•Self-healing capability of ECC is examined depending on literature survey.•Factors governing intrinsic self-healing capability of ECC are discussed.•Assessment of self-healing by transport and ...mechanical properties are emphasized.•Results of different experimental studies are collected and summarized.
The need for viable materials in sustainable infrastructures is driving the creation of multifunctional strain-hardening cementitious composites that combine brittle cementitious matrices with fibers. Unlike conventional concrete, these materials typically show multiple microcracking behavior with strain-hardening response under tensile loading. Even with tight widths, however, crack formation is a critical problem that reduces the mechanical performance of structures and accelerates the ingress of water and aggressive substances. As part of a class of cement-based composites exhibiting strain-hardening response, engineered cementitious composites (ECCs) have a high likelihood of preventing water and harmful chemicals from penetrating by sealing existing cracks and regaining original mechanical and durability properties through self-healing. This promises to contribute to the development of a new generation of highly durable, damage-tolerant structures. ECCs are potentially excellent for intrinsic self-healing due to tight crack widths and high amounts of supplementary cementitious materials in their mixture proportions. This paper details the parameters governing self-healing efficiency and the effect of self-healing on the residual mechanical and transport properties of cementitious composites. Test methods measuring the effect of these parameters on healing efficiency are also described.
•Influence of cracking and self-healing on the gas permeability of ECC were studied.•Gas permeability, resonant frequency and crack analysis tests were conducted.•Self-healing was strongly influenced ...by the chemical compositions of the mixtures.•Application of pre-loading led to significant increases in GP and RF results.•Recovery in GP results could be increased to 96% through proper curing.
The main objective of the study presented in this paper was to investigate the influence of cracking and self-healing on the gas permeability of Engineered Cementitious Composites (ECC). To deliberately introduce microcracks, specimens were pre-loaded to different deformation levels under splitting tensile loading and exposed to different environmental conditionings for the assessment of self-healing. Gas permeability (GP) and resonant frequency (RF) tests, crack characteristics observation and microstructural analysis were conducted to analyze the effect of cracking and healing on the properties of cementitious composites. Test results indicate that the self-healing effect determined through GP and RF tests was strongly influenced by changes in the chemical compositions of the mixtures. Application of pre-loading led to significant increases in GP results, so that even microcracks of less than 50μm caused a GP coefficient fifty times higher than that of sound specimens. However, the recovery in GP results could be escalated up to 96% after only a month through proper material design and conditioning. It therefore appears that microcracking and subsequent healing is influential on the GP recovery rates of specimens, but not on RF recovery rates.
Metakaolin (MK) is a valuable admixture for concrete/cement applications that can enhance the performance of cementitious composites through high pozzolanic reactivity, much like silica fume (SF). ...While SF concrete is characterized by superior mechanical and durability performance, concrete containing MK achieves comparable properties at a lower price and with better workability. The objective of this study is to investigate the effect of cement replacement by MK on the durability of self-consolidating concrete (SCC); the effect of SF at similar levels of MK replacement has also been included for comparison. The durability performance of SCC was evaluated based on the results of drying shrinkage, freezing and thawing, salt scaling, and rapid chloride permeability tests. The results of these tests indicate that highly durable SCC mixtures can be produced using a high MK content with an optimum percentage of around 20%. The results also show that the durability of SCC, especially with high MK content, is higher than that of SCC containing SF.
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.
This paper presents the development of lightweight aggregate self-consolidating concrete (SCC) using two types of lightweight aggregates having different densities. Lightweight aggregate SCC ...properties have been evaluated in terms of flowability, segregation resistance and filling capacity of fresh concrete as per the standards of the Japanese Society of Civil Engineering (JSCE). The measurement of the mechanical properties of hardened lightweight aggregate SCC, including compressive strength, splitting tensile strength, elastic moduli and density, as well as its specific strength were also carried out. The characteristics of lightweight aggregate SCC at the fresh state showed that as the density of the lightweight coarse aggregate decreases, the flowability improves but the segregation resistance tends to decrease. The 28-days compressive strength of the lightweight SCC was found to be 32
MPa or higher. The relationship between the compressive strength and the splitting tensile strength was found to be similar to the expression presented by CEB-FIP, and the relationship between the compressive strength and the elastic moduli was found to be similar to the expression suggested by ACI 318-05 which takes into consideration the density of concrete. The density of the lightweight aggregate SCC decreased by up to 14% compared to that of the control SCC, and the specific strength decreased by up to 20%.
The use of link slab (LS) made of Engineered Cementitious Composite (ECC) in the construction of joint-free bridge deck can meet structural performance requirements and enhance durability to minimize ...life cycle costs. Studies documented in the literature to date have been limited to composite steel-concrete I-deck girder bridges despite their commonly used reinforced concrete (RC) girder counterparts in construction. This paper deals with two span full RC deck girder joint-free bridges with ECC link slab (ECC-LS) constructed and tested under static and fatigue loading up to 1,000,000 cycles at 4 Hz subjected to mean stress level of 40% of girder ultimate load, followed by post-fatigue static loading to failure. Residual load, deflection, moment, rotation, stiffness, and energy absorbing capacity of fatigued bridge specimens are compared with its virgin (non-fatigued) counterparts to assess structural performance. Experimental moment capacities are compared with those obtained from existing analytical equations. The comparative performance of joint-fee bridge with RC deck girder is compared with its composite steel-concrete I-girder counterpart to assess its feasibility of construction.
