Engineered Cementitious Composite Mix Research Articles

Engineering characteristics, techno-economic feasibility and life cycle assessment of bio-fiber based green engineered cementitious composites

The objective of the present work is to understand the microstructural, and life cycle analysis of novel engineered cementitious composites (ECC) where the conventional synthetic micro-fibers are replaced using bio-based fibers. A detailed mechanical and microstructural characteristics of the developed ECC mix are presented first to understand the feasibility of introducing natural fibers without compromising the ductility and strength of the mix. To prove the cost-effectiveness and sustainable balance, a detailed life cycle analysis (LCA) was performed using different sustainability indices such as cost, embodied energy, and carbon emissions. The natural fiber ECC mixes developed in this work are compared with similar artificial fiber ECC mixes for different LCA parameters. Results from the tensile tests revealed that using natural fibers in an ECC mix aided in achieving significant tensile strength (4.3–10.2 MPa) and failure strain levels (2.5 %–3.5 %). Specifically, using flax fibers in the ECC mix aided in achieving a high tensile strength of 10.2 MPa corresponding to an ultimate strain of 2.5 %. From the outcomes of LCA, the use of kenaf and pineapple can be recommended for sustainable ECC production without compromising its mechanical characteristics.

Numerical and experimental study of Yellow River sand in engineered cementitious composite

Engineered cementitious composites (ECCs) represent a significant advancement in concrete technology, addressing the issues and limitations of conventional concrete and environmental challenges related to sedimentation in rivers such as the Yellow River in China. This study investigates the integration of Yellow River sand (YRS) into ECC mix designs for sustainable development. YRS replacement rates (0, 25, 50, 75 and 100%) with quartz sand are systematically analysed through flexural, compressive, uniaxial tensile and four-point bending tests. In addition, scanning electron microscopy and mercury intrusion porosimetry tests are conducted to investigate the micro-mechanical properties. The results reveal that the optimal mechanical performance with 100% YRS substitution improves the compressive and flexural strengths to 26.4 and 11.5 MPa, respectively. These values are 6.20% lower than the those of the 0% substitution rate. Notably, a 100% replacement maintains an ultimate tensile strain of 3.71%, improving the crack width and spacing compared with those at 0%. The average crack width and spacing decrease by 4.87 and 11.2%, respectively, compared with those of 0% substitution. The four-point bending test results show the highest ductility at a 75% substitution rate. Furthermore, a finite-element method model of ECC beams with YRS is developed and validated under the same loading conditions as the experimental data. This study recommends an analytical method for predicting flexural strength compared with the experimental data, enhancing its suitability for sustainable engineering applications.

The Optimum Percentage of Rice Husk Ash (RHA) as Partial Cement Replacement in Engineered Cementitious Composite (ECC)

Rice Husk Ash (RHA) is a potential supplementary cementitious material (SCM) in concrete production due to their capability of pozzolanic reaction. This research study on the fineness, workability and compressive strength of the RHA incorporated into Engineered Cementitious Composites (ECC) as a cement replacement alternative hence to determine the optimum percentage of RHA to be use in the ECC mix. The mix proportional of RHA-ECC was designed with RHA as the substitution of Portland cement at various percentages by volume, including 5%, 10%, 15% and 20% respectively. Physical characterization of RHA was determined by particle size distribution test. The workability of hand mixed mortar was determined by the flow table test. A total of 45 cubes of 50×50×50 mm was prepared and cured for 7, 14 and 28 days. These hardened mortars were test with the compressive strength test to study its mechanical property. Findings showed that the workability of RHA-ECC was decreased with increasing of the amount of RHA added. The compressive strength of RHA-ECC was best at 28 days with the 10% of replacement level compared to others. This study will provide both direction and knowledge on the application of RHA as a greener and sustainable cement replacement.

