PVA, PET, and MSE fibers with SPW inclusion is a promising alternative over the fully PVA blended ECC with SS.

Coupling effect of cementitious capillary crystalline waterproof material and exposure environments on self-healing properties of engineered cementitious composites (ECC)

Due to the healing mechanism of self-healing technologies, there are some limitations and challenges for application in concrete structures. Based on the characteristics of cementitious capillary crystalline waterproof material (CCCW) in powder and active materials moving along cracks, this work presents CCCW as a direct internally mixed self-healing material, and quantitatively explored the coupling effect of CCCW and exposure environments on the self-healing properties of engineered cementitious composites (ECC). Four types of ECC mixtures with CCCW doping of 0%, 1.5%, 3% and 4.5% were prepared. Exposure environments contained water, air and saturated calcium hydroxide solution. The self-healing behavior of ECC was evaluated by the recovery of mechanical properties, water impermeability and closure behavior of crack. Microscopic analysis of healing products was performed by scanning electron microscope (SEM), thermogravimetric analysis (TG) and X-ray diffraction (XRD). The test results showed that the recovery of mechanical properties and water impermeability of ECC was improved by directly adding CCCW. The percentage of re-opened healed cracks number in specimen EC45 with 4.5% CCCW content was 83.33% lower than that in specimen EC0 without CCCW. The normalized closure rate of crack area was raised by 167.98% by mixing 4.5% of CCCW in saturated calcium hydroxide solution, compared with that without CCCW. While it was enhanced by 132.44% in water. There was a superimposed enhancement of CCCW and calcium hydroxide solution. Microscopic analysis of healing products showed that CCCW facilitated the production of healing products, especially in saturated calcium hydroxide solution. Finally, the additive effect coefficient Ki was introduced to quantitatively characterize the coupling effect of environments and CCCW on the self-healing properties of ECC.

Computing Models to Predict the Compressive Strength of Engineered Cementitious Composites (ECC) at Various Mix Proportions

Concrete has relatively high compressive strength (resists breaking when squeezed) but significantly lower tensile strength (vulnerable to breaking when pulled apart). The compressive strength is typically controlled by the ratio of water-to-cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words, we can say concrete is made up of sand (which is a fine aggregate), ballast (which is a coarse aggregate), cement (which can be referred to as a binder), and water (which is an additive). Highly ductile material engineered cementitious composites (ECC) were developed to address these issues by spreading short polymer fibers randomly throughout a cement-based matrix. It has a high tensile strain capacity of more than 3%, hundreds of times more than conventional concrete. On the other hand, among the other examined qualities, compressive strength (CS) is a critical property. Consequently, developing reliable models to predict an ECC’s compressive strength is crucial for cost, time, and energy savings. It also includes instructions for planning construction projects and calculating the optimal time to remove the formwork. The artificial neural network (ANN), nonlinear model (NLR), linear relationship model (LR), multi-logistic model (MLR), and M5P-tree model were all proposed as alternative models to estimate the CS of ECC mixtures created by fly ash in this research (M5P). To create the models, a large amount of data were gathered and evaluated, totaling roughly 205 mixes. Various mixture proportions, fiber length, diameter, and curing durations were explored as input variables. To test the effectiveness of the suggested models, several statistical evaluations, including determination coefficient (R2), Mean Absolute Error (MAE), Scatter Index (SI), Root Mean Squared Error (RMSE), and Objective (OBJ) value, were utilized. Based on the statistical evaluations, the ANN model performed better in forecasting the CS of ECC mixes incorporating fly ash than other models. This model’s RMSE, MAE, OBJ, and R2 values were 4.55 MPa, 3.46 MPa, 4.39 MPa, and 0.98, respectively. A large database presented in this investigation can be used as the bench mark for future mixture proportions of the ECC. Moreover, the sensitivity analysis showed the contribution of each mixture ingredient on the CS of ECC.

Experimental study and analysis model of flexural synergistic effect of reinforced concrete beams strengthened with ECC

• The flexural synergistic effect of RC beams strengthened with ECC is synthetically investigated. • A synergy analysis model is proposed to determine critical ECC strengthening layer thickness and predict crack propagation pattern. • A critical ECC strengthening layer thickness is determined to obtain the optimal crack resistance. This work aims to synthetically investigate the flexural synergistic effect of reinforced concrete (RC) beams strengthened with engineered cementitious composite (ECC) through both experimental study and analysis model. Eight beam specimens are prepared to investigate the effects of five important parameters on the flexural synergistic effect, including the ECC compressive strength, interface roughness, fiber type, ECC mixture consolidation level, and ECC casting method. The experimental results are analyzed to characterize the failure mode, crack propagation pattern, crack load, crack width, ultimate load, load–displacement curve, and strain distribution at mid-span cross section. Besides, a bond-slip model of ECC and concrete interface is adopted in finite element analysis to simulate and validate failure mode, load–deflection response, and strain distribution at mid-span cross section. More importantly, a synergy analysis model is proposed to determine critical ECC strengthening layer thickness and predict crack propagation pattern. The prediction results of proposed model are in consistent with the experimental results from not only this study but also other research, indicating that the proposed model can effectively predict the crack propagation pattern of RC beams strengthened with ECC. This study is expected to promote a comprehensive understanding for application of ECC for strengthening or retrofits of existing RC structures.