AbstractRigid concrete overlays have been used for smoothing damaged surfaces and/or restoring or improving the mechanical capacity of bridge decks for many years. However, engineered cementitious ...composites (ECCs), which demonstrate superior ductility with high strength and improved durability characteristics, are an attractive alternative to conventional overlay materials if a strong mechanical bond is formed between the overlay and the substrate material. An experimental study was performed to evaluate the bond strength between ECC overlay and an ordinary concrete substrate with smooth and rough surface textures. Microsilica concrete (MSC), generally used as an overlay material, was also prepared as a control mixture. ECC and MSC overlay mixtures were cast over the concrete substrate to determine bonding performance. Slant shear and splitting prism tests were performed with MSC and two ECC mixtures. The experimental results show that when ECC is used as an overlay material, bond strength is significantly increased compared to MSC. Under compression loading (slant shear test), the bond-strength properties of layered ECC substrate concrete cylinder specimens were greater than the strength of substrate concrete with compressive strength of around 30 MPa. However, in the case of layered MSC substrate concrete cylinder specimen, failure consistently occurred at the interface.
•This study was to evaluate the effect of corrosion on shear behavior of SCC beams.•Four levels of corrosion were established at 5%, 10%, 15%, and 20% of mass loss of the reinforcing ...bars.•Experimental results showed a high correlation between calculated mass loss and real mass loss in reinforcing bars.•It appears that the usage of NC and SCC does not significantly influence failure mode.•Different corrosion stages have a higher influence on the failure mode and structural capacity of beams.
The objective of this study was to evaluate the effect of corrosion on shear behavior of self-consolidating concrete (SCC) beams. Reinforced normal concrete (R-NC) specimens that have equal compressive strength to the SCC specimens were also used for control purposes. Twenty reinforced concrete beams with dimensions of 150mm×220mm×1400mm (10 SCC and 10 NC) were manufactured for the study. Using accelerated corrosion through the application of a constant current of one ampere, four levels of corrosion were established at 5%, 10%, 15%, and 20% of mass loss of the reinforcing bars. In order to ensure the highest probability of shear failure mode, a ratio of a/d=2.5 was set, with “a” being the distance from the concentrated load to the reaction and “d” being the distance from the center of the tensile flexural rebar to the top of the reinforced concrete beam. Experimental results showed a high correlation between calculated mass loss (according to Faraday’s law) and real mass loss in reinforcing bars due to accelerated corrosion. It appears that the usage of NC and SCC does not significantly influence failure mode, although different corrosion stages have a higher influence on the failure mode and structural capacity of beams, regardless of concrete type. Therefore, the apparent changes in failure mode are associated with increased corrosion levels.
One of the most damaging environmental conditions to concrete structure is cyclic freezing and thawing. This paper discusses the influence of the high volumes of fly ash (FA) and micro ...poly-vinyl-alcohol (PVA) fibers on the cyclic freeze–thaw resistance and microstructure of the Engineered Cementitious Composites (ECC). ECC mixtures with two different FA–cement (FA/C) ratios (1.2 and 2.2 by weight), and at constant water-cementitious materials (fly ash and cement) ratio of 0.27 are prepared. To compare the behavior of ECC with ECC matrix, all of the preceding properties are also investigated for ECC matrix mixtures of same composition without PVA fiber. For frost resistance, mixtures are exposed to the freeze and thaw cycles up to 300
cycles in accordance with ASTM C666, Procedure A. Experimental tests consist of measuring the residual mechanical properties (flexural strength, mid-span beam deflection and flexural stress – deflection curve), ultrasonic pulse velocity and mass loss. The roles of PVA fibers and FA are discussed through the analysis of microstructure and fiber–matrix interactions as function of frost exposure. The microstructural characterization by measuring pore size distributions is examined before and after exposure to frost deterioration by using mercury intrusion porosimetry (MIP). The air-void characteristics of mixtures are also studied using linear transverse method. Test results confirm that both ECC mixtures with high volumes of FA remain durable, and show a tensile strain capacity of more than 2% even after 300 freezing and thawing cycles. On the other hand, before completing 300 freezing and thawing cycles, matrix (ECC without fiber) specimens have severely deteriorated, requiring removal from the freeze–thaw machine. Therefore, results indicate that the addition of micro PVA fiber to the ECC matrix substantially improved the frost resistance. The results of freeze–thaw tests also indicated that the reduction of residual physical and mechanical properties with increasing number of freeze–thaw cycles is relatively more for ECC mixture with FA/C ratio of 2.2 than for ECC mixture with FA/C ratio of 1.2.
This research focuses on the effects of self-healing on the different transport properties of microcracked Engineered Cementitious Composites (ECC) with different maturity levels and incorporating ...three different mineral admixtures with greatly varying chemical compositions. The effect of self-healing capability on transport properties was assessed using water sorptivity and rapid chloride permeability tests (RCPT). Experimental results revealed that with the selection of proper mineral admixture type and conditioning, a 92% recovery in water sorptivity results is attainable. Moreover, a considerable amount of this recovery took place after only 7 days of water curing, significantly lowering the risk of water transport by capillary suction into cracked ECC. Like the sorptivity measurements, most of the chloride ion penetrability values could also be reduced up to a great extent after 30 days of water curing, so most of the results fell into the low penetrability level during this period, as prescribed by ASTM C1202. Although self-healing in terms of RCPT results started to be visible in the first 7 days of water curing, significant improvements needed more time in RCPTs, unlike the sorptivity results. Overall, these findings suggest that the rate of self-healing varies depending on the different transport mechanisms dominant in a given infrastructure type during its service life.
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