Elasticity and Load-Displacement Behavior of Engineered Cementitious Composites produced with Different Polymeric Fibers

Engineered Cementitious Composites (ECC) are ultra-ductile materials, and the fibers used provide superior flexibility and strain capacity. This study investigates the use of two different types of polymeric fibers, Polypropylene (PP) and Polyvinyl Alcohol (PVA), with volume fractions of 1 and 2%, and studies their effect on stress-strain relationships, load-displacement behavior, toughness, and elasticity of ECC mixes produced with two strength levels, 30 and 60 MPa. The results showed that mixtures with PVA fiber ionic coating had a better performance than those with PP fibers due to the chemical reaction between the PVA fibers and the ECC matrix. This performance was confirmed by Scanning Electronic Microscopy (SEM). For normal-strength concrete (30 MPa), the modulus of elasticity increased by 7.8 and 9.6% for mixes with PP and PVA fibers, respectively, while in high-strength mixes (60 MPa), it increased by 9.4 and 10.85%, respectively. Toughness increases with increasing matrix strength, which is associated with an increase in cement content and fiber fraction. This study also investigates the effect of incorporating a PVA solution in ECC mixes, which leads to an increase in yield stress. This behavior was observed in the stress-strain behavior of 60 MPa mixes with 2% fibers which were compared to 30 MPa mixes with 1% fibers.

Development of low carbon engineered cementitious composite (ECC) using nano lime calcined clay cement (nLC3) based matrix

The construction industry is responsible for around 5% of total CO2 emissions globally. As a result, recent research is focused on the sustainability aspects of construction materials. Engineered cementitious Composites (ECC) are high-performance fiber reinforced composites with improved ductility and tensile strength but utilize higher cement content, raising concerns about their sustainability. In this study, nano-lime and calcined clay are combined with cement to develop a high strength sustainable nano lime calcined clay cement (nLC3) based Engineered Cementitious Composite (ECC). Initially, the packing density model was employed to develop a high strength nLC3-based matrix by combining the particle packing models and chemical compatibility while keeping costs to a minimum. Micromechanical modeling was then applied to determine the critical volume of fibers for the novel matrix using single fiber pullout tests and matrix toughness tests. According to the micromechanical model, the critical volume fraction is found to be 1.93% for the nLC3 mix. This was further confirmed by casting dog bone samples containing 2% fibers by volume which confirmed strain hardening response. The uniaxial test results indicated a strength of around 5.85 MPa in tension and 51 MPa in compression with about 3% tensile strain. These results are comparable to conventional ECC and better than previously developed LC3 based ECC. This study reveals that nLC3-based ECC is a more sustainable composite as compared to conventional ECC mix without any compromise on strength and cost.

Printability and shape fidelity evaluation of self-reinforced engineered cementitious composites

Incorporating fibers into Engineered Cementitious Composites (ECC) renders it a promising self-reinforced candidate for additive manufacturing, which can effectively address the challenges of reinforcement and automation. Considering this research challenge the current study aimed at designing 3D printable ECC mixes. The problems involved in the printability of ECC such as poor extrudability, buildability and shape retention, were addressed by utilizing the methylcellulose (MC) as a viscosity-modifying admixture. The results indicated that adding 1 % MC improved the fiber dispersion coefficient by 28 % and increased static yield stress in a range of 4 % to 237 % and plastic viscosity in the range of 247 % to 950 % in four different ECC mixes. Accordingly, the dimensional conformity of 3D printed filaments was considerably improved, and all designed ECC mixes meet the extrudability and buildability requirements.

Optimisation of the Mechanical Properties and Mix Proportion of Multiscale-Fibre-Reinforced Engineered Cementitious Composites.

