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The present study introduces a novel approach utilizing machine learning techniques to predict the crucial mechanical properties of engineered cementitious composites (ECCs), spanning from typical to exceptionally high strength levels. These properties, including compressive strength, flexural strength, tensile strength, and tensile strain capacity, can not only be predicted but also precisely estimated. The investigation encompassed a meticulous compilation and examination of 1532 datasets sourced from pertinent research. Four machine learning algorithms, linear regression (LR), K nearest neighbors (KNN), random forest (RF), and extreme gradient boosting (XGB), were used to establish the prediction model of ECC mechanical properties and determine the optimal model. The optimal model was utilized to employ SHapley Additive exPlanations (SHAP) for scrutinizing feature importance and conducting an in-depth parametric analysis. Subsequently, a comprehensive control strategy was devised for ECC mechanical properties. This strategy can provide actionable guidance for ECC design, equipping engineers and professionals in civil engineering and material science to make informed decisions throughout their design endeavors. The results show that the RF model demonstrated the highest prediction accuracy for compressive strength and flexural strength, with R2 values of 0.92 and 0.91 on the test set. The XGB model outperformed in predicting tensile strength and tensile strain capacity, with R2 values of 0.87 and 0.80 on the test set, respectively. The prediction of tensile strain capacity was the least accurate. Meanwhile, the MAE of the tensile strain capacity was a mere 0.84%, smaller than the variability (1.77%) of the test results in previous research. Compressive strength and tensile strength demonstrated high sensitivity to variations in both water-cement ratio (W) and water reducer (WR). In contrast, flexural strength exhibited high sensitivity solely to changes in W. Conversely, the sensitivity of tensile strain capacity to input features was moderate and consistent. The mechanical attributes of ECC emerged from the combined effects of multiple positive and negative features. Notably, WR exerted the most significant influence on compressive strength among all features, whereas polyethylene (PE) fiber emerged as the primary driver affecting flexural strength, tensile strength, and tensile strain capacity. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites are a type of advanced building materials, which have excellent ductility and can significantly enhance structural resistance. However, the expensive material cost of ECC limits its engineering applications. This study investigated the potential of replacing commonly used silica (river) sand and imported PVA fibers with the local desert sand and PVA fibers, aiming at reducing the preparation cost of ECC and improving its economic benefits and sustainability. The mixture proportion was first optimized to obtain favorable strength and ductile enhancement, using a combination of single-factor test and theoretical calculation which mentioned the slurry coating thickness of fibers and desert sand. The potential of desert sand in preparing ECC was experimentally evaluated by comparing the uniaxial tension (compression) properties and microstructures of desert sand-based ECC (DS-ECC) and those of ordinary ECC. The results indicate that optimized DS-ECC can achieve satisfactory performance even when 100% fine aggregates are replaced by desert sand. It has comparable uniaxial tensile (compression) strengths to ordinary ECC but a significantly improved tensile ductility, with the ultimate tensile strain of about 5–8% and 3% at 7d and 28d curing ages, respectively. Meanwhile, the utilization of desert sand and local PVA fibers alone in ECC can substantially deliver a reduction of about 20–30% in material cost and an improvement in environmental impact. [ABSTRACT FROM AUTHOR]

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This research examined the development of modified engineered cementitious composites (MECC) using manufactured sand (M-sand) and a high content of raw agricultural by-products, such as bagasse ash (BA) and rice husk ash (RHA), instead of conventional silica sand and fly ash. Fourteen different types of MECC mixtures were developed using raw BA and RHA blended with M-sand to reduce the cost of MECC. The fresh and hardened properties of all mixtures were examined using various types of testing methods. In addition, microstructure analysis were conducted for both the control and optimal mixtures to identify the bonding of fibres in cementitious composites. The correlation between conventional and MECC was also evaluated based on the hardened properties and cost analysis. The results revealed that workability steadily dwindled with increasing percentages of BA and RHA, from 10 to 55. Optimal mechanical properties were attained with the incorporation of BA and RHA at 10% cement replacement. In contrast, 30% BA and 40% RHA exhibited maximum impact strength compared to the respective control mixes. Similarly, ECC with 20% BA and RHA exhibited optimal durability properties. Moreover, compared to conventional ECC, the cost of the newly developed MECC was slightly lesser due to the incorporation of agricultural by-products and M-sand. [ABSTRACT FROM AUTHOR]