Engineered cementitious composites (ECCs) are cement-based composite materials with strain-hardening and multiple-cracking characteristics. ECCs have multiscale defects, including nanoscale hydrated silicate gels, micron-scale capillary pores, and millimetre-scale cracks. By using millimetre-scale polyethylene (PE) fibres, microscale calcium carbonate whiskers (CWs), and nanoscale carbon nanotubes (CNTs) as exo-doped fibres, a multiscale enhancement system was formed, and the effects of multiscale fibres on the mechanical properties of ECCs were tested. The Box-Behnken experimental design method, which is a response surface methodology, was used to construct a quadratic polynomial regression equation to optimise ECC design and provide an optimisation of ECC mix proportions. The results of this study showed that a multiscale reinforcement system consisting of PE fibres, CWs, and CNTs enhanced the mechanical properties of ECCs. CWs had the greatest effect on the compressive strengths of highly ductile-fibre-reinforced cementitious composites, followed by CNTs and PE fibres. PE fibres had the greatest effect on the flexural and tensile strengths of high-ductility fibre-reinforced cementitious composites, followed by CWs and CNTs. The final optimisation results showed that when the ECC matrix was doped with 1.55% PE fibres, 2.17% CWs, and 0.154% CNTs, the compressive strength, flexural strength, and tensile strength of the matrix were optimal.

Performance evaluation of the fresh and hardened properties of different PVA-ECC mixes: An experimental approach

This paper aims to investigate experimentally the effect of two different polyvinyl alcohol (PVA) fibres (REC15 ×8 and RF4000 ×30) on the mechanical and physical properties of different mixes of Engineered Cementitious Composites (ECC). An effort has been made to overcome the issue of the high cost of ECC without compromising its tensile properties. For this purpose, three different types of ECC mixes (with and without coarse aggregate) have been investigated for varying dosages of fibre contents by volume (0%, 0.5%, 1%, 1.5% and 2%). Slump, density, compression, flexure, split tensile and ductility tests are performed for fresh and hardened concrete/ECC specimens. It has been revealed through experimental results that the workability of all the mixes decreased with the increasing percentages of fibres, however, it remained within the allowable range of ASTM for fibre contents of up to 2%. It was further observed that the ductile behaviour of ECC was greatly compromised with the use of coarse aggregate in the mix, however, strain hardening and multiple-cracking properties were found to remain intact. Mechanical properties (compressive, tensile, flexural strengths) were found to increase with increasing fibre contents up to a maximum dosage of 1.5%. Beyond 1.5%, a slight decrease in the mechanical properties for almost all the mixes was observed, thus 1.5% fibre contents were revealed to be the optimum dosage.

Effect of different exposure conditions on the self‐healing capacity of engineered cementitious composites with crystalline admixture

AbstractIn this study, the effect of different exposure conditions of ambient air, tap water, and seawater on two levels of crack widths in engineered cementitious composites (ECC) were investigated. Crystalline admixture (CA) was implemented in the ECC mix to promote self‐healing capacity. Flexural testing on prism specimens (100 × 100 × 350 mm) was conducted to evaluate self‐healing by recovering the stiffness in the specimens with crack widths below 200 μm. Water permeability test was also carried out to assess the crack‐filling capability of ECC disk specimens (100‐mm diameter × 50‐mm thickness) with single crack widths over 1 mm. Digital image correlation technique was used to monitor crack propagation patterns and crack widths. To analyze the microstructure of the healing products, X‐ray diffraction test was conducted on groups of tap water and seawater exposures. Concluding results proved seawater to be a promising environmental condition for the self‐healing process in ECC specimens incorporating CA, in terms of recovery of mechanical and transport properties. Brucite was found to be formed as the additional healing agent that promoted self‐healing in this condition. These results can be applied for coastal concrete structures.