The existing Reinforced Concrete (RC) School buildings are often characterized by low-rise, very long beams, and relatively large-valued uniformly distributed loads. Beams present a large amount of longitudinal reinforcement so that they exert huge shear stresses, on the joint panels into which they frame, during a seismic event. For this reason, the main cause of seismic inadequacy of these buildings is often the premature shear failure of the joints. These latter can result either (a) completely devoid of reinforcing stirrups, or (b) not suitably reinforced, or (c) under-dimensioned. In some cases, due to either the results of the feasibility study or to instructions given by the Contracting Authority, the seismic rehabilitation of such buildings must be obtained by local interventions. To rehabilitate an existing RC building with under-dimensioned joints, by means of local interventions, the availability of pourable and self-compacting High-Performance Fiber Reinforced Cementitious Composites (HP-FRCC) renders the RC jacketing the ideal solution. In cases in which an aggressive environment is concomitant with the susceptibility to earthquakes, an Engineered Cementitious Composite designed ad hoc could be an even better option. The RC jacketing of the joint allows to enlarge it, thus making it work in un-cracked regime. However, when the joint panel is enlarged, the appropriate hierarchy of resistances must be restored throughout the length of the column, to guarantee the activation of the desired global dissipative mechanism. In this article a calculation strategy to follow in these cases, in compliance with the Building Regulations, is proposed and described by referring to a case-study. Finally, a discussion is provided on some aspects, which are still susceptible to improvement, to refine the intervention technique. [ABSTRACT FROM AUTHOR]

Engineered cementitious composites (ECC) have been manufactured by mixing the treated municipal solid waste incineration (MSWI) bottom ash (BA), ordinary Portland cement, fne silica sand and Polyvinyl Alcohol (PVA) fber. Characterizations including X-ray fuorescence (XRF) and laser difraction have been performed on four types of BA powders obtained by combined treatments, and the chemical compositions and particle size distribution of those BA powders are derived. The mechanical properties of BA powders in mortar as cement replacement are tested to determine their reactivity. BA powder with highest reactivity completely replaces the fy ash in ECC, and its contribution to strain hardening of composites is investigated. Results indicate that mortar mixed with BA fnes prepared by thermal treatment followed by ball milling has the best mechanical properties. After 28 days of curing, the fexural and compressive strength of this mortar reach 82% and 81% of the reference, respectively. The strength activity index meets the requirement of not less than 70% specifed in the Chinese standards. The increase of BA powder not only reduces the frst crack strength of ECC but also reduces the ultimate tensile strength of the composites. Fortunately, the strain hardening properties of ECC are improved. In addition, the highest ductile tensile properties are obtained in ECC with BA fnes to cement ratio of 2.2. This research provides a strategy in making use of vast resources BA obtained from MSWI. [ABSTRACT FROM AUTHOR]

Engineered cementitious composites (ECC) characterizes with high strain capacity, accompanied by two notable disadvantages, i.e., low elastic modulus and severe shrinkage yet. A new type of ECC featuring relatively high tensile strain capacity, high elastic modulus as well as low shrinkage was developed by using polyethylene fiber (PE) alone (P-ECC), or hybrid combining PE fiber with steel fiber (H-ECC) in this research. The effects of sand-to-binder ratio (s/b) from 0.42 to 1.02 and fiber hybridization on compressive properties, tensile properties and shrinkage characteristics of ECC were systematically investigated. Experimental results indicated that the increase of s/b ratio could benefit the compressive strength, the elastic modulus and the shrinkage performance of ECC. The elastic modulus as well as the shrinkage properties of P/H-ECC were superior than those of traditional ECC. It is noted that H-ECC with extremely high s/b ratios (i.e., 0.72–1.02) exhibiting relatively high tensile strain capacity, comparable elastic modulus with normal strength concrete and obviously lower total shrinkage than traditional ECC, is an ideal and competitive material which can be utilized in critical structural elements characterized by deformation compatibility and desirable ductility. [ABSTRACT FROM AUTHOR]

In this study, sprayable strain-hardening fiber-reinforced cementitious composites (FRCC) were applied to strengthen the concrete slabs in a concrete-face rockfill dam (CFRD) for the first time. Experimental, numerical, and analytical investigations were carried out to understand the flexural properties of FRCC-layered concrete slabs. It was found that the FRCC layer improved the flexural performance of concrete slabs significantly. The cracking and ultimate loads of a concrete slab with an 80 mm FRCC layer were 132% and 69% higher than those of the unstrengthened concrete slab, respectively. At the maximum crack width of 0.2 mm, the deflection of the 80-mm FRCC strengthened concrete slab was 144% higher than that of the unstrengthened concrete slab. In addition, a FE model and a simplified analytical method were developed for the design and analysis of FRCC-layered concrete slabs. Finally, the test result of FRCC leaching solution indicated that the quality of the water surrounding FRCC satisfied the standard for drinking water. The findings of this study indicate that the sprayable strain-hardening FRCC has a good potential for strengthening hydraulic structures such as CFRDs. [ABSTRACT FROM AUTHOR]

In this study, carbon textile reinforced concrete (CTRC) and engineered cementitious composites (ECC), together with steel fibers, were combined to fabricate two-layer concrete, called CTRC-ECC concrete. The dynamic compressive behavior of CTRC-ECC concrete was studied through the quasi-static compressive test and the impact test using a split Hopkinson pressure bar (SHPB). The effects of the thickness of CTRC, steel fibers, and impact face on the dynamic compressive strength, dynamic increase factor (DIF), strain at peak, and impact toughness of CTRC-ECC concrete were discussed. The results showed that as the thickness of CTRC increased, the dynamic compressive strength followed an increasing trend generally; the DIF decreased; and the strain at peak and the impact toughness increased firstly and then decreased. The addition of steel fibers to CTRC could increase the dynamic compressive strength significantly when the thickness of CTRC is less than 10 mm, improve the impact toughness slightly, but reduce the DIF significantly. In terms of the strain at peak, it firstly increased and then reduced and lastly did not change too much by steel fibers. The effect of impact face on the dynamic compressive strength, DIF, and impact toughness was not significant; however, when the CTRC face was subjected to impact load, the strain at peak could be slightly higher. [ABSTRACT FROM AUTHOR]

Orthotropic steel bridge deck system usually consists of an orthotropic steel deck and an asphalt overlay. Fatigue cracks of the orthotropic steel deck and premature damage of the asphalt overlay are frequently reported for such system. Engineering cementitious composites (ECC) was therefore proposed to replace the asphalt overlay to address the aforementioned issues. The current study presents an investigation on the transversal flexural behaviour of the ECC under bending forces. Influence of the bending force direction, cover thickness, the number of longitudinal reinforcement steel bars on the flexural performance was revealed. Responses with regard to the load-deflection curve, failure mode, the ultimate capacity, the cracking behaviour, the interfacial slip between ECC and steel deck and the nominal cracking stresses were analysed. The results showed that the load-deflection response under both negative and positive bending forces exhibits elastic stage, crack-developing stage and yield stage. Compared with the reinforcement ratio, cover thickness plays a more significant role on the flexural performances. When the cover thickness decreases from 35 mm to 25 mm, the peak load increases by 21%–25%. ECC maintains its feature of being ductile, with high tensile and compressive strain capacity in the composite slab. From the design point of view, reducing the cover thickness and increasing the reinforcement ratio can improve the ultimate load and cracking stress, and reduce the internal slip, strain and crack width of the composite slab. It is expected that the current study can provide basic knowledge to the design and application of the steel-ECC composite deck system. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to determine the effect of Natural Pozzolan (NP) content on the mechanical properties and durability characteristics on Engineered Cementitious Composites (ECC) as repair material. This study focused on the evaluation of the most factors influencing compatibility between the repair material and the base concrete including mechanicals properties such as, compressive and flexural strengths, elastic modulus, capillary absorption and drying shrinkage. The experimental results showed that natural pozzolan reduces the compressive strength and the flexural strength of ECC at all ages. The elastic modulus of ECC was remarkably lower than that of normal-strength concrete. This lower Young’s modulus is desirable for repair concrete, because it prevents the stresses induced by restrained shrinkage. In addition, the incorporation of high-volume natural pozzolan decreases significantly the coefficient of capillary absorption at long term and increases the drying shrinkage. Generally, based on the results obtained in the present experimental investigation, ECC can be used effectively as an overlay material over existing parent concrete. [ABSTRACT FROM AUTHOR]