Mechanical and shrinkage performance of 3D-printed rubberised engineered cementitious composites

Taking the advantages of 3D concrete printing (3DCP) and tackling the environmental issues related to the waste tires, current paper evaluates the material behaviour of rubberised engineered cementitious composites (ECC) using waste crumb rubber (CR) aggregates and polyvinyl alcohol (PVA) fibres, manufactured through 3DCP. To elaborate on the role of PVA fibres on the material properties, two different control mix designs were prepared through conventional mould-casting method, including control mix design without PVA fibres and ECC with PVA fibres equal to 1.75 vol% of binder. Thereafter, using the control ECC mix design, four mix designs containing 5, 10, 15, and 20% CR aggregates as replacement of fly ash, were prepared to assess the effect of CR on the mechanical performance of ECC. The prepared mix designs were subjected to compressive and flexural strengths, and shrinkage tests, and the rubberised ECC containing 5% CR was selected for 3DCP as it revealed superior compressive, flexural and shrinkage behaviour. Results obtained for 3D-printed specimens confirmed the dominant role of anisotropy on the material performance, which was very pronounced for flexural behaviour of printed elements. Comparing to the samples loaded in perpendicular direction, loading in the parallel direction to the fibre orientation (X direction) led to 3 and 4% higher 7- and 28-day compressive strengths, and loading parallel to the fibre alignment along the longitudinal axis of the specimen (Z direction) resulted in 104% and 47% increase in the 7- and 28-day flexural strengths, respectively. Moreover, printed specimens in the fibre-parallel direction showed 37% less drying shrinkage comparing to those printed in the perpendicular direction. Additionally, 3D-printed elements represent superior performance in terms of compressive strength, ductile characteristics, flexural behaviour, and shrinkage performance over the mould-casted ones.

Economic input-output LCA of precast corundum-blended ECC overlay pavement

Many studies have explored the prospect of using Engineered Cementitious Composites (ECC) in rigid pavements by looking at aspects such as mechanical performance, temperature susceptibility, cost, and environmental impact. Although ECC is an excellent choice because of its high tensile capacity, its major drawback for pavement applications is that it lacks roughness because of no coarse aggregates. Recently, an ECC mix containing corundum fine aggregates has shown remarkably higher skid resistance and drainage performance for pavement applications. The current study attempts to perform a comprehensive Economic Input-Output Life Cycle Analysis (EIO-LCA) of a concrete pavement having a precast corundum-blended ECC overlay. This LCA is compared with the LCA of a conventional rigid pavement and a full-depth conventional ECC pavement. The study includes both an inventory analysis using EIO-LCA and an impact assessment at midpoint and endpoint level on selected impact categories. It is found that the pavement having a precast corundum-blended ECC overlay is more economically and environmentally sustainable than the full-depth concrete and ECC pavements, and also has lower life-cycle impacts overall.

Tensile Behaviour of Slag-based Engineered Cementitious Composit

Engineered Cementitious Composites (ECC) have become another alternative in the concrete industry due to their excellent strain capacity under uniaxial tension. Research and development for new ECC mix incorporating wastes remain open to fulfil the industrial needs to produce green and sustainable ECCs. This paper presents the experimental work on the tensile and cracking behaviour of ECCs utilising industrial waste, namely ground granulated blast-furnace slag (GGBS), to replace cement. A total of four slag-based ECC mixes containing 2%–2.5% of PVA fibres and 50%-60% GGBS were investigated under uniaxial compressive and tensile tests. Compressive strength, tensile strength and the crack behaviours of the slag-based ECCs were evaluated and compared with a control mix. The experimental results show that the slag-based ECCs can achieve tensile strain capacity 2.6 %–2.75 % and ultimate tensile strength 1.43 MPa–2.82 MPa at 28 days. It was also found that the ECCs with GGBS and fibres formed few hairline cracks at the gage of the dog bone compared to brittle fracture in the control specimens.

Mechanical Properties of Modified Engineered Cementitious Composites (MECC) Incorporating Marble Dust

Engineered cementitious composites (ECC) are a type of high-performance fiber reinforced cementitious composite. ECC has different applications in the construction field due to its inherent characteristics of high tensile strain. The main concern regarding ECC is its high cost. The content of cement is high contributing to its cost. In this research work, the cement in ECC is replaced with marble dust and its mechanical properties such as compressive strength and flexure strength have been assessed. For this purpose, both cubes and cylinders were tested at different test ages for finding the compressive strength development with time and observe the shape effect of specimens on the compressive strength of ECC mixes. Beam members were tested for finding the flexure strength of ECC mixes. Deflection gauge was also installed at the mid span on the bottom surface of the beams to find the maximum mid span deflection before failure. The compression test results of both cylinders and cubes revealed that using of marble dust has negative effect on the compressive strength of ECC. The flexure strength result showed that marble dust can be used up to some extent replacing cement will increase the flexure strength. The result of mid span deflection suggests that by incorporating marble dust in ECC, its ductility increases.