The impact of a thin layer of a ductile fiber-reinforced concrete referred to as engineered cementitious composites (ECC) on unreinforced masonry (URM) prisms and beams has been evaluated. The objective of the research was to characterize the performance and potential benefits of using ECC to retrofit URM with eventual application to masonry infill walls in non-ductile reinforced concrete frames. Compression tests of masonry prisms and flexural tests of masonry beams with different ECC retrofit schemes were conducted. The variables studied were the use of wall anchors to improve the ECC-masonry bond and alternate steel reinforcement ratios within the ECC layer in the form of welded wire fabric. The ECC retrofit was found to increase the strength and stiffness of URM prisms by 45 and 53 %, respectively compared to those of a plain specimen. When wall anchors were installed on the masonry specimens, the bond between the ECC layer and the masonry surface was improved. Four-point bending tests indicated that the strength and more importantly the ductility of an ECC retrofitted brick beam are increased significantly, especially when light reinforcement is added to the ECC layer, relative to an URM beam. Analytical models for estimating the strength and stiffness of ECC retrofitted masonry specimens are proposed and evaluated. [ABSTRACT FROM AUTHOR]

Hydroxypropyl methylcellulose (HPMC) and amphoteric polyacrylamide (ACPAM) were respectively used to prepare engineered cementitious composite (ECC) which exhibits strain-hardening behavior under uniaxial tension. The connections between cement paste structure and the performance of the composite in fresh and hardened state were investigated, aiming at achieving the desirable workability at a given solids concentration. The experimental results of viscosity and microstructure of cement pastes show that the intimate connections between flocculation groups lead to the growing increase in viscosity. The results of deformability and fiber dispersion demonstrate that fiber dispersion coefficient is a comprehensive index which can reflect the performance of deformability as well as uniformity. And the desirable fresh mixture can be achieved by optimizing the viscosity of cement paste. At last, the ductile strain-hardening performance of the ECC prepared with HPMC or ACPAM was investigated through uniaxial tensile test. [ABSTRACT FROM AUTHOR]

The capability of processing robust Engineered Cementitious Composites (ECC) materials with consistent mechanical properties is crucial for gaining acceptance of this new construction material in various structural applications. ECC's tensile strain-hardening behavior and magnitude of tensile strain capacity are closely associated with fiber dispersion uniformity, which determines the fiber bridging strength, complementary energy, critical flaw size and degree of multiple-crack saturation. This study investigates the correlation between the rheological parameters of ECC mortar before adding PVA fibers, dispersion of PVA fibers, and ECC composite tensile properties. The correlation between Marsh cone flow rate and plastic viscosity was established for ECC mortar, justifying the use of the Marsh cone as a simple rheology measurement and control method before fibers are added. An optimal range of Marsh cone flow rate was found that led to improved fiber dispersion uniformity and more consistent tensile strain capacity in the composite. When coupled with the micromechanics based ingredient-tailoring methodology, this rheological control approach serves as an effective ECC fresh property design guide for achieving robust ECC composite hardening properties. [ABSTRACT FROM AUTHOR]