Investigation of matrix cracking properties of engineered cementitious composites (ECCs) incorporating river sands

Typical ECC mix design omits normal aggregates and adopts only fine micro silica sands. Few studies report the possibility of using river sands in ECC mix design. While the resulting ECC is more economical with improved time-dependent properties, a very different tensile strain-hardening behavior is also observed. The current study reveals the fundamental mechanisms by investigating the matrix cracking properties ECC incorporating river sands. Results show that the use of river sands alters the matrix fracture toughness and introduces microcracks along the aggregate/matrix interface. As a result, the matrix cracking strength of the high strength ECC with river sands is reduced, which favors multiple cracking and tensile strain-hardening. In contrary, the matrix cracking strength of the normal strength ECC with river sands is increased, which hinders multiple cracking and tensile strain-hardening.

On rubberized engineered cementitious composites (R-ECC): A review of the constituent material

Researchers have used crumb rubber in the manufacturing of engineered cementitious composites (ECC) as a solution for spalling, however, it reduces the mechanical and physical properties. Therefore, this research reviews the available and related literature reviews on rubberized ECC and its constituent. The role of each constituent in a rubberized ECC mix is also reviewed. It’s concluded that utilizing rubberized ECC helps to solve environmental issues relating to improper disposal of tyres. As a result, fly ash has been the most common substance utilized in rubberized ECC by scholars all over the world over the past years because of its encouraging impacts on rheology, matrix toughness control, and interactive effect between fiber and matrix. It’s also found that the rectification of the crumb rubber drawbacks in ECC is by incorporating a modern method of adopting nano-silica, Polyvinyl alcohol (PVA) fibers, graphene oxide into the rubberized ECC mixes. Therefore, rubberized ECC can be utilized for civil engineering applications, especially with the inclusion of nano-silica and graphene oxide, as a result of its high ductility and low permeability.

Experimental and analytical investigation of high performance concrete beams reinforced with hybrid bars and polyvinyl alcohol fibers

This paper investigates the flexural performance of engineered cementitious composite (ECC) concrete beams reinforced with innovative hybrid bars. Hybrid bars combine the advantages of both FRP and steel bars in enhancing the ultimate strength, ductility, and corrosion resistance compared with pure FRP or steel bars. Twelve half-scale ECC-concrete beams were tested to study the flexure behaviour under four-points loading test using polyvinyl alcohol (PVA) ECC fibers. Polyvinyl alcohol (PVA) fibers were used in the ECC mix for this purpose. The experimental variables are the hybrid reinforcement ratios (0.85%, 1.26%, and 1.7%), PVA fiber ratio (0.0%, 0.75%, and 1.5%) and hybrid schemes (hybrid and GFRP bars). The test results showed significant enhancement in the capacity of ECC concrete beams reinforced with hybrid bars or hybrid schemes. The achieved enhancements are 12% and 27% for PVA ratio of 0.75% and 1.5% respectively. In the presence of PVA fibers, the ultimate strain of the bars is higher than that registered in the absence of PVA fibers. Non-linear finite element analysis (NLFEA) was carried out to validate the experimental results. The NLFEA is adequately simulating the experimental results. Nominal flexural strength and flexural rigidity were assessed with the experimental test results and validated with 77 available ECC-concrete beams from the literature. The validation proved that the assessments of the nominal flexural strength and flexural rigidity are performed well in the prediction. Finally, a comprehensive sensitivity study is conducted to illustrate the effect of PVA-ECC on the flexural rigidity of the beams. The experimental evidence presented in the current study demonstrates the feasibility and plausible future of the novel hybrid bars and PVA fibers especially for marine and waterfront concrete structures.

Role of Sugarcane Bagasse Ash in Developing Sustainable Engineered Cementitious Composites

Sugarcane bagasse is an agricultural waste that can be transformed by incineration into a cement replacement material for various cementing purposes. This study investigated the role of finely ground bagasse ash (GBA) in producing engineered cementitious composites (ECCs) with the addition of polyvinyl alcohol (PVA) fibers. The main focus of this study was to develop a green ECC with higher strength capabilities (compressive, tensile and flexural) and greater tensile ductility. To develop this composite, GBA was added into ECC mixes at different proportions, i.e., 10, 20 and 30%. The proportions of PVA fibers and the water-to-binder ratio were kept constant. The results revealed that the ECC mix containing 10% GBA exhibited higher compressive strength compared to that of a control and the other ECC mixes. Furthermore, the tensile and flexural strengths of the ECCs exhibited patterns almost similar to that of compressive strength. Moreover, the deflection in the control mix was higher compared to that of the GBA-ECC mixes at an initial curing age. The ECC mix containing 10% GBA exhibited better ductile behavior among all the ECC mixes used in this study.

Feasibility of using ultrahigh-volume limestone-calcined clay blend to develop sustainable medium-strength Engineered Cementitious Composites (ECC)

Engineered Cementitious Composites (ECC) showing multiple-cracking and strain-hardening under tension are appealing for the construction industry, but the high cement content in conventional ECC leads to high environmental impacts. Recently, the limestone and calcined clay (LCC) blend has been proposed as a promising alternative of Supplementary Cementing Materials (SCM) to address the inadequacy of common SCM such as fly ash and blast furnace slag, which have been widely-used in ECC. This paper reports a feasibility study for the first time on using ultrahigh-volume LCC blend (HVLCC, 70% and 80% by weight of binder) to produce sustainable medium-strength ECC. Three water/binder ratios (0.30, 0.35 and 0.40) and two sand/binder ratios (0.2 and 0.4) were explored. HVLCC-ECC can achieve a tensile strain capacity of 0.57–1.58%, tensile strength of 3.24–5.19 MPa and compressive strength of 33–65 MPa at 28 days. HVLCC-ECC also have sufficient early strength at 3 days (22-38 MPa), and similar fresh properties and bulk densities under surface-dry condition (1900-2100 kg/m3), as compared to conventional ECC. Additionally, HVLCC-ECC show about 1/6 higher embodied energy and about 1/6 lower embodied carbon than a typical ECC mix with 55% fly ash in the binder, and ECC with fly ash perform much better than ECC with LCC blend in terms of embodied energy and embodied carbon per unit strength or strain capacity. Nevertheless, this new version of HVLCC-ECC with adequate mechanical performance are still attractive from the perspective of shortage of fly ash in the future due to the reduced consumption of coal.

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.

ECC Design Based on Uniform Design Test Method and Alternating Conditional Expectation

Engineered cementitious composites (ECC) have higher ultimate tensile strains than normal concrete. The mechanical properties of ECC strongly depend on raw materials and the mix proportions. The uniform design test method and alternating conditional expectation, which is a nonparametric regression analysis method, were used to design the ECC mix proportion. According to the regression analysis, the optimized W/B, S/B, and F/B ranges could be obtained as 0.35–0.42, 0.25–0.3, and 0.02, respectively. The tested proportions for validation were randomly adopted within the range of W/B, S/B, and F/B. The uniaxial compression, tension, and four-point bending tests were conducted to verify the material behaviour of the designed ECC. Results showed that all the specimens had large ultimate tensile strains and high fracture energy capacities, and strain hardening was also observed. The fibers were found to be uniformly distributed in the specimens by using a scanning electron microscope. This paper may provide theoretical and practical guidance for the ECC and other cement-based material mix proportion design.