The split Hopkinson pressure bar (SHPB) testing with diameter 40 mm was used to investigate the dynamic mechanical properties of engineered cementitious composites (ECCs) with different fly ash content. The basic properties including deformation, energy absorption capacity, strain-stress relationship and failure patterns were discussed. The ECCs showed strain-rate dependency and kept better plastic flow during impact process compared with reactive powder concrete (RPC) and concrete, but the critical compressive strength was lower than that of RPC and concrete. The bridging effect of PVA fiber and addition of fly ash can significantly improve the deformation and energy absorption capacities of ECCs. With the increase of fly ash content in ECCs, the static and dynamic compressive strength lowered and the dynamic increase factor enhanced. Therefore, to meet different engineering needs, the content of fly ash can be an important index to control the static and dynamic mechanical properties of ECCs. [ABSTRACT FROM AUTHOR]

Contributing nearly 5% of global anthropogenic greenhouse emissions through cement production alone, the concrete industry is a major contributor to global climate change. Automobiles and trucks that use concrete transportation infrastructure release another 30% of anthropogenic greenhouse emissions. Along with these atmospheric emissions, the construction, repair, and rehabilitation of concrete pavements rely on the production and flow of large quantities of concrete material and its constituents. To reduce environmental impact and improve the sustainability of pavement overlay systems, a class of materials called Engineered Cementitious Composites (ECC) is introduced to construct more sustainable, durable rigid pavement overlays. ECC overlays are designed to enhance sustainability in two ways. First, "greener" ECC materials incorporate high volumes of industrial waste to reduce the environmental impacts of material production. Fundamental micromechanics carefully guide this green material design to maintain pseudo-strain hardening material behavior under tension. This ductile behavior, over 500 times greater than conventional concrete, is critical to the second mechanism for sustainability enhancement. The ductility of ECC suppresses reflective cracking, a major cause of premature overlay failure, thereby increasing durability and reducing life-cycle maintenance. By incorporating industrial waste, over 70% of ECC virgin constituents have been replaced without reducing critical mechanical performance characteristics. When coupled with a possible 50% reduction in overlay thickness and extension of service life as compared to conventional concrete overlays, significant sustainability improvements have been modeled. These improvements are quantitatively measured using life cycle cost and life cycle assessment techniques. [ABSTRACT FROM AUTHOR]

Nowadays limestone powder and blast furnace slag (BFS) are widely used in concrete as blended materials in cement. The replacement of Portland cement by limestone powder and BFS can lower the cost and enhance the greenness of concrete, since the production of these two materials needs less energy and causes less CO2 emission than Portland cement. Moreover, the use of limestone powder and BFS improves the properties of fresh and hardened concrete, such as workability and durability. Engineered cementitious composites (ECC) is a class of ultra ductile fiber reinforced cementitious composites, characterized by high ductility, tight crack width control and relatively low fiber content. The limestone powder and BFS are used to produce ECC in this research. The mix proportion is designed experimentally by adjusting the amount of limestone powder and BFS, accompanied by four-point bending test and uniaxial tensile test. This study results in an ECC mix proportion with the Portland cement content as low as 15% of powder by weight. This mixture, at 28 days, exhibits a high tensile strain capacity of 3.3%, a tight crack width of 57 μm and a moderate compressive strength of 38 MPa. In order to promote a wide use of ECC, it was tried to simplify the mixing of ECC with only two matrix materials, i.e. BFS cement and limestone powder, instead of three matrix materials. By replacing Portland cement and BFS in the aforementioned ECC mixture with BFS cement, the ECC with BFS cement and limestone powder exhibits a tensile strain capacity of 3.1%, a crack width of 76 μm and a compressive strength of 40 MPa after 28 days of curing. [ABSTRACT FROM AUTHOR]